Loose pots on my New "Old" Hughes & Kettner

[rookie]

Hi folks!!

I am just bought a second hand Hughes & Kettner ATTAX 40 first edition, the one with the blue carpet cover..

I just have my first test and the amp is in good sound condition but in very poor aesthetic condition. There is only one pot (the reverb one) that is tight when spin, and all of them are loose. Anyway, the amp sounds good
without any weird noises or pot scratches. I´m going to change the buttons but i´m not sure if to change the pots because they seem to work properly but they seem may last not so long too.

I am thinking to put the sanding machine on duty and remove the carpet cover, and then apply some kind of wood protective lacquer to the cabinet. Any suggestions?

[joecool85]

I wouldn't worry about the pots unless they start acting up.  Sometimes they do get quite loose and spin freely but work that way for years.

[rookie]

OK, i could pass on that, but i really want to gave this old puppy a new fancy look. I really have no idea where to find a carpet-like covering or how cheap it would be so its for that i said about refinishing in natural (maybe tainted) wood.
The knobs are like the silver Marshall styled knobs. Any online store recommendation?

[teemuk]

So I am thinking to put the sanding machine on duty and remove the carpet cover, and then apply some kind of wood protective lacquer to the cabinet. Any suggestions?

First make sure that there actually is any sort of wood layer to lacquer. Even if it was a hardwood / plywood cab there will still be a lot of work to sand off all glue residues, not to mention to make the surface finish top notch so that the lacquer won't reveal pretty much all dents, scratches, etc.

Personally, I'd just recover the cab or leave it as is. It doesn't look half that bad in the photos and if the amp already sounds great why care too much about the looks. It's just a basic workhorse amp, not a supermodel.

[rookie]

Yea, in the photos it does not seem look that bad, but it is cause of the flash light of the camera, it makes the carpet covering looks almost like new, but the fact is there are large zones of the surface over painted,   like when you have a gum in your hair, if you permit me that analogy,  and that´s pretty awful. But like you said, there is not a fancy boutique amp, so probably does not deserve so much effort.

I was planning to using something like that http://www.amazon.com/3M-Hookit-9173NA-5-Inch-Reusable/dp/B00004Z4E0/ref=sr_1_1?s=hi&ie=UTF8&qid=1335457816&sr=1-1, and remove completely the cover, but I am going to try removing the paint with a hard brush instead.

In photos does not reflect, but all the knobs except two are blended or chipped. So I have to find a source of 8 cheap aluminum/plastic Marshallish knobs for sure.

It is only I enjoy with things looking good around my room, actually I did want that amp for home practice, but I am understanding by now that you have to turn up the volume a little bit to get better sounds of it.

What is your consideration of this H&K series, have you try/owned any of them? I have an ATS60 under the radar but this pop up surprisingly cheap so I could not pass on it.

[J M Fahey]

Fully agree with Teemu and add:
1) the problem with that finish is that it's not actual carpet but a very clever and modern one; they paint the amp with glue and then spray it with a special pistol,that blows the pre cut poyester "hairs" which stick to the surface.
The job is incredibly fast and even , no seams by definition.
There's some electrostatic trick to make sure the hairs fly perpendicular to the sticky surface.
Obviously, you can't pull a carpet which never was there.
Problem is that flexible hairs "give" or bend when the sander surface touches them, so you actually have to sand the wood itself (which probably is some kind of chipboard).
2) If it were mine, I would lightly apply a propane torch to bend all hairs into a hard solid mass which becomes "sandable".
But it might be a mess.
Try a small area in the bottom, with a small lighter flame.
If you can sand it out, then recover it (tolex/carpet/jean cloth); surface will be too ugly for lacquering.
3) an option I sometimes use is covering it with some of that stuff normally used in the underside of cars to protect them from small stones, I guess it's Dura-something.
If you apply it with a sponge paint roller or very short hair wool one, that gives it texture similar to Tolex.
Let it dry 1 or 2 days at least, add corner protectors and rubber feet so it never touches a concrete or stone floor, and it will naturally harden with time. In a week it will be real hard.
Something *similar* to these:
http://www.chirienterprise.com/WhataLiner/WhataLiner.html
http://www.duplicolor.com/products/bedArmor/ <-1 quart will be ample


Any paint shop will know what you are talking about.
Use the water based product, which is slow but friendly and does not smell.

[rookie]

Finally I am going to desist, you are right guys, I´ve been cleaning as much as I could with a brush and to refinish it surely won´t worth the effort because I am only use the amp at home. The clean volume pot scratch a little also but there is not a big problem. At home I can really turn volume up a lot so I could live with it.

And any of you guys have the schem of this amp.. I have some kind of curiosity about the design. Maybe someone could send it to me in a private message.

