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    GMD 40 malfunctions?

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    3lps

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    GMD 40 malfunctions?

    Post by 3lps on Sun Mar 26, 2017 9:54 am

    Power soak settings malfunction. I recently played my first gig with my 2-week-old GMD 40. About 2 hours into the gig I turned down my volume knob on the guitar and hung it on a stand. The amp was not on standby. 30 seconds later the amp made some loud cracking noise that clipped the main PA speakers. (Mic'd TM112 cabinet, redbox not used and in the off position.) I then put the amp into standby mode. After a few seconds I could not get any sound out of it at that point after I returned the amp to play mode. I looked at the back of the amp and the power soak had changed itself to silent mode from 20w mode and after trying all the different settings I could not get it out of silent mode. I powered the amp down for about 2-3 min in hopes that it would reboot. I was able to get it back on and working but this problem repeated itself 2 more times before the end of the show. I read in the manual that if the speaker is unplugged the power soak will automatically go to silent mode. The speaker was not unplugged but I'm wondering if the cable failed and created an open circuit if that would cause the setting to change to 'silent' also. I used this amp for rehearsals for up to 2-1/2 hours at a time without any problems.
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    aenima

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    Re: GMD 40 malfunctions?

    Post by aenima on Sun Mar 26, 2017 3:45 pm

    you should contact the h&k support, they might be able to help you.
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    3lps

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    Re: GMD 40 malfunctions?

    Post by 3lps on Sun Mar 26, 2017 4:17 pm

    Thanks, I've been to their website to send a description of my problem to tech support but haven't been able to get the message sent. I seem to be experiencing problems with the website but will try again. I also wonder if it could be a tube issue. Thanks for the response.
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    aenima

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    Re: GMD 40 malfunctions?

    Post by aenima on Sun Mar 26, 2017 5:07 pm

    Did you use the same cabinet-cable as in your rehearsals?
    Did you have a look on the TSC lamps when the problem occured? They're supposed to give some info, if the poweramp-tubes have problems.
    If it would have something to do with your preamp-tubes then the amp would not switch into the mute or 0w mode.
    Have you checked the cabinet is 8ohms or more?

    you might try this mail adress: service(at)musicandsales.com
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    3lps

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    Re: GMD 40 malfunctions?

    Post by 3lps on Sun Mar 26, 2017 5:14 pm

    I did use the same speaker cable that was used at rehearsals. The cabinet is a Hughes and Kettner TM 112. All the red lights were on when the amp switched itself to the 'silent' mode. I bought a brand new speaker cable today and am going to do some checking this afternoon. Thanks for the email address.
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    aenima

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    Re: GMD 40 malfunctions?

    Post by aenima on Sun Mar 26, 2017 5:24 pm

    ok, good luck! make sure to check the control lights while the amp is running (not standby).
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    3lps

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    Re: GMD 40 malfunctions?

    Post by 3lps on Sun Mar 26, 2017 5:53 pm

    I just experimented with a speaker cable and discovered that as soon as the 1/4" end is inserted into the speaker output jack on the amp that the power soak switches back to the designated setting from the 'silent' setting. I did this with no speaker connected but in the standby mode. It would seem that the switching is controlled by metal-to-metal electrical contact between the insertion of the 1/4" plug and the jack on the amp, rather than detecting the resistance of a speaker load. Thinking back to the gig, I'm not sure which red lights were on during the time of the problem as I was a bit panicked trying to get things figured out in the middle of performance. In standby mode, all the red lights are on regardless of whether the speaker cable is plugged in or not but in play mode (today, with the cable plugged in) only 2 lights are lit in the 20w setting and no lights are lit in the 40w setting. It almost seems that it could be a problem with the output jack or its wiring. Thanks
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    j200george

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    Re: GMD 40 malfunctions?

    Post by j200george on Mon Mar 27, 2017 4:36 am

    Are you using anything Midi? It seems to have disappeared since using Fredos editor (bizarrely) but i was getting the gm40 going into power soak mute when the FIRST PC command was received at the amp.

    (seems to be unable to replicate it now for some unknown reason).
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    3lps

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    Re: GMD 40 malfunctions?

    Post by 3lps on Mon Mar 27, 2017 7:07 am

    I am using MIDI but only the H&K 432 MKIII controller. I disconnected it but it made no difference.
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    j200george

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    Re: GMD 40 malfunctions?

    Post by j200george on Mon Mar 27, 2017 7:15 am

    Not sure if that sends PC commands it sounds like your issue is unrelated to the other power soak mute "bug"/"feature".... unless of course you had just selected a patch via the 432 and it caused the change?
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    3lps

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    Re: GMD 40 malfunctions?

