Roland PA-250: guts and service notes  [schematic]

Tube or solid-state, this section goes to eleven!
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karul
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Post by karul »

Roland PA-250, powered mixer and the art of internal wiring from the early 80's

there are no photos of this mixer on the web, so I thought maybe it's not a bad idea to post some ...
operation manual - pa250.pdf
(1.29 MiB) Downloaded 160 times
ROLAND_PA-200_PA-400_SERVICE_NOTES.pdf
(10.87 MiB) Downloaded 187 times
service manual - pa-80_150_250.pdf
(4.63 MiB) Downloaded 337 times
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peterc
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Post by peterc »

Loved these mixer amps, used one for many years, 250 that is

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Post by mictester »

karul wrote:Roland PA-250, powered mixer and the art of internal wiring from the early 80's
Those big electrolytics look to be a bit bulging! You might want to change those soon.
"Why is it humming?" "Because it doesn't know the words!"

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Post by karul »

mictester wrote:Those big electrolytics look to be a bit bulging! You might want to change those soon.
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.
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Last edited by karul on 22 Oct 2016, 22:28, edited 1 time in total.

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Post by karul »

peterc wrote:Loved these mixer amps, used one for many years, 250 that is.
It sounds quite nice.

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Post by karul »

Van Der Funk with Roland TR 808, TR 909 drum machine with RE-501 and PA-250


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Post by backlash »

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.

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Post by backlash »

Awesome, thank you!

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Post by wernersaurus »

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
Last edited by wernersaurus on 21 Jun 2022, 05:36, edited 2 times in total.

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Post by wernersaurus »

BRILLIANT BRILLIANT - THANK YOU !!!!!

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Post by modman »

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!
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