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Tr707 TR727 Negative vibes
Tr707 TR727 Negative vibes
The Roland TR707 and TR727 are almost exactly the same.
One of the many things they share is a particularly hard to find transformer, T1. originally made by the sumida corporation but long since discontinued.
it is unfortunately not indestructible and the only source for a replacement part is a dead tr707.
This has long been an achilies heel for the tr707, and many have given up on tr707s with dead sumida coils.
it even has its own thread on eevblog.
https://www.eevblog.com/forum/repair/10v-dc-dc-converter-repair-advice-needed/25/
harry axten, (who make a great tr707 rom swap mod btw) had a nice idea for an alternative using a single chip negative voltage converter:
https://www.facebook.com/groups/vintagesynthrepair/permalink/987500284726415
so when i had a tr707 arrive for repairs with a dead sumida coil. i knew what to do...
a Replacement for the TR707 sumida coil:
a Replacement for the TR707 sumida coil:
i've published everything on github, if anybody cares about that kind of thing:
https://github.com/ewanuno/tr707_negative_vibes
they are now available.
send me an email if you need one.
ewanuno@gmail.com
how to install:
how to install:
remove these components:
Q1, Q2, T1, D2, D3, D18, C7, C8, R1, R2
cut some 2.54mm pin headers
1x 1pin
2x 3pin
remove the middle pin on the two 3 pin strips
insert them into the bottom of the pcb, don't solder them yet...
Put it in place on the tr707, use a finger or a bit of tape to keep the single header pin from falling out. and make sure you get it lined up with the edge of the main pcb so it will fit properly in the case.
Solder the pin headers on the top of the negative vibes pcb.
Then turn the pcb over and solder them to the tr707 pcb.
That's it! go make beats! (hopefully that was the only thing wrong with your TR707....)
Make sure you put the pins in the right holes!
Errata: One of the pins is marked "NC" on the silkscreen, but it is infact connected to Vout, this will be fixed in a future revision but for now, just ignore it.
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