Yep. A very frustrating amp to work on. They desperately need a
removable cover below the tube socket area. Getting to anything on that
control board is a mission as well.
Not a nice machine to work on.
73, Alek. VK6APK
On 1/02/2014 1:40 AM, Tom Osborne wrote:
Well - got it fixed. It was the filter caps. Also ran into another
problem (that I caused) when working on it.
I was going to take the sub chassis with the tube sockets out to check
the bottom. After loosening one of the screws, found it was the one
that held the tube socket in, not the one that held the chassis in.
After loosening it, I decided not to take the chassis out.
Problem was - now I've got a loose screw holding the socket in as the
nut fell off. No problem - right?
Yes, there was a problem. When I fired the amp up, I was getting a
bad motorboating sound in the radio. Rechecked all the caps and they
were tight. I took the tubes out and put them back in one at a time
to see if it made the noise. Put 3 of them in and all was OK, but
when I got to the last one, the noise started again. It was the one
with the loose screw on the socket.
I had to remove the sub-chassis to get to the bottom of it and put the
nut back on and now all is OK. Seems that was holding the ground for
the grid. Doesn't work very good when it's loose :-) 73
Tom W7WHY
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