Search found 36 matches

by wally01
Wed Sep 25, 2019 6:32 pm
Forum: Music Tech DIY
Topic: Esq-1 keyboard repair
Replies: 20
Views: 1371

Congrats!
Glad to see it's repaired. :banana:

Cheers
Pat
:banana:
by wally01
Wed Sep 25, 2019 3:13 pm
Forum: Music Tech DIY
Topic: Esq-1 keyboard repair
Replies: 20
Views: 1371

That section of the keyboard has 2 groups of 4 keys connected together.
So yes - the 2 center pins are jumpered and the 2 outer pins are jumpered.
Glad i took a photo after i repaired my keybed.
by wally01
Wed Sep 25, 2019 2:11 pm
Forum: Music Tech DIY
Topic: Esq-1 keyboard repair
Replies: 20
Views: 1371

Good to hear you got the keystep fixed. If you lost 8 keys i'm guessing the problem is on the keybed pcb. The keybed has bus bar conductors that run the full length of the keyboard. The bus bar is connected to the keys in groups of 5 , 4, or 8 keys. I'm guessing there is a bad connection on one of t...
by wally01
Wed Sep 25, 2019 9:47 am
Forum: Music Tech DIY
Topic: Esq-1 keyboard repair
Replies: 20
Views: 1371

[quote="estin"]bumping this old thread as I have an ESQ-1 with a row of 8 dead keys. Ever find a solution? I have tried everything short of replacing the keyboard controller IC (since they no longer exist) Have you tried re-flowing the solder joints under the keyboard controller IC? My ESQ-1 had int...
by wally01
Wed Sep 18, 2019 6:03 pm
Forum: Music Tech DIY
Topic: Korg Mono/Poly Key Assigner calibration
Replies: 3
Views: 485

You're welcome!
Good luck with the calibration.

Cheers
Pat
by wally01
Wed Sep 18, 2019 11:14 am
Forum: Music Tech DIY
Topic: Korg Mono/Poly Key Assigner calibration
Replies: 3
Views: 485

If you have the service manual there is a tune switch indicated on the schematic on page 9 of the manual. It is right beside the 8049 micro. The switch is physically located in the vicinity of the mid rage adjustment pot. (page 15 of the service manual). The switch should be open under normal condit...
by wally01
Sat Aug 31, 2019 12:05 pm
Forum: Music Tech DIY
Topic: Analog Switch Confusion
Replies: 11
Views: 855

I had a quick look at the data sheet and it appears that the switching device is a mosfet. When it's switched on it has a minimum resistance of 25 ohms. Depending on the circuit you're switching it may affect the signal quality. Also
make sure you use bypass caps on the + and - V's.

Pat
by wally01
Tue Dec 11, 2018 7:47 pm
Forum: Music Tech DIY
Topic: what to do with a broken synth/sampler?
Replies: 22
Views: 1015

.[/quote] it's either that or he just made a couple of honest mistakes, I know the guy who sold me the eps was shady but the guy who I bought the spares from seemed to want to help me as much he could. idk, not much I can do about that now. gah, ebay I seem to have such bad luck with anything music ...
by wally01
Mon Dec 10, 2018 5:33 pm
Forum: Music Tech DIY
Topic: what to do with a broken synth/sampler?
Replies: 22
Views: 1015

I would consider getting it working with a floppy drive before spending any more money on it. I hate to be a downer but it sounds as if the Ebay seller was a bit doggy.The synth may have other problems not apparent until it's OS is loaded. Once you get it working with a floppy drive then i would con...
by wally01
Mon Dec 10, 2018 4:44 pm
Forum: Music Tech DIY
Topic: what to do with a broken synth/sampler?
Replies: 22
Views: 1015

What type of floppy disks came with the keyboard? The ones with the single write protect hole (double density) or the floppies with the two holes in the disk (high density). The EPS 16 plus came out in the late 80's which means it's more likely to have a double density drive installed in the unit. A...
by wally01
Mon Dec 10, 2018 3:10 pm
Forum: Music Tech DIY
Topic: what to do with a broken synth/sampler?
Replies: 22
Views: 1015

The specs for the teac fd-235hg floppy drive you have installed in the unit is a double sided high density drive (1.44 meg). The drive you need should be a double sided double density drive as used on (very) old PC's (720k).

Hope this helps.
by wally01
Wed Jan 10, 2018 6:49 am
Forum: Music Tech DIY
Topic: TTSH Ver.3 (rev.8) General build thread
Replies: 2031
Views: 118664

I have the VCO's out. I was able to get the power rails at 15 V+ and V- when i took the wiring out. But as soon as i wired it back up, the power rails went to 22- and 8+ Also on the pad to wire the speakers onto the board. I have continuity between R and G Im gonna go back to looking for a short in...
by wally01
Wed May 17, 2017 2:12 pm
Forum: Music Tech DIY
Topic: TTSH Ver.3 (rev.8) General build thread
Replies: 2031
Views: 118664

I think the problem with the speakers is that the impedance is too low for the amplifier. A Zobel network would have some effect on the back EMF. The main purpose of a Zobel network is to keep a consistent impedance load to the amplifier across the frequency spectrum. I would suggest installing an 8...
by wally01
Sat Apr 01, 2017 2:37 pm
Forum: Music Tech DIY
Topic: TTSH Ver.3 (rev.8) General build thread
Replies: 2031
Views: 118664

