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Schmitz ms20 filter stripboard
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author Schmitz ms20 filter stripboard
Here is the working stripboard


I tried doing my first stripboard of a circuit. René Schmitz version of the ms-20 filter.

Surprisingly it does not work. I've gone over the diagram and my layout four times already and haven't been able to find any obvious mistake.

So now I'm wondering if its my layout, my soldering or the components that are to blame?

Old image deleted

Though it isn't obvious from the image, there are cuts in the traces under the ICs. And yes, that's a lot of wires, and it is not the tidiest of boards. It's peanut butter jelly time!

If the layout is fine, I'm sure others could find it useful.
Looking at your layout, it seems that the collectors of the transistors are connected to each other. It should be the emitters that are connected.

Thanks Flagada! I wasn't able to make out on the orientation from the original schematics.

However, it's still not working after I flipped them over. hmmm.....
what does 'it does not work' mean? no sound from the output? have you double checked your potentiometer wiring? it always add pin numbers to schematics that don't have them - makes troubleshooting a lot easier...
Maybe post a pic of your board from component and solder side too...

Two things that would benefit further builds for sure, when you have 2 trannies like here tied together on the emitter as in exponential converters, it's best first to match them for the closest Ube <2mV and keep them in thermal contact. Means glue their flat side together with heatsink paste.

I therefore place them as shown below


so the flat sides are together.
Also adding 10R resistors or ferrite beads before the 10uF caps where you inject your power to the board for decoupling is a good idea.
And one third thing, i would use decoupling caps per each IC too, simple 100nF ceramics would do the job here, but it's important to place them as close as possible to the IC always +UB to Gnd and -Ub to gnd.
For reference ( I think it starts from a slightly different schematic) this layout supposedly works.

Hey guys

Thanks for your responses. I continued to work on the board for a while after making the corrections you suggested above, but ended up throwing it in the graveyardbox.

I recent spend a good week troubleshooting a different board before realizing, that the cheap chinese CA3080s I bought were fakes.

So I pulled this one from the graveyard, attached a 13700 and lo and behold: It works!

Though it seems that the 10vpp signal from my oscillators is too much for it as the resonance disappears. When I send the signal from the oscillator through a vca/mixer and reduce the input level it squeals as it should.

Is there an easier way to solve this than making a small board with an input divider and an amp for the output?
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