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Pioneer SPEC 2 restoration help

Discussion in 'Pioneer Audio' started by slipstream55, Feb 10, 2008.

  1. slipstream55

    slipstream55 Active Member

    Messages:
    236
    Location:
    Gilbert, Arizona
    Good Morning, all. I'm finally getting to restore a SPEC 2 I bought in 2006. It was purchased at a pawn shop in Norfolk, VA. It was demonstrated in "working condition" to me before I walked out of the door with it. That is about all I can say for it. The front face and handles are in showable condition. There is some slight, spotty corrosion (rust, I guess) on the metal sides , top and bottom so it will need some paint work and the AC power cord is a little on the stiff side. I am using my "dim bulb" tester to slowly apply power to it, in part, to reform the caps and to make sure that there are no serious electrical problems. I am using 25, 40, 60, 75, 100, and 150 watt bulbs. I have just started the 60 watt bulb and so far so good I think but I do have a few questions regarding things that happened during the 25 watt and 40 watt bulb power on. Symptoms are below:

    25 watt bulb: The SPEC "chittered" for about 3 seconds then stopped. The 25 watt bulb surged, dimmed, surged again, then dimmed as normal and stayed that way during the 1-1/2 hour conditioning period. Meters lit up and the RH meter movement fluctuated slightly for a minute or so then went back to zero. I didn't see the "protection" indicator light up but I wasn't paying attention, either (my bad).

    40 watt bulb: No "chittering" this time, no meter fluctuation that I saw but the "protection" indicator cycled on/off approximately every 3 seconds during the 1-3/4 hour conditioning period. 40 watt bulb surged then dimmed and stayed that way during the test period.

    60 watt bulb: Started this moring with 1 to 2 second chittering. "Protection" indicator is cycling on/off once a second. 60 watt bulb surged then dimmed as normal. Since this test is still under way, I can't give a time period of test though it will be for at least an hour.

    I suspect the "protection" indicator is cycling on/off because of the under voltage condition of the "dim bulb" tester. Can anyone verify this to be true?

    Is there anything else I need to be concerned with now or just press on with the remaining bulb wattages in my tester until it is ready for a direct AC connect?

    I will post some pictures of the SPEC later. To put it mildly, the inside is a little rough. Some of the relay enclosures I was able to see are milky instead of clear, amoung other things so it would be fair to say this needs quite a bit of work.

    Any comments, suggestions would be appreciated. Thanks in advance for your help.

    Mark
     

     

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  2. laatsch55

    laatsch55 Super Member

    Messages:
    2,451
    Location:
    Gillette, Wyoming
    Had to reply just because of your name!
    There are a fair amount of Spec2 Gurus here that will help you. I'm not familiar with the dim bulb test, although with a variac my Spec 2 stayed in protect until 100 volts was reached for a few seconds. Other than that can't help you.
     
  3. laatsch55

    laatsch55 Super Member

    Messages:
    2,451
    Location:
    Gillette, Wyoming
    By the way, some of these Gurus are VERY busy people, and getting busier every day, a little patience may be called for.
     
  4. EchoWars

    EchoWars Hiding in Honduras

    Messages:
    28,402
    Location:
    Kansas City
    You're pissing off the soft-start circuit, and in danger of blowing up the chincy 10uf electrolytic that Pioneer uses to pass current till the relay closes, as well as the power resistor in the same circuit.

    If you're really set on 'bringing it up gently', put a 100W bulb in your tester and if it goes dim after 4 or 5 seconds, you're 98% likely to be safe to power it up directly from the mains.
     
  5. slipstream55

    slipstream55 Active Member

    Messages:
    236
    Location:
    Gilbert, Arizona
    Thanks for your responses, guys. I thought this might be an under-voltage issue. Echo, I won't piss it off anymore. Thanks for catching this in time. Just got back from the AZ RenFaire and was getting ready to throw the 75 watt bulb at it. I'll go with the 100 watter per your recommendation.

    Some more history on this amp...After I brought the amp back to the hotel from the pawn shop for a little more thorough examination (yes, I was on a business trip when I found it), I powered it on and blew the room circuit breaker. A second power on attempt was successful but the meters jumped pretty high before settling down. I can't remember if the "protection" indicator lit or not. It has been a year and a half since I have done anything with it and now that I finally have the time to work on it, I'm a little gun shy.

    I'll let you know the results of the 100w, 150w bulb checks and direct ADC connect check. I assume it will be OK to leave the amp on in idle for the caps to reform for a few hours during the light bulb checks If the "protection" indicator stays off. What if the "protection" indicator comes on and stays on..should I continue with the "dim bulb" checks and cap reform?

    Thanks, again.

    Mark
     
  6. EchoWars

    EchoWars Hiding in Honduras

    Messages:
    28,402
    Location:
    Kansas City
    If the protect doesn't go off, there's not a lot of sense in leaving the amp on. If that doesn't turn out to be an issue, and you want to leave it on for a while, take the top off and check the heatsinks every few minutes to make sure that you don't have excess idle current (heatsinks should just about barely make it to 'lukewarm' with no signal input).
     

     

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  7. slipstream55

    slipstream55 Active Member

    Messages:
    236
    Location:
    Gilbert, Arizona
    Thanks, again, EchoWars. The "protection" indicator did extinguish after about 6 seconds and stayed off during the time (about 2 hours) the 100w bulb was in operation. I noticed the RH meter movement going a little nuts before I shut everything off and don't know how long this was happening. Can I attribute this to the undervoltage condition the amp is in from being connected to my "dim bulb" tester? The amp did not seem to be getting very warm just sitting there "on" during all of this time.

