Drake SSR1 solid state Communications Receiver

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Bought this radio at a buy-and-sell and after I used it while away from home several times, it stopped working. I opened it and had a look around and then did web searches for any service manuals or any other information. Did not find a service manual but did find a couple of good circuit diagrams. There was at least two version of the circuit and the radio I have is the latter version with 7400 and 7490 logic chips in the harmonic generator. Someone had already replaced the transistor and zener diode 5 Volt regulator with a 7805 so all i had to do was tidy this up and use more modern bypass capacitors on the device. Emailed a fellow in the USA who worked for Drake still although they were no longer into Ham Radio and he was looking after these heritage radios. He suggested the problem was in the 3SK39 Dual Gate FET and as I could not find then easily DownUnder he sent me some in the post. I replaced Q6 but the problem still existed.

Put the radio away in the junk shed saying it will have to wait until I retire and have more time. Did I say retire ? I retired four years ago and I do not know how I had time to ever go to work. This time the Drake had to wait until I was layed up recovering from a knee replacement.

You will notice a note about the two hidden fuses I have scribbled on the bottom cover plate. I found these the hard way, wasted quite a bit of time finding out why it had completely stopped while I was poking round inside.

Got it out of the shed in mid January 2015 and had another try at fixing it. I found a German language manual on Mods.dk for the Standard SR C-6500 (the same radio with a different front panel) and this had a better block diagram, it had the transistor designations on each block of the block diagram. I had worked out the first local oscillator (45.5 to 75.5 MHz) was Q6, a 3SK39 dual gate FET, and it was not oscillating below 48.5MHz. What could cause that ? My answer was little ceramic capacitors that had gone low in capacitance.

Replaced all the ceramic caps around the Colpits Oscillator and now the SSR-1 is working like it was intended to. The original Drake manual that came with the radio had a stamp on the front cover reading Seiwa Corporation, perhaps this was the manufacture of Standard radios. I have a 2M hand held by that brand name in my collection of "stuff".

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Written by and Copyright, Phil. Storr © Last updated 31th January 2015