I found one in the trash with a note saying" Turns on but makes a God awful noise;you have been warned!" I figured I could at least use it for parts for my JCM 800. 2 months later I decided to plug it in. When I hit the switch a white noise faded in,and then faded out,and then fading back in with a BLASTING FOG HORN SOUND! Immediately shutting the switch off I took out the head disconnected the speaker and plugged in a pair of headphones;it sounded fine. Looking around I saw a small board behind the input Jack with multiple pins (which turned out to be the effects board), and pulled it out. Spraying both the socket,and pins with Deoxit spray I put it back together and plugged in the speaker,it works fine. About a year later it started again,and I just did the same thing,and once again it works fine. This may work for other effects problems since it was the effects board with a dirty/ intermittent pin. It's worth a try.
Good afternoon Sr. I have a Marshall Mg 100 dfx which digital effects section doesn't work, when you dial the buttons it only makes noises and static. what should I do? Thanks, your video is so educational.
Hello Liam, great video and interesting to watch you having fun and fixing it up. If you can shed some light on my amp please, Marshall solid state MG50DFX: the clean channel lost almost all volume; the overdrive channel has volume but lost gain, can barely hear any crunch even gain turned to max. I have since taken the head unit out, cleaned with electrical contact cleaner while didn’t see any rust or bad joints, which made no improvement. I have tried testing with headphones; connecting the FX send and return; testing with footswitch to switch channel. All same symptoms. I would really appreciate if you can point me out where to look at first that’s mostly likely?
I'd give all you jack connectors a good squirt with contact cleaner and fully remove and insert a jack about 20 times on each one straight after spraying it. I'd start primarily with the guitar in jack. One would guess the problem to lie before the preamp stages as they are both separate but by the sounds of it are getting a low signal level. Also, check your guitar lead and guitar. If you don't have another to try, see what your guitar does plugged into a different amp.
@@killcar5nbike2 Hi Liam you're a STAR! it is y guitar which I added a humbucker previously the control cavity became too cramped. Turn on the "Thanks" let me buy you another drink please!
Hi Liam, as you mentioned the Impedance 16 ohms does this make components suffer if someone uses a 8 ohm cab. I have just bought a second hand 2004 Marshall mg 100HDFX with issues regarding the distortion OD 1 & OD 2channels. Foer some reason after playing on OD 1 And OD 2 thier is a slight tonal drop or gain reduction power drop if that makes any sense. As you also mentioned the chip mounted on a very small heat sink my have nultiple issues noa PCB based cct. I have trouble finding a schematic as it might also indicate the contour control might also have some influence with this unsual fault. I'll hopefully be able to replace caps but we are rated at 240 volt so interesting times to fix this issue. Please note the clean and crunch channel is unaffected with tonal or drive issues. Thank you for sharing your repair and hopefully a nice molt can be found in the Uk regards Big Grunta an amp Tech in Australia.
As far as I can remember the pre amp is pretty much all digital. Any analogue sections should not be affected by the output chip. The change in sound could be the thermal protection in the output chip kicking in. If it's been driven hard it may have issues where it's no longer functioning properly.
Hello man i have the same amp when i turn it in clean sound evrything be ok but when i click on any buttons it turn noisy and buzz can u help me fix this problem ?
It's like a car rev limiter. Will stop you blowing the engine up if you try to rev it past a certain point. Keep driving the thing running flat out and it will die eventually. Only helps to a point.
@@killcar5nbike2 but I've never had one shut down and protect anything. They always blow the fuse and the power amp fries, along with pretty much every other component in the power gain stage. It isn't shutting down until after it has shorted out and done its damage. I would expect it to blow the circuit beforehand at least once in a while.
@@natetolbert3671 the thermal protection on most amp ICs is not a shut down. The output protection circuitry just kicks in earlier. However you can't beat the laws of physics, and it can't protect it with an under sized heatsink.
