Circuitbenders Forum
Circuitbenders Forum => Drum machines => Circuitbending discussion => Roland & Boss => Topic started by: gmeredith on November 06, 2008, 04:41:25 AM
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Hey all,
I just scored a TR33 from a recycle shop for $15 hehe! It's an old boom-chick preset drum rhythm box from 1972. It's actually a great project subject because its sounds are of the CR78 style drum sounds, the forerunner to the TR808.
Inside, the circuit boards are all discrete transistors and components, and is a delight to poke around in (WARNING this is a mains powered device!!!!) if you are careful.
So far, I've been able to isolate most of the individual sounds and output them with separate out jacks. The Kick drum, Low and Hi Congas all have their own volume, pitch and decay trimpots. I'm going to mount these controls on the outside.
I've also found an output point that gives the Kick drum a much sharper, punchier sound (tapping off a pre-filter point). It sounds much more like the classic TR808 sound now, and if you turn up the decay trimmer on it you get that real big boom boom boom techno 808 kick, hehe !!
At the moment I'm trying to shape the snare sound - it's made up of 2 sounds - the "pfffttt" type noise, and also a wood block type sound for the snare "ring", which end up getting mixed together at one point in the circuit. I've got outs for both oscillators and mix them together externally. I've also added a pot/capacitor control for the "pfffttt" part of the snare that can dial in or out bottom end to fatten or thin it out.
I'd also like to look at manually triggering all the sounds, maybe even via MIDI. But that's later.
I'll upload some photos as I get these things sorted out, as well as some diagrams of all the points of interest, in case anyone else comes across one of these beasties!!
Cheers, Graham
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wooh that is fantastic find ! you must be happy
maybe you could use one of these to trigger http://highlyliquid.com/kits/decoder.html
or find some points inside that change the rhythm
congratulations !
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I was thinking about one of the MIDI kits from Highly Liquid but i didn't know about that one. That might do the trick.
Cheers, Graham
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Well, I've just managed to find a service manual for it from a synth repair tech guy. This shoud answer all of my remaining questions regarding modding this thing ;D
This guy has lots of service manuals and schematics, in pdf format for only $15;
http://www.muzikelektronix.com/MEsmListing.txt
I've pretty much mamaged to do everything I wanted to do to this machine.
I've got separate outputs for:
Kick, snare, hihats, low conga, high conga, rimshot/cowbell/claves. These last 3 share an output because the same oscillator produces all 3 of those sounds.
Controls for sounds :
Kick - pitch, decay, punch (sharp attack control)
Snare - ring, hiss, bottom end
Low conga - pitch, decay
High conga - pitch, decay
Mix output - volume, tone
Once I've got all the pots and sockets mounted nicely and I've played with it for a while, I'm going to look at adding MIDI, or at least triggering the sounds manually. I already have found some trigger points that fire some sounds when you touch them with a probe, from what I understand the early roland machines use a negative voltage pulse to trigger the oscillators, so this should be fairly simple.
I've printed out a nice control panel template to mount all my controls on the front panel, check it out below. I'll take photos of my finished work, inside and out, very soon!!
cheers, graham
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Cheers for that link Graham, he's got a service manual I was after
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OK, here's some pics of my prototype!
The fascia design was drawn up in a photo program and then printed out onto paper, then laminated. Easy!
The MIDI section is not installed yet so the front panel MIDI controls are vacant in that part.
The wooden sides are made of rare Tasmanian Huon Pine, I've yet to fine sand them and varnish them.
Cheers, Graham
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and some more:
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mp3! mp3! ;D
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I'll get some samples very soon - especially of that new fat kick drum hehe!
Cheers, graham
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OK, here are a few mp3's of the some of the modded sounds, at the bottom of this thread here:
http://www.vintagesynth.com/forum/viewtopic.php?f=5&t=42957
I'd post them here but this site won't upload the mp3's
Cheers, Graham
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very nice job, Graham !
i love that kick :P
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Nice work Graham that's absolutly stunning. Maybe starting to look for one if i can find one.
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If you do, you'll find it easy to work on, since you were doing your DR55. It sounds similar to it, but the boards are nice and big and spread out.
Cheers, Graham
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Niiiice does it still play the preset rhythms?
