Black Finger solid state v.1

[lowell]

hello,
have a semi broken black finger sustainer. believe it's version 1 and has dual op amp nte949. anyone have schematic or any help with fixing this? I have replaced the opamp and a transistor but am lost now. I remember a resistor that was connect two points together but don't remember what value or where it went. any help or a schematic would be great.

lowell

[lowell]

ok figured out that it's the original version which had the 748IC in it. however the schematic does not specify what the pin #s are in the diagram. could anyone help me here?

thanks!

[52 Bill]

Look for a data sheet for the 748 or for the NTE949. It should show the pinout for the chip.

Also you could look at the schematic and compare it to the circuit board in the pedal.

[Alex R]

First do diode tests on all the transistors. Chances are they're ok and it's one or both of the chips. If there's a dead transistor, though they look a bit special with their round packages and gold wires they are ordinary small-signal silicon types easy to replace.

I repaired one of these for a patient customer a year ago. EH sent me a schematic featuring a 741 and a CA3080. My schematic has the pins numbered. Not sure if yours is an earlier version? Might be worth getting the other schemo, it may be just the chips that are different, and the version I had did give the 'right' sound (see below).

Both chips on mine were dead. The 741 was in an obsolete package, round with wired in a circle coming from the bottom, metal can. I used a dip8 type instead, Got the pinout from a datasheet, soldered wires to its legs and so on. The CA3080 is obsolete anyway and hard to get. There is an electronically similar replacement for this controllable-gain amp chip, use one half of the LM13600 or LM13700. Again it's a matter of identifying the pins from the datasheet, soldering on wires...

Then it worked ok. This is a great compressor for that rhythmic fingerpicking sound. The owner said he'd heard it was 'cartoon-like' in its effect, he'd bought it for that reason, and that's about right. It has a slow attack so you really hear the pick sound, and a rather wobbly, uncontrolled and quite slow release which I thought was due to my repair till the guy played me someone's example mp3 and sounded just the same. I'd say it's not smooth enough for bass, but uniquely good for that certain rhythmic fingerpicking sound.

[lowell]

awesome i'll try that Alex... thanks for the help guys!