YAMAHA Ne80200 Opamp crackling noise repair, Schematicand pcb available

[cajitastompboxes]

Hi from Argentina, im working on an two channel YAMAHA Pm2000 rack, from channels strips of the original board.
So i was having noise crackling in both channels, and when the gain rotary switch bypass the NE80200 at -20db, the noise it goes, so im assuming that this OPAMP its faulty or noisy.
So i take one and degooped it (its no that hard because is silicon no epoxy), and make the photos, and clon version in express pcb, also a not so good schematic, i think its correct, but im lacking some technical abilities to find out where to start, to maybe resolve the crackling issue.
Y see four diodes and they have no markings, only a number 1, maybe they are simply 4148, doubt about they been zeners of some type.
So im posting the info in case of the curiosity of someone and also asking what can be changed to fix the opamp, or what can check first maybe.
What i already done is, the solder was brittle and old so i reflow everything.
Thanks i hope the pictures can be the help for someone else.

 

[cajitastompboxes]

Update on this, I resolder every pad and connection, the noise it's gone in both channels ,so I find the fix without change components, the solder it's too old and gets brittle, very common thing in old parts.
Byeee

 

[Ike Zimbel]

Just FYI, Yamaha switched to the silicone potting, from epoxy, sometime around the early-mid 1980's. At the time I heard that this was due to the epoxy potted ones being prone to failure. This was either proven to be, or suspected of, being caused by the epoxy being too inflexible...especially in regard to thermal changes.
I had about a 1/2 dozen of these fail on me between 1979 and the mid-80's on a few different PM-700's and 2000's.
One of them failed after a performance, while I was leaning on the desk talking to a colleague. I heard the fuse resistors go with a "snap!".