JCM 2000 DSL

[Mats A]

Thinking of buying a used JCM 2000 DSL. Read something about the earlier ones is not as well made and not as good. Is there any trruth in that? There is one from around 98 that i can buy.

[Wildone]

I would argue that thats not true, I had a DSL years ago and it was ok. Never was blown away with the amp. When I got to play a Vintage Modern I got rid of it.

[Mats A]

You mean a DSL from 98 in good condition is just as good and is a good buy if the price is right.

[Sully807]

The way I see it is there seem to be quite a few 98 models still going, if it's lasted this long and it's still in good shape and havnt had anything go bad all this time it's probably safe

[Mats A]

You mean there is few 90's DSL amps still working. How do you know that?

[Anitoli]

Considering it's used and a 98 which makes it 16 years old you might want to have at the very least all the filter electrolytics replaced. This will put a lot of balls back into the amp. I just did this to two mid 90's 6100"s and the difference was VERY noticeable.

[Mats A]

Is age a big issue with Marshalls if they've been taken care of. Old Plexis is quite expensive and sought after.

[Anitoli]

I don't think age has any effect on a Marshall's desirability, in fact I think it adds to it for certain models. Only thing is with all of these amps is they will need maintenance after so many years and its not a defect with the amp it's just that certain parts will degrade with usage and time namely the tubes and the capacitors. I wouldn't even think of running a 60's-70's-80's head with original caps. That's just asking for trouble. Doesn't mean it wont work but the likely hood of a failure gets higher the older the caps are.

[Mats A]

Some techs say electrolytic caps were not as good before as they are nowdays. If they don't look dammaged or leak there is no need to replace them.

[Anitoli]

Nope, that is completely false. Even though a cap doesn't shoe signs of external damage, i/e leaking or bulging in the aluminum case, that doesn't mean the cap hasn't started to dry out. The electrolyite is a paste and will dry out just sitting there unused on a shelf or in equipment. As the cap starts to dry out the ESR increases:

"Capacitors[edit]

In a non-electrolytic capacitor and electrolytic capacitors with solid electrolyte the metallic resistance of the leads and electrodes and losses in the dielectric cause the ESR. Typically quoted values of ESR for ceramic capacitors are between 0.01 and 0.1 ohms. ESR of non-electrolytic capacitors tends to be fairly stable over time; for most purposes real non-electrolytic capacitors can be treated as ideal components.

Aluminium and tantalum electrolytic capacitors with non solid electrolyte have much higher ESR values, up to several ohms, and ESR tends to increase with frequency due to effects of the electrolyte. A very serious problem, particularly with aluminium electrolytics, is that ESR increases over time with use; ESR can increase enough to cause circuit malfunction and even component damage,[1] although measured capacitance may remain within tolerance. While this happens with normal aging, high temperatures and large ripple current exacerbate the problem. In a circuit with significant ripple current, an increase in ESR will increase heat dissipation, thus accelerating aging.

Electrolytic capacitors rated for high-temperature operation and of higher quality than basic consumer-grade parts are less susceptible to become prematurely unusable due to ESR increase. A cheap electrolytic capacitor may be rated for a life of less than 1000 hours at 85°C (a year is about 9000 hours). Higher-grade parts are typically rated at a few thousand hours at maximum rated temperature, as can be seen from manufacturers' datasheets. Electrolytics of higher capacitance have lower ESR; if ESR is critical, specification of a part of larger capacitance than is otherwise required may be advantageous.

Polymer capacitors usually have lower ESR than wet-electrolytic of same value, and stable under varying temperature. Therefore polymer capacitors can handle higher ripple current. From about 2007 it became common for better-quality computer motherboards to use only polymer capacitors where wet electrolytics had been used previously.[2]

The ESR of capacitors of relatively high capacity (from about 1 μF), which are the ones likely to cause trouble, is easily measured in-circuit with an ESR meter."

As stated above they will wear out. The second paragraph is key.

[Mats A]

IF it sounds good why mess with it. The amp was checked and messured last year and it got new valves.

[Anitoli]

Ultimately it's the owners call. When you have a power filter that shorts ( and eventually they will ) and it takes out your PT, Changing the oil in the car, so to speak is much cheaper than replacing the motor. Even though the caps may "test" ok that doesn't take into account ripple rejection as they age.
They also lose the ability to supply/store current, which is drawn by the remaining circuit.

After 10 years it is generally understood that filter cap replacement should be considered.

[Mats A]

How do one know if they really needs to be changed if they look alright and doesn't leak?

[Mats A]

And the amp sounds good

[Anitoli]

Unless you have an actual ESR meter ( which are very expensive compared to capacitors which are relatively cheap ) you just base it on how old the amp is, how hard it's been used ( weekend warrior, low volume jammer Vs rehearsing/gigging player) over how many years this goes on. Remember heat also plays a part in aging caps and tube amps get very warm. The generally accepted notion is after 10 years it should be considered but not nessesarily critical. Beyond 20 years absolutely, change them.

I just did two 6100's made in 98 that worked before I did the job and the difference was undeniable. Prior to the cap job the amps were noisy, weak, and lifeless. After they are bitching man. The power is back, the tone is spot on, and they are very, very quite even with the gain on these.

Im not telling ya what to do but you might be surprised if you did.