weird Tube Amp problem

[metalj]

Hey i got a weird deal going with my H&K Tube amp.

Ok, so if i go guitar and cable plugged right to the front end and nothing else i can jam on it for like 5 minutes and the sound cuts out and or fades and there is kinda fuzzy static type sounds going on. I might add that in this set up... at first the amp sounds amazing for the first 5 minutes or so before it starts to degrade.

NOW, when i have my effects rack hooked up throught the effect loop i can crank it to 11 and play for hours and have full tone, and it works like brand new. nothing bad ever happens.

Now when i dont want any effects (just to keep me honest when im practicing) i just hook one short cable to the effects loop. One end to the send and the other end to the return. This also yeild excellent results and it works just like new, and i can play for hours.

MY question is.... why would i have to "engage" the effects loop in order for the amp to maintain its normal operation ???

I dont think it is the tubes due to them working perfectly with the effects loop hooked up in one of the above scenerios.

thanks

[metalj]

I might also add some more weirdness to my thread. I have two amps, exactly the same make and model. they both do this.

[vcgeetar]

thats quite a strange issue.... have you tried contacting hughes & kettner yet about it considering it must be a defect in their amps if it is two? Also have you troubleshooted with different guitars to make sure that it is in fact the amps? You say after 5 minutes the problem occurs.... when this happens do you shut the amp off and let it cool down or do you turn it off and turn it right back on? And what happens then? Yes I know this is alot of questions and I don't know how much i've really helped but I guess addressing these questions might provide more information for others to help find a solution. hope you get them working properly again.

[killthepixelnow]

Why did you buy the second one? lol
COntact Hughes & Kettner.

[Anfontan]

I think it might be a problem with cheap jacks in the effect loop circuit. I had an amp with a similar problem, and that was the cause of it. Unfortunately, no one uses the quality jacks like switchcraft anymore-those days are gone~Damn!

[Outlaws]

Originally Posted by Anfontan

I think it might be a problem with cheap jacks in the effect loop circuit. I had an amp with a similar problem, and that was the cause of it. Unfortunately, no one uses the quality jacks like switchcraft anymore-those days are gone~Damn!

Bingo.

There is a probably a cold solder connection somewhere inside in the path where the signal bypasses the effects send. Take it to a tech or return it for a new one if you just recently bought it.

I don't recommend doing much if you are not experienced at working on tube amps, but if you open it up you can look in the general srea of the send/return and look for a solder joint that isn't shiney....it would look almsot cloudy. That or the connection could be broken and its just resting by the weight of the solder.

[metalj]

Originally Posted by vcgeetar

thats quite a strange issue.... have you tried contacting hughes & kettner yet about it considering it must be a defect in their amps if it is two? Also have you troubleshooted with different guitars to make sure that it is in fact the amps? You say after 5 minutes the problem occurs.... when this happens do you shut the amp off and let it cool down or do you turn it off and turn it right back on? And what happens then? Yes I know this is alot of questions and I don't know how much i've really helped but I guess addressing these questions might provide more information for others to help find a solution. hope you get them working properly again.

If i turn it off and let it sit for a while then turn it back on it starts working like i described above. sounds great, then it starts causing trouble again.

Once it starts cutting out and making the noises.. if i turn it off then on real quick it still makes the noises.

H&K's are distributed in my erea by Pearl (what my local store told me). Very little support, and no one really knows them very well so i cant get an answer from anyone. no one at H&K will ever return a call or email.

[metalj]

Originally Posted by killthepixel

Why did you buy the second one? lol
COntact Hughes & Kettner.

They are by far the best sounding amp to my ears that i have ever heard. I bought one new, then found another one used for 1/2 the price that i paid for the new one and i just couldnt pass it up. Now i run them in stereo with my effects rack and its IS the tone of the gods

It is an amazing amp that has its own unique tone to anything i have ever heard, and like i was saying... they both work perfectly with effects loop hooked up.


thanks to all for the suggestions, ill have my store check out the loop connections like Outlaws and Anfontan suggested see what happens.

[Anfontan]

Tell them you are Alex Lifeson from Rush - He's an endorser of the amps. That ought to scare the crap out of them

[gbdweller]

Sounds like dirty jacks in the effects loop. My 5150 has experienced the exact same problem. The jack has a circuit bypass in it that is supposed to be making contact when there is no jack plugged in. A good cleaning of the contact surfaces of the jack may just cure your problem. I use a q-tip soaked in contact cleaner and carefully scrub the contact surfaces. End of problem.

[dgatwood]

Sounds like a thermal problem. Suddenly cutting out like that usually means some solder joint is getting warm enough to separate from thermal expansion, then cool and make contact again.

Probably the solder joint for the normalled contact on the effect send.

Know anybody with a reflow oven? No, seriously, it should be an easy soldering job for somebody even half competent.

[fm #1]

by any chance does the static sound die down if u touch any metal part of your guitar ie the machine heads or the jack socket? if so sounds like an earth problem. i have 3 or 4 amps with tht problem

[metalj]

Originally Posted by fm #1

by any chance does the static sound die down if u touch any metal part of your guitar ie the machine heads or the jack socket? if so sounds like an earth problem. i have 3 or 4 amps with tht problem

hmm, never thought of that. do the strings count as a metal part in your theory and seeing that it only happens when the effects loop is NOT engaged would that still fit into that thinking ??

good thoughts though. something to check into.

last night i practiced a for a few hours with just the one patch cable hooked into the effects loop and had no problems, so maybe its something minor to live with, although technically its bothering me that it doesnt work without the patch cable.

[Clive Hugh]

My set up does that but I've narrowed it down to an ancient Boss CS-2 compressor, if I kick the thing hard it leaps back into life.

[fm #1]

yes as the pedla can cause the same problems any amp can except obviously ones involing the speakers.