Other ADA Gear > Combo Amps
Viper combo amp
MarshallJMP:
Hey KG, first welcome the the ADAdepot :thumb-up:
As for the varicab, I looked at the schematic and it could be a couple of things, thee bypass switch, the high cut pot or an opamp (U8)
K_G_1:
Thanks for all the replies so far and sorry I disappeared for awhile. I've played around with it some more and discovered that I was lying about there only be a hum. If I crank the amp with the gain and volume to 10 there is sound with the varicab turned on, it is just very quiet. The signal is the same through both the record out and effects send - weak, but there. Should I just start replacing the parts you mentioned, or does this development help diagnose the problem? Thanks again!!
Dante:
Welcome to the Depot K_G_I!!
Have no fear, you have stumbled across the best place on the web to get your ol' amp back to new (well, old new).
Dante
MarshallJMP:
Well it should be one of those 3 things I mentioned, maybe start with the opamp.
K_G_1:
I found the schematics posted elsewhere on the site, and see two op amps labeled U8. Are you suggesting the replacement of both, or is there one that is more likely the problem than the other? (I've attached a screen shot of the two U8 op amps in the schematics). Also, there seems to be a huge variety of NE5532 op amps available. Is there a specific one that would be best for this application? Are they standardized in terms of pin positioning, size, ect? Are the op amps available from mouser (http://www.mouser.com/Search/Refine.aspx?Keyword=ne5532) what I want?
Sorry if these are silly questions, but while I have done some circuit board soldering and repair, I am totally inexperienced in terms of amp repair. Finally, given my inexperience in this area, am I risking the correct operation of the rest of the amp if I screw something up, or is the varicab circuitry totally separate/bypassed until the switch is engaged? Looking at the schematics, I think its the latter, but I'd like to confirm before I start this project just so I know the stakes involved :-\.
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