PL400 Series 2 problems...maybe
- Thread starter TrialByFire01
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- Aug 23, 2023
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I really appreciate the the helpful comments from everyone especially laatsch55 and gene french ( this is supposed to be a helpful forum for DIY repair ...right? ). WOPL Sniffer must be trying to sell WOPL boards or just plain needs everyone to do what he wants, that's why the fear mongering and constant sales pitch. Maybe he should just be a politician. These two amps are in great condition minus the bizarre tiny traces in this design that only a beginner at soldering or the two overheating power supply resistors could lift. And if I had a Bently I sure as hell wouldn't be working on a PL400.
Perhaps you missed this helpful advice that I posted for you...
If you are measuring current through/voltage across the emitter resistors at idle, you have big problems. The bias is set at the 10 ohm bias resistor, the 0.35V setting is not intended to have any main output device conducting at idle.
You need to debug and fix your bias problem before you have bigger issues. Perhaps you have a leaky driver transistor or the one that preceeds it. It is not a healthy sign if you cannot get your bias into range.
If you are measuring current through/voltage across the emitter resistors at idle, you have big problems. The bias is set at the 10 ohm bias resistor, the 0.35V setting is not intended to have any main output device conducting at idle.
You need to debug and fix your bias problem before you have bigger issues. Perhaps you have a leaky driver transistor or the one that preceeds it. It is not a healthy sign if you cannot get your bias into range.
No one does, until it happens...
When the original control board fails and the amp latches up and sends 80VDC to a nice big speaker and the woofer voice coil melts and catches the cone on fire, then the drapes...
Then the insurance company reads the Fire Marshal's report about the fire starting in the man cave and they discover YOU worked on the 50-year old amplifier as a non-factory certified technician or a licensed electrician; so no payout.
The horror stories are out there. But hey, don't say the Navy trained electronics technician or the electrical engineer didn't warn you.
When the original control board fails and the amp latches up and sends 80VDC to a nice big speaker and the woofer voice coil melts and catches the cone on fire, then the drapes...
Then the insurance company reads the Fire Marshal's report about the fire starting in the man cave and they discover YOU worked on the 50-year old amplifier as a non-factory certified technician or a licensed electrician; so no payout.
The horror stories are out there. But hey, don't say the Navy trained electronics technician or the electrical engineer didn't warn you.
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- music...the healer of souls...
i promise i wont say a tech and/or engineer didnt warn me...when these amps burn down the house, farm, guayabo, and maybe the whole northwest corner of costa rica....
lots of horror stories out there about a lot of things...cant worry about them either...got better things to do...
cant believe that keeps you up at night...
didnt know you had to be certified electrician or engineer to work on electronic video or audio equipment...didnt need one in the 25 years i fixed computers, printers, monitors, power supplies...etc
i learn something new every day!!!
lots of horror stories out there about a lot of things...cant worry about them either...got better things to do...
cant believe that keeps you up at night...
didnt know you had to be certified electrician or engineer to work on electronic video or audio equipment...didnt need one in the 25 years i fixed computers, printers, monitors, power supplies...etc
i learn something new every day!!!
You don't. But insurance companies will hire a $50,000 arson investigator to save a $150,000 homeowner's claim. My stepfather was in the insurance business and explained to me that he has seen too many people become homeless with no money just for things people take for granted or don't worry about.
I sleep well at night. And I have been known to pay a licensed electrician $150 to look into my circuit breaker box and close it up; and I keep that receipt in the fire proof safe. I want that insurance check.
I don't want to become homeless and I don't want anyone on this Forum to become homeless. So, Ground your equipment and don't let 50 year-old failure-prone components fester.
I sleep well at night. And I have been known to pay a licensed electrician $150 to look into my circuit breaker box and close it up; and I keep that receipt in the fire proof safe. I want that insurance check.
I don't want to become homeless and I don't want anyone on this Forum to become homeless. So, Ground your equipment and don't let 50 year-old failure-prone components fester.
I think we have digressed into several conversations… which is typical.
My point was/is if you are repairing something someone else will power and use in their home, and it burns the house down (or just stops their heart) you, the repair person will be squarely in the crosshairs of a swarm of attorneys.
If you want to repair something for yourself, that’s a completely different conversation.
Have fun!
My point was/is if you are repairing something someone else will power and use in their home, and it burns the house down (or just stops their heart) you, the repair person will be squarely in the crosshairs of a swarm of attorneys.
If you want to repair something for yourself, that’s a completely different conversation.
Have fun!
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- ---not quite right
Gotta agree with you Gene.
My uncle is running a bone stock 400 since he bought it new in the 70’s as his studio amp, he runs his drums and keyboards through it and it’s only ever failed when the jam session gets things too far into the red. Tim, my 700/1 has only the WO driver board and Don’s DCP, stock backplane. I’ve ABSOLUTELY PUNISHED that amp and it even has xpl909’s in one channel still. Over temp cut out many times, 4 ohm speakers... id love to see one insurance claim of a house burned by one of these amps, if they’re fused properly it should be a nothing burger. That said I did have smoke pouring from a set of speakers once when stock Linda went DC so I definitely agree that Don’s DCP should be installed, the rest can come as needed/cash allows if the owner so chooses (but it is damn good stuff) no need to break balls over it, most people probably don’t drive their stuff as hard as some of us...
My uncle is running a bone stock 400 since he bought it new in the 70’s as his studio amp, he runs his drums and keyboards through it and it’s only ever failed when the jam session gets things too far into the red. Tim, my 700/1 has only the WO driver board and Don’s DCP, stock backplane. I’ve ABSOLUTELY PUNISHED that amp and it even has xpl909’s in one channel still. Over temp cut out many times, 4 ohm speakers... id love to see one insurance claim of a house burned by one of these amps, if they’re fused properly it should be a nothing burger. That said I did have smoke pouring from a set of speakers once when stock Linda went DC so I definitely agree that Don’s DCP should be installed, the rest can come as needed/cash allows if the owner so chooses (but it is damn good stuff) no need to break balls over it, most people probably don’t drive their stuff as hard as some of us...