    Post by 3lps on Mon Mar 27, 2017 8:01 am

    No patch change command was entered. The guitar volume mode was turned all the way down with the guitar hanging on a stand, amp was in 'play' mode rather than 'standby'. Thanks
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    bordonbert

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    Re: GMD 40 malfunctions?

    Post by bordonbert on Mon Mar 27, 2017 8:15 am

    Couple of points from the GM36 side which will probably be the same for the GM40.

    You are right of course, the amp automatically sets itself into protective mode when there is no speaker inserted:
    H&K GM36 Manual wrote:Note that if you choose to mute the amp, you do not need to connect a speaker. Designed to enable silent recording, this option provides the full signal to the Red Box output. To protect the power amp, GrandMeister 36 automatically engages this mute circuit as soon as the plug is pulled from the Speaker Out port.

    The speaker sensing is done via the switched ground on the speaker socket.  When the plug is inserted it opens the switch which allows a voltage to rise above ground and this is detected by the safety circuitry.  I think you are right 3lps when you say it may be that if your cable bums out it will not be detected as the plug is still inserted!  There seems to be nothing there that detects the impedance of a speaker and you will note that in the quote from the manual above it does specifically say "...plug is pulled from the Speaker Out port".  However, the TSC tube safety control is constantly monitoring the cathode current and it may be that that also prevents very high currents going through the output valves.  Without knowing how that has been programmed it is impossible to say.  I also believe that when in silent mode it has not disconnected anything to the output stages and Tx, they remain working fully.  The full output from the Tx is just switched off the speaker socket and across the power soak resistors which act as the complete load.  The Redbox is taken from the Tx output so it can remain working based on the true output signal.

    One other interesting thing is that H&K have addressed the incorrect Standby approach used by almost all valve amp manufacturers.  Just removing the anode HT voltage from the output valves while they are still in a heated state actually gradually kills your output valves!  It does no harm in leaving the amp switched on with the volume fully down, that will not "wear out" your valves.  H&K controil the current through the valves via the TSC cathode circuitry leaving the HT applied.

    I have known strange "states" to occur in my own TM36 and GM36 amps when they were young.  They can be scary at the time but the protection circuitry in the amp does a pretty good job of preventing serious damage.  If your amp is back to working condition I would just make sure your speaker cable is a sensibly decent one with larger plugs specifically designed for speaker use with heavy cables, and with the internal contacts sleeved to keep them from shorting if it gets tugged (which it will).  Have a look at NEUTRIK NYS225 JUMBO 6.35MM JACK PLUG which are a good type to see what I mean, but there are other makes like them.  You don't need gold contacts in a guitar speaker plug either, the high currents continually "whet" the contacts and keep them conducting.  And any heavy gauge cable will do just as well!  I always use just a heavy mains cable type.  Please don't be conned into going for something "plaited by elves with asteroid sourced oxygen free copper blessed by Mongolian monks", it makes absolutely no audible difference whatsoever in our application.
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    aenima

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    Re: GMD 40 malfunctions?

    Post by aenima on Mon Mar 27, 2017 1:03 pm

    i want that plaited-by-elves cable though Wink

    @george: i think the problem with the first pc sent is only present, when you dont have the app connected and you use a floor board only.
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    3lps

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    Re: GMD 40 malfunctions?

    Post by 3lps on Mon Mar 27, 2017 1:35 pm

    Thanks bordonbert for you valuable input. I appreciate your response. I do have a decent speaker cable and have ordered a complete set of tubes in hopes of correcting my issues. I really like this amp and don't want to give up or say anything negative about it. It's not a perfect world but I am confident that I will get this condition corrected and have confidence that H&K / Sweetwater sound will take good care of the situation if I can't find the problem.
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    bordonbert

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    Re: GMD 40 malfunctions?

    Post by bordonbert on Tue Mar 28, 2017 4:14 am

    Aenima wrote:i want that plaited-by-elves cable though Wink
    Hahaha! I would have guessed that Aenima! Wink I should have been an advertising copywriter instead of an engineer, I could have made a fortune. Crying or Very sad
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    bordonbert

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    Re: GMD 40 malfunctions?

    Post by bordonbert on Tue Mar 28, 2017 5:55 pm

    As an addendum here, if you want to get H&K support it is often better to post a query on their Facebook page than to email them. The FB page is much more public and gets a pretty quick and reliable response. They often seem to let the emails slide if there is something important going on which demands their time. The guy who looks after the FB page is really helpful where he can be.
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    3lps

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    Re: GMD 40 malfunctions?

