AMS DMX-15-80 repair , service manual, schematic?

[mrclunk]

We've a very sick AMS DMX 15-80 delay that i'm trying to fix. We think its an early version (ex-bbc) and doesn't have some of the features of the later models.

Initially we thought it was missing cards but now believe it isnt, so its worth fixing.
A schematic would be very useful!

The chaps at AMS have been very helpful offering advice and possible solutions but unfortunately they can't give out the circuit .

Before i can get anywhere i need to replace the power transformer as there's a short on one of the secondaries.

Can anyone tell me the specs required ?
This is an old model with a linear supply, not the switcher model btw.

Also in this DMX the fan is wired straight to the mains via a resistor so i won't need the 150vac secondary.

I think i need 1x 9vac, 2x 18vac and 1x 15vac but that would mean three transformers!
Maybe if i could get a peek at the psu schematic it would all become clear.
Anyway some pictures for the gear freaks.

 

[mrclunk]

psu

 

[mrclunk]

sick processor board, missing the battery. Hopefully the eprom's survived.

 

[radardoug]

David Kulka at Studio  Electronics is the man to talk to, and he has new processor boards.

 

[mrclunk]

Thanks doug,
David is certainly the go to man in the States but we've the AMS tech krew over here, plus i'm hoping to remedy it myself and save the cash.
Worst case i'll get the psu, ribbons and caps etc.. fixed and then send it over to AMS for the tricky processor/ram stuff.

Noticed last night that the fan is broken so it probably slow cooked itself to death.

 

[r2d2]

....i remeber some year ago a my friend wanted to buy a DMX ...
before proceed with the deal he made a phone call to AMS ...
to ask to buy some spare  parts to keep in reserve in case of troubles ...
the anser was : "sorry no longer available" ...  .  :-[

perfect ! ... better no DMX !   

....better use the time to record, mix, etc ...

peace
r2d2

 

[mrclunk]

We've spoken to AMS.
They have  parts and still service them at very reasonable rates, contrary what i've read on other forums.

 

[Walrus]

Yes, that definitely is a very old 15-80!
Schematic that should be OK for the PSU is now in Technical Documents.

That box does seem rather short on boards.

 

[r2d2]

really ?
could you please give me the name of person at ams
you've spoken ?
(Ams uk ? )

i pass it to my friend ...(in case i it more want get a dmx...)

peace
r2d2

We've spoken to AMS.
They have  parts and still service them at very reasonable rates, contrary what i've read on other forums.

 

[mrclunk]

Found out our box is a 15-80S-B (B=Broadcast) Mono input to stereo out.
It just has the delay function without effects, pitch / glitch etc...

There's two 256K RAM boards, each gives a 0.5 sec delay. Not sure if this will give a total of 1sec or a 0.5sec delay per output channel.

Thanks to Walrus for the schematics.

Our psu's is slightly different from the schematic.
There's no centre tap on the 8vac secondary, instead it uses a full wave bridge rectifier.
My mystery secondary that connects to another bridge rectifier ('REC 4' on the pcb overlay but not in the schematic ) goes to a simple 7915 regulator circuit for a -15VDV rail.
However this -15v power rail goes to pins on the DAC cards that aren't connected to anything...

Probably buy a couple of toroids next week and get the psu going then move on to the tricky stuff.
Anyone know how to test RAM chips?