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TZFM SAW VCO
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sonicwarrior



Joined: Dec 22, 2005
Posts: 227
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PostPosted: Tue Nov 08, 2011 2:16 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks a lot. Smile
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peng



Joined: Feb 23, 2006
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PostPosted: Wed Feb 15, 2012 9:32 am    Post subject: Reply with quote  Mark this post and the followings unread

I have a Teezer built up and wired up but it is not working properly.
It does oscillate but it is sub audio oscillation and it does not respond to any frequency inputs or controls. I can see sine, tri, and saw shapes on the scope.
The CV summer is working.
My guess at this time is something having to do with the 3280 IC.

Ian, I would love for you to hold my hand while I try and fix it.
Scope is fired up and everything is on the table ready to go.
Do you have any ideas right off the bat?
Any measurements you need I can get within minutes of posting.
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frijitz



Joined: May 04, 2007
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Location: NM USA
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PostPosted: Wed Feb 15, 2012 6:45 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi Peng --

First thing to check is that every chip is getting the correct PS voltage.

Ian
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peng



Joined: Feb 23, 2006
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PostPosted: Wed Feb 15, 2012 7:30 pm    Post subject: Reply with quote  Mark this post and the followings unread

Ian, thanks for responding.
This is a bridechamber MOTM kit build and I'm running on +/-15V.
All chips are getting power and the regulated voltage lines come out as:
+/-5V line = +4.9V/-4.92V
+/-7V line = +6.84V/-7.02V
+/-9V line = +8.86V/-9.01V
+/15V = +/-15.00V

Nothing is hot either.
I have triple checked components, placement, IC orientation, and wiring.
I still could have missed something (in fact I hope I did! It would be an easy fix then) but I checked for the common errors I make. Solder joints look good, too. Traces for the CV summer have good continuity.

Thanks,
Phil
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frijitz



Joined: May 04, 2007
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PostPosted: Thu Feb 16, 2012 6:25 am    Post subject: Reply with quote  Mark this post and the followings unread

peng wrote:
All chips are getting power

OK, next please look at the output of A3 (p6) and make sure it is swinging +/- 5 V as the "init" pot is varied.

Ian
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peng



Joined: Feb 23, 2006
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PostPosted: Sun Feb 19, 2012 12:39 am    Post subject: Reply with quote  Mark this post and the followings unread

I get the +/-5V swing from A3 output.
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peng



Joined: Feb 23, 2006
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PostPosted: Sun Feb 19, 2012 1:21 am    Post subject: Reply with quote  Mark this post and the followings unread

I pulled up one end of R23 (6.8K) and checked the current to pin 3 of U1a.
With both the coarse and fine controls full CW I get 0.87mA.
Adjusting the coarse and fine changes the current so those controls seem to function properly. If that is the correct current maximum, then it seems A1a and b, A3, and the matched pair are OK. The circuit still oscillates (albeit, at LFO rate) but doesn't change speed with coarse, fine, or initial freq pot changes.

Do you think this may be a bad 3280?
I'm reluctant to pull it because it is soldered in and I don't have another. I want to get your opinion or other steps to check before I do so.

Thanks!
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frijitz



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PostPosted: Sun Feb 19, 2012 10:58 am    Post subject: Reply with quote  Mark this post and the followings unread

peng wrote:
I pulled up one end of R23 (6.8K) and checked the current to pin 3 of U1a.
With both the coarse and fine controls full CW I get 0.87mA.
Adjusting the coarse and fine changes the current so those controls seem to function properly. If that is the correct current maximum, then it seems A1a and b, A3, and the matched pair are OK. The circuit still oscillates (albeit, at LFO rate) but doesn't change speed with coarse, fine, or initial freq pot changes.

Good sleuthing. Just offhand, I believe something a bit under 1 mA is correct.

Quote:
Do you think this may be a bad 3280?
I'm reluctant to pull it because it is soldered in and I don't have another. I want to get your opinion or other steps to check before I do so.

