Metropoulos Forum

just finished a 2 hour session of playing - changes V2 and V3 to new Tung-Sols just yesterday.
I turned the amp off when I was finished. 10 minutes later I decided I'd play some mp3 playbacks through it to break in the tubes (and the amp itself which has around 12-15 hours on it so far). when I turned it up the red light flashed for a second and then went off. nothing happened afterwards...

I checked the Mains fuse - it's intact. replaced the rectifier tube (it should power up even when it's not there I believe) and still nothing.

the rectifier tube I pulled out makes clanking noises when shaken. I really hope I don't need a new PT.
what could possibly be the problem?

fast forward an hour and a half - tried again to power the amp up - everything seems to work normal...I'm puzzled...
I don't suppose the Mains fuse I have is of the resetting type so I'm really intrigued how could it be (though I'm thankful that my amp still works).

the problem returned - about 15-20mins of running the amp fairly low (2-5 on the volume) the pilot light turns off or starts flickering than gradually turns off and the heaters of the rectifier tube stop glowing then it comes back or dies completely.
turning the power switch off, unplugging the AC cord than plugging and turning on the amp comes back.

I switched between two rectifier tubes I have and the problem happens with both of them (earlier with a fresh Sovtek GZ34/5AR4, much later with a 1.5 y/o Fender branded Ruby 5AR4). not sure a rectifier tube fail would turn the pilot light off nor do I believe the rectifiers failed since they work great the moment after when I plug it and power it up again.

what should I be looking for - cold solder joints on rec. tube socket? PT heater voltage drops? maybe get a hold of a solid state rectifier to eliminate the option of defective rectifier tubes?
any help would be appreciated.

If the heaters are affected as well then it is from the wall, input socket and primary wires/switch area where you have a problem, maybe switch contact burned, or cold joint.

thanks,
I'll go over the solder joints on the switches, mains cable, mains fuse holder etc.
I'm also suspecting it might be the power strip I use.

btw, I used the 230v tap on the PT. AC voltages measured on the hot terminal of the power switch vary between 228-232 VAC.
I guess it could cut out when the voltages drop too low beneath 230v - am I better off putting it on 220 operation? never had problems with my other amps and appliances which run on 230 and 240 VAC.

Elad E wrote:thanks,
am I better off putting it on 220 operation?

No!

stef wrote:

Elad E wrote:thanks,
am I better off putting it on 220 operation?

No!

whats the reason? voltages drop every now and then below 230, wouldn't that make the amp cut out when wired for 230V operation?

btw, I get 2.9VAC on the heaters of V1-V5 when on 230v, when the amp was wired for 220v I got 3.10v.

Elad E wrote:

stef wrote:

Elad E wrote:thanks,
am I better off putting it on 220 operation?

No!

whats the reason? voltages drop every now and then below 230, wouldn't that make the amp cut out when wired for 230V operation?

No it would not. Even if it were 200V it would still be very audible. You can only fry the tubes and/or melt the iron when going for the 220V tap into 230+ wall voltage
Do what Neil posted

stef wrote: No it would not. Even if it were 200V it would still be very audible. You can only fry the tubes and/or melt the iron when going for the 220V tap into 230+ wall voltage
Do what Neil posted

thanks, now I understand.