[Daniel _NM]

Hello to all forum members,

Thanks in advance.

As I mentioned in another post, I'm starting to restore a PHILCO Model 54 radio receiver.

I'm running into a variety of different problems.

Someone, at some point in the past, substantially modified the circuit and electronics of the set: they removed the original tubes and replaced them with octal, European-type tubes, and also removed the wirewound resistors.

Given this situation, I haven't dared to plug it into the mains yet.

On top of that, the heat shield mounted on the inside of the wooden cabinet is made of an asbestos sheet — a highly carcinogenic material.

With all this in mind, I'm considering stripping out all the wiring/components inside the chassis, sourcing the original-type parts, and rebuilding it according to the original schematic.

This is a set designed to receive frequencies and stations that are no longer in commercial use today, so restoring it back to original/stock condition wouldn't really serve any practical purpose. Even so, I think it would be a good way to give value back to a piece of vintage technology.

Before I start taking anything apart, I wanted to ask for advice from anyone on the forum — I'm sure many of you have run into a similar situation before and have experience that I currently lack.

Thanks again to everyone.

[MrFixr55]

Hi Daniel,

This set covered the US broadcast band of approximately 550-1,500 KHZ and about 1.5 to about 4MHz (200-75M). Is the Broadcast band totally obsolete in Spain and other parts of Europe?It is in danger here but is currently quite active here.

There are inexpensive low power AM transmitters available as kits, preassembled or plans for 1930's era "Phono Oscillators" that can be used to generate RF signals receivable on this radios, using a CD Player, MP3 Player or computer as a source of audio. The USA regulatory Agency, the FCC (Federal Communications Commission) allows the use of these without a license as long as the power level is under 100 mW, the antenna and ground wires don't exceed a certain length and that no one complains about interference. Check for local, national and EC regulations for your location.

There are 2 ways to restore the set:

Using the appropriate schematics and specifications for the substituted tubes, ensure that the wiring is correct, recap and test.

OR

Rebuild the set to the original schematic.

Regarding the asbestos, it is dangerous only if it is inhaled. If it is stabilized, it is not as dangerous. If you are worried about it and want to remove it, thoroughly wet it down or tape over it before pulling the staples that hold it in place, carefully remove, place in a sealed bag and dispose per your local regulations. You will then have to fashion an appropriate insulator such as fiberglass

[Arran]

Daniel;
Can you confirm that your set is a U.S Philco model 54, Philco of Canada started re-using old model numbers during the 1940s, and many of those would have used octal and or loctal tubes, a Canadian Philco would have a metal plate on the rear of the chassis. Another possibility would be that it's a British Philco, but I think they used a different model numbering system . The reason I brought this up is that a model 54 from the early 30s and looks like this https://philcoradio.com/gallery2/1933b/#Model_54C
Regards
Arran

[Daniel _NM]

Good afternoon.
Thank you to Sr.Fixr55 and Arran for your replies.
Thank you to everyone who read the message.
I’m attaching photos showing the unit’s current condition.
Except for the logo on the casing and the name on the speaker, it has no labels or markings.
Based on information from the PhilcoRadio.com website, I’ve concluded that this is a Model 54.
Any ideas, references, or comments are welcome.
Greetings to all forum members.
Greetings to all forum members.

[Arran]

Daniel;
You are correct about your set being heavily modified, though the original set was also a series string set, here is the service info: https://philcoradio.com/library/download...l.%201.pdf I do not believe that it was intended for export, though I have heard that parts of Spain used to have 117-120 volt AC mains rather then the 230-240 they have today, so it's original owner may have been able to use it, as it was. Whoever modified it obviously wanted it to have long wave, or at least to have the band switch on the front, the original design had medium wave, and the old "Police Band" which covered what is now the upper part of the medium wave band. A few good points though, you still have the original speaker, knobs, and dial scales, and the cabinet is in good condition, apart from the extra hole.
It may be easiest to see if someone has a chassis for one of these sets, one that is mostly original, then to locate all of the original parts for this one. I think you are wise NOT to plug the set in, it looks like whoever modified it did so with the intent that it be operated from 117-120 volts like the original circuit, but replaced the old style American tubes with European Rimlocks, which were popular from the late 1940s through the mid 1950s. I have a British made Bush DAC-90A which likely uses the same tube/valve types as your set.
Regards
Arran

[Daniel _NM]

Good afternoon, Arran.
Thank you very much for your reply, comments, and explanations.
I have to admit I’m a bit confused.
I decided to buy this unit because I liked the cabinet.
But the electronic restoration work is much more extensive than I thought it would be.
I’ve read the posts on Ron’s blog (R.I.P.). Maybe I’ll follow his instructions.
Thank you all very much again.
Greetings from Spain.

