Superstar 3900 help. Early EPT360011B

smalltiredart · Nov 16, 2017

Struggling on a problem on this one.
No RX on AM and FM only.
TX is fine on both AM and FM, but No RX. No sound at all. No Meter movement etc. Even with close range radio
RX is fine on LSB and USB but noda on AM/FM

The only 360011B schematic I could find was for the "Galaxy Plus" on CB tricks

Any ideas are appreciated. I can voltage test any of switching transistors, but info on this early board seems scarce.

I have DVOM, Capacitor tester, Oscilloscope, ETC.

sp5it · Nov 16, 2017

Check attachment. It is AM/FM rx route.
Check d4, 5, 6. FL1 filter is suspected.

smalltiredart · Nov 16, 2017

sp5it said:
Check attachment. It is AM/FM rx route.
Check d4, 5, 6. FL1 filter is suspected.

Awesome !
That helps a bunch, and thank you for the schematic.
I'll give it a shot tonight.

smalltiredart · Nov 21, 2017

Removed and tested all the above diodes. Also Replaced FL1 with a known good filter, still no dice.

Doesn't even budge the S needed and 0 sound on AM and FM.

It hears fine on USB LSB and CW.

Strange one for sure. Transmit is fine so audio chip is fine.

Any other ideas ?

Robb · Nov 21, 2017

Mode switch?

I had the same problem with this radio once.
Turned out it was one of diodes already listed; not the mode switch. But a mode switch can also be a failure point here.

smalltiredart · Nov 21, 2017

Thanks Rob.

I did check the mode switch as well. With ohm meter and made sure switching voltage under power.

Robb said:
Mode switch?

I had the same problem with this radio once.
Turned out it was one of diodes already listed; not the mode switch. But a mode switch can also be a failure point here.

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Superstar 3900 help. Early EPT360011B

smalltiredart

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sp5it

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