VS100 Combo only works for about 5 minutes

fleshtwister · 04-25-2008, 05:18 PM

OK, First post here. I wish it wasn't for a problem.

I bought a used Marshall Combo Valvestate VS100 amp. When I got the amp all was GREAT. Now after a couple weeks of only playing it a few times a week at fairly low volumes it started to act up. When it first powers up all is good, then I start to get a crackling sound after a few minutes while playing. If I tap the top of the amp with my fist it produces the same crackle. If I keep playing for about 5 - 10 minutes it just cuts out and makes no sound at all (no guitar or anything). I also notice that the power light dims when it cuts out. If I turn the amp off, I get a real loud POP when the power switch comes out. I can turn the amp right back on and it works again but starts producing the crackling sounds.

I swapped out the tube for a new one but it made NO DIFFERENCE...

I'm going to video tape it and post a video hopefully later today. In the meantime if anyone has any suggestions, please share.

Thanks so much in advance for any help.

I shot some video to give you an idea of what's going on. You can view it on YouTube YouTube - Marshall VS100 Problems The problem spots are at about 1:40 new problem seems to have developed and can be heard about 1:50 in. The POP turning it off can be heard at about 4:15 and 4:53.

timstoel · 05-07-2008, 11:39 AM

It is most likely a bad solder joint somewhere on the PC board. The easiest way to fix it is open it up and examine the board, looking for small cracks and cold solder joints. Heating up all the solder joints on the board is a great way to eliminate that possibility. Use a very hot iron with a fine tip, because the less time you spend heating up the joints the better, as the traces can peel off the fiberglass.

Tim

fleshtwister · 05-07-2008, 02:31 PM

Thanks Tim. I'm going to pick up a soldering pencil in the next day or two. I have a Cold Heat solderer but it is hard to use when trying to heat up big pieces of solder.

I'll let you know if it helps.
Kevin

axegrinder87 · 07-30-2008, 11:20 PM

i had this same exact problem. on the mainboard, reg1 and reg2 like to get a lil too hot, and wound up crack the solder joint. i installed heatsinks to each, and resoldered them.

hope this helps

fleshtwister · 07-31-2008, 12:30 AM

I actually replaced both of those (twice). It no longer cuts out after a few minutes. Now it just stays REAL quiet. Every channel is the same with the gain and volume all the way to 10 I can barely hear it over my guitar....

Thanks for the tip anyway.

axegrinder87 · 07-31-2008, 05:01 PM

had the same problem again

twist the tube a lil bit, its not properly connected.

power it up, and put the volume up just a tad, and wiggle til it starts to glow, then itll work fine.

fleshtwister · 07-31-2008, 05:31 PM

Well, I tried twisting the tube a little and it made no difference. I even tried a new tube and it still had no change. I did catch something in the corner of my eye though. When I put the new tube in, right when I hit the power button I noticed a flash from what appeared to be the new tube. Is it possible for something to short out only part of a tube?? It still will glow but no change in the sound.

Thanks for the suggestions though, I REALLY appreciate it.

axegrinder87 · 07-31-2008, 06:17 PM

what kind of tube did you buy? as in brand and series. another possibilty is the connector on the power board, for the wires that jump it and the mainboard, on the left side. check the connections on it.

as far as a tube shorting out, ive never heard anything like that. but im no expert. it sounds though like it had connection when you first powered it up, and it lost it shortly after. i still think its just loose like i said, mine gets like that and sometimes it takes a bit of work to get it goin. mine will light up as well, but not as bright as it should until i get it connected right.

one more thing, wiggle it only a little bit at a time, as it takes a second or two for it to get working after its connected.

axegrinder87 · 07-31-2008, 06:20 PM

i forgot to mention, my new tube is a groove tubes gold series. the silver series is not supposed to be used for preamps. my stock marshall tube never has a problem with connection. i used a caliper and found that the leads on the groove tube are about 2 mils thinner, so they dont make contact as well as the marshall tube.

fleshtwister · 07-31-2008, 10:52 PM

Well I have the stock Marshall tube in there but the new one I tried is a Electro-Harmonix 12AX7 electron tube. I think I got it from the Tube Store?

I did notice that LED1 and LED2 are not as bright as they should be (like when it worked). Someone on another forum suggested I try testing the op-amp in the pre-amp. Since they are less than a buck I'm just going to replace the one that is right next to LED1 and LED2. Everytime I moved the prob around that chip the LEDs would flash so I'm hoping that might be it. If not, I'm either going to ship it off to have it fixed or put it up on eBay and cut my losses...

I tried moving the tube by turning it in small increments and pushing it down and even pulling it out and no change.

axegrinder87 · 08-02-2008, 12:58 AM

well i must say i feel for ya, these things can be pretty touchy. and trying to fix electronics can get really frustrating. im an electronics tech, so i get this crap all the time.

but as crazy as it might sound, ive never heard a better amp.

i wish you the best of luck, and if you do decide to sell, let me know a price and ill gladly take it off your hands.

