phase linear 400

[gene french]

Are you using that AstroAI to check your transistors?

no...i use an analog voltmeter

 

[Gepetto]

no...i use an analog voltmeter

WHAT!!! Use the diode function on your AstroAI

 

[gene french]

the analog has a diode function ....
i just like it better....

 

[gene french]

and i double check the dvm and analog if i see what i think is a problem...

 

[MusicSteve]

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.

Gene
Make sure you take new Pic of the backpane and save it.

 

[gene french]

yes sir...i will

 

[gene french]

yes sir...i will

thank you

 

[MusicSteve]

thank you

Gene
Please post backplane pic w new config
When you bring power back up please post Voltages
I know this is Redundant ,
Report 1- DC Rail Voltages
2-Speaker protection Relay is On or Off
3- Dc offset w relay on, (Speaker output + to -) 3b- Relay off **** Measure before going into Relay board

Anybody else please add to list?

4. Update on what you did (your doing this already) but please add the Component # from Schematic

Thanks
Steve

 

[George S.]

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????

I think that would be very slick and probably lower your blood pressure. I think you'd have a big smile every time you looked at it!

 

[gene french]

Gene
Please post backplane pic w new config
When you bring power back up please post Voltages
I know this is Redundant ,
Report 1- DC Rail Voltages
2-Speaker protection Relay is On or Off
3- Dc offset w relay on, (Speaker output + to -) 3b- Relay off **** Measure before going into Relay board

Anybody else please add to list?

4. Update on what you did (your doing this already) but please add the Component # from Schematic

Thanks
Steve

yes sir....i am off to a late start this morning....did not sleep well....too much on my feeble mind...lol
i will document all....
where is the best place to read the rail voltages....since i cant do it from the outputs any more....lol...

 

[gene french]

Gene
Please post backplane pic w new config
When you bring power back up please post Voltages
I know this is Redundant ,
Report 1- DC Rail Voltages
2-Speaker protection Relay is On or Off
3- Dc offset w relay on, (Speaker output + to -) 3b- Relay off **** Measure before going into Relay board

Anybody else please add to list?

4. Update on what you did (your doing this already) but please add the Component # from Schematic

Thanks
Steve

dcprotect is out of circuit....i have the outputs disconnected....and am reading the voltages from the wires

 

[Gepetto]

yes sir....i am off to a late start this morning....did not sleep well....too much on my feeble mind...lol
i will document all....
where is the best place to read the rail voltages....since i cant do it from the outputs any more....lol...

the bulk caps.

 

[gene french]

the bulk caps.

i hate those things....lol
from the plus on top cap to chassis ground and the minus on the bottom to chassis ground....
just want to be perfectly clear and make sure i am doing exactly as you ask...
i have moved the 2741s and installed the 909s....they are two different batches but all on each side are a matched set....the 909s i used as drivers will be matched to the outputs in each channel....




also....i am going to inspect the bias pots before i power up....

 

[Gepetto]

i hate those things....lol
from the plus on top cap to chassis ground and the minus on the bottom to chassis ground....
just want to be perfectly clear and make sure i am doing exactly as you ask...
i have moved the 2741s and installed the 909s....they are two different batches but all on each side are a matched set....the 909s i used as drivers will be matched to the outputs in each channel....
View attachment 66025

View attachment 66026

also....i am going to inspect the bias pots before i power up....

Matching does not matter. They need to be good transistors and of the same type but matching is useless.

 

[Gepetto]

i hate those things....lol
from the plus on top cap to chassis ground and the minus on the bottom to chassis ground....
just want to be perfectly clear and make sure i am doing exactly as you ask...
i have moved the 2741s and installed the 909s....they are two different batches but all on each side are a matched set....the 909s i used as drivers will be matched to the outputs in each channel....
View attachment 66025

View attachment 66026

also....i am going to inspect the bias pots before i power up....

And put a PL909 in each location, not an XPL909

 

[gene french]

And put a PL909 in each location, not an XPL909

ok....i will do that....
the xpl chips were original to this 400...and i no longer have a full set of those....for both channels...only one channel and one spare...
i replaced the one side that had bad outputs with the pl909s....i read they were interchangable...but unique per channel...

 

[gene french]

ok....i will do that....
the xpl chips were original to this 400...and i no longer have a full set of those....for both channels...only one channel and one spare...
i replaced the one side that had bad outputs with the pl909s....i read they were interchangable...but unique per channel...

thank you...

 

[Gepetto]

They are, but you are debugging bias right now and would like to get to a place of similar behavior on each channel.

 

[gene french]

They are, but you are debugging bias right now and would like to get to a place of similar behavior on each channel.

understood....i replaced the xpl with pl as instructed...
dbtester operation...normal...
results....
rails at caps neg to chassis are plus and minus 85volts....
dc on output wires....zero
dc offset both sides zero
left bias without warmup 340mv
right bias without warmup 10mv

tested bias transistors (on the back wall) before and after....
tested good each side tested the exact same...

 

[gene french]

something on the right channel on the board....i would guess....and it would be just that....not even a swag....