Larid 1450 Character Generator - No Ouput
 

Hi all,

I've come into a Laird 1450 Character Generator with a post-it note on it that says "WORKS - to the best of my knowledge". Unfortunately, I can't get anything from the encoder, preview, or program outputs.

These seem to be very very uncommon, and I'm not expecting anyone to hold my hand through troubleshooting, but I wanted to leave my diagnostics here in case they jump out at someone as characteristic of a certain issue. I have the full Installation and Operation Manual, which comes with schematics, but I am unable to find a service manual exists for this. The manual I have does not provide any test points, diagnostic codes, etc., but the fact that it includes many pages of schematics for the cards makes me worry there isn't actually a proper service manual for it. When looking inside, the unit is clearly designed to be extremely serviceable, as all the cards are easily swappable, all the ICs are in sockets, the chassis is very simple to disassemble, etc. so I would assume (hope) that there must be some more documentation out in the world somewhere. Anyway.

What I've tried:

Following instructions in the binder for pre-checkout bench testing, I've patched the encoder input into the encoder output, then hooked up the PRV OUT to a BW monitor (PVM-411), and the PRG OUT to a color monitor (PVM-9L2). Upon powering on the unit, the power LED and fans come on, I get a flicker on-screen, and no sync on either monitor. They do not react to any input from the connected keyboard. The only sign of life from the keyboard is that the "caps lock" light will toggle when pressed. There are no other noises, funny smells, or anything of the sort after being powered on.

I also tried to feed it a valid signal on the program or encoder inputs to see if it could just pass them straight through, but got nothing. I then hooked up the preview and program outputs to my scope to take a look.

What the Scope Shows:

When powering on, the Laird will immediately drop the voltage on the preview / program outputs to -1.7V, then ramp up over a second or two to settle between -320mV and -380mV.

I have opened the unit up and blown it out a bit, and removed each board to inspect it visually. I do not see any obviously damaged components or leaky caps (barely any electrolytics aside from the power supply).

Is there any hope of doing any work on this unit without a proper service manual? Physically, it is in fantastic shape, and allegedly pulled from a working environment, so it kills me to see it sit like this. If anyone has any ideas on where to even start tracking down a service manual, please let me know.

I can post photographs of the unit and/or scans of the documentation if needed, as these don't seem to even exist on the Internet. If you're curious, you can find a bit of info on page 9 of this archived catalog:
https://www.worldradiohistory.com/Ar...rt-1987-09.pdf

Thanks all for any advice.