This could be dangerous...

Discussion in 'Amp Tech Center' started by JSMac, Aug 5, 2021.

  1. JSMac

    JSMac Tele-Holic

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    ...if you didn't know what you were looking at.

    There's 311vdc at that transformer. I guess it's not really a problem with the partial back panel installed, but still. I've seen old radios set up like that but never a guitar amp. How common was that?

    002.JPG
    003.JPG
     
  2. Deeve

    Deeve Poster Extraordinaire Silver Supporter

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    isn't that called field-coil speaker?
     
  3. wabashslim

    wabashslim Friend of Leo's

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    No, that's just the OT. A field coil speaker has 4 wires; 2 for the voice coil & two for the, you know, field coil, which also serves as the power supply choke and co-incidentally a power interlock so the thing won't be run without the speaker. There's a plug on the wire with two larger pins for polarity.
     
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  4. Zoso420

    Zoso420 Tele-Meister

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    One way to get the OT away from the
    PT
     
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  5. dsutton24

    dsutton24 Doctor of Teleocity Ad Free Member

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    Looks like you've got a two conductor power cord on that thing. That was common.
     
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  6. JSMac

    JSMac Tele-Holic

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    It is fused but I intend to put a three prong cord on it. Looks like the filter caps have been replaced but that’s about it.
     
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  7. Wally

    Wally Telefied Ad Free Member

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    That bare fuse on the bottom of the chassis situation would be changed if I were going to work on it. Is this a home brew or does it have a
    Manufacturer name on it? It is a PTP amp for the most part, is it not?
     
  8. JSMac

    JSMac Tele-Holic

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    What is PTP?

    The badge on the front says Tempo. I can't find any info on this particular amp but some reference to some tempo solid state amps. Maybe affiliated with Univox. 004.JPG 005.JPG
     
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  9. JSMac

    JSMac Tele-Holic

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    There is a Schematic on the back panel.

    006.JPG
     
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  10. tubedude

    tubedude Tele-Meister

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    It's a darwinian puzzle.
     
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  11. Jon Snell

    Jon Snell Tele-Holic

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    Reminds me of that song, "The back's off the telly and the wires are live ... don't touch it", just before that puff of smoke from burnt fingers.
    That is not the primary reason to fit a back panel, it was for the increase in tone.
    It only becomes dangerous if people poke their fingers in it when it is running.
     
  12. Wally

    Wally Telefied Ad Free Member

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    PTP…point to point….no circuit board. I think I see a couple of terminal strips, but I see a lot of PTP connections.
    Interesting amp.
     
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  13. JSMac

    JSMac Tele-Holic

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    Yes, PTP wiring. It’s a pretty nice sounding amp, other than some AC noise. It’s bright and chimey and pretty clean. Not much dirt when cranked and not very loud. The tremolo is as nice as I’ve heard.
     
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  14. Wally

    Wally Telefied Ad Free Member

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    JSMac, after you get that recapped and serviced; try this. Use another instrument cable to jumper the two unused inputs. This will decrease the resistance on the input signal and give the circuit a boost.
     
  15. Paul G.

    Paul G. Friend of Leo's

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    Back to original question, it was very common to mount the output transformer on a speaker frame. We also had Lawn Darts, single circuit drum brakes, smoking in hospitals...
     
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  16. Wally

    Wally Telefied Ad Free Member

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    In reality, that frame mounted OT presents no more danger than does any other speaker lead connection. The only speakers that have some added safety there are the spring tension connectors as used on EVs with the insulated caps that one pushes down to insert the speaker wire. I have never thought about touching those connections, though.
    That fuse on the underside has live wall voltage.
    One of the more dangerous amps I have been around was a Univox. I forgot that there was a section of live circuit that was bare on the underside of the chassis. I reached under there while holding my guitar, which was plugged into the amp, to jiggle a tube to see if it was the source of some noise. Lol….I touched that circuit. My butt went straight up about a foot off of the chair in which I was seated! DO NOT REACH UNDER A UNIVOX OR THIS AMP WHILE IT IS LIVE!
     
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  17. Telekarster

    Telekarster Friend of Leo's Gold Supporter

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    Hey Wally, any chance this amp has the "death cap" situation in it?

    EDIT: Didn't see your recent post... I'm presuming it does then?
     
  18. zook

    zook Friend of Leo's

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    Strange schematic annotated.jpg
     
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  19. Telekarster

    Telekarster Friend of Leo's Gold Supporter

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    Ahhh..... and there we have it....
     
  20. JSMac

    JSMac Tele-Holic

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    I did see the death cap on the schematic and will be removing that as well as replacing the fuse holder and adding a three prong power cord.
     
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