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Yes, all the original functionality is still completely intact. When I do get the MIDI IN board for it, I will be able to run the preset rhythms and add extra drum hits via a MIDI sequencer, if I wanted to do that (although I think I'll end up just sequencing the whole rhythm and just use the machine as a sound module - easier than bothering to sync it to a sequencer).
Cheers, graham
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Just downloaded the 3 zip packs but this sounds good Graham.....nice deep BD, and i like the conga sounds. Could you maybe upload a bigger mp3 to vintagesynth? Like a pattern or something.
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No problems! I'll try and get one happening this week.
Cheers, Graham
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looking forward to it......the BD of the TR33 is way deeper than that of the Dr55......they are both boomers but the Dr55 has more punch in it while the TR33 is more a constant door shaker. I really want one now!!! Nice to stack with the Dr and a 606...jumjum...
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Yeah, i'm pretty impressed by that kick. It really is BIG when I run it through my PA speakers. An interesting thing too is that there is an adjustment pot in the main mix out that I originally thought was a tone control, but is actually a noise balance control for the noise oscillators (for the noise part of the snare, hihats and cymbals) - when you turn it all the way down, the hihats disappear and the snare becomes this amazing sharp impulse click noise, like something Kraftwerk used in their song "Numbers".
Here is a small demo with the modded kick, with lots of decay. The snare is also tweaked so as to be not so ringy and is more hissy. Also, using the individual outs has made it possible to clean up the sounds. Compare this to the "TR33 original preset" in the next post below.
Cheers, Graham
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The original sounds:
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Hi
I have just got myself a tr-33 and would like to mod it like some of then users did on previous post.
I would need a bit of guidance perhaps mod schematic or such to help me out!!!
anyone out there have some aditionnal technical info.?
thanks
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Sorry for missing this post for such a long time!
Here's the TR33 service manual on my band's website:
http://www.warningwillrobinson.com.au/index_files/InstrumentManuals.htm (http://www.warningwillrobinson.com.au/index_files/InstrumentManuals.htm)
Cheers, graham
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its almost as if you're taunting me! ::)
I've just spend about 2 days searching everywhere for a service manual or schematic for a TR55, and all i can find is the TR33 and TR77. Its like the TR55 doesn't exist.
You wouldn't have to know a source of those ancient inductors that are used in these machines would you? I'm guessing they were custom wound for Roland, but the rimshot in this TR55 seems to have a dead one and i'm having difficulty finding anything close to a drop in replacement.
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Again, sorry about being so slow in replying - uni semester has been busy. I've also switched on the notifications funtion on this board so i get emailed when you reply ::)
No, i don't know where you could get an exact inductor from but I do know that you could swap it for another sound's inductor of the same kind and rating to at least test that that is what is wrong. Have you troubleshooted it to the inductor? Swapping one would confirm this - and at least if there is some sound that is not used much like a maraca or something then you've got your snare back and happening and fix the maraca at a later date. You could also have a go at hand-winding the dead one - you have nothing to lose if you know it is actually dead.
Cheers, Graham
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This guy here claims to have the TR55 service manual on his lists, you could give him a try:
http://synthsfl.tripod.com/smanuals.html (http://synthsfl.tripod.com/smanuals.html)
cheers, graham
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I swapped the inductor from one of the bongos with the rimshot and it worked, albeit at the wrong pitch, so it must be the inductor thats gone. Having said that, it doesn't test as being dead in any sense other than that it just doesn't work so i'm starting to think its not the original part anyway. How can an inductor possibly just stop working, its just a coil of wire?
Every inductor in these machines appears to be custom wound for each sound, and none of them are labelled, so without the schematic theres very little chance of finding out whats meant to be in there. Even if i could find out what its meant to be, i don't think anyone has made inductors of values that big since the 70's.
Why did i throw away those late 70's radios i had a while back without harvesting them for parts first! ::)
Looks like i'll have to actually pay for a service manual! :o
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"How can an inductor possibly just stop working, its just a coil of wire?"
It goes open-circuit. Are there really no markings at all on it? You could measure the one you tested it with, and see if you can guess what would be close.
