Re: 11801, 11801C and CSA803A repair projects

Reginald Beardsley

In an attempt to get access to the calibrator I removed the nuts holding it in place per the service manual instructions. In the process I made a major tactical error and dropped one of the nuts into the instrument!

If you need to remove the calibrator for any reason, loosen the nuts and then use a multi-prong grabber to remove them. It's also advisable to have the instrument resting with the RHS on the bench. That will prevent the nuts from falling into the instrument.

As a consequence I now have both covers off the instrument at the same time. Fortunately, the nut fell out when I rotated the instrument.

The calibrator pin header is connected to J91 on Timebase Controller which is much more accessible for probing.

brown ???
red +4.93 V
orange ???
yellow ground
green ???
blue -4.93 V
purple ???

I have a clean square wave on the 3.5 mm line going to the calibrator. Does anyone know what signals should be on the brown, orange, green and purple wires? All I see with a scope is mV level noise.

Access to the signal path is through the RHS and the top. Both covers have to be off. The far RHS board is the TDR/Strobe buffer. The sampling heads plug into an interconnect board via ribbon cables. It's unclear from the manual if you can reseat the connectors in the signal path from the RHS after removing the TDR/Strobe buffer. But that looks to be the case. As I don't have signal path issues I don't want to mess with it.

I pulled the I/O board. As I expected the self test was turned off. In fact, all the jumpers were set to zero. I set them all to 1 in hopes of getting 19,200 baud on the RS-232 port, but it still reports 9600. Does anyone know if they will actually do 19,200?

I'm now throwing a T1331 error. That should be cleared if it boots normally. I saw this with #1 after I replaced the NVRAM. Do I need to jumper this to not halt on an error and then rejumper it? Pulling the card from the cage is a PITA. I remember the error from when I replaced the NVRAM in #1, but it cleared after a couple of boots. In this case, that is not happening. #1 is on a shelf 4+ ft from the floor, so I really don't want to wrestle it down to take apart to compare stuff.


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