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How Many Slutz Here Been Bit by the DIY Bug? Keyboard Synthesizers
Old 9th January 2018
  #421
Gear Maniac
I recently finished building my Moog 1125 sample & hold 'clone'. I used an R.A.Moog 1U blanking plate, sourced a C frame and then built everything else from scratch. Here is a video...



and see some of the photo's I uploaded in this thread...

My DIY sample & hold module....
Old 10th January 2018
  #422
Quote:
Originally Posted by noddyspuncture View Post
I recently finished building my Moog 1125 sample & hold 'clone'. I used an R.A.Moog 1U blanking plate, sourced a C frame and then built everything else from scratch. Here is a video...



and see some of the photo's I uploaded in this thread...

My DIY sample & hold module....
That looks like an authentic Moog module!
Sounds great too, nice work!
Old 10th January 2018
  #423
Gear Maniac
Quote:
Originally Posted by Hollowman9 View Post
That looks like an authentic Moog module!
Sounds great too, nice work!
Thanks... but what you're hearing is actually one of my Minimoog's.

The module is just a 'controller'... it outputs trigger & random CV.
Old 10th January 2018
  #424
Quote:
Originally Posted by noddyspuncture View Post
Thanks... but what you're hearing is actually one of my Minimoog's.

The module is just a 'controller'... it outputs trigger & random CV.
Yes I gathered there was a synth out of camera making the actual sounds.
Old 14th January 2018
  #425
Here for the gear
 

Quote:
Originally Posted by bfourcade View Post
I have always fantasized with having a Yamaha CP80 in my living room... so decided to make a Rhodes clone with a CP soul

Found a Rhodes 88 rail and plastic lid and refitted a Reface CP plus built in amplification and speakers. Instant-On magic at a switch distance
Here is the first sound test on my home made Rhodes MK8 (or a Yamaha Reface CP unleashed )

How Many Slutz Here Been Bit by the DIY Bug?

YouTube


Old 14th January 2018
  #426
Lives for gear
 
midiquestions's Avatar
Quote:
Originally Posted by midiquestions View Post
Currently replacing (many) tact switches and cleaning key sensors on a JX-10, then ordering a Vecoven 4.x kit.

After that, will be attempting to get my x0xb0x to respond to MIDI again.

Then maybe figuring out why some of my MPC2000XL individual outs aren't working at full volume.

So many projects.
Looks like Vecoven will be on hold as my tact switch replacement and key contact cleaning didn't quite go as planned. Now half the keys don't work at all -- no earthly idea why -- and the Switch PCB is completely unresponsive. Hmm.

Needless to say, will be going slowly on the MPC and x0xb0x...
Old 23rd January 2018
  #427
Changing batteries on all my Kawais lately.
Did the K3m when I got it a few weeks ago and today changed the K3’s battery to get it ready for sale. I’ve got the new battery for the Q80 EXE ready to go in tomorrow or the next day. Hopefully this weekend I’ll find time for the XD-5 too.
Next I’ll make the rounds on the Yamahas I haven’t gotten to yet.
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Old 11th February 2018
  #428
I’m making repairs to my Maxi-Korg and for the life of me cannot find the part numbers for the transistors used in it.
I think all the FETs are SK30A GR and 0 but don’t know about the NPN and PNP devices.
They are all very small packages and I cannot read the numbering on them. Damn bad eyesight!
On the PCB there’s some numbers under the transistors; 693, 608,
Some also have a C above the number which is confusing because I don’t know if it stands for 2SC or to indicate the collector.
And they don’t have a flat side so I cannot tell by the orientation what the pinout is.

Anybody know this? Any help appreciated!
Old 11th February 2018
  #429
Ok by C actually is for 2SC so one is 2SC693 and the other is 2SA608 I think. Now I just need to identify the pinout since they have round packages.
The schematic and some PCB analyses will help to figure this out.
Weeee fun!
Old 11th February 2018
  #430
Restauration KORG 800DV - Le blog de crazy-patroche.over-blog.com

I had to post this someplace as it is an excellent resource for technical info on the 800DV/Maxi-Korg
Old 11th February 2018
  #431
Lives for gear
 

just managed to do the infamous C78 snare mod on the
Volca Beats. no idea how i managed not to screw it up,
it's almost invisible to the naked eye.
well, in fact, what nobody mentions anywhere is the
likelihood that you'll melt one or more of the plastic
pot spindles in the process, which i did.
i fitted a couple of wires and a female 2-pin clip, so
the capacitor can be pulled out or swapped.

