McMurdo Silver Masterpieces were among the best radios of the time and of those the Masterpiece V and VI were particularly outstanding. They would be the center piece of most collections even if they weren't covered with chrome. Their tone, audio quality/power, BFO, audio expander and selectable IF bandwidth elevated them to the same quality and performance as units made by Scott or even the venerable Zenith 1000Z.

Masterpiece VI from 1937

BUT they are difficult to work on, even if you had the tools and schematic. Each one was somewhat custom made- in real terms. So the claim that each radio was built specifically for each buyer might actually be true AND an impediment to restoration today. (Much more on this coming in the next post)

Sadly, not many were made. I'm sure that the price had a lot to do with that. Similarly, their price today has kept them out of most collections. Worse yet, they became well known for the hi-fidelity of their components. Unlike most radios of the time, a cabinet was optional so a complete radio consists of the tuner/pre-amp (above), a power supply/audio amp (below) and a massive, dual field coil, 18 inch Jensen pedestal speaker (2nd below).  Today a complete radio might sell for around $6000.00 with or without a cabinet. Each of the components can be sold separately today (a boon for pickers on Pay-Bay). Where a nice unrestored receiver might go for around $1000, an amplifier can sell for nearly that much alone. The real problem has been that overseas demand has driven the price of the Jensen Super-Giant to ridiculous levels as high as $7000 in the recent past - around $3000 to $4000 today.

.Amplifier/ power supply

For that kind of  money, it is hard for even a dedicated radio collector to resist selling the speaker and, unfortunately that is what has happened to many of these . So, today, it has become common to find a Masterpiece receiver alone in its cabinet with the speaker and amp long gone to Asia.

The receiver chassis is still worth having, but, all of the cool functions and wonderful tone can only be imagined. Though not absolutely unique,  finding a substitute for the missing speaker is always a compromise in both quality and reduces the value of the radio as a collectors item.

Fortunately, I have just completed the restoration of a collection of McMurdo Masterpieces and there were a few parts left over. No there weren't any 18" speakers (though I have purchased one from the collection) but there was one, sad, rusty MCMV amp chassis and a single filter choke,  It seems that someone had replaced the power transformer with a smaller, unsuitable unit and, subsequently gave up on the project after it overheated evidenced by visible melted insulation on the primary wires.

I have long thought about building a power supply/amp suitable for running the many orphaned Masterpieces. I considered using a Scott 800B PS/amp. It could work. Or I could start with a brand new chassis. This would be a lot of work. It seemed easier to use the MSMV amp chassis that I already had.

After a few days of grinding and polishing my arthritis was protesting loudly. Maybe a new chassis would have been easier. But now that the rust and pitting was gone, I needed to make sure that it did not rust again. I considered gloss black paint. It would look nice but not very original for a radio known for CHROME (!). Well, I won't mess with chrome - too toxic. But nickel plate seemed like a good idea. It could be chromed later - if it just had to be done. So that is what I did.

A nickel plated chassis can be polished to nearly the look of chrome. There is a slight color difference. Chrome is more blue-ish. I wasn't going to that extreme. The way it came out, a lay-person might think it was chrome anyway unless it was sitting beside a chromed piece. I was happy- enough. And I did not have to cut out all of those holes.

SO NOW WHAT?  Having only the single filter choke and the tube sockets ment that this was going to be a custom assembly any way you looked at it. Then I had an idea - What about a universal PS/amp capable of driving any natural magnet speaker. The thought of not being constrained by the normal factory-look restoration intrigued me. "Let's take it one step further - how about a PS/amp that could run either a MSMV OR a MSMVI? So it was to be!

Now all that I needed was a pile of hard-to-find parts. I went through my transformer pile focusing on several REALLY BIG ones removed from 1960's electronic (tube) organs. I never thought that I would use one of these. They were over-kill for even the largest 30's radios or even stereo amp projects. I'm glad that I kept them.

The PS uses 2, 5Z3 rectifiers, so the trans must provide at least 6A at 5V and the DC requirement was for at least 300ma at about 450V. There was also the requirement to heat 18, 300ma tubes.  I needed both hands to lift this one!

Besides all of the little parts, I needed another choke, a interstage trans for the MSMVI input and an output trans capable of handling the push-pull 6L6s. And I needed to hit the target voltage for the receiver, around 340V under load, without having the 2 original field coils in the circuit. PLUS avoid the hum caused by removing said field coils which were also used for filtering. Skill - or luck, either would be fine with me.

Here is a list of the objectives:

1. Start with a MSMV design
     The MSMVI has the 2nd audio on the receiver chassis but the MSMV needs the 2 6C5s to drive   the push-pull 6L6s .

2. Find the missing 2nd choke at about 10h 200ma
     B+ for the output 6L6s is taken after the first choke. So the 2nd choke must be good for about 200ma.

3. Find an interstage transformer for the MSMVI input to the final audio stage.
     The 2nd audio stage is on the receiver chassis so routing the signal through the V's 6C5s will produce too much gain/noise. Also the VI uses the interstage as part of the bass control, omitting it would also eliminate this control function. A 1:1 or a slight step-down will be best since additional voltage gain is unnecessary.

