My daily driven amps right side channel decided to fail this morning out of nowhere, basically idling. The output is low in level and very distorted.The DC protection does not engage which leads me to believe the failure is not catastrophic. The amp doesn't heat or smell funny either.
Before sending it off for service, I`d like to see if something could be done. I have schematics on hand, tools, DVOM but no real trouble shooting skills.
Where should I begin to look? Any help would be much appreciated .
TIA
Before sending it off for service, I`d like to see if something could be done. I have schematics on hand, tools, DVOM but no real trouble shooting skills.
Where should I begin to look? Any help would be much appreciated .
TIA
Update
I took the amp apart to do a visual inspection, doesn't look too good. There are considerable heat artifacts present on the right channels Pre Driver board (PDB) particularly in the area of TR 207, 208 and the 2 series resistors going to TR 207s collector along with zeners 202 203 204 and D D200.
What would cause that? Could those semiconductors have failed on their own or were they victims of an up stream/down stream fault?
There is evidence that those very components were replaced at sometime.
Comparing that board to it`s left channel counterpart shows some pcb heat discoloration but nowhere near as bad.
Would this be a good starting point to begin checking and what should I be looking for?
Both channels output transistors appear to be original FWIW
I took the amp apart to do a visual inspection, doesn't look too good. There are considerable heat artifacts present on the right channels Pre Driver board (PDB) particularly in the area of TR 207, 208 and the 2 series resistors going to TR 207s collector along with zeners 202 203 204 and D D200.
What would cause that? Could those semiconductors have failed on their own or were they victims of an up stream/down stream fault?
There is evidence that those very components were replaced at sometime.
Comparing that board to it`s left channel counterpart shows some pcb heat discoloration but nowhere near as bad.
Would this be a good starting point to begin checking and what should I be looking for?
Both channels output transistors appear to be original FWIW
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To me that just looks like a poor design with parts dissipating too much power - a recipe for failure. No heatsinks on any of those TO-126 devices, I can guarantee they have ran far too hot and one or more of them have failed
Hello Funny you should Say that, because of all the parts on that amp
that are discontunied, you can still Order that Board
for a wopping 325 Dolllars + shipping!!
that are discontunied, you can still Order that Board
for a wopping 325 Dolllars + shipping!!
Your approach is simply childish Petruv ... this internet crap not knowledge of electronics
Any of the outputs OPEN and the amplifier will play absolutely perfectly until pushed hard and eventually fail
any of the outputs Shorted then protection will not allow to start and fuses will be blown any way ...
Now for real electronics ...the specific amplifier has a number of issues to look at and please let us not forget that is an old amplifier One way or another expect it to be complicated .
The chance that you have an output blown is a total zero , also the chance that you have some other semiconductor blown is also very low BUT :
-there is plenty of protective resistors in various stages of the amplifier that either drift or go open
-Your major issue is that you expect soldering problems in the areas you pointed thermal stress
--Then you need to verify all voltage according to the schematic and beyond big psu there is another 4-5 fused voltages to be checked to be present but also operate properly . ( from regulation aspects = small capacitors )
--Expect also some trouble in the secondary psu where diodes fail kinda easy ...together with plenty of small capacitors that might also suffer from age and heat
That's about it
Kind regards
Sakis
The chance that you have an output blown is a total zero , also the chance that you have some other semiconductor blown is also very low BUT :
-there is plenty of protective resistors in various stages of the amplifier that either drift or go open
-Your major issue is that you expect soldering problems in the areas you pointed thermal stress
--Then you need to verify all voltage according to the schematic and beyond big psu there is another 4-5 fused voltages to be checked to be present but also operate properly . ( from regulation aspects = small capacitors )
--Expect also some trouble in the secondary psu where diodes fail kinda easy ...together with plenty of small capacitors that might also suffer from age and heat
That's about it
Kind regards
Sakis
Hi Sakis
I am hoping maybe you can help me i am having touble identifing a Zdiode
on my Yamaha PC2002M it has marking JT 85 and a small 5 JT 85 5
black with blue ring i can send you a picture og it
if you send me a email it would be of great help
*email removed by mod*
thank you Robert
I am hoping maybe you can help me i am having touble identifing a Zdiode
on my Yamaha PC2002M it has marking JT 85 and a small 5 JT 85 5
black with blue ring i can send you a picture og it
if you send me a email it would be of great help
*email removed by mod*
thank you Robert
Robert, You might not want to have your email addy out in the public like that. Ask Sakis to PM or send him your email address via PM, and take it from there.
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