Hi,
I acquired a cosmetically beautiful Nikko Alpha 220 for 30 bucks that the seller said needed a new transformer. He said the the guy before him had replaced caps and gone through it and told him it needed a new power transformer. He told me it would not turn on. Knowing me as I do I bought it anyway.
Got it home and took a look around under the hood. There clearly has been some work done on it - not all of which looks terribly well-done. Some of the solder joints are sloppy and there is some PCB trace lifting. I examined everything under a magnifying glass and could not see anything in particular. Put in a new fuse and tried the power and it immediately blew the fuse.
After unplugging it, I began checking solder connections on the bottom of the PCB boards with my DMM and found a pre-driver Q723 (2SC2275) was shorted between C and E. I pulled the transistor and checked it with my Atlas DCA55 and it said it was unrecognized/faulty. I checked it with my DMM and got no continuity between the pins. I pulled its complimentary transistor Q725 (2SA985) and it tested fine.
So, I went back to the board where I had pulled Q723 and am getting continuity between the empty C/E holes. That is not right is it?
I followed the pcb traces and those connect to a 9-pin yellow ribbon cable, two wires of which connect to Q727. The right most two ribbon connections had continuity with each other and the empty holes on Q723. I then touched the empty holes on Q723 and the prongs on Q727 and had continuity. Indeed, Q727 (2SD882) had continuity between each leg and with the ribbon connector and the empty holes for Q723. On the other side of the amp I did not get continuity at all between any of the mirror points.
So, I think I found at least one of the culprits. If this circuit is shorted as indicated it would blow the fuse right?
I downloaded the service manual from hifiengine but it is too big to upload here? I have attached two pictures of the area. One without text, the other with text.
Now, finding replacements for these will be a peach. Any suggestions would be much appreciated. Initial Google searches have been unsuccessful.
Thanks for any replies or suggestions I get.
James
I acquired a cosmetically beautiful Nikko Alpha 220 for 30 bucks that the seller said needed a new transformer. He said the the guy before him had replaced caps and gone through it and told him it needed a new power transformer. He told me it would not turn on. Knowing me as I do I bought it anyway.
Got it home and took a look around under the hood. There clearly has been some work done on it - not all of which looks terribly well-done. Some of the solder joints are sloppy and there is some PCB trace lifting. I examined everything under a magnifying glass and could not see anything in particular. Put in a new fuse and tried the power and it immediately blew the fuse.
After unplugging it, I began checking solder connections on the bottom of the PCB boards with my DMM and found a pre-driver Q723 (2SC2275) was shorted between C and E. I pulled the transistor and checked it with my Atlas DCA55 and it said it was unrecognized/faulty. I checked it with my DMM and got no continuity between the pins. I pulled its complimentary transistor Q725 (2SA985) and it tested fine.
So, I went back to the board where I had pulled Q723 and am getting continuity between the empty C/E holes. That is not right is it?
I followed the pcb traces and those connect to a 9-pin yellow ribbon cable, two wires of which connect to Q727. The right most two ribbon connections had continuity with each other and the empty holes on Q723. I then touched the empty holes on Q723 and the prongs on Q727 and had continuity. Indeed, Q727 (2SD882) had continuity between each leg and with the ribbon connector and the empty holes for Q723. On the other side of the amp I did not get continuity at all between any of the mirror points.
So, I think I found at least one of the culprits. If this circuit is shorted as indicated it would blow the fuse right?
I downloaded the service manual from hifiengine but it is too big to upload here? I have attached two pictures of the area. One without text, the other with text.
Now, finding replacements for these will be a peach. Any suggestions would be much appreciated. Initial Google searches have been unsuccessful.
Thanks for any replies or suggestions I get.
James
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It seems you must have started 2 threads on this... here’s my post in the other one.
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