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Yamaha PM-700 - Not working? Help!

Discussion in 'Recording' started by purebloom, Jan 11, 2008.

  1. purebloom

    purebloom Guest

    Hey guys and gals -

    Recently a buddy of mine loaned our band an old 1973 or '74 Yamaha PM-700 12 channel board. He said last time he used it (a year or so ago) it worked fine and it's been in storage since then. We plugged it in and got power (The VU Meters lit up). However, when I hook a mic up to any of the channel inputs (I've tried them all) I can't get sound out. I've tried plugging in headphones and I can hear clicks through the headphones when I change certain settings and when it powers up.

    I see on the back it has a fuse, but other than that I'm not sure why it wouldn't be working unless the entire channel strip crapped out.

    I've looked over the manual and didn't see anything obvious, I have a feeling that it may work and I am just stupidly over looking something. I've been known to do that on occasion.

    Any advice/comments/suggestions would be greatly appreciated as we would love to use this.
  2. moonbaby

    moonbaby Mmmmmm Well-Known Member

    How are you setting the input sensitivity switches on the channels? I used to have a couple of PM700s for local contracting in 77-80. Out of town sound guys were ALWAYS confused by the nomenclature on those selectors and set them BACKWARDS! In other words, they'd see "-50dBm" and think that was the amount of attenuation, when in fact it was really the OPPOSITE. At that setting, the input wanted to see a -50dBm source (like an SM57). SO, they'd be setting the inputs to "0" or "+4", and that was really a LINE LEVEL setting. No gain for a typical mic, capiche? I'd get a call:" Hey man, we don't have any sound!". and I'd have to walk them through that. So be sure that you have the inputs properly set...
    Secondly, make sure that the little level switches on the rear of the mixer, by the XLR outs are properly set to "+4", not "-50". Hmm, on second thought, that wouldn't affect the phones output, I don't believe...

    Also, there are some internal fuses that are on the supply rail to the out- put driver amps, the ones that are by the output transformers. Everything lights up, no audio from the outputs. Adn I believe that the phones output amp is driven POST the output stages (weird). To check THAT, there are a couple of screws under the board, near the front corners, kind of inset. If you remove these, the whole front of the board opens up like the hood of a Chevy, and has latching supports to support it so that you can look around in there. Pretty cool, eh? Try that with a Mackie! Anyway, open up that puppy and, using a flashlight, check all of the fuses in there. I'll bet it's something that simple. If you aren't getting a bad 60HZ hum from crapped-out filter caps, or a bad bridge in the power supply, that is usually all that went wrong with those tanks. Noisey buggers, but they had gobs of headroom and hardly ever die. Good luck!
  3. Davedog

    Davedog Distinguished Member

    I could be ALL WRONG and maybe so.....Moon would know this for sure....Didnt the 700 also have those insert jumpers on the channels and the subs and if they werent in place or a device wasnt plugged in there nothing came through but the meters worked???? Am I screwed up or is it just the MadCow kicking around some???
  4. bent

    bent No Bad Vibes! Well-Known Member

    God, this brings back memories.
    When I first started at the mouse every mix location had a Yamaha!

    Ya know, I might still have one or two of these on my shelves...
  5. moonbaby

    moonbaby Mmmmmm Well-Known Member

    They didn't have inserts on the PM700, that came later with the M912/M1516 line (little brothers to the PM2000). Same deal with the jumpers. The PM700, like the PM1000, was a pretty straight-forward (i.e., no "frills"). Yeah, the M1524 I bought in '82 was the size of a Buick and it had internal jumpers, like the Soundcraft 400 did. Every time I had to move it, I did 3 crosses and a Hail Mary. It was stolen in '85...a Vegas-type act from Canada drove off with my truck full of gear. I remember praying that everyone of those bastards would get a hernia when they tried to move that beast!
  6. purebloom

    purebloom Guest

    I really appreciate the advice and suggestions. Next time I'm over there I'm going to have to open her up and take a look.

    Hopefully it is something simple like an internal fuse. Would love to use the old thing. :)

    Thanks again!
  7. moonbaby

    moonbaby Mmmmmm Well-Known Member

    Let us know how it goes !

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