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47 1230 no fm - Printable Version

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RE: 47 1230 no fm - willydcamaro - 02-11-2018

Thanks Radioroslyn ! I disconnected 15k and it measured right on. I'll try what you suggest and get back to you. Thanks again,Bill

RE: 47 1230 no fm - willydcamaro - 03-31-2018

Hi Terry, Well plugging along on this thing. I have good am and short wave,but still no fm,no noise at all. I seem to have a problem with wiring in replacement for c419. I have tried various combos according to the original schematic which many claim is wrong. Pin 6 of the 7f8 is zero voltage. It should be 150-165 volts dc. Also pin 5 is 0 volts,it should be 3.3 volts dc. Any ideas ? Thank you,Bill

RE: 47 1230 no fm - Radioroslyn - 03-31-2018

Hi Bill,
Well the reason 5 has nothing is that 6 has nothing. The hv circuit is a little confusing because the band switch is used to short across the primaries of the 1st if transformer depending on whether it on am/sw or fm. Anyway I'd check the resistance of Z300 at the blue to red wires w/the band switch in the fm position. Should see a low resistance like an ohm or two. Then switch the band switch to am or sw to see if there is a high resistance there. Should still be low.

Happy troubleshooting!

RE: 47 1230 no fm - willydcamaro - 03-31-2018

Thanks Terry. Will do,Bill

RE: 47 1230 no fm - willydcamaro - 03-31-2018

Hi Terry,I measured 6.1 ohms on all bands.

RE: 47 1230 no fm - Radioroslyn - 03-31-2018

Ok If you have 6 ohms then you should have hv on pin 6.
Would check the contacts on the bandswitch (FS 2) . Hv comes in from R300 and goes to the switch contacts. In fm the switch shorts the primary of the AM if coil (lower left coil in Z300 leaving the hv to pass thru the primary of the fm if coil (top left coil in Z300). Follow the hv from R300 up thru the switch and Z300 where it stops is your faulty part.

GL

RE: 47 1230 no fm - willydcamaro - 03-31-2018

Terry, First thank you for your help. I really appreciate it. I will check the hi voltage path and get back to you. Thank you again,Bill

RE: 47 1230 no fm - willydcamaro - 03-31-2018

Well.. that was quick.. I measured HV going to R300 but nothing after it, so it must be in FS4. Would a bad C304 Do that ? What do you think ? Thanks,Bill

RE: 47 1230 no fm - Radioroslyn - 03-31-2018

>Would a bad C304 Do that ?
No if that was bad (shorted) then it wouldn't receive on AM.

RE: 47 1230 no fm - willydcamaro - 03-31-2018

Hi Terry, do you mean it would receive am while switched to fm ? I don't understand why there is no HV after the R300. Thanks again , Bill

RE: 47 1230 no fm - Radioroslyn - 03-31-2018

No, It would receive am when the bandswitch is in the am position.
> I don't understand why there is no HV after the R300.
I'm thinking that it's getting lost in the bandswitch. Do you have hv on both sides of R300? I'm assuming you as if you didn't it wouldn't receive on am.

RE: 47 1230 no fm - willydcamaro - 03-31-2018

Terry, no I don't have hv on both sides of r300,but am works fine. Thank you,Bill

RE: 47 1230 no fm - Radioroslyn - 03-31-2018

Ok you have it on one side?? Do you have it on both sides in am?? Is it the proper resistance (abt 50K)?? If so then measure the resistance from the top of R300 to chassis ground. Should see a high resistance maybe 25K or better.

RE: 47 1230 no fm - willydcamaro - 04-05-2018

Well I think I'm done with this nightmare. I soldered a loose wire on 7f8, and noticed increased hum. I now have no hi voltage after R100 15k resistor....again. No am,no fm, no sw. Thanks to all for your help..........Bill

RE: 47 1230 no fm - willydcamaro - 04-06-2018

Good Morning, does anyone have photos of the underside of 47 1230 ? Thank you,Bill