Search found 213 matches

by wahee
Wed Jan 13, 2021 7:17 am
Forum: Music Tech DIY
Topic: Adding a sub oscillator to the Teisco 60F
Replies: 4
Views: 99

Re: Adding a sub oscillator to the Teisco 60F

guest wrote:
Mon Jan 11, 2021 4:53 pm
sounds great!
cheers, it's actually a decent mod to do
by wahee
Mon Jan 11, 2021 2:30 pm
Forum: Music Tech DIY
Topic: Adding a sub oscillator to the Teisco 60F
Replies: 4
Views: 99

Re: Adding a sub oscillator to the Teisco 60F

replicate the circuits in the mixer section. add a resistor from the 4024 output to the top of a 50k or 10k pot, and then take a 100k from the wiper of that put into the mixer. hi managed to get it sorted. Did as you said. I had to use quite a high value pot 500k. Then a 100k in and 47k out. Gave s...
by wahee
Sun Jan 10, 2021 2:52 pm
Forum: General Gear
Topic: VINTAGE sTIX st-305 DRUM MACHINE ISSUE
Replies: 6
Views: 578

Re: VINTAGE sTIX st-305 DRUM MACHINE ISSUE

that's me, yes got quite far with it, although not completely sorted.
by wahee
Sun Jan 10, 2021 2:13 pm
Forum: Music Tech DIY
Topic: Adding a sub oscillator to the Teisco 60F
Replies: 4
Views: 99

Adding a sub oscillator to the Teisco 60F

hi I have successfully made a very simple 4024 based sub oscillator and have tested it on a scope and it does indeed put out division of the inputted square wave. I wanted to add this to my 60f. I have successfully located the square wave output and the 4024 outputs a divided signal. I have been hav...
by wahee
Fri Sep 11, 2020 6:59 pm
Forum: Music Tech DIY
Topic: Highly Liquid Projects
Replies: 78
Views: 8596

Re: Highly Liquid Projects

excellent post, I have just ordered a CS-01 and a URM2 so will be attempting this. Thanks for the link to the old forum posts. I'll trey and document the install
by wahee
Tue Sep 08, 2020 6:23 am
Forum: Music Tech DIY
Topic: Calling Power supply gurus
Replies: 26
Views: 1028

Re: Calling Power supply gurus

FYI the wallwart is a transformer. there is no way around it. switch mode supplies have transformers. there are designs that do not have transformers. a buck converter for example. I would not show you how to do it because those systems can be deadly if they are not used properly. something you wil...
by wahee
Mon Sep 07, 2020 6:58 am
Forum: Music Tech DIY
Topic: Calling Power supply gurus
Replies: 26
Views: 1028

Re: Calling Power supply gurus

That's great I'll have a look at those devices. I think they are fixed output also.
The circuit is basic synth so nothing major in the capacitor department, just a few 220uf 16v
Thanks for your help with this.
by wahee
Sun Sep 06, 2020 8:19 am
Forum: Music Tech DIY
Topic: Calling Power supply gurus
Replies: 26
Views: 1028

Re: Calling Power supply gurus

CR4 and 6 are not there for the same reason as CR 3 and 5. You can read about them in TI's Linear Circuits Databook, Vol.3. Pg2-436 4 and 6 are for output polarity reversal and 3 and 5 are for reverse bias protection. We do tend to see 3 and 5 more often in DIY published circuits. But 4 and 6 are n...
by wahee
Sat Sep 05, 2020 7:23 pm
Forum: Music Tech DIY
Topic: Calling Power supply gurus
Replies: 26
Views: 1028

Re: Calling Power supply gurus

Very interesting, I always thought I needed a 3 tap transformer to easily get negative voltages, so this was a good if not perfect alternative No need. See this example. Not sure it needs quite so much smoothing capacitance and it only really needs CR3 and CR5 or CR4 and CR6. http://musicfromouters...
by wahee
Tue Sep 01, 2020 9:56 am
Forum: Music Tech DIY
Topic: Calling Power supply gurus
Replies: 26
Views: 1028

Re: Calling Power supply gurus

KSS wrote:
Mon Aug 31, 2020 9:47 am
C1 and C2 are providing both a storage and a phase shift function. Remember -or refer to- ELI the ICE man. ICE in this case.
Very interesting, I always thought I needed a 3 tap transformer to easily get negative voltages, so this was a good if not perfect alternative
by wahee
Sun Aug 30, 2020 4:15 pm
Forum: Music Tech DIY
Topic: Calling Power supply gurus
Replies: 26
Views: 1028

Re: Calling Power supply gurus

Yes the 2 caps should be + towards AC source, found this circuit.
bfb2a197acb9d3b895f0583608123aa1.jpg
by wahee
Fri Aug 28, 2020 6:10 pm
Forum: Music Tech DIY
Topic: Calling Power supply gurus
Replies: 26
Views: 1028

Re: Calling Power supply gurus

hi all thanks for the replies. I did get the idea of the 2 bridge rectifiers from another circuit. The capacitor orientation was copied from that but it may be wrong.