Andypandapedal · 08-02-2008, 07:16 PM

The op-amps are cheap and easily available, before I do that I would get the schematic and see what the correct voltage is at the board and check to make sure it has the correct voltage, start at the beginning instead of chasing a problem you aren't sure what it is.

Take a hair dryer and shoot the PC board (get it hot) and see if that works to get the leds to glow brighter. I would also check the first resistor in line with the tube, as in the one connected to a pin on the tube socket or closest to the tube, it's free to test and if you do not have a DVM then don't open an amp and try to fix it by guessing. Get a meter (for $14.99 at radioshik) and a schematic and start at the power and head toward the IC chip, it sounds like you have a blown part that is not giving the correct value now, a blown IC usually means no sound, not some sound.

Don't chase problems, just get a meter and a schematic and you will be golden.

04-25-2008, 05:18 PM	#1 (permalink)
fleshtwister Junior Member Join Date: Apr 2008 Location: Tampa Bay, FL Posts: 5	VS100 Combo only works for about 5 minutes OK, First post here. I wish it wasn't for a problem. I bought a used Marshall Combo Valvestate VS100 amp. When I got the amp all was GREAT. Now after a couple weeks of only playing it a few times a week at fairly low volumes it started to act up. When it first powers up all is good, then I start to get a crackling sound after a few minutes while playing. If I tap the top of the amp with my fist it produces the same crackle. If I keep playing for about 5 - 10 minutes it just cuts out and makes no sound at all (no guitar or anything). I also notice that the power light dims when it cuts out. If I turn the amp off, I get a real loud POP when the power switch comes out. I can turn the amp right back on and it works again but starts producing the crackling sounds. I swapped out the tube for a new one but it made NO DIFFERENCE... I'm going to video tape it and post a video hopefully later today. In the meantime if anyone has any suggestions, please share. Thanks so much in advance for any help. I shot some video to give you an idea of what's going on. You can view it on YouTube YouTube - Marshall VS100 Problems The problem spots are at about 1:40 new problem seems to have developed and can be heard about 1:50 in. The POP turning it off can be heard at about 4:15 and 4:53. __________________ (¯`·.¸¸.-> fLeShTwIsTeR <-.¸¸.·´¯) The Puzzle Box Shop http://www.HellraiserPuzzleBox.com Last edited by fleshtwister; 04-25-2008 at 11:36 PM. Reason: Added video link

05-07-2008, 11:39 AM	#2 (permalink)
timstoel Member Join Date: Jan 2008 Posts: 62	Re: VS100 Combo only works for about 5 minutes It is most likely a bad solder joint somewhere on the PC board. The easiest way to fix it is open it up and examine the board, looking for small cracks and cold solder joints. Heating up all the solder joints on the board is a great way to eliminate that possibility. Use a very hot iron with a fine tip, because the less time you spend heating up the joints the better, as the traces can peel off the fiberglass. Tim __________________ http://www.newoldsounds.com - rare NOS capacitors, tubes, speakers and more

05-07-2008, 02:31 PM	#3 (permalink)
fleshtwister Junior Member Join Date: Apr 2008 Location: Tampa Bay, FL Posts: 5	Re: VS100 Combo only works for about 5 minutes Thanks Tim. I'm going to pick up a soldering pencil in the next day or two. I have a Cold Heat solderer but it is hard to use when trying to heat up big pieces of solder. I'll let you know if it helps. Kevin __________________ (¯`·.¸¸.-> fLeShTwIsTeR <-.¸¸.·´¯) The Puzzle Box Shop http://www.HellraiserPuzzleBox.com

07-30-2008, 11:20 PM	#4 (permalink)
axegrinder87 Junior Member Join Date: Jul 2008 Posts: 5	Re: VS100 Combo only works for about 5 minutes i had this same exact problem. on the mainboard, reg1 and reg2 like to get a lil too hot, and wound up crack the solder joint. i installed heatsinks to each, and resoldered them. hope this helps

07-31-2008, 12:30 AM	#5 (permalink)
fleshtwister Junior Member Join Date: Apr 2008 Location: Tampa Bay, FL Posts: 5	Re: VS100 Combo only works for about 5 minutes I actually replaced both of those (twice). It no longer cuts out after a few minutes. Now it just stays REAL quiet. Every channel is the same with the gain and volume all the way to 10 I can barely hear it over my guitar.... Thanks for the tip anyway. __________________ (¯`·.¸¸.-> fLeShTwIsTeR <-.¸¸.·´¯) The Puzzle Box Shop http://www.HellraiserPuzzleBox.com

07-31-2008, 05:01 PM	#6 (permalink)
axegrinder87 Junior Member Join Date: Jul 2008 Posts: 5	Re: VS100 Combo only works for about 5 minutes had the same problem again twist the tube a lil bit, its not properly connected. power it up, and put the volume up just a tad, and wiggle til it starts to glow, then itll work fine.

