Meatball not filtering. IC voltages inside.

Started by Jack, June 15, 2007, 04:42:00 AM

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Jack

I perfed a McMeat based exactly on Joep's Layout, substituting the vactrols for LDRs and LEDs. The wiring done according to the pisotones diagrams.
LDRs:
The "Large" ones from Jaycar.
Light Dependent Resistor (LDR) - 8.5 x 10.1mm

Cadmium sulphide (CdS) light dependent resistor cell.
- Dark resistance: 0.5M ohm min.
- Light resistance: 2.8K ohm min 8.4K ohm max.
- Max dissipation: 100mW
- Rise time: (0-63%) 50mS
- Decay time: (100 - 37%) 40mS

Now, the envelope detection section works well, everything as it should, knobs, switches etc.
The filter section doesn't.
Signal does pass through. For some "Modes" there is some loss in level, when the "blend" is set to just filtered, no dry signal.
In one "Mode" ,not band pass, there is some crackling, that corresponds to the LED brightness.
Poking around occasionally makes squealling sounds if that helps.
There was no effects loop. The trace were joined and a wire sent to intensity.
Seeing as the LM1458 is working fine, here are the tl074 pin voltages, guitar plugged in, no signal.
Across power supply terminals: 8.8v
Pin: Voltage, V.
1 : 1.6
2 : 4.5
3 : 4
4 : 8.2
5 : 4
6 : .05
7 : 3.9
8 : 7.2
9 : 3.9
10:4
11:.003
12:3.5
13:4
14:4

I assume it's a wiring mistake, but any insight would be great, before I check it for the millionth time.
Thanks.

Bernardduur

Am learning something new every day here

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Jack

#2
Yes.

Also here's the schematic: http://home.planet.nl/~remke063/mcmeat.pdf
I didn't have any 22n caps so left off C19, but it looks like it's just filtering.

Bernardduur

OK; I used that one too!

You play with the CdS in darkness???
Am learning something new every day here

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