phase linear 400

stetter said:
am I missing something but didn't AEebar's trouble start after he converted his case to 8 fin from 4 fin, I think he had no issues before that. Sounded like a lot of smearing of paste and what ever else he did
Click to expand...
No, the trouble started when I tightened up the thermal straps on the bias transistors and cranked the backplane board down one last time. Then I added in the second row of transistors and had the runaway bias issue. The 4 to 8 fin conversion was just a joke. All I did was mount in the small heat sinks. No trouble there. I did use a thin layer of silicone heat sink thermal grease, but I've been using that stuff for years and don't over apply. Just a thin, even layer. There was the slightest bit of overflow, but it was minimal and cleaned up with 5 minutes and a handful of q-tips.

I'm fairly certain that cranking down the thermal straps was the fatal error. We'll see what happens when I dive back into it. It was too nice in Chicagoland today to be inside. Took the Harley out for a few hours and did some yardwork instead of getting frustrated with the amp.
 
Gene, call them output transistors. The G means their "green" and lead free. The newest ones will be G. Get those.
 
George S. said:
Gene, call them output transistors. The G means their "green" and lead free. The newest ones will be G. Get those.
Click to expand...
thank you...25 years with a computer store kinda sticks with me...sorry...
what is the difference between the 95 and 96 output transistors?? both were specified...
 
Look up the data sheets, they're complimentary, NPN, and PNP, I forget which is which.
Hence we get fully complementary output with the WOAD back wall kits, whereas most all these amps were built quasi-complementary.
Joe explained the difference in a earlier post.
 
gene french said:
thank you...25 years with a computer store kinda sticks with me...sorry...
what is the difference between the 95 and 96 output transistors?? both were specified...
Click to expand...
NPN/PNP. they must be on the correct columns could your issue be that simple?
 
i think i understand...both used = fully complementary....
thank you!!!
George S. said:
Look up the data sheets, they're complimentary, NPN, and PNP, I forget which is which.
Hence we get fully complementary output with the WOAD back wall kits, whereas most all these amps were built quasi-complementary.
Joe explained the difference in a earlier post.
Click to expand...
i think i understand now...when both used they are fully complimentary.....
thank you...
 
gene french said:
that would help me understand why a matched set is not necessary in this config...
thank you !!!
Click to expand...
I’m all mixed up now... yours is stock backplane/quasi-comp right? If so yours are all the same except the bottom row. If full comp the +/- rails must be properly populated with 95/96’s
 
Gene, when we build a WOPL, each vertical row of transistors is one type, the next vertical row is the other type, and so on, alternating.
PL didn't do this on the quasi-comp amps, they mixed the types per verticle row.
On matching, just try to use the same batch or production lot# printed on the cases. No testing is necessary or needed
 
AngrySailor said:
I’m all mixed up now... yours is stock backplane/quasi-comp right? If so yours are all the same except the bottom row. If full comp the +/- rails must be properly populated with 95/96’s
Click to expand...
yes sir...you are spot on.... for now...this 4 fin is to remain stock with a recap, leds, power supply caps, and a dcprotect board....
i am just asking because i want another 400 or 700b to upgrade...as my next project....and i am trying to learn as much as i can....i am sure my questions seem elementary and bothersome ....for that i apologize......
beginning my search....if anyone has a few spart parts...for sale, keep me in mind...i need enough of a machine to put in the wo upgrades....
i do appreciate the advice!!!....and of course your time to answer!!!!
 
ABebar said:
No, the trouble started when I tightened up the thermal straps on the bias transistors and cranked the backplane board down one last time. Then I added in the second row of transistors and had the runaway bias issue. The 4 to 8 fin conversion was just a joke. All I did was mount in the small heat sinks. No trouble there. I did use a thin layer of silicone heat sink thermal grease, but I've been using that stuff for years and don't over apply. Just a thin, even layer. There was the slightest bit of overflow, but it was minimal and cleaned up with 5 minutes and a handful of q-tips.

I'm fairly certain that cranking down the thermal straps was the fatal error. We'll see what happens when I dive back into it. It was too nice in Chicagoland today to be inside. Took the Harley out for a few hours and did some yardwork instead of getting frustrated with the amp.
Click to expand...
Wait... maybe I’m speaker lubricated here but... did you install the second row with nothing but thermal paste? No mica or sil-pad? The case is the collector, that would be a dead short to ground no? Glad you had a good day for the motor scooter. I only had one so far here. Managed to find all my wiring gremlins on that ride too. Old ‘75 super glide in bad need of electrical work. The only
Electrical working in power to the ignition. TF she’s a kicker.
 
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