TM20 loose knobs

Hi,

I have an issue with all my gain and master knobs with my TM20 : they went off ! Today when I wanted to change the gain I've felt that it was moving strangely and I've witnessed the problem.





So, the main issue is that there's no clip inside to set them back properly. If I put them back, it can turns endlessly without turning the rod behind properly. The only thing I see right now is to use glue but it will be tricky to do it in the right position.

Does anyone ever encountered this issue ? My amp isn't under warranty anymore. It's weird that it came so suddenly, with 4 knobs - the eq knobs are fine.

Sorry to have missed this Sushi_Overdose.  I've been pretty ill recently and a few things have slipped by me.

I can't even think why you would have 4 go at the same time.  It's odd but I would consider simply gluing them back on.  First take them off the pot shaft as you don't want the whole thing setting as one.  Check that there is nothing to require you to refit them in one particular position, an alignment flat on the shaft for example.  If there is you will have to set the pot shaft back to '0' then mark on the grey base where the 'dimple' in the silver cover should sit.  You should be able to refit the silver cover making sure to align it to that exact position as you slip it on and leave it to set.  You could use a hot glue gun, (my choice as a touch can also be added behind the grey base to help keep the silver cover in place), or simply a couple of drops of cyanoacrylate 'superglue'.  It may help to scratch the surfaces which will carry the glue or file a few small grooves both along the length and part way around them to give them a bit of a key.  If you were worried about how it would look I would do just one and see how it comes out.  If that one sets firmly and accurately then you can do the others to match.

Other than that, the best I can do is to suggest you get in touch with H&K and see if they will supply you with replacements.  The documentation for both the GM36H and the TM18H shows these parts as "Part number: 9660114;  knurled cylinder knob Chrome TM Series".  They should be universal to all TM and GM amps.  The best way to get them is via their official Faecesbook page.  They usually respond to that much quicker than to email.  The support staff spend a fair bit of time on the road at trade fairs and such like and they say the social media route is easier to deal with while you are in transit.

I have come across similar looking knobs while skimming for bits in the past, there are plenty on fleabay under "guitar knob silver".   They seem to be based on Telecaster style replacements but look remarkably like the H&K ones.  They all seem to be without the marker dimple however.  A tiny dab of nail varnish could help with that!  There is no guarantee that they are identical but, if you find some others you prefer, don't rule out replacing all of them for a new type as you only need 7 of them.  I would really expect that the fitting will be standard on the pots.  Hope this helps.

Hi Bordonbert,

I hope you are doing better.

Thanks for your answer. Well I got in touch with the support too, and their answer is pretty much the same : use glue. But I don't know how I will be able to set them exactly the way they were. I mean there's no point of reference. I guess I'll have to deal with approximate settings then, since buying new knobs won't solve that issue.

Just turn all of the knobs down fully on the amp until they won't go any further and use a knob next to one of your problem ones as a reference. Place a dot on the grey face with a marker pen where the indicator "dimple" should go. That should be pretty accurate if you have a good eye. Then pull the grey body squarely off the pot shaft and extend the mark squarely down the side and under the end so you can see it when the silver cover is in place.

Put a small mark on the inner back edge of the silver cover in line with its dimple so it can be seen from behind but is not visible with the knob in place. You can use the knurled pattern on the edge as a guide to keep yourself square as you do that. You should be able to do all of that fairly accurately and you will then be able to line up the dimple pretty well by eye using the marks you made which you can now see next to each other at the back of the knob. I suspect looking at the slot in the pot shaft in your picture that, when you remove one, you will find that they are the "knurled" type which can be fitted back rotated to pretty much any position anyway. Even if they aren't that method should be enough to get it pretty much the same as the others.

I think it won't be as difficult as you are worrying it will be to get to be accurate enough. A little variation in the '0' position will not be noticeable in use. You're going to have to just give it a go one at a time to see.

So, a quick update : H&K was kind enough to send me new knobs, so I didn't have to use glue with the older one.

Since the EQ part was fine, I used paper and a pencil to get marks to set up the new one. It's pretty accurate except the master for the clean channel but that's fine - and when the new knobs are set in, it seems really hard to pull them off so it will stay this way.

Excellent news Sushi_Overdose. It's good to hear that H&K still have decent support, spread the word. It may have taken a while but that really is the best result you could have hoped for. Did the new knobs come with their inside edges grooved to fit the pot spindles or were they smooth meaning you would have to push them on hard enough to create the grooves?

I had mine come loose and I just used some super glue if I recall, and even if they don't wind up in the right spot you can pull the knob off once it is dry and reposition them.

Sushi_Overdose wrote:So, a quick update : H&K was kind enough to send me new knobs, so I didn't have to use glue with the older one.

Since the EQ part was fine, I used paper and a pencil to get marks to set up the new one. It's pretty accurate except the master for the clean channel but that's fine - and when the new knobs are set in, it seems really hard to pull them off so it will stay this way.

I don't have one of these but it might work for pulling knobs on amps as well.
https://www.amazon.com/Bigrock-Engineering-LT-1401-023-Knob-Puller/dp/B00CRQWMYM

I instead have a Schatten Knob and Bushing puller and it works well and I used it to pull my Floyd Rose bridges inserts that the studs screw into. Multi-use

https://www.stewmac.com/luthier-tools-and-supplies/tools-by-job/tools-for-maintenance/schatten-knob-and-bushing-puller

bordonbert wrote:Excellent news Sushi_Overdose.     It's good to hear that H&K still have decent support, spread the word.  It may have taken a while but that really is the best result you could have hoped for.  Did the new knobs come with their inside edges grooved to fit the pot spindles or were they smooth meaning you would have to push them on hard enough to create the grooves?

They are exactly the same, with the edges grooved for the white plastic part.


Thanks for the tip damnedinblack but I will leave the master this way. My main concern was about the gain since it's the main thing I'm changing when I switch guitars. If I have to play with another unit outside of my house, I know exactly where's my spot with that.