OB-Xa - all EGs gone bad?

Pulling out your hair? Don't know what to do or where to go? Ask in here.
Forum rules
READ: VSE Board-Wide Rules and Guidelines

If your Help request has been solved, please edit your first post in order to select the Image Topic Icon to let others know your topic has been solved.
Don T
Supporting Member!
Supporting Member!
Posts: 296
Joined: Wed Oct 19, 2011 8:28 pm
Real name: Don
Gear: Roland SH-09, Korg Polysix, Moog Rogue, Realistic MG-1, Paia Fatman, Korg Monotron, and of course, my main instrument: Trumpet!
Location: Marietta, GA

Re: Any good synth techs? I blew a trimpot in my OB-Xa...

Post by Don T » Mon Sep 24, 2012 3:21 am

.....
Last edited by Don T on Mon Feb 04, 2013 7:50 pm, edited 1 time in total.
Don Taylor

Master of no trades, practitioner of many.
(Basically, this means I know just enough about a lot of things to get myself in real trouble)

User avatar
DesolationBlvd
Active Member
Active Member
Posts: 269
Joined: Tue Mar 06, 2012 1:24 am

Re: OB-Xa tunes same four oscillators sharp

Post by DesolationBlvd » Mon Sep 24, 2012 4:40 am

I thought about swapping voice cards. Problem is, I also don't know how to remove the voice cards. I removed all the screws, and pulled with a reasonable amount of force. Didn't come out.
Roland Jupiter-8 / SH-101 / RS-09 / MKS-30 / MKS-80
Moog Matriarch
Korg MS-20 Kit / ARP Odyssey FSQ
Boss CE-300
Yamaha DX7
Ensoniq SQ-80
Akai S5000
Elektron Analog RYTM

Don T
Supporting Member!
Supporting Member!
Posts: 296
Joined: Wed Oct 19, 2011 8:28 pm
Real name: Don
Gear: Roland SH-09, Korg Polysix, Moog Rogue, Realistic MG-1, Paia Fatman, Korg Monotron, and of course, my main instrument: Trumpet!
Location: Marietta, GA

Re: OB-Xa tunes same four oscillators sharp

Post by Don T » Mon Sep 24, 2012 9:29 pm

.....
Last edited by Don T on Mon Feb 04, 2013 7:50 pm, edited 1 time in total.

Steve Jones
Active Member
Active Member
Posts: 565
Joined: Wed Apr 23, 2008 10:40 pm
Real name: Steve
Location: Sydney
Contact:

Re: OB-Xa tunes same four oscillators sharp

Post by Steve Jones » Sun Sep 30, 2012 12:57 pm

Check the secondary power supplies for ripple with an oscilloscope. OB-Xa's are also notorious for rectifier failures.
Synthesizer service tech since 1982.
Synth parts and service, Sydney Australia.

User avatar
DesolationBlvd
Active Member
Active Member
Posts: 269
Joined: Tue Mar 06, 2012 1:24 am

Re: OB-Xa tunes same four oscillators sharp

Post by DesolationBlvd » Sun Sep 30, 2012 7:39 pm

Don T wrote:
DesolationBlvd wrote:I thought about swapping voice cards. Problem is, I also don't know how to remove the voice cards. I removed all the screws, and pulled with a reasonable amount of force. Didn't come out.

Check and make sure you have all the screws out, there is one in the middle of the connectors that's easy to miss, six screws total.

Yes, even after loosening the screws, it takes quite a pull to lift the card off the connectors. Place as many fingers as you can, preferably both hands, underneath the connector side only, and use your fingers to pry upward slowly. It will take a lot of pressure (apply from underneath the connectors only, never on the opposite side of the card). Slowy walk it up, the board will flex a little, but it can take a little flexing with no problem, as long as the pressure is evenly distributed.

Beware though, as soon as the card lets go, all the force you are using will be unleashed instantly! :D
Pretty much impossible at this point. Voice card one on the lower motherboard is trapped by a stripped screw head. They probably put too much epoxy to keep the screw in tight.

Is there a way to get rid of the wayward screw without risking the voice card?