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Theres four others in there that look absolutely identical but measure anywhere between 30mH and an astonishing 1430mH. Three of them have a resistance of between 30-60 ohm, but the 1430mH one measures 4.3K, which is ridiculous. Thats measuring them out of circuit
They all have a V followed by a number on the top, i.e V52, but i don't think that relates to the inductance value. I'm guessing thats a Roland code.
The rimshot/clave circuit in the TR33 which is very simliar to the TR55 has a 700mH inductor on the schematic.
The dead one in this TR55 appears to measure at around 36mH, with about 30ohms resistance, but it seems to just be acting as a dead short in the circuit. I'm not sure i trust the reading, especially as the 1430mH / 4.3K one seems to sound nearly correct for a Roland rimshot when i stick it in the circuit.
I actually unwound the dead one and rewound it, testing it every foot or so to see if it unwinding it had stopped a short. Theres no breaks and no shorts in it.
I've just ordered a load of various inductors from mouser so hopefully i'll be able to bodge something together that gets close to what the original was meant to be.
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Well that is totally confusing then. They must be an in-house roland component, wound specailly to suit them. Hopefully that means that you can wind your own to make it work then - maybe also you can make custom ones that will give your snare a modded sound.
cheers, Graham
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Measuring the resistance won't be helpful unless you use a true DC ohmmeter - most digital multimeters get horribly upset when you try to measure the resistance of a reactive component ;-)
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which is why i used an old AVO analogue ohmmeter i've had kicking around for years ;)
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Well, i just hooked together 10 x 150mH inductors in series and its almost there. It sounds like it could do with about 2 or 3 more to take the pitch down a little so its more like the original sound i've heard on youtube demos of the TR55, but its certainly usable.
I guess the original inductor must be meant to be something like 1.8 - 2H. :o
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Will changing any of the other component values in the network change the pitch instead eg. resistors or caps??
Cheers, graham
PS you've got to do a MIDI fitout to program your own crazy rhythms from a sequencer on this thing - I'm going to do it to my TR33 when I get through all my other projects ::)
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I just tried exactly that about 10 minutes after my last post. In the TR33 service manual theres a section on adjusting the sounds and it mentions adding smaller caps in parallel with the coil if the sound isn't tuned quite right, i.e. adding extra capacitance to the LC circuit.
On the TR55 theres actually a couple of empty holes in parallel with the coil to add extra caps. I just added a bit more capacitance and now its sounding pretty much spot on.
The next problem is that fact that both the hi and low conga/bongo LC circuits are constantly oscillating very quietly so theres a kind of low humming noise floor, kind of like a mains hum. TR77's are also a nightmare for this and despite all my efforts i never managed to iron it out on one of those, so i'm pretty much certain that this is impossible to eliminate, unless anyone has any ideas? The hum is definitely coming from the inductor circuit on each sound as i can change the pitch with the same adding capacitance technique.
If i can't sort out the noise floor, i'm not sure theres any point to installing midi, but its next on the list.
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In section 11-3-3-2 of the TR33 service manual, it mentions adjusting the "semi-fixed resistor VR305" to adjust the decay time - I'm thinking maybe the decay time on your congas are too long, such that they never completely shut down - or their output adjust volume is too high. Maybe that will relate somehow to your 55?? In section 11-3-3-6 there is a specs chart for all of the drum sounds, including peak output voltages, decay times etc. Methinks an oscilliscope might be needed to see what's going on with your congas.
Also, take a look at my individual output mod I did for the 33 - there are output points on the board for some of the instruments, and for the ones where there isn't, just poke arounnd the transistor solder points with a small set of computer speakers and some multimeter probes/clips attached to the speaker input plug. if nothing else, it may help you to process troublesome voices individually (like a noise gate pedal on the conga out etc)
Cheers, Graham
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Hello TR 33 owners
Glade to know this post is still alive... :D
I would like to simply mod the TR 33 with Din sync, I have tried to locate where and what to solder using the tr77 mod thinking it will be the same thing but havent found anything yet.!!
http://www.burnkit2600.com/tr-77/ (http://www.burnkit2600.com/tr-77/)
If someone could point me into a dirrection with the TR 33 how to do the same thing ( will be very appreciated )
I need to sync it up with my Akai mpc and Doepfer Mcv 24 that give me the ability to have differents/ any PPQN I want.
Best regards,