I believe that U510 is P/N 155-022 rather than the 156-022 that you have quoted. At any rate did you notice that both the A3 Trigger Selector and A4 Vertical Interface boards, U324 and U214, have the same device? It would be simple to interchange with U510 and see what happens.
I did see this problem about 20 years ago but I didn't notice at the time that there were other same devices in the mainframe. My problem was intermittent and I also trouble shot down to U510. I ordered a new device and installed it and nothing changed. I tried the usual troubleshooting techniques but nothing worked, (freeze heat push and so on). Since the boss was getting ticked off about the time I was spending troubleshooting it, I ordered a new Horizontal Amp Board and that fixed the problem. Of course that was in the days when Tek was interested in supporting even their obsolete equipment. I still have the 7603 at home now, along with some parts and that board and device, long sad story there about the company folding.
Bill
---In TekScopes@..., <chris@...> wrote :
Hi all,
My trusty 7603 developed a fault yesterday while I was using it, and I
fear that a Tek special IC has expired.
Until yesterday morning it was working perfectly. I looked away to do
something else for a couple of minutes, and when I looked back the
display had shrunk horizontally. It now looks like this:
Oddly the readout seems to be compressed into the left side, but the
main trace is compressed into the middle. I've measured a few things
around the horizontal amplifier board. The power supplies are all OK and
ripple-free, and the resistor values seem plausible based on a few
in-circuit checks.
Switching off the readout makes no difference (other than the readout
disappearing). Pressing 'beam find' has the expected effect, and it's
not stuck on.
I had a look at the waveforms going in to and out of the horizontal
channel switch U510 (156-022) and, while the input (pins 2/15) looks right:
the output (pins 12/13) looks far from right:
Apologies for the lack of vertical scale on the photos: the output is at
400mV/div and the input was 100mV/div, I think.
The 'display limit command' line, which seems to bias the channel
switch, is firmly at -15V as the book says it should be. I tried
reseating U510 but that had no effect.
Has anyone seen a fault like this before? Should I bite the bullet and
find another 156-022?
Thanks
Chris
