GFA-535 Brown gunk on output board

btom · 16th December 2011, 02:05 AM

Ugh! Opened the case of my GFA-535 (bought back in 88 or 89) and the PSU board has a lot of brown gunk around the big 6800 um capacitors. Last time I opened it to clean and replace fuses, probably 5 years ago, I don't recall seeing that. I suppose this is the leaking capacitor issue? One reason I opened the case is that the woofer on my left channel speaker blew but I don't recall any bad behavior (well maybe from one of my kids). Anyway, I figured I'd look inside to check fuses and to see if anything looked odd. I obviously need to change the capacitors but how should I (or should I at all) clean the board? Any help appreciated.

Ian Finch · 16th December 2011, 10:09 AM

Electrolye is somewhat water soluble, so alcohol and cloth should remove it safely if you repeat the process until all remnants are removed - both sides and lurking in through-holes too. Use a brush to remove difficult stuff and try to avoid spills on unaffected areas and the case etc.

Test that solvents don't remove any printing on the PCB, as this will make troubleshooting very difficult. If this is the case, adding a little water to the alcohol will reduce this attack. Many other solvents like acetone will remove printing pronto - take care.
Dry it out thoroughly in a warm area before fitting replacement caps and powering up again.

btom · 16th December 2011, 02:24 PM

Thank you Mr. Finch!

embrown057 · 17th December 2011, 06:19 PM

That "Brown Goo" in not Lytic fluid. It's the glue that was used to help hold the device and shoud not be a problem. If you repalce the caps it would be from age but I would guess the caps are in good shape. Change them if you want, it may just be a waist of time unless you mesure them and find out there high in ESR and low in value.

16th December 2011, 02:05 AM	#1
btom diyAudio Member Join Date: Jun 2004 Location: Virginia	GFA-535 Brown gunk on output board Ugh! Opened the case of my GFA-535 (bought back in 88 or 89) and the PSU board has a lot of brown gunk around the big 6800 um capacitors. Last time I opened it to clean and replace fuses, probably 5 years ago, I don't recall seeing that. I suppose this is the leaking capacitor issue? One reason I opened the case is that the woofer on my left channel speaker blew but I don't recall any bad behavior (well maybe from one of my kids). Anyway, I figured I'd look inside to check fuses and to see if anything looked odd. I obviously need to change the capacitors but how should I (or should I at all) clean the board? Any help appreciated.

16th December 2011, 10:09 AM	#2
Ian Finch diyAudio Member Join Date: Apr 2010 Location: Coffs Harbour, on the east coast	Electrolye is somewhat water soluble, so alcohol and cloth should remove it safely if you repeat the process until all remnants are removed - both sides and lurking in through-holes too. Use a brush to remove difficult stuff and try to avoid spills on unaffected areas and the case etc. Test that solvents don't remove any printing on the PCB, as this will make troubleshooting very difficult. If this is the case, adding a little water to the alcohol will reduce this attack. Many other solvents like acetone will remove printing pronto - take care. Dry it out thoroughly in a warm area before fitting replacement caps and powering up again. __________________ regards

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16th December 2011, 02:24 PM	#3
btom diyAudio Member Join Date: Jun 2004 Location: Virginia	Thank you Mr. Finch!

17th December 2011, 06:19 PM	#4
embrown057 diyAudio Member Join Date: May 2010 Location: Florida	That "Brown Goo" in not Lytic fluid. It's the glue that was used to help hold the device and shoud not be a problem. If you repalce the caps it would be from age but I would guess the caps are in good shape. Change them if you want, it may just be a waist of time unless you mesure them and find out there high in ESR and low in value.