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Roland promars repair
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the19thbear



Joined: Apr 19, 2007
Posts: 150
Location: denmark

PostPosted: Mon Jun 17, 2019 10:56 am    Post subject: Roland promars repair Reply with quote  Mark this post and the followings unread

I got a roland Promars. I have had the jupiter 4 before and loved it, and repaired it a bit as well.

Ok, the Promars is pretty dead. I have sound, and keyboard tracking, but none of the controls do anything.
I opened it up, and the battery had leaked. I have now replaced the battery along with an opamp on the VCO board, that was dead. Also inserte an soledered in a new plug where the battery connected to the main board.

I checked all the connectors, and GND, +15, -15, +5 seems to go to all the right places, and the PSU is working.

The promars (it is pretty much the same as the jupiter 4 on the inside), is, as i mentioned, not responding to any controllers being turned.


Since NO controls work, I can pretty much rule out, dead ultiplexers. Since they are divided up between different controls. It seems unlikely that ALL the multiplexers should be dead at the same time.
The same with the AD/DA, which is also divided up between different AD/DA's. It also seems unlikely that they ALL should be dead at the same time.

That really leads me to the last thing that could be wrong. The CPU (8084).
THey are pretty cheap, but I cant seem to find any in my country, so I have to order one.

Please let me know what you think. Is my logic right?

Is there any way to check and see if the CPU is dead, with a normal digital voltmeter?
I dont have a oscilloscope. I would like to get one, but preferrebly something very cheap and easy to use.
Maybe something i can connect to a computer?
I guess i can rule out the possibility to use my soundcard as an oscilloscope for cpu stuff, since the clock freq is way higher that the sound carsd max freq (cpus=mhz, soundcard=khz).

i'm no electornics expert, but can def. find my way around a synth schematic:)

Thanks!
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Blue Hell
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Joined: Apr 03, 2004
Posts: 22884
Location: The Netherlands, Enschede
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PostPosted: Mon Jun 17, 2019 12:13 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hmm .. I'd expect the keyboard to go through the CPU as well ... does it have (working) MIDI in? At least that would be a CPU thing.
_________________
Jan
also .. could someone please turn down the thermostat a bit.
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the19thbear



Joined: Apr 19, 2007
Posts: 150
Location: denmark

PostPosted: Tue Jun 18, 2019 9:31 am    Post subject: Reply with quote  Mark this post and the followings unread

You are right. Hadn’t thought about that. The promars is pre midi.
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