conclusion: not really worth the hassle, and it's a bit
of hype. korg crippled that machine by not having accent,
so although the snare does sound a bit better, it still sounds
flat and undynamic. if anything, the old snare is more suited
in context, if you use individual stutter settings.

in contrast, fitted a battery clip in the old RX7, and that rocks.
(my week without internet)
Old 12th February 2018
  #432
Fixed the dead Ring Modulator on my Maxi-Kog!
1st I changed the two parallel tantalum capacitors because i was measuring a short circuit across them. Next I swapped the two 2SC693 transistors with the most similar ones i had on hand 2SC1775 after checking signals on their collectors. But still no functionality. However I noticed there was some signal changes and with a bit more probing realized that the signal was not making it from the 2nd stage of the circuit to the 3rd. It was hard to figure that out since the signal of one VCO is fed into both stages. So I took out the coupling cap feeding VCO to the 3rd stage and sure enough there was no signal there. Then I swapped new caps in place of all the coupling caps and bingo, Ringmod!

Since the transistors i put in have over twice as much gain as the original parts there’s a little bit of juicy overdrive that I don’t hear in demos of this synth. I’m perfectly fine with that. Gives the Ringmod a nice crunchy edge to it.

My theory is the tantalums shorted as they’re known to do and let DC from the balance trimmer circuit through to the 2nd stage transistor where it got amplified high enough to make the coupling caps fail.

The voltage rating of the coupling caps was below the power supply voltage too so i used caps with twice the voltage.
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Old 13th February 2018
  #433
Here for the gear
 

Recently found a microkorg with a slightly mangled keyboard for £80, a few minutes on the korg website and a few phonecalls and I got a new keybed for £35 from korg.

With the vids online, it was a 15 minute job to swap out the keybed unit. Not a particularly difficult job but v-satisfying as I have a new(ish) toy to play with for £115 .
Old 13th February 2018
  #434
Okie dokie, just fixed the missing triangle wave on the upper Voice. It was a bad transistor. Again I swapped the C693 with a C1775 with no problem. The upper triangle sounds more triangly than the lower voice. Probably just needs calibration.

And that wraps up the faults on this synth. It’s working 100% now.

Now I can move on to the mods - EVIL LAUGHTER!
Old 17th February 2018
  #435
electro-music.com :: View topic - Korg 900PS

Here's another helpful Maxi-Korg, 800DV related link.
I'll be using that info to guide me with adding CV/Gate inputs to mine this weekend. Wish me luck!
Old 8th March 2018
  #436
Started stuffing my mixer PCB. This one is for the mods on my Maxikorg so i am setting up the 3rd bus for high gain to allow using the low amplitude waveforms from the VCO as modulation sources.
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Old 11th March 2018
  #437
All further postings relating to the Maxi-Korg modifications will be made in this thread here....
MegaKorg - Maxi-Korg Modifications
Old 21st April 2018
  #438
My mixer PCB is nearly done now.
Just waiting on the connectors for it.
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Old 7th May 2018
  #439
Quote:
Originally Posted by Hollowman9 View Post
My mixer PCB is nearly done now.
Just waiting on the connectors for it.
That looks like a lot of work. Have you been soldering the individual circuits?
Old 8th May 2018
  #440
Quote:
Originally Posted by Synth Guru View Post
That looks like a lot of work. Have you been soldering the individual circuits?
Yeah it’s been a ton of work and over a year in the making. Everything from designing and prototyping the circuitry to laying out the PCB and soldering the components. I had the PCB itself fabricated by PCB Express. The quality is very good I highly recommend them even if they’re a bit pricey in small quantities.
Old 8th May 2018
  #441
Quote:
Originally Posted by Hollowman9 View Post
Yeah it’s been a ton of work and over a year in the making. Everything from designing and prototyping the circuitry to laying out the PCB and soldering the components. I had the PCB itself fabricated by PCB Express. The quality is very good I highly recommend them even if they’re a bit pricey in small quantities.
Very kool, keep up the good work and keep us posted on the progress.
Old 26th June 2018
  #442
One of my Alesis MicroLimiters stopped working recently. I checked the adapter and it was dead. I found a suitable replacement at the thrift store for 99 cents and tried it. The MicroLimiter still didn’t work and now the replacement adapter was dead too!

