I have often encountered some resistance while discussing chassis restoration. In particular the aspect of "restuffing" the original paper capacitors seems to be a step too far for some people.

"I don't feel the need to do that". Well, that is OK, don't. And this one - "No one ever looks under the chassis". To that I say it is both untrue and somewhat ridiculous, since there is much more involved. I find this of particular interest in today's environment of "MAGA" which implies that we need higher quality and workmanship - like the "good old days".

This attitude is often associated with shoddy workmanship. If the builder of your home uses less concrete in the foundation because "no one will ever see it", Let's hope the building inspector catches him. This is why antique radio buyers WANT to see the underside of the restored chassis, unless the radio is very cheap.

But don't focus too much on restuffing caps, there is a lot more to "restoration" than just the caps. Let's look at a radio I am working on right now. It is an AK (Atwater Kent) 944 from 1934/35.

This radio was working when I acquired it in a large lot last month. The cabinet had been "antiqued". The heavy paint covered up missing and split veneers and holes filled with putty - it was a total loss. So, this fellow did some less-than-perfect cabinet work. Good thing I had another cabinet!

Lets move on to the chassis. It is clear that he did have some electronic experience. He either needed to replace the original volume control or had problems with audio level not uncommon to this set. So he installed a ganged pot that also controlled bias to the audio output tube. IMO not the correct thing to do but still proving this was not his first radio.

Above: A finished AK 447 chassis showing all of the aspects of restoration including but not limited to caps, resistors, wire and MOSTLY, proper soldering technique.



Can I tell you a short story? Well - - Around 1992 the "cellular revolution" was in full bloom. I was a tech working for GTE (later US West, later, Airtouch, later Vodafone, later - - you get the idea). Cell phones were not cheap, especially if you had to replace one without the "bundled" contract. They were so expensive that my employer(s) feared the loss of customers that would disconnect rather than buy a new phone. It became my job to insure that this did not happen - but there was a problem. The compact design (surface mounted devices) while not new, was going to new heights with the new compact handsets. The manufactures quickly found that phones exposed to existing repair techniques were being destroyed.

The result was that almost all warranty repairs (3 year warranty) were required to be sent back to the factory. The real problem for my employer was the need to keep hundreds, maybe thousands of loaner phones since the repair process could take weeks or longer. I needed to resolve this issue.

Contacting the individual manufactures was mostly like banging your head on the wall. I approached the FTR for OKI, a nice guy that really knew what he was doing. He told me what I had suspected. It all came down to field technicians NOT KNOWING HOW TO SOLDER. OKI set up a training course for about 5 people. I found out that I did not know everything. I also found out that I did not have the proper tools. OH - ALSO there was a test.

To make a long story shorter, my employer invested thousands of $$ in all of the proper stuff - 5 element de-soldering stations with suction, static safe workstations, and a lot of parts. We became one of the first authorized field repair centers and I got a plaque for the wall. Within a few months the other manufactures fell inline. One of my most satisfying moments was when my former boss, the owner of a MSS had to bring his phone to me for repair - he was the guy that said "There is no future in consumer electronics".  Also - he is out of business now.

Above: AK 944

Back to the AK 944 chassis. Above is the top side. Looks ok, if you don't look too hard. In the lower rt. is the new volume control. Since it needed more depth than the original it had been spaced out by a block of wood - yeah it caused the control to impact the cabinet but it worked - sort of.

Let's take a look at that plastic insulated wire. Do you think it is rated for 600V? Maybe it is rated for 50V or not at all. The one thing for sure is that it is a mess (and the wrong color) (And if you new guys don't think this is important, tell me where the "black" wire specified on the schematic is supposed to go.) Yeah he only had 3 or 4 colors and was not too particular as to which he used. Can you see the solder joints?

Above; As found.

The thing I find most striking is the congestion and clutter caused by this repair technique. Let me say at this point that what you see here is above average work.

So what else can we see? Novel - the mounting of a "new" filter can - which is more than 30 years old. I'll bet it was "NOS" when he chose to use it. DO NOT use old filter caps. They generally do not age well. Anyway he pushed it up through the bottom. I think this is the first time I have seen this and while certainly creative it is not "restoration".

Glob and blob solder technique. The real trick is to get the joint HOT - FAST. Get a nice shiny joint without overheating the other components. My iron is at 800 deg.F. before I start, pig tails are cut or straitened - yeah, solder is weak. You can pull the wire out of a solder joint which is why wires/leads need to be wrapped around connections. If you have to screw with the wire/components as you make the joint you are going to burn stuff up.

Melted insulation on "new" wire. Probably going to work but it sure looks bad. Taken to an extreme, it will result in shorts. This plastic insulator melts easily. It leaves ugly burnt marks even at good joints. I have found that the new EPDM insulated wire not only looks right but the insulation is nearly impossible to scorch let alone melt.