I have an electronics engineering degree and as a hobby I have just started messing around some schemes in NI Multisim, that if you do not are used to, I encourage to use this powerful design tool.

[rookie]

Hi folks!

I am replying this old topic because I am starting to have problems with the amp. I did not used it since last week and when I plugged my strat this afternoon suddenly volume goes down and back up and then no volume. I was playing at bedroom volume is that matters. And this was first at the lead channel, but then at the clean channel too. I turn the amp off, then turn on again and the problem persists. It is like a general volume drop.. but when you push the master up then the volume goes up  and finally goes down again...

If you guys have any idea of what is the cause of this problem it will be very appreciated..

[Roly]

Dirty contact somewhere.  The most common cause are the bypass switch contacts in the Fx Send and Return sockets, then the headphone socket.

Generally clean all your plugs and sockets, starting from the guitar, with a few drops of metho or contact cleaner, and "work" by plugging in/out a few times.  Occasionally they won't clean up and require replacement with new.

Second chance, dirty control pots, ditto.

Third chance, particularly with PCB mounted sockets, is a fractured solder joint where they mount - resolder.

HTH

[rookie]

Dirty contact somewhere.  The most common cause are the bypass switch contacts in the Fx Send and Return sockets, then the headphone socket.

Generally clean all your plugs and sockets, starting from the guitar, with a few drops of metho or contact cleaner, and "work" by plugging in/out a few times.  Occasionally they won't clean up and require replacement with new.

Second chance, dirty control pots, ditto.

Third chance, particularly with PCB mounted sockets, is a fractured solder joint where they mount - resolder.

HTH

Thank you very much Roly!

Today the story was a bit different, I started playing normally without any volume problems, to the point I meant to post here that the problem was solved, but suddenly, after at least 30 min of playing, the volume went out...

So maybe is a matter of overheating??.... I am going to turn on the amp in an hour or two to see if it sounds again...

[rookie]

Now It works.... ??

[Roly]

Intermittent faults are the bane of every techo's life, but while this fault is annoying, at this stage its cause is likely to be very minor, most likely dirt somewhere it shouldn't be, and therefore pretty easily fixable by you.

You need to do some tests to try and determine which part of the amp is causing the problem.

Take a known good lead and plug it into Line Out and Line In.  This will provide an alternate path around these switching contacts.  Give it a thrash.  If the amp still plays up like that then it looks like something else.  You could also try feeding your MP3 player etc., into Line In for a (long) while and see if it still plays up (most if not all the amp controls will be inactive in this mode).  This just exercises the back end of the amp, the power amp and speaker.

You can try playing (guitar or MP3 player) on headphones for a (long) while and see if that makes a difference (this takes the headphone/speaker switch contacts out of circuit).

While it could be due to heating that is pretty unlikely unless something else is wrong to cause it, and I think you would be suffering more problems than just a change in level if that were the case.

Are the volume and gain controls nice and smooth in their action, or scratchy?

This may sound like a silly question, but does thumping the top of the case make any difference to the fault; come, go, or make nasty noises?

Do these tests and report your results.

[rookie]

Thank you very much one more time!!

I took a lead and plugged it into the Line In and Line Out and all seemed to be ok, but when I took it off the Line In then the sound went intermitent and scratchy for a while. Then no sound. Plugged again, all ok, took off again and the intermittency. So it seems to be there, into the Line In connector.

I also knocked near the Line In connector while it was sounding (with the cable removed) and seemed to afect the intermittency but it was very subtle.

Besides of that, the clean volume pot, the lead gain pot and the general master pot feel loose, and the clean volume is also scratchy.

[Roly]

Classic.   :dbtu:

Okay, it's an old amp and it's got a few dirt problems (which doesn't surprise me given the way the outside of the sockets look).

Get some fresh (dry) metho, isopropyl, or other alcohol, or specific contact cleaner (make sure it is actually contact cleaner and not just any old "CRC" can) .

Unplug the amp and remove the chassis.

If the sockets are the open type they will be really easy to clean (i.e. both Line Out and Line In, 'coz both have switch contacts), if enclosed, give a good drink/squirt and work a plug in and out quite a few times to scrub the contacts.

Pots normally have an opening where the tags go in, sometimes a hole where the motion stop is in the back of the case.  The trick here is to get a sparing amount of cleaner just on the track/wiper.  The shaft boss normally contains some grease and you don't want to mobilise that if you can help it.

While you are there you should do all the pots and sockets, dust everything out with soft brush & vac.  If the pots are fully sealed with plastic covers you have a bit of a problem because these are not intended to be cleaned but replaced, but we'll cross that bridge if/when we come to it.

Let's see how you go up to that point and post pix of what you find inside.

[rookie]

Thank you very much!! You have been very helpful. Due to work, I do not think I will have spare time in the next few weeks but then I promise I will document all of the process. Bye!!