I just need to generate the -12v and +12v so this seems like a way to do it.
by wahee
Thu Aug 27, 2020 10:23 am
Forum: Music Tech DIY
Topic: Calling Power supply gurus
Replies: 26
Views: 1028

Calling Power supply gurus

hi all I was hoping to make a small desktop module which requires GND -12 & +12 rails. I don't want to use a transformer (I have seen plenty of circuits for that.) due to mains issues but rather a 15VAC wallwart. I have designed this for use with a DC barrel jack circuit and was wondering if those i...
by wahee
Mon Aug 24, 2020 6:41 pm
Forum: General Gear
Topic: OSC OSCar waveform memory
Replies: 14
Views: 1823

Re: OSC OSCar waveform memory

some details on the hum fix on my OSCar

http://www.mindburner.co.uk/synth/OSCar.html
by wahee
Thu Jun 25, 2020 4:55 am
Forum: Music Tech DIY
Topic: DIY synth cartridge
Replies: 6
Views: 477

Re: DIY synth cartridge

I used to do that with videogame cartridges - multiple games in one cartridge, selected by a DIP switch. Worked just fine. 27C64 is an EPROM, not EEPROM, as I recall (i.e. it needs a UV light to erase it). Are you sure the synth can write to it? Special programming voltages/sequences are required t...
by wahee
Thu Jun 25, 2020 4:53 am
Forum: Music Tech DIY
Topic: DIY synth cartridge
Replies: 6
Views: 477

Re: DIY synth cartridge

hi sorry I should have been more precise, the chip is an EEPROM so it should be ok to write to. I have just copied the original schematics.
It may be a Winbond or SST chip. I think Microchip make a similar one now, something like this

Microchip AT28C64B-15PU
by wahee
Wed Jun 24, 2020 5:30 am
Forum: Music Tech DIY
Topic: DIY synth cartridge
Replies: 6
Views: 477

Re: DIY synth cartridge

Assuming this is read only (in the synth), you just need to connect each of the higher address lines (A13 onwards) to 0V via a switch with a pull up to Vcc (say 1K to 4k7 ?) A higher capacity (later designed) eprom should be able to cope with the same timings as the 2764 Obviously need to avoid cha...
by wahee
Tue Jun 23, 2020 4:39 pm
Forum: Music Tech DIY
Topic: DIY synth cartridge
Replies: 6
Views: 477

DIY synth cartridge

hi all I was hoping to build a DIY synth cartridge for my SQ-80 synth. I seem to have managed to crack the circuit for a simple copy of the old original SQ80 cartridge. It uses a 27C64 eeprom but I was wondering if there was a way to use a bigger 27c512 etc eeprom to get more banks. I know there use...
by wahee
Mon Jun 15, 2020 4:49 pm
Forum: Music Tech DIY
Topic: Ensoniq Mirage Mods
Replies: 16
Views: 1406

Re: Ensoniq Mirage Mods

google MIRIMAGE

a program for making HFE files from WAV files
the HFE then should work on your GOTEK floppy emulator

they may need renamed to
DSKA0001.HFE
DSKA0002.HFE
DSK....
etc
by wahee
Thu May 07, 2020 7:17 am
Forum: Music Tech DIY
Topic: Z80 CPU voltage rail
Replies: 37
Views: 1784

Re: Z80 CPU voltage rail

just a quick message to say thanks for all the great help on this. I have decided to put this one to bed. I have not been able to locate the source of this unusual issue. I have basically replaced the entire PCB, even 74 IC's which are usually reliable, and checked traces until my eyes hurt,but some...
by wahee
Sun May 03, 2020 1:29 pm
Forum: Music Tech DIY
Topic: Z80 CPU voltage rail
Replies: 37
Views: 1784

Re: Z80 CPU voltage rail

Is it sometimes solidly high? yes but mostly not I have replaced all the IC's in the reset area and beyond, without any change unfortunately. I even carefully removed the socket for IC43 to ensure there was no lifted pads/damaged traces etc but all was ok Yes the 6116 was IC17. The other one on the...
by wahee
Thu Apr 30, 2020 11:45 am
Forum: Music Tech DIY
Topic: Z80 CPU voltage rail
Replies: 37
Views: 1784

Re: Z80 CPU voltage rail

Well at the risk of looking like a monkey trying to operate the international space station, I decided to do some probing around the reset circuit. IC42 pin 3 always goes high when power switched on As does pin 2 IC43 pin4 MREQ – nearly always has a square wave present when power switched on. Howeve...
by wahee
Wed Apr 29, 2020 8:57 am
Forum: Music Tech DIY
Topic: Z80 CPU voltage rail
Replies: 37
Views: 1784

Re: Z80 CPU voltage rail

some images of the PCBs just for info (with the Zilog 8mhz Z80) PENT1772.JPG PENT1773.JPG it's bizarre that the Zilog 8mhz CPU will not boot at all with the Z80 ACTC IC installed The D780-C1 will boot ok with it all will boot with the ATC version installed although very patchy. It's very hard to get...
by wahee
Wed Apr 29, 2020 8:52 am
Forum: Music Tech DIY
Topic: Z80 CPU voltage rail
Replies: 37
Views: 1784

Re: Z80 CPU voltage rail

One thing you should check since people have been bodging it is that one of the RAM or ROM pins has not got folded up so it looks like it is in the socket or is touching it intermittently. Then probe the whole address and data bus pin by pin looking for funny mid way levels caused by a short. Once ...
by wahee
Tue Apr 28, 2020 9:59 am
Forum: Music Tech DIY
Topic: Z80 CPU voltage rail
Replies: 37
Views: 1784

Re: Z80 CPU voltage rail

I set the scope up as follows. Trigger - single, edge, trigger - CH1 mode - normal coupling DC then used CH1 probe on pin 26 RESET. scale is 1MS x Axis here's what I got OScar.jpeg Thanks Graham for those schematics, they're much better than the ones I have. The crystal is now apparent. P is just th...

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