Testing SAD1024's???

[digi2t]

Is there a test circuit that I could breadboard to test an SAD1024? I have someone nearby that has a few of them, but doesn't know if they're good or not.

Part of the Mutron Flanger circuit, and an oscilloscope maybe?

[R.G.]

Any circuit known to work with them is fine.

The test is easy: if there is audio at the input, and good, clean, ground-to-power-supply clocks that are out of phase, if there is no audio on the output pin, it's bad.

Of course, this does require that you have a known-good circuit working first. Best to find a working pedal as a test-mule.

[Kevin Mitchell]

A bit obvious but... to scale things down a little you could test one side of the chip to cut the datasheet circuit in half - considering how the SAD1024 seems to be a dual 512 similar to the MN3210 you could just work something out using the circuit on the SAD512 datasheet - page 4. Perhaps you can sub the clock with something more bare bone as well.

That's what I'd do. Otherwise - Armdnrdy has developed a killer BBD tester a while back though thats far from a simple circuit. I kind of really want one and I don't even collect BBDs.

[Tony Forestiere]

I know you love your breadboard! Hope this helps.
https://dl.dropboxusercontent.com/u/3173950/SAD1024%20Blocks.PDF

[digi2t]

Thanks for the link Tony!

On a hunch, I thought about R.G.'s suggestion of finding a working platform beforehand. I might have a line on a working flanger that uses the 1024. If the deal comes through, I'll be all set. I was sure that Larry had come up with a test rig, but I wasn't sure if it was for the 1024 specifically.

In the meantime, gonna read Tony's article. Looks very interesting!

[DrAlx]

I built one for someone who had come across a bunch of SAD1024 and didn't know how to test them.
Basically I used a couple of 4047s. One to generate the clock, and one to generate an audio tone.

Shared here:

https://1drv.ms/f/s!AvrH61utWEtEhE9kBcw-1YE-6CfG

[R.G.]

The "find a working one" advice was intended to save the construction effort. The same advice applies in any case: get the power supplies and out-of-phase clocks working properly; in a construction effort, add the mixing resistors to mix the out-of-phase outputs. Then once power supply and clocks are verified, feed an audio signal to the input. If an audio signal appears on the output (after the mixing resistors in the case of a new construction effort), and it's reasonably like the input, then the delay is working.

SAD1024 faults tend not to be subtle. They usually either work or not, no in-between.

[Scruffie]

SAD1024 faults tend not to be subtle. They usually either work or not, no in-between.

Except for when only one side of the chip works

[digi2t]

Deal worked out. I have an old MXR 117 flanger on the way. I've got a 1024 that was gifted to me as well, I'll get to test it too.

Oh yeah... I'm getting a flanger out of the deal too!

@DrAxl: That tester looks absolutely kick ass!! I'd like to build one, would you happen to have the perf or vero layout for that? If not, no biggie, I'll draw up a vero.

Thanks for the input folks. World's best SB forum to my rescue, again!