Yes and definitely yes.
Last edited:
SA-6500 II replacement transistors
- Thread starter lazyhaze
- Start date
If your using the one screw mounting method you will also need a shoulder bushing.
One per transistor.
https://www.mouser.com/ProductDetail/Keystone-Electronics/3049?qs=sGAEpiMZZMtnzxi/A5nO1dmIxgTN5BU2OMWD9Tx4CFg=
What exactly is the issue?
Edward Musci
Member
The unit works but the output is low on the right side. From the looks of it the resistor in front of the output trans had an issue( looks like it got hot). I tested the right side outputs - they failed test.
So I cant have the metal if the new trans touch the heatsink right?
So I cant have the metal if the new trans touch the heatsink right?
The metal tab on the outputs is connected directly to the center collector pin on the transistor.So they MUST be totally isolated from the electrically chassis grounded heatsink.
Edward Musci
Member
No blown fuses.
So the order of the install is --- heatsink , heatsink compound, mica, heatsink compound and then the output transisitor with the shoulder bushing.
Recommend replacing all 4?
So the order of the install is --- heatsink , heatsink compound, mica, heatsink compound and then the output transisitor with the shoulder bushing.
Recommend replacing all 4?
All four what? screws or transistors? I'd just replace the bad side. But thats up to you.
Edward Musci
Member
Ok. Sounds good. Avionic thanks again. Really appreciate it.
Ordering the stuff and will let you know how it goes.
Ordering the stuff and will let you know how it goes.
The Fuxtor
Addicted Member
what transistors are you going with?
Edward Musci
Member
On-Semi MJE15032 and the MJE15033
cbusuttil
Active Member
cbusuttil
Active Member
I didnt use thermal grease. instead I used some good , thermally conductive TO264 silicone insulators which will never dry out. MAKE SURE THAT THE TRANSISTORS ARE INSULATED FROM THE HEATSINK! .... cranked up the guts of this little amp to test the thermal dissipation for many hours. all is okay. I preferred my route as the wires offer some slight vibration suspension, which will prolong the pcb track's life. further more, it offers thermal isolation from the transistor to the pcb. This little SA 6500 II is a very neat little amplifier! at least it doesn't use those pesky unobtainable STKs like some similar wattage Technics use! hope this helps. - Chris
The Fuxtor
Addicted Member
Nice job, curious what you have for bias voltage?
Edward Musci
Member
Again to all that helped , Thank you. I reassembled the unit and it works great.
Sorry if I hijacked this thread.
Sorry if I hijacked this thread.
cbusuttil
Active Member
I used the service manual ... works fine.
The Fuxtor
Addicted Member
There is no adjustment pot, so I was curious what your bias settled to?
cbusuttil
Active Member
to be honest its hovering at around 60mV ... a bit high .... was thinking of tinkering with the resistors to drop it down to around 30mV ..... your thoughts?
The Fuxtor
Addicted Member
I got my bias around 25mv, but I think 30 would be a touch better.... I've left the unit on for a few hours at a time with a good amount of volume and the outputs were not super hot, at least not as hot as I would have expected. If I remember correctly, the bias resistors were 18k I think from schematic??
cbusuttil
Active Member
hmmm..... the odd thing is, that the outputs barely get warm at idle..... i could not find 18k on the schematic... what value did you use?
