This amazing looking piece of vintage kit has arrived to me in near mint, untested condition. Previous owner purchased it at a fleamarket, and put it on sale online.
The machine looks amazing!
Sadly, it does power up but no sound is heard.
I decided to take a peek inside..
At first glance, i noticed the Toshiba silicon transistors.. expensive at the time (mid 60s? Looking at the wire resistors i would say so), usually Ace Tone units of this era used germanium transistors (cheaper but less reliable).. i thought “Yes..thats good! Quality stuff!”
I measured the psu filtering caps.. thinking they could be the culprit.. but erm they didnt test that bad..
Upon looking closely at the board, i noticed some weird looking blobs of coloured material, crystalized?
Thats where Denon cut corners, quality wise: these are high frequency transistors (most commonly featured in transistor radios..).
Well, heres the horror part: they destroyed, one by one, at the lightest touch. I couldnt even measure them or least of all desolder them..
I took pictures of the board earlier so at least i know where the yellow and purple ones were positioned.
But alas, some trasistor places where not even populated!
I made a rough note: yellow ones are 2SC183, purple ones must be 2SC182.. quite similar, with different frequency peak, NPN silicon type transistors.
As for the unpopulated places, looking at the underside of the board revealed some more unmarked, destroyed transistors-barely visible.
Since schematics for this drum box are all but unavailable, i tried to contact a few people online that have/had the unit (tubbutech who has his unit on repair, reverb sellers, this page dedicated to the CRB-90, hoping someone would have taken pictures of the insides.. needing to at least understand what type of transistors populate the underside of the voice board.
Since these transistors are very fragile, my advice would be to please help and SHARE pictures of your working/faulty unit internals-my trial could be yours someday (i hope not).
While i am waiting for contribution, i am subbing the broken transistors as featured in my pictures..
2SC182 NPN silicon transistors have been subbed with BC347B, 2SC183 NPN silicon with 2N5132.
Underside of board transistors: they were mounted upside down so i was able to locate TR30: it’s yet another coloured transistor: red!
But it seems the carnival isnt over.. could this be TR12? Yet another transistor: GREEN, partially readable: 183? 163?
Masuto's 