@@killcar5nbike2 Yea that is why I commented originally. I the case of the 7293, going by the Mouser datasheet, it is a shutoff. In fact, it is one of only a few tda models with this feature. That is why I found it so ironic that this particular amplifier was chosen for the circuit. It is almost as if the engineers knew that the heat drain wasn't enough for the application, but for whatever reason (likely having to do with upper mgmt. / production cost) they coundn't do much to counteract, so they chose a chip that was supposed to offer extra in the way of overheat resistance to try a bit of last minute CYA. However, it obviously didn't work, and theirs were left bare. Behind every lemon circuit design, their is a story identical to this one. Anyway, no more blabbing from me. I am a former elec. engineer who changed careers, and I miss the shop talk. XD Have a good one, and thanks for the great vids.
Great work. I am not so experienced on electronics. I ended up in your video as I was trying to resolve a problem with my Marshall 5205 Reverb 12 that lost almost all its volume, I crank it to the max and you nearly hear it. Both Zener diodes ZD2 and ZD3 seem to have blackened the board where they are attached but they do not show any damage. Do you know where I can find replacement for these? Thanks for the help.
Measure the voltage across them, when zeners go they short internally, but still look fine. Google will tell you what value they should be if you can't read the part number on the body of them. EBay will be fine for something like a zener.
@@killcar5nbike2 thanks for the quick response. I have found on the schematic of the board here (drtube.com/schematics/marshall/5205.gif) that both of them are 15V. However, they are called ZD2 and ZD3+. Do the numbers refer to the positions on the schematic while both of them are the same, or the numbers refer to a specific type of zener diode. What is the plus referring to that is on the board? Apologies, but it is the first time I have to do this job.
@@rodanthosofficial4393 the ZDx is it's place in the circuit. If you change them put them in the same way round as the ones that are in. You can see the coloured band as the Cathode end. But whether they're your problem is another thing altogether. I'd be inclined to try and find a forum where your problem is discussed. Most amps have common issues that have been well documented by now.
@@killcar5nbike2 thanks a lot for the help. I have put the Zener diodes to my Marshall but once I connected it, another component was burned. I am not sure if I put the Zener diodes right. I actually put the anode of the Zener diode towards the positive sign printed on the circuit. Is this right? Thanks in advance for the help.
@@rodanthosofficial4393 I'm afraid without having the thing in front of me any help I can offer is limited. Zener diodes, like all diodes are with silk screen markings will go Cathode on device, to Cathode on silkscreen.
You can tell the Whisky kicked in around 13:35 lol I have an overdrive issue with The Marshall MG10CD It CAN'T BE THE SPEAKER as it is ok in normal mode press the overdrive and its really distorted and crackly sound cuts in and out a little . i can only describe it as dusty contacts sound when turning old amps up etc but it is severe to the point guitar on vol 1 amp on 1 overdrive on 1 and it sounds awefull i looked inside i think the capacitors little brown thingys with little metal ends in rows one end of one looks slightly burned ? would that cause this kind of issue i feel i could replace it with an identical one from another board ? any feed back appreciated
I have one of these, and sometimes, not all the time, I would turn it on and it would make this constant loud ass popping sound. Any idea what's wrong with it? Should I just try to sell it on reverb and state the problem? Should I just throw it away?
@@chrisgoodrich46 if there's a bad connection on a signal level signal it will be amplified. Just do the pots and sockets. It can only help. Unlikely it's on the speaker lead, that would be more of a crackle/intermittent connection
hi,so mine mg100 hcfx...the sound is like "iiiiiiiii........".so.iam mentioned on your comment look likes.its just broke the chip diode and fuze...and replace it?.zero elektronic experince...longstory short..its broken because "maybe" i use for re amping modeling when mixing(its already not work,but before re amping its working well with my input guitar to out the cabinet).after that..my head not working..and justt..."iiiiiiii.......".have any idea...thanks alot.plis reply
@@natetolbert3671 thanks alot.so,keep in mind...how to use reamping with head for mixing? ist direct box or maybe there any specific tool for change the impedancy..iam sorry if my question confusing.once again..thanks for reply
i have had this amp head since 2000 so new.and just as of last week i have no signal no sound at all going the the cabinet it is plugged into.i have changed the chip board years ago the one by the fan in the back. any thoughts?
