phase linear 400

Sunnbobb

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Nice!! I picked up a couple "non-working" Furman PS-8's a few weeks back. I have the first one up and running, it needed a single 1000uf 50V capacitor. The second one has a dead EFI filter, I'm waiting for the part to arrive. Pretty easy to work on. I'll probably off one of them to cover the cost of one. Now I can tell the girl, "make sure the volume is down and hit this switch". LOL
 

gene french

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Nice!! I picked up a couple "non-working" Furman PS-8's a few weeks back. I have the first one up and running, it needed a single 1000uf 50V capacitor. The second one has a dead EFI filter, I'm waiting for the part to arrive. Pretty easy to work on. I'll probably off one of them to cover the cost of one. Now I can tell the girl, "make sure the volume is down and hit this switch". LOL
or dont tell her!!!
lololol
 

gene french

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just returned from a 2 week family visit to louisiana...it was very nice....people came in from everywhere...got special time with the grandkids...even had a crawfish boil...complete with homemade ice cream...interesting...and thankful!!!
 

gene french

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a week or so ago...
one of my stock 8 fins quit....it drove the 6" midranges ...i had a spare to replace it...also stock....so far so good!!!
decided to take a look at the non functioning unit...
the dcp board was not cycling...THANKS MR. DON!!! YOU SAVED ME AGAIN!!!...disconnected the inputs to dcp and discovered 57v dc on right channel...left channel functional....its a 14a board...checked all diodes and transistors...no sign of a problem...btw, the dbt would come up bright and dim as one would expect...checked all wiring to make sure nothing had broken....removed top two outputs xpl909 original right channel...the dc voltage on the right channel went away...no change in dbt..and the dcp relay cycled...right channel now playing...i tested both transitors with dvm and transistor checker...showed nothing wrong...reinstalled one at a time checking after each ...seems to be working fine ...
kinda strange...havent put it back together yet..
gonna let it cook tomorrow...then will keep it as a spare...i also have a wopl spare...
alls well that ends well...i guess..
 

George S.

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I'm thinking it's a short in those old sockets.
If I had a old socket, I'd think I'd shave it with a blade and see what contacts when those screws are tightened.
The rubber socket insulation on the first 400 I WOPL'd was totally trashed from poorly done output replacements. The raised portions that center the socket in the holes were really messed up and several showed severe over tightening of the screws with squashed insulation rubber.
Would have been difficult to keep the screws or the sockets screw hole tabs from grounding.
If I got it working on the bench, I would have been hesitant to move it and cause a shot.
 

George S.

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Yup Gene. That first unit I tore down.
Looked like they had a hell of a time getting the output leads into the sockets. Then they pushed the screws in too hard moving the socket away from the chassis and it was no longer aligned properly.
Then they tightened the screws with a misaligned socket. The edge of the insulation that fits the holes for alignment was sheared off or squished and the screw hole tabs bent.
Was a terrible mess. Glad I never plugged it in.
I've been wondering if there may be two pieces of metal in them that are separated by rubber that may contact and short if overtightened.
I don't know. I do know the screw tab or screw better not short to chassis.
 

gene french

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strange thing was..dbt never showed indication of being in a shorted state....always operated normally...bright to dim...but, after reseat/retightening, the dcp cycled normally..and it played music...
but, it was fun!!!
not gonna put much effort in keeping the stock units...a wopl unit makes more sense....i however, enjoyed the learning experience!!!
 

gene french

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well...went to let it cook today...played a bit ...made static...quit...dc again...removing all outputs did not help...sorta...
changed 3 sockets...carefully installed outputs...
all good till i plugged in speaker...dcp shut it down...disconnecting right side produce a dcp cycling on/off on left side ..then i heard the voice..."check the test equipment"..
impediance showed shorted speaker...i guess all of my trouble shooting... my test speaker was damaged and this completely shut it down...i had a tweeter and a cheap xover...it ohmed out a bit over 6 ohms....still playing...
i now need another test speaker(s)..that poor tweeter sounds terrible...
one of the sockets was cracked...another had been strippef out and the third would no seat in the holes properly....i was extremely careful...the speaker smoked one of the 10 ohm resistors ...changed 2 that looked overheated at one time or another...
after a burn in tomorrow...i will run the amp on the voigts...
live and learn...
 

Sunnbobb

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wonder if something similar happened to sunnbob??
Was a thought, but nah, I forgot what it was.. lol. I run a cheap set of Memorex speakers for raw testing, then up to some Neumi's, and then over to the living room and the JBL L7's, or AR LST's. I did have a blown resistor in one of the L7 crossover tweeter circuits, but it just kept signal from getting to the tweeter. All fixed now.
 

gene french

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well, ran fine a few days...then back to the original problem....
sometimes comes on...sometimes not...
dcp board holding it down...
pretty sure something is breaking down on the control board...
interesting...but, understandable...50 year old components...
guess its time to order another wo control board...
and start from there....
 

wattsabundant

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If it's a stock board, one of the front end differential transistors is failing. On every PL14 board I've seen in the last couple years, Q3 or Q4 has failed. I'm pretty sure it's Q4. Replace both with MPSA93. Make sure to read the service bulletins for pin outs in the service manual.
 
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