Hi everybody!
This is my first post here, so please be patient 🙂
I've never fixed an electronic circuit, so any help will do here.
I have a Denon PMA-700AE integrated amplifier that refuses to turn on (relay clicks and then nada). I traced the problem to a faulty transistor in the power-amp section. It causes a short-circuit. I also observed 2 toasted resistors and a toasted Zener diode. There's also another "regular" diode nearby that I intend to replace, since it's very close to the fault's location.
My problem is that I can't find the replacement parts, since they're probably discontinued. I've spent hours in digikey.com trying to find components with the same characteristics, but since I know nothing, I can't tell what's important and what's not.
It would be very helpful if someone would shed some light and offer equivalents for the following parts (all data taken from the service manual):
Zener diode MTZJ2.7A T77 (datasheet: MTZJ2.7A DIODES Datasheet pdf - ZENER DIODES. Equivalent, Catalog)
Zener voltage 2.690 - 2.910 V, looks like a glass capsule
Diode: 1SS270A TE - Looks like a Hitachi diode that nobody stocks,
also in a glass capsule
Resistors: RS14B3AR22JNBST (There are identical resistors on the right channel, which was not harmed, and they read 1W R22J by Matsushita)
Any help, pointer, suggestion would be much appreciated.
Thanks !
- Barak
This is my first post here, so please be patient 🙂
I've never fixed an electronic circuit, so any help will do here.
I have a Denon PMA-700AE integrated amplifier that refuses to turn on (relay clicks and then nada). I traced the problem to a faulty transistor in the power-amp section. It causes a short-circuit. I also observed 2 toasted resistors and a toasted Zener diode. There's also another "regular" diode nearby that I intend to replace, since it's very close to the fault's location.
My problem is that I can't find the replacement parts, since they're probably discontinued. I've spent hours in digikey.com trying to find components with the same characteristics, but since I know nothing, I can't tell what's important and what's not.
It would be very helpful if someone would shed some light and offer equivalents for the following parts (all data taken from the service manual):
Zener diode MTZJ2.7A T77 (datasheet: MTZJ2.7A DIODES Datasheet pdf - ZENER DIODES. Equivalent, Catalog)
Zener voltage 2.690 - 2.910 V, looks like a glass capsule
Diode: 1SS270A TE - Looks like a Hitachi diode that nobody stocks,
also in a glass capsule
Resistors: RS14B3AR22JNBST (There are identical resistors on the right channel, which was not harmed, and they read 1W R22J by Matsushita)
Any help, pointer, suggestion would be much appreciated.
Thanks !
- Barak
BZX55C2V7 for the Zener diode
1N4148 for the regular diode (should be good enough)
The resistor is a 0.22 ohm resistor rated for 1W. Probably metal oxide type.
1N4148 for the regular diode (should be good enough)
The resistor is a 0.22 ohm resistor rated for 1W. Probably metal oxide type.
Thanks a lot Jaycee and OldDIY !
I have a few follow-up questions, if I may:
About the Zener diode - during my searches I came across TZX2V7A
which differs from BZX55C2V7 in dynamic resistance (100 Ohm vs. 85 Ohm) and reverse current (5 micro amps vs 10 micro amps). In addition, the Zener voltage of the TZX2V7A is 2.5-2.7 V, whereas the BZX55C2V7 reads 2.5-2.9 V (the original MTZJ2.7A reads 2.54-2.75 v). Could you please tell what the important specs are?
About 1N4148 - what do you mean by "should be good enough" is it less-suitable than the Hitachi?
OldDIY - what do you mean by "check both output transistors and drivers" ? What are the drivers? There are 6 transistors on the heatsink, I guess 3 per channel (D2083, B1383 and a smaller ones that I can't tell from looking at).
Again, sorry for nagging here... This is my first try...🙂
Thank you all !
- Barak
I have a few follow-up questions, if I may:
About the Zener diode - during my searches I came across TZX2V7A
which differs from BZX55C2V7 in dynamic resistance (100 Ohm vs. 85 Ohm) and reverse current (5 micro amps vs 10 micro amps). In addition, the Zener voltage of the TZX2V7A is 2.5-2.7 V, whereas the BZX55C2V7 reads 2.5-2.9 V (the original MTZJ2.7A reads 2.54-2.75 v). Could you please tell what the important specs are?
About 1N4148 - what do you mean by "should be good enough" is it less-suitable than the Hitachi?
OldDIY - what do you mean by "check both output transistors and drivers" ? What are the drivers? There are 6 transistors on the heatsink, I guess 3 per channel (D2083, B1383 and a smaller ones that I can't tell from looking at).
Again, sorry for nagging here... This is my first try...🙂
Thank you all !
- Barak
Hi everybody,
Well, I replaced the 2 big transistors, the diodes and the resistors. With much anticipation I connected all the connectors, plugged it in and.... Nothing! The problem persists!
The relay on the power board clicks, and the unit enters standby mode... Sooo frustrating.
I verified that the driver transistors are ok. i also compared resistance on parallel components between the left and the right channel, and got the same readings (without anything connected and no power, of course.
I'm back at square one... Any help/hint would be much appreciated.
Thanks!
- Barak
Well, I replaced the 2 big transistors, the diodes and the resistors. With much anticipation I connected all the connectors, plugged it in and.... Nothing! The problem persists!
The relay on the power board clicks, and the unit enters standby mode... Sooo frustrating.
I verified that the driver transistors are ok. i also compared resistance on parallel components between the left and the right channel, and got the same readings (without anything connected and no power, of course.
I'm back at square one... Any help/hint would be much appreciated.
Thanks!
- Barak
Check the outut from primary power supply and relay, check if the relay is getting return voltage (should be nearly 10V)..