My tube amp died today

dragon1952

Crap! I turned it on to warm it up....about 15 minutes later I smelled something electrical burning. Looked over to see no lights on. The fuse was blown and when I opened it up I saw a fried resistor. Hopefully it's nothing serious. I've had it since 2005 and I have been so happy with it. I dragged my Yamaha receiver in from the living room until I can get it fixed and bleh.....:( it sucks in comparison. This is almost as bad as when you lose your internet access or your car.

Early B.

Sorry to hear that. I hope it's nothing serious.

Which tube amp do you have?

george daniel

Bummer,,mine is in the shop now for about a week,,kinda' hesitant to call and check.

HB27

dragon1952 wrote: »

Crap! I turned it on to warm it up....about 15 minutes later I smelled something electrical burning. Looked over to see no lights on. The fuse was blown and when I opened it up I saw a fried resistor. Hopefully it's nothing serious. I've had it since 2005 and I have been so happy with it. I dragged my Yamaha receiver in from the living room until I can get it fixed and bleh.....:( it sucks in comparison. This is almost as bad as when you lose your internet access or your car.

Get the tube tester out and see if a bad tube was the problem causing the resistor to fry.
IF you find a bad tube replace the tube, resistor and fuse and give it another go. I love tubes for sound and simplicity. Best of luck and my condolences.
Harry

reeltrouble1

sorry to hear Dragon. Well get her cleaned up with some new parts and you will be back in business.

RT1

amulford

That blows. I would guess you had one of the tubes take a **** and fried it, too. Good luck...

engtaz

That stinkys. Are you able to see the value of the resistor? Good Luck.

dragon1952

This is the Ming Da MC 88-C. Yeah, each power tube socket has the same value resistor. I don't have a tube tester. I had noticed a very slight hum coming out of the right channel recently, where before it had been barely audible. I just thought of something though. I believe that's the same socket where I had a power tube go out last year. These tubes are just 13 months old and probably pretty close to the same number of hours on them as the previous tubes had when that one bit the dust.

BlueFox

That is one of the best things about tube equipment. It can go up in flames. When I was in the Navy I repaired the radar on the F4B, and it was a combination tube-solid state device. More than once, while running on the bench something would burn up. Great fun. While integrated circuits are much better overall, the thrill factor is missing.

As we were taught in electronic school; Don't step on Superman's cape, and don't piss on B+

dragon1952

BlueFox wrote: »

That is one of the best things about tube equipment. It can go up in flames. When I was in the Navy I repaired the radar on the F4B, and it was a combination tube-solid state device. More than once, while running on the bench something would burn up. Great fun. While integrated circuits are much better overall, the thrill factor is missing....

I don't know about that. I was working on a pcb from a laser scanner once with my boss looking over my shoulder. I fired it up after replacing a component and an IC blew up sending a smoking piece right over his head. He had to do the George W. Bush shoe-coming-at-you head fake, and we both went "Whoa!"

Ern Dog

I keep a spare AVR around for that same purpose. I'm sure it's only a temporary thing.

Hawkeye

BlueFox wrote: »

That is one of the best things about tube equipment. It can go up in flames. When I was in the Navy I repaired the radar on the F4B, and it was a combination tube-solid state device. More than once, while running on the bench something would burn up. Great fun. While integrated circuits are much better overall, the thrill factor is missing.

As we were taught in electronic school; Don't step on Superman's cape, and don't piss on B+

Ahhh, the F4. You're lucky you worked AIMD. One night on the boat USS Ranger, me , being a young Airman walked past an F4 in Phase. They were doing Elevator checks and caught me right in the melon. 15 stiches and 1 night in sick bay taught me to stay as clear as I could of the UHT/Elevators.

Gordon

Hillbilly61

dragon1952 wrote: »

I believe that's the same socket where I had a power tube go out last year. These tubes are just 13 months old and probably pretty close to the same number of hours on them as the previous tubes had when that one bit the dust.

That is probably a big indicator right there. (I'm very, very NOOB re tubes ... doing homework/reading/ etc so I can bring myself up to a knowlegable frenzy to want to delve into tube audio in a few months ). Research so far shows tubes all have a life with some brands/types not being much more than an incadescent light bulb. If you have been using your amp about the same amount (including just leaving it turned on), the tube could be just wearing out. Not sure why it would take out the resistor (and possibly other stuff) when bellying up.

engtaz

The resister could have been the problem all along. Try replacing it and give it a try.

