Newly assemble pl14 rev G bias trimmers do not work correctly

CrazyIvan said:
Quasi appears to be working now. redid board as required. Anyone know how decent Watts is to deal with? I bought the DCP board prebuilt. In trying to switch the cap, it took the trace out of the board when removing.
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HInt on rework, always sacrifice the component. Cut the component off and then you will be able to remove the leads easily, one at a time.
 
the reason I said go Full Comp, if you decide to go quasi, and then decide to go Full, you'll have to gut the whole amp again, rework the control board and then install all new wiring and the back planes..... It's just a waste of time and effort all for $150...... Just sayin.....
 
Skratch said:
Looks like your amp has blown before, you have at least 3 different date codes on the output transistors. You may want to check and make sure none are open or shorted
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I bought this amp from a photographer who took pics at rock concerts from the 70's till today. He said he bought the amp off Emerson lake and Palmer after the last show of their concert tour. 1974 or 1975 I think.
 
Gepetto said:
HInt on rework, always sacrifice the component. Cut the component off and then you will be able to remove the leads easily, one at a time.
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I had no room to get my snips under that tiny capacitor, I was able to delsolder the leads and push it out.
 
I like .308 for watermelon removal, The soldapult (well made solder sucker)for capacitor removal.......If its full of 2SC458s I might reach for that .308 again
 
I have two soldapults. Other than tips piping off when I “arm” it too quickly, they work fine.
 
As usual, I'm late to the party. Saturday night when this thread started the wife did a stage dive, 12 steps down and landed by the front door. Fortunately no broken bones. 10 stitches to sew up the gash in her knee. Sunday, traveled to Houston office to teach a class this week. NOt much time for anything else.

To move forward and answer a couple questions:

Who built the board? The important thing is who doesn't, me. "Tami" builds the boards. She runs the PCB dept at my day job. Has all of the certifications including ISO-9000 and is part of the team for components qualified for use in safety related equipment at nuclear power plants. And she's human. She's built built hundreds of boards for me and 1000's at the day job. Thus far on my boards she put 1 chip in backwards and had a bridged solder joint . I can live with that.

If anyone ever wondered why there is a drop of finger nail polish on a DCP board, it's my QC stamp. Every board gets inspected, and then tested in a working amplifier to verify proper operation on both inputs. On the back of the board I stamp the date. When inspecting the boards I usually focus on solder bridges, especially around the binding posts. I missed this one.

Next question: Is wattsabundant easy to deal with? I do this for beer money (1/6 barrels). It's not intended to pay the rent. I don't have a P&L statement. In instances like this I ask the question, what's the right thing to do? Answer: Replace the board. I consulted Spencer on that last night over beers.

I wish I had known about the issue before the attempted surgery on the board, and the surgery on my wife's knee, and the problem could have been avoided.

If a cap has to get installed backwards on the DCP, C7 is the one to do. That's the timing cap on the detector. It rarely sees more than a few millivolts and had it been left alone would have been fine. Electrolytics can withstand a certain percentage of reverse voltage. I've been wanting to address that here and intend to do so soon. I have a great document on electrolytics (29 pages I think) that I include in the document package for my training classes. I also have an OE (operating experience in nuke-speak) on a cap installed backwards.

Todd: I'll send another board and ask you return the old one. I keep an emergency stock at my Houston office. It will go out in a day or two. In the mean time I would like to see a photo of the damage.
 
Fully comp is way better than Quasi. Project for later sounds like now.

Cool history on your amp OP
 
wattsabundant said:
As usual, I'm late to the party. Saturday night when this thread started the wife did a stage dive, 12 steps down and landed by the front door. Fortunately no broken bones. 10 stitches to sew up the gash in her knee. Sunday, traveled to Houston office to teach a class this week. NOt much time for anything else.

