replacement predrivers for PL400 series 2

[Dr12volt]

anyone got any suggestions on replacements for the RC410 predrivers? I have heard that they, the SJ2741, and 66546 have all been discontinued. surely there is a comperable replacement if not a better part? thanks for your input.

 

[mlucitt]

These RCA 410 NPN driver transistors basically set up the bias and signal conditioning for the NPN Output Transistors, they do not have to work very hard, that is why they last so long. The RCA 410 was selected because it was a common 200V transistor, with low gain ( hFE 30-90), and low bandwidth so less likely to oscillate. It is in the Motorola 2N5840 Family of TO-3 devices.
My understanding is the SJ2741 was used on the earlier PL400 amps and the RCA 410 showed up during the majority of production. In the later years and during Series II production, the RCA 66546 was used but the consensus here is that the RCA 66546 is a RCA 410 with a different part number, there is no Datasheet for the RCA 66546 that I could find. I have attached the datasheet for the RCA 410 transistor (Line No. 15).

There is no exact or superior replacement for the RCA 410 or RCA 66546. I have seen MJ15024 in the Driver position and some other oddballs, best to go with matched RCA devices. Many of the folks on the forum have them if you need a set of four.

 

[Gepetto]

And remember, you only need them in 2 positions on quasi comp amps. The locations that I shared with you. So for 2 amps, you only need 4, not 8.

Most amps have them in the bottom row and rarely go bad. Test them and if they are good, use them.

 

[Gepetto]

anyone got any suggestions on replacements for the RC410 predrivers? I have heard that they, the SJ2741, and 66546 have all been discontinued. surely there is a comperable replacement if not a better part? thanks for your input.

And you don't want a better part, there are many better parts.
Nobody makes transistors as bad as these were anymore, the technology has moved on.

The MJ411 comes close but even those are not available new.

 

[Dr12volt]

These RCA 410 NPN driver transistors basically set up the bias and signal conditioning for the NPN Output Transistors, they do not have to work very hard, that is why they last so long. The RCA 410 was selected because it was a common 200V transistor, with low gain ( hFE 30-90), and low bandwidth so less likely to oscillate. It is in the Motorola 2N5840 Family of TO-3 devices.
My understanding is the SJ2741 was used on the earlier PL400 amps and the RCA 410 showed up during the majority of production. In the later years and during Series II production, the RCA 66546 was used but the consensus here is that the RCA 66546 is a RCA 410 with a different part number, there is no Datasheet for the RCA 66546 that I could find. I have attached the datasheet for the RCA 410 transistor (Line No. 15).

There is no exact or superior replacement for the RCA 410 or RCA 66546. I have seen MJ15024 in the Driver position and some other oddballs, best to go with matched RCA devices. Many of the folks on the forum have them if you need a set of four.

thank you for you infomation

 

[Dr12volt]

And remember, you only need them in 2 positions on quasi comp amps. The locations that I shared with you. So for 2 amps, you only need 4, not 8.

Most amps have them in the bottom row and rarely go bad. Test them and if they are good, use them.

thanks. I will ask my technician if they are are good. He may just be wanting to replace everything to make sure its all up to date.

 

[Gepetto]

thanks. I will ask my technician if they are are good. He may just be wanting to replace everything to make sure its all up to date.

That is what everyone does that retains quasi comp, they rarely go bad and are no longer available as new.

If you want everything as new technology, convert to full comp and pick up the advantages of better SQ as well.

 

[WOPL Sniffer]

WOPL that thing and be done with the old junk.

 

[mlucitt]

Send the old RCA 410's to Sniffer, he likes them for target practice...

 

[WOPL Sniffer]

Send the old RCA 410's to Sniffer, he likes them for target practice...

Oh hell yeah. I can hit em at ten paces with the gat. Then I use them for incense burners.

But, don't send them to me, I sent buckets of them to others here that may need them more than me.

 

[wattsabundant]

...Or send them to me and I'll eventually put them in someone's amp who doesn't want to convert to full comp. The important thing is you do not sub "superior" transistors for the applications Joe has called out above. Doing so creates oscillations that can not be cured.