Search found 5044 matches

by madtheory
Tue Jun 08, 2021 7:23 pm
Forum: HELP!
Topic: Poly800 first eight keys muddled with button actions
Replies: 15
Views: 3638

Re: Poly800 first eight keys muddled with button actions

Have you checked that the 8155 io chip is doing what it is supposed to? Off the data sheet? I assume you have the service manual? Because 8155 is programmable, you'll need the Poly 800 service manual to know exactly what it's supposed to be doing in this application.
by madtheory
Tue Jun 08, 2021 2:31 pm
Forum: General Synthesizers
Topic: Anyone recognise this David Sylvian synth?
Replies: 5
Views: 1276

Re: Anyone recognise this David Sylvian synth?

ppg_wavecomputer wrote:
Sun Jun 06, 2021 10:19 pm
desmond wrote:
Sun Jun 06, 2021 9:39 am
Hartmann Neuron

http://www.vintagesynth.com/misc/neuron.php
Quite surprised to see it there.

Stephen
I'm not. It gives a sound quite like some tape machines, say, the IBM dictaphone Holger Czukay used.
by madtheory
Thu Jun 03, 2021 2:50 pm
Forum: General Synthesizers
Topic: Buying a hardware synth advice
Replies: 7
Views: 1206

Re: Buying a hardware synth advice

They can all do the same range of sounds from weird to boring. The differences will be in the user interface and the sound quality, mainly of the filter but also the oscillators. It's really down to how good you are at synthesis, and trying out the real thing for yourself. Would you be able to get c...
by madtheory
Thu Jun 03, 2021 2:46 pm
Forum: HELP!
Topic: KORG POLY 800 LED Display not working
Replies: 1
Views: 507

Re: KORG POLY 800 LED Display not working

Sorry, but the first thing to check would be supply voltage to the display. Second thing would be ripple in the supply line caused probably by a failed capacitor. That would show up on a DMM too (scope is better).
by madtheory
Thu Jun 03, 2021 2:41 pm
Forum: HELP!
Topic: YAMAHA CS70M PSU repair
Replies: 13
Views: 1605

Re: YAMAHA CS70M PSU repair

I think a failing capacitor is also likely? But with the Zener there it is not the cause of the voltage increase... although it might have pushed the Zener out of range (damaging it) because one failure mode of electrolytic is to offset the DC voltage. You can check the caps visually, or remove them...
by madtheory
Thu Jun 03, 2021 2:37 pm
Forum: HELP!
Topic: Poly800 first eight keys muddled with button actions
Replies: 15
Views: 3638

Re: Poly800 first eight keys muddled with button actions

OK well I could be wrong but in that case it would seem obvious that the CPU has a problem. Get the data sheet and a logic analyzer and check that it matches up. Before replacing that though, I would look at replacing the EPROM where its instructions are stored. Because that's more likely to have ag...
by madtheory
Tue Jun 01, 2021 1:18 pm
Forum: HELP!
Topic: Poly800 first eight keys muddled with button actions
Replies: 15
Views: 3638

Re: Poly800 first eight keys muddled with button actions

Depends on where the MIDI comes in, does it go through that same buffer chip?
by madtheory
Tue Jun 01, 2021 12:24 pm
Forum: HELP!
Topic: Ensoniq Mirage DSK-8 novice
Replies: 2
Views: 583

Re: Ensoniq Mirage DSK-8 novice

If sampling is working and you can save them to disk, everything is OK. I just can't figure out how to create sounds or really how the wavesample wavetables work. Yes the terminology is confusing. As meatballfulton says you just have to work through the MASOS manual and try the examples. The confusi...
by madtheory
Sat May 29, 2021 4:35 pm
Forum: HELP!
Topic: Poly800 first eight keys muddled with button actions
Replies: 15
Views: 3638

Re: Poly800 first eight keys muddled with button actions

Cool! Please do keep us posted on your progress with it :)
by madtheory
Sat May 29, 2021 9:38 am
Forum: HELP!
Topic: Poly800 first eight keys muddled with button actions
Replies: 15
Views: 3638

Re: Poly800 first eight keys muddled with button actions

Ya good call on the decoupling caps. If that doesn't throw up an issue, you'd need a logic analyzer to see what is going in and out of the 40H240. It's possible for a chip to partially fail. You could take it out and test it on the bench to rule it out (rather than simply replacing it) because the r...
by madtheory
Fri May 28, 2021 8:12 pm
Forum: HELP!
Topic: Roland VP-9000 Internal power supply
Replies: 17
Views: 3016

Re: Roland VP-9000 Internal power supply

That makes sense. It's great that you're getting closer! I empathise with the itch :lol: I'm not sure about running it unloaded. Won't you have to work out the resistance to represent the equivalent load of the device?
by madtheory
Fri May 28, 2021 12:10 pm
Forum: Buyer's Guide
Topic: Multivox MX-3000
Replies: 14
Views: 7638

Re: Multivox MX-3000

Are you sure it's stereo? What's the resistance? Is it log or linear (you can measure for this)? What are the dimensions?

Armed with this info, you can refine your search.
by madtheory
Fri May 28, 2021 12:05 pm
Forum: HELP!
Topic: Poly800 first eight keys muddled with button actions
Replies: 15
Views: 3638

Re: Poly800 first eight keys muddled with button actions

The first thing to do would have been to check how it works via MIDI in. If it functions normally that way then you know it's not the CPU, it's somewhere between keyboard matrix and where that and front panel logic are input to CPU. Doesn't seem symptomatic of a buffer, as you have ascertained by re...