Traynor YSR-1 Question

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by AL30, Jan 24, 2006.

  1. AL30

    AL30 Member

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    After much procrastinating and some help from some people here (thanks Cpokay) I finally got my Traynor YSR-1 running. I got it very cheap because it wasn't working. It had a burnt resistor (complete with a hole in the board) and some other wiring issues. I think I now have it back to spec. Mine is a 1970? model with a choke and reverb transformer. Schematics here;

    http://www.lynx.bc.ca/~jc/traynorSchmArchive.html

    My question is concering the 1K 12W resistor on pin 4 of the power tubes to the filter caps. I played the amp for about an hour and was just checking to see if everything was OK and that resistor was very hot. Is this normal for this amp? I wouldn't think so, as this is where the burnt spot on the board is, but I don't have any experiences with Traynors. I replaced the old resistor with a new 1K 15W.

    I haven't had any time to check voltages, bias (I through in new power tubes), or anything of the sort. The filter caps are original and I have replacements ready to go as soon as I find my solder gun (I just moved and things are a bit scattered). I'll be able to check the rest in the next few days.

    Anyone have any experience with this issue? It seems to be putting off a lot of heat.

    By the way - this thing sounds fantastic - WOW !!

    Thanks

    AL
     
  2. mr coffee

    mr coffee Gold Supporting Member

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    that hole is common... without the quick check to schematic I'd say off the top of my head it's a common screen resistor for both tubes. I usually pull that resitor and install a screen resistors on the tube sockets (one per tube) and never look back...
    if that has a choke it has those lovely yellow mustard caps also that everyone is gagag over..

    great amp!
     
  3. bob-i

    bob-i Member

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    That resistor is the screen resistor, since these typically have 400V or so across them I've never touched one so I don't know if they get hot or not. My guess is YES they get hot.

    If you put a 15 watt resistor there, that should be fine. I've seen many amps use 2 Watt resistors in this location. This is a common failure part though.

    Once you get your meter out, measure the voltage drop across it then use watts law to see how much power dissipation you have. If it's near 15 watts you could have something else wrong.

    Use this calculator, saves lots of manual calculations
    http://ourworld.compuserve.com/homepages/Bill_Bowden/ohmslaw.htm

    BTW, don't use a soldering GUN on these repairs. Get a 30watt or so iron. A gun will apply way too much heat.
     
  4. donnyjaguar

    donnyjaguar Member

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    A couple of things here. According to the schematic, the shared Sgrid resistor should be 470R, not 1k. That tells me that the amplifier has been modified (or repaired) and is not a stock circuit. (My Traynor head is a 470R 2W). During normal operation IIRC, the Sgrid should draw about 5-7mA, so 2 tubes will make that 10-14mA. For a 1k resistor, 14mA of current will result in about 1/4W of power. Not enough to warm up a 12W power resistor to any extent. If I had to guess, I'd say the amplifier is running very hot on the bias and that a repair has to be made to that part of the circuit. I would definitely check this before using it again as a damaged output (or power) tranny is expensive and awkward to replace.

    The date of the amplifier can be determined by the first 3 digits of the serial number. The first digit is the year and the next 2 are the month. So 711 would be 1977, November for example.

    Mine sounds good too, and its a unique tone. The output transformer is rather small as it is a later unit, but the volume is there.

    DJ
     
  5. AL30

    AL30 Member

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    Thanks very much for all the replys. I'm going to try and get to this tonight.

    A few things:

    That's an awfully big resistor. Where would you put two of them? One side is to the grid the other to the filter caps.

    Oh yeah. It's loaded with mustard caps. Not bad for $60 huh? I could sell the caps for more than that. And NO I won't...:moon

    The only thing I would be using the gun for was for getting the filter caps off the chassis - the grounds are soldered directly on the chassis. I can't get my iron to heat enough to even put a dent in the solder.

    You looked at the later schematic without the choke or reverb transformer. It has a 470 10W. It's kind of confusing - I've done it a million times - even during the re-wire. I had both schems out just to make sure and I looked at the wrong schem on a few occassions.

    Thanks for that. I'll check for some drifted components. Would it be a good idea to add a bias pot to the circuit?

    Yeah, definitely unique. Quite different sound from my other amps. I like it - plenty of thump without the mud.

    AL
     
  6. bob-i

    bob-i Member

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    You can put them right on the tube sockets. Put a small terminal strip on the bolt that holds the tube sockets on.
     
  7. AL30

    AL30 Member

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    Hey now... that's a good idea. Thanks for the insight. I never would've thought of that.

    AL
     
  8. bob-i

    bob-i Member

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    Me neither. I stole that from Leo Fender. :NUTS
     

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