Phase Linear 400 Series 2 Power Transistors

[Steve]

I have a PL 400 ser 2 amp. Managed to blow out the power transistors while replacing the power supply caps. The serial number on the amp is 4A26921. From what I have read this is an early production of the amp and the transistors are semi complimentary. I'm thinking replacement transistors would be as follows:

The 2 top rows: replace the F914 PL909s with MF 21195 or 95G transistors
The 3rd row: replace the F901 PL909s with MF 21196 or 96G transistors
The bottom row: replace the RCA 66546 CY7912 with Motorola SJ 2741 or MJ 1800 transistors However, a Phase Linear notice published recommended NEC 25D555 power transistors for the bottom row.

I like the amp and the sound but have not done any transistor work. So I need advice on whether I'm on track with the replacement transistors or suggestions as to what I should use. And what is a good honest (no fakes transistors) place to buy the transistors.

Steve

 

[mlucitt]

Your PL400 Series 2 is a middle release version, likely 1979 or early 1980. The PL400 Series 2 was released in 1978 and you could still buy one new in 1981 for $800.00.

If your amplifier has PL909 Output Transistors it is wired for quasi-complementary operation. The current replacement for these (12) transistors are the NPN ONSEMI MJ21196G devices. I recommend replacing all (12) Output Transistors at the same time using Sil-Pads instead of grease and mica, which will need to be removed.

The bottom row of (4) transistors in your amplifier are RCA 66546 Driver Transistors and should be retained unless they have been blown, which does not occur often. There are no replacements for these Driver Transistors. Time has proven that they are superior to NEC 2SD555, Motorola SJ2741 or any other devices in this application.

You can find these authentic transistors at Mouser:
https://www.mouser.com/ProductDetail/onsemi/MJ21196G?qs=HVbQlW5zcXW9Hdwg53oKog==
Or, there are folks here on the Forum that can send them directly to you along with the Sil-Pads.
Click my username to the left of this dialog box and send me a Private Message (PM) if you would like more information about these transistors.

 

[gene french]

what would be preferred driver transistors using the '96 outputs in the series 1 pl400...please...
thanks

 

[laatsch55]

RCA 410'S

 

[laatsch55]

The RCA 66546 are rebranded 410's..

 

[mlucitt]

In my humble opinion, the RCA 410 or RCA 66546 (they are the same devices) driver transistors are the best for that application.
Others may have a different opinion.
I have some if you need them.

(Lee is faster on the keyboard than I am.)

 

[gene french]

ok...thanks!!!

 

[gene french]

In my humble opinion, the RCA 410 or RCA 66546 (they are the same devices) driver transistors are the best for that application.
Others may have a different opinion.
I have some if you need them.

(Lee is faster on the keyboard than I am.)

i have a bunch of odds and ends.. from the two wopls...and mr. george sent me some stuff...i bought a set of 96s...for when i run out of xpls and fs...also when the repairs to stock gets out of hand i have enough 96s for 2 units...i have a few 410s...546s...and 41s....
just planning ahead....i appreciate your offer...but am good for now...cant some 96s be used as 2 drivers...or maybe all 4??

 

[gene french]

i have enough for 2 wopl backplanes...just need the 95s...to complete 2 more upgrades!!!

 

[mlucitt]

i have enough for 2 wopl backplanes...just need the 95s...to complete 2 more upgrades!!!

Mouser has them, about $9.00 each:
https://www.mouser.com/ProductDetail/onsemi/MJ21195G?qs=HVbQlW5zcXWtNoqJbrBgZA==

 

[gene french]

thank you!!
i try to buy from mr. joe when i can...
he has done a bunch to help everybody!!!

 

[Steve]

Your PL400 Series 2 is a middle release version, likely 1979 or early 1980. The PL400 Series 2 was released in 1978 and you could still buy one new in 1981 for $800.00.

If your amplifier has PL909 Output Transistors it is wired for quasi-complementary operation. The current replacement for these (12) transistors are the NPN ONSEMI MJ21196G devices. I recommend replacing all (12) Output Transistors at the same time using Sil-Pads instead of grease and mica, which will need to be removed.

The bottom row of (4) transistors in your amplifier are RCA 66546 Driver Transistors and should be retained unless they have been blown, which does not occur often. There are no replacements for these Driver Transistors. Time has proven that they are superior to NEC 2SD555, Motorola SJ2741 or any other devices in this application.

You can find these authentic transistors at Mouser:
https://www.mouser.com/ProductDetail/onsemi/MJ21196G?qs=HVbQlW5zcXW9Hdwg53oKog==
Or, there are folks here on the Forum that can send them directly to you along with the Sil-Pads.
Click my username to the left of this dialog box and send me a Private Message (PM) if you would like more information about these transistors.

The recommendation from mlucitt is to replace all 12 transistors with 96Gs which are NPNs. That would switch the top 8 transistors which are currently PNPs (F914 PL901). How does that affect the operation of the circuits?

 

[laatsch55]

Ok, columns of transistors, which are in the same plane as the heatsinks, 1st column, what do you have?
2nd column, what do you have.
Columns= vertical
Rows =. horizontal

 

[Steve]

Ok, columns of transistors, which are in the same plane as the heatsinks, 1st column, what do you have?
2nd column, what do you have.
Columns= vertical
Rows =. horizontal

The first column on the left has:
2 F914 PL909 top two rows
1 F901 PL909 third row
1 RCA 66546 bottom row

That same transistor numbering and placement is the same each of the four columns So the top two rows in the 6 columns all have F914 transistors, the third row in all columns the F909 transistors, and the bottom row in all columns the RCA 66546 transistors.

 

[Steve]

The first column on the left has:
2 F914 PL909 top two rows
1 F901 PL909 third row
1 RCA 66546 bottom row

That same transistor numbering and placement is the same each of the four columns So the top two rows in the 4 columns all have F914 transistors, the third row in all columns the F909 transistors, and the bottom row in all columns the RCA 66546 transistors.

 

[laatsch55]

It is a quasi amp and should not have any PNP's as outputs. The bottom row of 66546's tells you it's not a fully comp amp.

 

[mlucitt]

I explained to him in a PM that the F means Fairchild Corp. All the outputs are relabeled by Phase Linear to read PL909 and the 914 and 910 are date codes 9=1979 and 10 and 14 are weeks of manufacture.
I believe this is true because we used Fairchild semiconductors in the Navy.

 

[Gepetto]

thank you!!
i try to buy from mr. joe when i can...
he has done a bunch to help everybody!!!

And they are not $9 each...

 

[mlucitt]

And they are not $9 each...

$8.13 each, if you buy from Mouser plus the $7.99 shipping...
Joe has a better price.