Some of the old rubber insulated wire was just too tough to get to or replacement was deemed unnecessary.  Give that blue lead on the resistor a few more years, it will be a bare wire. HOPE it does not short. When you are doing a rewire job like this, replace all of the original wire.

Extra connectors, while convenient they detract from a proper restoration. If you NEED an MP3 port, add the jack in such a way that it can be removed. Future owners will thank you.

Modern parts - detract from the "restored appearance of the chassis. Capacitors can be restuffed, if not, save the old ones for a future owner. I still need to locate the original AK caps for this unit. This is often the biggest challenge I have in doing a restoration. I also rewind or otherwise repair transformers and coils, and cast new resistors so they look like the originals.

Above: Showing the lands/connections on an AK power transformer. ALL 1930s AK power transformers need to have the leads replaced. The original rubber insulated leads will short and cause an expensive failure. DO NOT trust the original wire.

Other AK coils are no different from the power transformers. Above is the IF transformer. At least the original tech chose to replace the wire. Unfortunately he chose to cut/splice and then wrap his connections in vinyl tape. I would have given him more slack if he had at least used heat shrink. I will again point out the wire and single color - not a restoration. You know why vinyl tape is not up to code for most electrical work? If you have to use tape, learn how to use the old friction tape - It can last for decades - or better yet do not use tape OR splices. These transformers also have lands (experience is worth something). See below.

Above: Wire/connections properly installed on the IF transformer. (no tape)

Below: A comparison of the chassis before and after. I still have to locate the original paper caps and I will restuff them, but if you choose not to, this is how your chassis should look. Note that one of his new caps had failed and one was the wrong value. Those two are yellow - for the moment.

See the new resistors? These, small AK resistors are too small for my ceramic tubes. On larger values I reuse the original lead ends. With these the whole resistor is recast and painted. Maybe one day I will start making new metal ends. (Construction is end - tube - end with a new resistor in the tube. All new resistors are at least twice the original rating but more often 4 to 12 times the ratings. For example a 1/4 watt resistor actually has a 2 watt resistor inside.

OK, you don't have to tell me that this is over the top. I have also heard from "professionals" (NEVER trust your radio to someone who is not licensed AND bonded). Several have stated that they would "tell a customer where to go" if he asks for this kind of work. Well, I can save them the effort. If your "tech" does not want to restore a radio to your specifications - I'll tell you where to go -  - Someplace else.

I have also heard people say "People want unrestored radios and pay more for them". Yes, I want unrestored radios. There is a lot of extra work involved with fixing a radio like this one. And, a more correct statement is that people don't want improperly restored radios - true that some people don't want to pay for the additional time it takes. BUT, even if a tech does not restuff caps or cast resistors the result should still be like the first picture above, not like the second. Many techs will find, as I did,  that properly restored radios sell for a premium. If you are purchasing any radio ask to see the underside of the chassis. Restorers might already have a picture. If it is too "inconvenient" for the seller, assume the worst, don't pay much.

Some people say this takes too long. I can assure you that the first one or two WILL take too long. Is it better to have three radios restored poorly or one good one? I am not going to decide for you. I think that the real annoyance comes from owners that have paid for more and they got less or collectors that have a bunch of "repaired" but not restored radios. Sorry, I know how it feels. I have reworked many of the radios I repaired 20 years ago. Yes my skills have improved and I have found sources for better and or original (looking) parts. I have refinished one cabinet 3 times ;-)


So make your next radio the best it can be. And if you are new to the hobby - well, now you know.

So, while you might not look under a chassis, I am always going to do so.

Don't forget to push "like"

The box said "AL's radio". Inside was a 3-tube Acme radio with other accessories from the early 1920's. It had been preserved so well. It must have been important to Al. Now, nearly 100 years after it was made, his nephew was allowing me to take responsibility for it's future. I will do my best.

This receiver was manufactured by Acme Apparatus Co., Cambridge MA.

As-found above

This 3 tube receiver is comprised of a UV200 detector and two stages of audio amplification. The audio stages incorporate 4 ohm rheostats controlling the filaments. These low resistance rheostats point to the original use of 1 amp UV 201s in the audio stages that would be consistent with a radio made in 1921 - early 1922. So all three tubes would have been the early brass-based/tipped 1 amp versions.

It is really tough to tell, but the original finish is either so good or possibly has been neatly top-coated at some time. In any case. the very slight cracking of the original shellac is visible if you look VERY closely.

Not only is there a storage space for B batteries, but also an internal horn speaker.

In the picture above you can see the splices that were made when the right  Acme interstage transformer was replaced with a slightly later model. The secondary on this trans. was found to be open and was the only repair that needed to be made to make the radio work again.

