Servicing PHILIPS N4418 reel tape recorder

philips n4418 open
Great piece of gear of the 70’s and very good reel tape player . Very good and serious contruction who seems made for last and for facilitate servicing (see below the power transitors the bar which hold all the electronic part upward)
The problems here is all the belts have mold into a sort of sticky black gluey paste (nightmare to clean , going everywhere when touch it bare hand , argh !) , common problem in these gear .
Apart changing the belt after a good cleaning , and maybe put some contact spray a bit everywhere it needs , it seems everything works well .
Plan to use it as master player for tape duplication , for better quality !

DIY Germanium Diode Ring Modulator

I just built a passive germanium diode ring modulator with spare component , everywhere i see the only use of germanium diode or shottky diode for « best result » , but i think by experimenting with leds , silicon diode , and other will do the job – maybe worster ; maybe more harsher result ?
I played around with 2 deathmetal in no-input configuration (input plugged to amp output) , plugged in the 2 input of the circuit and this made sick results !