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HB9TC wrote:

Sam I checked that the relay and PCB connectors were secure but the only screws I disturbed were those on the top shield. I left the radio on for several hours and tested it in TX periodically and it

Mike, Did you torque any screws on the board containing the Rx/Tx relay, or any metal shield covering portions of the circuitry? Sometimes these kinds of issues are caused by hairline fractures on a

Ok Mike...No problem...have fun with the rig and feel free to ask questions should you have any....73...Jordan VE6ZT

Thanks Jordan. All the board screws were tight and I couldn't see or feel any loose connectors but if/when it fails again I will follow your advice. This radio is immaculate and shows no signs of

P.S..... Should read "...control line connectors."

All I can suggest is that you tighten all the screws fixing the board to the chassis, then pull and then reseat the dc and control like connectors...It could simply be an oxidized interconnection

Well this is frustrating ... I removed the screen cover from the Final unit to access the TX/RX relay and now it's working again ?. I couldn't see anything loose so I'm in the dark as to what's

Sorry - I now see you are asking about the 870s, not 570S.

Mike, ([A=B] + POWER ON) should be a full reset, so you should be good there. In your image what am I looking at (discolorization on the RF shielding); is that a burn mark? Random thoughts //

That's a reflection in the screening can ?. -- Mike G8GYW

Thanks Jordan, yes that was helpful. I found a good quality set of schematics on mods.dk and have identified the TX/RX relay which is switched by a TXB line. Time to start probing ... -- Mike

What is that scorched discolored area...? Looks like something arced or burned... Jordan...

Manuals sometimes show a partial reset and a full or complete reset. Bob W4JFA [email protected]> wrote:

Get the service manual and read the portion that deals with the RX/TX change-over. I'm pretty sure you'll find a description as to how the change-over is implemented. Normally there are voltages such

Thanks Bob. I tried the Full Reset described in the instruction manual ([A=B] + POWER ON) to no effect. Is that the same as the factory reset? The Mic socket and ACC2 are wired to the TX-RX Unit

If you haven't already, try a factory full reset. I'm not a professional tech but I've fixed 2 radios in the past year and a half doing a full reset. Bob W4JFA wrote:

I have the schematic, just hoping for some pointers. Nothing happens when I operate PTT, it stays in RX. -- Mike G8GYW

You should be able to find a schematic and trace the circuit, at least in theory!

Thank you David. My plan is to (hopefully) gather some suggestions before opening it up. -- Mike G8GYW