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 Forum index » DIY Hardware and Software » Circuit Bending
Roland TR-707 ??
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misjah



Joined: Aug 21, 2010
Posts: 2
Location: naisus

PostPosted: Sat Aug 21, 2010 7:37 am    Post subject: Reply with quote  Mark this post and the followings unread

Hello all! I just got 707, really bad condition but I fixed most of the stuff (power supply, jumper cables between boards, sliders etc.) The only thing that isn't working is Hi HAT. No sound at all ( both master and separate OUT). Buttons are OK, slider POT is also fine. What else should I check here? (I hope it's not bad ROM)
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electri-fire



Joined: Jul 26, 2006
Posts: 535
Location: breda nl
Audio files: 4
G2 patch files: 4

PostPosted: Sat Aug 21, 2010 8:02 am    Post subject: Reply with quote  Mark this post and the followings unread

misjah wrote:
Hello all! I just got 707, really bad condition but I fixed most of the stuff (power supply, jumper cables between boards, sliders etc.) The only thing that isn't working is Hi HAT. No sound at all ( both master and separate OUT). Buttons are OK, slider POT is also fine. What else should I check here? (I hope it's not bad ROM)


If worked on TR-505, not 707 , but they're similar so ...

Are the individual outs take from near a row of transistors? These would be the VCAs. You could check the signals back from the Hihat transistor. Maybe the Hihat transistor is dead.
Connect the signal prior to the transistor to another transistor that works to see if you get a Hihat going on another channel.

These VCA transistors need an envelope control voltage. These come from a row of capacitors. You can superimpose the Envelope voltage on another channel, see if it works.

Further upstream there's separate gates that start an oscillator driving a counter to generate adresses to read each sound. Here it gets complicated, If I remember corectly the adresses and readouts are multiplexed ( combined) into a single data stream, and demultiplexed to send the appropriate data to their appointed outputs.

But your most likely candidate is the VCA transistor I think.
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misjah



Joined: Aug 21, 2010
Posts: 2
Location: naisus

PostPosted: Sun Aug 22, 2010 11:34 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanx for quick response. There are 5 M5218L dual op amps for 10 sliders. I'll try to swap them first to see if this one is dead. This is on volume board.
I did a quick transistor check on main (voicing) board and they all seem OK.

Edit: nope, that didn't work....
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