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Post subject: Re: Mustang GT 40 Sound Cuts Out
Posted: Wed Apr 03, 2019 12:45 pm
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Aspiring Musician
Aspiring Musician

Joined: Tue Feb 10, 2009 7:53 pm
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Hmmm, well i still don't like that but it is reassuring if that's the case. Never the less i'd replace it next time i'm in it if i happen to have a better quality replacement. Only thing is, the traces and pads these cheap boards like the small board the jack is on are so fragile you could be left with a less reliable input by replacing it because the heat no matter how well you do it may loosen the pad. Best thing would be a quality jack hardwired with the proper resistor(s) (think there were a few surface mounts on there) tho can't see the circuit paths or values on the board and no schematic so i didn't bother while i was in there. I wish they had a schematic for these. I know they did for the old mustang.


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Post subject: Re: Mustang GT 40 Sound Cuts Out
Posted: Tue Apr 09, 2019 10:04 am
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Aspiring Musician
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Joined: Tue Feb 10, 2009 7:53 pm
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Well, it happened again. Turned the amp on and footswitch was frozen. Turned it of and back on 5 times and same thing. Then the 6th time after i turned it off i picked it up and let it drop to the ground a couple times from maybe 8-10" and when i turned it back on it was fine. if thats not an indication it's a bad connection i dunno what is. I may solder some wires from the trace destinations on each side of the connector and see if that does it. If not it would be a different connector or even solder joint. Modern electronic design/construction is just garbage. Tired of dealing with cost cutting designs.


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Post subject: Re: Mustang GT 40 Sound Cuts Out
Posted: Wed Apr 10, 2019 8:12 am
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Aspiring Musician
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Joined: Tue Feb 10, 2009 7:53 pm
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Ok, i now have what IMO is undeniable proof it's a connection issue. The above post seems to strongly suggest it as did cleaning of the contacts. Today however i have proof positive as far as i am concerned. This amp has had problems with the footswitch freezing up since i got it the day they debuted in guitar center. What, 2 years? Anyways, of the uncountable times the FS has frozen not one time did it ever correct itself without turning the amp off and back on. Never. Not by jolting the footswitch or plugging and unplugging it, deoxit on the plugs and jacks....nothing. Only rebooting the amp ever did it. But as i said above, the other day it wasn't even correcting itself by rebooting 5 times in a row till i turned it off and dropped the am a few times from about 8 or 10" onto the floor to jolt whatever connection might be causing it and when i turned it back on after that it worked.

Anyways, today it froze again but this time it hit me to jolt the amp while the switch was frozen WITHOUT rebooting it. That i felt would eliminate any chance it was the rebooting that was all or partially responsive for correcting itself. Sure enough, without rebooting i just picked it up and dropped it a couple times and the problem corrected itself ! Proof positive far as i am concerned that it's a problem with a connection, likely a connector tho a bad solder joint is a possibility but i feel highly unlikely for a few reasons. Anyways, i'm going to open it back up and take a good hard look at whether it will be less than a torture fest to hardwire all pin connected path ways in the amp. Certainly the pins on the footwitch board (in the amp, not the board in the FW itself) if not all connectors.


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Post subject: Re: Mustang GT 40 Sound Cuts Out
Posted: Wed Apr 10, 2019 3:42 pm
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Aspiring Musician
Aspiring Musician

Joined: Tue Feb 10, 2009 7:53 pm
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Well, soon i will know if the FS board 18 pin connector is the issue. I hardwired the pathways, all 18 of them. It should never freeze again if that was the issue. If not, back to the drawing board.


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Post subject: Re: Mustang GT 40 Sound Cuts Out
Posted: Mon Apr 15, 2019 11:38 am
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Hey Aspiring, I have exactly the same issue as you posted on 12th Jan, 2018 with the volume dropping to about 50%, then back to full as a chord or note is held. After a lot of messing about, it seems to be a connection problem in the headphone socket- stuff a 3.5mm (⅛ inch) jack in the headphone socket, then remove and it seems to cure.
Not sure if it's that simple, but works for me. Only figured this out today, so will have to see how it goes over the next week or so...


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Post subject: Re: Mustang GT 40 Sound Cuts Out
Posted: Thu Apr 18, 2019 2:07 am
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Joined: Mon Apr 15, 2019 7:44 am
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Hi folks,
I have the same issue with the sound dropping to about 50% volume, then increasing as a chord is held. Amp is about 6 weeks old, did firmware updates as soon as a received it. Sound drop started about 3 weeks in. It can be cured (for me at least) by plugging in 3.5mm (⅛ ") plug or headphones into the headphone socket, then removing. When you plug in headphones, the signal to the speakers is broken and diverted via some of attenuation into the headphone lead, so could be just the cheap plastic headphone jack contacts not holding fast. Would be interesting to know if anyone else can reproduce the same result...


