phase linear 400

Gene, perhaps the pin outs on the plastic transistors are a issue. Pin outs changed between early and late GES93, GES97, and others.
Also note the specifics in the first Service Bulletin 1-76 regarding transistor type.
Taken from Don's site. Thanks to Don for making this available.
 

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George S. said:
Gene, perhaps the pin outs on the plastic transistors are a issue. Pin outs changed between early and late GES93, GES97, and others.
Also note the specifics in the first Service Bulletin 1-76 regarding transistor type.
Taken from Don's site. Thanks to Don for making this available.
Click to expand...
changes were noted mr george...
and right channel functions normally...i also have running machines to compare...this one is evil...
lol
 
it is playing....beautiful music mr. george...
i changed every diode and transistor on the left channel....
bias is still a bit high....370 to 390....
about the same when its playing....
cant get it lower....but i dont think its on the board unless the collection of pots i have are not good...
i had trouble finding two pots that were consistant and close...and quite a few were corroded beyond use...
still have a couple i can swap around if need be...
will let it play a few days open so i can keep fiddling with it...
i think this unit was parts and pieces somebody threw together....
not sure i believe this is a factory series one with a 240v transformer....
quite a challenge for me...
i do need another light board...but, i will wait until i am sure this thing will survive...
lol
i appreciate the hints and tips and advice!!!!
more than i can express....
 
i remember reading in the service manual....if q1 and q2 are changed its possible that the bias pots will be out of limits....
if so there is s 3.9k resistor that can be changed for less resistance to help setting the bias....
i will have to study more...
i dont believe there is a serious problem left...
 
Gene, none my 400 S2 dual primary transformer wiring looks like yours. No black primaries or secondaries other than the black buss bar ground wire. And your chassis has the sticker and no drillings I could see for the six screws that hold the Cylon meter sub plate to the chassis.
I'm thinking it truly is one of the first export 400's.
Think about all the people who tried to fix it in the past and didn't know what they were looking at. Glad you got it sort of working, and I'm sure you'll eventually get it spot on.
If you do pursue a old school transistor tester, I do really like my Sencore TF-151A. It is slick, and such a joy to use. The TF-151 is a cluster of point to point internal wiring, best avoided, while the later TF-151A uses a circuit board, dirt easy to recap, restore, and align.
Used the Sencore to test the plastic transistors on the modulation board of that Boonton RF Generator. Was easy to test for Beta and leakage, and it has higher current settings for power transistors that a battery powered tester can only rudimentary test. Yup, it plugs into the wall and has a transformer. Later!
 
George S. said:
Gene, none my 400 S2 dual primary transformer wiring looks like yours. No black primaries or secondaries other than the black buss bar ground wire. And your chassis has the sticker and no drillings I could see for the six screws that hold the Cylon meter sub plate to the chassis.
I'm thinking it truly is one of the first export 400's.
Think about all the people who tried to fix it in the past and didn't know what they were looking at. Glad you got it sort of working, and I'm sure you'll eventually get it spot on.
If you do pursue a old school transistor tester, I do really like my Sencore TF-151A. It is slick, and such a joy to use. The TF-151 is a cluster of point to point internal wiring, best avoided, while the later TF-151A uses a circuit board, dirt easy to recap, restore, and align.
Used the Sencore to test the plastic transistors on the modulation board of that Boonton RF Generator. Was easy to test for Beta and leakage, and it has higher current settings for power transistors that a battery powered tester can only rudimentary test. Yup, it plugs into the wall and has a transformer. Later!
Click to expand...
i am sure it is functional...just need to finesse the bias. ..i will look into the transistor tester...if i get one like yours. .i think you will guide ne through the work .
thanks for sharing mr george
 
Well, there's a NOS open box Sencore TF-151A on eBay right now. Several others.
I paid very little for mine, I waited. Got lucky and it wasn't blown up from hooking it to a live circuit.
If I wanted a nice one, that NOS one would be it.
Service manuals and schematics are online.
I think Lee has one.
Lee, what do you think of yours and is there something better that you've used?
 
I like mine. Not the last word on testers but plenty capable for what I do.
 
I feel the same way. To me a step up would be a curve tracer, which I really have no use for at this time.
 
If it is a PL14 board you are playing with Gene and cannot get the bias to go low enough, it is often that the bias circuit is the culprit.

You can try increasing R19 which should be a 680 or 470 ohm resistor on the PL14 board to 1K instead. That will allow extra base current for Q6 to help it come closer to saturation and bring down your high bias.
 
Gepetto said:
If it is a PL14 board you are playing with Gene and cannot get the bias to go low enough, it is often that the bias circuit is the culprit.

You can try increasing R19 which should be a 680 or 470 ohm resistor on the PL14 board to 1K instead. That will allow extra base current for Q6 to help it come closer to saturation and bring down your high bias.
Click to expand...
i think (even though i dont know bear s**t from apple butter) you are on the right track....
everything has been changed and checked out...
i read about this in the service manual...but refered to r17 on the 400c board....
i will do as you suggest.....and i thank you for your input....
 
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