Discussion in 'Pioneer Audio' started by loweran, Nov 19, 2017.
Wow, I went back and re-read my thread and seems like I am rambling and just thinking out loud on my posts. Sorry if this is confusing and hard to follow. I will re-cap (pun intended) whats been done so far:
Visually inspected the set and found burned resistors
Tested all resistors diodes and drivers on the amp board. R34,R56, R58, R60 tested bad
Replaced the bad resistors
Asked a lot of dumb questions
Lifted the leads of the outputs and tested them. Right channel outputs were dead. This was the channel where the bad resistors were
Replaced outputs with On-Semi MJL3281 and MJL1302
Checked for bad solder joints and did some reflowing
Powered up on DBT and got no shorts and the relay clicked
Checked power board voltages. All checked good
Re-capped the power supply, pulled, tested, re-greased and reinstalled the large transistors on the power board
Powered up on DBT and got nothing
Fuse checked good but was loose. Tightened it up and cleaned it. Powered up on DBT fine
Checked power supply voltages and all checked out
Replaced Q11 - Q16 and Q19 - Q22 on the amp
Powered up on DBT
Display went dark and I traced it down to R104. It tested bad so I replaced. Display came back as normal
Set the idle current and tested on speakers. Sounds and functions great
Ordered the rest of the caps I need and am waiting on time to finish
Much more to do on this unit including cleaning the pots and switches, finishing the board work, replacing the power cord (it's got a crimped on temporary since someone cut the cord), building a new walnut case, and general clean up.
At this point I think I have too much in this unit. After all the orders, since I keep finding issues that require another order, I am up to $260 on it. Case will probably be another $20 in materials. I was thinking of selling this one when I am done, but I may second guess that and hold on to it for a little while.
Got more done last night. I finished all the boards except for the display board. Notes from the work:
The two 2AS912s in the eq board had desoldered themselves and left very little pad to work with. Replacing with KSA1220AYS requires drilling out the mounting holes. This combined with the bad shape the pads were in required scraping away the green board masking to copper and soldering them to the traces.
Everything else went fine and a quick test on the DBT showed now shorts and I get relay click.
The last board will be the display.
Done with the boards. Deoxit and lubed the controls, put the thing back together and am breaking it in. I am still a little worried about that phono amp transistor. It dont look so good. The connection seems solid though. Check out the pics and let me know what you think about that transistor.
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