To move forward and answer a couple questions:

Who built the board? The important thing is who doesn't, me. "Tami" builds the boards. She runs the PCB dept at my day job. Has all of the certifications including ISO-9000 and is part of the team for components qualified for use in safety related equipment at nuclear power plants. And she's human. She's built built hundreds of boards for me and 1000's at the day job. Thus far on my boards she put 1 chip in backwards and had a bridged solder joint . I can live with that.

If anyone ever wondered why there is a drop of finger nail polish on a DCP board, it's my QC stamp. Every board gets inspected, and then tested in a working amplifier to verify proper operation on both inputs. On the back of the board I stamp the date. When inspecting the boards I usually focus on solder bridges, especially around the binding posts. I missed this one.

Next question: Is wattsabundant easy to deal with? I do this for beer money (1/6 barrels). It's not intended to pay the rent. I don't have a P&L statement. In instances like this I ask the question, what's the right thing to do? Answer: Replace the board. I consulted Spencer on that last night over beers.

I wish I had known about the issue before the attempted surgery on the board, and the surgery on my wife's knee, and the problem could have been avoided.

If a cap has to get installed backwards on the DCP, C7 is the one to do. That's the timing cap on the detector. It rarely sees more than a few millivolts and had it been left alone would have been fine. Electrolytics can withstand a certain percentage of reverse voltage. I've been wanting to address that here and intend to do so soon. I have a great document on electrolytics (29 pages I think) that I include in the document package for my training classes. I also have an OE (operating experience in nuke-speak) on a cap installed backwards.

Todd: I'll send another board and ask you return the old one. I keep an emergency stock at my Houston office. It will go out in a day or two. In the mean time I would like to see a photo of the damage.
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wattsabundant said:
As usual, I'm late to the party. Saturday night when this thread started the wife did a stage dive, 12 steps down and landed by the front door. Fortunately no broken bones. 10 stitches to sew up the gash in her knee. Sunday, traveled to Houston office to teach a class this week. NOt much time for anything else.

To move forward and answer a couple questions:

Who built the board? The important thing is who doesn't, me. "Tami" builds the boards. She runs the PCB dept at my day job. Has all of the certifications including ISO-9000 and is part of the team for components qualified for use in safety related equipment at nuclear power plants. And she's human. She's built built hundreds of boards for me and 1000's at the day job. Thus far on my boards she put 1 chip in backwards and had a bridged solder joint . I can live with that.

If anyone ever wondered why there is a drop of finger nail polish on a DCP board, it's my QC stamp. Every board gets inspected, and then tested in a working amplifier to verify proper operation on both inputs. On the back of the board I stamp the date. When inspecting the boards I usually focus on solder bridges, especially around the binding posts. I missed this one.

Next question: Is wattsabundant easy to deal with? I do this for beer money (1/6 barrels). It's not intended to pay the rent. I don't have a P&L statement. In instances like this I ask the question, what's the right thing to do? Answer: Replace the board. I consulted Spencer on that last night over beers.

I wish I had known about the issue before the attempted surgery on the board, and the surgery on my wife's knee, and the problem could have been avoided.

If a cap has to get installed backwards on the DCP, C7 is the one to do. That's the timing cap on the detector. It rarely sees more than a few millivolts and had it been left alone would have been fine. Electrolytics can withstand a certain percentage of reverse voltage. I've been wanting to address that here and intend to do so soon. I have a great document on electrolytics (29 pages I think) that I include in the document package for my training classes. I also have an OE (operating experience in nuke-speak) on a cap installed backwards.

Todd: I'll send another board and ask you return the old one. I keep an emergency stock at my Houston office. It will go out in a day or two. In the mean time I would like to see a photo of the damage.
Click to expand...
Glad to hear your wife is ok. That is the most important thing.
 
What's the bottom of the board look like? The track goes from R3 to the cap and then on to Pin 2 of the chip. The negative terminal of the cap goes to the ground bus. If a cap is available the board could be repaired with a strand of wire IMG_4157[1].JPGIMG_4157[1].JPG
 
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