Regulator

[davidsrsb]

The low rbb types can show negative resistance, which is why we add base stopper resistors

 

[Stocker]

presto! oscillations ..

Jan Didden

LOL that's funny!

To get a proper regulator from that +/- 17 volts, you need 1x 78xx / 79xx series regulator IC, one or two capacitors, and maybe a resistor to obtain a non-standard voltage. < $10 if you know how to shop.

 

[argonrepublic]

I can't believe it. I got service manual today. They said copy centre takes acout ten days. 24 Hours ago I place my order, today I received an all original N.O.S service manual. It is really cool. It came off a real printing press! One page folds out into a 3 foot by 3 foot sheet.
IO immediately looked at the circuity in question and the voltage are 5 and -10. The other schematic shows +7.5 - 7.5 even though it is the same IC. I will try to scan tonight and maybe I can get things right with much needed and appreciated help.
Thanks
Joe

 

[argonrepublic]

I began to think I wasn't learning anything until I pulled a scanner from my junkpile and found a bad cap in it. Now I have a scanner. There are a lot of settings for scanning. I have never used one of these. What is the best scan format for B&W to place online?
Back to the synth....
I checked power distribution throughout. It all looks good. I got to my clock Oscillator. It is a TC4069UBP Hex inverter. My Hz meter says .1 kHz but I am not sure if it works properly. The OSC should provide 10kHz+/-1.
How can I test this IC?
I will try to scan and post

 

[pinkmouse]

Dpi depends on the resolution of the text you're scanning, 200dp is a good start, but scan in B&W, and save as GIF or PNG.

Please don't post the whole thing, or we might get into copyright issues.

 

[Nordic]

For pencil drawings and circuit scans, lineart format should give you the smallest files...

 

[argonrepublic]

I followed some tests last night and from my findings, the clock OSC output looked strange. I had no other choice than to go buy Oscilloscope. That's okay because I sold a friend 2 KB Electronics dual trace, a heathkit single trace and a lodestar function generator last year. He didn't need them anymore so here they are (Heathkit and 1 KB 4 sale). I am not experience with these besides playing around. I have a box of ancient amphenol BNC connectors. What can I use for cable to make probes?

 

[anatech]

Hi argonrepublic,
You need a X10 probe to keep the capacitive loading down. Just buy the probe(s) and be done with it.

The actual cable should be a flexible 52 ohm type. This is okay for a 1:1 probe.

-Chris

 

[argonrepublic]

Reg

Now that I have proper scematics, I need to move on to next phase of learning and repair.
I have attached diagram. Output of IC2, pin 8 should be 10 kHZ, -10 +10V sweep. I have an oscilloscope here have to get probes tomorrow. can I rig something up tonight to test this circuit? I have plenty of BNC connectors, Guitar cable and 75 Ohm coax.
Thanks

 

[anatech]

Hi argonrepublic,
It is possible to build a 10:1 probe. You need low capacitance 52 ohm cable, probe, some small cap in parallel with a series resistor (~9 Meg) and a trimmer cap for the calibration. Who knows what bandwidth you will end up with.

Not worth it for one. It's only a couple days until you get a real probe, if you put one together it will most likely "lie" to you.

-Chris