So I went down to the basement with the adapter for my other MicroLimiter and opened the failed unit up. Within seconds the rectifier diodes got too hot to touch once power was applied. The voltage regulators didn’t get hot. So I tested the diodes and they were all good. Next I tested the filter capacitors. One (C2) was a short circuit. I removed it and verified it was a short. The capacitor was rated 330uF at 35V. Closest I have on hand is 470uF at 35V so I put one in. The MicroLimiter had correct voltages on the regulators +/- 12V.
I replaced the other 3 for safe measure.
The unit works once again.

The date on its PCB is June 1988 making the components on it 30+ years old.
I guess I better go ahead and do the other one before it starts eating adapters too.

And happy 30th birthday MicroLimiter!
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Old 26th June 2018
  #443
Gear Maniac
 

i got bit good about 6 year ago and my house was taken over by components and PCBs. but **** happens and im not in a place where i can continue at the moment (not enough time, money or space).
it is always in the back of my mind and i do intend to scratch that itch again asap, but for now all my half made DIY builds and circuit bends are sitting dormant.

i got some cream for the itching but the side effects suck
Old 28th June 2018
  #444
Interesting, the other MicroLimiter uses different filter capacitors. They aren’t the miniature kind I found in the 1st one but regular sized units.
This unit assembled on 12/18/1988 making it more than half a year younger than my other one. I wonder if they found high failure rates with the miniature capacitor types and changed the part during production.

Also interestingly one of the caps has a marked inspection sticker on it. Older one didn’t have this.

Whatever the case these suckers are going bye bye anyways.
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Old 30th June 2018
  #445
MPD24 Pad Fix

I recently bought a used Akai MPD24 and was not happy with how hard I had to hit the pads on it.
Fortunately there’s a cheap solution of putting electrical tape over the sensors. It’s easy to find the videos of this online so I won’t repeat the steps here.

This morning my son and I cracked the unit open and performed the fix together. It goes alot faster with two people.

All in all it’s definitely worth the time and effort.
The pads are significantly more responsive now.
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Old 30th June 2018
  #446
Lives for gear
 

HELP!

I wasn't bitten by the DIY bug. More like it swallowed me whole. Decided to upgrade the studio last year. I now have a Hammond rig, 1" 8 track from the 70s and a 24 channel dolby sr system from the 90s. Found out that a tech visit to set up the 8 track costs as much as a $300 test tape + used iscilloscope. Seeing as how this thing needs to be constantly calibrated along with the dolby, looks like I have no choice but to learn this stuff and buy the right tools.

So, where do I start? Tube amps scare me, may farm that out. The otari has all the instructions needed for calibration, just have to learn to fly an oscilloscope. Dolby likely needs a recap. My mixer is from '97. Hopefully it doesn't need recapping yet but I wanna test anyway, plus get a better idea of performance. It uses TL072 chips throughout and I'd really like to see uf I can improve performance with a simple socketed chip swap. Read up on it and learned that you need to check all sorts of specs to make sure the new chip is compatable, over my head. Any reccomendations where I can learn this stuff (books, online etc.)?
Old 30th June 2018
  #447
Quote:
Originally Posted by EvilRoy View Post
HELP!

I wasn't bitten by the DIY bug. More like it swallowed me whole. Decided to upgrade the studio last year. I now have a Hammond rig, 1" 8 track from the 70s and a 24 channel dolby sr system from the 90s. Found out that a tech visit to set up the 8 track costs as much as a $300 test tape + used iscilloscope. Seeing as how this thing needs to be constantly calibrated along with the dolby, looks like I have no choice but to learn this stuff and buy the right tools.

So, where do I start? Tube amps scare me, may farm that out. The otari has all the instructions needed for calibration, just have to learn to fly an oscilloscope. Dolby likely needs a recap. My mixer is from '97. Hopefully it doesn't need recapping yet but I wanna test anyway, plus get a better idea of performance. It uses TL072 chips throughout and I'd really like to see uf I can improve performance with a simple socketed chip swap. Read up on it and learned that you need to check all sorts of specs to make sure the new chip is compatable, over my head. Any reccomendations where I can learn this stuff (books, online etc.)?
A computer can be used as a oscilloscope for cheap. There’s software and USB interfaces for the probes readily available and much easier to learn than an actual scope.

