FSM432 won’t communicate with my GM36

Hello,
Brand new to my GM36 and FSM-432. Having some issues and any help would be greatly appreciated. When I connect the FSM-432 using the included cable (seven pin connection from midi out) to my GM36 (seven pin connection midi in) the head does not supply phantom power to the midi controller as it should. When I connected a external power supply to the FSM-432 it powered up as it should however the midi controller does not control the GM36. You can change patches and banks on the board but they do not change the controls on the amp at all.

I found a post on Reddit where another individual was having the same issues but never mentioned any resolution.

I just purchased both used and I would have to ship everything back to the seller by Monday if I want a refund so any help would be greatly appreciated.

Thanks everyone

*edit*
I also just tried putting the amp into midi setup mode to ensure it was in omni mode and to make sure it was set to midi channel one and that does not seem to be working properly either.

Hi Garono.  Welcome to the forum.  Your description of the amp having problems in MIDI Setup Mode does seem to suggest the problem is probably with the amp and not the footswitch unit though that is not for sure of course.  I would start with sorting out some simple things on the amp.

The first thing I would try is to do a factory reset on the amp to cure any software corruption related problems which may have crept in.  Be warned, while this will not make any difference to the performance of the amp if there is no existing problem, it will replace all of the currently programmed patches with the factory defaults.  As you have just bought the amp I would guess this is of no consequence to you but it is best you are aware of it.  You will permanently lose any programmed voices which the amp currently holds.  That is done by pressing "Store" and "FX Access" simultaneously while powering the amp up with the Power/On switch. Both buttons will flash three times to indicate the successful factory reset.  Once that is done you can be sure there is no software corruption to introduce erratic behaviour.

Next I would try to access the MIDI Setup Mode again.  If this is still a problem could you describe exactly what you are seeing.  Does it do absolutely nothing when you hold the Noise Gate and Fx Loop buttons for 3 seconds?  Does it seem to complete with the Noise Gate and Fx Loop buttons flashing and the fx Access button permanently lit up as they should but will not respond to other commands?  What I mean is does it get through any part of the procedure as you would expect it to and at what stage do you see there is a problem?

EDIT: I would also say that another simple test we could run in the meantime is to measure the DC voltage at the footswitch end of the cable. Do you have access to a simple multimeter to do this?

Thanks for your quick reply bordonbert .

I’ve tried the factory reset multiple times. When I hold down the the “store” and “fx access” buttons simultaneously (while powering up the amp) both buttons will light up at which point when I remove my fingers the buttons will flash five times (not three as the manual suggests) and then just the Fx access button remains on.

When I try to put the amp into midi setup mode by putting the amp into standby and pressing the “noise gate” and “FX loop” simultaneously it lights up the “store” and “Fx access” buttons (solid not flashing) instead of the correct buttons flashing (noise gate and fx loop) as the manual indicates. At that point I can use the noise gate and fx loop buttons to change the values of the four channel LED’s however holding noise gate and and fx loop buttons again simultaneously does absolutely nothing as far as indicating a saved command.

I’ve done both countless times and get the same results every time. Unfortunately I bought the units used and am now looking at what I’m guessing will be a heafty fee to ship the unit off to Germany and pay to have it fixed as it isn’t under warranty.

And it was an Christmas gift for my kid to boot, thankfully I decided to try it out before putting it under the tree. *sigh*

Whereabouts in the world are you Garono?

H&K do have a policy of only releasing their service/maintenance info and access to spare boards to recognised workshops. In some countries like the UK they have a service depot which is easy to contact. In larger countries like the US it is more difficult as the distances are greater but I have known local tecxhs be able to fix problems so it may be that with the right request from them it could be set up. In more remote countries it is much more a case of "suck it and see".

Lol well I’m in the US so hopefully it won’t be “suck it and see”. I believe the company’s closed until the new year so I’ll have to wait a while for an answer.

What’s frustrating is that the seller claims the amp and controller were in perfect working order before shipping it but I’m thinking that wasn’t the case as the box it came in was in perfect condition and the equipment was immaculate as if it had never been used. I think this was a factory defect from the start. I have a feeling I just got taken for $700

Hopefully the repair cost won’t be too bad, the amp sounds amazing with what I am able to do with it.

