The PHILCO Phorum
American Bosch 5AC - Printable Version

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RE: American Bosch 5AC - dseverson - 07-04-2015

No hum on pin 3 of 47.

I think the power transformer is bad. Can't get a steady reading on any of it and I don't get any readings on the other tubes.

RE: American Bosch 5AC - Radioroslyn - 07-04-2015

Ok remove the 80 tube. Set meter to >500ac. Measure voltage from the ungrounded side of R-12 (should be a big resistor, wire comes from the power transformer) to pin 2 of the 80 socket and then pin 3 of the 80 socket. Should see about 300-350vac on pin 2 and then pin 3 should be the same. If that is OK check R-12 it may be open.

Terry

RE: American Bosch 5AC - dseverson - 07-04-2015

I don't get any voltage readings on pin 2 or 3. Actually, one one of the pins (not sure if it's pin 2 or 3) the meter starts at over 1000v and drops to 0v. The other starts at about 20v and drops to 0v. R12 checks good. It's a 400ohm 5w resistor and it checks at 408ohms. With the set turned off, pins 2 and 3 show 358ohms and 386ohms. Not sure that matters, though.

RE: American Bosch 5AC - Radioroslyn - 07-05-2015

Try measuring the AC voltage across pins 2 and 3 of the 80 socket with the power on. Should see about 600vac. Be careful. Hope the transformer is good cause the replacement is going to be hard to find.

Terry

RE: American Bosch 5AC - dseverson - 07-05-2015

Hope springs eternal but this time the fates got to it. Measuring between pins 2 and 3 with the power on shows infinity.

RE: American Bosch 5AC - Radioroslyn - 07-05-2015

(07-05-2015, 11:07 PM)dseverson Wrote:  Hope springs eternal but this time the fates got to it.  Measuring between pins 2 and 3 with the power on shows infinity.

Autorangning meter? Can it read 600 or 700vac? Some digital meter won't read that high of an AC voltage.

Terry

RE: American Bosch 5AC - dseverson - 07-06-2015

No, it's not autoranging. I set it to read from 500v to 2000ma.

RE: American Bosch 5AC - jerryhawthorne - 07-06-2015

dseverson, your post on meter reading setting does not make a lot of sense to me. Is it set to max A/C reading and if so is that 500V A/C? The statement of 2000ma is confusing unless your measuring current. If you are at 500V A/C it is understandable as Terry indicated that your meter will not read the voltage present as it is too high.
Go back to Terry's post #17 so you can measure each leg (plate) to the chassis. It should cut the voltage in half and be within the range of your meter.
Best, Jerry

RE: American Bosch 5AC - dseverson - 08-07-2015

Finally got back to working on this radio. I went back and removed the 80 tube and took voltage readings on pins 2 and 3 fromthe ungrounded side of R12. I get about 380 volts on both. Also checked R12, a 400 ohm power resistor - not sure of the watts. It measures 408 ohms.

RE: American Bosch 5AC - Radioroslyn - 08-09-2015

OK so plug in the 80 tube and with the set on measure the DC +voltage from pin 1 or 4 to the chassis. Should see a couple of hundred volts. Next measure the DC voltage on pins 2 and 4 of the 47 tube separately to the chassis. Again should see a few hundred volts at both.
If you like I can send you a pm with my fone# Might be easier and quicker that all this typing!
Terry