There’s forums for R2R enthusiasts which are a wealth of knowledge for maintenance and calibration of decks. With the effort of this and the high price of tape you might want to reconsider tape for your main recording medium.

The mixer from 97 doesn’t need a total recap yet but you might consider getting ahead of the game and at least change the filter caps in the power supply. It’s likely to lower the noise floor noticeably.
Forget about changing ICs unless you’re also willing to construct a new power supply from scratch. High performance opamps are gonna use more power than the old 072s and the power supply won’t have any overhead to handle the higher load. Take it from me this can be an ugly rabbit hole and a major headache and expense too.

But the necessary starting point for any of this is to learn basic electronics 1st. If you have no foundation with the basics then don’t even bother with DIY.

Try starting here....
Electronics - Mobile Friendly
Old 30th June 2018
  #448
Lives for gear
 

Quote:
Originally Posted by Hollowman9 View Post
A computer can be used as a oscilloscope for cheap. There’s software and USB interfaces for the probes readily available and much easier to learn than an actual scope.

There’s forums for R2R enthusiasts which are a wealth of knowledge for maintenance and calibration of decks. With the effort of this and the high price of tape you might want to reconsider tape for your main recording medium.

The mixer from 97 doesn’t need a total recap yet but you might consider getting ahead of the game and at least change the filter caps in the power supply. It’s likely to lower the noise floor noticeably.
Forget about changing ICs unless you’re also willing to construct a new power supply from scratch. High performance opamps are gonna use more power than the old 072s and the power supply won’t have any overhead to handle the higher load. Take it from me this can be an ugly rabbit hole and a major headache and expense too.

But the necessary starting point for any of this is to learn basic electronics 1st. If you have no foundation with the basics then don’t even bother with DIY.

Try starting here....
Electronics - Mobile Friendly
Great info, thanks.

The mixer (D&R Cinemix) was never commissioned and/or used, so I also think I have a few years left on the caps. I have enough mono spares to replace the whole mixer and extra 12&18v supplies. Was planning on taking 10 years to recap and replace a couple of modules at at time but doing the PS first seems like a goid idea. Didn't know about R2R forums, thanks. Found a hammond forum. Heard that you can do some oscilloscope stuff on a laptop, worth investigating although used tektronix only run about $200. Not really using the 8 track as my recording medium, just want it for bounces for tape effect plus it has 8 line and mic transformer balanced pres which I mostly got it for, the tape recorder is a bonus that I want to get running just for giggles. Everything works and it pulls tape but the cards likely need work. I know guitar electronics but I think that qualifies me as a Noob. Much to learn. Thanks for the advice.
Old 4th July 2018
  #449
Universal Gate Transliterator

There’s an aggravating problem where my Two Voice Pro cannot trigger the gate of my Roland SH-2 because its gates are only 3 volts and the SH-2 requires a minimum of 7.5V input.

So I built a quick and dirty solution for the problem out of junk I had knocking around.
It’s not designed to be pretty it just has to work and not cost money.

Gates input to it are boosted to 8.9V regardless of their original level. There’s a switch to invert the gates to convert between rising and falling gate types so as to make incompatible instruments compatible.

Inputs are minijacks. Outputs are both mini and 1/4 inch. So it can also be used as a buffered splitter.

I need to dress the internal wiring yet.

There’s two independent channels.
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Old 17 hours ago
  #450
Gear Addict
 
channelite's Avatar
I finished the Rakit Baby 8 and Drum Synth. A really cool combo for $100. Had to also buy a few extra cables too. I sync the Baby 8 to the iPad using Korg Sync Kontrol app. Also I use the app Midi Link Sync to sync with the Digitakt. Both apps are synced via Ableton Link.

My next project is to put a break out port to the Korg monotrons to use with the Baby 8.

I did also get a Weller soldering iron for Christmas, so that’s what started me down this path. Really do enjoy it, even though I made a bunch of soldering mistakes, like soldering the Baby 8’s lights on the bottom side.?
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