Roland GR-30 Guitar Synth cap replacement

[Chrisfromiowa]

Does anyone have any experience with Roland guitar synths? I have a GR-30 that has a battery error even though I've changed the battery. I've been told its a capacitor problem there are only four different cap values used according to the service manual. I'm guessing I'll have to go through and check each one, but I'm not that fond of surface mounted components. Any help would be appreciated. Thanks all, regards Chris

[Enzo]

Have you reinitialized the system since replacing the battery? ("Restore factory settings" if you prefer the term)

[Mick Bailey]

This is where an ESR meter really comes in handy. Usually the capacitance value reads fine, but the ESR climbs until the cap is open-circuit. With my meter I can quickly test every cap on a board and determine which (if any) are faulty. SMD cap failures are pretty common on older equipment such as this, but don't assume that this is the problem without actually checking. It's easy to damage the tracks and you'd feel pretty stupid if a pad lifted on a cap that didn't need replacing.

The first thing I would check is that your battery voltage is present on the board and you'll probably need the schematic or service manual to locate appropriate test points.

I've removed hundreds (actually hundreds) of SMD electrolytic caps and I use this technique;

You need a really sharp, fairly hefty but slim side cutters. I line the cutters up with the cap terminals in line with the jaw opening and snip through the cap just where the body meets the plastic end plate. I then lift off the plate and now I have to terminal stubs sticking up. A little SMD rework flux and they clean right off with some fine solder braid. Then clean up with a Q-tip and some alcohol, then the replacement cap can be fitted. I can do this easily in the time it takes to write this.

[Chrisfromiowa]

Yes, several times, but I really wished that was the problem. I've actually replaced the battery twice, the second time I installed a coin battery clip because, well I don't know, I just thought maybe I'd bought a few bad batteries or something even though the multimeter said they were OK. Thanks though.

[Chrisfromiowa]

This is where an ESR meter really comes in handy. Usually the capacitance value reads fine, but the ESR climbs until the cap is open-circuit. With my meter I can quickly test every cap on a board and determine which (if any) are faulty. SMD cap failures are pretty common on older equipment such as this, but don't assume that this is the problem without actually checking. It's easy to damage the tracks and you'd feel pretty stupid if a pad lifted on a cap that didn't need replacing.

The first thing I would check is that your battery voltage is present on the board and you'll probably need the schematic or service manual to locate appropriate test points.

I've removed hundreds (actually hundreds) of SMD electrolytic caps and I use this technique;

You need a really sharp, fairly hefty but slim side cutters. I line the cutters up with the cap terminals in line with the jaw opening and snip through the cap just where the body meets the plastic end plate. I then lift off the plate and now I have to terminal stubs sticking up. A little SMD rework flux and they clean right off with some fine solder braid. Then clean up with a Q-tip and some alcohol, then the replacement cap can be fitted. I can do this easily in the time it takes to write this.

I'd just ordered a cheap in-circuit ESR meter, and I've got the service manual, does it name the test points or do people who know what they're doing know what they're looking for? I really am not looking forward to this surgery as my through hole soldering skills are weak at best. Well, I can always frame the PCB if I brick it and call it art. Thanks

[DrGonz78]

This is where an ESR meter really comes in handy. Usually the capacitance value reads fine, but the ESR climbs until the cap is open-circuit. With my meter I can quickly test every cap on a board and determine which (if any) are faulty. SMD cap failures are pretty common on older equipment such as this, but don't assume that this is the problem without actually checking. It's easy to damage the tracks and you'd feel pretty stupid if a pad lifted on a cap that didn't need replacing.

Very great point about the ESR checking. I was working on a Casio PG380 guitar and the owner wanted me to recap the entire thing. My first thought was to troubleshoot which caps were to blame for the lower strings cutting out. Good ole ESR meter testing and I removed two suspect caps to find that the thing worked great after replacements. There is a website that says just start replacing all the caps with disregard to actually troubleshooting. I agree in some sense that if some of the caps are going bad then it is only a matter of time, but still fix what is broken then think about further work. I did recap that entire guitar and now it is good for years to come. In fact, the owner kept telling me this was the same synth guitar used making the music for the Princess Bride movie. I thought at first he meant it was the same model synth used but really it was the exact guitar played in the movie. Now we can sell it for a million dollar$ on fleaBay!!

