5E3 Clark Beaufort [Archive]

1stormcat

01-06-2009, 06:48 AM

I have had this amp for several years now and think it is great. A couple of problems have come up that are keeping me from enjoying this wonderful amp.

Maybe those of you that have technical background can help me out.

When I switch the standby switch to ON the amp starts a steady hum. It hums when plugged in or not and it hums even after being on for quite a while. It is a steady background hum.

Also at times the signal breaks up creating a lot of static especially when first turned on. As the amp warms up the static tends to go away. Then the static will tend to return if I play D on the high E string.

I have changed the 12AX7 as well as the 12AT67. I also changed the 6v6's as well as the rectifier tube to no avail.

Could these two problems be related. And what do you think could be the problem?

Thanks

Trout

01-06-2009, 08:14 AM

It could be as simple as the input jacks needing cleaned, it could be several other things as well. Given the age of the amp, I would start by first confirming the type of hum you are getting.

Before you go to far, Check in with Mr Clark on warranty status. If you are still under warranty, you do not want to void it by tinkering inside.

http://www.clarkamplification.com/warranty.htm

Blue Strat

01-06-2009, 08:27 AM

What Trout said.

Also, try pulling the PI (phase inverter) tube, the preamp tube closest to the power tubes. If the hum stops, the problem is in the preamp of the amp, if not, it's in the power supply or power amp section.

RC2

01-06-2009, 10:59 AM

Make sure you've turned the volume all the way off on the channel you're not plugged in to. Mine does the same thing if I forget and leave both turned up.

donnyjaguar

01-06-2009, 11:32 AM

Wild guess. You have two problems:

- Power supply filter capacitors could do with replacement.
- You have a whipped plate resistor in your preamp chain or more likely a cold solder joint on same.

1stormcat

01-06-2009, 03:57 PM

I've turned down the other volume knob but the hum persists.

Trout

01-06-2009, 05:40 PM

I've turned down the other volume knob but the hum persists.

Start one at a time,

No Guitar plugged in,
both volumes down, Noise?? Yes/No
" " Raise Volume 1 Noise?? Yes/No
" " Raise Volume 2 Noise?? Yes/No

Pull V1 Any noise? Yes/No
Pull V2 any noise? Yes/No

Since the amp is only a couple years old, I doubt the PS caps are shot, possible? yes, Likely? no.