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roland gr20 guitar synth static hiss noise!

Started by EDWARDEFFECT1, July 21, 2010, 06:15:51 PM

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EDWARDEFFECT1

here is a tough one . i know this is an amp forum,but i am having a problem with static crackling noise in a gr20 roland guitar synth.you can't get a shematic from roland for it.i'm not sure where to send a signal into the midi connnection so i can signal trace with an oscilloscope.anybody had a simular problem or have any ideas.the unit works great in all other areas. it just has alot of noise.the guitar and pickup works perfectly with another unit.the midi chord is good and there is a new input board in it and it didn't make any difference. don't see any cold solder joints.....any help appreciated.i thought this would be my best place to get a fix for this unit.as i have delt with this site in the past and rate this site as the #1 elcectronics knowledge base on the net!!!....keep rocking....thanks...ed!!

J M Fahey

Tough one indeed.
The reason for Roland not providing a schematic for it makes me think that this thing must house a monster 144 pin square blob of plastic which "does it all" and not much else.
Definitely you will *not* inject any (audio) signal at all into the Midi connector, it carries only a stream of Midi coding.
That said, as digital as it may be, audio must surely pass across *some* capacitors, resistors (which imply soldering), connectors, PCB tracks , jacks, etc. , which might through various imperfections (cracks, bad contact, etc.) make noise.
I'd send a clean sinewave into it, scope a naked plug sitting in the output jack (where I should *clearly* see the crackling noise disturbing the sinewave) and move backwards from there.
You *may* find some spot where before it the signal is clean. Look carefully around it.
If in your backward journey you get into some digital monstrosity where the signal still emerges dirty, forget about it.
Drop it into the trash bin where it was genetically engineered to end.
Build an AX84, plug your favorite guitar into it and enjoy the life.  :tu:

bry melvin

is the static present in the "regular" guitar through signal ? or just the midi pickup portion.?

If only using the midi synth sound...it could be some shielding missing between audio portion and computer...or just simply something like a level pot...a wire too close to the computer portion,,,, did they leave something (sheilding) out putting the new input board in?

The midi portion is likely to not be causing the static unless there's some REALLY noisy memory.

Sorry I can't help more...but my synth access guitars go into a 4 computer studio rig not a stand alone processor.

FWIW JM synth access is REALLY good if you need a track for a sax etc and don;t have or can't afford one...(or don't  know how to play one) .It also takes a lot of drudgery out of scoring what you're writing. Very handy paper trail for copyright suits too. You can print out all the scores of the piece as it evolved




J M Fahey


AutoDoc

Hi fellas, I'm new on the board and found this thread while hunting up noisy GR-20 problems and I see that it ain't just me.  In my setup, (telecaster, GR-20, several stomp boxes, back to GR-20, out to Marshall half stack) I am hearing white noise as mentioned here, and also 60Hz hum.  The problem is definitely NOT a ground loop, and it is NOT the 13 pin cable.  The problem is for sure in the GR-20 effects loop circuitry, and in my (old, experienced, guy) opinion is a shielding problem within the bowels of the GR-20.  The biggest problem I think is that the GR-20 takes an AC input from its transformer so that gets that 60Hz signal all the way into the GR-20's housing.  I tried grounding the bottom metal plate of the GR-20 and that had no effect.  Most of my other stuff takes various DC voltages in, and as long as I keep the wall-warts shielded from the audio, all is well.  The white noise is coming from somewhere else, but I'll bet that it's also caused by poor shielding in the analog audio section of the GR-20.  I'm still trying to quiet this thing down, and if I make any progress, I'll post up here.  Since I've seen this complaint elsewhere, I'd say that the OP does not have a broken GR-20, but a poorly designed one.  I'm gonna poke at Roland a little to see if I can get a response, but I'm not expecting much more than the "check for ground loops" boilerplate fix that everyone gets.  If I come up with an answer, I'll post back here.