@@killcar5nbike2 Yeah mine has blown 4 times in 20 years. I eventually just gave up; it now makes an excellent coffee table... In fact, by the last time, most of the solder pads had broken/ worn away. I had to use jumper wires to make it work.
Off the top of my head it was a 12v 1/2 watt. I'd have to watch the video but I'm fairly certain I mention the voltage I used or voltage I measured after replacing it.
@@killcar5nbike2 After I replaced the TDA7293, the fuse still blew, I checked the Diode and it was a shorted, I have a few diodes in my bin but not the 1N5238B. This one is 8.7V 0.5W zener diode, let me know if you find out what is a suitable equivalent diode. thank you.
A more substantial chunk of metal would help. Big heat sink with proper air flow would be a big improvement. As it is if you go no lower than 16 ohm load it should be just fine.
The connections for pedals are make/break. Try some servisol super 10 in the connector, and cycle plugging unplugging a connector in the socket about 50 times. Make sure you come fully out, and go fully in to work all the contacts.
I found one in the trash with a note saying" Turns on but makes a God awful noise;you have been warned!"
I figured I could at least use it for parts for my JCM 800.
2 months later I decided to plug it in.
When I hit the switch a white noise faded in,and then faded out,and then fading back in with a BLASTING FOG HORN SOUND!
Immediately shutting the switch off I took out the head disconnected the speaker and plugged in a pair of headphones;it sounded fine. Looking around I saw a small board behind the input Jack with multiple pins (which turned out to be the
effects board), and pulled it out. Spraying both the socket,and pins with Deoxit spray I put it back together and plugged in the speaker,it works fine.
About a year later it started again,and I just did the same thing,and once again it works fine.
This may work for other effects problems since it was the effects board with a dirty/ intermittent pin.
It's worth a try.
i have this amp and its pretty dope for real.
cool vid … informative. had a few on bench
My son is called Liam and I was born in 1981 😳 I wonder if that brought me here lol great vid though 👍
I have the same problem, amp turns on fan works but no sound .
Had 2 of them and they both burned out. Really unfortunate because i loved how they sounded...
Good afternoon Sr. I have a Marshall Mg 100 dfx which digital effects section doesn't work, when you dial the buttons it only makes noises and static. what should I do? Thanks, your video is so educational.
Hello Liam, great video and interesting to watch you having fun and fixing it up. If you can shed some light on my amp please, Marshall solid state MG50DFX: the clean channel lost almost all volume; the overdrive channel has volume but lost gain, can barely hear any crunch even gain turned to max. I have since taken the head unit out, cleaned with electrical contact cleaner while didn’t see any rust or bad joints, which made no improvement. I have tried testing with headphones; connecting the FX send and return; testing with footswitch to switch channel. All same symptoms. I would really appreciate if you can point me out where to look at first that’s mostly likely?
I'd give all you jack connectors a good squirt with contact cleaner and fully remove and insert a jack about 20 times on each one straight after spraying it. I'd start primarily with the guitar in jack. One would guess the problem to lie before the preamp stages as they are both separate but by the sounds of it are getting a low signal level.
Also, check your guitar lead and guitar. If you don't have another to try, see what your guitar does plugged into a different amp.
@@killcar5nbike2 Hi Liam you're a STAR! it is y guitar which I added a humbucker previously the control cavity became too cramped. Turn on the "Thanks" let me buy you another drink please!
The 5v regs always seem to have long legs on these amps.
Every time I turn it on the fuse instantly blows ??? What’s the problem
Hi Liam, as you mentioned the Impedance 16 ohms does this make components suffer if someone uses a 8 ohm cab. I have just bought a second hand 2004 Marshall mg 100HDFX with issues regarding the distortion OD 1 & OD 2channels. Foer some reason after playing on OD 1 And OD 2 thier is a slight tonal drop or gain reduction power drop if that makes any sense. As you also mentioned the chip mounted on a very small heat sink my have nultiple issues noa PCB based cct. I have trouble finding a schematic as it might also indicate the contour control might also have some influence with this unsual fault. I'll hopefully be able to replace caps but we are rated at 240 volt so interesting times to fix this issue. Please note the clean and crunch channel is unaffected with tonal or drive issues. Thank you for sharing your repair and hopefully a nice molt can be found in the Uk regards Big Grunta an amp Tech in Australia.