Could be the 3280. I'd also suspect the VN0104 pair -- they are very sensitive to static and heat and easy to damage.

If you want to check the 3280: Carefully unsolder or clip the output pin (p.13). (I'd just clip it.) Connect p.13 to ground through a resistor, say 6.8k (Just tack solder it directly to the pin or use a fine wire soldered to the pin). You should be able to get +/- 5 V (or so) with freq controls at max. Carefully redo the connection to the board if the output is OK.

Ian
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decaying.sine



Joined: Aug 31, 2009
Posts: 92
Location: New Haven, CT, USA

PostPosted: Sun Feb 19, 2012 5:04 pm    Post subject: Reply with quote  Mark this post and the followings unread

Phil, if you find out that it is your 3280 that is bad, email me. I bought 10 from Mr. Patchell for his vocal filter and only need 9 I believe. I'll mail it to you quick.

Brian
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Mongo1



Joined: Aug 11, 2011
Posts: 411
Location: Raleigh NC

PostPosted: Sun Feb 19, 2012 5:19 pm    Post subject: Reply with quote  Mark this post and the followings unread

This sounds unfortunately very familiar - When I built my bridechamber kit I had similar symptoms. I finally got the module to work somehow (I never did quite understand what happened). It worked for a few months, and then started getting progressively more unstable. About a week ago it died again.

It seems like there may be a bad connection, but I've gone over it 1000 times trying to find it - no luck.

One weird symptom I've seen - I can touch various spots on the back of the board around the core, and it will suddenly start working for a while. I have no idea why.

One thing I'm going to try is to replace the the film cap in the oscillator core. It's possible I overheated it during the assembly process.

Gary
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Mongo1



Joined: Aug 11, 2011
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Location: Raleigh NC

PostPosted: Thu Feb 23, 2012 2:04 pm    Post subject: Reply with quote  Mark this post and the followings unread

I have one technical question - I've been looking at the schematic and I don't understand the way Q4 and Q5 are arranged. I've seen two trannies used in parallel to increase current capacity, but why are these two used in series? The data sheet indicates they can handle 40V, so I'm at a loss.

Anybody have an opinion?

Thanks
Gary
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frijitz



Joined: May 04, 2007
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PostPosted: Thu Feb 23, 2012 3:56 pm    Post subject: Reply with quote  Mark this post and the followings unread

Mongo1 wrote:
I have one technical question - I've been looking at the schematic and I don't understand the way Q4 and Q5 are arranged. I've seen two trannies used in parallel to increase current capacity, but why are these two used in series? The data sheet indicates they can handle 40V, so I'm at a loss.


The FETs have input protection diodes, so you need two in series for bipolar operation. Totally standard.

Ian
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Mongo1



Joined: Aug 11, 2011
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PostPosted: Thu Feb 23, 2012 4:45 pm    Post subject: Reply with quote  Mark this post and the followings unread

Ah! Thanks. Its nice to learn something new.
Gary
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Mongo1



Joined: Aug 11, 2011
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PostPosted: Sun Mar 04, 2012 3:54 pm    Post subject: Reply with quote  Mark this post and the followings unread

Okay! So I finally got this thing working again this weekend. As I expected, the problem was C4 - Those poly caps are so sensitive to heat. Replaced that, and it works better than ever now.

AND I got my chaotica built and running - sounds amazing...

Gary
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frijitz



Joined: May 04, 2007
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PostPosted: Mon Mar 05, 2012 5:48 am    Post subject: Reply with quote  Mark this post and the followings unread

Mongo1 wrote:
Okay! So I finally got this thing working again this weekend. As I expected, the problem was C4 - Those poly caps are so sensitive to heat.

Glad to hear it's working for you. Yeah, it's easy to melt the poly caps. Also, sometimes you just get bad ones. Best to go with the NP0/C0G ceramics nowadays.

Ian
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Mongo1



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PostPosted: Mon Mar 05, 2012 1:41 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
Best to go with the NP0/C0G ceramics nowadays


Wow - I didn't realize those were an acceptable substitute- thanks for the tip!