4. Add a suitable output trans 
     Since the original one is on the speaker on both the V and VI. 8 ohms would be best. Ours provides both 4 and 8 ohm  secondary taps.

5. Increase the values of the filter caps to help compensate for the loss of the field coils.
     I used a 10uf 630V film cap in the first position that originally was two .5uf at 400V in series resulting in a value of .2 (point 2) at 800V. They were probably trying to take it easy on the 2 rectifiers by using a small or no cap prior to the first choke. Then a 47uf 450V 105c electrolytic in both the 2nd and 3rd filter position. I wasn't sure whether I was going to need a resistor to drop B+ to the receiver to 340V at this point so if I had to add a resistor I thought I would add a 4th filter cap as well. Turns out that neither were needed.

6. Wire the original 6 pin speaker port/socket to accommodate the VI receiver
     Since the FC speaker is not used the 6 pin plug is available to power a MSMVI  the V uses the original socket.

7. Determine the best point to insert the audio from the interstage to the final amp.
     The V application is as it originally was but I needed to inject the signal from the interstage at the grids of the 6L6s without affecting the output from the 6C5s too much. The interstage trans provides the inverted signal for the VI that was accomplished by the 6C5s on the V. The 6C5s are cap coupled to the grids  by .1 (point 1) caps. I chose this point to inject the signal using .045 caps to try to prevent some of the loss that would occur by placing the transformer windings across the output of the 6C5s.
     This worked great. I balanced the inputs by driving the amp with a stereo signal, R through the V port and L through the VI port to compare the levels. I reduced the value of R11(K) from 500K to 50K to compensate for a slight loss. This resistor is one of the "custom" parts to be covered in a later post.
     This all could be made easier with a switch for V and VI but I did not want to have to remember to make the switch - or to look at it.

8. Use 1/2 of the transformer's 12V filament winding for the receiver and 1/2 for the amp (as was done on the organ (donor organ ;)
     The receiver draws 16 or 18 X .300A or about 5A at 6.3V

9. Check for proper voltages and make adjustments.
     The new power transformer delivered about 750V for the B+ where as the original delivered about 1000V. This is OK - actually required since the resistance across the field coils will be missing. Some compensation can be made in the filter chokes. On the V they are both the same, about 10h and 50 ohms each but on the VI the 2nd one is about 10h but 125 ohms. Which explains some of the differences in the V and VI speaker field coils (again more later). The only adjustment that was needed was on the cathode resistor for the 6L6s. At the stated value of 250ohms 20W (these are almost always 10W and often show signs of overheating) we had 39V on the cathodes. So it was a good time to upgrade to a 25W 180 ohm unit which gave us about 26V on the cathodes and improved bass response too.

10. Find a place to put all of the "extra" components.
     I extended the mounting bolts for the chokes so that the output trans and interstage trans could be mounted, though I did plat the bell for the output trans and mounted it on top with the 2nd choke being relocated below. There are good reasons for doing this, also to be covered later.

11. Upgrade wire. Use 600V neoprene for a "original" look but much better service. Upgrade fuse holder since I didn't have an original. Clean up the original layout for best wire routs. Add a convenient terminal strip for the various B+ voltages. A good place to terminate the chokes and caps and take measurements.

Underside with everything mounted. The three wires coming out the top are the speaker out, 4 ohms and 8 ohms. I have not provided an on off sw yet.

Top side. Note the output trans in place of the original 2nd choke.

Above is a demo using a VI  receiver chassis. The VOM is monitoring the B+/screen voltage to the receiver chassis. The B+ to the 6L6s is about 420V.

I still need a bigger bench - - -

Russ

I was going to part it out. The two Radiola interstage transformers were good.

The "restorer" could not get the knobs off, so he could not get the chassis out of the cabinet. "No sweat"' he thought. I'll just slather poly on everything - the dials, knobs and bezels included. But first, since I can't get the cabinet stripped of the old finish properly, I'll just scrape it with a knife(?).

Well, when he got done, it looked pretty good from around 10 feet away. Sue said that she liked it. So it was diverted towards 2 or 3 days of restoration which was mostly figuring out how to get the poly off of everything.

The former owner managed to remove most of the character of the wood by scraping the front panel. So much so that the bezels were raised by a little lip where the scraper could not reach. So I added a little bit of grain and a knot or two prior to refinishing.

Completed 5-tube TRF - 4 each 199 and one UX 120 for audio output. I still need to find the paper instruction label for the underside of the lid.

Craig's List item. Before and after.
Yeah, the radio chassis had a few issues, but, so did the cabinet.

Fortunately, in the process of replacing the front veneer with a single sheet of Mahogany, the seller did not get the damaged front panel firmly glued to the arch. Unfortunately, the original trim was lost.

Since the back side of the panel was also damaged, I found it was easier to just make a new panel. The picture above shows the original front after it was reglued and cleaned up. At one point I was going to re-veneer but other damage caused me to reconsider. Much of the grill area had been "patched" with a filler similar to Bondo or some sort of wood filler.

