SOLVED Episode Boost biasing

[EGRENIER]

I just completed the episode boost. Now I need to bias it with the trim pot. I’m not sure what I’m supposed to look for in terms of value or even sound.

I assume I’m biasing Q1 (2n5457) based on the trim pot location. I read in some Other thread that I should aim for half of the voltage. So when the pedal is on 9V should I read 4.5V on the collector ?

Right now full, open gives me 9.22V and if I turn the trim pot CW I can drop it to 7V. I checked and I have the right trim pot 50K.

So when facing the flat side starting from the left I read:
with pot CCW all the way
9.22V, 229.5 mV and 0

with pot CW all the way
7V, 218 mV and 0

Any suggestion ?

 

[EGRENIER]

Get on EG's mailing list. They put stuff on sale every week. It's surplus, so stuff constantly comes and goes. They have some generic Vactrol-type devices; a good deal when they're on sale. You have to test 'em 'cause there are usually a few duds. At 12 for $3, I don't mind having to toss a few out.

J112s have a large spec range for Idss & Vp, so be prepared to test & sort them. You might want to get some 2N5458s from Tayda as well. They are like 2N5457s, only hotter.

Will do...

I got also those on the Tayda order:

400 Point Solder-less Plug-in Breadboard White

Get It Fast - Same Day Shipping

www.taydaelectronics.com

You had recommended the 6 packs, do I need 6 ? I guess you'll tell me that depends how big the project I will breadboard... At 2$ each, I don't mind having more than less.

In terms of tools/accessories/testing goes anything you'd recommend to get from Tayda ? So far, I'm loading up on knobs, power jacks and leds...

 

[Chuck D. Bones]

Those are pretty small and you only need one or two. It is the least expensive option and you can give the extras to your pedal-building friends.

I have been using mostly ZY-204 solderless breadboards. They are featured in most of the breadboard pix I've posted. Plenty of room to build anything on this site. I get 'em on eBay and I buy from the seller with the best price + shipping at the time.

 

[spi]

Could Amazon be trusted ?

I would not trust amazon for those.

 

[Chuck D. Bones]

In terms of tools/accessories/testing goes anything you'd recommend to get from Tayda ? So far, I'm loading up on knobs, power jacks and leds...

1% 1/8W resistors, WIMA film caps, tantalum caps, opamps (the usual suspects) & pots. You can never have enough of any of those.

 

[EGRENIER]

1% 1/8W resistors, WIMA film caps, tantalum caps, opamps (the usual suspects) & pots. You can never have enough of any of those.

Yeah, I'm pretty much loaded for those... Obviously not all the values, but normally when I need one I buy 20...

I wish Tayda had Transistor testers or other tools of that nature... But testing on breadboard will be a good learning experience.

 

[music6000]

Your JFET is too cold (Idss & Vp too low). All too common to find those on eBay. Probably the leftovers from someone else cherry-picking the "good" ones. Take solace in the knowledge that your cold 2N5457s will be useful as subs for J201 in some pedals. Ideally, you should find a hotter JFET. Doesn't have to be 2N5457. Did you solder the transistors into the sockets? What' the point of using sockets if you're gonna solder them in? Your other alternative is to reduce R4 (try 2.2K) or change the BIAS pot to 100K.

Thanks Chuck for confirming my suspicions on the 2N5457!

What's that cheap Digital Screen device on Fleabay you have that measures all types of Transistors????

Just added Picture!!!

 

[EGRENIER]

Thanks Chuck for confirming my suspicions on the 2N5457!

What's that cheap Digital Screen device on Fleabay you have that measures all types of Transistors????

Just added Picture!!!

See that's on Tayda product list but out of stuck... would have probably got one...

LCR-T4 ESR Meter Transistor Tester Diode Triode Capacitance SCR Inductance LCD Backlight

Get It Fast - Same Day Shipping

www.taydaelectronics.com

 

[EGRENIER]

@Chuck D. Bones , @fig, @music6000, @spi, @Big Monk, @Dali, thanks for your support...

Well I swapped and measure the other 2N5457 that I have and all 3 are giving similar values +/- 500mV....

So, I'll get the Tayda order in and wait the 5 days

I ordered 20X J112 and 10X 2N5458, so I assume that out of 30, I should get something that works ?

 

[Travis]

Hi! Could I use j201 or 2N5457 with 18v for more headroom?

thanks guys

 

[music6000]

Hi! Could I use j201 or 2N5457 with 18v for more headroom?

thanks guys

Mark a Dot where it set at the moment.
Adjust Bias by ear either way of the dot & see if it gets better or worse!