trinityamps.com

I figured I'd start a know thread for this one because I'm totally flummoxed by this problem. I rewired all of the tube sockets and reflowed all of the components on the board and the crackle at the MV continued.

I set out to check my voltages and that's where all the weirdness begins.
No tubes installed.

Wall 124VAC
Indicator to Mains 124VAC
Power switch both lugs .415VAC
Power switch to fuse .415VAC
Fuse to AC mains .408VAC
Heaters at tagboard 3.5VAC
Rectifier:
Pin 1 320VAC
Pin 7 320VAC
Pin 5 3.7 VAC
Pin 4 8.08 VAC (should be 0)
B+ on cap can 11.5 VDC

I followed this layout
viewtopic.php?t=493
This layout shows the black and white mains neutral from the transformer going to the pilot light.

For the rest of the amp I followed the layout from 12/3/05. This layout shows the black and white mains neutral from the transformer going to the bottom lug of the power switch.

Which way should it be wired and could this be part of the cause of the crackle problem? I'd like to get this sorted out cause I'm itchin to play.

Thanks,
Joe

That's the correct layout. The one that shows the black and white mains neutral from the transformer going to the pilot light. You followed a correct layout for the rest of the amp.

I just built an amp that develped a crackle. Lbet & I found a cap on the tone control of the normal channel, was not soldered.

Check everything in the chain that is unique to that channel. Resolder at will.

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Could a bad pre amp tube or bad tube socket cause this crackling? My DDM showed continuty all across the board on the components.

Sure that could be, but continuity is one thing. When everything starts to vibrate, that's when the sparks can fly.

However, checking all the mechanicals on the crackling channel is good as well.

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Ok. I'll go over the board again. Did those voltages I posted look right?
Seemed off to me. I dunno being a newbie. Where should I check on the TMB side??

Thanks,
Joe

Check the off board parts & connections as well. This is the TMB channel only or both channels?



No, those don't look correct, but I'd like to see how they were measured. I dont pay a lot of attention to AC voltages if the B+ and tube voltages are good. The important voltages are posted in the forum. Use them as reference.

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

So I basically spent the whole day re-wiring the amp. Components, pots, sockets, mains, input jacks, etc. Any underboard wiring that appeared ok I left alone. Reflowed all the solders on the buss bar. I tried contact cleaner, compressed air....yadyadayda. This amp wants to be right, I can hear it, there is pilot error somewhere on my part.

The normal channel is fine, actually, great. The TMB channel is fine for 2 to 5 minutes, sounds good. Then the crackle starts. It fades up. The chopstick reveals nothing. The crackling varies from just sort of a popcorn type noise to loud pops. Here are the voltages with tubes in.

Wall voltage: 124 AC

V1
p1--140
p3--1.09
p6--134
p8--1.08

V2
p1--179.3
p3--1.64
p6--266
p8--180

V3
p1--215
p2--55
p3--77
p6--201
p7--53
p8--77

V4
p3--12
p7--354
p9--343

V5
p3--12
p7--354
p9--343

V6
p1--309
p3--365
p7--308

Sorry to be such a pain in the ass, but I'm real close and, frankly, lost.

V1 p6--134 looks about 30V low. This part of v1 is supposed to be on the Normal channel.. Is it?

bevins cross connected them and he ran into problems.

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

v1 p6 is conected to c15 which feeds the normal channel. I swappped pre amp tubes around until I came up with a combination that gave me about 6 minutes of silence then the waterfall came back. Maybe it is a bad tube. I'm going to try and get another set of pre-amp tubes from a local music store tomorrow. In the meantime can someone explain how to retension the pins on the sockets? I might as well try that as I have pretty much exhausted all other possibilities.

What I don't get is how a bad tube would only affect the TMB MV. Why wouldn't I have the same problem on the normal side? I know all three pre tubes feed both channels, but it's different pins for each socket...gain, tone stack etc. Just curious.

Thanks,
Joe

Sorry you're having all this hassle. v2 is unique to the TMB channel and half of v1.

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

neon,

Check out these sources of help:

http://ampage.org/htac/faq/tube.amp.mini.faq.html

http://www.diyguitarist.com/Misc/J_Darr.htm

and specifically

http://www.diyguitarist.com/PDF_Files/j_darr8.pdf

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Stephen thanks for the links. I think??? I may have discovered the problem or at least part of the problem. There is some solder in p1 of v2.
The tube would seat, but I can see how the solder heating could create problems. It was very hard to see. Could I be on the right track here?

Is there a way to get the solder out of the pin or should I just replace the socket? Again, thanks for your patience.

Joe

Easy enough to find out, do a chopstick test on the pin with the amp on, you will soon find out if touching that pin with the end of your chopsick causes the crackle to be worse. To clean it you should be able to heat the pin up with your iron and blow hard into the top of the socket. My money is on a dry joint somewhere so if that is not the culprit try using the chopstick on each of the components in turn. Word of warning, use a wooden chopstick NOT one of those fancy stainless steel ones Don't get despondent, out of nine amps I have built so far it is only the last two that have fired up with no issue (and one of those ended up with a bad tube)
Nigel