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Post subject: Re: Mustang GT 40 Sound Cuts Out
Posted: Sun Apr 21, 2019 9:29 pm
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Aspiring Musician
Aspiring Musician

Joined: Tue Feb 10, 2009 7:53 pm
Posts: 972
Good call ! That could very well be the issue for some with the volume problem. Switching jacks are always doing that. Just look at the ever so common effects loop issue that causes the exact same problem and also due to switching jacks who's contacts become dirty/ozodized and then become intermittant. You may very well be onto something, and if so deoxit should be used to remedy it more permanently than reseating the contact via a plug. I had the volume issue too but on mine it was one of the internal connectors, as was my footswitch freezing issue, Reseating them and using deoxit cured my volume issue which has not come back now for months.The FS issue stopped after the same for days but then came back. As i mentioned above i did a hardware fix to the offending connector and it has not done it since. Crazy, but with modern electronics probably 90% of problems turn out to be connector issues due to poor quality connectors and jacks.


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Post subject: Re: Mustang GT 40 Sound Cuts Out
Posted: Mon Apr 22, 2019 4:05 am
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Hmm, might have to do a 180 on that theory, as the volume drop is also present when piping the signal into my MacBook Pro via the USB lead. This signal is going to be a digital one before the pre-amp stage, so the switching headphone jack is much further down the line. Could always solder the 'switching' pins from the jack together to prove 100%. Bit drastic for an amp that's only 4 weeks old!
Plugged my Gretsch 2655 in this morning and the issue started within a minute or so. Reseated the headphone jack, and the problem stopped for a short time before starting again. Swapped guitars for my Ibanez JSA5 acoustic, and no problems at all. Back to the Gretsch, and still no issue!! Arrrggghhh, son of a...
Next thought is that a bad connection in the switching jack (hence no or reduced currant to the speakers) could be seen by the power supply. If said power supply is of the switched mode variety, then it may well be reducing it's output in this state. If the CPU part of the amp is on a separate rail, then it would keep working.
Anyway, just chucking some ideas around, need an electronics guru to tell us what's really going on inside these cheap boxes ;-)


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Post subject: Re: Mustang GT 40 Sound Cuts Out
Posted: Mon Apr 22, 2019 7:15 am
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Aspiring Musician
Aspiring Musician

Joined: Tue Feb 10, 2009 7:53 pm
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I wouldn't write it off just yet. Without a schematic you just can't be sure of anything. One thing i notice pretty regularly is at times the amp's volume seems quite low for the setting i typically use at home. I plug in with the volume at 10 o'clock and I could swear it's much lower than usual. I always write it off as my ears or whatever it is that makes all gear sound different at times. But this volume difference just seems to be too much to be that. I always spray deoxit in the send and return jacks so i know those are clean and making good contact. So last nite i sprayed the phones jack and slammed it a bunch of times with a plug. We shall see if that possible issue remains or not after a time.


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Post subject: Re: Mustang GT 40 Sound Cuts Out
Posted: Mon Apr 22, 2019 9:14 am
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I hope that Deoxit stuff evaporates, other wise your reduced volume might be due to the amount of liquid sloshing about in your cabinet!! :lol:


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Post subject: Re: Mustang GT 40 Sound Cuts Out
Posted: Mon Apr 22, 2019 9:32 am
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Aspiring Musician
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Joined: Tue Feb 10, 2009 7:53 pm
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No, its non conductive. You can spray it right on a power supply and soak it with the amp on and it does nothing. It does dry quickly too.


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Post subject: Re: Mustang GT 40 Sound Cuts Out
Posted: Tue Apr 23, 2019 5:48 am
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Professional Musician
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Location: ʞɹo⅄ ʍǝN
Yeah Deoxit is designed for electronics use. It won't cause damage. Fantastic stuff.


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Post subject: Re: Mustang GT 40 Sound Cuts Out
Posted: Tue Apr 23, 2019 6:05 am
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Really shouldn't need it on any bit of kit that's only a few weeks old though!


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Post subject: Re: Mustang GT 40 Sound Cuts Out
Posted: Tue Apr 23, 2019 7:08 am
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Aspiring Musician
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Joined: Tue Feb 10, 2009 7:53 pm
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You shouldn't but having worked in a repair shop for years i have seen it over and over even with essentially new gear. Name your reason...cheap connectors, contaminated connectors that have been on the shelf for a year, etc etc. In any case its common no matter the age. Mine is a couple years old but it started with some of these issues within the first year. You might say i was lucky. :mrgreen:


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Post subject: Re: Mustang GT 40 Sound Cuts Out
Posted: Tue Apr 23, 2019 9:05 am
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Professional Musician
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Joined: Thu Aug 07, 2014 3:25 pm
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Without a schematic, I'm kinda flying blind here, But...
Most digital amps I have examined do not use conventional jack switching of the signal. They use a single switch in the HP jack to generate two different signals.
One is a HP detect that instructs the CPU to go full stereo and lower the gain so you don't blow your ears out.
The other signal is a HP mute that turns off the speaker.
If there is a connector on the HP circuit, solder its wires in.


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