Problems with the v8

gogmagog · Joined: Nov 08, 2008 Posts: 19 Location: Nashville, TN

So I've built the V8 simulator and, after some IC issues (I'll get to that later), it's up and running, sounding good. Except it won't "shift gears" when Auto is switched on.

I'm temporarily using a 100k pot for the speed input, no other CV input. Probing the inputs (11 & 9) to the 40106 shows that voltage seems to increase too slowly as I turn the speed pot; pin 11 only reaches 10 volts (upper threshold for 40106) when I've got the speed pot cranked all the way up to about 80 or 90k. By that time, sound has cut out all together for some reason (probably because the circuit was designed for only a 25k speed pot; sound stops at about 30k). Probing pins 8 & 10 shows 15v with speed turned down, 0v when the inputs reach 10v (at around 80-90kohm speed).

I've verified that all the components in the VCO section of the schematic are correct (except for the speed pot), but I have a feeling you guys are going to tell me to verify the whole board. I intend on doing that anyway, but it would be a lot easier if the picture of the PCB layout was more up-to-date on the site (wink-wink, nudge-nudge Wink

).

Earlier issue I mentioned was that I had tried to jury-rig a PSU out of two separate wallwarts rated at 12v before my actual PSU arrived (never again). Testing with that proved odd and eventually, I believe, shorted out my board, leaving practically all my ICs running hot to the touch. It eventually wouldn't make a sound. I'm pretty sure they were all shorted, so I replaced them all. Now I've got a Power One HBAA, works fine.

Any ideas?

gogmagog · Joined: Nov 08, 2008 Posts: 19 Location: Nashville, TN

Ok, after inspecting the PCB against the schematic, I've found what appears to be a contradiction. In the second section of the schematic (the timing generator), CLKI from the clock jack goes to a 15k resistor then to pin 5. Also, from pin 6 is a 10k to ground, and a 100k to +15v. However, on my PCB, the 15k and 10k resistors are switched. My PCB says Rev 1.2.

Can anybody else confirm this? Which way is supposed to be correct? Is anybody else having problems with this PCB rev?

I'll try switching the resistors today and see if that fixes my problem.

gogmagog · Joined: Nov 08, 2008 Posts: 19 Location: Nashville, TN

This is worth bumping after the holidays. Update is that switching the resistors didn't fix the automatic transmission; just made me increase the speed pot value.

Any ideas?

PHOBoS

This seems to be the only thread on the V8 Simulator module so I'll just add
my findings/problems to this one. I breadboarded it and can't really get
it working as I think it should.

First of all the VCO section: it kinda works but the range I get is really small.
I measured the voltage going into pin 9 of the 4046 (auto transmission off)
and with the speedpot I can vary this between 0... 12,3V (+/- 15V PSU),
which I think is correct. But the VCO allready stops working at 2,5V which
gives a max frequency of ± 5,3KHz. I tried replacing the 4n7 cap between
pins 6-7 with a larger one and that gave me a wider range (it can go
much slower) but it still stops at the same max frequency.

I've read in the info on the Thomas Henry X-4046 VCO that the range can
vary a lot depending on the chip used. So I suspect this might be the
problem. I ordered 4 CD4046's and received 1 Texas Instruments
CD4046BE and 3 HEF4046BP chips (which I suppose are Philips).
Since I had 3 of the HEF chipc I tested with those. The Texas Instruments
one does however have a slightly bigger range of 5.8KHz @ 4.3V.

The next part is the timing generator with the comparator and 4024 binary
counter. This section seems to work without any problems for me.

After that the signal is fed into the 'ringing oscillators'. These don't seem
to work for me aswell. That is, they work as a HPF but it's not the sound I
would expect. Also in the "Setting up the unit" section on the website it
states the following:

andrewF · Posted: Sat May 14, 2011 5:13 am Post subject:

I can at least confirm the design is fine and the module does sound like the most brutal V8, my last gig finished with 2 minutes of me just 'revving' the speed pot and trying to make the walls shake.

hate to say it but have a 3rd or 4th check over your board to make sure everything is correct.

This was one of my first CGS builds.......over 10 years ago? So can't remember much about it.
will pull the synth out and record some samples, if that helps??

PHOBoS · Posted: Sat May 14, 2011 5:36 am Post subject:

Thanks for confirming the design is correct. I am thinking about just
putting it on perf so I know that at least all the connections are correct.
(I sometimes have trouble with bad jumperleads). Samples would be
very helpful so I know if it sounds anything like what I have right now.
Another thng that would be helpfull if you could look at which 4046
you used (if that is not too much trouble). Since I'm pretty sure I have the
VCO wired correctly, it's just that the range is too small.

