phase linear 400

[gene french]

and i took a small screwdriver and lifted every soldered wire to the board just to make sure they were not broken or frayed....
they were not....a couple had nasty solder blobs...which i addressed....but, did not find a problem....
and yes....the 400c board is very crude....george sent me a 14b driver board for parts....and it is light years ahead of these first boards....
joe, george, and sniff....all warned me about this old stuff....one guy actually said with these 50 year old amps you have an organized box of old parts....
i guess that is true...

 

[gene french]

And every wire


Read my other post ,,,,Bias Pot,,,,,on board
its not a output transistor problem at this point in time

yes sir, i did and understood....i did answer....

no sir....but, tomorrow i will check again....when i check the board again....



i am trying....lol
be patient with me...
lol

before i repower after working on anything....i always meter the bias transistors....always...and again after....i was told that it can be devastating if one of the legs break on these....i am trying to be extremely careful....

i also thumped....and examined both bias variable resistor pots....i have cleaned them several times with contact cleaner....maybe 4 or 5 times....
they do adjust....and are not too jumpy....a little movement goes a long way....but, it is linear and with patience you can get the offset and bias very close....within a few mv....

 

[MusicSteve]

no sir....but, tomorrow i will check again....when i check the board again....

Buss out all traces by the Bias Pot w a meter and ohm out the pot The problem could be in this area.
I buzzed out one side (good side) and compared it to the Bad sides which had a different reading ( a bunch of different spot on the board) I found the problem by comparing reading w my meter.

 

[George S.]

Buss out all traces by the Bias Pot w a meter and ohm out the pot The problem could be in this area.
I buzzed out one side (good side) and compared it to the Bad sides which had a different reading ( a bunch of different spot on the board) I found the problem by comparing reading w my meter.

Good advice! And Gene, you should be able to verify that trimpot is good or bad with a ohm meter.
If all else fails, note I left short insulation stubs for identification of wire connections for future possible reuse on that board. You may want to consider that as a option later on down the road. Later!

 

[gene french]

Buss out all traces by the Bias Pot w a meter and ohm out the pot The problem could be in this area.
I buzzed out one side (good side) and compared it to the Bad sides which had a different reading ( a bunch of different spot on the board) I found the problem by comparing reading w my meter.

yes, sir....i will certainly do that....i appreciate your suggestion....
very much...

 

[gene french]

Good advice! And Gene, you should be able to verify that trimpot is good or bad with a ohm meter.
If all else fails, note I left short insulation stubs for identification of wire connections for future possible reuse on that board. You may want to consider that as a option later on down the road. Later!

yes sir, i certainly will do exactly that...
and a bad pot could mess up my day....
i was told mouser has these pots in multiple turn....making them easier to adjust....
when i order my caps i just might do that....
this 4 fin is a april 1973 model....next year....50 years old..
yes sir, i did notice that....joe put a couple of 1304s in the box as well....i can easily put these two transistors back...and have a usable board....
i counted the wires and they have the same number as the 400c....do you reckon if worst comes to worst i could exchange my old board for the one you sent??
plausible????
joe said they are the same board basically....
thank you george of the jungle and music man!!!!

 

[Gepetto]

Geez Louise, 79 pages.

 

[George S.]

I know of no reason that 8 fin S1 board wouldn't work in your 4 fin S1. Seemed in very good condition overall, just needs recapped and everything checked. Mounting is different, but easily fixed.
You've got two more S1s coming. All the 8 fin parts will fit the 4s. Plenty of extra parts.

 

[George S.]

Geez Louise, 79 pages.

And she's not yet singing!

 

[gene french]

And she's not yet singing!

thanks for reminding me...i had almost forgot about that....
lol

 

[Gepetto]

both sides offset within 2mv of 0
left side bias at 350vm....pot has plenty of adjustment....
right side bias at 10mv...pot dont do squat...
checked diodes and resistors on back plane....
tomorrow scour the board, check diodes resistors and transistors again until the others machines get here....
all of the transistors that i put in / removed / swapped around check ok on the analog vm....
but, this definitely could be something breaking down....
stick a fork in me....i am done....
for today....lol

Don't mess around with the flyback diodes, they don't have anything to do with what you are chasing.

Take both driver transistors out of the right channel.

Take one of the left side drivers out, the one in the first column next to the transformer and move it to the 4th column.

You will now have a driver in column 2 and 4 starting from the transformer.

Put a GOOD PL909 transistor into column 1 and 3, bottom row.

Recheck your bias.

You only need the RCA410 or SJ2741 in column 2 and 4.

 

[Gepetto]

Now serving 80...

 

[gene french]

I know of no reason that 8 fin S1 board wouldn't work in your 4 fin S1. Seemed in very good condition overall, just needs recapped and everything checked. Mounting is different, but easily fixed.
You've got two more S1s coming. All the 8 fin parts will fit the 4s. Plenty of extra parts.

i think that i am going to order a new chassis from joe for the new wopl....and build an 8 fin with the spare parts...
what u think??? george of the jungle????

 

[Gepetto]

put the 8 fins on the new chassis and make one classy amp...

 

[gene french]

Don't mess around with the flyback diodes, they don't have anything to do with what you are chasing.

Take both driver transistors out of the right channel.

Take one of the left side drivers out, the one in the first column next to the transformer and move it to the 4th column.

You will now have a driver in column 2 and 4 starting from the transformer.

Put a GOOD PL909 transistor into column 1 and 3, bottom row.

Recheck your bias.

You only need the RCA410 or SJ2741 in column 2 and 4.

not only can you guys see inside the transistors...you can from 4000 miles away.....lol

yes sir, i can do that...and quite a handy piece of information....i have spares of the 909s....

i only have one spare 2741....and you sent me some 410s....

i will get a few more when i order the chassis....probably ps cap kit and led kit...

i will hold off ordering till i see more of a parts list i need...

thank you...you are very kind...

 

[gene french]

put the 8 fins on the new chassis and make one classy amp...

YES....exactly what i was thinkin....

 

[gene french]

i was hopin the new chassis came with fins....i didnt look that close....lol

 

[Gepetto]

Also check R19 in both channels, a 10 ohm resistor feeding Q8 collector. If those are open, your gain will be equal to 1.

 

[gene french]

they both show 10 ohm exactly....in circuit

 

[Gepetto]

Are you using that AstroAI to check your transistors?