- May 24, 2011
- Reaction score
Happy to helpCool! The resolution when watching on my phone is not so good will try when I come home. Really appreciate you sharing.
Have a question. Iam currently working on the FX have changed a lot of things like jacks and and still having problems. I did the atomium mods for unity gain. The remaining problem is signal fluctuations in the fx signal in the A loop and some strange popping sounds hard to discribe like strange distortion/compression. The B loop is working. Also chasing some hum that I suspect to be related to the fx loop.
Having problems reading the schematic do you thing IC2 and 3 on the od board might be the problem? Tried to look for intermittent contact but everything seems to be fine so looking in to IC:s and optos and stuff like that? Any other idea’s?
1) Relocating the inject and removing C24 does not affect channel switching in any way. It corrects the maldesign of the circuit by cascading each stage positive - negative - positive - negative for each channel, whereas before they left it a mess by forcing 5-stages upon the clean, and for what purpose who knows. Four stages is ample for cleans, as additional stages do nothing but adduce rumble to the lows and muddy up what would otherwise be clear and clean.Looking at your schematic revisions now and have some questions.
1. The changing of the inject point and removal of MB C24 regarding the clean channel. Is this possible without changing the switching circuit?
2. When you write remove I guess you mean remove and brake that part of the circuit?
3. When removing MB C9 the changes in C17/18 how much higher than your recommended values would you advice going if I like the tone/brightness?
4.I am changing MB C8,15,23,28,29 to sozos 500V(stock values) and C6-7 and C27to Vishay1813 630V 0.022 any thoughts? is there any of these positions that are more sensitive when it comes to voltage ratings? Other caps to upgrade on MB?
5. Looking at the clean/crunch/clean boards, any caps you would advise changing to MKT1813 or Sozos? Have already put the micas across vol.pot crunch/OD (atomium mods).
6.Regaring the improved filtering MB C1-4. Ive already did a full recap. Do you still think these caps should be changes to 4700u 16V? I have som hum issues? I have moded the heaters supply so that all preamp heaters comes of BR1 not just v1-2 and the bridge elevated of the board and 8A. Here is a link to the mod: https://valvetubeguitaramps.com/marshall-jcm2000-dsl-hum-solution/
Your newest post of the schematic was better resolution that your first! Really appreciate your work. I was about to give up on this amp before I found your thread . Now the amps working and the bias is stable just some final fixes: FX Loop, new reverb tank and some upgrades! This amp is really brutal! Running it with a weber 100w greenback H clone (Legacy 12) in a iso box and a weber mass 200 to take it down a bit. Now I am loving this amp. Have a 1966 super reverb that gathering dust right now. Hats of for all the work you did and all your posts!
50V is fine. You might even do better with 105 degree types. The idea is to prolong longevity. That way you don't have to replace as often, as parts wear down over time. I read the rail a while back at 47-48V, so transient spikes do not wear too bad at 100V. Wall power fluctuates, too, so a high flux would exceed 50V easy.Looking at your rear board revisions: C29-15,16,18 what values do you recommend?
Mainboard C30 when using two 22uf tantalums can I get away with 50V rated?