Search found 183 matches

by Synthetech
Sat Apr 19, 2014 8:46 am
Forum: HELP!
Topic: TX7 RAM problems from botched expansion..
Replies: 5
Views: 1237

Re: TX7 RAM problems from botched expansion..

Been learning some more about this beast as I twiddle with it more. 1st of all, I've had quite a blast tweaking out some voices and it sounds just as a DX7 should. Just a bit of clipping at high volumes.. lowering the volume down a couple notches fixes that problem. The highs are angelic, the lows a...
by Synthetech
Fri Apr 18, 2014 8:04 pm
Forum: HELP!
Topic: TX7 RAM problems from botched expansion..
Replies: 5
Views: 1237

Re: TX7 RAM problems from botched expansion..

Is this that one that was on eBay a couple weeks ago? Really glad I didn't hold out for that, now. Yes. It's not all that bad.. just needs a bit more TLC. Once I fix the RAM issue, it should make for a nice FM 6op synth. Did a mod move my thread? I coulda swore I posted this in the gear repair sect...
by Synthetech
Fri Apr 18, 2014 6:15 pm
Forum: HELP!
Topic: TX7 RAM problems from botched expansion..
Replies: 5
Views: 1237

TX7 RAM problems from botched expansion..

I picked this unit up with someone's idea of a memory expansion hacked into it. http://i62.tinypic.com/1gjeax.jpg http://i61.tinypic.com/34rgkf4.jpg http://i57.tinypic.com/2na8ylk.jpg http://i57.tinypic.com/2u4oaxh.jpg I powered it on, loaded some patches and only Pg's 1 & 15 would make any sound. 1...
by Synthetech
Thu Apr 17, 2014 4:02 pm
Forum: Gear Services & Other Goods
Topic: njm4558s op amp replacement?
Replies: 20
Views: 16123

Re: njm4558s op amp replacement?

Another really useful piece of test gear for situations like this is a capacitor decoupled audio signal probe. Quite easy to build, plenty of schematics on the web. do you have a link to an example? I searched and could not find much except this? http://www.talkingelectronics.com/projects/MiniBench...
by Synthetech
Thu Apr 17, 2014 3:59 am
Forum: Gear Services & Other Goods
Topic: njm4558s op amp replacement?
Replies: 20
Views: 16123

Re: njm4558s op amp replacement?

Thanks for all the suggestions. Yes, I have a Tektronix 466 scope to check voltage ripples and signals. I need to diagnose it the next few days when I can take the K3 to my shop with a proper test bench. Doing it at home on the kitchen table drives the wife nuts. Fortunately, the way Kawai built thi...
by Synthetech
Wed Apr 16, 2014 4:20 pm
Forum: Gear Services & Other Goods
Topic: njm4558s op amp replacement?
Replies: 20
Views: 16123

Re: njm4558s op amp replacement?

Dirt/ dust in the relay makes it switch intermittently. Sounds just like clipping. if the relay were faulty, then wouldnt it distort/clip at any volume setting? it only does it when I push the gain up past halfway. I'd assume if I bypass the relay and the relay was the fault, the clipping would cea...
by Synthetech
Tue Apr 15, 2014 3:32 am
Forum: Gear Services & Other Goods
Topic: njm4558s op amp replacement?
Replies: 20
Views: 16123

Re: njm4558s op amp replacement?

Thanks for your advice. What would I be looking for to indicate the relay is cause of clipping? I thought it was just a simple switch that passes audio to the outputs when the unit powers on.. according to the schematic clip I attached above. Yes, I have the service manual. It is here http://www.sou...
by Synthetech
Mon Apr 14, 2014 12:44 am
Forum: Gear Services & Other Goods
Topic: njm4558s op amp replacement?
Replies: 20
Views: 16123

Re: njm4558s op amp replacement?

Thanks for the reply. Yea.. I took a look at a Korg DW8000 filter board I have laying around and noticed it has a 4558s next to each filter chip. I only see the one relay. I doubt that is the source of my clipping. What are "feedback networks"? Am I looking for a bad electrolytic cap or caps? Any ot...
by Synthetech
Mon Apr 14, 2014 12:28 am
Forum: Gear Services & Other Goods
Topic: Basic Oscilloscope
Replies: 14
Views: 6693

Re: Basic Oscilloscope

That 466 was actually my 2nd attempt at procuring a scope. First time I tried to get one was a smaller Hitachi scope that was eBay listed without pics of it working.. ended up the seller did not pack it worth a sh!t and by the time it made it to my front porch, the CRT had metal/glass clinking aroun...
by Synthetech
Sun Apr 13, 2014 9:03 pm
Forum: Gear Services & Other Goods
Topic: Basic Oscilloscope
Replies: 14
Views: 6693

Re: Basic Oscilloscope

I recently picked up a Tektronix 466 analog storage 100MHz scope(late model) with the dm44 DMM built into the top of it for $150 shipped. http://i62.tinypic.com/or2f88.jpg I was shooting for a 465B, but this is even better since it has storage and a meter. Be very careful buying used on eBay. Only b...
by Synthetech
Sun Apr 13, 2014 6:34 pm
Forum: Gear Services & Other Goods
Topic: njm4558s op amp replacement?
Replies: 20
Views: 16123

njm4558s op amp replacement?

EDIT- Believe it or not, I found out the source of the K3 clipping was in fact my mixer aux send was overdriven for the channel the K3 was on. Doh! I have a Kawai K3 that begins to clip the audio output when volume is past half way. There are two 4558s's in the audiopath right before the line outpu...
by Synthetech
Wed Apr 09, 2014 5:20 pm
Forum: General Synthesizers
Topic: Korg NJM2069 VCF Filter Module?
Replies: 0
Views: 1567

Korg NJM2069 VCF Filter Module?

Anyone know of a filter module that uses the Korg NJM2069 VCF chip? The same IC used in Korg Poly 800's, DW8000's, DSS-1's and all their rack versions. I'm not sure if Paul Maddox's Zira does external input for VCF or not.. http://www.vacoloco.net/synths/zira/ it's the only currently sold synth item...
by Synthetech
Sat Apr 05, 2014 2:48 pm
Forum: General Synthesizers
Topic: Synth's Controls Affect On Oscope Waveforms
Replies: 18
Views: 3397

Re: Synth's Controls Affect On Oscope Waveforms

I put a scope on my Dx21 once and that was, by far, the most interesting looking read out I've ever seen. FM is incredibly animated. Back in the mid 90's, when laser diodes began to become cheap, I built a small laser light show using mirrored galvonometers driven by simple op amps. I hooked my DX1...
by Synthetech
Tue Apr 01, 2014 2:29 pm
Forum: General Synthesizers
Topic: space between Minibrute middle B and C
Replies: 11
Views: 1722

Re: space between Minibrute middle B and C

That gap is used for a tuning reference... blow through the gap and it should whistle a precise middle C note.
by Synthetech
Mon Mar 31, 2014 5:27 am
Forum: General Synthesizers
Topic: Any Korg EX 800 Users?
Replies: 21
Views: 4235

Re: Any Korg EX 800 Users?

Synthetech: Yeah, I suggested buying the Hawk kit four days ago. :roll: At least he got an opinion from someone who actually owns a Hawk800. Along with a description of some of the many features it adds to the lowly Poly800. I.don't understand the point of your recent post. Especially the :roll: Di...