    The 150w bulb for one hour "on" also did not seem to make the amp very warm. A good thing. Also, The "protection" indicator came "on" , then went "off" after 6 seconds (as normal?). Both meter movements were rock solid "off" during the time the 150w bulb was on. I did notice the RH meter movement jumped about a third of the meter scale when the "protection" indicator extinguished but the LH meter movement did not. A problem here?

    Lastly, do I check the DC Offset the same way on this amp as I have been doing on my other receivers? Digital meter set on DC (mV), all controls to "off", probes on speaker terminals. Thanks again.

    Mark
     
  8. EchoWars

    EchoWars Hiding in Honduras

    Messages:
    28,402
    Location:
    Kansas City
    Read this thread, and the links I posted therein.

    Offset is measured the same way as any other amp. No signal, volume down, meter set to read DC on the most sensitive scale.
     
  9. slipstream55

    slipstream55 Active Member

    Messages:
    236
    Location:
    Gilbert, Arizona
    I did a direct AC power up this evening on the SPEC 2. Relay clicks after 3 seconds, "protection" indicator winks off after about 8 seconds. I presume this is normal operation? Meters didn't jump this time and stayed stable for the 45 minutes it was warming up. DC Offset measures 7.5mV on RH channel and -41.0mV on LH channel. I take it there isn't a DC Offset adjustment on the SPEC 2? I couldn't find any reference to it in the SM.

    Mark
     
  10. EchoWars

    EchoWars Hiding in Honduras

    Messages:
    28,402
    Location:
    Kansas City
    Protect sounds like it's working as it should.

    No offset adjust. I just replace the 2SA798 transistors and cross my fingers that it ends up better than it was before.
     
  11. slipstream55

    slipstream55 Active Member

    Messages:
    236
    Location:
    Gilbert, Arizona
    Poopies. I was hoping not to have to do this. Why did Pioneer not include DC Offset adjustments on the SPEC 2 but did on most of their integrated amps and receivers (at least all of the ones I am familiar with)?

    Anyway, the 2SA798 in the SM says "-g" or "-f". Any idea what the difference is and which one to use? Can't find a spec sheet on the "-f" or "-g". Mouser carries a replacement, NTE42. NTE OK to use?

    When you said "cross my fingers"... if it works, great. If it doesn't, what can I expect to happen?

    Any idea on what Pioneer used for painting their covers and side panels on the SPEC 2? I need to do this and am trying to get as close to a perfect match as possible in finish, texture, and durability.

    I will be going to the UK in a few weeks and am going to try to round up some black metric screws to match what Pioneer used on the SPEC 2. Some of my screws are pretty corroded.

    The inside of my SPEC 2 isn't as bad as I originally thought. Needs some serious clean-up, though. I'm still working on the pictures.

    Regarding the power cord...If I replace it, what gage wire did Pioneer use? It feels like 14 but might be 16.

    Off topic: How do I get the neat little smiles into my posts?

    Thanks for all of your help so far.

    Mark
     

     

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  12. pustelniakr

    pustelniakr Silver Miner at Large Staff Member Super Mod Moderator Subscriber

    Messages:
    7,519
    Location:
    Tucson, AZ
    I would not NTE transistors for anything electronic. Wait a bit, and EW just might come across with a source or a suitable sub.

    Enjoy,
    Rich P
     
  13. EchoWars

    EchoWars Hiding in Honduras

    Messages:
    28,402
    Location:
    Kansas City
    If offset measures less than about 60mV, I would not sweat it too much. That's a long way from ideal, but I don't know of a source for these devices (maybe Consolidated Electronics). The alternative is to carefully match two devices and use them instead of the single 2SA798.
     
  14. slipstream55

    slipstream55 Active Member

    Messages:
    236
    Location:
    Gilbert, Arizona
    By less than 60mV, do you mean less than +60mV or does exceeding 60mV on the negative side count, too! (ie acceptable is less than +60mv or greater than -60mV with 0mV being ideal). I only ask this as I'm sure it could go more than the -60mv (as in -80mV or more negative). Are you confused? I am? Anyway, you get my point I hope.
     
  15. agger

    agger more Pioneers :-)

    Don't be too exact. If you don't hear a difference in distortion between the left and right channel better leave it like it is. Else you may screw up things which were not neccessarry!
     
  16. pustelniakr

    pustelniakr Silver Miner at Large Staff Member Super Mod Moderator Subscriber

    Messages:
    7,519
    Location:
    Tucson, AZ

     

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  17. EchoWars

    EchoWars Hiding in Honduras

    Messages:
    28,402
    Location:
    Kansas City
    Forget the sign...it's the absolute value (the 'distance' away from the 0.000V ideal) that counts.
     
  18. slipstream55

    slipstream55 Active Member

    Messages:
    236
    Location:
    Gilbert, Arizona
    Roger that, Agger. I just wanted clarification on acceptable voltage readings. Less than +60mV OK, 0mV ideal, any negative voltage (ie -10mV, -41mV or higher) is a worse condition than getting a reading of higher than +60mV.

    Thanks.
     
  19. slipstream55

    slipstream55 Active Member

    Messages:
    236
    Location:
    Gilbert, Arizona
    Well, just caught EchoWars reply. I guess that clears up the DC Offset voltage question I had.

    Thanks EW.
     
  20. laatsch55

    laatsch55 Super Member

    Messages:
    2,451
    Location:
    Gillette, Wyoming
    slipstream55, if you need some 2sa798's i've got a couple I can live without.
    I bought 10 or 12 but I can't find the bill to see where I got 'em. Have some 2sa733's too if you need some of those, from the same place,.
    When i find the bill(and I will) I'll post where I got 'em. They were only 1.09 too!
     

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