hi there. I'm looking for some help on distinguishing the mods on my 4210. Its dated 1984 on chassis. I picked this amp up last week with then intention of possibly doing some minor mods. When i tested it out, it was just what i was looking for, it works, but not too great. It definately needs a tuneup, possibly cap and tube job. The reverb is very weak and the amp isnt very loud (my dsl5 blows it away). Pots are scratchy.... etc. Etc... so now to today. I pulled the chassis and started investigating. The amp has some mods done to it already. 2 of the clipping diodes on the gain have been lifted, but it looks like nothing else was done for this mod-no other wires added to change the circuit? It also has a small board installed in the normal channel with a 5vdc switch some resistors and some caps. I believe this would be a mod to correct the channel bleed, but im not sure. There is also a piggy backed resistor on r5? Any help on this would be appreciated. Thank you! Ps i have some pics of the board, but i cant seem to figure how to post them. It keeps saying they are too large.