OBERHEIM SYNTH

I was able to repair Rene's Cyclone. Thank you Malte for your tip about the 7805 regulator! It was dead just as you said.

I looked at the circuit and noticed it was easy to mod the power entry so this never happens again. I added a forward biased 1N4003 diode where the power adapter feeds the board. I used a 1N4003 because I have a lot of them. A 1N4001 or similar will work as long as it can pass 500ma of current. If the wrong adapter is used the diode simply blocks the reverse voltage. The 5 volt regulator is now fed by approx 8.3 volts instead of the normal 9 volts. This should not hurt anything. I cut a trace on the backside of the board to make the installation look factory. There are detailed pictures of this mod in the photos area of the group. Click on a picture and hover over the text at the bottom of the page for details.

Next I read the Cyclone manual (this is the first I've ever seen a Perf-X unit) and on page 22 it stated that a memory mod could be performed to increase the number of presets from 32 to 100. Since I have quite a few Sony CXK58256P-10L I installed one after checking the datasheets to make sure it was compatible with a HY6264. The Cyclone came right up but it had an error code of J9 displayed. Next I tried a hard reset by holding down the Enter/Enable button and powering on. It came right up with preset 00 with 99 available. Whoohoo!!! I posted a pic in the photos area of the group showing the SRAM chip and 99 displayed on the LED's. I suppose if I had more time I could test the sysex dumps to see if 32 presets will work with the mod but I'm asking if anyone here has any experience with this first???

Feel free to ask any questions or even to give me a hard time for doing this.... Sorry for the long post. Now to send this puppy back to Rene. Fran

I have an Oberheim Cyclone that powers up ok but freezes very soon thereafter. I pretty much can't get anything out of it before it freezes or locks up. I also notice the number LED blinks a lot as well as most of the other LEDs. I believe the Play LED should blink but the others should not if correct. I've tried the hard reset, but that doesn't work either. If there was a problem with the regulator is wouldn't power on right?

A duff regulator could still enable the unit power on, then fail - say the regulator has a faulty solder joint or a crack..  The regulator heats up and the bad joint/ crack widens.

However could be another component.

Good luck 😊

Ps: you could try the Synth DIY and Synth Repair groups
________________________________
From: photoshootjapan@...<mailto:photoshootjapan@...>
Sent: ‎05/‎12/‎2013 04:37
To: oberheim@yahoogroups.com<mailto:oberheim@yahoogroups.com>
Subject: [oberheim] RE: Repaired and modded Rene's Perf-X Cyclone....

I have an Oberheim Cyclone that powers up ok but freezes very soon thereafter.  I pretty much can't get anything out of it before it freezes or locks up.  I also notice the number LED blinks a lot as well as most of the other LEDs.  I believe the Play LED should blink but the others should not if correct.  I've tried the hard reset, but that doesn't work either.  If there was a problem with the regulator is wouldn't power on right?

Cool stuff Fran - mods like yours along with re-caping old dried out electrolytic caps can do wonders for keeping old gear up & running.

Cheers,

WG