Besides, I think the voices are aokay, and it's the autotune circuit that's screwed up.
Last edited by DesolationBlvd on Sun Sep 30, 2012 11:30 pm, edited 1 time in total.
Roland Jupiter-8 / SH-101 / RS-09 / MKS-30 / MKS-80
Moog Matriarch
Korg MS-20 Kit / ARP Odyssey FSQ
Boss CE-300
Yamaha DX7
Ensoniq SQ-80
Akai S5000
Elektron Analog RYTM

Steve Jones
Active Member
Active Member
Posts: 565
Joined: Wed Apr 23, 2008 10:40 pm
Real name: Steve
Location: Sydney
Contact:

Re: OB-Xa tunes same four oscillators sharp

Post by Steve Jones » Sun Sep 30, 2012 10:30 pm

Use a small pair of vice grips and turn the screw head to break the bond, then go back to a screw driver. I that doesn't work, put a small tube with some Blu Tac to seal it around the screw head and drill the top off the screw using a sharp drill bit on a battery screw driver at a fairly low speed. Do not break a voice card because of a stripped screw.
Synthesizer service tech since 1982.
Synth parts and service, Sydney Australia.

User avatar
DesolationBlvd
Active Member
Active Member
Posts: 269
Joined: Tue Mar 06, 2012 1:24 am

Re: OB-Xa tunes same four oscillators sharp

Post by DesolationBlvd » Sun Sep 30, 2012 11:35 pm

Steve Jones wrote:Use a small pair of vice grips and turn the screw head to break the bond, then go back to a screw driver. I that doesn't work, put a small tube with some Blu Tac to seal it around the screw head and drill the top off the screw using a sharp drill bit on a battery screw driver at a fairly low speed. Do not break a voice card because of a stripped screw.
The area is too tight for the vice grips - I tried, and I risk slamming into the high track trimmer.

As for the second one, what kind of tube?

Okay, maybe I have a short temper and a tendency to overreact.
Roland Jupiter-8 / SH-101 / RS-09 / MKS-30 / MKS-80
Moog Matriarch
Korg MS-20 Kit / ARP Odyssey FSQ
Boss CE-300
Yamaha DX7
Ensoniq SQ-80
Akai S5000
Elektron Analog RYTM

Steve Jones
Active Member
Active Member
Posts: 565
Joined: Wed Apr 23, 2008 10:40 pm
Real name: Steve
Location: Sydney
Contact:

Re: OB-Xa tunes same four oscillators sharp

Post by Steve Jones » Mon Oct 01, 2012 12:04 am

DesolationBlvd wrote:
Steve Jones wrote:Use a small pair of vice grips and turn the screw head to break the bond, then go back to a screw driver. I that doesn't work, put a small tube with some Blu Tac to seal it around the screw head and drill the top off the screw using a sharp drill bit on a battery screw driver at a fairly low speed. Do not break a voice card because of a stripped screw.
The area is too tight for the vice grips - I tried, and I risk slamming into the high track trimmer.

As for the second one, what kind of tube?

Okay, maybe I have a short temper and a tendency to overreact.
Just build up something around the screw with some plasticine or any kind of barrier to catch the metal fragments as you drill, or use a vacuum cleaner nozzle to pull them away while you are drilling. Jammed screws are pretty common on those machines, drilling is sometimes the only way. Just select an appropriate bit size that is slightly larger than the shaft of the screw and take it slowly.
Synthesizer service tech since 1982.
Synth parts and service, Sydney Australia.

User avatar
synthparts
Senior Member
Senior Member
Posts: 779
Joined: Sun Oct 09, 2011 12:05 pm
Location: SF Bay Area, CA
Contact:

Re: OB-Xa tunes same four oscillators sharp

Post by synthparts » Mon Oct 01, 2012 5:47 am

You can get a set of special drill bits for stripped screws, got mine at Sears... If you do end up damaging the voice card I have some (with or without chips)...
Vintage Synth Parts - http://www.synthparts.com

Don T
Supporting Member!
Supporting Member!
Posts: 296
Joined: Wed Oct 19, 2011 8:28 pm
Real name: Don
Gear: Roland SH-09, Korg Polysix, Moog Rogue, Realistic MG-1, Paia Fatman, Korg Monotron, and of course, my main instrument: Trumpet!
Location: Marietta, GA

Re: OB-Xa tunes same four oscillators sharp

Post by Don T » Mon Oct 01, 2012 6:19 am

.....
Last edited by Don T on Mon Feb 04, 2013 7:51 pm, edited 1 time in total.

User avatar
DesolationBlvd
Active Member
Active Member
Posts: 269
Joined: Tue Mar 06, 2012 1:24 am

Re: OB-Xa tunes same four oscillators sharp

Post by DesolationBlvd » Tue Oct 02, 2012 1:09 am

Okay, I just had a crazy idea:

The little file thingy on nail clippers. I file a groove into the bad screw head so I can use a flat screwdriver and get far more torque. A vacuum cleaner hose then sucks away filings. The screw seems to be pretty soft already. I might not need the stripped screw removers.

