Metropoulos Forum

I am constantly having problems with this amp, it is a handwired clone. I hope someone here can help me troubleshoot. Here is what has happened:

1. Daughter flipped the on off switches over and over and blew the mains transformer - replaced with genuine Fender.
2. The amp played awesome for a while and then all of a sudden started crackling and fading in and out. - Sligo installed new switchcraft jacks and carling switches - Ran fine for 2 weeks.
3. At a gig the power started dropping in and out and I saw smoke!! I saw a spark shoot across the filter caps - I blew the amp out and cleaned it and it worked fine for two weeks.
4. At another show, when I would kick in the OCD pedal, the amp would fade in and out and start crackling again.
5. Changed the tubes to Ruby and it has worked fine for a few weeks.
6. Now it works great for about 20 minutes and then starts fading out again i turned the volume up and down and it didn't get loud at all, sounded like a 5 watt amp, flipped the standby then back on and now it's fine. Could it be the filter caps, OT? I have had copper cap rectifier, Tube rectifier, switched all tubes and it still takes a dive out of nowhere. Where do I start troubleshooting and taking voltages. It has two 6L6's, GZ34 Rect. and 12AX7's. Maybe someone could give me a list of voltages to take with tubes in or out and I could post them to isolate the problem, Thanks

Dax-The-Ax wrote:1. Daughter flipped the on off switches over and over and blew the mains transformer - replaced with genuine Fender.
2. The amp played awesome for a while and then all of a sudden started crackling and fading in and out. - Sligo installed new switchcraft jacks and carling switches - Ran fine for 2 weeks.
3. At a gig the power started dropping in and out and I saw smoke!! I saw a spark shoot across the filter caps - I blew the amp out and cleaned it and it worked fine for two weeks.

An arc of any kind would be a sign off trouble. Do you have a cap can over the filter caps? What do you mean by "blew the amp out", compressed air? Have the filter caps changed and make sure they are wired correctly. If you don't have one now, have a cap can cover installed. What size filter caps are in it now? The "genuine Fender" transformer, is it for a reissue 59 Bassman? They run much higher voltages than what someone might use building a clone. It could be out performing the voltage limits on your filter caps.

It's a sign of old carbon resistors going bad.
Very common in old fender amp. Replace with Metal film resistors.
As far as smoke, which you cured by blowing the amp out, you did not fix anything.
Get the amp to a good tech. A good tech will fix it in 1-2 hours, and then it will work for years.
Arcing: the socket must be replaced, cleaning it is useless. The problem will reoccur unless the socket is replaced.

Cause of arcing: bad speakers, bad speaker cable, using a shielded cable for a speaker. This will make the tube sockets arc.

If the repairs from your current tech last 2 weeks, get another tech. A professional knows how to fix it right.

Look for bad solder joints on your tube sockets, or a bad 470K Screen Grid Resistor on the power tubes Or a bad tube, I am running all NOS in mine with a 12AY7 in V1 WTF why Fender put 12AX7 in that slot PS: Those Ruby GZ34 Rectifier Tubes Suck

yladrd61 wrote:Look for bad solder joints on your tube sockets, or a bad 470K Screen Grid Resistor on the power tubes Or a bad tube, I am running all NOS in mine with a 12AY7 in V1 WTF why Fender put 12AX7 in that slot PS: Those Ruby GZ34 Rectifier Tubes Suck

+1 on the cold solder joint.

Nagging intermitent problems are often cold solder, in my experience, and can be real easy to miss unless you are chop sticking a running amp (keep one hand behind your back and only use non-conductive chop sticks or have a pro do it because this is very dangerous) or looking through a big magnifying glass at each and every joint. You might want to check the can connections on your filter caps for visual traces of arcs--> your cap could be defective and this is causing all of your problems.

best of luck,

Tom