Full Or Quasi Comp

[TapeHeadOne]

Hey guys,

I'm a bit slow on the uptake, but I am following this thread.

It seems my problems stem ti a larg extent from
- The fact the WOPL colour/wiring schematic has different colors and transistor identifications than the PL one
- Me 'trusting' the info and not paying enough attention
- Making an general ass of myself.

Importing the backplanes and such from the US to go full comp is a horrendously expensive proposition as I found out ordering the cap kit and Rev E board a few months back, and recently imports from the US have been stuck in customs for weeks without any apparent reason.

Now, what may have escaped my attention is mentioning the fire was caused in the WO 36 board. Some of the resistors and diodes in the rigt channel burnt. The print board has one burnt trace it seems, but I'm figuring it may be repairable.

Just in case you're asking, no It ain't my first rodeo. I have a small collection of vintage gear (and some cassette decks) I maintain and repair on a regular basis. I also have the required pro grade tools.

I'm currently trying to recover from a slight depression following previous events. I'm kind of fond of that old 400/II. So to be continued.

Peter

 

[TapeHeadOne]

Bonus question : did 400 series II ever leave the factory with NEC 2SD555 ?

Cheers,

Peter

 

[laatsch55]

Yes, often paired with 2SB600'S in full comp mode
.

 

[mlucitt]

Lee, this thread is on topic for this discussion on transistor gain:
The (4) drivers that originally came with the PL400 measured: SJ2741 #1 hFE=14, SJ2741 #2 hFE=3, NTE162 #1 hFE=12, NTE162 #2 hFE=24.

Looking forward to testing/comparing the replacement driver transistors...

The (16) MJ21196G's output transistors that I got from Joe all measured hFE=60-76. The mean being hFE=67.5, and the average hFE=65.187.

I thought about putting the outputs with the lower hFE on the bottom rows and work up the wall so the outputs with the highest hFE are on the top. Does this qualify me for transistor gain nerd of the week?

Oh, and I just got a new transistor tester.

 

[Bradrock]

Curve tracer???

 

[mlucitt]

Curve tracer???

I wish! Nah, just one of those cheap Chinese testers that tell you what the device is, the parameters, and that your battery is running low.

 

[laatsch55]

Lee, this thread is on topic for this discussion on transistor gain:
The (4) drivers that originally came with the PL400 measured: SJ2741 #1 hFE=14, SJ2741 #2 hFE=3, NTE162 #1 hFE=12, NTE162 #2 hFE=24.

Looking forward to testing/comparing the replacement driver transistors...

The (16) MJ21196G's output transistors that I got from Joe all measured hFE=60-76. The mean being hFE=67.5, and the average hFE=65.187.

I thought about putting the outputs with the lower hFE on the bottom rows and work up the wall so the outputs with the highest hFE are on the top. Does this qualify me for transistor gain nerd of the week?

Oh, and I just got a new transistor tester.

Yep, gain Nerd...

 

[TapeHeadOne]

Lee, this thread is on topic for this discussion on transistor gain:

No, it's about me being an idiot, but you go right on ahead.

 

[mlucitt]

No, it's about me being an idiot, but you go right on ahead.

I represent that remark!

 

[MarkWComer]

No, it's about me being an idiot, but you go right on ahead.

Wow... that guy fits right in, eh!

 

[mlucitt]

Wow... that guy fits right in, eh!

He is one of us, just not as... seasoned.

 

[Gepetto]

Most of us are 'full' of 'quasi' around here.

 

[MarkWComer]

He is one of us, just not as... seasoned.

 

[TapeHeadOne]

That's nice to read, guys...I think.

I've started a repair thread. You're help is greatly appreciated. There's some emotional value attached to this thing.

 

[WOPL Sniffer]

They ARE ticking time bombs until wopl'd.....

UNTIL WOPL'D CORRECTLY AND FULLY


BOOM

 

[orange]

I represent that remark!

Certainly!

 

[TapeHeadOne]

Yes, often paired with 2SB600'S in full comp mode
.

I'm currently reading service bulletin 1-80, which states :

2SD555 (NEC) was never used in production runs of 400 or 700 series but is a suitable replacement etc. etc.

However, sometimes the I and II series are mentioned separately, sometimes they just talk about 400 meaning both, and so forth.
This thing is doing my head in.

 

[laatsch55]

Yep, itll do that..

 

[Wayne]

“Full comp” and “quasi comp” refers to the output stage transistor makeup, “quasi” being all NPN transistors, “full” being a mixture of NPN and PNP. The driver circuit has to be in the proper configuration to feed which ever transistor makeup is used, and the two aren’t compatible. You can build the driver circuit to accommodate a quasi-comp backwall and revise it if you change to full-comp. When you order the driver board, all components for either build are included.

If you mix the two you’re likely to get asymmetric clipping, the negative (or positive, as the case may be) swings of the waveforms of your audio signal may not be presented to your output transistors.

IF you have an amp that was built by Phase Linear as “full comp,” you will make your driver circuit according to the full comp instructions.

Hey guys,
No one addressed the question.
Which is better sounding.
Thanks

 

[WOPL Sniffer]

we would not be building full comps if they weren't better... Higher output, superior sound.... It's answered.