So, after 20 years of wanting, we finally bought a Soundmaster SR-88 on fleabay.. Paid under a ton for it, in box with manuals, with START / STOP buttons already replaced, which was nice, but the STOP key is already gammy, so i may have to revisit that despite it looking like a pain in the hole to do.
First thing was to add the SYNC IN mod, so i could clock it with something else. It's 1 pulse per step - so for every cycle of a square LFO, it will advance a step. This 'beats' against the internal clock, so you can get some serious swing if You play your cards right. You can see the mod to the left of the mods picture attached - i enclosed it in heatshrink and just layed it over the board. It works very well with the usual suspects triggering it.
Now to the Sound mods. The Trimmer on the board works with the TONE pot, it's a 470k, so you need to get that out of there and wire in a 470k pot instead to start with. This acts as a low pass filter, including some odd feedback when both TONE and it are open..
Then i set off on the Bends (thick red cables).. They are all marked with coloured circles on the pic attached - just short alike colours together as it plays for fun. They mostly cause cross triggering of the voices, and are easy ON/OFF fun to send to switches, except the WHITE one - this needs to firstly be switched, then loaded with a pot, as it causes that crazy SQUAWK trick. Its best to experiment with the value of the pot, or bridge legs of what you have with different resistors to get the right range.. This mod is pretty extreme sounding, but worth doing right.. Mess till You find a good value that doesn't pack all the action in a small area near the end of the pot's range.
Next, the sound mods (thin wires).. These are marked in Cyan shading on the pic attached - the shade will cover the points that should be bridged with caps. Nothing too clever here, just adding in (non-polar) capacitors in parallel with ones already in the circuits to change lengths and such. Nice thing is, different values give different results, so some creative use of Multi-pole/Multi Throw switches and open up fun.. Grab a 103z and a 68n cap and poke about to get a feel..
I didn't use all of the mods marked on my unit, only what i could fit on switches i mounted in the battery bay, and by using the SQ out port. NOTE: if you choose to loose the SQ out, remember to short the 2 leads as they come off the board to the socket - they carry the audio for the cym sound!
Mmm the sound on the Youtubes is very low and noisey - this was due to the crap inputs on the 1970's video machine.. the mp3 here is a bit louder and you can hear the full stupidity of it all.. TBH, the levels out of it are very very quiet as it is.. Like nowhere near LINE level.. You end up jacking the inputs on your card/desk to dangerous levels to hear it properly..
Of coarse, the mp3 mashes alot of the spikes, i guess the only way to experience the full horror is in person.. You'd certainly have to compress the crap out of it to use it live - the differences in levels are profound depending on which mode it's in.
Cool stuff. i've been looking around the web for an SR-88 manual or schematic for ages.
Haven't used my SR-88 much as it just eats through batteries in a couple of hours.
I'm trying to find out if there's a component that could be responsible for this. One of the diodes maybe, anyone got an idea on this type of stuff?
IDK, i have been using these ENERGIZER RECHARGABLES and it's been very happy, running for 2-3days non stop with no obvious issues.. They are definatly as good as if not better then top-notch Duracells.. I tried the normal non-alkaline black/silver Energizers when i first got it, and it ate them in an afternoon.. Remote control it AINT.
Although, after all the modding, plugging in the external power made it go mental - well it did the one time i did it.. In fact, it froze the memory, making changing the patterns impossible, and scrambling the patterns that WERE in ram.. After plugging in the power, it made a falling ticking noise, and then appeared to freeze until the power was removed.
Basically - you could put it into WRITE mode, and it never passed the first step, nor would even this first step change in memory. All the presets became random 'plastikman on mushies' patterns, which was actually awesome, but became annoying after a few days.
I ended up changing the 2 transistors before the ram, next to the buttons and it came back to life.
Not sure if this was related to the external power, or something i had started when looking for bends.. During the initial panic phaze of 'oh shi- i has bricked her', i did a good job of finding NOS or alternative components for all the major bits in the machine.. the only bitch to get was the ram.. 4bit ram is like not easy to find. littlediode had some though, of coarse..
My only gripe about the machine is it is SO quiet - like between Mic and Line level, and very very prone to RFI - so switch off all mobile phones when You are recording with it, and clamp that output with a compressor, or You WILL be sorry..
A friend of mine just gave me one of these about a month ago. I am definitely going to try these mods out on it! Thanks so much for posting photo's and the manual!
Go for it Tony.. Everyone that hears the 88 in the flesh is blown away with it - even without mods or in flaky condition there is something magic about it's tinny little sounds and strict timing..
i may revisit it soon for seperate outs, depending how bored i am, just to take it to the next level of awesomness.. would be handy to be able to compress the 4 sounds individually, as the hats do get very loud sometimes.. i'm thinking the only way to get away with it would be 2 x stereo minijack sockets, since there is so little space spare now, or maybe convert the current mono 1/4 inch jack socket to stereo, and add a mini stereo? Got to be worth a punt!
MOD: Soundmaster memory rhythm SR-88
LOL Wicked Noize ALERT! !
NoT fOr ArMeR 
Linear Mode
