Philips 22AH578 - strange semiconductors

[audiomatic]

Hello;

I am currently working on a philips 22ah578 amplifier. The schematic of this monster can be found here:

http://www.mfbfreaks.nl/pdf/amps/578/22ah578.pdf

One channel is not working, I already figured out that some of the TO-3 type power transistors are dead.
I am very confused about the semiconductors which are used in this amp, never saw those before and I guess those were OEM made for this project.
The power and driver devices are Toshiba items, the power devices are labeled "355N1" and the driver devices are labeled "357N1" and "357P1". The small signal devices are mostly motorola, also having strange numbers.
Anyone else been working on such an amp before? Which common types can be used as replacements? I`ve read some information about the amp in this thread , so I`m not quite sure if simply taking MJ15003`s is the best way...

thanks, audiomatic

[jacco vermeulen]

MJ15003/4 no good, only 140Vce.
I wouldn't bet my money on Phili using exotic parts, they'd probably picked 2955/3055 if those could have handled the rails.
MJ15022/3 is more like it.

Mr power hour K-amps still has a lot of MJ21195/96: here

[zeonrider]

In the past I, have the same problem.

I, put MJ15024/025.

Why, because I, have it.

Still working fine!

Regards zeoN_Rider

[jaycee]

They are probably just "factory numbers" for common transistors. IMO this practice should be banned!

I'd agree, MJ15024 should be suitable as replacement outputs. As for the drivers (looks more like pre-drivers in that topology) what kind of packaging are they in? If they are TO-220 then MJE15032/3 will probably work. If they're TO-126 or similar i'd try MJE340/350

[zeonrider]

Sorry for MJ15025, forget it.

Driver stage , yes but MJE 15032/3 have deferent pin layout.

You must cross"C" & "B", on MJE15032/33.

Regards zeoN_Rider

[jacco vermeulen]

The drivers are TO220 and Japanese (green/black), A968/C2238 or earlier types.

Which likely makes the output devices 14MHz Toshiba 2SB600/2SD555.
As they'll cost in the order of $10/pc to replace, MJ15024/MJ15025 or the upgraded MJ21195/MJ21196 types would be the economical substitutes.

[audiomatic]

Hello;

thanks for all comments, and suggestions.
As far as i figured out right now the drivers seem to be OK.
I will try MJ15024 as pwr devices (first have to order some), and then we`ll see further.

thanks again

audiomatic

[spind]

Quasi-complementary amp here. The '357N2 and 357P1' transistors are the pre-drivers. The drivers and the outputs are all the same TO-3's --> the 355N1 npn's. (one pair of drivers and 3 pairs of outputs are all on the main heatsinks).

Here's another very useful thread from 'Echowars:'

Oscillating Power Supply....WTH?

[zeonrider]

Yes it is Q about curent for driving output stage.

At that time when amp. produced it hard to find semicond. for drivers.

Now it is another story.

regards zeoN_Rider

[jacco vermeulen]

Originally posted by spind
Quasi-complementary amp here.

Oops, yes.
I was looking at this picture, the green/black complementary devices should be the pre-drivers.
Makes it only 2SD555 for the outputs.