Modify old drum machine (tempo click in/out?)

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hageir
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Modify old drum machine (tempo click in/out?)

Post by hageir » Sat Feb 12, 2011 7:08 pm

I have this old Multivox FR-3 which I love.

I was wondering if I could somehow put a clock input on it? (or even a clock output)
Bypass the onboard clock and have the jack/input advance it one step at a time?

Similar to the SH-101's CLK Input

Image

Somebody must've done this onto these old transistor drum machines, right?
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Re: Modify old drum machine (tempo click in/out?)

Post by blackdiscoball » Sun Feb 13, 2011 2:45 pm

ok, I have not done this but I have been thinking about it lately and I just bought an old rhythm machine to mess with and see if I could do it. My plan of attack is to look around inside and research any chips that might be in there and then find out what they are designed to do. Im hoping that I will find one that is clearly being used as a clock. If so then all you would need is to look at the data sheet and figure out how the clock is working and you might be able to do an in or an out. This is all speculation and hopefully someone chimes in here and explains how they've done it. Also does that have a start/stop function? I was just asking because I have a bliptronic1000 that you can set to only play its pattern once. It also has a start in and out. What I do is set the tempo on that the same, then sent it a gate signal once every 8 beats so that it plays its pattern once, goes to stop, then gets a gate signal telling it to start again. Its pretty reliable and works more often then not (but misses a pattern every once in a while).
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Re: Modify old drum machine (tempo click in/out?)

Post by blackdiscoball » Sun Feb 13, 2011 2:49 pm

http://matrixsynth.blogspot.com/2007/06 ... fr-3s.html also, according to one of the post on that page, they made a model of that machine with a trigger out. Id think if you could track down the schematics for it, it would be easy to duplicate as I assume they two models have the same guts.
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Re: Modify old drum machine (tempo click in/out?)

Post by hageir » Mon Feb 14, 2011 5:43 pm

hah,
that was actually an old post by me (the one on MS).

I opened him up and there are a lot VR's in there (Snare, Bass, Noise, HC, LC, etc. -I'm checking these out later)
and the main chip in it is a Sanyo LM8471, but I can't find a data-sheet for it :(

I found a description .pdf which reads:
"Rhythm Pattern Generator For Electronic Organ"

I'd be happy with a trigger out,
any suggestions?

Are there any guides to modifying any of these old drum machines?
It sure would help out..
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Re: Modify old drum machine (tempo click in/out?)

Post by prinsen » Mon Feb 14, 2011 7:11 pm

"VR's" as in voltage regulators? Odd.

Schematics? If so, please share.

I'm guessing the LM8471 takes a clock pulse signal and chops it into musically meaningful divisions. So if you've got an oscilloscope you could probe the pins of LM8471 till you find a steady-looking clock that follows tempo. That would be a place to start.

Edit: Just found the brief description of the LM8471. It seems it's got a clock oscillator built into it, so if you're lucky then the output of that oscillator is brought out to one of its pins. And then you just need to work on a way to integrate the start/stop logic levels with the clock signal and convert the resulting clock pulse levels into something useful.

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Re: Modify old drum machine (tempo click in/out?)

Post by hageir » Tue Feb 15, 2011 4:20 pm

prinsen wrote:"VR's" as in voltage regulators? Odd.

Schematics? If so, please share.

I'm guessing the LM8471 takes a clock pulse signal and chops it into musically meaningful divisions. So if you've got an oscilloscope you could probe the pins of LM8471 till you find a steady-looking clock that follows tempo. That would be a place to start.

Edit: Just found the brief description of the LM8471. It seems it's got a clock oscillator built into it, so if you're lucky then the output of that oscillator is brought out to one of its pins. And then you just need to work on a way to integrate the start/stop logic levels with the clock signal and convert the resulting clock pulse levels into something useful.
Variable Resistors (trimpots)... :) hehe
For each sound.. I wonder if it's just volume?

I don't have the schematic, it's really, really hard to find (if not impossible),
but I think I might have shot of finding a similar schematic,
because Multivox was always a rebadge of something else..

But which one I don't know;
Rhythm Ace something?

I'll check out the pins on the LM8471,
too bad there isn't a datasheet of it..