While there would be some historical perspective maintained by leaving the spliced buss wires, I just could not do that. So the completed repair is pictured below.

There appear to be other post-production modifications done to this radio besides the audio trans. repair. Most apparent is the piece of plywood added to the front of the battery storage area. This modification appears to be nearly as old as the radio. The construction of the plywood is period correct and it was stained to match the finish. This mod incorporated a change to the method of B battery attachment. This change made changing batteries much easier. It also allows for the use of both B+ and detector (22.5V) connections.

There is some speculation that a variable cap prior to the detector was replaced with a variometer. While this change might have reduced selectivity it probably improved antenna performance. In 1922 the ability to tune to the antenna is more significant than selectivity since all radio stations were on only ONE or two frequencies. The history of frequency assignment is discussed in the article referenced below.

With or without the variometer there is no signal gain prior to the UV 200 detector. So the "range" of this receiver is very limited. The UV 200 was a good choice at the time but the radio has insufficient control to really take advantage of it. The filament control is very rough and, in the best case, some method of of controlling the detector B+ would have been necessary.

It is possible that all of the repairs and modifications to this radio were made at the same time. While all of the work appears to be professionally done it also appears to be well planned and the person performing the repair must have been experienced with these modifications.

In my years as a radio tech I participated in several large manufacture's sponsored recalls with required modifications. After a few dozen repairs a tech would get very good at it. In my opinion, repairs to this unit might have been a part of a rebuild/reissue effort.

 I believe that all of the modifications were improvements. Looking at the front panel behind the tuning knob, the panel is neatly and accurately drilled for both a tuning cap (3 holes) and for the variometer (2 holes). All of the holes arel countersunk and clean. This is almost never the case in field modifications.

Consider the possibility that this radio was a warranty repair/return. While very few of these exist there are notes online that seem to indicate that another unit had many similar modifications. A couple of the  early UV type tubes have Pacific States Electric tags. This company was a reseller of considerable size. Is it possible that they acquired returned and unsold units and modified them?

Below is an explanation for the relatively unselective design of the Acmefone.  This is an excerpt from a remarkably complete history of broadcasting compiled by my friend Ron Kramer.

The complete document was part of an effort to build The Western States Museum of Broadcasting, a project that is on hold, for the moment. It is available as an archived document here:

https://web.archive.org/web/20150404142651/http://www.wsmb.org/Page.asp?NavID=19

If you get a chance , I would recommend reading the entire history. While much of it is specific to  S. Oregon, I am sure that the story was replicated in many large and small communities in the early 1920's

Thanks again to Ron for making this piece of radio history available to us.

Below are video demonstrations of the Acmefone in operation. There is a considerable improvement in audio using the RCA cone speaker over the onboard horn. Also, the horn driver might have been replace along with the other repairs.

The Acmefone is now available for viewing by appointment at Russ' Old Radio shop/museum.

I've been promising to post pictures from last summer's "radio pile".  Since I have already moved on to this winter's radio pile, I suppose that I should get this done.

This was a collection that was donated. It was comprised of complete radios, projects and parts chassis. I was able to preserve and restore many of the table radios including a collection of Zenith TOs not pictured here, The parts chassis were mostly scavenged for usable parts to take up less space and make accessing the spare parts easier. Some of the AA5 and other 1940s radios were sold to the public as those are outside of the scope of the collection/display. Many of the console project radios were donated to Skip, a friend, and guy with more storage space. Very little was thrown away and I consider that a success.

The radios pictured below were electrically restored by finding and replacing most of the original parts, most significantly finding and restuffing the original capacitors that had been lost. Most of the cabinets needed to be refinished.

Other radios from this collection have been discussed in greater detail in earlier posts, below.

I want to again thank contributors in helping me make these radios available to view and study by me and other radio enthusiasts.

The Motorola Stereo (3 channel) was working and the cabinet was in exceptional condition. The audio amp uses six 6V6gts in push pull configuration with the 3rd channel driving a bass speaker in the center. VERY nice. It is now at home in the office.

In the previous post the substitute UV 199 tubes are demonstrated in an early 1920s TRF radio. Now I wanted to test the UX 199/UX 120 versions along with another application for the UX 201A version.

I realized that there aren't many - any, small radios using the later UX tube versions in the museum display. There are a couple in storage, not easy to get to. There is the Thompson Minuet, I really did not want to pull it off of the shelf and risk damaging the speaker cone that Buford Chidester made for it. And then there is this really big  Remler super. Well at least the top cover was already removed for display.

The Remler is a cool radio!

I had purchased it about 5 years ago along with about a dozen other radios at an auction near Portland. It always seems that radios come in bunches and I am always in a hurry to clean them up. I do test them, but, generally move on to the next one after as quickly as possible.

