Full Or Quasi Comp

TapeHeadOne

New Around These Parts
Joined
Jul 30, 2019
Messages
39
#21
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
 

mlucitt

Chief Journeyman
Joined
Jun 24, 2011
Messages
1,415
Location
Jacksonville, FL
#24
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.
 

laatsch55

Administrator,
Staff member
Joined
Jan 14, 2011
Messages
57,124
Location
Gillette, Wyo.
Tagline
Halfbiass...Electron Herder and Backass Woof
#27
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

New Around These Parts
Joined
Jul 30, 2019
Messages
39
#34
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.
 

TapeHeadOne

New Around These Parts
Joined
Jul 30, 2019
Messages
39
#37
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.
 
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