OBXA Tandulum caps.

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.
Skiroy
Newbie
Newbie
Posts: 94
Joined: Thu Jun 09, 2011 3:38 am

OBXA Tandulum caps.

Post by Skiroy » Thu Jan 12, 2012 7:48 am

I keep hearing these need to be changed often but where are they? I only see radial electrolytic. What do they look like?What are their specs?

User avatar
sequentialsoftshock
Synth Explorer
Synth Explorer
Posts: 2413
Joined: Thu Jan 28, 2010 1:57 am
Real name: Zayne
Gear: Pro~One, MS20, MPC60, Aalto, Volca Beats, Volca Keys, Beatstep, Casio MT18, BitOne (sorta), Circle, Orbit 3, K5, Stylos, Univox Hi Flier, iPad
Band: Echo & Liora
Location: Paris / Philadelphia
Contact:

Re: OBXA Tandulum caps.

Post by sequentialsoftshock » Thu Jan 12, 2012 1:48 pm

Didn't you post that Eric said it just needed a calibration in your other thread about this..?
bonne chance

Skiroy
Newbie
Newbie
Posts: 94
Joined: Thu Jun 09, 2011 3:38 am

Re: OBXA Tandulum caps.

Post by Skiroy » Thu Jan 12, 2012 5:02 pm

Yes but.
1. I am just educating myself for the future.
2. He suggested for me to rebuild the power supply and he thought based on our conversation it is something I can more than handle.
3. He said it all sounds like its functioning and to do the calibration,but if it doesnt sound as I want then to possible recap the output stage caps and tandulums. I am going to do the PSU and we agreed that I will attempt to calibrate it myself. If I cant handle it I will drive up to him where he will give it a full comb over and I will probably let him do any voice card recapping.

He is a really awesome guy and offered to educate me in case I need to do anything in the future. He sounds like he is willing to do the work but doesnt have to do it and is more than happy to get me up to par to do it myself. People like him are rare and I will try and allow him to do as much as I can work out because he deserves it,but I also want to continue to educate myself for the future if I am going to keep this board. By the way the same reason why he educated himself to work on these things.He told me he isnt a EE and that he is just a keyboard player that got enough info from people to work on them himself as necessity.

Dont get me wrong he is very knowledgeable and good at what he does and I would highly recommend him to anyone on here.

User avatar
madtheory
Supporting Member!
Supporting Member!
Posts: 5366
Joined: Mon May 01, 2006 12:45 pm
Real name: Tomas Mulcahy
Gear: Wurlitzer Opus 1536, Model F, Morovdis Arpeggiator, Maplin My First EQ, Jeff Wayne Thunderchild rack, Thermostat, Buck Owens' Moog.
Location: Cork, Ireland
Contact:

Re: OBXA Tandulum caps.

Post by madtheory » Thu Jan 12, 2012 5:41 pm

Google spell check won't pick up your misspelling, so here you go:
http://en.wikipedia.org/wiki/Tantalum_capacitor

Makes sense to just do those caps alright, as he said.

User avatar
cornutt
Moderator
Moderator
Posts: 2117
Joined: Sun Dec 02, 2007 6:03 am
Gear: 6th
Location: Rocket City USA
Contact:

Re: OBXA Tandulum caps.

Post by cornutt » Thu Jan 12, 2012 7:40 pm

Generally, tantalums look like random blobs of plastic, as opposed to the neat cylindrical shape of electrolytics. Here is an example, from Mouser's listings, of what one looks like:

http://www.mouser.com/ProductDetail/AVX ... jbKaTQc%3d

I'm going to go against the conventional wisdom and say that, if you're going to replace the existing tantalums, you should replace them with modern dry tantalums. The secondary characteristics will probably be closer to the orignals than electrolytics would. And dry tants should outlast electrolytics.

Do make sure you get them in the right way. :o
Switches, knobs, buttons, LEDs, LCD screens, monitors, keys, mice, jacks, sockets. Now two joysticks!

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

Re: OBXA Tandulum caps.