Much less risk of hitting anything important.

After I do this and get the screw free so I can swap voices 1 and 5, I will get back to you guys.
Roland Jupiter-8 / SH-101 / RS-09 / MKS-30 / MKS-80
Moog Matriarch
Korg MS-20 Kit / ARP Odyssey FSQ
Boss CE-300
Yamaha DX7
Ensoniq SQ-80
Akai S5000
Elektron Analog RYTM

User avatar
Zamise
Supporting Member!
Supporting Member!
Posts: 2352
Joined: Wed Oct 20, 2004 2:41 am
Gear: Rollhand P00
Band: Quantum-Source
Location: DenverMetroUSA, Quantum-Source.com
Contact:

Re: OB-Xa tunes same four oscillators sharp

Post by Zamise » Tue Oct 02, 2012 8:25 am

They do make reverse drill bits with socket heads on them specifically for removing stripped screws and broken bolt heads. Don't let the stripped screw hold you up too long. I'm watching this thread to see if you find an answer too, I've a card that was bad in my OB-SX, I fixed it but I think since it hasn't been used consistently like the others have it does not seem to want to always autotune the same as the others. I've tried re-aranging cards and adjusting the little pots and will get it sounding as close to perfect as I can but then I switch to another patch and the dang card will be way off again and that happens no mater which slot it is in, so I kind of gave up on it. Sadly, I flipped the bypass dip switch back to off, but it doesn't sound so bad in unison so I still flip it back on sometimes. I wonder if perhaps a previous owner of yours could have put salvaged or scavenged cards in yours. I've this feeling if the cards don't get the same amount of use over time then components don't degrade at quite the same rate thereby making tuning and autotuning h**l. Just a theory because the card I fixed actually sounds crisper and brighter than the others, I wish they all sounded like it instead of trying to get it to sound like the rest, but I think that isn't going to happen either on mine. Hope you get it figured out and if so please post back on how you accomplished it.
<ZQS> [....<OII>.....soundcloud player v2.42.....................link]

Don T
Supporting Member!
Supporting Member!
Posts: 296
Joined: Wed Oct 19, 2011 8:28 pm
Real name: Don
Gear: Roland SH-09, Korg Polysix, Moog Rogue, Realistic MG-1, Paia Fatman, Korg Monotron, and of course, my main instrument: Trumpet!
Location: Marietta, GA

Re: OB-Xa tunes same four oscillators sharp

Post by Don T » Wed Oct 03, 2012 6:16 pm

.....
Last edited by Don T on Mon Feb 04, 2013 7:52 pm, edited 1 time in total.

User avatar
DesolationBlvd
Active Member
Active Member
Posts: 269
Joined: Tue Mar 06, 2012 1:24 am

Re: OB-Xa tunes same four oscillators sharp

Post by DesolationBlvd » Sat Oct 06, 2012 11:00 pm

I got the bad screws out. Drilled them out and then used the screw remover. Had horrible luck - both screw heads broke off on me and I had to remove the shafts. The damage was only to the screws, the boards are scratched a little but otherwise fully functional.

Now that the bad screws are gone, I swapped the places of voice cards 5 and 6 with 2 and 3. The bad voices did not move - known good cards 2 and 3 wouldn't tune right, and suspect cards 5 and 6 tuned up okay.


Another oddity: There are some pins indicating a missing cable that could be connecting the upper and lower motherboards. They are to the left of voices 1 and 5. Could this be it?
Roland Jupiter-8 / SH-101 / RS-09 / MKS-30 / MKS-80
Moog Matriarch
Korg MS-20 Kit / ARP Odyssey FSQ
Boss CE-300
Yamaha DX7
Ensoniq SQ-80
Akai S5000
Elektron Analog RYTM

Don T
Supporting Member!
Supporting Member!
Posts: 296
Joined: Wed Oct 19, 2011 8:28 pm
Real name: Don
Gear: Roland SH-09, Korg Polysix, Moog Rogue, Realistic MG-1, Paia Fatman, Korg Monotron, and of course, my main instrument: Trumpet!
Location: Marietta, GA

Re: OB-Xa tunes same four oscillators sharp

Post by Don T » Sat Oct 06, 2012 11:09 pm

.....
Last edited by Don T on Mon Feb 04, 2013 7:52 pm, edited 1 time in total.

Post Reply