So after fixing the hum issue i do now have another problem: All VCOs do influence the others by changing its frequency slider. I reheated the pins several times and installed resistor legs to all the extra pins. When slider is to LF the issue disappears. Any other suggestions than reheating? I hav...
by wally01
Sat Apr 01, 2017 1:47 pm
Forum: Music Tech DIY
Topic: TTSH Ver.3 (rev.8) General build thread
Replies: 2031
Views: 118664

So after fixing the hum issue i do now have another problem: All VCOs do influence the others by changing its frequency slider. I reheated the pins several times and installed resistor legs to all the extra pins. When slider is to LF the issue disappears. Any other suggestions than reheating? I hav...
by wally01
Fri Mar 31, 2017 3:57 pm
Forum: Music Tech DIY
Topic: TTSH Ver.3 (rev.8) General build thread
Replies: 2031
Views: 118664

there shouldn't be a beep if the resistance is in the kohm range, under 10ohms usually gives a beep, maybe something wrong with your meter... That could be. It's a Fluke 179 and otherwise feels solid. I bought it second hand, maybe it needs recalibration or I have to read the manual. There seems to...
by wally01
Fri Mar 31, 2017 6:30 am
Forum: Music Tech DIY
Topic: TTSH Ver.3 (rev.8) General build thread
Replies: 2031
Views: 118664

Ok to clarify: I have to problems: 1. the left speaker (i switched left and right at the opamp output) hums slightly when the slider is not fully up (it is worse in middle position). When fully up it is as quiet as the right one If the hum stayed in the left speaker after swapping the amp connector...
by wally01
Thu Mar 30, 2017 7:53 pm
Forum: Music Tech DIY
Topic: TTSH Ver.3 (rev.8) General build thread
Replies: 2031
Views: 118664

Hum in the reverb section can be caused by poor cables or a bad/missing ground connection to the reverb spring. Classic reverb hum is difficult/impossible to produce in V3 due to fact that ground is isolated on reverb return. You need a ground loop path to produce reverb hum. True but it appears as...
by wally01
Thu Mar 30, 2017 7:13 pm
Forum: Music Tech DIY
Topic: TTSH Ver.3 (rev.8) General build thread
Replies: 2031
Views: 118664

Hum in the reverb section can be caused by poor cables or a bad/missing ground connection to the reverb spring. Classic reverb hum is difficult/impossible to produce in V3 due to fact that ground is isolated on reverb return. You need a ground loop path to produce reverb hum. True but it appears as...
by wally01
Thu Mar 30, 2017 7:06 pm
Forum: Music Tech DIY
Topic: TTSH Ver.3 (rev.8) General build thread
Replies: 2031
Views: 118664

OK. So what happens if you swap the left and right connectors that go to the amps on the synth? Does the hum problem stay on the left channel? If so then you may have an amp problem. If it goes to the right then check speaker/headphone jack wiring. What happens when the RCA cables are connected to t...
by wally01
Thu Mar 30, 2017 3:15 pm
Forum: Music Tech DIY
Topic: TTSH Ver.3 (rev.8) General build thread
Replies: 2031
Views: 118664

Still couldn't fix the hum problem. I used gnd from gate and trigger for left, right speaker and for the headphone jack separately. It is worst on left headphone but also recognizable on the left speaker (slightly on both) and even more when reverb is fully up (without rca cables connected). RCAs a...
by wally01
Thu Mar 30, 2017 2:12 pm
Forum: Music Tech DIY
Topic: TTSH Ver.3 (rev.8) General build thread
Replies: 2031
Views: 118664

Still couldn't fix the hum problem. I used gnd from gate and trigger for left, right speaker and for the headphone jack separately. It is worst on left headphone but also recognizable on the left speaker (slightly on both) and even more when reverb is fully up (without rca cables connected). RCAs a...
by wally01
Thu Mar 30, 2017 2:01 pm
Forum: Music Tech DIY
Topic: TTSH Ver.3 (rev.8) General build thread
Replies: 2031
Views: 118664

Those readings actually don't sound too bad. You are in good shape here. I would only be concerned if you saw resistance close to, or at zero. Thanks so much guys! I have connected the PSU and indeed it seems to work! I am short of all the sliders for CV control but at least the oscillators and the...
by wally01
Wed Mar 29, 2017 1:44 pm
Forum: Music Tech DIY
Topic: TTSH Ver.3 (rev.8) General build thread
Replies: 2031
Views: 118664

I have soldered nearly all the parts on the board so I thought I am ready for some tests. Before I connected the PSU I measured the power bus for continuity on the big board and oh dear, beep, beep between V+ and 0 and also between V- and 0 and also between V+ and V- :sadbanana: There is a resistan...
by wally01
Sun Mar 19, 2017 1:51 pm
Forum: Music Tech DIY
Topic: TTSH Ver.3 (rev.8) General build thread
Replies: 2031
Views: 118664

Did even more experimenting with my sync/timestretch/weird issue. Again, it's when you stack two or more VCOs in the same frequency on top of each other and raise the speakers, raise the VCOs into the mixer, etc. The beat frequencies, when slow, then latch onto each other and completely freeze. It ...

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