Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: mresistor on December 03, 2015, 11:25:42 am
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As the title says during setting up bias on my new SC DR build I was measuring HV which was 456v and as I pulled off the probe I guess I caused a path for the 456v to travel across to pin 2. Not good! and first time I have ever had this happen in my guitar amp experiences. It arced and as is always the case it seemed like it took forever to get to the off switch, which I did immediately turn off. I don't think I did any permanent damage to the PT filament winding, as it is still putting out 6.45VAC. And I don't have any DC on the heaters. These are brand new Belton sockets. Doesn't look like any damage to the socket. I did figure out that I had my 16 ohm cab hooked up to the 8 ohm jack and I have since plugged it into the 16 ohm jack. I also dropped the HV down to 432 with a 5R4 . I did get bias adjust done and have played through the amp and it sounds pretty good. The tremolo works really well and the reverb works too well. I'm going to have to tame it down some. However, there is alot of noise on the reverb. There is some static type noise with no input and volume turned way up, but there is a ton more noise, static and hum, when I turn up the reverb. The reverb tank is sitting out at the present time next to the chassis and I am using hifi rca cables because I haven't made the permanent cables yet as the cabinet isn't ready.
What would cause there to be a large amount of noise and hissing/humming on the reverb? I've built two DRs from scratch and they had no problems. This is a Hoffman turret board amp.
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Well I found the problem. Not my day. The reverb send wire was running very near one of the 12AX7s and I don't have any shields installed on it. Positioned wire away and all the noise went away.
Thanks to all those that read this. Back to working on the cab now
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Good catch. :icon_biggrin: