#1
Hi all!

I've got a Hughes and Kettner Montana acoustic amp to repair, and have hit a brick wall very early on!

Basically the inputs cut in and out, but even when it works it's at a massively reduced volume. The power amp section obviously works as I seem to get full volume from connecting to the "return" of the series FX loop. Thankfully that's before the EQ so it's still usable but it's not perfect..

I've replaced the jack sockets but that didn't help. It's both the "warm" (for low output, non pre-amp guitars) and "bright" (for high output, pre-amp guitars) that have the problem, so it's a wider problem than a single socket.

There is no visible damage to any of the components so I'm not too sure what to look for next.

Any suggestions of what kind of component might be causing this issue? I'm trying to get a schematic from H&K but not sure if they'll be willing to help..

Cheers
PRS SE Chris Robertson
PRS SE EG
PRS SE Angelus Custom
Yamaha SF1000 (Both of 'em)

Laney L20H Lionheart
Marshall 1936 w/ Eminence

Rather large pedalboard..
#2
Sounds like you have a dead/dying preamp valve to me. Or possibly a dirty valve socket. If you turn on the amp, turn up the volume, and then gently rock the preamp valves around does it cut in and out? What type of noises do you hear coming from the speaker when while you are rocking the valves?

Edit: I made the assumption that it was a valve amp. I should have asked 1st, is it a valve amp, solid state, or hybrid? Also, have you tried plugging into the amp with a different lead?
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Last edited by CorduroyEW at May 18, 2016,
#3
Quote by CorduroyEW
Sounds like you have a dead/dying preamp valve to me. Or possibly a dirty valve socket. If you turn on the amp, turn up the volume, and then gently rock the preamp valves around does it cut in and out? What type of noises do you hear coming from the speaker when while you are rocking the valves?

Edit: I made the assumption that it was a valve amp. I should have asked 1st, is it a valve amp, solid state, or hybrid? Also, have you tried plugging into the amp with a different lead?


Yeah sorry, it's a solid state acoustic amp! I've tried different leads and all do the same thing so that's not the problem :/ If only it were that simple
PRS SE Chris Robertson
PRS SE EG
PRS SE Angelus Custom
Yamaha SF1000 (Both of 'em)

Laney L20H Lionheart
Marshall 1936 w/ Eminence

Rather large pedalboard..
#4
I'm going to start this by saying that I'm very comfortable with valve amps but haven't bothered to do the research into solid state amps. What I am going to tell you is what I would do if it were my amp but may not be what you should do.

I'd make sure the amp it unplugged, open it up, and have a quick visual inspection. If there is a frayed or broken wire, or a burnt out circuitry you might be able to see it. Look for any sign in of excess heat like blown fuses, burnt resistors dark spots on the board, or bubbling on any component or the board. If all looks OK I would make sure all the quick connect wire connections are secure. A lot of manufacturers will put hot glue on the connector but that doesn't mean the connection is good so get rid of the glue so you can tell what is helping underneath. Next pull the fuses and check them with a multimeter in just to be sure they are good. Finally I would carefully plug the amp in, turn it on, and start poking each solder joint with something non conductive like a wooden chopstick. Chances are it's a cold solder joint and by poking a bad solder with the chopstick it will pop or click or make a range of other noise. I'd fix the bad solder joints I find or If I don't find anything by poking with a chopstick then I'd take it to a tech.
Not taking any online orders.
Last edited by CorduroyEW at May 21, 2016,