2Sk30 substitution in the low rider

[midwayfair]

1) Low rider

2) No sound. (Squeaks for a split second sometimes the moment it's plugged into the power.) I suspect it has something to do with subbing 2N2457s for the 2Sk30s per Bean's recommendations. The data sheet for the 2N2457 says that the drain and source are interchangeable, so I didn't think I'd have to swap any leads, but looking back at the 2Sk30 datasheet, I'm having some trouble telling whether the gate is on the opposite side. (It's on the right looking at the flat side of the 2N5457; it might be on the right of the 2Sk30.)

Has anyone done this substitution that they could say whether they're oriented differently? I soldered the transistors in and would prefer not to remove (or replace them with the 2SK30s) until I know this.

3) I've double and triple checked all my values and done a thorogh search visually and with a multimeter for solder joints. If this isn't the problem, I'll start looking at the chips once I order new ones. I had plug a couple in backwards for about 30 seconds and it's possible I blew one. It certainly drained my battery in a hurry ...

4) See #2. I've also omitted C12 and socketted C10 (currently has a 1nF) per Brian's suggestions in the build doc.

EDIT: I should include the links to the datasheets. http://www.datasheetcatalog.org/datasheet/nec/2SK30.pdf

http://www.fairchildsemi.com/ds/2N/2N5459.pdf

[Haberdasher]

From what i can gather, the 2sk30 goes sgd while the 2n5457 is gsd.
I think you need to swap the source and the gate.  I do this all the time with 2sk117's from tayda and it works great.  Just insulate the middle leg with some stripped wire sleeve and go nuts.  They face the same way as a 2n5457 would.

[midwayfair]

From what i can gather, the 2sk30 goes sgd while the 2n5457 is gsd.
I think you need to swap the source and the gate.  I do this all the time with 2sk117's from tayda and it works great.  Just insulate the middle leg with some stripped wire sleeve and go nuts.  They face the same way as a 2n5457 would.

Thanks!

I should have used sockets and this would have been much easier to troubleshoot ...

[Haberdasher]

after you desolder, definitely use a socket.  I'm pretty sure what i said is accurate but I hate the thought of you having to desolder again.

[midwayfair]

after you desolder, definitely use a socket.  I'm pretty sure what i said is accurate but I hate the thought of you having to desolder again.

yeah, I was impatient and ran out of sockets over the weekend.

[Vallhagen]

Hi.

I just recently build a low rider with 2n5457. I located them just as the PCB symbols (i have to admit i never bothered to check the data sheets for comparison), no leg swapping or anything.

I have a thread in "build reports" with pics, if u wanna take a look.

The unit works just fine.

[Haberdasher]

Oops, the data sheet I looked at said 2sk30 was sgd but maybe I'm mistaken?
http://jm.plantefeve.pagesperso-orange.fr/2SK30.pdf

[midwayfair]

Oops, the data sheet I looked at said 2sk30 was sgd but maybe I'm mistaken?
http://jm.plantefeve.pagesperso-orange.fr/2SK30.pdf

It looks like maybe they vary by manufacturer. I'll have to get out the magnifying glass when I get home to read who made the ones I had. But I know that the 2457s I used work fine - I plugged them into an orange squeezer first, and Vallhagen says that he didn't need to do any lead swapping.

I think after some more debugging (I'll check ALL my values again) and adding the sockets that should arrive this weekend and testing the STOCK transistors (and maybe putting C12 in), if it doesn't work, it'll be time to order replacement chips (see #3 above) so I can eliminate that potential variable.

[Vallhagen]

Despite the circuits complexicity, the "clean" signal chain is pretty straightforward. If the unit is completely dead (and all your basic troubleshooting as values, solder points etc are done) i would check there first. That would be IC1, IC6 and (swapped legs or not) Q1. 

Cheers

[midwayfair]

This is fixed.

After going over the components in some real lighting after I got home, I finally found the faulty part - It was a broken Ge diode, not a bad chip or reversed transistors. So yay for not desoldering working components before checking parts an extra time!

It wasn't a little broken, either. It was cracked straight through. Replaced it and now the effect works. It sounds very cool. Glitchy and a little fuzzier than I expected and thus perfect for the synth board I'm building. I may or may not add C12 back in. Right now I'm using a 4n7 in the C10 slot (1n was simply too fuzzy).

Am I correct in assuming that the fundamental can't be dialed out completely on the upper octave, though? It's still present no matter where the upper octave is set. Seems to come through more with more pick attack. When I turn up the clean the fundamental definitely becomes "cleaner," but the actual volume doesn't really change.