e-licktronic Forum

I'm also compared with tr9090 schematic.
Tr9090 schematic look same with tr909.

my real tr909 transistors are located as well as the diagram in the scheme tr909 no mistake, this is probably an error on nava909 board .... I wonder why so many people built them, and found no problems with sound)) can all still there no errors? Check again twice... Maybe mistake only nava schematic and on board all ok? you installed these transistors as indicated on the nava board, or reversed emitter and collector?

In the Roland schematic Q43 (NPN) is put in its normal biased mode. In a nutshell it acts like an amplifier. In the Nava circuit it is placed reverse biased, acting more like a switch. The circuit still works fine, however probably has decreased gain. It is most likely the reason why some are complaining that the BD is more quiet: viewtopic.php?f=24&t=889&start=10

EDIT: Transistors on BD seem to be corresponding the original schematics..

The question is, did Vincent do it on purpose for some reason, or is it just an error?

Either way, I think I'll stick to the Roland circuit as the Nava's analog part is a direct copy of it.

Grizzlydj wrote:my real tr909 transistors are located as well as the diagram in the scheme tr909 no mistake, this is probably an error on nava909 board .... I wonder why so many people built them, and found no problems with sound)) can all still there no errors? Check again twice... Maybe mistake only nava schematic and on board all ok? you installed these transistors as indicated on the nava board, or reversed emitter and collector?

It good question why)
I installed it twice, first time i installed it as nava, then as tr909, not big changes. My Bass Drum still with humm.
How is original tr909 react if turn snappy to max? My nava generate a lot of noise.

hmmm ... interesting, I will have to try when I get my boards

Did the 100k at the middle tom make any difference?

Grizzlydj wrote:hmmm ... interesting, I will have to try when I get my boards

I thought that you have tr909)

drifter7508 wrote:Did the 100k at the middle tom make any difference?

I posted in the other thread : no it doesn't make a difference for the volume

R124 is in one of the VCOs which had all the same magnitude compared to the low and high tom when I did the measurements. the problem is in the envelope circuits or already before the envelope circuits at the accent signal.. at least when I measure and compare the accent signal at the multiplexer it is lower than those from low tom and high tom, maybe someone with an oscilloscope and a proper working mid tom could do a measurement?

... but who has a "proper working" Mid Tom? No one I heard off? "All people in "Sweden" who I am in contact with (around 5) has the same result on the middle tom.