nte458 will not work in place of J201, please help.

[ronnie]

Hello, I built the Electrictabbs Boogeyman pedal, the layout requires 4 J201's, I have Nte458's, So I put them in but it will not work, What could be the problem, I made sure the orientation was correct as far as where the drain would be, the pinout on the front packing on the 458 says DGS, Should it be DSG, if so, are their different types of NTE458's, Thanks for any help on this,

Sincerely,
Ronnie.

[Dragonfly]

Hello, I built the Electrictabbs Boogeyman pedal, the layout requires 4 J201's, I have Nte458's, So I put them in but it will not work, What could be the problem, I made sure the orientation was correct as far as where the drain would be, the pinout on the front packing on the 458 says DGS, Should it be DSG, if so, are their different types of NTE458's, Thanks for any help on this,

Sincerely,
Ronnie.

i ROUTINELY use NTE458's (including a build i did tonite) in place of J201's ....i would guess that its something more than just the type of Jfet youre using...

did you check the drain voltages on the fets ?

[javacody]

I would go by what your 458 says.

Also, are you using a trimmer on your drains? You can sub several different types of JFET's but they each have to be tweaked to work correctly in the circuit (this is called biasing).

[ronnie]

No, I haven't, what should they be, would this be done while fets are in the circuit or pull them out and measure.

Thanks.

[ronnie]

I would go by what your 458 says.

Also, are you using a trimmer on your drains? You can sub several different types of JFET's but they each have to be tweaked to work correctly in the circuit (this is called biasing).

I used (4) 100k trimmers, I can turn them and set all Drains to 4.5v, but I still get nothing, any thoughts.

[javacody]

Time to whip out your DIY Audio Probe (see the GEOFEX link above, if you don't have one).

[Dragonfly]

No, I haven't, what should they be, would this be done while fets are in the circuit or pull them out and measure.

Thanks.

you could do either...some people will bias them off the board by wiring a pot as a resistor, setting the voltage to 4.5 (or so), and measuring the resistance on the pot...then you would use that value resistor connected to the drain....

me, i just use a trimmer pot instead of a resistor...its easier

[Dragonfly]

I would go by what your 458 says.

Also, are you using a trimmer on your drains? You can sub several different types of JFET's but they each have to be tweaked to work correctly in the circuit (this is called biasing).

I used (4) 100k trimmers, I can turn them and set all Drains to 4.5v, but I still get nothing, any thoughts.

after that, i'd check your output connections and your ground connections...

see the debugging page at GEOFEX for more info...

good luck !!!

[Steve C]

Check your pinout, IIRC the NTE 458 has a different pinout than the J201 (DSG).

[ronnie]

Check your pinout, IIRC the NTE 458 has a different pinout than the J201 (DSG).

Thats what I was thinking, in the faq section, I saw that the pinout for J201's are the same as Mpf102's (DSG) the 458's say (DGS) could this be the problem.

[javacody]

Yeah, it's pretty darn amazing what missing a ground or two will do to a circuit.  LOL   :lol:

[Steve C]

Yeah, the NTE 458 has a pinout of DGS and the J201's pinout is DSG.

[ronnie]

Yeah, it's pretty darn amazing what missing a ground or two will do to a circuit.  LOL   :lol:

Does this sound like it might be the problem javacody, if so, will 2n5457's work, do they have the same as j201's, (DSG)

[javacody]

Ha ha ha, I posted before I read your response. If you have the JFET's in wrong, that is definitely the problem (or at least one of the problems  ).

2n5457's should have the same pinout as a J201 and MPF102. 2N5457's will have less gain than a J201 and you will need to tweak the trimmers quite a bit.

[ronnie]

Ha ha ha, I posted before I read your response. If you have the JFET's in wrong, that is definitely the problem (or at least one of the problems  ).

2n5457's should have the same pinout.

OK, cool, I have (4) of those, I will try them, if that doesn't do it then it's back to square 1, thanks to everyone's reply's, I do appreciate it.

Ronnie.

[Dragonfly]

Check your pinout, IIRC the NTE 458 has a different pinout than the J201 (DSG).

the 458 is DGS , according to the package i'm looking at ...

[Dragonfly]

Yeah, it's pretty darn amazing what missing a ground or two will do to a circuit.  LOL   :lol:

gee...voice of experience talking

ive never done that  :oops:   (ok...maybe a few times )



BTW....sounds like changing the pinout should fix it this time...

[javacody]

Yeah, the only mistake easier to make than leaving out a ground is getting the pinout wrong.  LOL

[sir_modulus]

No, I'm sorry, but none of you can top my experiance....

I wonder what happens, when you put a power diode in a power amplifier (DC, 60 V - 5.2kv) and wonder why the power is not even getting past the filtering section. It turns out that I just put the diode in wrong, but that was only after it reversed biased itself till the point of shorting....and let me tell you....4.some odd KV is NOT fun to short to ground....I burnt a $ 500 power amplifier board....with a single diode... :oops:

Ah, the joys of bad pinouts.

Nish

P.S. and for you critics out there, the diode had NO band!

[ronnie]

I trird 2n5457's, the circuit still doesn't work, I get signal when the effect is bypassed, but no signal when effect is engaged, I double checked all wiring, electrolythic orientations, tested the switch with DMM, I will try audio probe next, if the problem is a cold solder joint or dirty contacts, whats the proper way to correct the problem, I've been useing desoldering copper wick, after that are you suppose to clean the exsisting solder off the pads, if so how do you do it.

Thanks.