[Premium-Rx] Collins 851S-1 help needed

[Heinz Breuer]

Hello Peter,
sorry to hear that your 851S-1 shows "FAULT".

Your problem sounds like a defective tantalum capacitor. Are you sure that ALL tantalum capacitors have been replaced? I have not counted but I guess we are talking about 100 capacitors or even more.

I have maintained and repaired my three 851S-1 and a few for local friends but my friend Zlatko 9A6SUE in Croatia is a real expert on the 851S-1. He has refurbished and repaired about 100 receivers. I understand that it is not economical to ship the 851S-1 to Croatia and back. We have to isolate the defective module first.

I hope you have the service manual. If not you can download it from www.mods.dk
You have to register first. Download is free but as a non paying member you are limited to ONE download every four days. Be careful where you click (pictures, mods, manuals) as every click counts as a download.

As a first step you should check all operating voltages. Remove top and bottom cover. Turn the 851S-1 upside down and measure all operating voltages at the screw terminals on the power supply.

Next step switch off the 851S-1 and lift out of the socket or remove all boards and modules including the boards inside the synthesizer box with the exception of A10 Control board.
Insert one by one Board/Module and every time switch on the 851S-1. Turn the VFO knob and check if the FAULT led goes off. If it goes off the Board/Module is OK. Switch off the 851S-1 and insert the next Board/Module. Switch on again and check ...
If the FAULT led stays ON you found the culprit.

Let me know what you find out.

BTW there is one tantalum capacitor located on the synthesizer motherboard. If it is defective you should see it when checking voltages at the power supply screw terminals when all Boards/Modules are lifted.

vy 73 Heinz DH2FA, KM5VT

Von meinem iPhone gesendet

> Am 14.07.2019 um 19:08 schrieb PETER PATTON <peter.patton at cox.net>:
> 
> I have a fully optioned Collins 851S-1 which suddenly shows a receiver fault light. I hear static but no signal. The tantalum capacitors have been replaced and it has worked perfectly for years. Any suggestions for someone who can repair this radio?
> 
> Pete Patton W0EWQ
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