Slowgear Transistors...equivilents?

sir_modulus · February 12, 2005, 05:59:59 PM

I was wondering if anyone knew any common transistors that would work in a Slow Gear? The schematic calls for:
6 x BC546B
2 x BC550 or BC549B
1 x 2SK30A

Now for the 2SK30A, I know these are the flip flop fets for a Boss pedal, and are available at small bear (@ $1 ea), but does anyone know if any other Fets will work here?
As for the other parts, I am clueless about. Any help will be appreciated!

Cheers,

Nish

sir_modulus · February 12, 2005, 11:03:30 PM

bump

Paul Perry (Frostwave) · February 13, 2005, 03:18:14 AM

www.acme-sales.net/flyer.pdf has the 2SK30A at 39cents, Futurelec has the BC546 and BC550 at 10cents each.
So I guess they already ARE 'common', or at least 'cheap'!

pyrotek · February 13, 2005, 04:20:43 AM

sir_modulus, would you like to trade J201s for 2SK30s?

Paul Perry (Frostwave) · February 13, 2005, 08:26:01 AM

2N3904 and 2N3906 should do for the BC546 and BC550 respectively, but note that I havn't tried them. And I'm not sure the pins are the same.

Tychobrahe1979 · February 13, 2005, 08:27:26 AM

http://topopiccione.atspace.com/PJ03BossSG1.html

Paul Marossy · February 13, 2005, 08:43:13 AM

I used 2N5089s in place of the BC____ transistors, and that seems to work fine. According to this layout, http://topopiccione.atspace.com/pjimages/BossSG1layout.gif, you can drop the transistors right in there without any problems. The PCB I etched uses this layout.

The FET is another story, though. :x
So far, I have tried a 2N3819 and a J201, and it doesn't work with either one of those. The NTE "equivalent" for the 2SK30 is the NTE 459, so I may give that a try. I also need a 5.6V zener diode, I was using a 4.7V zener for some quick testing - I'm sure that's also a factor. The best that I could get is just a straight thru guitar signal with a J201...

It took about 4-5 hours for me to etch the board, drill it and populate it. It's definitely not a beginner project!

sir_modulus · February 13, 2005, 09:23:38 AM

Aighty, thanks a lot for all the input! I've decided to go for 2N3904's and 06's for the transistors. In regards to the fet...hmm...I can always rip one out of an old Boss pedal, and make it True Bypassed...Or just wait till my next small bear order!

Pyrotech: I have no J201's to even speak of....I'm FET defficient (except 2N5952's for my phase 90...I got plenty of those

). Thanks for the offer!

Cheers,

Nish

Paul Marossy · February 13, 2005, 04:39:44 PM

QuoteI've decided to go for 2N3904's and 06's for the transistors.

Uh, is there NPN and PNP transistors on this thing?! The schematic only indicates NPN types... :?

sir_modulus · February 13, 2005, 05:11:07 PM

Where'd the 2n3906 come from... :?

I've actually decided to go for all 2n5088's and the 2SK30A from small bear.

Cheers,

Nish

Paul Perry (Frostwave) · February 13, 2005, 06:23:51 PM

Quote from: Paul Perry (Frostwave)2N3904 and 2N3906 should do for the BC546 and BC550 respectively,

NO NO NO!
I need new glasses!! :oops: :oops: read the 550 as a 556, sorry!

Paul Marossy · February 13, 2005, 07:38:22 PM

I took a second look and actually, if you look at the original Boss Slow Gear schematic, there are (2) PNP transistors, but they look like they are part of the flip-flop circuit. The true bypass version as posted is fine with all NPN transistors. :wink:

Zero the hero · February 14, 2005, 04:24:23 AM

Hi Paul, I've been a little busy lately...
I was wrong when I said that i posted a wrong version of the SG-1: schem, PCB and layout are all CORRECT. Sorry for the confusion I created: I believe I misread all the pic names on the site...

I also added a small text about part substitution. 2N5088, 2N5089 and 2N3904 work well for all NPN transistors (and that's a general rule).
I managed to replace the FET too, but involves some part changing and a accurate testing, so i reccomend to buy a 2SK30A from Small Bear...

Read the complete substitution article at http://topopiccione.atspace.com/PJ03BossSG1.html

Paul Marossy · February 14, 2005, 11:09:20 AM

Zero-

Yeah, it looked OK to me, so I etched and built it last Saturday. I did read that text document as well. I just need to find a 2SK30 now...

BTW, your mind does funny things when you're tired. :wink:

Samuel · February 14, 2005, 11:18:21 AM

If the NTE459 is an equivalent of the 2sk30, try looking at a 2n5459, as I believe this is another equiv of the NTE part....

Paul Marossy · February 14, 2005, 11:20:30 AM

That might be worth a try. Unfortunately, I only have 2N5457s...

TheBigMan · February 14, 2005, 04:01:09 PM

There are 2 versions of the SG-1 AFAIK. One version (the first I believe) calls for the parts listed above, the second (March 1981 Service Manual) calls for Q1-2 2SC732TM, Q3 2SK30A and Q4-10 2SC945.

2SK30As are annoying in a way as they have a different pinout from "standard" FETs like MPF102, J201 or 2N5457. They are DGS as opposed to DSG.

Paul Marossy · February 14, 2005, 04:10:38 PM

The 2N3819 is DGS as well. It just doesn't work in this circuit... :evil:

Zero the hero · February 14, 2005, 04:19:23 PM

According to thid datasheet http://www.fairchildsemi.com/ds/2N/2N5459.pdf , 2n5459 has a very high Vgs off number (-2.0 .. -8.0). I believe that 2N5457 and a 6.8 or 7.1 zener will work better in this circuit.
Just remember to chose a zener diode that is about 0.8 .. 1.2 volts higer than max Vgs of your fet: for example, 2SK30A has Vgs of -0.5 .. -4.5 volts and a 5.6 zener is used.

You should aply the same method with 2N3819: have a look at the datasheet http://www.fairchildsemi.com/ds/2N%2F2N3819.pdf and see that Vgs(off) parameter is -7.5 Volts... this FET looks like a BC264 to me.

It's incredible how datasheet could be a mine for infos about transistors and ICs... I always have a look at them and always learn something new.

Take care of pinouts too, as always... but you can always twist the pins of your transistor to fit the layout provided!

Paul Marossy · February 14, 2005, 04:52:51 PM

Ah, I think I'm getting the idea now. :oops:

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Slowgear Transistors...equivilents?