Crack power transformer smells and smokes

[zlib]

Some days ago I completed Crack and it worked well. Then I tried Speedball upgrade. I couldn't make it work properly (only right channel worked and there was some background noise). During the voltage check I found problems in terminals 4 and 5 but then power transformer began to smell and smoke. I turned it off and decided to revert to original Crack.
Now it sounds just like before but in some minutes power transformer begins to smell and smoke again. What should I do?

 

[Paul Birkeland]

Can you post your voltages?

A smoky transformer is pretty rare, but other components under the power transformer can smoke if they are not properly installed.

 

[Doc B]

It may be that a component in the power supply was overloaded by a miswire in the Speedball. First thing to check might be the rectifiers, to see if one has shorted. Put your test leads across each rectifier and measure resistance with the power off and the amp unplugged. Swap the test leads around to the opposite ends of the rectifier you are testing and measure again. If you find one rectifier that measures very low ohms in both directions it is blown and needs to be replaced.

 

[zlib]

Thanks for the answers.
All 4 rectifier diodes are OK.
To check voltage again I need to turn it ON. It will smoke again... I'll try it a little later.

 

[Doc B]

OK, check the tops of the electrolytic caps next, to see if any look bulged. If the transformer overheated with the new speedball installed and continues to overheat with it removed that tends to indicate that the power supply itself was damaged by some problem in the speedball installation drawing too much current. Thus my suggestions for sorting out the power supply before proceeding further. Hitting the transformer with AC is not a good idea until we have an idea of where the problem is. Try redoing the resistance check first rather than going to the voltage check.

 

[zlib]

I resoldered the joints with different solder and now my Crack works fine.

 

[PZAPRTY]

What kind of solder were you using the first time around?

 

[zlib]

Some chinese 60/40. Maybe it was because of bad contacts of 3K ohm resistors (I needed to remove them for Speedball and after that their ends looked not very well).

 

[Paul Birkeland]

Does it say that it's for plumbing?

Does it contain lead?

 

[zlib]

I don't remember now. Old solder is over.

 

[Paul Birkeland]

You probably used plubmers' solder on your amplifier, which contains a conductive flux.  It will basically make shorts across all terminals inside your amplifier, and these paths through the flux will conduct current when the amp is on, heat up, and burn off.  This will repeat until you clean the flux off (with water) or until it burns off.

It can be tough to tell if this is the case, but the arcs should be visible while the amp is running (and audible).