anyone experienced cold/cracked solder joints svt classic??

[bakerlite]

So.... This beast is driving me insane    Thought i was on the home straight firing it back together after full tube change and screen reistors change.
I am almost certain its a bad joint but i cant find it -
The problem is that it sounds like a trio is dropping out and one of the bias led doesn't act quite right (The red doesn't flicker on when playing indicating (as by the sound) no action from that side)
 that is unless I  apply a bit of pressure just a finger tip wiggle to either of the 2 12au7's and 12ax7 at the back she goes back to normal sounds gorgeous and the leds act normal but... a loud note is enough to unseat it?
Any common places the joints go bad around here? The pios pot joints didnt look the best  so i did them - I dont want to take the buckshot approach with this so if there is a common spot let me know!
 

[bakerlite]

did ya ever feel like you just went and wasted a day?....

So went a chopstick searching for a bad joint and certainly no sign - i had to do that with the whole amp upsideown and weirdly it worked perfect all the time no tube wiggling needed.

back up the right way and problem back again though still intermittent

The rear of the chassis as well as the 3 tubes and two bias bots seem slightly microphonic (in a kind of buzzy way when tapped with a pencil or scredriver tip)  when the problem manifests itself

as said sometimes a wiggle of ANY one of the three tubes will cure the problem but not all the time.

I am a head scratchin so chime in if ya like!

[Willabe]

So went a chopstick searching for a bad joint and certainly no sign - i had to do that with the whole amp upsideown and weirdly it worked perfect all the time no tube wiggling needed.

That is a big powerful amp with high DCV and high current to be turning upside down and poking with a chop stick! 

No way I would do that, don't care if I fixed it or not. Not worth my life.


               Brad     

[John]

You probably already cleaned the sockets with De-oxit?

[bakerlite]

I sure did - though I have received the liquid pump action can instead of the spray and find it quite messy! its too expensive to waste though.......

BREAK THOUGH!!! My biggest problem has not been able to recreate the issue at will as its intermittent so hard to pin down.

However I just noticed the the "SLAVE OUT" jack about 2 inches down from the axy and 2 au7's is missing its locking nut and washer - sure enough if I apply gentle upwards pressure the problem is gone sound is full , both leds work as normal. and  if I don't touch it the problem is there.... and if the problem is not there a very light downwards pressure creates the problem.

at least I have a better idea where to start tomorrow.

I been at this since 10am and its 1930 now,,,, (ok I had a long lunch but still)  all for a tube change and intermittent partial volume loss issue.

[Willabe]

Sounds like you found it all right.

I don't know how you guys have the patients to stick with chasing down something like that. It would drive me nuts.   

I have a lot of respect for you being able to do that.


             Brad    

[Jack1962]

glade you found your problem , I work on a lot of these monsters , save yourself future problems replace the jacks.

[bakerlite]

Ok.... Tomorrow came and went - but even with my discovery of rocking the slave out the problem dissappeared the next day -??

Also I dont see how a faulty "slave out" jack socket can knock out a trio out seeing as this signal is straight from the preamp and hasnt been split for the output section quite yet -

Today the problem appeared for seconds at start up but has now dissappeared again -

If anyone has any idea where to sniff next i'd sure appreciate it