Now I had a little time to explore and the first thing I needed to do was verify that the unit was functioning normally. It Wasn't. The second RF section in the TRF wasn't contributing at all.

It did not take long to find the problem which was a relief since there are a lot of moving parts and the potential for broken wires, but that was not it,

The second section of the tuning cap was shorted. This was not from broken parts but because of a wiring issue. The 3 sections of the ganged cap are isolated from each other until that little wire, seen near the bottom of the picture above is installed. On most tuning cap assemblies the moving plates (rotor) are all grounded to the shaft that moves them leaving the stationary plates (stator) to be connected in the grid circuit. On this assembly Remler had wanted to stagger the grounded plates - in other words the moving plates (rotors) in the center section were grounded. This must have confused somebody WHO grounded the stator as well as the rotor. I could tell from the obviously factory connections on the trimmer what the design configuration was.

The fix resulted in better gain from the TRF section.

I suppose that at This point I should explain that unlike any other early super that I have seen, This radio will operate as a superheterodyne OR as a TRF. And that is one of the reasons that I think it is so cool. With a "normal" super from this time you would tune and tune listening for a squeal and then tweak the IF and oscillator until you had a station. OR you would just have some noise - start over. On this radio you can turn up the TRF filament rheostat and get the same functionality as a 5 tube TRF, which is what it is in that setting. When a station is found turn down the TRF (you don't need that much input to the IF section) and adjust the super for the best audio. It really is much easier.

If you want to understand the other cool functions, like the IF that uses the sum of the freq. and local osc. there are a few good sites. Start at this one:

http://www.duanesradios.info/html/infradyne_superheterodyne.html

Now on to the tube substitution.

Below is a demonstration of the Infradyne:

Below, the 01A (201A) substitute is used in the 1st audio socket.

In the video below the 01A sub is used in the 2nd detector position with the superheterodyne section running.

During the testing process I decided to inspect the IF assembly. Below is the IF, removed and flipped over. IMO these non-potted IF transformers are so much easier to deal with than other manufactures units.

I decided to just go-for-it and replace all 3 of the UX 199s in the IF section. I believed that this was probably not going to work - but it did.  The higher gain of the substitute tubes along with other differences required retuning the IF.

Using the tree tubes there is a savings of 1/3A in the filament supply.

As one last note, I never did show or sub the UX 199 used as the oscillator since it is stuffed in behind the meter so close that it is almost impossible to get out.

I used a 3S4 just to see if it would work, it does, but the 3V4 is probably better. In the case of the 3S4 the jumper between the plate and screen could be replaced by a resistor to reduce the screen voltage which is not required in the 3V4.

Well, this concludes this project, at least for now. I have another chrome plated monster to work on.

Russ

P.S. Don't miss Part I below.

OR is there - -

I just looked up 201/01A postings on E-Pay. It looks like prices are up since the low around 4 years ago. Then it was not uncommon to be able to buy these for $10 - $15. Looks like it is $20 - $25 now. One thing you can be sure of - they aren't making new ones.

There is plenty of history on the 201 online so some research should be done, if you are interested.

I have more than enough UX201s to last a long time, especially considering that the plastic base, long pin tube was really only original equipment for about a year with the previous versions running back to about 1920. And since I try to put the original brand/type of tube in my restorations - well, that is why I have plenty.

But, many people only care about the radio working - and being cheap (me too).

I have thought about this for a while and it is a sure thing that I am not the first. Here is how it goes - build a replacement for the UX201/01A for less than $2.50.

You are gonna' need a 4 pin base like off of an 80. Depending on your radio, this base may or may not need to have the side pin for the Bayonet/UV base - depends on how old your radio is. Then, a standard 7-pin miniature socket. These should both be available from your junk drawer.

Then look in your tube stash for a 6C4. I picked this tube for it's characteristics - basically it is 1/2 of a 12AU7.  It is called a power triode by RCA. If you don't have one, E-Pay has some for about $1, some NOS. I just bought 15, about half of them NOS for an average of $1.10 - Sorry, there will be more.

Then 4 wires and a jumper will connect the 2 sockets/plugs. Connect the 7 pin socket, pins 3 and 4 to the big pins, pin 6 goes to the small pin on the right (Pins up, big pins closest to you) and the plate to the remaining small pin. Then place a jumper between pin 3 (fil) and pin 7 on the 7 pin socket. This is the cathode connection.

To test as a 201 use the same settings as an 01A but you will need to lower the bias from about 48 to near 0.

In testing this tube works great as an audio amp including a 112 . I tested it in my AK 20 in all positions with setting as they were for the 201s and it worked great as a detector and audio amp improving tone and level some and about the same as the 201 in the RF amp sockets.

