Dr. Humboldt
Active Member
Thanks again everyone! It's now reassembled and will be packed for shipping! PM'd Bob! Thanks again!
Marantz 2275 fuse popping and no left channel
- Thread starter Dr. Humboldt
- Start date
-
- Tags
- fuse marantz 2275
OH, FWIW, the 2275 has a plug-in tone board.
The "latches" are delicate and I have actually seen the connector come a tad loose from (rough) handling and the unit to lose a channel.
The pre-out/main-in RCA on the back have switches built into them (you don't need jumpers) and those internal contacts can cause a channel drop out.
All the internal switches I've seen on RCA and 1/4 inch jacks are just a point-to-point contact with a little spring pressure. No actual "rubbing" involved so once they get whacky, it may be tricky to get them working. Deoxit may do it through chemical action, but I have seen spring contacts that just would not cooperate. You end up taking things apart and getting at the contact to polish it.
The "latches" are delicate and I have actually seen the connector come a tad loose from (rough) handling and the unit to lose a channel.
The pre-out/main-in RCA on the back have switches built into them (you don't need jumpers) and those internal contacts can cause a channel drop out.
All the internal switches I've seen on RCA and 1/4 inch jacks are just a point-to-point contact with a little spring pressure. No actual "rubbing" involved so once they get whacky, it may be tricky to get them working. Deoxit may do it through chemical action, but I have seen spring contacts that just would not cooperate. You end up taking things apart and getting at the contact to polish it.
Just wanted to come full circle on this and add some closure.
Right side amp module pins J705 & 706 had some burn marks on them .
Both right channel outputs were shorted ECB.
Replaced them along with new mica insulators and Dow 340 heatsink compound.
Tested all other components on the amp module and all were fine.
Brought up on dbt and set bias and dc offset on both amp boards.
Btw ,there is no reason on earth to be sticking bias test leads anywhere near the J pins as there are two convenient bias test point pins between the driver heatsinks on the 2275.
Next up was the "totally dead left channel" issue.
Swapping jumpers on preamp out to main in jacks showed that issue was in the preamp left side output as left amp module was fine.
Upon close examination of the easily removable PE01 preamp board a broken eyelet to foil trace was discovered at C38 4.7uf .
Trace was repaired and board re-recapped with Wima MKS2 poly films,Silmic II's and a Panasonic FC.
Pots and switch were deoxed.
Board was reinstalled paying close attention to gently snapping in the connection plug.
Everything works fine now.
However the dial lamp housing is badly melted and the remaining restoration needs to be done.
Bob
Right side amp module pins J705 & 706 had some burn marks on them .
Both right channel outputs were shorted ECB.
Replaced them along with new mica insulators and Dow 340 heatsink compound.
Tested all other components on the amp module and all were fine.
Brought up on dbt and set bias and dc offset on both amp boards.
Btw ,there is no reason on earth to be sticking bias test leads anywhere near the J pins as there are two convenient bias test point pins between the driver heatsinks on the 2275.
Next up was the "totally dead left channel" issue.
Swapping jumpers on preamp out to main in jacks showed that issue was in the preamp left side output as left amp module was fine.
Upon close examination of the easily removable PE01 preamp board a broken eyelet to foil trace was discovered at C38 4.7uf .
Trace was repaired and board re-recapped with Wima MKS2 poly films,Silmic II's and a Panasonic FC.
Pots and switch were deoxed.
Board was reinstalled paying close attention to gently snapping in the connection plug.
Everything works fine now.
However the dial lamp housing is badly melted and the remaining restoration needs to be done.
Bob