Moog Rogue gate issue / loud thump (technical)
Posted: Thu Oct 31, 2013 7:10 am
I have a loud pop noise at gate-on in my Rogue.
I have checked all pins on all 4000 series ic's and they seem to work fine. All transistors are also working to spec. The only thing I have found is a 2N3904 transistor (Q8) which is under spec and goes positive and negative when the gate is cycling in auto trigger. Q8 on my Rogue has a VBE(Sat) of 0.3V while the Motorola spec sheet gives 0.65 as minimum value for this part. Could this be the reason for the loud pop sound ?
For reference here is the Rogue schematic. Q8 is located in front of the 4007 in the ADS section. (This picture may not open in Explorer).
http://www.cykong.com/Synths/Moog%20Rog ... loured.gif
Any thoughts or shared experience would be higly appreciated.
P.S. I have tried adjusting the VCA balance but it doesn't remove the clicks/pops.
EDIT September 2014 (for the benefit of others who search the forum about the same issue):
Fixed. Turned out the U16 IC, which according to the service manual should be a 3080A, was faulty. In my Rogue U16 was a RCA336. I replaced it with a fresh 3080E. Works perfectly again.
I have checked all pins on all 4000 series ic's and they seem to work fine. All transistors are also working to spec. The only thing I have found is a 2N3904 transistor (Q8) which is under spec and goes positive and negative when the gate is cycling in auto trigger. Q8 on my Rogue has a VBE(Sat) of 0.3V while the Motorola spec sheet gives 0.65 as minimum value for this part. Could this be the reason for the loud pop sound ?
For reference here is the Rogue schematic. Q8 is located in front of the 4007 in the ADS section. (This picture may not open in Explorer).
http://www.cykong.com/Synths/Moog%20Rog ... loured.gif
Any thoughts or shared experience would be higly appreciated.
P.S. I have tried adjusting the VCA balance but it doesn't remove the clicks/pops.
EDIT September 2014 (for the benefit of others who search the forum about the same issue):
Fixed. Turned out the U16 IC, which according to the service manual should be a 3080A, was faulty. In my Rogue U16 was a RCA336. I replaced it with a fresh 3080E. Works perfectly again.