Gary
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peng



Joined: Feb 23, 2006
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Location: Chicago
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PostPosted: Mon Mar 19, 2012 12:33 pm    Post subject: Reply with quote  Mark this post and the followings unread

Wow!
It works!!!

Turns out it was a bad 3280.
I feel kinda dumb about this because it should have been caught before it was ever installed.
I have long been suspect of every 3280 and normally test these out on the breadboard (simple VCA circuit) to confirm they are within spec and/or work.
But this one was an Intersil brand and those have always checked out OK so I skipped my normal routine.
Bad move on my part.

Regardless, it works now and I feel very happy!!!

p.
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Mongo1



Joined: Aug 11, 2011
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PostPosted: Mon Mar 19, 2012 1:01 pm    Post subject: Reply with quote  Mark this post and the followings unread

That's great! Glad you got it working.

BTW - if it makes you feel better, yesterday I spent some time trying to figure out why 1 of the 3 clock dividers on my new Yusynth board wasn't working. Sometimes it had no output - other times the output was the same as the input. After some head scratching I pulled out my scope and followed the clock line into the suspect chip - no clock!

I pulled the board and waddya know - not a single molecule of solder on that one pin. I completely skipped it during assembly. AND during the careful visual inspection I always make before attaching the board to the bracket.

So - at least you have an excuse - a bad chip. I was just stoopid.

head banging monitor

Anyway, glad it's working for you. It really kicks ass.....

Gary
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echoer



Joined: Dec 10, 2009
Posts: 40
Location: lawrence, ks

PostPosted: Tue May 08, 2012 2:17 am    Post subject: Reply with quote  Mark this post and the followings unread

just finished wiring.

not working Sad

Pretty sure my problem is the 3280 because it is HOT to the touch. Not exactly sure what the voltages should be on each pin as I'm not too familiar with OTAs, so I can't tell what's wrong. Checked adjacent pins and there are no shorts.

I am running on +/- 15V and used http://modularsynthesis.com/bridechamber/tzfm/tzfm.htm modifications.

I did try inserting another 3280 as I have the chip socketed and probably fried that one as well...ugghgh. Hopefully these chips can handle some heat. If someone could take some pin readings off their working module that would be awesome.

Any help in getting this straightened out would be much appreciated. I have a cool Dual Teezer design, and I can't even get the first of the two to work yet1

This is such a great project I can't wait to get it going. Thanks in advance for any support.

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echoer



Joined: Dec 10, 2009
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Location: lawrence, ks

PostPosted: Fri May 18, 2012 8:46 am    Post subject: Reply with quote  Mark this post and the followings unread

I am guessing pin out voltages were in a previous post somewhere? I'll scroll through the pages again and have a look.

I've built two Threelers and they are incredible, and no doubt this VCO lives up to the hype. Can't wait to get them up a blooping.

Fritz you are an excellent Electronics Artist. Thanks for sharing your great work.

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sduck



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PostPosted: Sun Aug 26, 2012 8:24 pm    Post subject: Reply with quote  Mark this post and the followings unread

What voltages is the 3280 supposed to be getting? Mine is getting around +-11.45v, and is getting really hot. No output. This is the second one I've built, and I was super meticulous about parts and such, but obviously could have screwed up something.

edit - upon rechecking, pin 4 is getting -11.5, pin 14 is getting 11.5, but pin 11 is getting 15v - but it shouldn't be? Why would that line be that much higher?
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davebr



Joined: Jun 09, 2007
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PostPosted: Sun Aug 26, 2012 9:32 pm    Post subject: Reply with quote  Mark this post and the followings unread

sduck wrote:
What voltages is the 3280 supposed to be getting? Mine is getting around +-11.45v, and is getting really hot. No output. This is the second one I've built, and I was super meticulous about parts and such, but obviously could have screwed up something.

edit - upon rechecking, pin 4 is getting -11.5, pin 14 is getting 11.5, but pin 11 is getting 15v - but it shouldn't be? Why would that line be that much higher?

