ISP Decimator II

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ISP Decimator II

Postby caspercody » 15 Dec 2018, 07:02

I found a schematic for this here:

http://the7line.clan.su/publ/diystompbo ... e/2-1-0-35

I created a vero board using Sabrotone's Decimator one layout. I have not built it yet, and if anyone sees anything that needs to be changed please let me know

Also, if you have anything for the G string portion, please let me know?

Thanks
Rob
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Re: ISP Decimator II

Postby caspercody » 16 Dec 2018, 05:37

I found some mistakes in my last vero, here is the corrected one.

I colored the +9 volts with red jumpers, ground with green jumpers, 1/2 voltage with blue jumpers, and jumpers are in white.

Also attached is a BOM. The BOM is missing the 10K B Threshold pot.
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Re: ISP Decimator II

Postby caspercody » 26 Dec 2018, 03:53

I finally got around to put this together, I get sound out of it, but it is distorted. More gated fuzz sounding, and the Threshold pot does nothing. I took voltage readings, supplied voltage is at 9.48.

voltages 1.pdf


I have attached the schematic where I wrote in the IC numbers and pins that correspond to the vero board. I circled the parts that are different then the first version of the Decimator. Some of the values are different then the first one, but for the most part, the rest of the schematic is the same. The only difference that I think about is that pin 4 on 2181 is connected to pin 2 in the first version. In this version there is no connection to pin 4?

I just a wire coming off of the output and worked my way into the circuit. I get clean sound up to the capacitor side of R6, but no sound when I touch pin 1 of the 2181 chip. If I connect to pin 7 of IC 2, I get a nice sounding distortion. If I connect to pin 3 of IC 2, I get no sound.

Any help on this would be appreciated! I do not know what to really think about those voltage readings. I also took readings from the first version I made:

voltages 2.pdf


Thanks
Rob
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Re: ISP Decimator II

Postby EddieTavares » 27 Dec 2018, 02:53

Great job caspercody

I cloned the older version, something that looks strange for me in the schematic below is that the gate of the fet 2N5484 (pin 3) should be connected to R30 and the remaining terminal to r22 as the earlier decimator, if there is a little noise when you s a diode between r30 and gate and a small cap to the ground would avoid it. I know that you didn't implement that part of the circuit, I did because I like the idea to have buffers before and after all my noisy pedals.
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Re: ISP Decimator II

Postby caspercody » 28 Dec 2018, 01:34

Thanks Eddie

But I am kind of stuck trying to get this to work.

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Re: ISP Decimator II

Postby caspercody » 30 Dec 2018, 06:18

Okay, I believe this vero works. My build does work now, when I turn the threshold pot it does eliminate noise.

However, on my build I do not have a clean tone when it is activated. I do not know if I have a bad component somewhere or wrong value. I did take my Decimator version one apart and using a probe when both sound the same at different points in the circuit. Meaning they both have a distorted tone going through much of the circuit.

I do now have different voltage readings on IC number 2, and 3. Also on the 5401 transistor.
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Re: ISP Decimator II

Postby caspercody » 28 Jan 2019, 22:17

I have made a mini board for the G string and wired it into my Version 1 Decimator and it works.

I am still stuck with the Version 2 Decimator, it works and it does eliminate noise. But it still is not a clean tone, it has a little distortion to it. I am not sure if I have a bad component or if the schematic is missing something. I have checked it out for shorts with a DMM, and a magnifying glass and see none. The voltage readings look close to the readings I get on the Version 1 Decimator. I am stuck now on how to figure this out. I know the version 1 Decimator does have a distorted sound and at the end of the circuit it is cleaned up.

I am hoping someone else will bread board or build it to see if they get the same results.

Thanks
Rob
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