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Thread: Roland GR-30 Guitar Synth cap replacement

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    Junior Member Chrisfromiowa's Avatar
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    Roland GR-30 Guitar Synth cap replacement

    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
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    Lifetime Member Enzo's Avatar
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    Have you reinitialized the system since replacing the battery? ("Restore factory settings" if you prefer the term)

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    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.

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    Junior Member Chrisfromiowa's Avatar
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    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.

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    Junior Member Chrisfromiowa's Avatar
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    Quote Originally Posted by Mick Bailey View Post
    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

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    Stray Cap DrGonz78's Avatar
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    Quote Originally Posted by Mick Bailey View Post
    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.

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    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.

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    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.

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    Last edited by Mick Bailey; 10-25-2017 at 12:47 PM.

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    Junior Member Chrisfromiowa's Avatar
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    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?

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    Last edited by Chrisfromiowa; 10-26-2017 at 03:37 PM. Reason: Dick Van Dykes Cockney Accent

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    Lifetime Member Enzo's Avatar
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    "sodder" Like someone who lays sod on lawns.

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    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.

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    Lifetime Member Enzo's Avatar
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    Don't leave us hanging, how do you pronounce solder over there?

    SAW-duh?

    SAHL-der?

    SOUL-der?

    It's fraffly good.

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

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    Old Timer J M Fahey's Avatar
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    Is there any other way to say "solder"?

    ...................
    "sodder"
    ouch!, it makes me shudder!!!!!


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    Juan Manuel Fahey

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    Lifetime Member Enzo's Avatar
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    Some people pronounce the L in salmon.

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

    Justin

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    It's SOUL-der over here.

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    Junior Member Chrisfromiowa's Avatar
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    So this is one case that your damned silent letters aren't silent..... Is there anything we should know about Whip, Lincoln, or the above mentioned Salmon?

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    It's 'sold her' over here 'sod her' over there. When I was in Greece last summer they pronounced the w in swordfish.

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    Juan Manuel Fahey

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    Supporting Member The Dude's Avatar
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    Quote Originally Posted by J M Fahey View Post
    Oh dear. You shouldn't have showed me that feature, Juan. I can have some fun with that!

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    don't forget the joker g1's Avatar
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    Well, in spite of what Mr. Carlson and his videos would have you believe, Canadian's do not pronounce the L in solder. I have no idea where he got that from, perhaps he came up under a Brit instructor.

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    Junior Member Chrisfromiowa's Avatar
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    I kind of feel like I’ve caused an international incident here.... Im just going to imagine Dick Van Dyke as a Cockney chimney sweep and say it like that, guv’nas. Anyhoo got my in-circuit tester opened it back up and realized i was thinking of this other thing ive been working on with the surface mounted caps, this has all normal caps. None of them look bad, so I compare the values listed on the service manual,there are only 4 varieties, and check them all using say 1000u/6.3v etc., right.Click image for larger version. 

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    I don't know what you mean by " ....and check them all using say 1000u/6.3v". Can you clarify?

    A faulty component can look just the same as a good one, though if you did have an oozing or encrusted cap that wouldn't be good. Did you first check the battery voltage to see if something is running it down? If the battery is getting discharged I'd be looking for a low resistance effectively appearing across the terminals. If the battery voltage is good than you could have a high resistance in series with the battery.

    A problem you may encounter though is that the battery circuit is fine, but the battery could be mistakenly being reported as faulty.

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    Junior Member Chrisfromiowa's Avatar
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    I don't know what you mean by " ....and check them all using say 1000u/6.3v". Can you clarify?
    that in this device there are only 4 different caps, so a good reading is going to be one of four values, like the 1000u(F) 6.3v. Im coming to the realization that I should have spent more on my esr meter, and that one of the ones that list good/bad are probably better suited to my ability. The battery does not actually drain, the system just alerts me to a bad battery at startup. The battery is used to hold user patches and preferences, so I guess that there could be a couple different components that have gone bad. Or it might just be an alert that means nothing. Someone told me it was a bad cap, but none of them are obviously damaged, although two of them apparently have a small red line at the top right next to the cap, im not sure if it’s electrolytes or just the way they are designed. Roland cant help me due to a new company policy, and I totally understand that, theres no money in helping a cheapskate like myself avoiding buying something new. Thanks again, regards Chris

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    Can you post a schematic?

