TZFM SAW VCO

Sound · Joined: Jun 06, 2006 Posts: 842 Audio files: 1

The pulse that I had before the ramp starts disappeared increasing R36 to 1.5K.
Ian helped and supported me until the solution was founded via PM.
So thanks again, Ian.

My first impression is that the Teezer is a very great oscillator.
You can achieve a lot of different sounds. Its amazing the fact that you have control over the linear control. I recommend the big know suggested by Ian, or add a FINE control like I did. There are a lot of details during its route.
Very easy to tune it, over all the range.
The sine wave is very very clean.
Very wide range, since LFO to ultrasonic range.

I have some work still, calibrate again and investigate.
About my modifications, the extra sine output just wired, has the little inconvenience that for example if your are sending the sine to the audio output and with other jack connected at the sine copy you touch ground, the sound obviously is cut. So I will go for a voltage follower. Is a very useful mod for reciprocal modulation within the two Teezer.
About the FMSUM output, its very easy to implement, due the extra R14 pad in the PCB, you have the two points to tap free. But I'm thinking to do it internal, so send the FMSUM of the first Teezer to second Teezer via an switched jack or an switch. I will lose a little utility but I will achieve a more clean front panel.
I think its important this feature because its easier to make that the two Teezer works in proportional frequency.
Also In the Exponential Fine potentiometer I put R4=1M it means that it has control over an octave, that i think is useful. In final front panel I will divide the layout in 12 lines instead of 10. That will be approx semitones.

A lot of sounds in one oscillator. A lot of colors. I sincerely recommend it.

Very Happy

frijitz · Posted: Wed Dec 02, 2009 12:45 am Post subject:

Just for the record, Oscar's problem with the spurious pulses was due to a wiring error (R27 not connected).

Very Happy

Ian

Sound · Joined: Jun 06, 2006 Posts: 842 Audio files: 1

R27 was correctly connected.

What I pm'ed you referring R27 is talking about the Teezer in the solder-less breadboard.

In the solder-less breadboard now is correctly working, think that I never doubted. For the record.

Anyway, whatever thing is happening at my teezers I will found it and I will fix it.

Regards. Sad

frijitz · Posted: Wed Dec 02, 2009 1:23 pm Post subject:

Sound · Joined: Jun 06, 2006 Posts: 842 Audio files: 1

I have two dual Teezer built in a dual unit as you already know and one in a solder-less breadboard as I said you.

Thanks!

sduck · Posted: Mon Dec 07, 2009 8:49 pm Post subject:

Apparently my teezer is stillborn. Finished the last little bits of wiring, chip insertion, etc, and upon first power up - nothing. Not a peep.

Major troubleshooting will start tomorrow - I'm tired now, will miss things.

I used a parts kit from bridechamber, which had quite a few missing/wrong parts - I caught most of these, but may have had some slip by. My only question right now is - for the LM741's, can you sub UA741's? That's what was in the parts kit, so my presumption is yes.

frijitz · Posted: Mon Dec 07, 2009 11:56 pm Post subject:

sduck · Posted: Wed Dec 09, 2009 6:08 pm Post subject:

Ok, gotta get on this. I've been over the pcb and wiring with a fine toothed comb, and can't find any obvious problems. So I guess the first thing to do is make sure the right voltages are getting to the right places. I've got this board set up for 15v, as per the instructions in the docs, with the 6 zener diodes. I've checked the +-5v at the initial freq pot, and they're fine. Can you give me some places to check to make sure I've got the right voltages going? FWIW I'm pretty terrible at deciphering schematics in great detail, but can usually follow along, and have a good dmm and scope here.

Also if you want to do this via email instead of clogging up this thread, PM me about that.

frijitz · Posted: Wed Dec 09, 2009 7:17 pm Post subject:

sduck · Posted: Wed Dec 09, 2009 7:58 pm Post subject:

Thanks! I'll get on it. Forgive me if it isn't right away - things are getting a bit hectic here, but hopefully I can get on it Friday if not sooner.

sduck · Posted: Mon Dec 14, 2009 3:12 pm Post subject:

Ok, I checked all the supply voltages to the chips, and they're all working correctly according to your list.

