1935 GE Model A-53 AM/SW Tombstone Radio

[old_coot88]

Bridging simply means "connect in parallel with", using a pair of clip leads. So bridge (jumper) each individual electrolytic (one at a time) with a single unit of equivalent or higher ratings. Note correct polarity.

The caps in question would be C19 and C20 (main power supply filters). You could jumper each with something like a 20mf 450V unit and see if it affects the hum.

EDIT. Those two caps should be replaced as a matter of course anyway. If they're the original cans they could be left in place for aesthetics, but out of circuit. There's also C26, a low voltage electrolytic across the cathode resistor of the 6F6. It won't cause a hum problem, but will cause reduced volume if it's gone open. It should be replaced anyway.

[vortalexfan]

Originally Posted by old_coot88

Bridging simply means "connect in parallel with", using a pair of clip leads. So bridge (jumper) each individual electrolytic (one at a time) with a single unit of equivalent or higher ratings. Note correct polarity.

The caps in question would be C19 and C20 (main power supply filters). You could jumper each with something like a 20mf 450V unit and see if it affects the hum.

EDIT. Those two caps should be replaced as a matter of course anyway. If they're the original cans they could be left in place for aesthetics, but out of circuit. There's also C26, a low voltage electrolytic across the cathode resistor of the 6F6. It won't cause a hum problem, but will cause reduced volume if it's gone open. It should be replaced anyway.

Its already been done, none of the electrolytics in the radio are original to the set, that was the first thing I did when I got this set, was replace the old electrolytics, which I left the old cans in place for aesthetics and wired in some new electrolytics which I installed onto some isolated terminal strips that I soldered ontop of the old electrolytic can's positive terminal (the terminal strip's attachment lug was isolated from the terminals so the original cans are still out of the circuit but are being used as an attachment point for the terminal strip for the new electrolytics without affecting the circuit, its a trick I learned from Mr. Carlson's Lab.)

I checked the capacitors that I installed in the radio and they still test good yet on my ESR Meter, (they mesured about 4-6 ohms ESR and they both are 2 4.7 MFD 450V axial lead electrolytics paralleled together to make 10 MFD at 450V).

And then the low voltage electrolytic is a 10/10 @ 160V Firecracker type electrolytic cap like the original was, and that one tests fine as well.

So unless one of these caps failed in a manner I'm not aware of, or that the ESR meter wasn't able to detect (dead shorted) then I don't think the electrolytics are to blame here.

[dieseljeep]

Originally Posted by vortalexfan

Its already been done, none of the electrolytics in the radio are original to the set, that was the first thing I did when I got this set, was replace the old electrolytics, which I left the old cans in place for aesthetics and wired in some new electrolytics which I installed onto some isolated terminal strips that I soldered ontop of the old electrolytic can's positive terminal (the terminal strip's attachment lug was isolated from the terminals so the original cans are still out of the circuit but are being used as an attachment point for the terminal strip for the new electrolytics without affecting the circuit, its a trick I learned from Mr. Carlson's Lab.)

I checked the capacitors that I installed in the radio and they still test good yet on my ESR Meter, (they mesured about 4-6 ohms ESR and they both are 2 4.7 MFD 450V axial lead electrolytics paralleled together to make 10 MFD at 450V).

And then the low voltage electrolytic is a 10/10 @ 160V Firecracker type electrolytic cap like the original was, and that one tests fine as well.

So unless one of these caps failed in a manner I'm not aware of, or that the ESR meter wasn't able to detect (dead shorted) then I don't think the electrolytics are to blame here.

Remove the rectifier tube and check the HV windings on pins 4&6. Should be around 600 volts AC or 300 volts from either 4 or 6 to ground. If it seems to be in order, replace the 5Z4 with a 5Y3. Maybe the 5Z4 got damaged!
I would leave the 5Y3 in there! I don't trust the old-time metal rectifiers!

[Electronic M]

Originally Posted by vortalexfan

Its already been done, none of the electrolytics in the radio are original to the set, that was the first thing I did when I got this set, was replace the old electrolytics, which I left the old cans in place for aesthetics and wired in some new electrolytics which I installed onto some isolated terminal strips that I soldered ontop of the old electrolytic can's positive terminal (the terminal strip's attachment lug was isolated from the terminals so the original cans are still out of the circuit but are being used as an attachment point for the terminal strip for the new electrolytics without affecting the circuit, its a trick I learned from Mr. Carlson's Lab.)

.

If the negative of the can is grounded you could alternately solder the terminal strip to the chassis so the mount lug of the strip can be used for a negative terminal...you need a powerful iron to do it that way but it can clean things up a bit in some cases.

[old_coot88]

With an ohmmeter set to RX1, be sure the negative ends of C19 and C20 are securely grounded (zero ohms) to chassis. Any resistance here would definitely produce ripple in the B+.

[vortalexfan]

OK, so a little update with this radio:

I changed out the 5Z4 for a 5Y3G tube and installed a 6V6G tube into the radio and the hum has gone away, but a new issue as arisen, whenever I touch the chassis anywhere including the knobs or ground my signal generator to the chassis, the radio goes completely silent.
But then when I remove my hand or the signal generator ground clip from the chassis or from any of the knobs, the radio comes to life.

Is it because with this radio being made to utilize the metal tubes they had one of the heater pins grounded to the shield pin of those tubes and thus to the chassis?

If so should I go and unground those heater pins to make this radio work with more modern glass tubes?

[vortalexfan]

Well I got it working, unfortunately it has to be turned up full blast in order to hear anything on it, which is what you guys warned me about with this unit because of its lack of AVC circuitry, the hum is still there but its not nearly as bad as it was, in fact when I turn the volume up all the way the hum goes away.

Unfortunately I couldn't tell how good the reception was on it because my housemate (who caught covid from his dad) had his desktop computer running (which is a high end gaming desktop) which has a super noisy power supply which basically renders AM Radio useless in my house, it just sounds like a a bunch of hash noise, across the whole dial with one local station that manages to break through the noise, the weird thing is that the noise seems to be not only on the AC line but also radiated through the air because even my battery radios are affected by the noise...