As far as I can remember the pre amp is pretty much all digital. Any analogue sections should not be affected by the output chip.
The change in sound could be the thermal protection in the output chip kicking in. If it's been driven hard it may have issues where it's no longer functioning properly.
@@killcar5nbike2 Thanks Liam, I'll replace the bad caps and hopefully I can find the IC Chip . Remount on a larger heat sink.
I have this speaker but when i turn on it make no sound or any electric sound from the speaker. Everything is fine but no sound. What is the problem?
Hi, i have a mg100x which has lost the dfx channel altogether. Reverb randomly works some days and the next day it doesn't. What can I do?
Hello man i have the same amp when i turn it in clean sound evrything be ok but when i click on any buttons it turn noisy and buzz can u help me fix this problem ?
The strange thing is that the TDA7293 has a built-in thermal shutdown circuit!
It's like a car rev limiter. Will stop you blowing the engine up if you try to rev it past a certain point. Keep driving the thing running flat out and it will die eventually. Only helps to a point.
@@killcar5nbike2 but I've never had one shut down and protect anything. They always blow the fuse and the power amp fries, along with pretty much every other component in the power gain stage. It isn't shutting down until after it has shorted out and done its damage. I would expect it to blow the circuit beforehand at least once in a while.
@@natetolbert3671 the thermal protection on most amp ICs is not a shut down. The output protection circuitry just kicks in earlier. However you can't beat the laws of physics, and it can't protect it with an under sized heatsink.
@@killcar5nbike2 Yea that is why I commented originally. I the case of the 7293, going by the Mouser datasheet, it is a shutoff. In fact, it is one of only a few tda models with this feature. That is why I found it so ironic that this particular amplifier was chosen for the circuit. It is almost as if the engineers knew that the heat drain wasn't enough for the application, but for whatever reason (likely having to do with upper mgmt. / production cost) they coundn't do much to counteract, so they chose a chip that was supposed to offer extra in the way of overheat resistance to try a bit of last minute CYA. However, it obviously didn't work, and theirs were left bare. Behind every lemon circuit design, their is a story identical to this one.
Anyway, no more blabbing from me. I am a former elec. engineer who changed careers, and I miss the shop talk. XD
Have a good one, and thanks for the great vids.
Great work. I am not so experienced on electronics. I ended up in your video as I was trying to resolve a problem with my Marshall 5205 Reverb 12 that lost almost all its volume, I crank it to the max and you nearly hear it. Both Zener diodes ZD2 and ZD3 seem to have blackened the board where they are attached but they do not show any damage. Do you know where I can find replacement for these? Thanks for the help.
Measure the voltage across them, when zeners go they short internally, but still look fine.
Google will tell you what value they should be if you can't read the part number on the body of them. EBay will be fine for something like a zener.
@@killcar5nbike2 thanks for the quick response. I have found on the schematic of the board here (drtube.com/schematics/marshall/5205.gif) that both of them are 15V. However, they are called ZD2 and ZD3+. Do the numbers refer to the positions on the schematic while both of them are the same, or the numbers refer to a specific type of zener diode. What is the plus referring to that is on the board? Apologies, but it is the first time I have to do this job.
@@rodanthosofficial4393 the ZDx is it's place in the circuit. If you change them put them in the same way round as the ones that are in. You can see the coloured band as the Cathode end.
But whether they're your problem is another thing altogether.
I'd be inclined to try and find a forum where your problem is discussed. Most amps have common issues that have been well documented by now.
@@killcar5nbike2 thanks a lot for the help. I have put the Zener diodes to my Marshall but once I connected it, another component was burned. I am not sure if I put the Zener diodes right. I actually put the anode of the Zener diode towards the positive sign printed on the circuit. Is this right? Thanks in advance for the help.
