PM1000 with Altec Meter Bridge

bassist001 · Post by **bassist001** » Mon Apr 21, 2014 12:36 pm

So, I recently acquired a new Pm1000. This particular one is pretty rad, cause it has a full 32 channel Altec meter bridge with outputs on each channel also. Anyways, there is one issue. The guy that I bought it from, bought it from a company that went out of business. So... No info. But after booting it up and not getting any action from the meter bridge. I opened it up and realized that the meter bridge needs its own power supply. But, since the whole thing looks really custom. There are no model numbers printed on anything and I can't find info. I need to find what voltages this thing runs off, and what to know if anyone know any info on this thing. Thanks!

http://s1313.photobucket.com/user/Aaron_Knott/library/

The Scum · Post by **The Scum** » Mon Apr 21, 2014 12:55 pm

Can you pull it apart enough that we can read the markings on the chips?

bassist001 · Post by **bassist001** » Mon Apr 21, 2014 1:02 pm

That's my next step that I'm gonna work on later tonight (I didn't have a full set of tools at the studio. But I'll post that info asap

bassist001 · Post by **bassist001** » Mon Apr 21, 2014 5:23 pm

Ok, looks like it has 2 - LM3915N and 1 - LM348N Chip per channel. I found there to be more notations on the front side of the board. Looks like it's wanting -12v, +12v and +5v. +5v is for the LEDs and the other looks like its for the chips. Now I'm no expert on ICs. So, I have a few concerns.

1. Is there a stock power supply that anyones knows of that supplies -/+ 12v and +5v?
2. What's the best way to calculate how many amps of power I will need to supply 32 channels of that mix?
3. Do these opamps sound ok? Cause that's what the direct outs are connected though. If they don't sound great I'll mod the thing with actual DO transformers. But thought I'd ask anyways.

Jim Williams · Post by **Jim Williams** » Tue Apr 22, 2014 8:30 am

Power One makes a three section power supply with + - 12 and + 5 volts.

bassist001 · Post by **bassist001** » Tue Apr 22, 2014 10:04 am

Perfect! Thank you!

The Scum · Post by **The Scum** » Wed Apr 23, 2014 3:42 pm

LM348N's are trash. Four 741's on a chip.

http://www.ti.com/lit/ds/symlink/lm348.pdf

Noisy, poor slew performance. Perhaps in keeping with the retro 70's-style design of the desk overall, but totally contradictory to the strong class-A foundation of the PM1000.

Jim Williams · Post by **Jim Williams** » Thu Apr 24, 2014 8:29 am

LM348's are fine for a meter circuit.

Injured Ear · Post by **Injured Ear** » Fri Apr 25, 2014 5:34 pm

Jim Williams wrote:LM348's are fine for a meter circuit.

My meters sound awful!

The Scum · Post by **The Scum** » Fri Apr 25, 2014 11:19 pm

My meters sound awful!

That's because you're tying to listen with your eyes.

To the OP: If, as you stated, the direct outs do indeed go through the 348's, ditch them. If they're just being used as utility amps for the meters, they're fine.

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PM1000 with Altec Meter Bridge

PM1000 with Altec Meter Bridge

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