EDWARDEFFECT1

Quote from: EDWARDEFFECT1 on July 21, 2010, 06:15:51 PM
here is a tough one . i know this is an amp forum,but i am having a problem with static crackling noise in a gr20 roland guitar synth.you can't get a shematic from roland for it.i'm not sure where to send a signal into the midi connnection so i can signal trace with an oscilloscope.anybody had a simular problem or have any ideas.the unit works great in all other areas. it just has alot of noise.the guitar and pickup works perfectly with another unit.the midi chord is good and there is a new input board in it and it didn't make any difference. don't see any cold solder joints.....any help appreciated.i thought this would be my best place to get a fix for this unit.as i have delt with this site in the past and rate this site as the #1 elcectronics knowledge base on the net!!!....keep rocking....thanks...ed!!

EDWARDEFFECT1

thanks everyone for the help. i followed jm fahey's advice and signal traced the circuit with my oscilloscope and got the static fixed. it had a bad 10uf capacitor. nasty little bugger.alot ceaper than a $300.00 plus board.the unit works like new now.i new i had it fixed when i got a square wave pattern out the output that was uniform....thanks again!!!...ed!!

hartattack72

I am having the same problem.  Would it be possible for you to post a pic of where the location of the 10uf capacitor is in the unit?

quazcha

Hello all,
Greetings from the Peoples Democratic Republic of New Jersey.

  I too have the HISS GR-20 problem, EDWARDEFFECT1 could you list the capacitor's number ex: C7 or the location of the cap? I see (14) 10uf 16v electrolytics and (6) 10uf 16v non-polorized?
I may just "shotgun" and replace them all as I am SALIVATING at the possibility of having this fixed- I bought it new on ebay and had a problem out of the box-vendor sent me to Roland- they said vendor is not an authorized seller so NO WARRANTY REPAIR ON A BRAND NEW ITEM- of course I could send it to them for an $75 estimate charge...WTF?

quazcha

Hartattack72 - I ordered the caps from digi-key under ($15 with shipping) 14 -10uf/16v, and 6 - 10uf/16v non polorized, If Edwardeffect1 gets back to me I'll have 19 parts  in stock-lol. If not, I'll decide on shotgunning and replace ALL 10uf caps on the jack board- parts are low cost & labor is free.... I will let you know how I make out with it!

EDWARDEFFECT1

#10
sorry i didn't see your posting.if you send a picture of the board it might jog my memory of what i replaced.hopefully it is the same capacitor that is bad.i injected a  sine wave signal into a cap at the top right hand side of the board and then i checked the wave forms from the output  back up towards the origin of the injected signal till i got a good signal. then i replaced 3 caps on the right side of the board that were grouped together.after i replaced the caps . i got a perfect square wave out the ouput while injecting a sine wave.hope this helps.i have a good preamp board for a roland here at the house,the problem with the hiss was not on the preamp input board..hope this helps a little. like i say if i see a picture of the board i might better be able to dial you in on the caps i replaced.....ed

p.s the capacitors i replaced were  all electrolytics.non polarized capacitors seldom go bad!.....
also look at the tops of the capacitors for bulged tops or leakage.

quazcha

EDWARDEFFECT1 here are the pics sorry for the poor paint job. I assume the 3 caps are the ones with the red arrow on my close up photo?

quazcha

I just re-read your reply It was on the main board? I have marked all of the 10uf caps in yellow the rest are 0.47uf

EDWARDEFFECT1

#13
the 3 caps i replaced on mine were on the right hand side of your board.there is a group of 5 near the bottom right side of the board. i replaced the 3 in the middle of the group of 5.another words all of them except the top and bottom cap.hope yours is the same...hope it works for you.i know it could be another cap somewhere,but thats what fixed the one i repaired.luckily it was a cheap fix. they wanted $300.00 at a roland service center they were going to replace the whole board ouch!!.i got it after they looked at it from a friend. i made his day as i was alot cheaper for me to fix it.saved him alot of bucks.....!!!....ed

ps: don't forget to look for bulged tops on all your caps if you find any replace them.the ones i replaced looked good but at least one of the 3 was bad...

quazcha

all caps look good I'll try by first replacing the 3 you suggested, Thanks! I will keep you posted on how I make out. You said you had an input/output jack board, would I be able to borrow your board to check if my problem is on that board. I get a hiss in the left channel after a while