Post by synthparts » Fri Jan 13, 2012 1:52 am

If you've never repaired a synth before I would not start out mucking around with the power supply in an OB-Xa... Have him do it. If he's worked on any Oberheims he should know about the tantalums and other power supply issues like the rectifiers and regulators. Have him do it.
Vintage Synth Parts - http://www.synthparts.com

User avatar
sequentialsoftshock
Synth Explorer
Synth Explorer
Posts: 2413
Joined: Thu Jan 28, 2010 1:57 am
Real name: Zayne
Gear: Pro~One, MS20, MPC60, Aalto, Volca Beats, Volca Keys, Beatstep, Casio MT18, BitOne (sorta), Circle, Orbit 3, K5, Stylos, Univox Hi Flier, iPad
Band: Echo & Liora
Location: Paris / Philadelphia
Contact:

Re: OBXA Tandulum caps.

Post by sequentialsoftshock » Fri Jan 13, 2012 2:06 am

I'm surprised he'd suggest you work on it yourself. Especially the transformer / power supply...
bonne chance

User avatar
madtheory
Supporting Member!
Supporting Member!
Posts: 5366
Joined: Mon May 01, 2006 12:45 pm
Real name: Tomas Mulcahy
Gear: Wurlitzer Opus 1536, Model F, Morovdis Arpeggiator, Maplin My First EQ, Jeff Wayne Thunderchild rack, Thermostat, Buck Owens' Moog.
Location: Cork, Ireland
Contact:

Re: OBXA Tandulum caps.

Post by madtheory » Fri Jan 13, 2012 10:04 am

The thing about a power supply is that it's easy to work on by itself, but if you don't triple check everything before you reconnect, you will cause serious damage.

Skiroy, here's a simple way to test your skill for this job- can you operate a 'scope? Do you own a 'scope? Do you solder your own cables? Do you know Ohm's law? Are you able to calculate current having measured voltage and knowing the load? Do you know what a capacitor does? Do you know what a rectifier does?

If you can answer all of those with 100% confidence, then you can work on a power supply.

Skiroy
Newbie
Newbie
Posts: 94
Joined: Thu Jun 09, 2011 3:38 am

Re: OBXA Tandulum caps.

Post by Skiroy » Fri Jan 13, 2012 6:42 pm

madtheory wrote:The thing about a power supply is that it's easy to work on by itself, but if you don't triple check everything before you reconnect, you will cause serious damage.

Skiroy, here's a simple way to test your skill for this job- can you operate a 'scope? Do you own a 'scope? Do you solder your own cables? Do you know Ohm's law? Are you able to calculate current having measured voltage and knowing the load? Do you know what a capacitor does? Do you know what a rectifier does?

If you can answer all of those with 100% confidence, then you can work on a power supply.
I had am electronics class a while back but rarely put it in use.

I dont own a scope but have used one in the past. May be fuzzy on where exactly to put the leads in the circuit.

Capacitors store a charge and or smooth out voltage and are polarity sensitive in most cases but not all. Ohms law is V/R=I or Voltage/Load=current. Yes I can soldier my own cables and I have built a pre amp using old yamaha mixer board channel strips and rack mounted them with a DIY PSU which came in components, I rebuild my rhodes piano preamp and have had soldiering class 4 years ago.I know how to tin a iron,remove and install components. Rather not mess with surface mount

I believe a rectifiers converts A/C to D/C. And I have watch a you tube video of a guy rebuilding his OBXA PSU and voice cards.

So contrary to some peoples opinion on here that I am clueless about electronics I can do some stuff. I just cant yet read a schematic and know what is the proper techniques to test certain components based on weather they need to be on the PCB or off of it to check it. I dont fundamentally know how to look at a circuit and know which component to test based on it function in the circuit. I dont know how to test ICs. I would not know where to test voltages unless it was spelled out, like in the OBXA manual.And NO I dont know s**t about synths when it comes to being a good programmer right now or how to trouble shoot there electronics because I never owned one. But I do understand there signal path as far as the Oscillator section,filter section,and VCA and filter envelope sections.

