1. Time for some upgrades in server hardware and software to enhance security and take AK to the next level. Please contribute what you can to sales@audiokarma.org at PayPal.com - Thanks from the AK Team
    Dismiss Notice

SPEC-4 replacement part question

Discussion in 'Pioneer Audio' started by mikebw, Nov 5, 2018.

  1. mikebw

    mikebw Member

    Messages:
    58
    I first posted about this a few years ago (yikes 10! :yikes:) but never made any progress. Sometimes life just happens...

    To the point- I (still) have a SPEC-4 that goes into protect mode after turning it on. In a very old message to EW it was suggested that I might do the following to replace the original Q13, #2SC1384, and Q7, #2SD381 on each driver board.

    "I'd replace the 2SC1384 with a Zetex ZTX1056A, and the 2SD381 with an On-Semi MJE15032."
    However it seems those are no longer available either. After some digging it looks like KSC2690AYS and MJE15032G are suggested replacements. Can anyone please confirm that those are the correct current replacement parts before I place an order?

    The 2690 appears to be on backorder, but as you might imagine I am not in a huge rush to do this.

    There also seems to be some interesting current discussions here on replacing relays; is that a concern for the SPEC-4 as well?
     

     

    Please register to disable this ad.

  2. sawdust

    sawdust Solid walnut covers all my gear Subscriber

    Messages:
    339
    Location:
    Michigan
    that is what I used Q13, KSC2690AYS and Q7, MJE15032G
     
    mikebw likes this.
  3. embrown057

    embrown057 Active Member

    Messages:
    178
    Location:
    Apollo Beach,FL
    I would suggest you start fresh here. I just looked at the schematic SPEC-4 and q7 and q13 are 2sc945A. If your looking for an alternative to the 2690 just use the Ksc3503/A1381.
     
  4. mikebw

    mikebw Member

    Messages:
    58
    I appreciate the feedback, but where are you seeing that information? It seems to be inconsistent with my prior findings.
     
  5. slimecity

    slimecity Super Member

    Messages:
    2,986
    Location:
    New Zealand
    The MJE15032G is just the currently available version of the MJE15032 that EW cited. These are definitely still available - its the same transistor.
     
  6. mikebw

    mikebw Member

    Messages:
    58
    OK I see that those are the same thing now, thanks.
     
    slimecity likes this.

     

    Please register to disable this ad.

  7. embrown057

    embrown057 Active Member

    Messages:
    178
    Location:
    Apollo Beach,FL
    Ok I see your error. You said the "driver board". It's NOT the driver board your referring to it's the "Meter Board". Q7=D381- Q13-1384 are correct.
     
    mikebw likes this.
  8. mikebw

    mikebw Member

    Messages:
    58
    Whoops, yeah totally my mistake there. :confused: Like I said it's been a while since I've really thought about this.

    Any other likely bad parts to consider adding to my order at this time? $8 shipping for $2 in parts just feels wrong, although I will be getting a few extras.
     
  9. slimecity

    slimecity Super Member

    Messages:
    2,986
    Location:
    New Zealand
    If you mean speaker relays - you will know when to replace these if you get a certain type of sound dropout - usually in one channel - one channel will drop by quite a bit, however the problem goes away if you pump the volume up a bit. Its an intermittent fault caused by worn internal relay contacts
     
  10. LesE

    LesE 110284 Subscriber

    Messages:
    851
    Location:
    Ontario, Canada
    Toshiba TTC004B is a potential alternative to the KSC2690A.
     
  11. embrown057

    embrown057 Active Member

    Messages:
    178
    Location:
    Apollo Beach,FL
    I would suggest you just slow down on ordering anything till you decide weather you want to do this right or not. If you want to continually get back into this unit then your on the way. I've contributed some picture and there is a fair amount of information on the SPEC-4 rebuild. Get it wrong and she'll keep giving you sleepless nights. Do it right and you'll have an amp that will last for another 20 years. There are many parts that need to be replaced and yes the relays also. Although the SPEC 4 dose not have as much power as the 2 it's a better sounding amp in my option. You did not say if the BJT's your considering replacing were bad and why. What voltages did you have, I'm assuming no data at this time. Glen is one of the best technicians I had the privilege to know and see his work. That being said he just gave you a quick suggestion where to start.
     

     

    Please register to disable this ad.

  12. kevzep

    kevzep Its all about the Music Subscriber

    Not quite, the G variant is Lead free, they are phasing out semiconductors with lead nowadays.
     
    slimecity likes this.
  13. mikebw

    mikebw Member

    Messages:
    58
    I agree. I do have some experience with soldering and recapping boards, but am not well versed in diagnosing on the component level. I have no data and I went to Glenn looking only for his best guess based on his experience with these units, and the current condition of mine going into protection, so I am not expecting that to be a 100% complete and accurate diagnosis. I would like to eventually recap and get it back to a well performing amp, but thought his suggestion could be just a good starting point.

    Right now I am viewing this a longer term project that I do a bit at a time, hopefully learning about the whole process along the way.

    With regards to ordering parts, if there is a BOM for all the likely bad parts I could order now I am in favor of that because it would allow me to proceed when I have the time and not be stuck waiting for a delivery or searching for a replacement for a recently obsoleted part.
     
  14. embrown057

    embrown057 Active Member

    Messages:
    178
    Location:
    Apollo Beach,FL
    You should take some time and go through the SPEC postings here on AK. Rebuild meter board, amp boards then soft start relay(s). None of it difficult just time consuming. There are a few examples of replacing the relay on the amp board. Some examples are less elegant, time taken and you can make that relay look like it was always meant to be there. As far as the BOM not sure if anyone every did one for the 4, mine consist mostly of NOS parts. Just look up the original numbers and see if the sub suggested meets the original spec. If you run into a number your not sure about check with one of us here. I see some sub's suggested here that fall short on Ft or Cob, may not be critical on some jobs but always cross check your data. Check twice solder once.
     
  15. miklemke

    miklemke AK Subscriber Subscriber

    Messages:
    862
    Here are some lists that should help you with your Spec 4. I compiled them from others posts to Audio Karma. Thanks should go to those who did all the heavy lifting, unfortunately I didn't copy their names.

    I've repaired several non-functioning Spec 4's. They all had various problems. My approach was to take a schematic and test the individual components and mark them either good (green) or bad (red) on the schematic. Unlike the Spec 2's that I repaired, the Spec 4's all had a lot of destroyed components. On the marked-up schematic it was interesting to follow the path of destruction.

    The Spec 4 is a very nice sounding amp. It's worth repairing.

    Good Luck!!!
    Spec 4 Repair.
    Spec 4 Parts List.pdf
    pdf
     

    Attached Files:

  16. mikebw

    mikebw Member

    Messages:
    58
    Thanks very much! I'll be sure to check these out.
     

     

    Please register to disable this ad.

Share This Page