07-31-2008, 05:31 PM	#7 (permalink)
fleshtwister Junior Member Join Date: Apr 2008 Location: Tampa Bay, FL Posts: 5	Re: VS100 Combo only works for about 5 minutes Well, I tried twisting the tube a little and it made no difference. I even tried a new tube and it still had no change. I did catch something in the corner of my eye though. When I put the new tube in, right when I hit the power button I noticed a flash from what appeared to be the new tube. Is it possible for something to short out only part of a tube?? It still will glow but no change in the sound. Thanks for the suggestions though, I REALLY appreciate it. __________________ (¯`·.¸¸.-> fLeShTwIsTeR <-.¸¸.·´¯) The Puzzle Box Shop http://www.HellraiserPuzzleBox.com

07-31-2008, 06:17 PM	#8 (permalink)
axegrinder87 Junior Member Join Date: Jul 2008 Posts: 5	Re: VS100 Combo only works for about 5 minutes what kind of tube did you buy? as in brand and series. another possibilty is the connector on the power board, for the wires that jump it and the mainboard, on the left side. check the connections on it. as far as a tube shorting out, ive never heard anything like that. but im no expert. it sounds though like it had connection when you first powered it up, and it lost it shortly after. i still think its just loose like i said, mine gets like that and sometimes it takes a bit of work to get it goin. mine will light up as well, but not as bright as it should until i get it connected right. one more thing, wiggle it only a little bit at a time, as it takes a second or two for it to get working after its connected.

07-31-2008, 06:20 PM	#9 (permalink)
axegrinder87 Junior Member Join Date: Jul 2008 Posts: 5	Re: VS100 Combo only works for about 5 minutes i forgot to mention, my new tube is a groove tubes gold series. the silver series is not supposed to be used for preamps. my stock marshall tube never has a problem with connection. i used a caliper and found that the leads on the groove tube are about 2 mils thinner, so they dont make contact as well as the marshall tube.

07-31-2008, 10:52 PM	#10 (permalink)
fleshtwister Junior Member Join Date: Apr 2008 Location: Tampa Bay, FL Posts: 5	Re: VS100 Combo only works for about 5 minutes Well I have the stock Marshall tube in there but the new one I tried is a Electro-Harmonix 12AX7 electron tube. I think I got it from the Tube Store? I did notice that LED1 and LED2 are not as bright as they should be (like when it worked). Someone on another forum suggested I try testing the op-amp in the pre-amp. Since they are less than a buck I'm just going to replace the one that is right next to LED1 and LED2. Everytime I moved the prob around that chip the LEDs would flash so I'm hoping that might be it. If not, I'm either going to ship it off to have it fixed or put it up on eBay and cut my losses... I tried moving the tube by turning it in small increments and pushing it down and even pulling it out and no change. __________________ (¯`·.¸¸.-> fLeShTwIsTeR <-.¸¸.·´¯) The Puzzle Box Shop http://www.HellraiserPuzzleBox.com

08-02-2008, 12:58 AM	#11 (permalink)
axegrinder87 Junior Member Join Date: Jul 2008 Posts: 5	Re: VS100 Combo only works for about 5 minutes well i must say i feel for ya, these things can be pretty touchy. and trying to fix electronics can get really frustrating. im an electronics tech, so i get this crap all the time. but as crazy as it might sound, ive never heard a better amp. i wish you the best of luck, and if you do decide to sell, let me know a price and ill gladly take it off your hands.

08-02-2008, 07:16 PM	#12 (permalink)
Andypandapedal Junior Member Join Date: Jan 2008 Location: Hollywood Florida Posts: 8	Re: VS100 Combo only works for about 5 minutes The op-amps are cheap and easily available, before I do that I would get the schematic and see what the correct voltage is at the board and check to make sure it has the correct voltage, start at the beginning instead of chasing a problem you aren't sure what it is. Take a hair dryer and shoot the PC board (get it hot) and see if that works to get the leds to glow brighter. I would also check the first resistor in line with the tube, as in the one connected to a pin on the tube socket or closest to the tube, it's free to test and if you do not have a DVM then don't open an amp and try to fix it by guessing. Get a meter (for $14.99 at radioshik) and a schematic and start at the power and head toward the IC chip, it sounds like you have a blown part that is not giving the correct value now, a blown IC usually means no sound, not some sound. Don't chase problems, just get a meter and a schematic and you will be golden. __________________ "I play a Gibson into Marshall's, not only do I have a great sound, I look good doing it."

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