The geometry of the arch trim is a somewhat more  difficult than most people would think. Not impossible, but, just try to calculate the inner curve (at a tangent to the outer curve).

The rest was router work and adding the Zebrawood veneer.

IF the most important consideration regarding the restoration of a chassis is the amount of rust, then this one was not so bad. Unfortunately the power transformer had been replaced and was missing it's cover. Another interesting deficiency was discovered in the tuning cap. There was just enough oxidized metal deposited on the insulators to cause the volume control circuit not to work.

This volume control is much better than a simple rheostat placed on the antenna input but also more complicated. If you get a chance, it can be seen here:

http://www.nostalgiaair.org/Resources/480/M0001480.htm

Aah, Spring, fresh flowers and old radios!

P.S. No, I didn't pay $100 for it.

Russ

Or Masterpieces - which seems a bit contradictory.

In the 1920s and 1930's there were several radios that went by the name "Masterpiece". The term would seem to indicate the best of the best at least as much a one individual or manufacture was concerned. There was the exceedingly common Freshman "Masterpiece" which was rather average as far as 1920s TRF radios go. It was a good radio, but that was about it. A better name would have been, Freshman Average Radio. Then there was the Parker McCrory Masterpiece 733 From 1937  (See: https://www.russoldradios.com/unique-radios.html  3rd entry) which was a really nice 30's battery radio. It was way above average, but a "masterpiece"? Well maybe. And then there was McMurdo Silver, a guy that intended every one of his radios to be a masterpiece. By the time he got to his 5th version, the Masterpiece V, I would say the name fit very well.

I was doing the chassis restoration on a Zenith Stratosphere for a friend and fellow radio accumulator when he mentioned having several (about 7) McMurdo Silver Masterpieces. For the most part, they had been awaiting restoration since 2015. The project had been started, a lot of the parts had been rechromed, but the chassis restoration was unfinished. One thing led to another and before I knew it I was up to my elbows in Master-pieces.

Most radio collectors do not own a Masterpiece. I would guess that  significant percentage have never seen one,   face-to-dialface.. Even more elusive are the 18-inch "Super Giant" pedestal speakers since many of them were removed along with the separate amplifier and sent off to be use for other purposes.

Having entered into this project at the end, I never got to see the original cabinets. For that matter and as you can see, UPS just started delivering parts and pieces. And, at that, many of the speakers/chassis had been partially disassembled. It was a GRAND jigsaw puzzle.

In the photo above note the chromed pedestal on the V and VI Super Giants. They were not built that way and had been chromed along with a lot of the other parts as a matter of taste. Two were to be kept and two more were to be sold along with the matching radios. The V is on top with two VIs below.

Underside of the main (radio) chassis of a MSMVI.
There seems to have been a lot of changes around the addition of a "MIC" circuit along with the "Phono" input for the VI. (left side of chassis)

Above is the power supply/amp for a MSMV. Note the 6 tubes - 2 each 5Z3, 6J5 and 6L6s. That combination gets really HOT. Keep the power cables away from the tubes. As a note for future restorers, the MSMV amp/speaker incorporates 2 field coils in addition to the 2 chokes seen above. FC 1 has a DC resistance around 400 ohms and FC2 around 4K ohms. FC 1 is inline with the B+ to the radio and FC2 is shunted to ground. You get about 350V  to power the main chassis.

The MSMVI PS/amp above has a 25hz power transformer which is much larger than a standard 60hz unit.

The MSMVI power supply/amp only has 4 tubes 2 each 5U4s and 6L6s. The supply is very similar to the V less the 2 6J5s, but the DC resistance of the field coils is considerably higher than the V with FC1 at around 700 ohms and FC2 around 8K ohms. So the speakers are not interchangeable.

Another interesting thing to note at this point is that the tubes on a MSMV are all metal by Raytheon with the exception of the two 5Z3s. On the MSMVI all of the tubes are glass except the two 6L6s which may have also been glass on some units (ST bulb). At the time of manufacture the only difference between the 5Z3 and 5U4G was the base.

MSMVI topside with coil covers (shields) removed.

There are 3 more tubes on the MSMVI receiver chassis but 2 less on the PS/amp chassis for a gain of 1 over the MSMV.

OK, OK, the only color is green.

Sold in 1948, this was one of the first budget TVs. This brings back memories of long lines of people waiting for the "Black Friday" sale at Circuit City when flat screens first became the "hot" Christmas gift. These were no less popular.

The $99 price was the best part of this TV. The real drawback was the 3" screen. Continuous variable tuning on  2 bands was a cost saver, but I find tuning to be easy, maybe easier than the click , click/fine tune two step of a conventional TV tuner.

The picture tubes were not green phosphor as sold. The original CRT must have failed and prior to my restoration somebody installed a oscilloscope tube. An original replacement is very hard to find today. The green doesn't make watching a 3" tube any better.

TV are not something I have not put much effort into, but I always wanted a small "roundie" TV for the museum.

It is hard to take a movie of a changing/reflective surface, but I tried: The input is from a HD to channel 3 (NTSC) analog converter - Below

     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