ADM RM 1083 - Schematics / Direct outs

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beezer4

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Hi all,
I snagged an ADM RM 1083 portable mixer off eBay last week. It was listed as not powering on, but turns out it was just the LED that was nonfunctional. It's basically an 8 into 2 mixer with an aux send, stereo return and monitoring section. It's a pretty rad little mixer. Sifam VU meters. Transformer balanced inputs and outputs. The input transformers resemble the UTC ouncers, but I think they are ADM custom. I know ADM leverages the UTCs in much of their equipment. Looks like it was built in 1987. The original advertisement stated the unit has direct outs. This specific unit does not, so I'm hoping to find a schematic or someone who might have knowledge on these mixers. I'd also like the recap the power supply, so it'd be cool to find the power supply schematics to see if I can make any updates.

I attached some pics as well.

IMG_2027.jpegIMG_2029.jpegIMG_2032.jpegIMG_2028.jpegIMG_2039.jpegIMG_2030.jpeg
 

TwentyTrees

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Nice find! And a good score with the power LED too.

I've a lot of time for ADM gear, I've a couple of EQs that I really love. Brian Roth is very knowledgeable about ADM, if anyone has the schematics for this piece it would be him I imagine.
 

Brian Roth

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That's a new one for me! ADM made lots of items I never saw. My experience was with the large studio/radio-TV consoles. As for direct outs, can you snap a pix of the rear of the unit?

Bri
 

beezer4

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That's a new one for me! ADM made lots of items I never saw. My experience was with the large studio/radio-TV consoles. As for direct outs, can you snap a pix of the rear of the unit?

Bri
Here ya go. There is a large external I/O connector that I believe is for linking another mixer, but I need to trace that down.
IMG_2041.jpeg
 

Brian Roth

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If a quality company such as ADM said it has direct outs, it DOES! <g> They are buried into that rear panel multi-pin connector along with "who knows??" other connections.

Sidebar....I suspect the markings you are seeing for the small "Ouncer sized" transformers is an external mu metal shield. Inside that is an actual Ouncer O-1 or whatever. For the older modules, I've had questions like "what is an O-17??" O-17 was an optional can that shielded the real xfmr, and folks mistook as the actual part number for the xfmr.. Perhaps in later years of production, Bob Bloom sourced a different mu metal can source....or maybe not <g>. He may have also sourced a clone for the older UTC iron. Wish I had all the answers!

Most of ADM's gear was sold into the television (and high end radio station) markets. It had to run 24/7/365 and ignore RF interference from a co-located 1000000000000000 Watt <G!!> transmitter in the same building. ADM built incredibly well-designed gear in the USA when "men were men and the sheep were nervous." Ahem.....Sorry about that coarse bit of humor...<g>.

Wish I had more info to supply about that handsome little rack mounted unit! Let me know what you find.

Bri
 

Brian Roth

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As a followup, ADM supplied very detailed manuals, schematics, parts lists when the equipment was shipped. I have a hunch about why so much of that info is difficult to find in year 2021. I guess that all that info went to a dumpster along with the actual desks during the TV station conversions from analog to digital. Years go, I literally "stood between the back door and the dumpster" as an ADM was being disposed...along with the docs. Did my best to save it all, and I ended up saving the modules. Resold those on ebay. I kept the docs (such as they were....tons of those were lost after decades).

Bri
 
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Youngwhisk

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How many pins does that external I/O connector have?
A signal fed into one of the inputs should be able to be found on that connector. If you find 8 individual output signals, that should be the direct outs shouldn't it? Not sure if it is balanced or not.

Found this. You have probably seen it. (edit: I didn't realize this was in the brochure above)
From the manufacturer:
The ADM RM1083 is a self-contained, rack -mountable mixer designed for both mobile and fixed installations. It offers the most needed audio console features not generally found in a portable audio mixer, such as eight inputs that are switchable between microphone and line source, transformer coupling, phase reversal, 30 db of gain adjustment and a high pass filter. A three band equalizer with carefully chosen frequencies optimizes your audio performance for either a mobile or fixed application.

Designed with stereo in mind, the RM1083 provides panning on each input with in/out switching, a line up oscillator bus assignment, eight direct outputs, transformer coupled main and auxiliary outputs and a host of other features make the RM1038 the most versatile rack - mounted mixer available today.

Built with traditional ADM quality, the RM1083 will handle the roughest mobile or fixed use and still deliver the top performance the commercial broadcaster has learned to expect from ADM.
 
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Whoops

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It seems a really nice mixer and ADM stuff was really good.
I hope you find documentation and schematics although if it works well and you just want to Re-CAP the PSU you surely dont need schematics for that that, replacing the Electrolytic capacitors that are already there should be pretty easy.

Have fun with the unit, hope you were able to get it for a good price
 

beezer4

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After doing some digging today, it looks like the external I/O is a DB37 connector with 12 lines ran inside the mixer. They all seem to be going to the Master L, Master R and Monitor cards. The input modules don't have independent outputs to the master channels, they all connect together via a ribbon cable and that ribbon cable gives a Left, Right and Aux signal to the L/R master. I hope that makes sense.

I'm guessing the external I/O is 8 additional inputs to the master, stere out and monitor out.
 

mjrippe

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Yeah, I didn't want to be a bummer, but that panel on the back is probably where the direct outs would go :(
But I bet you can figure out a way to add them.
 

beezer4

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Quick power cap question. The power supply generates +-40VDC and then each card has it's own pair of regulators to bring it down to +-20VDC. On the main supply the decoupling electrolytic caps are 2200uf 50V - is it safe or good practice to increase those to 2200uf 63v (which is more readily available at Mouse)?
 

Whoops

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On the main supply the decoupling electrolytic caps are 2200uf 50V - is it safe or good practice to increase those to 2200uf 63v (which is more readily available at Mouse)?

Yes, you can always go for an higher voltage rated cap, just never go lower.
I would recommend you Panasonic Lytic caps rated at 105 degrees
 

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