Express Problems Pictures

[ampmike]

Hi Guys,
Went to fire it up, got smoke on V4. Can you guys look at the pics on my photobucket and see if you see anything obvious? I'd love to fire this up on the 4th. Blew some fuses also.
Thanks, Mikey



http://s916.photobucket.com/albums/ad2/ ... rainwreck/

[Noel Grassy]

Whutchoo mean by, "...got smoke on V4."? The smoke exited from the
bottle or something in the vicinity? Did you power up with NO tubes and
check everything off on the list in Ron's guide? Do you have more power
tubes you can use when you try starting up again?

[ampmike]

Yea ,If you look at the photo of the back of the tube socket you can see the burn mark,I installed all the tubes and went for it,I know that was dumb.Got smoke out of the V4 power tube.The tubes were tested and good,So Im going to go back and start all over.I believe after the smoke I blew a fuse.
I need to slow down and take it all over step by step I guess.Ill see if I can get some readings without tubes again and Ill post back OK,Thanx Mikey

[Gibsonman63]

I was very tempted to do that as well, but I am glad I didn't. It turned out that I had issues with my power supply wiring.

If you don't have one, build a light bulb current limiter. It will pay for itself in fuse replacements alone. Check all of your voltages without tubes first. I would seriously consider replacing the burnt tube socked. The carbon traces are conductive and could lead to problems later.

Verifying all the voltages should point out where you need to be checking.

[WhopperPlate]

Mike, did you swap out the suspected "bad cap"? Looks like the tube arced from OT primary to the heater pin. Probably want to swap out that tube socket. From the photos the wiring seems correct, but that's as close as I can assess.

What gibsonman said: check all voltages without tubes and post them.

I also see a couple of unrelated things that might cause issues down the line, like your power tube grid wires placement and the snubber resistors lead length. Your NFB lead should probably be moved away from the grid wires. Make sure you trim all excess leads (bleeder resistors).Your treble pot lead wire should float in the air away from the bass and mid leads. Look at pictures of Francesca.

Doesn't look like you have a lead from v2 plate to the v3 .1uf coupling cap; is it just under the board?

Double check every connection and test for resistance/continuity.

I know better than anyone, don't rush the build process. I have spent all night trying to dial an amp in for a show the next day, it just ends up being sloppy and creating more problems down the line.

Happy 4th!

[marcoloco961]

+1 on Whoppers suggestions.

You have 2 red wires coming from the yellow 8 ohm connection on the selector switch. One is the negative feedback wire, the other looks like it connects to the lowest voltage B+ terminal. Is this what I see?? I looked at the layout and see where it might be possible to think it connects from the pic, but it should not.

Also, might want to beef up the heater wires and the jumper for the screen voltage between pin V4 + V5.

[M Fowler]

On V3 pin two there is no wire to the phase inverter circuit?

[ampmike]

What was that Mark?Do you think Im missing a wire,OK I do have some readings Power and standby on
Heaters Good
V1 &V2 Pin 5 -35
V1 pin 1 & 6 No reading That is why I suspected the cap being bad.The new one comes I think today.
V1 p1-0 P6 -0
V2 p1-595 p6-.001
V3 p1 -670 p2-670 Thats about where I stand on the first part of the fireing up,No tubes yet Mikey Thanx Mark I got that wire soldered,Nice work!

[M Fowler]

Mike,

You were missing that wire based on the photos. Wouldn't work well with out the bias circuit buddy.

Mark

[ampmike]

You got an eagle eye Mark,Mikey

[M Fowler]

Any more problems with the amp at this point?

Did it fire up and play?

[ampmike]

Thanks to your great eyes and Thanx Marco,I did have an extra wire off the suspect cap,Now I go 15.50 off the preamps pins 1&6.Should I go for the tubes now? MIKEY Oh also do you think I damaged the power tube socket when I had smoke back before?

[ampmike]

Im also gonna get my buddy rj to send me more wire and redue a lot of the lead dress,Its looking like a mess compared to Jim and Charlie

[ampmike]

Oh Well,I tries with the tubes in ,On standby I had a hum sound,speaker conected,When I hit standbye to on we almost had a fire.V4 somewhere between pins 3 and 6 it lights right up and I shut it down fast!Tube are OK
Im gonna post a new picture with the corections.

[ampmike]

Suppose the diodes were fried,Could that cause the arcing and fire?
OK Do you guys want any voltages with tubes in standby on? Mikey