Diagnose this...

[JDJ]

My amp has a ticking noise on the bright channel only. The ticking varies in speed and in pitch. It does not matter whether the guitar and cable is plugged in. I have switched out every tube one at a time, and the noise is still there. It is a 5F6-A circuit. Turn the bright channel volume pot up, and the noise gets louder. Turn it all the way down, and it goes away. Turn up the normal channel, and there is no noise.

What is it? What needs to be checked first? Thanks.

[JDJ]

Also, the buzz or tick sometimes degenerates into popping and static. It does not appear to be the tubes.

Anyone?

[Pearly Gator]

Per the schematic, the amp came stock with a two prong power cord. If you convert it to a 3 prong (grounded) cord it should help with noise. Are there any appliances nearby? Things like a microwave or TV? Has the amp had a recap job? As capacitors in the power supply age, their filtering ability deteriorates.

Best of luck,

PG

[donnyjaguar]

Well, given there are only two components to check it should be pretty easy. Check the 100k resistor from the plate of the 12AY7 to the supply. Hint, if there isn't 150Volts on the plate then that's the culprit. There's also a 20n capacitor that may be leaking DC to the volume potentiometer. If you measure ANY dc voltage on the input to this pot' that's your problem.

Of course, I could be wrong. :)

[ScottWolfe]

Could be an input jack, if the shorting tab isn't making good contact. Try a little DeOxit and give it the old in-and-out. If the clicking stops with a cable in one of the inputs, that's a clue that that jack is the ticking source. Good luck.

[Swarty]

It sure sounds like a cap issue to me. Either the bright cap on the Vol control or the coupling cap.

[donnyjaguar]

I'm with you Swarty. (What exactly is a swarty??)
I don't think its the bright cap on the volume because there shouldn't be any DC across it during normal operation.

Scottwolfe, I don't think its the jack 'cuz JDJ says it does it with instrument in or out. Usually cycling is caused by a charge-discharge mechanism and you need a capacitor (either physical or virtual) for that.

[Old Tele man]

...with NO vibrato circuit, it sounds more like a decoupling "capacitor" problem...ie: "breaking" down (pops) and "failing intermittantly" (noise).

...check the preamp cathode decoupling capacitors and the main high-voltage filter cap(s) supplying voltage to the preamp tube(s).

[Swarty]

...with NO vibrato circuit, it sounds more like a decoupling "capacitor" problem...ie: "breaking" down (pops) and "failing intermittantly" (noise).

...check the preamp cathode decoupling capacitors and the main high-voltage filter cap(s) supplying voltage to the preamp tube(s).

It would seem either of these components would affect both channels?

[Old Tele man]

It would seem either of these components would affect both channels?

...normally, I'd agree, but -- and I'm "going out on a limb" here -- one side (triode) of the preamp tube could have more gain than the other and be more sensitive to the changes!?!?

[JDJ]

Well, I'm taking it to the manufacturer on Saturday, 11/11. He'll bird-dog it and I'll let you know. Winner gets a prize. :)

[Chris Scott]

This one's sure got ME curious--

.......don't forget to let us know!

[JDJ]

Well boys, I'm back from the manufacturer. A nice diversion when one lives with wife plus three daughters. I've been eyeing the treehouse as a bachelor pad, but I digress...

Turns out it was a small metal shaving behind the circuit board in the preamp section getting tossed about by vibrations and causing intermittant noise. An easy fix with no soldering.

As a consolation prize for my troubles and travels, the manufacturer gave me a set of NOS Tung Sol 5881s, a NOS Mullard 5AR4, a NOS RCA 12AY7, and a pair of Raytheon 12AX7s for the V2 and phase inverter.

http://i84.photobucket.com/albums/k36/j616129/Gear/November2006032a.jpg

Thanks for all of your great suggestions. And thanks for the tubes, Mike. :cool:

[Old Tele man]

...looks like a VERY nice "conciliatory" prize for having to "...take her back to the factory."

[rockon1]

Well, I'm taking it to the manufacturer on Saturday, 11/11. He'll bird-dog it and I'll let you know. Winner gets a prize. :)

Looks like YOU got the prize! ;)

[jimmyc]

That's one nice "prize" for a minor little problem! Who is that builder?? I want to do business with him!!

jimmyC

[bluesjuke]

Looks like YOU got the prize! ;)

Sometimes things work out better than you had hoped!
Cool tubes.

[JDJ]

The builder is Mike Clark.

[brad347]

WHOA, great score! Who is this manufacturer? I might just have to buy an amp with 'troubles.'

Now WHERE did I put those metal shavings?

;)