If you used my mods, you would have replaced D203 and D204 with 8.2V zeners. 15 - 8.2 = 6.80 volts on the power supply pins. 11.5 would indicate either 3.5V zeners or perhaps a short somewhere. I have no layout to be able to trace the runs, but pin 14 and pin 11 should be connected together I would think. Pull the OTA and measure the voltage. The OTA is spec'd to +/-15 volts so that shouldn't be an issue. If it is getting hot then I would suspect a solder bridge somewhere. I would verify all the voltages on the OTA socket with the part removed. Feel free to email me if you want specific help.

One final thought ... 3280's are a bit rare so have you ruled out counterfeit parts?

Dave
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sduck



Joined: Dec 16, 2007
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PostPosted: Sun Aug 26, 2012 10:29 pm    Post subject: Reply with quote  Mark this post and the followings unread

Sorry, should have taken a break before posting. A bit frazzled perhaps.

I used Ian's 15v mod method, with the 6 extra zeners. According to the layout I have pins 11 and 14 of the 3280 don't connect, although they're supposed to be getting the same voltage according to Ian's list earlier in this thread - I think, running on tired memory here.

Hope to get this sorted out in the next few days, if I can find time.

Oh, and I got the 3280 from bridechamber - have no way of knowing whether it's real or not.

davebr wrote:
sduck wrote:
What voltages is the 3280 supposed to be getting? Mine is getting around +-11.45v, and is getting really hot. No output. This is the second one I've built, and I was super meticulous about parts and such, but obviously could have screwed up something.

edit - upon rechecking, pin 4 is getting -11.5, pin 14 is getting 11.5, but pin 11 is getting 15v - but it shouldn't be? Why would that line be that much higher?

If you used my mods, you would have replaced D203 and D204 with 8.2V zeners. 15 - 8.2 = 6.80 volts on the power supply pins. 11.5 would indicate either 3.5V zeners or perhaps a short somewhere. I have no layout to be able to trace the runs, but pin 14 and pin 11 should be connected together I would think. Pull the OTA and measure the voltage. The OTA is spec'd to +/-15 volts so that shouldn't be an issue. If it is getting hot then I would suspect a solder bridge somewhere. I would verify all the voltages on the OTA socket with the part removed. Feel free to email me if you want specific help.

One final thought ... 3280's are a bit rare so have you ruled out counterfeit parts?

Dave
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davebr



Joined: Jun 09, 2007
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PostPosted: Sun Aug 26, 2012 11:42 pm    Post subject: Reply with quote  Mark this post and the followings unread

sduck wrote:
I used Ian's 15v mod method, with the 6 extra zeners. According to the layout I have pins 11 and 14 of the 3280 don't connect, although they're supposed to be getting the same voltage according to Ian's list earlier in this thread - I think, running on tired memory here.

Hope to get this sorted out in the next few days, if I can find time.

I found the layout information. There are clues in the schematic. Pin 14 is fed from B201 and pin 11 is fed from B205. You can see the U1a and U1b listed in the schematics by these parts. You replaced B201 and B205 with zeners but pin 11 is getting the full 15V. Measure the voltage on each side of B205. Something is wrong with that zener mod.

That would give you 3 more volts on that leg of the power distribution but I don't see anything obvious in the schematic that would be over stressed by this voltage. I would suggest you measure all the voltage sources: +/-12, +/-9, +/-7 and +/-5. The +9 is probably at +12 if B205 is at +15.

I would measure all the pins with the OTA removed. Something is causing it to heat up. As always, I suggest reviewing every solder joint with a magnifying glass looking for any unsoldered or bridged pins. Good luck!

Dave
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sduck



Joined: Dec 16, 2007
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PostPosted: Mon Aug 27, 2012 7:39 am    Post subject: Reply with quote  Mark this post and the followings unread

Both diodes - the ones in the place of B205 and B206 - seem to be shot - they're acting like wires, not stepping down the voltage at all. The other ones are fine. Strange. That's all I've got time for this morning - I'll replace them and see where I'm at later.
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