One tube over heating? help!

[german_cargo]

Hey guys,

I thought maybe some of you might be able to give me some help with a question I have about my amp. Its not actually a Mesa... its a 100 watt Traynor YCS 100 with EL34s but still. I've had the amp for about 3 months and I've only really turned it up 3 or 4 times and I had it up this evening and it was sounding SWEET with my new stomp boxes but I noticed some vibrating or distorting in the low end when I palm mute it and once it took a really quick dip in volume. After that happened I took a peak at the tubes and the last power tube on the right, looking in from the front grill was glowing REALLY bad. I flipped it on to stand by and it quit glowing so bad within about 10 - 15 seconds.

I'm a little worried, I don't know if it would have anything to do with my stomp boxes... but can anyone help me out with some ideas?

Thanks!

 

[german_cargo]

ok guys... bad news.

I just turned it on and strangely all I could hear was the reverb. In other words, if the reverb is turned all the way off there isn't any volume no matter what the master or channel volumes are. The reverb is acting as the only volume in that the only way to get any sound from it is by adjusting the reverb.

BTW its spring reverb and it does this in both 100 and 30 watt mode.

Also, after I did the last post I checked and all my ohmages were lined up properly.

Yikes... looks i'm in for some amp repairs. Any ideas as to what happened?

 

[SixVeeSix]

Always on a tube amp that still lights up.........check your tubes first!! Get a known good substitute tube for any tube in question and replace the tube. Never swap out all of them at once, you won't know which one was bad. Take your time and swap out one tube at a time. If nothing changes, replace the original tube and move the tube you are testing with to a new position. Start at the side that the input jack is on and work your way across. A problem with the reverb is likely to be in the preamp section (the smaller tubes). In the case of the glowing output tube, does this amp have a bias adjustment? If replacing just the glowing tube fixes things, fine but keep your eye on it. Maybe put a mirror behind your amp so you can watch the tubes, looks cool anyway You may need to have the bias adjusted on the output tubes, depending on whether or not this amp has that feature. Unless you saw smoke and smelled a foul aroma there is probably nothing too seriously amiss here. Good luck!

 

[german_cargo]

Well if its just the tube(s) thats a big sigh of relief. Co-incidently I started looking at new tubes last week... I wasn't planning on retubing this quick but I didn't like the stock ones anyways!

Yes, it has a bias adjustment... and can take EL34 and 6L6 types. So I was thinking of either going with some JJ EL84s or JJ KT77s.

Doesn't anyone have an opinion on either of these tubes?

 

[domct203]

.....
Yes, it has a bias adjustment... and can take EL34 and 6L6 types. So I was thinking of either going with some JJ EL84s or JJ KT77s.

It's most likely bad tubes. When you say it has bias adjustment, do you mean it just has a switch for EL34 / 6L6, or does it have an adjustable pot in the bias supply?

Also, EL84's are not the same as EL34's (maybe a typo?)

If you know how the power tubes are paired you can remove the bad one and it's mate to run the amp in "half-power" while you trouble-shoot the preamp section. Just be sure to "half" your ohmage (ex. 8 ohm cab into 4 ohm jack on amp).

And you might want to pick up some extra fuses. :wink:

Dom

 

[german_cargo]

I haven't actually looked but I'm quite sure that in the manual it has an actual pot for adjusting bias as well as being able to take EL34 and 6L6.

When I said EL84 it wasn't a typo... but I've now found out that the 84s won't actually work with my YCS100. I'm going to get the JJ KT77s and probably the high gain ECC83S's.

Why do I need new fuses?

 

[Octavarius]

Because when a tube shorts like yours did the fuse most likely will blow to prevent the tube from burning out other internal parts in your amp.

If your amp won't turn on, that means the fuse is blown. Buy a handful of correct replacement fuses. Make sure that they're rated the same as the one that's in your amp now. The fuse rating and voltage should be written somewhere near the fuse socket.

 

[domct203]

Because when a tube shorts like yours did the fuse most likely will blow to prevent the tube from burning out other internal parts in your amp.

If your amp won't turn on, that means the fuse is blown. Buy a handful of correct replacement fuses. Make sure that they're rated the same as the one that's in your amp now. The fuse rating and voltage should be written somewhere near the fuse socket.

+1
When trouble-shooting tube issues it's likely you may blow a fuse. Just don't keep blowing fuses, if re-tubing doesn't help, stop and find a tech. Besides, it's good to have spares (tubes as well), so if anything goes at a gig you can at least get back up quickly with a fuse and / or power tube(s) swap.

Dom

 

[german_cargo]

The amp turns on fine... it even makes a little bit of sound through the reverb. All the lights are lit up and everything... do I still need to change fuses?

 

[domct203]

The amp turns on fine... it even makes a little bit of sound through the reverb. All the lights are lit up and everything... do I still need to change fuses?

Nope. Only if the amp will not turn on.

It's still good to have spares, and they are cheap.

Dom

 

[german_cargo]

I just remembered that late the night before I plugged my bass into it to work something out for a song... It was on so quiet you could easily have a conversation over it, but would that have sped up my tube(s) going?

 

[StratTone]

Sounds like you had a tube short out and take out a screen grid resistor. Just a guess of course. I'm not sure about your model but you may have a bias balance pot and it has most of the current going to one tube and not balanced out properly. Something to check into.