I just purchased a PL 400 Series 2 amp but have 85 volts AC on output with no input

Dr12volt

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#1
I just bought this beautiful 400 series 2 but get 85 volts AC with no input. DC output in in the mV range. It shows up after about 2 seconds after i turn it on. The input sensitivity adjustment has no effect on output. Any suggestions on where to start to look for issues? thanks in advance
 

BlueCrab

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#2
Always start with a visual inspection with everything unplugged. I use my nose too, to check for anything toasted. Check fuses. If that looks and smells ok, then I'd bring it up on a variac and dim bulb tester while monitoring the power supply voltages. Everything begins and ends with the power supply. Photos of what you've got would be helpful.
 

Dr12volt

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#3
Always start with a visual inspection with everything unplugged. I use my nose too, to check for anything toasted. Check fuses. If that looks and smells ok, then I'd bring it up on a variac and dim bulb tester while monitoring the power supply voltages. Everything begins and ends with the power supply. Photos of what you've got would be helpful.
soon as I get a chance to take it apart I will post pics. thank you.
 
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#5
If it is really AC the rectifier is shorted, if pulsed DC filter caps are shot.
Of course as already stated some outputs are kaput as well.
 

wattsabundant

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#6
I just bought this beautiful 400 series 2 but get 85 volts AC with no input. DC output in in the mV range. It shows up after about 2 seconds after i turn it on. The input sensitivity adjustment has no effect on output. Any suggestions on where to start to look for issues? thanks in advance
I could believe 85 millivolts. Blown rectifier blows AC input fuses. Blown outputs blow fuses and/or has 80VDC on the output.

First of all strongly consider wearing safety glasses. There is 160 VDC across the main caps. Get across that and you're dead.

Stop and build the dim bulb test set (see attachment) first. Then measure the DC voltage (about 80VDC) on the main caps and then the AC ripple voltage (less than 100 millivolts) on the main caps.

Attached is the 400II service manual. Read and follow the troubleshooting section. Do not buy a parts kit and change out a bunch of parts that haven't failed.
 

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WOPL Sniffer

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#7
I just bought this beautiful 400 series 2 but get 85 volts AC with no input. DC output in in the mV range. It shows up after about 2 seconds after i turn it on. The input sensitivity adjustment has no effect on output. Any suggestions on where to start to look for issues? thanks in advance

Is that one of them Chinee meters???
 

wattsabundant

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#8
Is that one of them Chinee meters???
Maybe Harbor Freight for $6.99. Actually Harbor Freight has a true RMS meter. 1000v cat. III input? NFW on that. I bought some $25 meters at Harbor Freight a few years ago specifically for testing SCR's and diodes out of circuit. Someone grabbed one and put it on 480 VAC and melted the case.
 

Dr12volt

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#13
I could believe 85 millivolts. Blown rectifier blows AC input fuses. Blown outputs blow fuses and/or has 80VDC on the output.

First of all strongly consider wearing safety glasses. There is 160 VDC across the main caps. Get across that and you're dead.

Stop and build the dim bulb test set (see attachment) first. Then measure the DC voltage (about 80VDC) on the main caps and then the AC ripple voltage (less than 100 millivolts) on the main caps.

Attached is the 400II service manual. Read and follow the troubleshooting section. Do not buy a parts kit and change out a bunch of parts that haven't failed.
Thank you for all of your help. I will begin to tear into it in about 2 or 3 weeks. Got a few business trips to do in the mean time. I looked at your service bulletin and it is hard to read several areas. I have another copy that is not much better. Does anyone have one that is actually readable so you can see the part placement and values clearly? thanks.
 

George S.

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#15
Oh, and before you print them, go into printer settings and select the highest quality settings. It does make a difference on the schematics.
Nonetheless, I've found issues even with the best scans. So I open the PDF on a large monitor near my bench and expand the area in question. Makes it easier to read component values that are faint.
Have fun!!!
 

Dr12volt

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#19
thanks to all of your help...i was in error....it was DC voltage. I was on the wrong meter setting and didnt realize it. I have put this one aside for a bit. I have 3 more of them I am currently updating to WOPL standards. thanks
 
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