[Boatanchors] Nasty Collins Problem
infomet at embarqmail.com
Fri Jan 28 00:20:18 EST 2011
I got out my trusty Collins 310-B to get ready for CX this weekend. I knew
it had had soft keying for a while and I was able to fix that quickly,
although it's not clear just what was happening. The time constant in the
grid block circuit was wrong, even though the components seemed OK. I can
wait to get to the bottom of that.
BUT, I've also had low drive to the 2E26 on 80M, but fair drive on 40.
Historically, these have been high, with drive to spare. The manual is fine
for alignment instructions and there's a good schematic, but no typical
supply or signal voltages. After much adjusting and hand wringing, I
convinced myself that the PTO was not putting out the requisite drive to the
first 6AG7. While contemplating the tedious task of pulling the PTO and
opening, it dawned on me that I had a similar PTO I'd been carrying around
for the last 40 years or so. The PTO is connected to the circuit with a
four pin plug, so I tried the old one. WOW, ten or fifteen times the output
voltage and plenty of drive to the buffer string!!
So now the nasty part. Pulling the pto is not easy, but not hard, just
tedious. And when I get it out it will have to be opened. Maybe I can put
the other one in. It looks to be the same mechanically, but I'd really like
to fix the original. Has anyone still alive had one of these open and does
anyone know likely failure points? It's been sealed up since 1947, when my
dad's radio club bought the 310-B, so who knows what I'll find in there.
And yes, both tubes are fine!
Lastly; it won't help with this CX, but does anyone have a 70E-8 lying
around for possible sale?
I may have to drive my 1930s amp with an Icom 730, which won't get me many
Thanks for any info you can provide,
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