    Post by 3lps on Tue Mar 28, 2017 9:13 pm

    Thanks to everyone for your insight and suggestions. I called Sweetwater Sound in Fort Wayne, Indiana, USA, Monday morning and explained my problem and answered some questions they had for me. Within several minutes they concluded that the amp would need to be returned and that a replacement would be sent out. I received the replacement today. I couldn't ask for better service attention than that. I also ordered a full set of new tubes because I've read many comments from people who have replaced the stock tubes upon buying this amp. I won't install the new tubes right away but wanted to have them on hand in case I have a problem. I am very pleased with the response I've received from everyone and appreciate the insight. I am also very pleased with the way the music dealer helped me through this. Thank you to everyone and I will revisit this post if I experience any more problems.
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    j200george

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    Re: GMD 40 malfunctions?

    Post by j200george on Tue Mar 28, 2017 10:19 pm

    Great service and good to hear. I have to say although I too had great service from thomann who swapped out mine without hesitation. The first gm40 I had unfortunately arrived with its heat shield detached.

    I cant be sure of I experienced the power soak mute issue with the first head because at the time the amp was just so different and there was a lot to get my head around in terms of the way I interacted with it compared to my mesa lss.

    It may have happened I just didn't put it down to a pc command triggering it. Please let us know if it still happens.

    H&k asked for my serial number and I await their response. My guess is I too will need to send it l but do you know what? Since using fredos control app, and this makes no sense at all I know... what was a solid repeatable fault has been absent regardless of whether the amp has the iPad connected or not. For clarity, I've only used the desktop app one time and it's not been connected since.

    I am trying to blast it nightly after work much to my long suffering wife's chagrin.

    Will keep you all informed also.
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    j200george

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    Re: GMD 40 malfunctions?

    Post by j200george on Wed Mar 29, 2017 7:04 am

    **update, H&K say that mine is an early serial number and are suggesting a swap out. I have contacted Thomann via email again and will see if they support a swap out, it is beyond thirty days from purchase so not quite sure what they will say.....
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    3lps

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    Re: GMD 40 malfunctions?

    Post by 3lps on Wed Mar 29, 2017 8:02 am

    Thanks j200george for the update. I'm impressed with the fact that these music stores and H&K are really concerned with taking care of these issues. What a pleasant surprise.
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    aenima

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    Re: GMD 40 malfunctions?

    Post by aenima on Wed Mar 29, 2017 11:57 am

    I have to say, my unit seems to be messed up. I dont know but presets are not recalled correctly. the app may show the correct values but not the amp. The amp is in crunch and boost or ultra and boost activated most of the time even on presets where clean channel without boost or sth different is programmed. i was totally looking forward to a jam session. the first with this amp and made some presets to test its different channels etc. its not an issue of a midi unit because it happens with windows app, android app and midi floor board alike. I really hope this amp does not turn out to be a non reliable unit, because that would make it useless for everyone planning to gig with it. I do have the old firmware on it and hopefully that's the only cause for this problem. I'll have to contact the support and test the amp first, because that test was the final milestone for me to see if its worth its money and i wont use the 30day money back program. i need a loud clean tone which some (most amps) at this wattage have not been able to deliver to me so far and cant test that at home... I'll let you know how the story continues.
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    j200george

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    Re: GMD 40 malfunctions?

    Post by j200george on Wed Mar 29, 2017 12:24 pm

    If you select say global mute on the iPad app is the amp muting? Or if you change channels on the app does the amplifier change channel?

    I take it you have the fs432 connected to the amp via the wmi-1 midi in port and the wmi connected to the amps mini in and out correctly? They don't need fully pushed in?

    Sorry if the above is a bit patronising I'm only trying to help. Hope you get it sorted soon mate.
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    aenima

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    Re: GMD 40 malfunctions?

    Post by aenima on Wed Mar 29, 2017 12:27 pm

    who are you adressing? if youre adressing me: the amp changes presets but does not change channel/boost etc accordingly. gives out the correct values via midi out but does not load them itself. i use a behringer fcb1010 via midi in and the apps with midi in /out.
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    j200george

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    Re: GMD 40 malfunctions?

    Post by j200george on Wed Mar 29, 2017 12:31 pm

    I was addressing you aemina. I'm struggling on the phone wasn't sure how you were accessing mini I must have mixed you up with another poster.

    I'm sure someone more able to assist you logically today will pitch in.
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    3lps

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    Re: GMD 40 malfunctions?

    Post by 3lps on Wed Mar 29, 2017 1:37 pm

    When mine was acting up the 432 foot switch was not functioning properly either.

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