[SanDegan]

I am in need of some help.  

I have a Philco Model 84 (I think model b) that I have decided to restore.   All of the leads attached to the power transformer are crusty and the shielding is breaking.  I removed the transformer and plan to re-sleeve them.  I gathered up some test equipment, isolation transformer, variac, and I built a dim bulb tester.

Now the problem.  This transformer has 9 leads. The schematic I have for the radio shows the transformer should have 10 leads, two secondaries with a center tap on each and the third without. I found another schematic for a 37-84 it shows only 9 leads but with different tubes.  I found on ebay someone selling a transformer with the same model number (different year) but it has 3 leads for the primary where I only have two.

All leads on mine ohm out so no shorts.  I found the center tap for one of the secondary windings.  I tested up to 115 volts and I see 5v on one winding, 270v on another and 3 on another.

Does anyone have any data (expected voltage, ohms etc) for a 32-7180N transformer.  My date code is 6-35

Thanks
(fyi I am new to this)

[Radioroslyn]

Hi and welcome,

Here is a list of the output voltages of the power transformer.  https://philcoradio.com/library/download...%20178.pdf

[SanDegan]

The schematic linked is the one I found.  Unless I am reading it wrong it shows 8 secondary leads. Two secondaries with a center tap.  My transformer only has 7 secondary leads. 1 center tap.

After doing some more testing, I fear this transformer may be toast.

Findings with 115V applied to primary

1st secondary (no center tap) 5V output
2nd secondary (with center tap). Using center tap, 277V and 278V output .  Without center tap, 598V  output
3rd secondary (no center tap) 107.1V output. I was expecting 6.3

Thoughts on findings would be greatly appreciated.

Thanks.

[Radioroslyn]

What happens if you connect a 120v light to winding 3?

[MrFixr55]

That sounds strange and almost physically impossible.

Ohm between the primary and that secondary, and check voltage between one leg of the primary (preferably neutral and each leg of the secondary in question. Resistance between primary and secondary should be infinite. Voltage between the primary and this or any secondary should be zero (a slight resistance, such as 10 - 100K Ohm may have to be placed in parallel with the meter leads if a DVM is being used. The 5V and 6.3V windings should both have very low resistance as they are short windings with rather thick wire, making it physically impossible for that winding to put out 107V.

Is this the original transformer?

If you find a short between the primary and secondary of this transformer, check the wiring. You may have accidentally put the primary and secondary in series, in a "buck" mode.

Several companies, such as Arvin and RCA were not above using a transformer with a high voltage secondary to power a series filament string/ on some models. However, this is rare.

When Philco (likely the first as they were a major manufacturer of car radios) and others started using 6Volt tubes for AC powered radios (6V tubes were originally designed for car radios an the filaments were rated for 6V even though they served as heaters for a cylindrical cathode), they followed the practice of having a grounded center tap on the filament (heater) secondary winding of the transformer. Either this was found to be unnecessary at the time or improvements in tube design rendered it unnecessary to have a grounded center tap. Therefore the center tap was eliminated and one leg of the 6V winding was grounded.

Several transformers of this vintage including from the 80 and 81, as well as from the 37-84 should work, as well as others of the vintage. The 42 (6F6 draws more filament current than the 41 (6Kg but this is a 4 tube radio. A transformer form a 5 tube radio should fit.

Interestingly, both the 84 and 37-84 list the same part number for the transformer (32-7180). However, while the schematic for the 84 shows the center tap for the 6V winding to be connected to the center tap of the B Supply winding (and technically not at chassis ground potential, the 37-84 (same set, only uses Octal tubes) does not show a center tap for this secondary but has one leg at chassis ground.

This radio is an interesting set. It is a direct descendent of the 80 Junior, a radio that caused almost as much of a stir as the Philco 20 (which started the "Cathedral" radio craze). The 80 was designed in the throes of the great Depression to be cheap but work. It was actually a superheterodyne with a36 tetrode "autodyne" convertor (1st detector) but no IF stage, a 36 grid leak detector with adjustable regenerative feedback, as a second detector, no first AF amp, and a 42 pentode output stage. The closest RCA competitor, the R28 (and others) Radiolette was a superior constructed Superhet, using a 58 tuned RF amp, a 2A7 (just released) Pentagrid Convertor, no IF Amp, a 58 biased "power" detector and 2A5 output stage. the Philco 80's purpose was as a "loss leader" to get people in the store where the sales rep would attempt to "upsell" the Customer to a more expensive Philco radio. However they sold thousands of these, starting at $19.95, and eventually dropping the price to $14.95. This caused RCA to sell its R28 "Radiolette" almost at a loss, and they still could not compete with Philco. Between these radios, the 20, the 70, etc., Philco became the #1 selling brand. They updated the 80 with the 81 (Pentode 1st and 2nd detectors and "Police Band", then your 84 (same as the 81 but no police band), then the 37-84 (same as 84 but with Octal tubes).

Having serviced an 80 and owning an RCA R28, I was very impressed with the 80's performance and tone.

[SanDegan]

Thanks for the help.

The entire problem was of my own doing. In that test set up, I connected the mains supply from my dim bulb tester to the filament winding’s. Yes, the bulb got brighter as the voltage was increased. I failed to grasp the concept.

Now that I have figured out my error, everything now tests as it should and all voltages are as expected. In the correct configuration the bulb did not light up as expected as there was no load on the transformer.

[SanDegan]

MrFixer55

Thanks for the history of the 84. My great – great grand father bought the radio new. He was not a man of means so it was a big expense. He wanted to be able to provide some entertainment to the family in rural upstate New York and to be able to hear news, particularly regarding Europe.

[MrFixr55]

In modern times, we marvel that these radios were available so cheaply, but we must remember that the 80 Jr's $14.95 price was 2-3 (or more) days wages of a worker in 1933. Add to that the fact that many rural areas lacked power. Upstate NY did have the Niagra hydroelectric power plants. Touring them is on my bucket list. Although I am a New Yorker, I am totally on the other side of the state (Long Island) and a full 400 miles away.

Radio was the "internet" of the 1930s, which is why so many radios of the time had shortwave bands to get European or Asian stations. It is very interesting (and scary) piece of history that in Nazi era Germany, high end receivers were confiscated, and people were reduced to buying the VE301 Volksemfanger ("Goebbels' Snout") radio, capable of only receiving local (propaganda) broadcasts. Receiving foreign broadcasts in Nazi era Germany was a crime punishable by prison and possibly death. Compare this to the US where you could buy the radio of your choice (if you had the money, otherwise, you could build one).

[radiorich]

Hello Mr Fixr,
For sure I have sears Silvertone little tabletop and in the 30s it was about $8.00

Sincerely Richard

[Radioroslyn]

I remember working on a Silvertone set from '36 that had a power transformer. But it was an autotransformer... http://www.nostalgiaair.org/PagesByModel...017073.pdf Cheap design and shock hazard.