Author Topic: Trouble with JFET Boost Circuit  (Read 502 times)

mrahc_jftd

Trouble with JFET Boost Circuit
« on: October 25, 2020, 05:48:21 AM »
Hi everybody! Complete newbie here.

I'm having a bit of trouble with this circuit. I had it going once, but now I've rigged it up again I'm just getting nothing.

I feel like maybe I'm not successfully getting power to the J201, I rigged up a quick LED off to the left and it didn't turn the light on, so it leads me to believe I've not got power going into the circuit.

As I'm not sure and I know the people here are absolute legends, I thought I send over the schematic and photos to see if anyone here can spot where I've gone wrong!

Thanks guys. Hope you're all keeping well ❤️








antonis

Re: Trouble with JFET Boost Circuit
« Reply #1 on: October 25, 2020, 06:20:13 AM »
What's the purpose of +9V wire on 3PDT switch lug 7 (upper right..) ..??
"I'm getting older while being taught all the time" Solon the Athenian..
"I don't mind  being taught all the time but I do mind a lot getting old" Antonis the Thessalonian..

niektb

Re: Trouble with JFET Boost Circuit
« Reply #2 on: October 25, 2020, 06:22:51 AM »
I'm not well-versed in reading color codes from a metal film resistor but is R4 1 milli Ohm or 1 Mega Ohm? (since m stands for milli and M for Mega)

antonis

Re: Trouble with JFET Boost Circuit
« Reply #3 on: October 25, 2020, 06:38:56 AM »
There aren't commercially availiable resistors of 1m (0.001Ohm) value..
"I'm getting older while being taught all the time" Solon the Athenian..
"I don't mind  being taught all the time but I do mind a lot getting old" Antonis the Thessalonian..

Steben

Re: Trouble with JFET Boost Circuit
« Reply #4 on: October 25, 2020, 06:54:57 AM »
Greetings!

Welcome. In Dutch there is a saying: "Meten is Weten" = to measure is to know.
Do have a multimetre? Can you check voltages?

It is just as possible a solder joint is mechanically ripped with moving the circuit.
Rules apply only for those who are not allowed to break them

Steben

Re: Trouble with JFET Boost Circuit
« Reply #5 on: October 25, 2020, 06:57:02 AM »
What's the purpose of +9V wire on 3PDT switch lug 7 (upper right..) ..??

LED power connection probably.
Rules apply only for those who are not allowed to break them

antonis

Re: Trouble with JFET Boost Circuit
« Reply #6 on: October 25, 2020, 07:05:48 AM »
LED power connection probably.

If so, black wire goes to LED anode, which anode is also connected to "somewhere" when effect bypassed (red wire on lug 9)..

"I'm getting older while being taught all the time" Solon the Athenian..
"I don't mind  being taught all the time but I do mind a lot getting old" Antonis the Thessalonian..

Steben

Re: Trouble with JFET Boost Circuit
« Reply #7 on: October 25, 2020, 07:10:31 AM »
LED power connection probably.

If so, black wire goes to LED anode, which anode is also connected to "somewhere" when effect bypassed (red wire on lug 9)..

Yes, that wiring might be a problem. It can connect power to gnd for example... We can't see where the wires go of course.

mrahc_jftd, can you show where the wires go?
Rules apply only for those who are not allowed to break them

mrahc_jftd

Re: Trouble with JFET Boost Circuit
« Reply #8 on: October 25, 2020, 08:56:31 AM »
Probably not the wisest of methods but the set up of the footswitch was just one I spotted on Google images and I just ran with it!

But to answer the question as to where that wire's going - it's going from the positive lug on the DC Jack, to that top right pole, then the middle right lug (LED) goes into a 2.2k Resistor, into the LED anode (just soldered on component to component) then it is attached to another wire, which runs to ground.

I'll grab a photo of it asap, apologies. But I threw the explanation in to hopefully illuminate where that's going.


duck_arse

Re: Trouble with JFET Boost Circuit
« Reply #9 on: October 25, 2020, 09:27:06 AM »



see in the highlights, the breaks in the blue/red continuity indicators? that break indicates there is no continuity in the middle of the busses, you need to jumper across each break, or move your power connections to the other end of the board.

[this exact problem caught me this week - but without the coloured lines.]
Now battery powered. Remove plug when not in use, please.

mrahc_jftd

Re: Trouble with JFET Boost Circuit
« Reply #10 on: October 25, 2020, 07:46:18 PM »



see in the highlights, the breaks in the blue/red continuity indicators? that break indicates there is no continuity in the middle of the busses, you need to jumper across each break, or move your power connections to the other end of the board.

[this exact problem caught me this week - but without the coloured lines.]



Mate!!! Thank you so much. This was exactly the problem. Worked swimmingly afterward!
Thanks everybody I appreciate you all & wish you a happy day/night.

duck_arse

Re: Trouble with JFET Boost Circuit
« Reply #11 on: October 26, 2020, 09:03:04 AM »
keep the problems this simple and we'll get along fine.
Now battery powered. Remove plug when not in use, please.