But I learn fast as long as I have people that are willing to answer questions. Eric is that guy. There are some on the web but I often run into people that just want to shoot me down. I not saying that about anyone here but alot of people rather make there comments instead of be helpful. There has been alot of helpful people here though. Sometimes I wish people would just stay on the topic. I didnt get to know the stuff I have or rebuild my rhodes preamp or rack mount my vintage Yammy pres by listening to people tell me I should just quit and send it to a Tech.

Skiroy
Newbie
Newbie
Posts: 94
Joined: Thu Jun 09, 2011 3:38 am

Re: OBXA Tandulum caps.

Post by Skiroy » Fri Jan 13, 2012 7:00 pm

Still working out the rectifiers needed and I still cant seem to find any Tantalum Caps anywhere. Maybe they are under the voice cards. I only see little brown ones that are flatter which Eric said sounds like ceramic caps.

Yeah, if they are shaped like flat discs, they are almost certainly ceramic. Take a photo and post if you aren't sure. Tantalums are more blob-shaped. Actually, I an not aware that there are any tantalums in the OBXA -- I've never heard that Oberheim used a lot of tantalums.

User avatar
madtheory
Supporting Member!
Supporting Member!
Posts: 5366
Joined: Mon May 01, 2006 12:45 pm
Real name: Tomas Mulcahy
Gear: Wurlitzer Opus 1536, Model F, Morovdis Arpeggiator, Maplin My First EQ, Jeff Wayne Thunderchild rack, Thermostat, Buck Owens' Moog.
Location: Cork, Ireland
Contact:

Re: OBXA Tandulum caps.

Post by madtheory » Fri Jan 13, 2012 9:30 pm

You need to get more practice with electronics- and a valuable synth is not the place to do it.

Look- it doesn't cost much to have this synth serviced and a few caps replaced. Get a price of the guy, get a few other quotes. The good thing is you do know enough to give a tech the right info to give you a fairly accurate estimate, and also to ensure that the guy won't pull the wool over your eyes.

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

Re: OBXA Tandulum caps.

Post by synthparts » Sat Jan 14, 2012 2:43 pm

Oberheims and lots of other analog synth from the late 70s/early 80s has some tantalums.
Vintage Synth Parts - http://www.synthparts.com

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

Re: OBXA Tandulum caps.

Post by Steve Jones » Sun Jan 15, 2012 7:52 am

If yo are going to remove the OBXa power supply board to work on it, replace the bridge rectifier module in the 5V section of the power supply. They are under-specified and fail often.
Synthesizer service tech since 1982.
Synth parts and service, Sydney Australia.

sam
Expert Member
Expert Member
Posts: 1304
Joined: Wed Jun 21, 2006 10:09 pm
Location: Europe

Re: OBXA Tandulum caps.

Post by sam » Sun Jan 15, 2012 2:43 pm

When recapping put a cross (+ve side)on the circuit board first before removing..It's easy to get confused.
Roland Vp330 mk1.SH101.juno 6.OSCar.ARP odyssey..Tonus 2600..omni.
ms20/50. OBX.
Prophet 5
Wasp.EMS AKS.

rjd2
Active Member
Active Member
Posts: 301
Joined: Mon Jul 03, 2006 2:23 am

Re: OBXA Tandulum caps.

Post by rjd2 » Sun Jan 15, 2012 11:04 pm

2 things:

1- just had my OBXA open, and i'm 99% sure the only tants are in the PSU.

2- just being honest here, but if you just want a working synth, you're better off just servicing your OBXA. if you are intent on going down the synth resto rabbit hole, i can guarantee you that about 50-70% of the repairs you attempt for the first 2-3 years will not be done correctly the first time.

3-the OBXA is one of the hardest synths to tune properly. its completely counterintuitive. i think that frankly, trying to fix anything that's not already broken is a complete and utter recipe for disaster. best of luck either way.

Post Reply