ViperZ

engtaz wrote: »

The resister could have been the problem all along. Try replacing it and give it a try.

Being a passive element, a resistor has a much smaller probability of failure compared to the tube. To make it sound more simple, resistor fail very very rarely. As someone mentioned, most likely it was the tube that failed, or the original tube that failed overstressed that resistor so much that it finally bit the dust.

engtaz

if a resistor is crack slightly, it will only get worse. I have them be a problem before but I usually replace it last but the failure rate is small.

dragon1952

From what I have been able to gather, the tube likely took the resistor out.

disneyjoe7

For that resistor to fail like that, it wasn't the only thing that failed.

HB27

dragon1952 wrote: »

From what I have been able to gather, the tube likely took the resistor out.

It's more than possible it was the tube causing the problem.
As previously stated some tubes have a short life. That's due to a couple of issues. Quality of the tube is the first issue. Some tubes are NOT made for higher voltages and are designed and used as a minimum option for original equipment. Cost always being a factor and manufacturers cut cost wherever feasible.
Tube bias is critical to tube life. Some amps are biased to the max to get max output and "boost" the numbers game. Bias is a major cause of tube failure.
Without opening up a can of worms here, Experience has taught me over the last decade or so that the cheap re-issues won't give long life and I'll only use them as a last resort until I can find a good NOS or good used vintage tubes. It's not always possible(cost-availability) and when I use re-issue tubes I keep a very close watch on bias as it's the heart of keeping tubes and circuits healthy. Also, I think that anyone with tube gear should use a tester on your tubes regularly. Also it's a good idea to keep a record of test results on each tube and socket placement.
There's not many set rules to follow just basic guidelines and precautionary moves.
Any part can fail at any time. A qualified tech is always the best bet if possible to make sure there aren't other issues causing this problem or as a result of the blown resistor. It's easy to guess what happened but until you actually run the problem down you won't know for sure and are just "rolling the dice".
Good luck with the repair and let us know what the final results yield.
Harry

dragon1952

I've ordered a new quad of EH KT88's. That's what I had previously and I really don't want to change the sound. On the suggestions from a tech I've been exchanging emails with, I will replace the screen resistors with 5W wire wounds. I have measured all the surrounding resistors and they all look good. The recommended bias for my amp is 41 mA, which is well within the 37-50mA spec for the KT88. I will be more conscientious about checking the bias this time.

dragon1952

Problem is fixed! A 19 cent repair....woo hoo! Well......plus $125 for new power tubes anyway. Replaced the fried resistor, and powered up without tubes...checked all the voltages and everything looked fine. Put the new tubes in and biased them to .41v, then let it sit for about an hour. Checked the bias again and it was right on, so I fired up some tunes and I was back in business. No more hum in the right channel either

disneyjoe7

Nice, funny but a $.19 resistor cost is all that schooling you had to know what to fix and why. That was the total cost.

Glad to see you fixed it.

HB27

Glad to hear you got 'er up and running. Keep close watch on the bias every few hours until you're sure that they'll stay stable.
New tubes can surprise ya at any time.
Harry

Blownrx7

dragon1952 wrote: »

Problem is fixed! A 19 cent repair....woo hoo! Well......plus $125 for new power tubes anyway. Replaced the fried resistor, and powered up without tubes...checked all the voltages and everything looked fine. Put the new tubes in and biased them to .41v, then let it sit for about an hour. Checked the bias again and it was right on, so I fired up some tunes and I was back in business. No more hum in the right channel either

Did you ever test the old tubes? Or, did you at least test the tube that was attached to the blown resistor?
Most electronics repair places still have tube testers. They may charge you a few bucks but it is better than throwing out a potentially good tube or, worse, putting in a bad tube and watching fireworks again.

organ

Sounds good. Glad to hear it's working again. It was probably a short in the tube.

dragon1952

Blownrx7 wrote: »

Did you ever test the old tubes? Or, did you at least test the tube that was attached to the blown resistor?
Most electronics repair places still have tube testers. They may charge you a few bucks but it is better than throwing out a potentially good tube or, worse, putting in a bad tube and watching fireworks again.

Believe me, I wouldn't put the old tubes back in without having them tested. Also, I live in a remote area. We're probably lucky to have a Radio Shack :rolleyes: I may send them off somewhere though. I've got the first set (JJ's) that blew one that I'd like tested too.

tom t

this is why my next amp will be solid state. if dragon1952 dident know how to fix it on his own,the shop would of been at least $100