carlsbro tc60-el34 socket problem

[jcs]

this amp has new electrolytics and a rebuilt bias section..

when i got the amp it blew an ht fuse, i was using some low draw el34s biased around 25 ma..

i found a faulty 12ax7,replaced it, tested everything else again in my b&k 600 and loaded it back with tubes and a 1/2 amp fuse..

with my hoffman bias meter installed, the amp fired up fine, i let it idle checking both tubes turning the amp on&off,it idled around 25 ma per tube for a half hour at least..

the trannys are cool,no weird noises the el34s warm to the touch..

at this point i plug in a guitar and immediately i see smoke from one el34 socket..

at first i suspect a screen resistor and then notice a slight melted sopt between pins 2 & 3,the sockets do show signs of being hot btw but were like this before this problem..

any idea what i should check next? the screen resistors are 1k-5 watt..

did the socket have some carbon that caused the arce possibly? jcs

[Mark Black]

Arcing between pins 2 & 3 is fairly common since the heater circuit is probably at or close to ground potential and that B+ right next door is itching to get there, especially with flyback voltage peaks.

In minor cases you can sometimes scrape the carbon off but often a new socket is your best choice.

Don't forget to look at the tube base as well - carbonized paths can form there too.

Mark

[Enzo]

Really, you are better off replacing an arced socket than trying to "save" it.

Did this amp start out life as an EL34 amp? In other words aer BOTH pins 1 and 8 wired together on the EL34 sockets?

[jcs]

yes it started life as an el34 amp and 1 and 8 are together..

i figure a pair of ceramic sockets are in order,anything better?

any other suggestions or advice?

a good tech friend is going to wire it for me when i can get the amp to him.