@@rodanthosofficial4393
I'm afraid without having the thing in front of me any help I can offer is limited. Zener diodes, like all diodes are with silk screen markings will go Cathode on device, to Cathode on silkscreen.
You can tell the Whisky kicked in around 13:35 lol
I have an overdrive issue with The Marshall MG10CD It CAN'T BE THE SPEAKER as it is ok in normal mode press the overdrive and its really distorted and crackly sound cuts in and out a little . i can only describe it as dusty contacts sound when turning old amps up etc but it is severe to the point guitar on vol 1 amp on 1 overdrive on 1 and it sounds awefull i looked inside i think the capacitors little brown thingys with little metal ends in rows one end of one looks slightly burned ? would that cause this kind of issue i feel i could replace it with an identical one from another board ? any feed back appreciated
Really can't say I'm afraid. I'd just be guessing as it's not an amp I've had a lot to do with.
I have one of these, and sometimes, not all the time, I would turn it on and it would make this constant loud ass popping sound. Any idea what's wrong with it? Should I just try to sell it on reverb and state the problem? Should I just throw it away?
Could just want a spray of contact cleaner lube in the control pots and the jack connectors
@@killcar5nbike2 you think that'll work? You think the issue is the connection with the speaker cable or something?
@@chrisgoodrich46 if there's a bad connection on a signal level signal it will be amplified. Just do the pots and sockets. It can only help.
Unlikely it's on the speaker lead, that would be more of a crackle/intermittent connection
hi,so mine mg100 hcfx...the sound is like "iiiiiiiii........".so.iam mentioned on your comment look likes.its just broke the chip diode and fuze...and replace it?.zero elektronic experince...longstory short..its broken because "maybe" i use for re amping modeling when mixing(its already not work,but before re amping its working well with my input guitar to out the cabinet).after that..my head not working..and justt..."iiiiiiii.......".have any idea...thanks alot.plis reply
It is possible. The line voltage coming from a mixer is A LOT more than an instrument output.
@@natetolbert3671 thanks alot.so,keep in mind...how to use reamping with head for mixing? ist direct box or maybe there any specific tool for change the impedancy..iam sorry if my question confusing.once again..thanks for reply
i have had this amp head since 2000 so new.and just as of last week i have no signal no sound at all going the the cabinet it is plugged into.i have changed the chip board years ago the one by the fan in the back. any thoughts?
Is the fuse on the board blown? Good chance the chip has blown again.
@@killcar5nbike2 Yeah mine has blown 4 times in 20 years. I eventually just gave up; it now makes an excellent coffee table...
In fact, by the last time, most of the solder pads had broken/ worn away. I had to use jumper wires to make it work.
Hi, which equivalent zener diode did you use to replace the original 1N5238B ?? thanks
Off the top of my head it was a 12v 1/2 watt. I'd have to watch the video but I'm fairly certain I mention the voltage I used or voltage I measured after replacing it.
@@killcar5nbike2 After I replaced the TDA7293, the fuse still blew, I checked the Diode and it was a shorted, I have a few diodes in my bin but not the 1N5238B. This one is 8.7V 0.5W zener diode, let me know if you find out what is a suitable equivalent diode. thank you.
so having just bought one of these second hand should i get a better heatsink straightaway?
A more substantial chunk of metal would help. Big heat sink with proper air flow would be a big improvement.
As it is if you go no lower than 16 ohm load it should be just fine.
Can you fix mine
My power switch broke, how do I fix it
Yeah so did mine did you ever figure it out?
If so please tell me how
My MG 250DFX 2 X 50W stereo only works with a pedal in the loop Pffff
The connections for pedals are make/break. Try some servisol super 10 in the connector, and cycle plugging unplugging a connector in the socket about 50 times. Make sure you come fully out, and go fully in to work all the contacts.
just got one used and there is a buzzing like an unplugged cable noise
Are you drinking whiskey?
Yes, Single malt Scotch.