Search found 62 matches

by synthchaser
Thu Sep 17, 2020 10:54 pm
Forum: HELP!
Topic: Roland Juno 106 panel slider replacement
Replies: 2
Views: 110

Re: Roland Juno 106 panel slider replacement

Google "how does a voltage divider work" and you'll see why it doesn't matter if the pots aren't exactly the same values, or if they are replaced with different ones.
by synthchaser
Thu Sep 10, 2020 3:11 am
Forum: HELP!
Topic: Getting my OBXa going... help with removing JL Cooper midi kit!
Replies: 8
Views: 445

Re: Getting my OBXa going... help with removing JL Cooper midi kit!

Yeah, you'll need a 2732 EPROM. Each manufacturer had their own prefixes and most of the time, the only differences were the programming voltages. So you just need to find a chip that your EPROM programmer is compatible with... Then maybe download the datasheet for it and compare the pinout to the O...
by synthchaser
Wed Sep 09, 2020 7:08 am
Forum: HELP!
Topic: Getting my OBXa going... help with removing JL Cooper midi kit!
Replies: 8
Views: 445

Re: Getting my OBXa going... help with removing JL Cooper midi kit!

Sounds like you just need to burn an EPROM and you're good to go!
by synthchaser
Wed Sep 09, 2020 3:14 am
Forum: HELP!
Topic: Getting my OBXa going... help with removing JL Cooper midi kit!
Replies: 8
Views: 445

Re: Getting my OBXa going... help with removing JL Cooper midi kit!

It's been a while since I worked on one with JL Cooper MIDI, but to revert to stock most likely all you need to do is: 1. Unplug the daughterboard from the main board (I think 2 ribbon cables? 1 into processor socket as pictured and probably another into a DIP-14 socket which was for a CD4011) 2. Tr...
by synthchaser
Wed Sep 09, 2020 3:03 am
Forum: HELP!
Topic: Getting my OBXa going... help with removing JL Cooper midi kit!
Replies: 8
Views: 445

Re: Getting my OBXa going... help with removing JL Cooper midi kit!

There are a bunch of chips (the ones you listed included) that were on earlier revisions of the main board, but were removed by your revision.
by synthchaser
Thu Aug 06, 2020 11:03 pm
Forum: HELP!
Topic: Prophet 600 Note Triggering Issue
Replies: 3
Views: 1077

Re: Prophet 600 Note Triggering Issue

I think I may have showed this in one of my Prophet 5 repair videos, but a good reason is if the oscillator isn't stable, and it comes in and out of tune. Find the oscillator in question and attach a scope to the CEM3340 chip and you'll get to the bottom of it very quickly.
by synthchaser
Thu Aug 06, 2020 4:44 am
Forum: HELP!
Topic: Prophet 600 Note Triggering Issue
Replies: 3
Views: 1077

Re: Prophet 600 Note Triggering Issue

You have an oscillator that's out of tune. You hear it every 6th keypress because it's a 6 voice synth and it round robin assigns key presses to a voice.
by synthchaser
Fri Jun 12, 2020 7:25 pm
Forum: HELP!
Topic: Juno 106 voice issues
Replies: 5
Views: 1239

Re: Juno 106 voice issues

Ashe37 wrote:
Fri Jun 12, 2020 3:31 pm
'new digital versions'?
I would assume he means new surface mount clones.

To the OP, I would recommend using an oscilloscope to find what your actual problem is before guessing and changing stuff. You may wind up doing more damage than good.
by synthchaser
Fri Jun 05, 2020 6:23 pm
Forum: HELP!
Topic: ARP Odyssey 2800 No Sound
Replies: 3
Views: 847

Re: ARP Odyssey 2800 No Sound

They didn't want to make it easy on anyone, they're not labeled on the board. The test points are listed on the schematic, and you need to figure out where those parts correspond to on the PCB using the PCB layout diagrams.
by synthchaser
Fri Jun 05, 2020 6:20 pm
Forum: HELP!
Topic: Drumtraks Noisy Transformer
Replies: 9
Views: 1250

Re: Drumtraks Noisy Transformer

Most transformers that are available off the shelf have 1 or 2 secondary windings. This one has 4 secondary windings. (basically it's 2 separate center tapped transformers in one unit).

Mouser has 4,651 power transformers listed on their website. Only 11 of them have 4 secondary windings.
by synthchaser
Fri Jun 05, 2020 3:54 pm
Forum: HELP!
Topic: Drumtraks Noisy Transformer
Replies: 9
Views: 1250

Re: Drumtraks Noisy Transformer

If drilling holes bothers you, you can always make an adapter, like this adapter I have to mount a modern fan in a Memorymoog: https://synthchaser.com/product/memorymoog-fan-adapter-plate/ Mouser sells the 18VCT and 36VCT transformers. Based on what you said about your skillset, I'd recommend you ha...
by synthchaser
Fri Jun 05, 2020 3:36 am
Forum: HELP!
Topic: Drumtraks Noisy Transformer
Replies: 9
Views: 1250

Re: Drumtraks Noisy Transformer

I don't think you'll find a drop in replacement for this configuration. You should be able to put in 2 separate toroidal transformers, one with 18VCT secondaries and the other with 36VCT secondaries. In fact, I may consider doing this in mine...
by synthchaser
Fri Jun 05, 2020 3:17 am
Forum: HELP!
Topic: ARP Odyssey 2800 No Sound
Replies: 3
Views: 847

Re: ARP Odyssey 2800 No Sound

The service manual has 6 pages of test points listed, with illustrations of what waveforms you should be seeing on them with your scope. I'd check it out before trying to fix anything. And spraying these sliders is a bad idea, there are some good videos on how to clean them.
by synthchaser
Fri May 01, 2020 10:14 pm
Forum: HELP!
Topic: Arp Solus - square wave at TP11, but no sound from outputs
Replies: 1
Views: 902

Re: Arp Solus - square wave at TP11, but no sound from outputs

If you have an oscilloscope, and have the schematics, just follow the signal towards the output until you lose it.
by synthchaser
Sun Apr 12, 2020 12:56 am
Forum: HELP!
Topic: Please Help - "F" Note not playing
Replies: 3
Views: 959

Re: Please Help - "F" Note not playing

desmond wrote:
Sat Apr 11, 2020 12:56 am
Synthchaser? From Synthchaser.com? :)
I really enjoy your YouTube channel - thanks for doing that. 8-)
That's me, thanks!