BUT, BUT it is a 6V tube. Yeah, it doesn't matter. It takes about 10 seconds to warm up. BUT, BUT, BUT the cathode will be damaged - well if it goes to "sleep", just run it at 6V in your tube tester for a while. In reality these tubes were often run at low filament voltages to keep noise down in audio circuits and as a way to get bias for finals - look up some of the Fisher amps using the 12AU7 and 12AX7. It will be fine.

Also it only draws .15A of filament current. This will make your power supply/battery happy.

So a UX 201/01A sub is cool but what makes me nervous is testing with UV-199s and other more expensive/temperamental tubes.

I say temperamental since it seams that a UV or UX-199 can go to sleep just setting in it's box. Sure they can be rejuvenated, at the risk of destroying them. During the restoration process it sure would be nice to have a sub that doesn't cost $50 and up (metal base UV), then put in the correct tubes for display.

Again, looking in the inventory under cheap and plentiful I find the 3V4 miniature 7 pin tube. I have 12 of them. This tube is a pentode but don't let that bother you. The filament is a center tapped common cathode with the tap already jumpered to the suppressor grid. So one more jumper between the plate and screen and you have a triode.

https://www.radiomuseum.org/tubes/tube_3v4.html

The filament is 2.8V but running it at 3V should be no problem. The current draw is .05A. This is just perfect to replace both the UV and UX 199. COST?? - About $5 on Pay-Bay.

Go back to your parts box - assuming it is not still dumped out on the floor - and find another 7-pin mini base. Now, the UX-199 base is a little harder to find than the one for a UX-201. It has the same pin spacing and sizes but is over-all smaller in diameter. Good/bad news is that there are a lot of bad ones around. The UV-199 is harder to come by, even bad ones. Your are going to have to search for "display tubes" which should be priced at $1 or $2.

OK! this is as good a place as any to post:
THE PIN OUT ON A UV199 IS NOT THE SAME AS A UX199!!!!
Anybody trying to test one without knowing this will be fine until they hook up a UV199 and push the "TEST" button - and - BOOM goes the filament, since you just put plate voltage on it.

Examine the pin-out, courtesy of RM:

https://www.radiomuseum.org/tubes/tube_3v4.html

On your tube tester, use an ADAPTOR for the UV based tube. Both should give you about 1500 GM on the settings for a 199 (or a 99 on most Hickok tube testers).

OK, OK, just one more - for now.

How about the UX-120. This is the "power" triode output on many radios that use the 199s. The adaptor above is going to work in that socket but the B+ needs to be kept to 90V. How about using a 3S4 instead? It has about the same configuration s the 3V4 but a different pin-out.

I need to do more testing on the UX199 and UX120 subs. I will post further as results become available

If you find these posts useful, don't forget to check the "like" below. Thanks

Russ

I stated somewhere, probably more than once, that my interests include early radios up to 1942 and later Hi-Fi from around 1955 to 1979.

Why, you may ask, do I exclude the decade between 1945 and 1955? Cabinets, those rectangular, featureless cubes with doors that degraded further with the "blond", yellow and whitewashed finishes that continued into the 60s.

The problem, for me, is two fold.  First, these designs tend to hog floor space. Second, unless you design a room around them, these consoles don't fit well with most décor. Or even more simply put, they are just not to my taste. I know that my feelings are not universal, but demand and prices over the years do indicate considerable sympathy. I will have to concede that after considerable resistance, a 3 channel Motorola has been added to the display - and I kind of' like it.

 Unfortunately there were some great radios hidden inside of those cabinets. Scott and Meissner were just two of the high end manufacturers that followed this trend. They had to. It was the style of the time.

Fisher consoles are often stripped of their tuners to be installed in cabinets like those that became popular in the 60s and 70s. I suppose that this is preferable to losing the whole console to the land fill, but, one day (maybe today) the original cabinet will be missed.

So when recently I was given a number of these late 40s, upper-end radios, I simply stashed them in the parts room and moved on to the good stuff.  I suppose that fate and my desire to preserve history collided when it became necessary to clear out the parts room - or put a warning sign on the door - Enter at Your Own Risk!

Among these radios was the Scott 510 discussed below and a Scott 800 that I have not addressed yet. But the ones that interested me most were the Meissners. There was quite a collection - none were complete and none had a cabinet.

First there was the 2961 amp - REAL radio candy from 1947! I just could not ignore this PS/amp with push-pull parallel 6L6GA output tubes. Turns out the 6L6s are wired for triode operation which reduces the power output considerably (as compared to pentode operation). This amp/dual power supply was the heart of a 2961 tube radio - I wish that I had the rest of it.

Since I had neither the original 2961 receiver nor the amps for the 9-1093-7 and 9-1093, I built an adaptor to use them in combination as well as with a 9-1091C receiver (later).

