EG&G 5210 Lock in Amplifier

[(*steve*)]

@cchu2k asked the following questions via PM, and I have finally done as promised and placed them in a thread.

I have an EG&G 5210 lock in amplifier. It powers up and freezes. I was wondering if you have service manual. There are bunch of blue jumpers on the main logic board. Do you have information on them? Thanks!

Unfortunately I'm about to go on leave for 3 weeks so I can't check the unit. I have some documentation, but not a service manual.

When I get back I'll be happy to take a look at my unit and we can compare jumper settings etc.

Have you checked all the supply rails? As you saw in my repair, there's a number of voltage regulators and you would be well advised to track them down and check them.

The supplies voltage look correct. All the voltage on ribbon cable connecting to the front panel are stuck on high. I am checking the drivers(TTL decoders). I see input signals, but outputs are stuck high. Need more digging and probing.

I had to replace one of the front panel driver ICs. They're all common chips as far as I can remember. It shouldn't be too hard to determine if the chips themselves are receiving valid inputs and producing valid outputs. If they're receiving what appear to be valid inputs it may even be worth replacing one of them to see if it makes a difference.

I'm back from my holiday and I'd be happy to assist you in diagnosing the fault.

I did check all the power supply voltages. They are all within limit. I don't see any ringing or dipping in power supplies.

I borrowed a spare working EGG 5210 for a day. I took bunch of pictures of its blue jumpers. Somehow the website refuses to accept the pictures. Is there a limit on image size?

Anyway, I mirrored all the blue jumpers per the working amplifier. It was still the same. The amplifier hanged at power up. Also, the analog and digital meters got stuck at some strange but fixed value.

By probing and comparing the working and non-working 5210, I noticed the i8254 clock generator right next to the main micro-controller 68008 having different clock rate. In the working 5210, about 100ms after power up, the output of clock switched from 4MHz to about 100kHz. While in the non-working 5210, the clock stayed at 4MHz. I traced back to another TTL 74157 right next to the large crystal can. It is supposed to do switching between the two frequencies. That is how far I got before I had to return the loaner unit.

It looked like the bad 5210 68008 cleared its own Power On Reset (POR), but the 74157 clock selector chip got stuck in the pre-POR state. Do you know if there is an RC type of POR circuit for the clock distribution?

This is from working 5210. Hope it can help others in the future.

I know I have documentation about the jumper configuration of one of my lock in amplifiers, I'll check as soon as I can to see if it's for this model.

Would you mind if I transcribe this private chat into a public thread?

Please do turn this into public thread. Thank you.

I've taken a month and a half to do this... sorry.

 

[(*steve*)]

Here is the user manual.

(just for reference)

 

[(*steve*)]

And some high level information about this model

 

[(*steve*)]

And the user manual (including schematics) for an earlier version (5104)

Too big to attach... here

 

[(*steve*)]

There are regulators in the both of the shielded boxes in the 5210 -- have those been checked too? Although I'm not sure they'd make the device lock up.

Presumably "lock up" means the buttons don't do anything? Correct?