running 160 melcor 1731's. power/current draw?

[CJ]

did you try a different pwr supply?

ask the owner if he wants to part this thing out, 

Melcors will fetch 5 grand,

UTC iron you say?  ;D

i bet one side of the supply went bad, if there was hum on both sides, that discrete regulator circuit would probably take care of it,

 

[mjrippe]

Of course PRR is totally correct!  This is the same design used in other RCA/Melcor modules and consoles (BC100).  Cards like the one pictured below have the regulating transistors, others like in the following post are without them and require +/-15v.  Opamps may be labelled RCA but are usually Melcor 1731.  I have heard that some were API 2520 but I have not seen those in person.

 

[mjrippe]

Here is the second "unregulated" board, from my own collection.  Also, check out http://www.preservationsound.com/?p=8177 for more info on the RCA 100 series.

 

[pucho812]

thanks guys for all the help and suggestions.

PRR yes there is a separate bipolar 15VDC supply. The console has 3 X supplies total.

+/-28VDC
+/-15VDC
and +24VDC(logic/relays)

According to the tech for the seller, the 28VDC did the master section. I can only guess he means master section is the card cages?  After going over the schematic, I Would agree that the UOAB cards run off +/-28VDC. But they did not know, they did not have any of the documents at the time. The gear broker did not know there were documents. The buyer who I have been working for this called the previous owner and not the brokerage company and got the documents. I The more I look at the UOAB schematics and console,  I would concur that the UOAB cards run purely off +/-28VDC. If that is  the case then the +/-15VDC must power the eq's and comps.  I must add the flow chart for the console later. Hunting things down is fun...

 

[mjrippe]

OK, to make things even more confusing, the EQ-20 modules you mention are supposed to run off of +24VDC!  Specs attached.

 

[pucho812]

???  Oh boy...
That doesn't look right the to Melcor GME20 schematics I have seen... hmmmm

 

[mjrippe]

???  Oh boy...
That doesn't look right the to Melcor GME20 schematics I have seen... hmmmm

No, you said it had EQ-20 modules.  Totally different units.  The GME-20 specs are attached and they use +/-15VDC.

 

[pucho812]

Ah yes you are correct I did sat eq-20.  I was unaware there was a model eq-20. hmmm

 

[mjrippe]

Yeah, Melcor liked the number "20".  They offered EQ-20, GE-20, GME-20, AE-20, SME-20 equalizers, CL-20 limiters and AML-27 mic pre/line amps!

Sorry about multiple edits - so many similar numbers!

 

[pucho812]

Problem fixed/solved

After some careful testing, the suggestions of several members I am in deep gratitude for I got to the heart of the problem. Based on the original noise that was being heard and some testing that was suggested I was getting some 2 VAC across the -15VDC output.  An inspection of that +/-15VDC power supply yielded a supply that was in dire need of a recap, had rust and over all was in bad shape.  I  procured two single ended supplies and wired them up to act as a bipolar 15VDC supply and noise is all gone. Console is now working and sounds incredible.  Thanks guys as always the collective minds around here make my proud to associate with such amazing people. I am putting this thread to rest and starting a new one containing in depth photos and other great info. Thanks again guys...

 

[mjrippe]

Glad to hear it is resolved!  Can't wait to see/read more

 

[pucho812]

well the bulk of documents we were able to obtain on this beast is the UOAB information which is in the tech documents under RCA. It contains UOAB schematics and some app notes.. 8)  outside of that I have a flow chart. The flow chart will be added shortly as will be some photos. Since the console has no stereo buss or pan pots on each channel  for that matter, I thought about adding some in. Obviously in  keeping the console original, I would have them in  a separate container. You know to not drill up the frame at all. I  For the buss amps  might do a tube thing... Still on the fence with that or I do a doa thing, hmmm decisions decisions