morriso2002@... wrote:
Timebase plugins however are not so easy to find - in fact if anyone
has a spare 21A/22A combo for disposal I would be happy to give them a
good home here in Melbourne Australia :-)
Morris
Hi Morris,
There was an extensive modification to the 21A and 22A tunnel diode triggers
at SN 11000. 21A and 22A timebases have the older tunnel diode trigger
circuitry in them from SN 7000 to SN 10999. I would stay away from those
unless they have had Mod Kit 040-0417-00 installed. The kit is very complex
and includes a double sided circuit board and lots of hard to find parts so
it would be almost impossible to try to put this kit together from scratch.
The early TD triggers were very unstable and I can remember being very
frustrated trying to get them adjusted so they would continue to operate
reliably.
They way to tell if the mod has been installed or not is too look in the
timebase in question on the top of the chassis and just behind the front
panel about an inch to see of the etched circuit board is installed there.
The early 21A and 22A timebases had a couple of short rows of the small notch
ceramic strips installed there with the early TD trigger circuits installed
on them.
Stan
w7ni@...
