Reverb problem

[NWBasser]

I think I finally isolated my amp's noise problem to the reverb. As you may recall, I was having trouble with my Hughes & Kettner Edition Tube breaking up on the clean channel. I thought it was tube trouble, but the breakup wasn't a nice and smooth tube one. It's pretty harsh and nasty.

I don't why I didn't do this earlier, but today I turned the reverb down all the way and lo and behold it held a nice clean tone up to a decent volume. I turned the reverb up and got the nastiness.

I sprayed the contacts to the spring reverb with cleaner, but that didn't do the trick.

Anything else I should try?

[FrankenFretter]

Shake the living $h*t out of it? Oh wait, use a m0th3rf*cking hammer. Just ask Brian!

[otaypanky]

I'm not familiar with that amp but with the Fender style and Allen amps I use, a bad tube could cause those symptoms.

[sumitomo]

Shake the living $h*t out of it? Oh wait, use a m0th3rf*cking hammer. Just ask Brian!

If your interested that is Snap-On tool #BFH.Sumi:D

[tunghaichuan]

Is it the Tube 20? If so you can find the schematic here:

http://www.schematicx.com/schematic/hughes-kettner-tube-20-schematic/

The reverb is opamp-driven, so no tubes to deal with. It could be a lot of things, so I'll insert my stock advice here: you probably need to take it to a tech, unless you are skilled at repairing pcb-based solid state circuits.

[NWBasser]

Shake the living $h*t out of it? Oh wait, use a m0th3rf*cking hammer. Just ask Brian!

The legend of the MFH is born!

[Tig]

It's hammer time!

http://pages.uoregon.edu/mandyl/cat/HammerCat.jpg
http://www.roadsideamerica.com/attract/images/ak/AKHAIhammer_hovde.jpg
http://community.crystaltech.com/wp-content/uploads/2009/10/BigHammer22B.jpg

[otaypanky]

http://i173.photobucket.com/albums/w49/otaypanky/images-1.jpg

[NWBasser]

http://i173.photobucket.com/albums/w49/otaypanky/images-1.jpg

:rollover

[player]

are spring reverb amphs a thing of the past? even my practice amph has one.
Hughes & Kettner have been around awhile.do they only do Tube verb now?

[NWBasser]

are spring reverb amphs a thing of the past? even my practice amph has one.
Hughes & Kettner have been around awhile.do they only do Tube verb now?

It's a tube amp with transformer driven spring reverb.

[player]

It's a tube amp with transformer driven spring reverb. I would have to say out of the last dozen or so Tube amps I've owned I have not seen a transformer driven reverb unit they were all independent of the amp electronics(at least to the naked eye) and all spring too.come to think of it adjustable spring at that.Marshall,Fender,Orange and a Vox extemely adjustable.others I had to take time out to do it if it needed it or I wanted to.always been decent at modding or fixing em if needed.

[NWBasser]

I would have to say out of the last dozen or so Tube amps I've owned I have not seen a transformer driven reverb unit they were all independent of the amp electronics(at least to the naked eye) and all spring too.come to think of it adjustable spring at that.Marshall,Fender,Orange and a Vox extemely adjustable.others I had to take time out to do it if it needed it or I wanted to.always been decent at modding or fixing em if needed.

Adjustable?

Can you change the spring tension or something like that?

[jim p]

This is a combo amp from what I see on the web so you could remove the reverb tank from the amp to see if it is an acoustic feedback problem. Just put the tank on the floor, stack of books or something high enough so there is slack in the RCA cable. You may want to try another RCA cable and make sure it is not pickup from how the cable is routed in the cabinet. Instead of removing the reverb tank if possible you can use the amp as a head and play through a cabinet to help isolate the reverb tank from vibration as a test. I would need to see a schematic to have any other ideas on a solution aside from trying another tube for the reverb driver and or the reverb recovery amplifier.

[NWBasser]

Thanks much for the suggestions Jim. Unfortunately it doesn't have RCA connections for the reverb. It does seem that the reverb would be very susceptible to speaker vibrations since it's close to the driver.

