5e3 blowing PTs

I've got a Weber 5E3 that blew a PT a couple of months ago. I wasn't too concerned and swapped in a Magnetic Components DR PT. Worked fine for a few weeks and now it's dead again. I don't think the fuse even blew. I've been running a Copper Cap 5Y3 rectifier. Anyone have an ideas what might be going on?

I checked and the fuse didn't blow. All the connections from the PT are soldered and shrink tubed. Grounds seem solid. All the wiring at the tube sockets looks good. The amp was running fine and then yesterday it wouldn't power on. If if turn it on and put my ear up near the PT I can hear a very slight hum.

Is it warm/hot? Did you check the voltages on the various taps? Continuity between the windings?

It wasn't running hot and it didn't die when the amp was on. When it worked the amp was quiet and sounded good. Just wouldn't turn on one day. To check the voltages on the various taps would I measure between the tap and ground? How do I check continuity between windings? The tubes aren't heating up.

Was the Weber PT a W025130? Do you still have it? You can bench check it for continuity between each winding...the primary black/brown....secondary green, red and yellow wires. Then check if there's continuity between each secondary and the CT, if there is that's good. There should be no continuity between each set of windings.
If all seems ok then you may want to try and apply mains voltage to the PT and check the secondary wires for their actual voltage readings.

Read this carefully as a guide..

http://www.paulrubyamps.com/info.html#FirstPowerUp

Take things one step at a time

I don't still have the Weber.

It was center-tapped and the Magnetic Components isn't so I was getting hum until I added a pair of 100ohm resistors from the pilot light to ground. Did I miss a step when I added the artificial center tap that killed the PT?

Have you checked the PT's heater taps for voltage?

Did you disconnect the center tap when you intsalled the 100 ohm artificial C/T? you can't do both.

Here is the first question that needs to be asked. Was there an analysis of the amp before and after the PT repalcement? Waht were the voltages with the new PT? What was the current draw? IF not, then the replacement of the PT was incomplete. Probably more often than not, a blown trannie is the symtom/result of a problem as opposed to being the primary and only problem in the circuit. In other words and with all due respect, this amp needs a tech, imho.
That said...and if you know how to drain the caps....
Disconnect the PT connections and check for continuity as suggested above. Also, check for continuity between all of the windings and ground...the frame of the PT. A transformer can show correct continuity in the windings but be shorted from somewhere to ground. IF you don't check for this, you will miss it, right? There should be no contiuity between any winding and ground, obviously...as long as the widnings are disconnected from all points. IF there is continuity in the windings and no continuity to ground, then one starts measuring voltage from the AC in through the PT.
Good luck with it....and IF this 'new' PT is bad, a tech might have saved you a PT if you had had the work done by someone who would have installed the PT and then assured that the amp was operating properly in all other respects.

While I've built a few amps and re-capped a bunch there's a gap in my knowledge when it comes to troubleshooting and checking voltages and such. At this point the only thing I can think of that might have happened is that I changed a few components on the turret board and some solder might have dripped out the base of the turret and contacted the chassis.

If I connect a meter between the heaters and ground there is no voltage. The MC PT has no center tap. Wally- thanks for the advice. I'll report back here when I've tried your suggestions.

TNO, no judgement here...just an observation. Ime, it is imperative to understand how to check voltages and current draw if one is going to recap, build....do whatever work on an amp. That is about the first thing I did with one. YEs it is dangerous to work on live circuits....but without reading voltages and current, there really isn't a lot that one can understand about these things, is there? One might get sound out of an amp after a repair job , a retube, or out of a new build; but without knowing the voltages and the current draw, one is never going to know exactly what is going on there. IT takes a very experienced ear to 'hear' that an amp is running properly, ime and imho. Adn....even when I like the sound that is comoing out of an amp, teh votlages and curretn draw give me good clues as to why that sound is what it is. IF I want, I can then repeat the situation in that amp again down the line....or in another amp like it.
When I put tubes in an amp, the first things I want to know is what are the plate voltages and what is the current draw.

IF you are reading no heater current from the heaters to ground.....AC voltage setting, correct???... then you should be ready to start reading other voltages. IF you are not versed in the safety procedures, then step away from the amp. This is a warning to absolve me of any responsibility if you suffer an accident while working on this amp, right?

