Toasted 400 still toast

62vauxhall

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#21
Like the English say, In for a Penny, In for a Pound.

I'd be doing exactly like you are, make it work. Those situations become a contentious point with me.
 

VSAT88

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#22
Doubtful that I can help but if you post needing something that I have you can get it. I wish you luck and more with the amp repair. Joe has been honest with me in my dealings with him and I have had no trouble with any parts I have gotten from White Oak Audio. I expect from the dealings I have had here on this site that most would be of the nature of helping well before hurting. Again, good luck with the amp. and post back about it. It will undoubtedly help me with future builds.
 

orange

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#23
Ray, if you really want this amp I would just let Lee or Jer or hell, Sniffer's bro Seat finish it even.

'Sokay, you run to the store for more TP now and then. I'm sorry it blew up too, that has to hurt. There are things (well, a LOT of them) over my head from time to time, and I have to get creative.

I sense that's what you are looking for, a little WOPL redemption value.

I myself tend to put things away and some time later when i get them out and want to use them again I find out why I pulled it in the first place :whax::???:

Well, dang that.
 

roccus

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#27
Here is the latest.... Joe has asked I send the control board to him so will do next week. When I had put this away a couple years ago I had replaced all blown and burnt out components on the right channel backplane board, the left channel tested fine no damage found. I then installed the first row of power transistors in and powered it up with my veriac and DBT, nothing blew up or fried up but found the left output and right output was different... I don't recall what it was I have notes I think but not a big deal to power it up again and see what is up. I remember after the test and some further testing I think it may be one of the power transistors that is causing the discrepancy... I picked up enough new power transistors to replace all the transistors on the right channel as they all got damaged from the resistor swap on the control board.
 

62vauxhall

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#28
Output transistors on a 400 did not go well for me either. I would have sworn the graphics on the cases all went the same way. The increased force needed to get some pins in some sockets plus that holes in those cases did not quite lining up with their holes in chassis (making the screws hard to tighten) should have clued me in but didn't.

It had to go immediately to Dr. Glen's ER (Emergency Repair) room for assessment and mending.
 

roccus

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#29
With the use of one of those pen handle magnets it is not to hard just take your time.... I put the 2 screws in the transistor first then slowly lower it to the chassis, align the screws to the screw holes, then as you lower it further align the pins, they pretty much just drop right in for me. That reminds me... I think maybe I should order some new silicon heat pads for the transistors instead of using the ones that were there.... but then none of them were damaged when I removed the transistors
 

orange

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#30
We'll get your WOPL bruising tail ends again soon!
 

roccus

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#31
After I rebuilt and repaired the damage backplane board I had put it in and just put one row of output transistors to check things out that went well so today I took the board back our and cleaned it all back up pretty and shinny... I need to wait to get some new heat pads before I start installing the transistors, the ones I removed looked a bit compressed so better safe than sorry...
 

orange

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#32
Excellent! It sounds like your plans for speaker domination are finally coming together! :whdat:
 

roccus

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#33
Got all the power output transistors in and powered up No smoke, sparks, or flames.
Thought I would run the numbers by you all to see what you think. With veriac turned up to output 115V this is what I got at test points.

Left side..... B+ 76.17V, B- 76.56V, PAD 11 75.94V, PAD 12 76.54V
Right side... B+ 75.86V, B- 76.48V, PAD 11 75.84V, PAD 12 76.46V
 

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#34
Got all the power output transistors in and powered up No smoke, sparks, or flames.
Thought I would run the numbers by you all to see what you think. With veriac turned up to output 115V this is what I got at test points.

Left side..... B+ 76.17V, B- 76.56V, PAD 11 75.94V, PAD 12 76.54V
Right side... B+ 75.86V, B- 76.48V, PAD 11 75.84V, PAD 12 76.46V
 

Gepetto

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#35
The important measurement is the output measurement Ray. TP4 labeled OUTPUT with the gray test point in it.
 

Gepetto

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#37
Yea I got that to....
Output L 75.74 and R 75.70
That is not a good sign Ray. Tack a 10K ohm resistor from output to ground, you have a DCP in place so you can jumper it across that terminal block.

With a 10K ohm resistor in place as above and no control board connected, you should measure zero or extremely close to zero.
 

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roccus

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#38
OK thanks... I do have the 10K resistor in place on both sides and the ground wire is disconnected so gotta go look something else must be blown.... Thanks for the Doc most all my Docs are on a laptop that died over a year ago so I was going on memory and remebered about the resistors and ground wire to test but could not remember for sure about the voltages.....
 

roccus

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#39
Here are the new measurements..... from the back planes with all output transistors in and powered up to 115V

Left side........ B+ 77.67V. B- 77.69V, Output .0005V
Right side..... B+ 77.65V, B- 77.68V Output .0007V
 

Gepetto

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#40
Here are the new measurements..... from the back planes with all output transistors in and powered up to 115V

Left side........ B+ 77.67V. B- 77.69V, Output .0005V
Right side..... B+ 77.65V, B- 77.68V Output .0007V
Those numbers look good Ray.
 
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