Roland PA-250: guts and service notes [schematic]
- karul
- Cap Cooler
- mictester
- Old Solderhand
Information
Those big electrolytics look to be a bit bulging! You might want to change those soon.karul wrote:Roland PA-250, powered mixer and the art of internal wiring from the early 80's
"Why is it humming?" "Because it doesn't know the words!"
- karul
- Cap Cooler
Power supply electrolytics are fine, just the plastic caps (covers) on top are deformed. Esr and capacitance are still in the range. No bulge on the caps themselves. However, considering the age of the amplifier, they will be changed soon.mictester wrote:Those big electrolytics look to be a bit bulging! You might want to change those soon.
Last edited by karul on 22 Oct 2016, 22:28, edited 1 time in total.
First of all, apologies for resurrecting this super-old thread. I just acquired a Roland PA-80 which needs some work, and shares a service manual with the PA-150 and PA-250. Unfortunately the links to the manual posted previously have expired. I wonder if anyone reading this has a copy they wouldn't mind making available.
Thank you.
Thank you.
Seems I have to resurrect this thread again - because the Service Notes are not accessible on all 3 locations now.
Could someone please load them back up for me ? THANKS !!!
I got this PA-250 - worked a charm - put it away for 3 months - tried using and only getting very very faint signal from it. Headphone out is perfect. Using the 'finger humm test' on the signal connector into the power amp(s) gives full loud humm on the speaker(s) - so amp(s) are fine I think.
So - what's between the headphone take-off and the power amp in ??
ANSWER:
4 FETs stopping signal from mixer to both main out (and the main power amps) and monitor out if the input power is no good. Few components on the PSU board, ie a Diode, a cap 1uF/100V and two resistors and the cap went to 24nF hence the sense circuit never opened the FET's
Could someone please load them back up for me ? THANKS !!!
I got this PA-250 - worked a charm - put it away for 3 months - tried using and only getting very very faint signal from it. Headphone out is perfect. Using the 'finger humm test' on the signal connector into the power amp(s) gives full loud humm on the speaker(s) - so amp(s) are fine I think.
So - what's between the headphone take-off and the power amp in ??
ANSWER:
4 FETs stopping signal from mixer to both main out (and the main power amps) and monitor out if the input power is no good. Few components on the PSU board, ie a Diode, a cap 1uF/100V and two resistors and the cap went to 24nF hence the sense circuit never opened the FET's
Last edited by wernersaurus on 21 Jun 2022, 05:36, edited 2 times in total.
- karul
- Cap Cooler
service manual - pa-80_150_250
https://mega.nz/file/6oURFIAK#iLMRLtUJl ... Z7OaI1ogsA
ROLAND_PA-200_PA-400_SERVICE_NOTES
https://mega.nz/file/Lpd3FDya#MTh19PJkX ... VgYhxFTnGY
operation manual - pa250
https://mega.nz/file/GkVBya5Q#heGS3pOhl ... 1mxurIEUoU
https://mega.nz/file/6oURFIAK#iLMRLtUJl ... Z7OaI1ogsA
ROLAND_PA-200_PA-400_SERVICE_NOTES
https://mega.nz/file/Lpd3FDya#MTh19PJkX ... VgYhxFTnGY
operation manual - pa250
https://mega.nz/file/GkVBya5Q#heGS3pOhl ... 1mxurIEUoU
BRILLIANT BRILLIANT - THANK YOU !!!!!
- modman
- a d m i n
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Thanks so much, great thead Karul. Would just like to draw everybody's attention to the fact that you can edit your posts and the attachment limit has been expanded.
I also deleted some dead links and remarks about not being able to download etc from this thread to keep it readable. Keeping the mega links for now, but already re-attached the service notes to the first post.
thanks so much for you contributions!
I also deleted some dead links and remarks about not being able to download etc from this thread to keep it readable. Keeping the mega links for now, but already re-attached the service notes to the first post.
thanks so much for you contributions!
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