Repairs in the US seem to be organised on a more casual basis due to the size and distances involved.  I'm in the UK so your setup over there is different to my own.  Over here we have a single service agent who all official repairs are sent to.  However, with some of the older models now warranty isn't an issue and local techs are becoming confident with repairing them so we can sometimes take that route if necessary though it isn't the authorised route by H&K.  Your own repairs seem to follow that setup as a matter of course.  If you approach a local well established repair shop they may have a working relationship with H&K already.  It is a good point to note that these amps with their digipots and MIDI control options are very much more complex than the usual "classic" guitar amps.  It is good to find someone who has experience of working on them already.  The fix is usually quicker to find and more reliable afterwards.  You may also get a more sensitive treatment from them, old school amp purists (Luddites?) with their handwired valve exclusive preferences are notoriously snooty about H&K amps.

I wouldn't give up hope of a possible fix yourself though.  I would look into the repair side of things while at the same time keeping a finger on working on it yourself.  Is there any way you can measure that voltage on the pins of the MIDI Out plug at the FSM432 end of the cable when it is plugged into the amp?  That's only the two extreme pins with the gap between them which would carry the DC.  The fact that the FSM432 does not even boot up seems to suggest you may have a power supply problem in there but the rest of the amp working as it should soundwise would seem to rule that out.  I'm assuming the amp does actually work when you play through it, is that correct? (Edit: Just reread your post and this is irrelevant.)

One other things is that you could approach H&K for advice themselves directly.  This is best done on their Facebook page rather than through email which they are slow to respond to.  https://www.facebook.com/hughesandkettner/  Try asking them the same as you have told us here and see if they can offer more info than I can.  They will at least be able to fill you in as to the best repair route in the US.  You could message them in the "About" block on the right but a post in full public gaze may be picked up a little more quickly.

I've just reread your earlier posts and thought of this. You said "When I hold down the the “store” and “fx access” buttons simultaneously (while powering up the amp) both buttons will light up at which point when I remove my fingers the buttons will flash five times (not three as the manual suggests) and then just the Fx access button remains on."

Are you holding down the buttons until the whole process completes and the flashing has stopped or are you releasing them as soon as it starts?

Good question. I’m holding them down until they both light up (but don’t blink) and then removing them at which point they blink five times. I did try continuously holding them down the first time (expecting them to start blinking) but assumed after several minutes that something was amiss. Does it take an extended amount of time for the reset to take? I was holding them for several minutes without them blinking.

*edit*
Just tried it again and held them down for over five minutes and no blinking, going to assume that’s not typical

No, you're right, it shouldn't take anything like that time to respond. It did just occur to me that you may have just released them as soon as you switched the amp on. What you describe certainly doesn't sound normal. This is the first time I've come across this particular type of problem I have to say. It almost seems as though it is something deep within the coding of the processor unit and it is even affecting the reset procedure.

That’s what I figured. I have a bad feeling this will be a costly fix. I guess my only option is to reach out to H&K then. I think they’re closed until after the holidays unfortunately. Thanks again with helping me try and troubleshoot the issue, I appreciate it

Do keep us in the loop with how it goes. You never know when your own problem and its solution are just what someone else is looking for to solve their own situation. In the meantime you never know when someone may pop in here who can offer you something I can't see. You may even need someone to translate what H&K might give you and make it clear.

I can't help thinking that there is something simple we are missing here. This doesn't seem to have the characteristics of a hardware problem at all and the idea of a non-working reset has never come up as far as I can remember. I'll keep thinking and see if there isn't something more I can advise.

Thanks! I’ll update this thread as I have information. And like you said maybe someone else will have some input about my issue in the meantime.

Hi Garono,

Have you tried it with another 7 pin midi cable?
I have had a faulty cable myself with my GM36. It is also possible that the socket on the foot switch could be damaged. I think that it would have been a better design if H&K had placed a protective cap over the area where the sockets are situated or to recess them deeper into the casing to prevent possible stepping on them.

Maybe you could also take the GM36 to a music store where they sell them and hopefully try it out with an alternative foot switch and cable.

Kind regards and good luck.

Martin

My apologies for the thread necromancy, but I am having the exact same issue described Garono. That includes getting 5 blinks instead of 3 when I reset to factory defaults. What was the solution that ended up working? My FSM 432 MK III powers on (only with an external power source) but doesn't actually control my GM36 at all.

