ISP Decimator (Sabro version)

[strassercaster]

Well mine isnt working. I had a wire touching another wire and got smoke no idea whats wrong with it now ha ha. I seem to have great voltages everything is between 3.8 and 5 ish only a few legs at around 1.8 volts idk if thats normal or not. Do you think a 30 turn trimmer could help? It goes from nothing to noise when adjusting. I wonder if smaller increments would help? What kind of trimmer were you using when it did work? Thais Is bumming me out I had a sunday afternoon and about 30 bucks in this thing ah ah

[strassercaster]

So which is it cut or no cut? To be or not to be. I got those vactrols you wanted as well

[motterpaul]

All I know is that the 1M trim pot mattered a LOT - both the value and the type. I find the really cheap ones with metal on metal discs seem to flame up. I try to buy the Cermet plastic ones so you don't risk shorting the trimpots out (even with a plastic screwdriver those cheaper things would sometimes flame up).

I also noticed that when I had it on full at 1M, and before I acquired the 1M I tried 500k and it was half as loud. It honestly makes me wonder if you might be better off just trying a much bigger trimpot, or maybe just 1.5 or a 2M resistor just to see what happens.

That was really the bottom line - when I had it sounding good - it was right after I put in the 1M Cermet trimpot. Maybe that burned out eventually or something else, but it was never the same after awhile. The problem with builds that complicated is they are really hard to troubleshoot.

Plus - you could buy a used one for probably about $50, right?

[strassercaster]

Ya trouble shooting this circuit has me stumped. I can6t find working voltages or a schematic. I have went over the thing 3 times an hour at a time. I never do more than an hour when troubleshooting unless im making progress. I ordered a 25 turn 500k trim pot ill put like a 750k  resistor in series and maybe i can dial it in maybe ill do 2 500k for more range. I have a feeling that he changed the layout after verifying and something is amiss. I wish I had the schematic do you have one?Did you get the bricks? I got the vactrols you wanted 6 for 20 with tax and ill need 4 or five for shipping ill email you soon

[motterpaul]

Strasser - I am just a little curious about these Vactrol orders you have mentioned a couple of times. I (motterpaul) did not ask anyone or even mention getting vactrols. I use LEDs with LDRs - and have been doing that successfully for probably 10 builds now.

I am really interested in seeing how you do with that icreased impedance (500k + 750k-ohm). Good idea.

If you google ISP decimator schematic and hit "images" a lot comes up. I don't know if they go with this circuit, but here is one example.

[strassercaster]

Hey sorry i just now saw your message. Ill check and see if they have more vactrols.They had the vtl 5c3/2 and vtl 5c 2 but some guy was buying them up to sell online they said. I got my isp to work sort of. It was doing its thing on the bench .I think we need a 25 turn type trimmer. I hit a spot and worked for a bit then when i boxed it it stopped. I think it is very very touchy as far as setting the trimmer i must have just bumped it or something. I ordered a multiturn trimmer and its somewhere i have to find it and see . I havent touched it for a while. I had about 14 bad builds i just wen5t through and only had two that didnt work left. I am back up to 5 that arent right again. Ill clean house of the bad builds  after I pump out an order of 6 for this music store that wanted there own boutique pedals that im making.  

[strassercaster]

Also you can get vactrols really cheap on aliexpress. I order over half my stuff there now. 100 resistors for 64 cents chips are 10-15 cents each  even 5532 are very cheap at times.I still use tayda for potentiometers and enclosures and electrolytic caps but aliexpress is cheaper on a lot of stuff. Shipping tales 3-5 weeks