I'm looking to buy some 2SD424 transistors for a Phillips AH-578 Power Amplifier Thanks everyone for your time.
Greetings" RM Thanks man it would be cost prohibitive because of shipping Thank you though.
To my Friend in Canada yes you can use On-Semi Devices however the sound is not as good grant you that is a subjective Topic.
Thanks to you both!!!!
To my Friend in Canada yes you can use On-Semi Devices however the sound is not as good grant you that is a subjective Topic.
Thanks to you both!!!!
Hi mr woofer,
I use both original Toshiba 2SD424 / 2SB554 and MJ21195 / MJ21196 in service and have for ages. The new On Semi transistors are actually better in that they maintain beta to higher currents. That makes the circuit more linear.
If these make a difference to the circuit behavior, the circuit is broken. You do have to check for oscillation and stability. Besides, any 2SD424 / 2SB554 you can find today are probably fakes and may well sound different.
Up to you!
I use both original Toshiba 2SD424 / 2SB554 and MJ21195 / MJ21196 in service and have for ages. The new On Semi transistors are actually better in that they maintain beta to higher currents. That makes the circuit more linear.
If these make a difference to the circuit behavior, the circuit is broken. You do have to check for oscillation and stability. Besides, any 2SD424 / 2SB554 you can find today are probably fakes and may well sound different.
Up to you!
Hi mr woofer,
If you're at all concerned with matching the outputs, new production of current devices would be the only reasonable choice.
Here are three data sheets that may help you. The Toshiba data sheet for the 2SD424 is harder to find.
From long experience, the process variations with the 2SD424 were much wider than the MJ2119x series. The MJ1502x series also has more process variation than the MJ2119x series. I also am curious to know why you would use the older MJ1502x series over the newer MJ2119x series.
These devices are close enough so that they do not impart a "sound" to an amplifier. The output topology and voltage amp determines how an amplifier sounds. That's keeping it stable.
If you're at all concerned with matching the outputs, new production of current devices would be the only reasonable choice.
Here are three data sheets that may help you. The Toshiba data sheet for the 2SD424 is harder to find.
From long experience, the process variations with the 2SD424 were much wider than the MJ2119x series. The MJ1502x series also has more process variation than the MJ2119x series. I also am curious to know why you would use the older MJ1502x series over the newer MJ2119x series.
These devices are close enough so that they do not impart a "sound" to an amplifier. The output topology and voltage amp determines how an amplifier sounds. That's keeping it stable.
I chose the MJ15024 due to my lack of ignorance into looking at the Transistors you suggested because I had one of these Amps back in the mid 80s
and that's what I had used subsequent to the change over from the then Motorolas the Toshibas' sounded better.
That being said I'm going to take your advice and use the Transistors you suggested I am a novice Hobbyist with a humble knowledge of the things we are discussing.
I thank you RM and many others on this site that take the time to help people like me.
Much appreciated!!!
Best Regards
John
and that's what I had used subsequent to the change over from the then Motorolas the Toshibas' sounded better.
That being said I'm going to take your advice and use the Transistors you suggested I am a novice Hobbyist with a humble knowledge of the things we are discussing.
I thank you RM and many others on this site that take the time to help people like me.
Much appreciated!!!
Best Regards
John
Hi John,
Often practical considerations are most important. One thing is true, transistors have improved steadily over time. When replacing transistors, you have to make sure the amplifier is stable - even with the same number parts.
If you blow an output, replace the drivers also. If a driver went, replace still further back. You may also have to replace the differential pair, if one was reverse biased it can damage it. These should be very tightly matched in beta.
I haven't got the schematic for that amplifier, but the servicing is pretty common. Watch out for open resistors, sometimes they only show a small black mark on the bottom (towards the PCB) when they fail. Trust nothing, prove everything. If you have a variac to power up slowly, use it.
Often practical considerations are most important. One thing is true, transistors have improved steadily over time. When replacing transistors, you have to make sure the amplifier is stable - even with the same number parts.
If you blow an output, replace the drivers also. If a driver went, replace still further back. You may also have to replace the differential pair, if one was reverse biased it can damage it. These should be very tightly matched in beta.
I haven't got the schematic for that amplifier, but the servicing is pretty common. Watch out for open resistors, sometimes they only show a small black mark on the bottom (towards the PCB) when they fail. Trust nothing, prove everything. If you have a variac to power up slowly, use it.
Thank you very much for your Insite on things well noted on my end and yes you are right about the Film Capacitors I like to use the Nichicon Film & Foil Capacitors I believe they are the QYX Series.
Many Thanks
John
Many Thanks
John
It has been probably a dozen years since I've worked on one of those. Seems like I used Panasonic ECQ.