Barondeblot is spot on with his advice.  I have found that MIDI cables seem to be notoriously weak in use.  I have gone through a few in my time.  They don't have any strict technical requirements so tend to be made with cheap cable and cheap connectors.  The cable is a highly possible factor in this.  I didn't mention it specifically which I should have done, thanks to Barondeblot for doing that, but I did suggest measuring the voltage at the end of it which would of course check it out.  So, how do we do that?

There are a lot of problems like this which would respond to a bit of ultra simple self diagnostics.  It's a good thing for any guitarist to have a multimeter in their kit.  These are ridiculously cheap nowadays and will measure voltages both DC and AC, currents, and resistance.  Some even give an indication of capacitance too and test semiconductors.  I'm looking at some on ebay for around £5 brand new.  You only have to be careful to select the range that is correct for what you are going to measure before you connect up.  It also pays to start with higher value ranges in the correct sector and click down until it reads the value.  This protects the meter from potentially damaging overvoltages.  If you can get your hands on a meter then measuring the voltage on the FSM432 end of the cable takes seconds.

Looking into the GM36 FSM432 MIDI In socket and imagining it upside down with the locating notch at the bottom and the pins at the top, (N.B. this is for a socket and not a plug which will have its pins reversed to fit in), you should find +22V on pin 6 with reference to 0V (ground) on pin 7.  These should be the end ones on the left and right sides with the gap between them.  It makes sense to put the cable in their and do the measurement on the plug for the FSM432 at the other end.  Looking into that you should find +22V on the outermost right pin and 0V on the outermost left.  This will have been reversed to match the plug to the socket when it is inserted.

A quick bit of general info here.  DIN sockets do not number their pins around the circle.  I have seen pictures online showing just that and it is wrong!  With the pins at the top they start with a basic 3 pin type, 1 left, 2 top and 3 right.  This is what you need to construct the simplest 3 pin version.  They then add in the diagonals between these with 4 left and 5 right to create the 5 pin variants.  Finally the two lower diagonal pins are added with 6 on the left and 7 on the right.  It's awkward but it is structured and is fairly easy to work out.  The confusion comes when you mix up sockets and plugs as these will have reversed numbering as you look into the open ends of each so they match up when they are mated.  I've attached a picture of the power connections as you would see them on the rear of the amp.

Certainly I would check up on that cable.  It may be the cheapest fix you would ever come across.  It doesn't explain the 5 flashes, though I wonder if that is just a bit of out of date info in the manuals.

Thank you for the tips! I will try out what you've suggested and go from there. I did pick up a new MIDI cable today but I asked an employee to grab me one and they grabbed a 5 pin instead of a 7 and I didn't check it until I got home. I'll get a multimeter and a proper 7 pin cable! My original 7 pin cable does look a little beat up and upon closer inspection I noted one of the pins is askew so it could very well be a cable issue. Thanks again!

Make sure to let us know how you get on with the new cable.

Hey all! Sorry for the delay, I had to special order a replacement cable and it took a while to come in. I am thrilled to report that replacing the cable fixed the problem!! Thank you for the tips!

I did have a problem tracking down the appropriate male-to-male 7-pin MIDI cable because they're apparently not all that common. For those wondering, I purchased a Fender 7-Pin DIN from Long and McQuade which can be found at the following link (but it had to be special ordered):

https://www.long-mcquade.com/118683/Guitars/Parts/Fender-Musical-Instruments/7-Pin-DIN-25-ft-Cable.htm

Excellent to hear it is fixed, and good to find out that it was something as simple as a cable.  As I said before, for some reason MIDI cables always seem to be very lightweight and vulnerable to me.  The best I have ever found are those supplied with my old Vox Valvetronix which use an armoured "locking" type of plug into a recessed and very solid socket on the VC12 foot controller so it is less likely to be damaged by being trodden on near to the footswitch.  But these use RJ45 style computer network cables and not 7pin DIN.  The advantage is that flexible network cable is faster and stronger than the usual 7 wire cable used for MIDI and it comes in tougher military grade.  There is no electrical requirement for a MIDI cable to be of a light construction.  Making one up from heavier cable is a good idea if you have the soldering skills.  Soldering DIN type sockets is not for the inexperienced!

Has this corrected the 5 flashing LED situation too?

Here is a UK version from a decent cable constructor:  7pin DIN Cable