I also checked the voltages coming out of the output jacks on a whim, and found a +5v coming out of the sine jack, and -5v coming out of the saw and tri jacks. This doesn't sound right - does it give you any ideas?

I don't really know where to proceed from here - so any ideas are welcome. My usual procedure at this point is to replace all the chips, but in this case there's a lot of them, and some are hard to get, so that may not be the best way to go. I have had problems with static electricity recently - after years of no problems, I've had chips die in 2 modules recently, although those both may have been in a related storm incident. I'm pretty good about esd procedures while building, although who knows what happens before I get the chips.

frijitz · Posted: Mon Dec 14, 2009 3:30 pm Post subject:

sduck · Posted: Mon Dec 14, 2009 4:44 pm Post subject:

Uh-oh, that's not at all what I'm getting. At 0 on the coarse tune knob, I'm getting about +5v (depending on where the fine tune knob is set), and as I turn it up it quickly drops to about +.7v between about 2-3 on the knob (I have a 10-turn pot, so I'm guessing) and stays there the rest of the knob travel. So something's broke - which is it?

frijitz · Posted: Mon Dec 14, 2009 9:53 pm Post subject:

sduck · Posted: Tue Dec 15, 2009 7:18 am Post subject:

Ok - I'm really hoping the Q1Q2 is OK - I'd hate to have to replace it!

The inital pot seems to be working - I've got the +5 to -5 (from A3-6) swinging from low to high - is that the right direction? I thought I'd worked out how these 10 turn pot wiring worked, but it's pretty easy to get it wrong.

frijitz · Posted: Tue Dec 15, 2009 8:11 am Post subject:

sduck · Posted: Tue Dec 15, 2009 8:31 am Post subject:

Hi again, and thanks for leading me through this!

A2-6 is dead - 0 volts. At any setting of the knobs.

U2 - pin 2 is +2.2v, pin 3 is +2.75, pin 7 is -6.65.
U3 - pin 2 is -2.75, pin 3 is -2.18, pin 7 is -6.67v.
These readings were with the init pot at 0. Readings are the same at 10.

I'm guessing the O volts coming out of A2-6 is a bad thing, no?

frijitz · Posted: Tue Dec 15, 2009 12:50 pm Post subject:

sduck · Posted: Tue Dec 15, 2009 1:40 pm Post subject:

I'm reading +10.24v at that node. What does all this mean?

frijitz · Posted: Tue Dec 15, 2009 2:24 pm Post subject:

sduck · Posted: Tue Dec 15, 2009 2:37 pm Post subject:

Hmmm, it looks like the Q3 is in right - flat side corresponds to the silkscreened flat side.

I'm getting 0.73v at the Q3, D3, R27 node,

and 10.9v at A9-7.

frijitz · Posted: Tue Dec 15, 2009 3:00 pm Post subject:

sduck · Posted: Tue Dec 15, 2009 3:42 pm Post subject:

You're more than welcome!

A9 voltages -

1- 11.35
2- 3.8v with sync level pot at 0, changing to 0v with pot at 10
3- 4.84
5- 2.3
6- 0.01
7- 10.9

Thanks!

frijitz · Posted: Tue Dec 15, 2009 4:47 pm Post subject:

sduck · Posted: Tue Dec 15, 2009 8:15 pm Post subject:

Yay! That was it! For some reason, R133 had a 22 ohm resistor instead of a 22K one. My aging eyes have enough trouble reading color codes that I don't bother, instead just reading each resistor with my DMM - and apparently I missed the fact that the tiny symbol at the end was the wrong one. An easy fix.

What a 22 ohm resistor was doing in the parts kit I bought is another question. Not one I'm very concerned about at this point though.

And yes, I had the 2 10-turn pots wired backwards, but again it was an easy fix.

I'll post some pics of the finished product tomorrow maybe.

Thanks so much for working me through this Ian - you're the best!