EH Small Stone

Forum dedicated to helping people debug and troubleshoot non-functional pedals or builds. Please use an clear and informative title, indicating circuit and basic problem. Don't forget to mark the issue as fixed if this is the case.
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Post by espinete »

Hi all !
The pedal has no effect when engaged. It also has a big volume drop.
There was a shortcut due the bad shape of the "Color" switch. I cut the common leads and the ones at the down position and put together.

One of the transistors was dead, I put a bc239 (same pinout as the bc309's.)

I guess I can use ca3094's instead of eh1048 wich are completely impossible to find. Now there are five ic sockets for the op amps.

The ca3094 near the pot area measures 0.70v @ pin 6 with the potentiometer at maximum.
The rest of the op amps measurements at pin 6 :
Ca3094 5.42v
Ca3094 5.42v
Eh1048 3.23v
Eh1048 3.23v

I saw a 10uF e.capacit but there is a printed text saying 33uF in that component, so I changed it to 33uF.

I also changed the first resistor of the power supply 43R to 47R to be more relaxed😅

The ca3094 ota chips are very expensive. I was thinking about to buy some chinese copies for my proves believing they have the same pinout but I'm not sure.

I installed a new b100k (Lin) pot. I guess 3 (In) and 2 (wipper) pins are together.
I'm using this issue j schematic : ... -schematic

Any help will be welcome and appreciated

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Post by Lani »

I would be cautious if buying these chips from China. I know it's tempting considering the prices but if it to good to be true it prob is.... If you had the ambition one could make a ca3094 copy by using a LM13700, a couple BJT's and a few passives. Check out the datasheets and the schematic for the CA3094 is right in there. I've been wanting to do this but keep putting it off as I have many many projects going at once at the moment.

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