Marshall JCM 2000 DSL 401 problem

[DrGonz78]

The meter I have is a decent digital meter... It's not a "Fluke" but it's a good one... Not a "bench meter" but it's ok... lol. My friend is offering me to borrow his Fluke that he used when working as a mechanic on motorcycles, so I will probably go pick that up soon too. However, I am currently using a cen-tech p377722 meter and it has been good to me so far.

Anyway, I will pull off a couple of those resistors as to do a double check of the resistance readings. I wish that I tested resistors before turning it on, because I had the caps totally drained. Well, maybe it's a component like BR1 or something that is a common problem in regards to the powering of tubes on this amp.

Please let me know if you know how to test the Bridge Rectifier. Thanks so much for being here to help me learn this stuff!
~Jer

[DrGonz78]

Yup going to the shack right now to look for the part and a heat sink would definitely be in order. I wound up testing the R117 1M resistor after de-soldering it off the board and it is fine. So, thanks again guys and will keep you posted as to if I can get this amp working.

[DrGonz78]

The BR102 that was on this amp tested as bad. So, I got a new bridge rectifier & heat sink and installed them on this amp. Still no luck. When I soldered the the BR102 on the board I used heat sink clip so the rectifier would not get too hot. Also, I just noticed that now the led lights to clean channel will not light up anymore. It will switch between crunch and lead but clean will not light up. The tubes still are not getting any juice.

All of the fuses are working as mentioned before, but I am not sure how to test F3 fuse. Not even sure about this amp and where to look for a cause to this problem anymore. Does anyone have any ideas?

[g1]

F4 is the fuse you need to check. Removed from the amp it should measure very low resistance or beep if it has continuity test/range.
You have verified 6.3Vac between W12 and W18, correct? Now you need to find out why you do NOT have 6.3Vac between pins 2 and 6 of the power tubes. Somewhere between the heater winding and the power tube sockets is a bad connection or burnt trace (unless the F4 fuse is blown).

[DrGonz78]

Well thank g-one! So, I read your post and the part "(unless the F4 fuse is blown)" made think back to the first time cracking this amp open to work on it. I have even tested this fuse a few times actually just to make triple sure. So, when I read that part it seemed like the last thing to look at by this stage, but it is not passing the continuity test and is bad. I will go pick up a fuse tomorrow and cross my fingers this is all I have to do on this amp. Thanks for the post... It got me right back to the central problem on this amp. My only worry now is that the clean LED is not on but the other two work and maybe something is shorting out that might blow this fuse. But I think F3 supports the low level voltage and would blow. If that happened... I am guessing... then none of the LED lights would work? Thanks again man!

[g1]

Don't thank me, thank OC Disorder. Please re-read his very first response to your original post.

[DrGonz78]

Hey g-one yes I am in debt to OC Disorder too. Thank you OC Disorder for helping a newbie like me and having the patience to explain all of this so clearly. Thank you to all of you on this site and thread for helping me trouble shoot my amp(s).

So, I got the tubes fired up now!! First time you see them light up it is really nice to get this point on the amp. However, like I had feared the Green LED for the clean channel won't light up and there is no sound on that channel. The Lead and Solo are working and sound great. Does anybody have an idea what components to look at first to trouble shoot this scenario? I will start to look into it myself and keep ya'll informed for more information.

Again... Thanks OC Disorder, g-one, Mark Black, Enzo, & Prairie Dawg you guys Rock!!