16.08.2019
Posted by 

Early 90s JCM900 with two channels and reverb on both. A lot of opamps in this amp. They are used for the input and first gain stage, reverb drive and recovery, and for the boost circuit. It essentially has an overdrive pedal inserted into the front of the amp before the V1 12AX7 drives the tone stack. It is a cathode follower in the typical fashion. V2 is a gain stage and V3 is phase inverter.

  1. Marshall Jcm900 4100 Schematic Manual

The value of R17 is different on the 2 versions of the schematic for the power amp. One schematic is dated 1990 it covers the both the 4100 and the 2100 master volume MK III. R17 is part of negative feedback signal the MK had more neg feedback. Created Date: 3/3/2006 11:07:29 AM.

Somehow I lost my chassis image of this amp and all I have is a pic of the crappy re-soldering job someone did in the past. This thing had intermittent crackle and it would cut out occasionally. After re-flowing many solder connections like these ones it worked reliably. It was also extremely dirty. I’m sure cleaning the pots and tube sockets helped too.

Marshall JCM900 2100, 2101, 4100, 4101 and 4102 power supply and output section schematic

Return Policy

Marshall Jcm900 4100 Schematic Manual

Return Window

This product can be returned within 30 days of receipt.

General Terms

Items must be returned in original, as-shipped condition with all original packaging and no signs of use. Buyer assumes responsibility for all return shipping costs unless the item was not received as described.

Schematic

Refunds

Buyer receives a full refund in their original payment method less any shipping costs and a 5% restocking fee.

Special Conditions

How do i install wow addons

At GearNuts.com, we're not happy until you're totally happy. If you're not completely satisfied with your purchase for any reason, you can return it to us within 30 days. When you return a product, you can request that it be replaced with an identical item, exchange it for a different item, or request a store credit or a refund.

Jcm 900 mods

If the product you received is defective, we'll pay the shipping, both for you to return it to us and to send you a replacement. If you're returning a product for any other reason, you must pay for shipping. If your original purchase was eligible for free shipping, the original shipping cost will be deducted from your credit or refund.