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Post by telejas on Dec 16, 2017 14:39:40 GMT -7
UPDATE... Fixed!! See my reply below.
I just picked up an AC30H2 and while playing through it, I noticed the cut control does virtually nothing at all on the amp. I've had many AC30 and similar amps with cut controls, and know how it *should* work, it doesn't.
I can tell a very slight difference in the hisssss the amp makes when I turn it, but it doesn't seem to affect my tone at all.... If it does, it's not noticeable.
I pulled the chassis and followed the 2 leads from the cut, through the chassis, to the power tube terminals, and didn't find any broken solder points.
Any thoughts on what this might be?? Luckily, it seem set in the middle (or at least at a place I seem to like).
I've changed all the preamp tubes and rectifier......But, could this be power tube related in any way?
Any advice would be appreciated.
**I've read that some amps require higher volumes for a cut or presence control to work..... Is this the case with the AC30H2? I haven't had much of a chance to really turn it up. If it is, this is different from any other Vox I've ever owned.
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Post by purpletele on Dec 16, 2017 20:15:19 GMT -7
I just picked up an AC30H2 and while playing through it, I noticed the cut control does virtually nothing at all on the amp. I've had many AC30 and similar amps with cut controls, and know how it *should* work, it doesn't. I can tell a very slight difference in the hisssss the amp makes when I turn it, but it doesn't seem to affect my tone at all.... If it does, it's not noticeable. I pulled the chassis and followed the 2 leads from the cut, through the chassis, to the power tube terminals, and didn't find any broken solder points. Any thoughts on what this might be?? Luckily, it seem set in the middle (or at least at a place I seem to like). I've changed all the preamp tubes and rectifier......But, could this be power tube related in any way? Any advice would be appreciated. **I've read that some amps require higher volumes for a cut or presence control to work..... Is this the case with the AC30H2? I haven't had much of a chance to really turn it up. If it is, this is different from any other Vox I've ever owned. Telejas, i would consider the Pot as most likely to fail, the only thing to fail really. i would start there.
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Post by zpilot on Dec 16, 2017 20:33:01 GMT -7
I don't have a schematic in front of me but there should be a cap in that circuit connected to one of the terminals of that pot. Somewhere around .0022 to .0047 if I recall. You might check to see if that is good or even change the value if you want more effect. The higher the value, the more highs it will roll off.
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Post by premiumplus (Dave) on Dec 18, 2017 4:21:33 GMT -7
Agree 100% with the above posts. Either the pot failed or the capacitor did, or there is an open circuit in the wiring between components, possibly a short to ground somewhere. It's as simple as circuits get. Did you find the problem yet?
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Post by telejas on Dec 18, 2017 21:14:21 GMT -7
Agree 100% with the above posts. Either the pot failed or the capacitor did, or there is an open circuit in the wiring between components, possibly a short to ground somewhere. It's as simple as circuits get. Did you find the problem yet? No, been under the weather..... I did trace the wires, but found no bad solder joints. It's doing something, very slightly, when I move the cut knob (I can hear the hiss change).....Which leads me to believe the pot or capacitor is dying, or possibly been modded in the past? Some of the post on the pot don't look "factory", like it's had something done before? I also don't really have a way to test capacitors, so I may just replace it. Gonna tackle this later this week, if I feel better... Or after Christmas? Where's a good place to get replacement parts? I searched Google and am having a hard time finding the right pots?
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Post by zpilot on Dec 19, 2017 5:04:45 GMT -7
I used to be a Korg authorized repair tech (among others) and I got a lot of parts from "Parts Is Parts". That would be a good place to start.
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Post by telejas on Jan 27, 2018 20:15:39 GMT -7
FIXED!! Finally got a night off, and weekend off, to take a loot at it! Looks like someone replaced the capacitor a few years back and put it in the wrong spot.... Plus, it was dead. I replaced it and moved it over to the correct spot, and it works perfect now! Wrong: Correct:
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