SGH

[On The Rocks]

Does anyone know anything about SGH amps? I have an SGH VSH100 head and cab that I can not find anything other than one youtube video about. Anytime you lightly tap the head it chimes out the speakers like clinking glasses. I narrowed it down to what I believe is the phase invertor tube 12AT7. replaced the tube with a new groove tubes tube and still does it. replaced it with a 12AX7 and went away. Only thing is I understand that the 12AT7 handles more power and cant have the amp go down during a show. Also it only makes the sound if guitar cord is plugged in. I have searched for days for any info/schematics on this amp with no luck. I can live with the slight chime sound but with vibration from kick drum and bass the chime will build to a feedback. Any info is greatly appreciated. This amp sounds to good to not be able to use

[jjasilli]

Always suspect tubes first.  Sounds like a microphonic tube.  When the amp is on tap each tube lightly with a chopstick.  Then try lightly tapping: the transformers; then the chassis.


If that doesn't work, open the chassis and try probing leads & components

[On The Rocks]

I figured on tube issue. I did figure it out last night. Took 3 AT27 tubes before found one that worked. All the Groove Tubes that I used chimed out. finally got a JJ tube and all fixed. Imagine that! I still would like to find some info on this unit if anyone could point me to where I can find manual or schematics for it.

[jjasilli]

Besides replacement, 2 possible fixes for a microphone tube:  spring loaded tube shield; Special heat resistant "rubber bands" for tubes that damp vibration.