Jerry's "Gonna Rebuild me PLWO 1000" thread

Damn...

Bah....

Crap...

Scope testing didn't go so good. Serious oscillation on the right channel, and the left channel has what looks like a IM spike of some sort, and neither can handle a load...

Ahhh.. I'm taking a break.. a long one... I'm going to say it was probably learning the right (and wrong) way to align and seat the trannies in their sockets. Tough lesson, but I'll give it another stab in a few weeks hehe. or sooner.. who knows..
 
An output touching the chassis will cause an oscillation.
 
Pull the outputs and leave the drivers. It is about a 100 Watt amp with just the drivers installed and this will confirm the problem is pre-driver/driver, or outputs.
 
mlucitt said:
Pull the outputs and leave the drivers. It is about a 100 Watt amp with just the drivers installed and this will confirm the problem is pre-driver/driver, or outputs.
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Everything except the MJ15024's on the bottom, or except them and at least one row of the others?
 
Hehe. in the meantime, me M-80 "custom" will do. Had it rattling the walls earlier with some "Divine Moments of Truth" going. My wife thought a portal to another dimension opened, and out poured a tribe of cannibals upstairs. They almost had me for the "pot", but I escaped.

After a good 20 minutes at Mach 7, the '80 was barely warm.. HMMM.... I think those FG caps and the big beer can caps on the back have finally got themselves burned in good.
 
Yeah, just the 024's on the bottom row will give you 100 Watts. If the problem persists, you can pull them too but I think you may find your problem with the 024's in-place. They do a nice job of holding the heatsinks on.
 
Ok will do. I'm going to get a 200W 8ohm dummy load first (well, two of 'em, I guess). Need to properly load it without beating the crap out of my speakers should things go wrong. Yeah, a MUST for every tech's bench.. I know.. :thumbright:
 
Dummy loads in hand, now back to it...

Ahhh.. so "grasshoppah" here sees wisdom in old and wise PL tech advice! Got to take it SLOW and EASY... I took out all of the outputs from the right channel (that was the worst - the left can "live" but the right really had issues). Then two by two, back in. I'm up to the drivers and two sets of outputs.

rstest4.jpg


Fired up.. no issues.. DC offset is really good now on the right side...

rstest1.jpg


And now we go for the "power"... not too bad considering I'm at 2/5'ths capacity... (need tripod yeah yeah.. that's 5V per division there... half the waveform shown til I come up with a .5X voltage divider or somethin.. )

rstest2.jpg


rstest3.jpg


As I told Lee tho, I think these sockets were probably a little bit "advanced" for me to be "patient" with them. The boss's on the top end are a bit thin for seating good on the chassis, and it's real easy to overdo the solder on the base and emitter pins to where it flows down and effectively welds the contacts. I'm going to see what I can do to continue working with 'em, but I may replace a few problematic (read - really 'effed up by ME.. oops.. ) ones if I can't get the MJ's in there just right.

It's salvageable I think.. I aint giving up so easy, so Lee.. y'aint getting this back in a box.. no way, jose! :cheers:

I'm getting the finesse thing down, no probs!
 
laatsch55 said:
Good Job Jer!! Makin music??
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Not yet - seeing if I can reseat all outputs successfully. Like I said.. slow n easy.

Heheh.. but I am having fun with these dummy loads. Here's the Yamaha M80 @ 60 hz..

m80out.jpg


Holy shit... is that really 587 watts @ 8 ohms or did I not calculate that right??? Yeah, just one channel driven (I don't want to nuke both dummy loads should they not be able to handle it).. but STILL... whooaa.. Can't say either if it was clipping since I couldn't see the peaks.. hmmmm... maybe that yammy does have some balls?? :ugeek: :mrgreen:
 
Pretty sure the flat tops went quite a ways at that voltage. Put you loads in some cold mineral oil, Dry ice, Liquid N2, whatever ya got handy. Then ya can romp on it!!

BTW--I came up with 589.
 
laatsch55 said:
Pretty sure the flat tops went quite a ways at that voltage. Put you loads in some cold mineral oil, Dry ice, Liquid N2, whatever ya got handy. Then ya can romp on it!!

BTW--I came up with 589.
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Heheh.. I'm going to have to make a voltage divider so I can see exactly where it's clipping. I tell ya tho.. I have it on a 1500VA UPS, and it told me flat out "I can't do nothing more for ya"... the input watts were up over the limit of 865 with about 200 of that going to the computer stuff. The rest of it was the Yamaha.

Dummy loads.. nice... now I can save some hearing, whatever's left.
 
You ......................have.......................hearing......................left??
 
When using the green TO-3 sockets you should pin the heatsinks for alignment. The original ones were protruding out the back and used to align the heatsinks. Misalignment can cause the pins and bolts from the transistors to groung out. There is quite a bit of movement without the pins
 
mlucitt said:
I like the one on the right, I dn't know why...

Make sure the .27 Ohm resistors are negative biased and the .33 Ohm resistors are positive biased, just look at the schematic and you'll see what I'm talking about.
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Ok, so now I'm back to the square sockets. I have the left side done, and it came out rather nice (pics later.. wife stole camera). Anywhoo... was reviewing this thread.. and. HMMM...

Hey Mark.. if ya mean make sure the .33's are on the left side and the .27's are on the right side, yep, they are (I have the layout just about committed to memory).

But .. if you are trying to tell me that resistors can be negative or forward biased.. are you kiddin???? If so, I just got the joke.. lol.. Naaa... can't pull that on me. :cyclops: IR smarter... :mrgreen:

Anywhoo.. more pics later. I didn't have any problems with the heavy buss bars, which was kind of surprising. Might be ready to test out by tomorrow.
 
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