At this point I will confess that the original configuration of the 9-1093 had only (ONLY!) 24 tubes, but what the heck. Here is a video. The original coaxial speaker and OP transformer are also missing so I had to adapt -

Meissner 9-1093-7 and 2961   (26 tubes)

The 1093-7 chassis was in the best shape of all of them with the black finish and red lettered labels remarkably intact. Yet it also needed the most work.

Along with the standard restuffing of paper and electrolytic capacitors, this unit also had about half of the carbon resistors way out of tolerance. I was able to replace all of the resistors with NOS carbon comp resistor from my parts inventory. This kept the bottom side of the chassis looking original as well as the top side.

During the parts replacement all eyelets are cleaned and the original mechanical contact is restored prior to soldering. This keep the eyelets and contact strips from "bulking up" with old solder and the old component wire ends also maintaining the original look and reducing the chance of intermittent contacts.

You might note the -7 on this model number. This one is the only reference to that suffix that I have found. The other version is just 9-1093. I have one of each and there are at least 3 very significant differences.

The -7 version has an on-board preamp tube for phono mounted at the end of the FM circuit and inside of the area that shields the last IF, 2 limiters and the discriminator. The other version has a hole/cover in the chassis but uses a separate pre-amp module with 6V and B+ coming from the main chassis. Interesting that the pre-amp must be plugged in in both cases to an RCA input connector.

The -7 version also has the nice black paint and the controls are mounted directly to the front of the chassis rather than being spaced back several inches in the other version.

Meissner 9-1091C

This is another AM FM (mono) chassis from about the same period. It has somewhat more versatility as compared to the 9-1093 since it has it's own power supply and push-pull 6J5s capable of driving almost any amplifier. But, it still does require a separate amplifier chassis. This radio has 17 tubes including a 6U5 eye tube to display signal strength. Like the 9-1093, AM and FM reception and audio quality are very good.

This 2961 amp uses push-pull-parallel 6L6GA wired as Triodes. It has 2 rectifiers. The 5Y3G supplies B+ for the tuner chassis and a 5V4G provides B+ for this chassis.  There is a separate filament transformer.

One of the features of this amp that is notable is the socketed filter capacitors, one for each of the B+ supplies. These caps use a 4 pin socket like the one used for an 80 or 2A3 tube. They are secured by a clamp. This sure would have made servicing the filters easier. They could have been changed out every couple of years to avoid failures.

This collection of Meissner radios also includes a Signal-Shifter EX ( low power CW transmitter ) and a much smaller kit radio. I will post any updates on those as I get to them.

It seems that many radios were sold as kits or replacement chassis for a cabinet that a customer already owned. This is consistent with the company's other offerings of  quality OEM and replacement parts. Some were sold under the name Maguire. You might want to do more research under the name Thordarson-Meissner / Mt. Carmel, Illinois. Thordarson is still in business. (Thanks Ron)

To conclude, this series of radios, especially the large chassis with FM, were very high quality only lacking the chrome to be compared with the very high end radios of the time. If you happen upon one of these radios and have never heard of, or seen one, you are not alone. If the price is right, you might want to add it to your collection.

Nipper-

Time to clean out the parts room. And, what to do with the Victor Micro-synchronous receiver chassis? It was very rough and over the 5 or 6 years it had been there, not very useful. I guess that I had just kept it for the top cover. I had always thought that it would have been nice if the heavy, stamped covers were more visible inside of the RE-XX cabinets,

Well, the chassis is gone but Nipper has been polished and mounted  (that sounds wrong ). I'll set him on top of the "Talking Machine" display.

Probably the best way to add quality programing to your old radio collection is with a low-powered, local transmitter broadcasting personally selected content.

Such devices have become inexpensive and, to some extent, reliable. Issues with these transmitters are usually associated with noise, interference and modulation levels/quality. There are at least two instances where using a Part 95 transmitter is not the best solution.  First, those people with only one or two radios might not want the additional expense and the associated hardware for their small collection/display. More significant for us "serious" collectors is the inherent mediocre audio quality and it's reproduction on a very high end radio like a Scott, McMurdo Silver or any of the high tube count radios of the 1930's to the 1970's. It is difficult to get the performance that these radios are capable of without quality input.

Many of these high-end radios came with phonographs or at least a phonograph input that can be used with modern source equipment. The most significant drawback associated with using your MP3 device as an input is the relatively small signal voltage that they generate for audio output.

The other significant compatibility issue is that even the mightiest, 25 tube (or more) hi-fi system built prior to 1955 was only single channel (mono) reproduction. So even with a quality phono input, the question is  - "So where do I plug-in this other cable". Using a "Y" adaptor that ties your right and left stereo channels together (with no isolation) is usually a bad idea and might even damage some devices.

