Need help from CP200 experts.

[Mikael Christensen]

I have two Dolby CP200 units, which displays almost the same problems:
There's no function on the fader.
Using Non-Sync input, there's no sound.
When using optical input, low level sound is running through the unit, with no fader function. The L+R meter are active.
Any idea what's wrong ?

[Gordon McLeod]

One thing that comes to mind is it looking for a remote fader box?

[Steve Guttag]

Is the "Activate This Fader" LED/button on the front panel lighted? If not, you likely have the Auditorium fader switch up and/or on the Fader/Mute card you have the remote fader suitcase link in the remote enabled position.



CAT157.jpg

[Mikael Christensen]

One thing that comes to mind is it looking for a remote fader box?

Thanks for the tip, but I need to use the fader on the unit.

[Mikael Christensen]

Is the "Activate This Fader" LED/button on the front panel lighted? If not, you likely have the Auditorium fader switch up and/or on the Fader/Mute card you have the remote fader suitcase link in the remote enabled position.

No it is not lighted, and the switch + suitcase is in the right position. I have a older card, when it is plugged in the LED is on, but no sound.
The old card also have some modification on it ???

[Sam Chavez]

I would venture a guess that the special 1 or 2 card links have been cut to allow the installation of an SRA5 adaptor. If the SRA5 is no longer in the circuit, the signal stops there. At least that is what I recall from way back then.

Also exercise the Cat. 141 card slots. The 23 way connectors get pretty flakey sitting around unused.

[Steve Guttag]

Sam, he stated that the Activate This Fader button on the front panel is not lighted. If that isn't lit (including if the LED is bad), there won't be any sound as that LED indicates the VCA source. I don't have one of my CP200 schematics around (and I'd probably have to check an early issue to see one with that early of a CAT157) and I definitely haven't worked with that version of the CAT157 and I've worked with a 1st generation CP200 (Empire Strikes Back) that did have CAT204 remotes. However, I'm reasonably certain that it had the Auditorium Fader switch...which is missing on the picture above. I do recall reading that on the early units, if you didn't have the remote faders that there were additional diodes on the motherboard that had to be present/cut (again, this is really old info/memory).

Non-Sync does not use the Lt/Rt lines on a CP200. It does an end-run around the Special 1 and 2 and comes in on the second CAT 141. I'd sooner suspect ribbon cables not being properly inserted or missing voltages on one of the units due to power connectors/cables not being right and in the right order. for loss of audio

When you press the Activate This Fader button on the front panel, does the LED come on then? If so, do you have sound then (I'd use Format 66, dolby-tone) as my test while checking on the fader mystery. But, ...no LED, no sound.

[Sam Chavez]

It's too long ago to truly concentrate but I agree it might be something to do with the ribbon cables or ribbon cable headers. I do recall there was fader A thru D and not all fader references are alike. One of them was hanging out there and easier to accidentally operate.

Overall, my experience is that often the reported problem or observation as stated turns out to be a red herring and the real problem is a layer or two down.

Plus, I don't listen so good.

[Mikael Christensen]

Thanks for the help, it is much appreciated :-)
But I found the fault with the fader, I am an idiot !
Had no power cable from psu to units, so I made one. but had forgotten the extra +24v connection.
Now fader is working, and there is sound :-)

[Sam Chavez]

Well done! You re-examined your work and found the problem.

Welcome to state of the art 1978 audio! About where I came in.