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
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
Hi!
In the past I, have the same problem.
I, put MJ15024/025.
Why, because I, have it.
Still working fine!
Regards zeoN_Rider
In the past I, have the same problem.
I, put MJ15024/025.
Why, because I, have it.
Still working fine!
Regards zeoN_Rider
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
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
Hi!
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
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
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.
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.
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
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
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:'
http://www.diyaudio.com/forums/showthread.php?s=&threadid=30190&highlight=
Here's another very useful thread from 'Echowars:'
http://www.diyaudio.com/forums/showthread.php?s=&threadid=30190&highlight=
Hi!
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
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
Hi,
Does anyone know what could be used as replacements for the Q205 and Q206 biasing transistors on the right driver board?
Many thanks
Does anyone know what could be used as replacements for the Q205 and Q206 biasing transistors on the right driver board?
Many thanks
Are the pre drivers you mention Q203 and q204,
383 P1 and 383 N2 ?
I'm trying to find a sub for these.
383 P1 and 383 N2 ?
I'm trying to find a sub for these.
on my driver board, q205 is a ecg192a, q 206 subs to a nte 128, but a nte 159 also works
as does C3228, which also sub for Q207
as does C3228, which also sub for Q207
on the amp I am repairing, there is a mix of mj15024, 2sd424, 355-1 and ec6284,
that are the final output transistors.
fwiw.
that are the final output transistors.
fwiw.
Hi
this circuit looks like an old RCA circuit uprated for 200W. They used RCA-1B05 outputs and another for the driver and1E02/3 for the NPN/PNP pre-driver pair. They used to package pnp's in green and npn's in black TO-220, but the 1E02/3 I think were TO-66.
The SOA for the 1B05 was 150W to 140V, 1.07A. The MJ21193/4 match this but have 250W dissipation and much better gain linearity, so would give a performance improvement. You could probably use MJE15032/3 drivers and pre-drivers, because the gain would be higher (MJ21193/4 =25 at 8A, 1B05=15 min, 2A) but these are in TO-220.
John
this circuit looks like an old RCA circuit uprated for 200W. They used RCA-1B05 outputs and another for the driver and1E02/3 for the NPN/PNP pre-driver pair. They used to package pnp's in green and npn's in black TO-220, but the 1E02/3 I think were TO-66.
The SOA for the 1B05 was 150W to 140V, 1.07A. The MJ21193/4 match this but have 250W dissipation and much better gain linearity, so would give a performance improvement. You could probably use MJE15032/3 drivers and pre-drivers, because the gain would be higher (MJ21193/4 =25 at 8A, 1B05=15 min, 2A) but these are in TO-220.
John
Hi Todd!
do you also know the sub for the IC´s for the Front board IC101 - IC 106
Thanx in advance
Karl
do you also know the sub for the IC´s for the Front board IC101 - IC 106
Thanx in advance
Karl
another question to friends of this equipment: I tried a few times to get contact with EARL RAPP, he said, that he was one of the technicians who develped this item.
But never ot an answer. Maybe it works if someone from USA tries it?
BRGDS
Karl (Tandberg)
But never ot an answer. Maybe it works if someone from USA tries it?
BRGDS
Karl (Tandberg)
Hi M8's
I am new on this site but I repair for a lot of years Philips audio.
I am also a owner of a complete lab series. Past week my 578 amp. was blowing up. My pre-drivers are destroy and even some head drivers. So I have to ficker out what are the closed types that works. I have found out that for head drivers MJ15024 are good. The pre drivers I have used 2SA1452 and 2SC1625 both are 1 watt with high voltage. For Q205 I have use BC639. For Q207 BC640 and Q206 BC439 both are 0,5 watt by 80 volt. After replacement the 578 amplifier is as new. Good luck everybody.
Wim 😉
I am new on this site but I repair for a lot of years Philips audio.
I am also a owner of a complete lab series. Past week my 578 amp. was blowing up. My pre-drivers are destroy and even some head drivers. So I have to ficker out what are the closed types that works. I have found out that for head drivers MJ15024 are good. The pre drivers I have used 2SA1452 and 2SC1625 both are 1 watt with high voltage. For Q205 I have use BC639. For Q207 BC640 and Q206 BC439 both are 0,5 watt by 80 volt. After replacement the 578 amplifier is as new. Good luck everybody.
Wim 😉
- Status
- Not open for further replies.