Duckie is Quiet, 5e3 squealed a bit and then went silent

In 2012 I built a DIY 5e3 from sourced parts and the help and encouragement of people here at this wonderful forum, you can see it here: http://www.tdpri.com/forum/shock-brothers-diy-amps/313314-duckie-another-5e3-tweed-deluxe-born.html#post3929359 Last night right before a practice it squealed for a second and went silent. What's funny is I had not a half an hour before we got together warmed up a bit and it was fine. I did notice a slight acrid smell and the second 6v6 was blue plating a little but soon stopped. No smoke visible, transformers cool, caps don't seem to be popped or puffy. Checked what if it is not the amp things like the cable between guitar and amp, took the effects out of the equation, tried cable and guitar in another amp. I have been very lucky with my builds any issues were small, obvious, and easily fixed. Entering exciting territory for me, fixing is an opportunity to learn a lot more. I guess next step is getting the B+ voltages? Is there troubleshooting guide or outline people like to follow? Look at stuff coming off the rectifier first, then look at ... Help appreciated in any form, thanks, milkshape


Update: closer examination showed showed the 4.7k resistor between the first and second filter caps is toast. That and probing showed no voltage on B+1.
Fixing now, hopefully this is it.

 

I think the toasted resistor was a symptom as opposed to the problem. I replaced it and switched power on and put it on standby, no smoke, switched it off of standby and the rectifier sizzled a bit and then the fuse blew. I suspect the rectifier tube is done, I checked for shorts and did not find any. I have a spare rectifier in the 5f1 I built but am shy to try it until I get some feedback on whether my suspicions are sound. More research on the net at large is most likely how I will be spending my evening Thanks everyone.

 

Hey ripgtr thanks for the comment, it's a sovtek, new guy. So we have a fireworks show in the rectifier bottle. Pretty sure that's not the operating norm, going to try my other rectifier tube and if that proves to be the issue replace rectifiers in both the 5f1and 5e3 with NOS tubes.

 

Images of the toasted resistor

 

Swapped out rectifier tubes, the one from the deluxe worked in the champ, and the one from the champ shoots sparks when power is applied in the deluxe. Guessing either a short or a bad power transformer. I will go over the connections with the multimeter, but the amp does not move often and I just can't see a short suddenly appearing. I mean vibration can move things around but enough to produce a short? Ideas welcome!

 

Thanks c64 I will get a shot up, the amp has been perfect for 2 years and gets used almost everyday. So I don't believe it is a wiring issue. This is the first time I have opened the back on it in I can't remember how long. So I don't think it is a wiring issue. But more eyes the better. I have a feeling I will be replacing the power xfrmr.

 

Compared the voltages coming off the power transformer of the deluxe with those of the champ. I first removed the rectifier. The champ is steady 480V at pin 5 and 6, while the deluxe is all over the place but never more than 65+/- V. It's crazy, numbers never stay quiet, just keep flipping around

Hackworth - thanks for the reply, so you think perhaps the tube is shorted or the short exists outside the tube? I did notice that the second 6v6 did do a little blue plating when the problem first showed up.

 

Thanks robrob, I will double check that. Was not able to get to it over the weekend. I remember an issue with the heater tap not being grounded and learning about the 100 Ohm y wired to ground trick to eliminate it. The stuff you find here can save time time time. So many newb builders such as my self have gone from 0 to tone by being helped from past and current threads and knowledgeable members. Chances are someone has done it or broke it just like you. Long Live TDPRI.

 

I replaced the resistor and got some new tung-sol tubes but unfortunately this did not cure duckie. I am going to take the chassis out and give it a good visual and electrical inspection to make sure everything is on the up and up. I will post voltages and findings.

I have a sneaking suspicion it is the power transformer. Right now when you turn it on, the rectifier tube sparks, red plates something fierce, and blows the fuse. Even after that the rectifier works fine in the champ I have.

All shots in the dark welcome.

I got the tubes from tubedepot, first order there and was impressed. I fat fingered my address and sent them a note. They responded quickly, like minutes, let me know it was fixed and the tubes arrived earlier than expected.

 

Thanks Commodore 64! that is the kind of similar experience I was looking for. I see a new power transformer in my future.

 

Links were helpful, thanks!

Does Edcor really want $21 to ship it UPS ground!? Man, that's practically 1/2 the cost of the tranny! NE is not the dark side side of the moon. Nice lookin' stuff tho'.