PHOBoS · Posted: Sat May 14, 2011 12:23 pm Post subject:

Ok, I've done some more tests. Started by isolating the VCO section, taking
out the auto transmission part and anything else attached to the 4046 chip
that wasn't needed. Tested the output (pin4) and it worked fine, no more
stopping but all the way up to 15,6KHz @ 12,3V Very Happy

so next I attached the second opamp, and tested the output, still fine.
Added the resistor and diode, and that's when it stopped working properly.
So I replaced the opamp the diode the resistor, measured if everything was
connected but couldn't get it working. I remembered reading somewhere (I
think it was another Ken Stone design) that people had problems with the
LM358 and replacing it with a TL072 solved it so I gave that a try and it
worked!

So that's where I am now, and I will add the rest of the circuit part for part.
Maybe replacing the LM358's in the ringing oscillators will also solve the
problem I had with those,..

-----------------------UPDATE----------------------
I have ringing oscillators! Very Happy

the problem wasn't the LM358's but there is a fault in the schematic which
I discovered by studying the PCB layout. There needs to be a 2M2 resistor
connected between the wiper of the trimpot and pin 2 of the LM358. I was
already wondering why they were in the parts list Wink

So it seems to be all working now, and it's extreme allright. I'm testing
with 2 PC speakers and even at a low volume it feels like I have a fan
blowing. I can only try to imagine what this would sound like on a PA
system. Twisted Evil

I also made one addition by adding pin 3 of the 4024 to the input of the
unused inverter and connecting it's output to an LED.

andrewF · Posted: Sat May 14, 2011 7:03 pm Post subject:

well spotted - the 2M2s are on the pcbs

-minus- · Joined: Oct 26, 2008 Posts: 787 Audio files: 13

I saw this project some time ago and wouldn't mind bread boarding it to see what it sounds like. Just wondering if anyone could upload a sound clip to hear it in action.

Thanks!

-minus- · Joined: Oct 26, 2008 Posts: 787 Audio files: 13

No sounds? Sad

"Please gentlemen, start your engines"

PHOBoS · Posted: Tue May 24, 2011 7:47 am Post subject:

andrewF · Posted: Tue May 24, 2011 4:19 pm Post subject:

-minus- · Joined: Oct 26, 2008 Posts: 787 Audio files: 13

Excellent! I had an 18 hour non-stop CGS breadboarding frenzy yesterday. The drum simulator is fun... but what I really REALLY like is the Chime Simulator! I might have to build two of these.

Looking forward to the sounds of your motors! All Ears

I need to get hold of a 4024...

EDIT: WAIT!! I have four 4024's here right now!!!! What was I thinking? I'm trying to get a driving license and a car at the moment (before I die). This circuit is going to sound great installed under the bonnet of a little 3 cylinder Daihatsu Charade Twisted Evil

andrewF · Posted: Tue May 24, 2011 11:21 pm Post subject:

18 hours, well i used to do that.....my eyes can't hack it anymore!

anyway V8 demo in the CGS samples thread -
http://electro-music.com/forum/topic-28043-25.html

-minus- · Joined: Oct 26, 2008 Posts: 787 Audio files: 13

Ha! My eyes have deteriorated somewhat too, quite noticeably over the past two or three years actually...

Thanks for posting the sounds! I really like the sounds at the start! I am going to have to breadboard this immediately. Looks like I'll be logging on for another long shift tonight! Laughing

-minus- · Joined: Oct 26, 2008 Posts: 787 Audio files: 13

Ah I finally got around to breadboarding this, only to have it not working. Then I read through this thread and saw what PHOBoS said about the 2M2 resistors! Once that was fixed it worked. Smile

I didn't have the appropriate trimmers so I used some pots for testing purposes. Spent a good hour or so tuning her up!

I was thinking the reason why this is a good V8 simulator is because of all the tuning. Trimmers would have enhanced the real V8 engine experience by introducing the screwdriver. I don't think my engine has as much grunt as yours andrewF.... you must have put many weekends work into that beast! Twisted Evil

andrewF · Posted: Sat May 28, 2011 9:53 am Post subject:

otherunicorn · Joined: May 11, 2008 Posts: 136 Location: Australia

Bah - no one told ME the resistors were missing from the diagram.

Cries. Wink

PHOBoS · Posted: Sun Jun 05, 2011 3:38 am Post subject:

otherunicorn · Joined: May 11, 2008 Posts: 136 Location: Australia