Yamaha A-1 Repair and restore: beyond Deoxit

Discussion in 'Yamaha' started by Dadbeh, Jul 2, 2018.

  1. clinic-audio

    clinic-audio all on YAMAHA untill 1990

    Messages:
    1,968
    Location:
    France
    Yes ,we can help if you are very carefull
    Always discharge electrolytic capacitors with a resistor NEVER , NEVER with a screw driver like you can see in this video
    Here again in this movie we can see all you should not do !
    AK is a reliable source , follow experienced members , not the web !
    once you did what I recommend you in my last post , come back to us with report

    Who will you trust ?
    The web or a guy who do repair on all high quality equipments over 40 years with many worldwide customers ?
     
    Dadbeh likes this.

     

    Please register to disable this ad.

  2. Dadbeh

    Dadbeh Active Member

    Messages:
    101
    oh i had no doubt thast the video was wonky, i posted it for a laugh (iu thought it was funny that the guy thought that he should spread his wisdom lol). the problem was that when i asked before, ya'll told me to discharge but not how and i kinda rushed over it but connecting a wire to the ground terminal and connecting the other end to the metal legs of my equipment stand and not worry about it anymore until last night. so no doubt that my rushing was the source of error. ofcourse i also made the other error that plugged the unit in to test the lights and forgot to unplug and got a spark when i tried to unscrew the transistor. so that was a separate mistake but the problem with the caps holding a lot of charge is pretty egregious.
     
    Last edited: Jul 10, 2018 at 9:18 AM
  3. Nashou66

    Nashou66 AK Subscriber Subscriber

    Messages:
    1,480
    Location:
    West Seneca NY
    Yes use a large watt resistor maybe like 500 ohm to 1000 ohm.

    I did the same thing you did and blew the output. and in the same fashion , after I discovered the emitter resistor was bad.

    Dont get discouraged. It happens to all of us. Just learn from your mistakes and get better with practice.

    Athanasios
     
    Dadbeh likes this.
  4. Dadbeh

    Dadbeh Active Member

    Messages:
    101
    actually i got so upset with myself exactly because you mentioned it just before i did it hahaha. i was got so frustratyed with myself because i could see that you that you warned me about it like 4 posts above it. well what can i say? we live and we learn.
     
  5. zaibatsu

    zaibatsu Well-Known Member

    Messages:
    573
    I just skimmed through the whole thread and to add some things which may not have been covered:
    • The capacitors you want to discharge with the 500-1000Ω resistor Nash suggested are the main filter caps (largest ones), do this every time before working on the amp (obviously switched off first) and check across the terminals with your meter in DC V to make sure they're low once done.
    • Most of the Nichicon lineup is good, a safe bet is using either the PW or HE series (UPW / UHE) as they are 105*C rated. It is safe (even beneficial) to go up in voltage rating over stock, but measure the diameter of stock part and check diameter of replacement part to make sure they are similar / will fit. Keep capacitance value same. Note (or mark on board) the polarity of caps you remove, because sometimes there are errors in screenprinting.
    • Did you re-check your output transistors? Because they look to be alive from your previous test.
    • When you've replaced any bad parts and are ready to do live testing of voltages, first it's good to build yourself a dim bulb tester, as it will save your amp if you have made a mistake that causes the output transistors to short (the bulb will glow bright instead). A 60-100W incandescent (old style, not energy saving) bulb will do. You need no load connected for this to work (no 70W resistors, no speakers). You can also have this connected when testing voltages which avionic might ask you to do.
    • Generally if the bulb dims + stays dim and the relay clicks the amp has no major problems, but there may still be minor ones.
    • Get some mini-grabber leads for your multimeter (you press the top and a little spring-loaded hook comes out) so you can clip to parts without shorting before powering up the amp to read the voltages (incl. setting bias / dc offset). Poking around in a live amp with regular tip leads is asking for trouble.
    I'm pretty sure most people made the same mistakes you have at some point, don't let it get you down, just try not to repeat them. You do have to be really patient working on these things, work slowly and double check all work before powering up the amp. A small mistake due to rushing can cause many days of extra work.

    Best wishes!
     
    Nashou66 and Dadbeh like this.
  6. Dadbeh

    Dadbeh Active Member

    Messages:
    101

     

    Please register to disable this ad.

  7. clinic-audio

    clinic-audio all on YAMAHA untill 1990

    Messages:
    1,968
    Location:
    France
    10 OHM / 100W will be fair enough
     
  8. Nashou66

    Nashou66 AK Subscriber Subscriber

    Messages:
    1,480
    Location:
    West Seneca NY

    How about 8 ohm 100 watt so he can also use it as a dummy load?

    Nashou
     
  9. clinic-audio

    clinic-audio all on YAMAHA untill 1990

    Messages:
    1,968
    Location:
    France
    Yes , it is fine but you need 2 , one for each speaker
     
  10. amr2

    amr2 Active Member

    Messages:
    492
    I use 470 / 15W across the terminals and wait a couple of seconds, always checking the voltage with the meter.
     
  11. Dadbeh

    Dadbeh Active Member

    Messages:
    101
    Thanks guys pair 8 ohm, 100 watt resistors ordered. Even though im too impatient about putting that emitter resistor , which arrived today, in and firing it up, I am going to be forcing myself to be disciplined and I'm not gonna touch it until I have the resistors and the mini grabbers. I promised myself no more getting shocked myself or zapping any elements lol
     

     

    Please register to disable this ad.

  12. Dadbeh

    Dadbeh Active Member

    Messages:
    101
    I shocked myself a good six or seven times doing this. Lol.
     
  13. Mrvintage

    Mrvintage New Member

    Messages:
    46
    Location:
    Parry Sound Ontario Canada
    Good morning fellow AK’rs. I’ve been into audio since I was 13 at 15 in 1978 I started a DJ business. That’s when I bought my first Yami it was a P 2200. It was in my rack until 3 years ago when I got out of the business. I’ve since bought 2 more P 2200’s and one amp came with 2 complete sets of output transistors neatly packed on cardboard to protect contacts. I need a few more pieces to help in completing my vintage system rebuild. Pic slow ’ I need a CD player looking at Tascam 503 and replace my old Sony reel to reel with a newer version not shown. My question is. Does anyone know a good yami guy in Ontario Canada that can give my beloved beauity’s some love’n ? I will be bi amping a set of JBL 3648 cinemas and matching 2446H driver and with the matching JBL 8340 surrounds. Pic of speakers is when I first brought them home. I assembled horn driver at that time to get prospective of size. I’m in the process of putting and Jatoba veneer on the speakers in the coming weeks
    Shane
     

    Attached Files:

    Last edited: Jul 13, 2018 at 9:00 AM
  14. avionic

    avionic " Black Knights " Subscriber

    Messages:
    41,161
    Location:
    Fort Dodge, Iowa
    What does this have to do with a Yamaha A-1 ? Start a new thread about your 2200.:thumbsup: Look up AK'r Vint age..he may be able to help you out.
     

Share This Page