AFAIK it's not a tube-driven reverb. The exposed location of the springs to the speaker suggests a bit of poor design. That may expain why it gets worse with volume, i.e. more speaker movement = greater interference. Methinks a reverb tank would have been a better option to isolate the springs from the driver.

I may chuck it and go with an outboard unit.

[jim p]

A couple of questions is the reverb OK up to a point as you increase the volume? Also did you try playing through a cabinet connected to the head section of the amp? If you do not have a cabinet if you removed the head from the cabinet and then connected the speaker that maybe enough isolation to give you an idea if acoustic feedback is the problem. Is the amp the same as in the schematic linked above? If it is then there maybe some component value changes that would have an effect depending on what the problem maybe.

[Spudman]

I had that amph and cranked it at gigs. I never had a reverb problem with it. Isn't that circuit tube driven? Could it be a funky tube? I did have tube issues with mine that were really annoying.

If it worked before without the reverb issue, and then as time went on you started to notice the problem, then that might suggest a component that could change over time, like a tube.

[NWBasser]

I had that amph and cranked it at gigs. I never had a reverb problem with it. Isn't that circuit tube driven? Could it be a funky tube? I did have tube issues with mine that were really annoying.

If it worked before without the reverb issue, and then as time went on you started to notice the problem, then that might suggest a component that could change over time, like a tube.

Spud, the amp is new to me so I wouldn't know how long this has gone on or how it started. I put new JJ tubes in it after I got it. It has 2 12ax7 preamp tubes and 2 EL84 power tubes. I'm not sure how the those tubes would be used in the reverb circuit.

What tube issues did you have with yours?

[NWBasser]

Is it the Tube 20? If so you can find the schematic here:

http://www.schematicx.com/schematic/hughes-kettner-tube-20-schematic/

The reverb is opamp-driven, so no tubes to deal with. It could be a lot of things, so I'll insert my stock advice here: you probably need to take it to a tech, unless you are skilled at repairing pcb-based solid state circuits.

At first blush, that looks to be the right schematic, but it depicts 4 of the EL 84s and mine only has 2. I also see what appears to be RCAs going to the reverb and in my amp there are no RCA connectors.

I'll check that site a bit to see if I can find the right schematic.

Thanks much.

[Spudman]

What tube issues did you have with yours?

I had a clock running in mine. It was a steady tick, tick, tick, and some other noises. I took it all the way across the state to an authorized service center and they "couldn't find anything wrong." Brought it home and immediately it was doing the same thing (losers at the service center). Switched out some tubes and never had the problem afterward.

[jim p]

The EL84 tubes are just labeled tube 3 and 4 in the schematic there are just two EL84s on the schematic that I see. Being that there are op amps on the +/-15 volt supplies in the signal chain all over the amp those supplies are probably OK. There is an adjustment pot PT110 labeled SYM adjust you could note the current position of the pot and dial it back and forth a few times then back to its original position. This pot looks to be to center the operating point of the two transistors gain stage of T4 and T5 for symmetrical clipping. With a little luck maybe the wiper has a bad contact and exercising it will clear it up. One thing the reverb signal will do is to increase the peak to peak signal when in phase with the clean signal so maybe the SYM adjust will have an effect. I think the schematic is in error on where it shows the reverb return signal and feedback connection because in a simulation that setup would not work. Looking at the schematic there is a master control as well as lead master, clean volume and tone controls. You could try dialing the clean volume back and turning the master up in case it is clipping in the preamp sections before the power section that is the cause of the problem. If the problem is due to overdriving the reverb tank R48 the 22 ohm 1 Watt resistor could be doubled to 44 ohms to reduce the current on the input transducer of the reverb tank.

[gregsguitars]

1- check and change tube(s).

2- does the reverb work ?
if not,

3- reverb drive or transformer (small ) could be bad.

4- check caps for leakage

5- check for a short in the chassis somewhere.

[FrankenFretter]

It's so cool that we have so many people here that know all this stuff. Just one more reason I love The Fret.

That said, I still say...USE THE BIG HAMMER!
http://i49.photobucket.com/albums/f268/zdoubleedge/MK1BattleHammer.png