Check the AC voltage in. IF you have AC voltage to the PT adn out of that PT on the read wires, then take some readings in DC voltage setting of the vaious points along the circuit where votlage should be present. IF you built the amp, then you should know where these points are. REfer to the daigram and schematic that helped you build it. IF the kit did not provide voltage information, then the kit provider is lagging behind in their job, imho. You need to be able to read the AC out of the PT to the rectifier, the DC B+ out of the rectifier, the DC out of all filter caps, and the DC at all plates and other pins of all tubes where DC voltage should be present.
Sit and look at your diagrams and schematics until you understand this....and then proceed if you feel confident that you won't kill yourself in the process. IF you have fears....then stop working on amps until you understand things well enough not to have fear....have respect but no feaer that will undermine your concentration on what you are trying to do. IF studying the layout and schematic doesnt' get you there....or even if it does, I have to suggest that you start studying up on these things that you have been workign on. There are a lot of good books out there....too many to list and many that I haven't read or seen...and should. Tom MItchell's 'How to SErvice YOur Own Tube Amp is a very basic book written in layman's terms....good starter. DAVe Funk's book is a great book for Fender amps.
Many, many other books to read...from basic electronics to specifics on guitar amps.
I am not the best or most knowledgable tech on these pages...but I would never have recapped an amp before I knew how to read the voltages in one.
I certainly wouldn't build one without understanding what voltage does what and where to some extent.
BEst of luck with it...and be careful. ONE hand behind your back, please. A shock in one hand will hurt you. A shock traveling from one hand to the other crosses the heart....and might stop it permanently.

It's your heater wires. They are shorting to the chassis or to each other, somewhere. Possibly intermittently. Check everything around the pilot light, and the pilot light hardware itself. The light hardware is often very cheaply manufactured so check for continuity between the 2 terminals, and between each terminal & ground.

If that's OK then go through the string to each tube socket.

BTW this all has to be done with the PT heater wires disconnected.

Beware the copper cap, I got a bad bunch when they first came out...

If this was a new build I'd be inclined to suspect a bad ground or faulty connection.

But this thing worked, if only for a while.

I'll also second Wally's key point. While it is possible for a power transformer to fail on it's own, they typically don't. Meaning that when one goes bad it is usually evidence that something else is wrong, and that something else killed the PT.

Dropping in another PT without finding that underlying problem is probably gonna be a death sentence for the new PT.

At this point I'd pull the PT and test it on the bench.

... Dropping in another PT without finding that underlying problem is probably gonna be a death sentence for the new PT.

At this point I'd pull the PT and test it on the bench.

+1, or at least fuse all of the PT secondaries accordingly.

I don't still have the Weber.

It was center-tapped and the Magnetic Components isn't so I was getting hum until I added a pair of 100ohm resistors from the pilot light to ground. Did I miss a step when I added the artificial center tap that killed the PT?

Did you originally have the filament CT grounded? If you add the faux filament CT, you need to disconnect the filament CT.

http://www.tdpri.com/forum/shock-brothers-diy-amps/341968-5e3-blowing-pts.html#post4348701

5 star post. :idea::idea::idea::idea::idea:

IF the kit did not provide voltage information, then the kit provider is lagging behind in their job, imho.

Wally,

If no voltages are provided, are calculated voltages close enough?
If they are, what kind of deviation in voltage readings is close enough to the calculated values to keep the amp and operators healthy?

~Thx

Filmis, there are so many variables there that I don't care to respond. IF I were to put ktis out for salae, then you will see votlages wiht the schematic and diagrams.

Adn on this note, I leave this thread....andmaybe it is time to take some time off. I spend a lot of time here....and i may just take the advice that was given to me in a PM by filmix....and I quote....

"I know it is in your nature to look out for folks, but maybe it is time to pass the "safety" torch on to someone else. We all respect and enjoy your posts, so let someone else do the housekeeping so you can just sink your teeth in to the good stuff."

Ya'll have a good one.

Well, I found the problem. Bad solder joint at the pilot light. I couldn't see it until I pulled the chassis out and examined it upside down. So I'm a lucky idiot this time. I really appreciate all the responses.

Glad to hear you figured it out.

I just wanted to say that I discovered a problem when using a fender style pilot lamp.

The thin metal plate that holds it all together can become twisted or distorted, especially when tightening the nut that holds it to the chassis. This caused the side of the bulb's base to make contact with the metal portion of the jewel. Grounds one side of the heater and raises hell. Not directly related to what happened to you, but it is something that I will be double checking on the next build.

Mark

Glad you found the problem. Too bad the first PT was repalced before it was realized that the only problem was a bad connection on the heater filament circuit. Without that heater filament voltage to the tubes, an amp will be silent. This is where checking voltages would help a person out. A multimeter properly used would have told your eyes where to find that bad connection.
How? Your heater filament voltage from the PT was good at the pilot light, but that voltage was not present the tubes due to the bad connection of the lead from that pilot light to the tubes. Regarding finding the problem by 'eye'...that was a working solution on this one, but sometimes a solder connection can be 'soild' and look to be a good connection without having the ability to conduct current. A meter will find a problem like this every time.
I would think that you are lucky you didn't waste the expense of another PT before you found the problem. Hmmmm...price of a MM PT versus a dab of solder and enough electricty to heat a soldering iron??? We all live and learn, right? Again, kudos on finding the problem.

Yeees Wally, I heard you the first time but thanks for playing.

You're welcome. Post #7 by Keyser Soze on August 4th and my post #11 of that day both would/should have led directly to the problem in about 30 seconds of mesauring voltages or continuity along that heater circuit. Glad you figured it out a week later.
What finally led you to the solution?

Wow, someone needs a chill pill.

Wow, someone needs a chill pill.

Yup. *somebody* does.

/mirrors
//such a concept