[mancave]

I am resurrecting an Apex 26p "Gloritone" made by US Radio and Television corp. I am attaching a picture of the schematic. A previous owner threw away the original filter capacitors and I have managed to wire into new ones and have b+ voltage and a little bit of reception and plenty of volume. What should the b+ voltage b on this set? With 110 volts ac going in, it is about 155 volts.

[morzh]

You mean the RED speaker wire, or the second 8uF cap (which is the same) ate 150V? It is low. Should be over 270-290VDC or so. In some radios over 300VDC.
This is the sch.

https://www.nostalgiaair.org/pdfs/US-Rad...rp-26P.pdf

[MrFixr55]

Hi M
ancave,
+1 on what Morzh said. I have done a Gloritone 26. The difference is that mine had a '45 triode as an output as opposed to the '47 that you have. (The P in 26P refers to Pentode output.)

Voltage at the output transformer should be about 250V. Voltage at the cathode of the '80 should be about 325-350V. Power transformer secondary should be 350V between either rectifier plate lead and the center tap, or 700V across the transformer rectifier plate leads (above the ability of most meters to measure, so measure between each plate lead and the center tap.

It is important to note that the center tap of the B Power supply is NOT at chassis potential. Most sets made before about 1939 or so had resistance between the center tap and chassis ground. The chassis was B- / C+. The center tap was now C-. This was done to develop cathode bias for several tubes, particularly the -18V of grid bias required by the output tube.

Hope this helps.

[mancave]

Thank you, Morzh and MrFixr55. I now have correct B+ voltage. I was measuring the voltage when powering the set through a dim bulb. When I power it directly, b+ is correct. Also, shortly after I posted my question, I noticed that the schematic lists what the b voltage should be at the tubes. Oops. Yes, center tap of the hv secondary of the power transformer is not directly grounded to the chassis.

[MrFixr55]

Hi Mancave,

Yes, having the radio connected to the dimbulb will do that. Congrats on bringing a 95 year old radio to life.

When I was reconditioning the Model 26 I did (for a friend), I had the opposite problem. HV was too high, sound was low. My set had the '45 triode output tube. Output tubes draw the most curent and "Class A" output stages draw almost as much at no signal as they do at full blast. The weak output tube was the cause of the low sound and high B+ voltage. Replacing the tube resolved all and the set now plays loud and proud.

[morzh]

You should not do measurements when using the dim bulb.
It is 1) useless, 2) confuses everybody.

Dim wit tester is for initial safe start only, nothing else (and I am a know opponent of using it at all, most useless piece of junk. Variac is exactly what is needed).