h4r01d

Hi, I´m new in this forum and I´m writing to see if anybody can help me with a Issue that I get a week ago.
I was playing with my Jcm2000 and suddenly the sound stop, the amp was working but I can't get any sound from the amp. I turned it off and like about 5 minutes I turned it on again to see if it was a problem with the cabinet. The amps starts to working well and then it stop again!. This time I check it the tubes zone and I saw that the first two 12axt went off and the others (plus the tubes on the power amp) were on. So right now, the only way that I can play with my amp is to "heat it" like one hour before I use it, and it works but..... on the run the first 12axt will turn it off and the second one seems to be less iluminated compared to the others two remaining; the amp continues to work but the sound is affected with a lack of volume and overdrive.
I hope anyone out there can help me.... thanks!

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TheShadowNinja

please tell me you are running the right ohms....

other than that, it sounds like the valves need replacing.

h4r01d

Thanks for the help, I'll be checking my preamps valves 'cause I'm running the amp with the rights ohm.

American Viking

JCM2000's have kind of a safety catch that they shut themselves down if impedance is mismatched. If you have a blown speaker in the cabinet then the impedance won't be right and the amp will keep trying to power down. This happened to me before.

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Transformers inside amplifiers were not originally designed to be in there, and the tube was not created for the guitar amp.
ANY recommended idle current is a guideline and in no way a necessary requirement. There is no skeleton key for any tube amp.

PaoloJM

To me this sounds more like a problem in the heater circuit.
All symptoms point there: valve not lighting, taking a long time to heat, low gain, very little overdrive.
DSLs are prone to poor solder joints making intermittant connections. Pins 4,5 and 9 are the heater pins for the preamp valves. I would start by touching these up.
The first two preamp valves are feed from a DC supply. Perhaps there's a problem there? Faulty rectifiers (BR1), filter caps (C1 and C2) again check for dodgy solder joints?

Impedance mis-match wont affect the preamp stages.

If you don't have any experience in electronics then take your amp to a technician to have this done. The DSL is a particularily complicated, poorly made/designed amp and not the amp a beginner should be working on.
It also contains dangerous voltages, and you will be the amp live and open for testing.

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I think PaoloJM hit the nail on the head, sounds like a bad solder joint. If the rectifier was flaking out it would affect all the preamp tubes. One way to check to see if it is a bad solder joint would be to gently grasp the second tube when it doesn't light, and gently again, wiggle it slightly to see if it comes on. That is by no means a cure but it would indicate a possible bad solder joint. If you or a friend are/is handy with a soldering iron it may be an easy fix but there are lethal voltages present even when the amp is off and unplugged, the filter caps need to be drained before poking around inside the amp.

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h4r01d

Thanks everybody!, But checking the response of Shadowninja, yesterday I tried changing the valves position and to my surprise one of the tubes went off and was the one that used to be en V1, so I'll be buying a new set of12ax7s.
And for Paolo when you wrote "All symptoms point there: valve not lighting, taking a long time to heat, low gain, very little overdrive." My amp doesn't take a long time to heat, I meant that I needed to turn on my amp like half hour so that valve doesn't went off, but like I saw yesterdat that valve went off in another V's position.
Now I'll be buying a JJ803s for my V1, and tungsols for v2 v3 & v4, so I can get more loder andhi-gain, that configuration works well for that matter?
Thanks again for everything!

RiverRatt

Glad it worked out for you harold. I'm glad your complicated, poorly designed, cold solder joint filled DSL head only had a bad preamp tube. Mine's been working fine for going on 10 years (it was made in 2000)... well, to be fair, I had to replace the HT fuse once. I just hate reading posts like this where people trash DSL amps. In the real world, the DSL is a workhorse of an amp that sounds great, is very reliable, and rarely needs servicing, especially if you know a little about tube amp maintenance and care.

MartyStrat54

Just wanted to let you know that the latest tube news is concerning Tung-Sol. Their 12AX7 is not holding up well in V3 (tone stack/cathode follower). I would recommend that you go with a different tube in that position. If you have already bought it, keep an eye on it. It may or may not last.

Here's the thread. They are talking about a different amp, but that doesn't matter.

These pre-amp valves for my 2203.....

Marty

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MARTY

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PaoloJM

I apologise completeley if you were offended by my comments, that was not my intention.
My comments were based on my findings so far as a service technician, I understand many other technicians also share the same opinion.
The purpose of my post was to try and help the guy out and not to offend you or anyone else.

From the original post there two faulty valve positions, V1 and V2. Glad to hear that it appears one was a faulty valve, what about the other one, was it a faulty valve too?
It would seem odd that both V1 and V2 valves had a heater failures, particularily seen as both are heated from DC, umlike the other valves in the amp, but perhaps/hopefully it is just coincidence.

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RiverRatt

I'm not offended really, just a bit miffed that the JCM2000 series seems to get an undue amount of bad hype. I don't believe that they are any worse than any other line of amps that are wave soldered, including the current Vintage Modern and JVM models. With a wave solderer, you are going to have some bad solder joints - there's no way around it. I don't believe that means that the DSL and TSL circuts are poorly designed, just that they made so many that a few bad ones are going to slip past quality control. It seems like every Marshall model since the Plexi's has its detractors, whether deservedly or not. I've seen metal panels that had cutouts for cooling fans, heard horror stories about JCM 600's that had heat issues, 6100's that have MIDI controllers that are prone to fail. Fact is, we usually only hear from the people who have faulty amps - not the thousands who have amps that never need servicing. These are all great amps or we wouldn't be here talking about them.
If I understood the original problem, V1 was not lighting up and V2 wasn't as bright as the others, which isn't unusual. The fact that the problem followed the valve that was in V1 to me indicates that it needs to be replaced. If the replacement valve fails as well, then start looking for something more complicated. I'll always try the cheapest fix first.

MartyStrat54

Following along with what Ratt was saying. I think you will find that Marshall sold a boatload of DSL amps (TSL as well). In fact, if Marshall were to release sales info, I wouldn't be surprised if the DSL was one of their top-sellers.

I posted something a long time ago. If you make X amount of product, you will have Y amount of failure. This is just basic common business logic. No one makes a product (especially a complicated one) where every unit is perfect. When you are dealing with an electronic product, there are always going to be some bad eggs.

Ratt is correct. 99 per cent of the people who post about their DSL needs help with an issue. Rarely does anyone post that their DSL is the love of their lives. It gives a false impression that the DSL is prone to all sorts of failures. That's too bad, because the DSL doesn't deserve that sort of reputation. It's as reliable as any other guitar amp.

I think the DSL is owed an apology.

Marty

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MARTY

2009 Gibson Explorer-Hell Raising Machine
1989 Fender Strat Plus USA
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TSL100
TSL122
TSL602 #1
TSL602 #2
DSL401 #1
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jcmjmp

The only Marshalls I've ever had a problem with were my 2550 Silver Jubilee and a solid state 75w reverb. Everything else, including the 12 year old DSL have been running flawlesly.

jamesbreese

Check the easy things first. The fuses. You can pull them out and visibly look to see if its blown. I blew a fuse on my DSL100 about a year ago and it was a $5 replacement from Radio Shack.

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