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looking for Spec-2 help

M

mchriste

Active Member
The other day I finished a restoration of a Spec 2, I posted here how happy I was with it. Now unfortunately the same issue I had with the left channel is popping up again. Here is what happens:
-When listening, usually at low volume, the left channel sometimes get really low volume with high distortion. It sounds like a symptom of dirty pots and switches that we've all heard (the two pots and the ohm selector switch have been cleaned, and re-cleaned a lot.
-While the distoring is present, the meter for that channel keeps plugging away like nothing is wrong as though the output is the same as normal.
-What will make the distortion and lowness go away is power... if I bump the volume it goes away and sounds good, I can usually lower the volume again and it will sound fine. I can also switch from 4ohm to 8ohm on the back and the problem will go away, but will come back at either setting. Sometimes it doesn't happen for days.
-I was able to measure the bias on all the transistor pairs during an episode of it happening, and they all are good right around 30mv.
- I have low DC offset, like less than 5mv on either channel (I've checked this during an episode of distortion too)
-This is the same issue I experienced before I restored many parts, including (done to both amp boards) all electrolytic caps, all transistors (not the outputs, they are orig) the three trim pots, RL1. Additionally all the other electrolytic caps on the unit were replaced.

I'm looking for any ideas you may have of where to look given these symptoms. I've eliminated the possibility that its my preamp, duplicated the problem with another preamp, swapped RCA leads and the problem stays on the left channel.

I think what i'll do next is reflow every joint on the board, although I've inspected them and they look good.
Thanks,
Mike
 
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AE Bob said:
You likely have a bad protect relay. Burnishing / cleaning the contacts will likely resolve the issue.
Click to expand...

Bob, thanks for the reply. Let me ask you something, do you think if the speaker protection relay was chattering or whatever, that the protection light would illuminate? it doesn't.
Second, I did open and clean the relay contacts as part of my work, but let me tell you how I did it and if I should use some other technique; I removed the cover and took an index card folded in half, soaked it in deoxit and slid it between the open contacts and went back and fore. This resulted in some blackness that eventually went away.
Can/should I be more aggressive with this? maybe some 1000 grit soaked in deoxit?
Thanks for your help!
 
Deoxit is for the contacts scrubbing each other. There is little of that type of motion in an opening and closing of a relay.

I ain't just whistling dixie here, I was employed by Magnecraft Relays (when they were in Chicago, up on Lynch ave (west of Elston Avenue ) by Switchcraft (west of the SOS Driver's facility)
Did various Engineering testings, I was (part of) developing microprocessor automated testing for the end of production lines.
I was hardware, my co-worker was software.

1000 grit would strip the plated on material off of the contact.

MAYBE less aggressive scrubbing with the equivalent of a pencil eraser (NOT PEN!!!! :yikes: )

All that can be alleviated by zebulon1's suggestion. Otherwise you will find yourself fiddling with it at odd intervals, instead of resetting the clock.
 
Last edited:
markthefixer said:
Deoxit is for the contacts scrubbing each other. There is little of that type of motion in an opening and closing of a relay.

I ain't just whistling dixie here, I was employed by Magnecraft Relays (when they were in Chicago, up on Lynch ave (Elston Avenue ) by Switchcraft (west of the SOS Driver's facility)
Did various Engineering testings, I was (part of) developing microprocessor automated testing for the end of production lines.
I was hardware, my co-worker was software.

1000 grit would strip the plated on material off of the contact.

MAYBE less aggressive scrubbing with the equivalent of a pencil eraser (NOT PEN!!!! :yikes: )

All that can be alleviated by zebulon1's suggestion. Otherwise you will find yourself fiddling with it at odd intervals, instead of resetting the clock.
Click to expand...

Mark, thanks good copy on all. Do you concur that with my symptoms sounds like a relay?
 
Shikaka said:
I just did a total rebuilt on my Spec-2 last winter. You may find this old thread from 2007 on Spec-2 relays very helpful. You mentioned that you replaced the primary surge relay, but not any of the others. There is a small "crappy" relay on each power amp board that historically has been problematic.

https://www.audiokarma.org/forums/index.php?threads/pioneer-spec-2-unstable-bias.113229/
Click to expand...

thanks for the link, those two relays I’ve replaced as per those instructions, no other relays have been replaced. I’ll probably order replacements for the three larger relays, and I the meantime give the current originals another clean.
 
Sorry, it was my confusion about which "RL1" relay you replaced. I quickly looked at my large Spec-2 schematic where "RL1" is shown as the primary surge current relay, but forgot about Pioneer's inconsistent device tagging between their main schematic and their individual PCB schematics (they also labelled the small paper covered relay on the amp board as "RL1" on their individual board schematics).

Another thought; perhaps trying a temporary jumper around the interposing contact from the output relay could confirm (or rule out) that a bad relay contact is the source of the problem.
 
I usually burnish / clean protect relay contacts with a small strip of 3000 grit emery paper folded in half lengthwise to make a two sided strip. I put it between the contacts and slide it back and forth while pressing the contacts together with my finger. The 3000 grit is so fine that it doesn't take much material off, but will remove the tarnish. I typically visually examine the contacts, and work until they are shiny. I then clean them with residue free contact cleaner and then put a small amount of electronic lube on them. I have virtually no problems with this process, unless the contacts are burned from running too long with tarnished contacts. If the contacts will not shine up with a few swipes of the 3000 grit, the relay should be replaced, as too much "burnishing" will remove the hard contact surface plating.
 
AE Bob said:
I usually burnish / clean protect relay contacts with a small strip of 3000 grit emery paper folded in half lengthwise to make a two sided strip. I put it between the contacts and slide it back and forth while pressing the contacts together with my finger. The 3000 grit is so fine that it doesn't take much material off, but will remove the tarnish. I typically visually examine the contacts, and work until they are shiny. I then clean them with residue free contact cleaner and then put a small amount of electronic lube on them. I have virtually no problems with this process, unless the contacts are burned from running too long with tarnished contacts. If the contacts will not shine up with a few swipes of the 3000 grit, the relay should be replaced, as too much "burnishing" will remove the hard contact surface plating.
Click to expand...

I did this last night, with mixed results. New relays en route. I’m no sure how well I got in there with the 3000 grit.
Thanks for everyone’s help, hopefully new relays fix the symptoms.
Mike
 
Thanks for the help everyone, I replaced the two relays on the power supply board (those were a PITA to de-solder) and the one on the meter board. So far so good! (but iIwas fooled before) I'll put it through its paces, hopefully I'm done with this one!
Mike
 
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