The simplest solution in many cases is to build a matching transformer/cable using 2 small output transformers. This will provide isolation for the R and L channels of the MP3 device along with a voltage boost - and less than great frequency response. This is still a good choice if you have a phono input or can manufacture one.


What we have here is completely different.

First a little background: Mentioned below - and still lacking the story it deserves - is a collection of radios/chassis/parts donated to the cause in early summer of this year. Among these was a Scott 510. All of the components were there including the cabinet which was the typical, rectangular, late 40's box with a couple of doors - not my favorite design. This cabinet was originally finished in the white-washed color that was popular in the 1950's. Along with the yellow-ish finishes of the same period, also, not a favorite. The overall delaminated, banged up, falling apart condition contributed to the decision to not restore.

The receiver chassis used in the 510 is good, maybe even very good, but certainly not consistent with the quality and leading edge design of earlier Scott models. So, I scrapped that chassis too.

The remaining chassis is the chrome-plated power supply/audio amp seen in the first picture, above.

This is a nice unit using a 6SN7GT driver and push-pull 6L6s for output. And look at the size of that audio-output transformer (8 ohms only). The published frequency response is 30 to 20k hz at +/- 1 db.

http://www.nostalgiaair.org/Resources/592/M0016592.htm

It was built with a dual power supply using both a 5y3GT and a 25Z6GT as rectifiers. The 25Z6 was no longer necessary since it only supplied the receiver chassis. There was also a nice large choke (underside of chassis) that was now no longer needed. Having recapped the unit, I decided that it would be nice to incorporate this choke into the amp's power supply. So I reduced the value of R48 from 375 ohms to about 275 ohms and installed the choke between the first and second filter caps.

Testing the amp using input from my Samsung phone, I found the output to be way too low to be satisfying. There was just not enough voltage out of the phone to drive the 6SN7 grids (in parallel). The extra, now unused rectifier socket was also screaming - "stick a tube here". So I did.

The objective was the same as stated above, to provide isolation, voltage gain and combine (mix) right and left channels. Since I had plenty of power supply overhead - lacking the need to power the receiver chassis, the obvious solution was the addition of a 6SL7gt stage prior to the 6SN7 driver.

So how is this done? Easy. Just look in the index of your RCA tube manual under the chapter on Resistance Coupled amplifiers. WHAT? You don't have a tube manual - don't tell anybody and get one here:

http://bama.edebris.com/manuals/tubesandvalves/

The directions are pretty simple. Pick your B+ voltage and desired characteristics from table 5 (I was using RCA 25 from 1966) and dig out the few additional parts that are needed. The drawing and specs are for a single triode. Your are just going to need to double this up for the 2 triodes in the 6SL7. The plates of both triodes will be tied together and feed the grid of the 6SN7 through a coupling cap also speced in the chart. Note that you could probably use a single cathode resistor/bypass cap, but I used 2, one for each cathode.

Most applications are going to need an additional tube socket and a person could use a 12AX7 but I already had a socket - given that it would probably be better further from the rectifier but that would require another hole and the 6SL7 that I chose had the aquadag coating which resulted in ALLMOST no hum. Rolling a few other tubes into this position resulted in some hum. I might add a shield - or not.

The test results were plenty of gain, good frequency response and little or no noise.

I also upgraded the 6L6s to 6L6GCs so that I could play with higher B+. As it is, B+ is running at about 380V. I added 2 shielded cables with RCA jacks to the back of the chassis. You might want to add a coupling cap of around .01uf to each input to the grids of the 6SL7 to provide some safety for your device should one of the grids fail and crash into the plate resulting in B+ going to your phone/device. Otherwise, isolation is good as is the mixing of right and left channels.

- - - Or the second 1926 Neutrowound.

From the post below, here is how the second Neutrowound receiver looked when it arrived - soaking wet.

Other than the rust, this one also had wasp nests inside, crunchy - dried out rubber tube mounts, open interstage transformers, missing on/off switch, missing knobs and no finish left on the wooden base.

I started off by sand-blasting all of the metal cabinet pieces and replating the corner trim and tube shields/caps.

This is one of those radios that needed to be taken entirely apart, each part cleaned, serviced/rebuilt and then reassembled.

I repainted the cabinet with wrinkle paint, which was easy since it was over 100 deg. outside. Having coated it twice, I just set it out in the sun and it wrinkled up just fine. It was then top-coated with black lacquer to bring up the gloss. CAUTION: lacquer will severely  mess up this wrinkle-paint. It must be applied really dry.

The base/board was stripped, filled and sanded then sprayed with shellac.

The rest just needed a lot of cleaning and the same re-stuffing of components that was performed on the earlier unit.

Fortunately, the missing knobs are similar to those used on a lot of 1920s radios. Unfortunately, I still need 5 of the tube shields/caps.