[MrFixr55]

Hi Daniel,

Thanks for the pictures. It appears that the person tried to do a good job and tried to make a European version of a common American 5 tube circuit that was popular from about 1941 to the end of the vacuum tube era in the USA. The "All American 5" circuit used a "pentagrid" (heptode) converter, a "remote cutoff" pentode for the IF (intermediate frequency) stage, a combination diode / triode tube for the detector and first AF Amp and a power pentode for the audio power output amp. The DC for the set was provided by a rectifier. The original Philco 54C was an early version of this circuit. It seems that the person rebuilding this set also replaced the IF transformers and all capacitors and resistors. Nothing other than the tuning capacitor, speaker and the chassis itself is original.

The filaments (heaters) for these tubes are wired up in series. if the total operating voltages of these heaters in series did not add up to power line voltage, then resistance had to be added to compensate for this. In the US, the popular tubes were a 12SA7 (converter), 12SK7 (IF), 12SQ7 (Detector / 1st AF) 50L6 (Output) and 35Z5 (Rectifier). These heater voltages added up to approximately 120 Volts. The original 54C had heater voltages that added up only to 68 volts at 300 mA so sufficient resistance had to be added to make up the mains voltage.

It seems that the only original parts that remain in this set are the chassis, speaker and the tuning capacitor.

My recommendation is to make a note of the tube types used in the modification to your set. Feel free to list the numbers on the tubes here. Thee appear to be European 7 pin or 9 pin miniature tubes. If they have the same functions as listed above, try to trace out the current diagram based on the tube diagrams for the tubes used. The circuit may be legitimate. Do change out the electrolytic capacitors. Everything else should be OK, but you have to determine, based on the total heater voltages and any resistors in series with the heaters (they may have used a motor capacitor instead of a resistor) to determine the voltage that the original rebuilder designed this radio to operate from.

THE ONE BIG ISSUE HERE IS SAFETY!!!!

Radios of this type have their chassis connected to one side of the power line. Worse, that usually happens through the power switch making the radio to be dangerous no matter how the plug is inserted. I assume that in Europe, one side of the power line is at "Earth" ("Ground") potential If your mains voltage is in the order of 220 volts, this makes it even more dangerous. The original Model 54C had an interlock to completely disconnect power when the back was removed.

Here is a link to a very good article on this issue:
https://antiqueradio.org/safety.htm

If you can't get to this document or need it translated to Espanol, let me know.

Good luck and God Bless!

[Arran]

Daniel, Mr. Fix;
The tubes used in this set are "Rimlocks" they were a development of the Phillips group of companies, they used sockets with a collar, and the tubes themselves had 8 pins with a stub or "key" stinking out the side to locate the tube in it's socket. There does not appear to be a dropping resistor in this set, but the rimlocks developed for series string sets typically added up to 120 volts volts with the dropping resistor dropping the remaining 80-120 volts from the power line. However the tube heaters draw about 100 milliamps as opposed to the 150 ma that later North American series string sets typically used. The mixer oscillator tubes/valves in European sets typically used a triode-heptode combination rather then a "pentagrid" configuration, in this case likely a UCH41, though there were exceptions of course.
Whether the chassis is connected to one side of the power line I would have no way of knowing as this is some sort of later conversion, possibly using a "kit" of parts, some manufacturers used a "floating chassis" and some did not. In the case of my Bush DAC-90A it is a "hot chassis" set, and there is a safety interlock on the power cord that disconnects the cord when the back is removed, and the knobs have shafts, with grub screws, that extend inside the cabinet so the operator to reduce the shock hazard.
Regards
Arran

[MrFixr55]

Hi Arran,

Yeah on closer view, I see the spring clip and locating notch.

Hi David,

If you can, please list the tubes that are used.