1980 EHX Small Stone Repair

[andrewnelles]

I was given a 1980 dated Small Stone that has been dead for at least 20 years, I'm hoping to get it back into working order. The original owner appeared to have changed the wiring around, I've restored the wiring back to original spec, which doesn't seem to have been the source of the issue. Looks like it was hooked up differently, but still correctly.

It passes a signal when activated, however their is no effect except for a minor change in tone. The color switch slightly alters this minor tone change. No phasing whatsoever.

Any suggestions on where to start with this? What would the easiest method be to test the functionality of the ICs?

All IC's are receiving about 6.3VDC into pin 7. Is that correct for this pedal?

I have experience working on various pedals before, but never a phase shifter, so this is new to me.

Thanks in advance.


Pics:

[theehman]

I'd start by checking to see if the oscillator is working first (IC next to the pot).   Audio probe the output pin for clicking.   If it's working, probe the output pins of the other ICs to find where the phasing stops.

[mustardwhirlpool]

Dropping by 5 years late because I found this thread through a google search, and I have literally the exact same problem with a 1980 Small Stone I'm working on. Clicks on, has a vague phaser-like sound, but definitely not as prominent as it should be.

Shooting in the dark here, but did you ever figure it out?

[andrewnelles]

Dropping by 5 years late because I found this thread through a google search, and I have literally the exact same problem with a 1980 Small Stone I'm working on. Clicks on, has a vague phaser-like sound, but definitely not as prominent as it should be.

Shooting in the dark here, but did you ever figure it out?

It ended up being an easy fix, I remember that, but I can't remember what it was.... I have a vague memory of it being a faulty IC.

[c_dragon]

Hi Guys,
I find myself in the exact same position. Vague phaser-like sound but not as it should be?
Mustardwhirlpool, did you happen to fix it? 
The owner tells me the problem started when he accidentally stood on the pot but the pot seems to be working perfectly for me.
Hope you see this!

[11-90-an]

Welcome to the forum...

Dropping by 5 years late because I found this thread through a google search, and I have literally the exact same problem with a 1980 Small Stone I'm working on. Clicks on, has a vague phaser-like sound, but definitely not as prominent as it should be.

Shooting in the dark here, but did you ever figure it out?

It ended up being an easy fix, I remember that, but I can't remember what it was.... I have a vague memory of it being a faulty IC.

[c_dragon]

Welcome to the forum...

Thanks 

[Toshkomarov]

Hi guys, I had a Small stone delivered yesterday but no wiring and I can't handle it myself. I don't know where to solder input, output, and the switches, there are just no cables. Can you help me with pictures or tell me exactly what wires to solder. Thanks in advance

[Mark Hammer]

First, welcome.

Without wishing to dismiss your request, I think you'll find that there are often a pleasantly surprising number of "gutshots" of pedals posted around, in addition to schematics.  There are, however, several different Small Stone circuits since the very first one, as different chips became available or out of production.

If you cannot find a picture that corresponds to your particular pedal, at the very least you need to pop the enclosure open and tell us how many chips it has and any noteworthy characteristics (e.g., 8 pins, 16 pins, etc.).  That can help to narrow down which issue it is, and where connecting wires need to go.

[mozz]

Adding to the above posts, i have one here that i do remember changing a IC because it was bad. So i am thinking certain versions are known for this problem. Once you post some pictures or what version yours is, we can go further.

[Mark Hammer]

OTAs can apparently be fried if the current fed to the Iabc pin is too high.  Manufacturers will obviously design pedals to avoid such mishaps, but when pedals use 5^ tolerance resistors, and someone plugs in the "wrong" power supply, mysterious things can happen.

[ElectricDruid]

OTAs can apparently be fried if the current fed to the Iabc pin is too high.

No "apparently" about it! They *can*. I've discovered this the hard way on my breadboard!

If you've managed to avoid ever having released this particular magic smoke, Mark, you have my respect