Revisited: My Marshall JCM 2000 DSL100-
I finally managed to get my amp to Keith Fain, a retired electronics tech from Beckley, West Virginia, to repair the 8-ohm input jack, clean out the chassis for dust, and test the main board for the notorious bias drift these model amps were known to have from time to time. Since I wasn’t in any hurry to get it back, I left it in Keith’s capable hands on March 16th and awaited news that the work was complete. I received my first update from Keith around April 8th when he sent me an email with an image of the main board. Shortly after, we spoke by phone about his initial thoughts on the main board. Surprisingly, the main board showed no signs of scorching or burns. Being an amp of 25 years old and manufactured before 2005, when the bias drift issue was resolved, the board was clean. Keith assured me that not all PCB boards were faulty—some never had a bias drift issue. Marshall UK confirmed this via email when I inquired about defective boards, explaining that some lots in the production line were good and others bad, and that I might have a good one. Keith did, however, change the rear input jack after discovering the old one was still inside the chassis. It looked like three of the four connectors were missing, with the last one folded underneath (see photo below); so my guess is the input connector was just rattling around. Once the initial work was completed and Keith began testing the amp, he discovered a loud hum when powering it on. The hum was evident even when plugging a cable into the front jack. It didn’t take long to find the culprit: a C-46 capacitor. Keith replaced it with one of slightly higher voltage, which eliminated the hum, then set the bias, and it was rock solid. This capacitor was the only component on the main board that showed signs of burning (see photo below). He also repaired the solder joints on the impedance selector switch, which had been causing the amp to cut out during vibration. I finally brought it home on April 28th. I’m thankful Keith was so thorough and kept me informed throughout the process. He could have just done what I asked—clean the chassis and replace the input jack—and I would have discovered the hum only later, without knowing what caused it. I cleaned the tolex with some leather cleaner and replaced the broken handle. My Marshall JCM 2000 DSL100 now has a new lease on life. The next blog will probably be a sound demo. Until then, I’ll post some important links below. You can contact Keith Fain through his Facebook page.
And since I was not in any hurry to get it back, I left it in the capable hands of Keith on March 16th and awaited word that the work was complete. I got my first update from Keith around April 8th. He sent me an email with an image of the main board. Shortly thereafter, we spoke by phone about his initial thoughts on the main board.
Surprisingly, the main board showed no signs of scorching or burns, being an amp of 25 years old, and being pre-2005, the year the bias drift issue was resolved. The board was clean. Keith went on to assure me that not all the PCB boards were faulty, that some boards never had a bias drift issue. Marshall UK reaffirmed this via email to me when I was seeking info on the defective boards, and what lots in the production line were good and bad. They too assured me not all boards were bad, and I might have had a good one. Keith did, however, change the rear input jack, and found the old one still inside the chassis. By the looks of it, 3 of the 4 connectors were missing, while the last one was folded underneath (see photo below). So, my take is the input connector was rattling around.
Once the initial work was completed and Keith was set to test the amp, this was when he discovered a humming (loud) when he powered it up, the hum was even apparent when he plugged a cable into the front jack. It didn’t take long for him to find the Culprit. It was a C-46 capacitator. Keith replaced it with a slightly higher voltage, which eliminated the hum. He then set the bias, and it was rock solid. This capacitor was the only piece on the main board that Keith had found that showed some burns. (see photo below.) He also repaired the solder joints on the impedance selector switch that was causing the amp to cut out with vibration.
I finally brought it home on April 28th. I am thankful Keith was so detailed and kept me in the loop throughout the whole process. He could have done what I requested, which was to clean the chassis and change the input jack, and I would have discovered the hum, not knowing what it was or what was causing it.
I cleaned the tolex with some leather cleaner and replaced the broken handle. My Marshall JCM 2000 DSL100 has a new lease on life.
The following blog will likely be a playthrough. Till next time, I’ll post some important links below. You can contact Keith Farin via his Facebook page below.