I have this really old 10 watt soldering pencil that I used on that repair and with some quick chip removal of the caps was a breeze. I tried this with a brand new 12 watt pencil on another PG380 and did not have as smooth of an experience at all. So back to the 10 watt relic for all future endeavours or until it final breaks.

Also, Mick?? I like what you are saying about slim side cutters to remove cap part. There is a video where the guy simply twists them off. Your approach seems way safer than his and I would be worried that simply twisting the can to break the legs might still damage the pads.

[Mick Bailey]

I consider twisting them off to be really bad advice. The cutters I use are the ones pictured. I usually go for the crimp line around the base of the can, sometimes lower depending on the cap, but always with the cutters in line with the connections so the legs aren't squeezed together. I have 100% success rate with this method, even if the pads are weakened through leaking electrolyte.



Regarding the battery replacement - you may have a shorted cap or on that's leaked and caused low-resistance across the pads. Trace back where the battery connects and measure the voltage. You may find the new battery is getting discharged. Diagnose the problem first though before attempting to replace anything. Take a close look at the board to see if any caps are raised off the board through bulging seals, or whether there's crystallized crud around any.

Edit: just remove the battery and check the voltage first to see if it's getting discharged.

[Chrisfromiowa]

DrG, Mick, Enzo, thanks. OK, I have one other question that will show how little I really know about surface mounted components. The listing on the Roland service manual gives what looks like part numbers, codes, and values. Since these are Roland internal documents meant for Roland authorized service workers most of what I need just the value, right? like of 00674423 ecaojm102 1000u/6.3v. The part of this string that is important is the 1000u/6.3v, that being some kind of 1000uF 6.3volt cap, I've found some results for the last two parts of the string, ecaojm102 1000u/6.3v, but I'm thinking that once I figure out the problem I'll be able to look at the components and hopefully get a better idea. I know that not every 1000uF 6.3V cap will work, but what else should I look for? Thanks
00674423 ecaojm102 1000u/6.3v
13639134jo sme10vb1000 1000u/10v
00346378 25mv3300hc 3300u/25v
00127301 lla50vb1 1u/50v low leakage

PS have I been saying solder wrong all these years?

[Enzo]

"sodder" Like someone who lays sod on lawns.

[Mick Bailey]

Not over here. People would look at you all funny gov'nor if you pronounced it like that. Try it like this; hook your thumbs behind your lapels and kick your heels in the air whilst saying it. Now which do you prefer?

Caps have lots of variables, but the main one after capacitance/voltage rating is physical size - make sure replacements are the same size. Also, if you have a choice, go for the higher temperature rating of 105C rather than 85C and lowest ESR. I wouldn't get too hung up on specs. Think of it this way - caps deteriorate over time and the synth kept working fine with degraded components until one day it went faulty. Any replacement component is likely to be much better than a failing one and will probably last as long as the originals.

But again, don't assume the caps are the problem. It's possible that one or more have failed, but not a certainty. Be sure to diagnose the problem first. There's a poetry, beauty and sense of achievement when you diagnose a problem (sometimes quite complex) and get it in one.

[Enzo]

Don't leave us hanging, how do you pronounce solder over there?

SAW-duh?

SAHL-der?

SOUL-der?

It's fraffly good.

[The Dude]

I believe the English blokes say "soul-der". Mick can confirm (or deny), but I recall watching a UK video and noticing the difference.

[J M Fahey]

Is there any other way to say "solder"?

...................

"sodder"

ouch!, it makes me shudder!!!!!

[Enzo]

Some people pronounce the L in salmon.

[Justin Thomas]

Yeah, well, I didn't get my stomach cringed from Sam&Ella, either...

Justin