1.6K Ohms resitor turned orange. [resolved]

[clthrt01]

Hello,

I finished my Tode last week.  Everything seemed to check out okay with the multi-meter (some output readings were low, but from some reading, that was to be expected).  I plugged it in, got about 2 notes out and it fizzled out.  Sounded like something fried inside.  A few seconds later I saw smoke.  The 1.6K Ohm resistor was orange-hot and, after it cooled, crumbled.  I replaced it, only to find the same problem.  Any idea what causes this?

FYSA, I'm new to this stuff.....this is my first build of this type.

Thanks
Mike

 

[Doc B]

Don't turn it back on, you have a major short somewhere. The burned resistor is a symptom, but not the problem. Best place to start is to go back over all your connections to make sure you haven't inadvertently wired something to ground that shouldn't be.

 

[Paul Birkeland]

(some output readings were low, but from some reading, that was to be expected).

Which ones?

A backwards capacitor would cause this problem on its own.

 

[clthrt01]

At this point, I don't quite remember which ones.  I would have to go and redo them, which I can do tomorrow.

I think I might have found the short.  The shielded wire that jumps from A4 & 5 to B4 & 5 was fused together about a 1/4 inch above B4 & 5.  While soldering, apparently I let it get too hot and it melted the coating and the wires were touching.  Will this cause my problem, and now that they are separated, can I chance turning it on again?

Thanks
Mike

 

[Paul Birkeland]

That short would certainly keep your amplifier from operating, but I don't believe it's the source of your trouble.

-PB

 

[clthrt01]

Nope, it wasn't.  I also found that I had the poly cap attached to 18U instead of 19U......but that didn't solve it either.  I need to go through the directions step by step because I cannot find anything else that looks odd.  I must have attached something wrong.

Mike

 

[clthrt01]

Turned out to be a really simple issue.  Terminal 5 on the output transformer was touching the metal speaker frame.  I bent the tab in, away from the speaker and viola.

Thanks, pretty cool little amp that I now want to build a cab for so I can hear it through a 12" speaker.

 

[Paul Birkeland]

Thanks, pretty cool little amp that I now want to build a cab for so I can hear it through a 12" speaker.

I'm glad you got it sorted!  Don't limit yourself to one 12" speaker, go for a 4x12!

 

[clthrt01]

Pretty sure my wife would kick me out if I did that.....