TZFM SAW VCO

Luka · Joined: Jun 29, 2007 Posts: 1003 Location: Melb.

damn guess ill have to order some more of those

i actually have the fets placed in pin sockets
they were never soldered directly

frijitz · Posted: Sat Aug 28, 2010 2:42 am Post subject:

Luka · Joined: Jun 29, 2007 Posts: 1003 Location: Melb.

ian i swapped the mosfets from my working teezers into this one and it made no difference. what would be the next section to check?

frijitz · Posted: Sat Aug 28, 2010 6:09 pm Post subject:

Luka · Joined: Jun 29, 2007 Posts: 1003 Location: Melb.

getting back to this

d2-6 node is steady on -1.6v

lm311s are from same batch
i have some from another batch i can try and will do after posting this

When measuring A2 pin 6 there is no change when turning init or tune
here is a scope shot from that node

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Luka · Joined: Jun 29, 2007 Posts: 1003 Location: Melb.

well as smart as i thought i was by using pin connectors on the transistors they were my downfall in this case. the bass of the connector was shorting pin 2 to pin 3 of A2 ie to ground.

i just de-soldered the area and put it back together and it is up and running

a good way to finish a frustrating day

Funky40 · Posted: Mon Sep 13, 2010 1:30 am Post subject:

tomcat · Joined: Oct 14, 2005 Posts: 141 Location: earth

Terrafractyl · Joined: Sep 21, 2010 Posts: 13 Location: Melbourne

Hm I thought I already posted something here and it dissapeared... strange, ah well I'll try again!

So i've just finished putting together a Teezer, and on powering it up it works(all outputs), but only as long as I have the Initial Frequency pot above 12 o'clock.
As soon as it goes below, it kind of dies and I get nothing from any of the outputs until either I, power down, turn up the initial freq pot and power up the Teezer... or if I put a signal into the sync input it also kick starts the oscillations.
I'm using a kit from bridechamber and I used Dave Browns 15v resistor/diode mod.

All the IC's seem to be getting the correct power, + - 7v on U2 and 3 and +-9v on the A4
I checked the output of A3-6 and it swings from +5 to -5v fine.

I checked A2-6 output and it mesures +2.5 when the Oscillator is giving me sound and +5.0v when it has gone silent. Also the outputs all give me +5.0v when the oscillator is silent.
I checked the node where D2, D4, D6 etc join and when the Oscillator is working I get a -6.3v but when the Oscillator has gone silent I get a 3.5v

I only have software scope, but the saw has a very sharp downward peak just before the top of the waveform, and the sinewave is round at the top and triangular on the bottom.

So I have a feeling that it might be something to with either one of the LM311's or one of the VN0104's. but any help would be greatly appreciated.

Even without the Through zero, and with the problems it has, its sounds great already, I cant wait to get it working properly!

frijitz · Posted: Tue Jul 12, 2011 1:36 pm Post subject:

emdot_ambient · Joined: Nov 22, 2009 Posts: 667 Location: Frederick, MD

Terrafractyl · Joined: Sep 21, 2010 Posts: 13 Location: Melbourne

frijitz · Posted: Sun Jul 17, 2011 1:54 pm Post subject:

Terrafractyl · Joined: Sep 21, 2010 Posts: 13 Location: Melbourne

Ok so I've switched r133 and r132.

I double Checked D7, Its ok

A9-7 on the other hand seems a little odd. It is giving me -13.8V with nothing applied to the sync input. and -13.6V with a signal.

could this be a problem?

I'll go and try changing C8 right now also but I wont be able to switch out the LM311 for a few days.

thanks again for your help Ian

frijitz · Posted: Tue Jul 19, 2011 5:35 pm Post subject:

moellhoven · Joined: Jun 18, 2011 Posts: 15 Location: Germany

Just finished building my Teezer and fired it up.
At first glance everything seems to work fine.

When i started to calibrate the module i noticed that when the initial freq knob is turned full left or right the lowest freq i could tune in with the coarse knob is around 100hz.

Also when the coarse knob is turned fully down the VCO does not react to the signal from the V/OCT input anymore.

Please help Smile

frijitz · Posted: Mon Oct 03, 2011 2:55 pm Post subject:

moellhoven · Joined: Jun 18, 2011 Posts: 15 Location: Germany

moellhoven · Joined: Jun 18, 2011 Posts: 15 Location: Germany

I forgot to add that I used the Bridechamber kit for 15V.

frijitz · Posted: Tue Oct 04, 2011 10:09 am Post subject:

OK, it looks like the waveshapes are OK, just out of adjustment.

The problem with the frequency range is probably in the expo converter section: A1a, A1b and the transistor pair. There must be a wiring error or a bad component or a solder bridge or something in there somewhere.

I can't say much beyond that. If you want to measure the voltage at the A1a output (pin 1) as the coarse pot is varied from end to end, that might be helpful.

Very Happy

Ian

moellhoven · Joined: Jun 18, 2011 Posts: 15 Location: Germany

Thanks for pointing me into the right direction. Will do some checking on the weekend.

There is one thing i am not sure of i got it right. The kit came with an SSM2220 but without an TempCo.
From the documentation i figured it is missing and i added one of my spares to R14b. Is this OK or is this maybe the problem?

emdot_ambient · Joined: Nov 22, 2009 Posts: 667 Location: Frederick, MD