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    Junior Member Chrisfromiowa's Avatar
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    Quote Originally Posted by Mick Bailey View Post
    Can you post a schematic?
    Heres a link to the service manual with the schematic, http://www.synfo.nl/servicemanuals/R...VICE_NOTES.pdf
    I’m repairing my computer right now and only have an iPad so the best I can do is screenshots. I hope they’re detailed enough for you. Thanks again, regards ChrisClick image for larger version. 

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    Did you go through the internal battery test routine (section 4 page 7). It also gives the place to check if it fails - R86 in series with the battery, and IC20.

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    Junior Member Chrisfromiowa's Avatar
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    Quote Originally Posted by Mick Bailey View Post
    Did you go through the internal battery test routine (section 4 page 7). It also gives the place to check if it fails - R86 in series with the battery, and IC20.
    Hello Mr Bailey,
    No and yes, and no. I didn’t do the test, i did replace the battery and checked the resistor, and Im sure about the ic chip. I’d started down that path when I was told it was a cap, is “its a bad cap” the electronics version of “I think it’s the carburetor “?. In testing the chip I would use my regular multumeter with the battery in place and compare the values listed on the schematic, right? And if it is bad, I’m probably up the creek unless I can find a kindly Roland service provider... Well, here’s to hoping that I can figure that the chip is good. Thanks for subtlely reminding me something I should have never forgotten, RTFM!!!

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    With the synth unpowered (but with the battery in place) make sure you have a voltage greater than 2v on the VCC pin of IC25. This is the memory retention voltage.

    IC20B is configured as a buffer, so you should see the same voltage on pin 7 as pin 5 if the synth is powered. Trace this through to make sure you get a voltage on the processor side of R87. This is what the processor uses to report low battery voltage. Actually, it's safer to initially check the voltage on either side of R87 rather than risking a probe slip on the IC pins.

    Does the unit retain its memory after being powered off?

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    Junior Member Chrisfromiowa's Avatar
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    Quote Originally Posted by Mick Bailey View Post
    With the synth unpowered (but with the battery in place) make sure you have a voltage greater than 2v on the VCC pin of IC25. This is the memory retention voltage.

    IC20B is configured as a buffer, so you should see the same voltage on pin 7 as pin 5 if the synth is powered. Trace this through to make sure you get a voltage on the processor side of R87. This is what the processor uses to report low battery voltage. Actually, it's safer to initially check the voltage on either side of R87 rather than risking a probe slip on the IC pins.

    Does the unit retain its memory after being powered off?
    greater than 2v on the VCC pin of IC25
    Do you mean the ic20? I'm having a hard time seeing any voltages on the pins of the ic20.

    Does the unit retain its memory after being powered off?
    A resounding yes. I mean, that's a good thing, right? If it says that there is a battery problem, but the function that the battery maintains is still working, might this be one of those If it aint broke, don't fix it realities....

    Also I guess you can't see it here but there is a small amount of red residue on the silver of this cap. I can't see that its part of the backup, but I'm not that good at reading schematics either. Thanks again, regards ChrisClick image for larger version. 

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    IC25 is correct - this is the memory chip that needs the battery voltage to retain the contents. Given that the memory is retained then we can rule out that part of the circuit as the chip has to have more than 2v otherwise it will lose the settings when power cycled.

    Again, there are two parts to this circuit - the battery voltage to the memory (established as being OK by inference) and the voltage being provided to the CPU for it to report on the battery condition when the unit is powered. I think you have either a missing voltage on pin 7 of IC20, or R87 is maybe open. Check the voltage at both sides of R87. If you get no voltage either side then IC20 isn't working correctly for some reason, (or D27 is shorted on pins 2 & 3). If you get voltage one side and not the other then R87 is open.

    The cap is unrelated and there's no cap fault with the battery circuit.

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