Have you done any similar mods to drum machines?
If so, which ones and what?
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Re: Modify old drum machine (tempo click in/out?)

Post by prinsen » Tue Feb 15, 2011 10:45 pm

Ah, trimpots... of course. If the circuits are typical transistor based ones, then they may be for adjustment to the point just before constant oscillation. Kind of like a decay control.

I haven't done any drum machine mods, but I did make my own transistor drum rhythm machine with custom rhythms a couple of months ago.

In case I didn't make myself clear; the mod route I was suggesting was for clock output.

External sync... hmm. If the internal oscillator of the LM8471 can't be bypassed, which I'm afraid may be the case, then you probably won't be able to clock the drum machine from an external source. Unless of course you bypass the whole thing and do trigger inputs for each drum circuit, but that would be drastic and then your beguines and rhumbas wouldn't be authentic anymore. :lol:

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Re: Modify old drum machine (tempo click in/out?)

Post by Sir Ruff » Tue Feb 15, 2011 11:31 pm

prinsen wrote:I haven't done any drum machine mods, but I did make my own transistor drum rhythm machine with custom rhythms a couple of months ago.
Would love to see some pics of this if possible!
Do you even post on vse bro?

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Re: Modify old drum machine (tempo click in/out?)

Post by prinsen » Wed Feb 16, 2011 12:17 am

No photos, sorry, I suck at documenting the projects I do for fun... I did it on breadboard, so it wasn't much of a looker anyway.

The drum circuits were similar to these Ken Stone ones + a simple noise source with a VCA for snare and hat-ish sounds. The rhythm generator had 32-steps and was based on a NAND-gate relaxation oscillator clocking four CD4017s counters with four CD4013 d-flipflops as clock dividers.

It worked great and with all those divisions and clock inversions was able to reproduce all the classic organ rhythm box patterns AND do custom ones. Calling it programmable would be stretch though.

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Re: Modify old drum machine (tempo click in/out?)

Post by meatballfulton » Wed Feb 16, 2011 2:16 am

blackdiscoball wrote:My plan of attack is to look around inside and research any chips that might be in there and then find out what they are designed to do. Im hoping that I will find one that is clearly being used as a clock.
It would be easier to just poke around with a scope.

Trace the wiring for the tempo knob and you should locate the clock source pretty quickly.
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Re: Modify old drum machine (tempo click in/out?)

Post by blackdiscoball » Sat Feb 19, 2011 2:17 am

Ok, I just got done working on two of mine, and I've managed to mod both of them to add a gate in to control the speed. I first tried poking around with a scope and looking for something that could be a clock signal and found a lot but I really have little clue how a o scope works so I didnt have much luck. What I ended up doing and please do this at your own risk (to the drum machine and your self), and I take no responsibility for how it works. What I did was to set up a clock source and make a cable that ran out from that and had both ends exposed. I attached one to ground and then used the other to poke around. This can be dangerous as the drum machine is plugged into the wall and there is the potential to be a lot of electricity so if you aren't comfortable with doing this or don't know what to watch out for please don't do it. It could also be bad for the machine if you send a voltage to something and burn it out so I would avoid any chips or transistors (although I touched a lot and didn't have anything burn out but ymmv) Having said that what I found was that while both where very different there was some similarities. Both had some adjustable pots on the inside that you could turn to adjust the tone of the different sounds, most of the componants around here are most likely going to be related to the sounds so just stay away. I just poked around until I found a section that seemed to effect the tempo somewhat. From there I just kept poking around until I found something that did change the tempo. In both units it was a capacitor and in both it seemed that the hi hat sound also controlled the tempo and in one it made the hi hat louder. Once I found that I just soldered a wire to that and the other to ground and added a jack to the outside. Now I can control the tempo with my 707 or other clock sources. This may or may not work on yours and you could run the chance of blowing something so be careful and please don't hurt yourself but if you choose to do it let us know how it goes.
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Re: Modify old drum machine (tempo click in/out?)

Post by station » Wed Aug 26, 2020 12:13 pm

hello blackdiscoball
i was wondering if you mean the trig out of 707 is your clock source or the din sync out?
thank you, station

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