A couple of other notes:

Both of these radios were missing the 6 bolts that hold the top cover on and I'll bet this is quite common since reinstallation of these bolts takes a bit of  fishing. So they were probably left out having once been removed for service. If you need some, they are 4 inch long #10 X 24 machine screws with a slotted head.

If you need to replace interstage transformers, use 3:1 (three to one) rather than 5:1. If you use 5:1 transformers, you will probably end up overdriving the last audio stages. This will result in really noisy poor audio.  If you have a 5:1 with a tapped secondary, just use 1/2 of the secondary. That is what I did here.

If anybody find a few extra shields/caps, I could use a few. BTW they and the end trim are plated brass.

Russ

Sorry it has been so long since I posted. Honestly, if the smoke from the forest fires was not so thick outside, right now, I would probably be on my way to the shop.

About two months ago we were given a large collection of radios, chassis and parts. This was such a nice thing to do. The collector had just retired. He had a lot of projects and travel planned and did not want to liquidate the collection by selling individual radios.

So after two truck/trailer loads, there were radios stacked in the shop and at both the front and back doors.

Well, I may be a radio collector (hoarder), but I am also unable to allow stuff to pile up for very long. So for the past two months I have been cleaning, restoring, donating, selling and disposing of this collection. But, that is not what this post is about. The rest of that story will be posted later.


THIS story is about the two 1926 Neutrowound receivers that I acquired in the meantime.

Of the two, the one pictured above, was by far in the worst condition. Even though it was well packed, it arrived soaking wet. That probably did not account for the rust and bug nests, but it didn't help either. BTW, none of those tubes were good either. All of them had open filaments.

I am in the process of saving the specimen above. The greatest challenge will be finding the missing tube shields/covers.

For the moment, we'll concentrate on the other unit, below.

I won't take the time to illustrate the history of Neutrowound Radio Manuf. except to say that this division of Advanced Automotive Accessories only made radios for 4 or 5 years. This "Shielded Breadboard" design carried through those years with a few modifications.

Though this is a good radio, by 1926 the design was a bit dated. Then by 1928, the battery powered TRF was really behind the times. I can't really see why this design was popular in any of the years it was produced.

Pictures really don't express the size of this radio, measuring almost 3 feet long. It had 3 stages of tuning and the 3 dials rather than a single dial, as was becoming the standard of the time. I suppose that in a home that was yet to be "electrified" the need for batteries in 1927/28 was not a problem but elsewhere, the new AC powered radios were more desirable

.

Radio construction on a "breadboard" was quickly becoming a thing of the past.

There are two significant and nearly universal challenges to restoring any of these radios. The first is RUST. A crinkle coat paint was applied to the outer metal surfaces. In the 1927 models this could be a striking blue or red. In all of the models, adhesion - at least in the long term, was not so good. This lead to a lot of rusted cabinets  (see top pictures). Coupled to that, it seems that in the finishing process, shellac was applied (smeared) to the inner surfaces of the metal. This hit or miss finish led to rust on the inner surfaces as well.

The second and probably most encompassing issue is caused by the degradation of the gum-rubber mounting of the Kellogg tube sockets.

The first two tubes have somewhat of a "hard" mounting since the screws pass through the socket flanges, through the 1/4 inch gum-rubber and into the breadboard. The last 4 tube socket are fully floating on the rubber strip shown above having been replaced.

I have not seen an example of this radio where the rubber has not become powdered or at least the consistency of a sugar cookie. Needles to say, the rubber should be replaced. Gum-rubber sheet is not a common hardware item anymore and the cost of a piece may be significant. Mounting the sockets on new rubber is not an easy task either.

Above, I am holding an original piece of the rubber mount.

As you can see, mounting the sockets requires careful placement and compression of the rubber. This mount must compress the rubber without making a big hole in it, which would require starting over. I had to make a jig to hold the nuts/washers while compressing the assembly from the top. Otherwise, at least 3 (frustrated) hands would be required. By the time I made a few of these, the task was not so impossible, but at first it certainly seemed so.

Now consider what would happen if the sockets/tubes were not in the correct position.  You probably would not notice until you tried to replace the top cover and even more so as you tried to install the shields. In other words, incorrect placement results in the tubes hitting the top cover and/or the shields. The best you could hope for in this situation would be for the rubber base to give enough to allow the tube to fit through the hole at a slant - not acceptable.

Other common issues include failure of the 3 interstage transformers pictured in back, above. And, the replacement of the two .5 uf paper capacitors. I restuffed/rebuilt all three of the interstage transformers and the metal-box capacitors for an original look.

I was able to save the original crinkle finish with just a little touch-up as well as the finish on the board. Not so lucky on the other radio, but, more on that one later -