Hey, I've built 2 of these correctly, this last ones got me lost.
http://2.bp.blogspot.com/-8z8Xoss8H2k/U_4wBvUaVfI/AAAAAAAAIh4/dHxqBiq8lJM/s1600/Wampler%2BEcstasy%2BRev%2B2.png
When I plug in the 9V, the over drive is there for 2 seconds, then slow goes into a fizzle and after 7 seconds, theres no more sound.
Is that a capacitor issue? I've tried 2 different chips, a Jrc4580 and the 1458, same deal. I used a ceramic for the 1uf cap on the top right by the way.
And I also didn't solder the switch, because I don't require the other 2 clipping modes. It's OK the completely leave out the switch right, since in the middle position, no connections are made.
Thanks
Could be a bias issue (?), or a couple of other things... check ALL your connections for 'cold solder' joints. Go back over parts placement 100 times, as well as any cuts you had to make in the tracks.
Do you have a DMM (meter)? If so, can you post your pin voltages please?
Quote from: Esppse on March 12, 2019, 07:22:30 PM
It's OK the completely leave out the switch right, since in the middle position, no connections are made.
Difficult to see without a schematic but since positions 2 and 5 are connected on the switch (which is the 'off' position i think you'd still need to jumper 'gain 1&2' to to 'switch 5' on the board.
I dunno, i've had a few ha :icon_rolleyes:
OK here are the voltages, just got a chance to check.
1 = 9.14
2 = 4.79
3 = 0.84
4 = 0.0
5 = 9.78
6 = 8.81
7 = 8.75
8 = 8.44
Is there anything odd with those numbers? I've been over my trace cuts and components over 12 times.
And I think the switch can be left out, 2 and 5 are not connected when in the middle position, it is an on off on switch. So it can be completely removed.
Yes, the voltages are wrong on the opamp.
You should see 9v on pin 8 and 0 on 4 (you're not bad here) but the other pins should be around mid voltage (4.5).
There are pairs of 100k resistors that "divide" the 9v into half voltage, and this mid voltage goes via 470k to the non-inverting inputs of the opamps (pins 3 and 5). When this is done (and nothing else is wrong) the other pins will go around the same voltage. Your meter may load things and give you a lower number, but it should be around mid voltage.
And the power voltage on pin 8 is actually lower than the voltage on other pins... People love to see pictures on this forum, even pictures of ugly vero board layouts with lots of mistakes....
Omg, I'm such an idiot, I forgot the right side of the chip is 8, 7, 6, 5 going downwards. It should be,
1 = 9.14
2 = 4.79
3 = 0.84
4 = 0.0
5 = 8.44
6 = 8.75
7 = 8.81
8 = 9.78
But that means I'm still not getting mid voltage on some pins
First of all, check for clear cut left to IC pin 8.. (absolute discontinuity between pins 1 & 8)
Check for +4.5V on the junction of 470k & 100k resistors (10th row, 5th & 6th hole..)
(a check for clear right lower cut should be a good idea, too..)
Ok,
There is no continuity between 1 and 8,
And I got 4.66 volts where you told me to check. So far so good?
(https://i.postimg.cc/qzfXzWc3/20190315-012831.jpg) (https://postimg.cc/qzfXzWc3)
(https://i.postimg.cc/vgfTj24J/20190315-012714.jpg) (https://postimg.cc/vgfTj24J)
(https://i.postimg.cc/tYwJzVCZ/20190315-012648.jpg) (https://postimg.cc/tYwJzVCZ)
Here are some pictures, it's actually on the same board as a cab sim I built, which I tested 100% working.
Hmm, is there possibly anything else I could try?
Would defective 100pf caps cause this to not function properly? Also, the layout calls for a 25k tone pot, but I used a 20k trimmer. Does that have anything to do with the improper voltages? For the 7 seconds that the circuit works, all the pots work right.
I've been over my work so many times, I'd hate to give up on this because the cab simulator is tied to the same stripboard.
Are the 47k resistors actually 47k? They look like green/blue/black/red/brown which would be 56k.
There should be about 4.5V on pin 3 of the IC. This is supplied via a 470K resistor which connects to a voltage divider formed by two 100K resistors and a 10uF capacitor.
Take IC1 out and test the voltage on pin 3 of the IC socket. If it doesn't come up to at least 3.2V (this value allows for meter loading ) check the value of the 470K resistor and make certain that the copper track connected to pin 3 is not shorting to another track. Even a fine sliver of solder or copper can do this.
Quote from: aelling on March 17, 2019, 03:02:38 AM
Are the 47k resistors actually 47k? They look like green/blue/black/red/brown which would be 56k.
And also, the 470k resistors seem to be 560k.
The colour (color ) of the 1% resistor bodies make it difficult to read the value bands - particularly if those bands are lightly printed. So yes, the yellow bands really do look green (ish ) and the purple bands seem blue (ish ). I find it good practice to measure all resistors with a meter anyway just to be sure that they are the value I need.
It's hard to tell but on the photo of the copper side of the board it looks like there could be a short between pins 3 and 4 of the opamp next to the trace cuts.
Ahhh yessssss!!! Thank you so much for your help all. It was that pesky 470k resistor that leads to pin 3. Apparently one of the legs was broken from the resistor and made no connection. :D