JHS SUPERBOLT troubleshoot

[Elijah]

Hello guys. I'm building a JHS Superbolt from effectslayouts.com and it does work but has a lot of whistle noises. I can't access J201 but I love Russian KP303a instead. KP303a has 4 pins the last being the enclosure(ground). So Q1 and Q2 are KP303a and Q3 is 2n5457.

Voltages are:
Q1:
     G=0
     S=0,43
     D=9,65
Q2:
     G=0
     S=0,64
     D=9,59
Q3:
     G=0
     S=0,17
     D=13,32
The noise (whistle) is super loud. Ratio is like 1/1. I think the problem is self-excitation of transistors but don't know how to solve it. Any help is really appreciated.

[Kevin Mitchell]

Isolate pin one of the 7660.
Or replace it with a LT1054 or 1044.

Also your solder work is a bit messy and suspicious of bad connection.

[iainpunk]

do you have a schematic for us?
what are the power bus voltages?

i think its the bad (non-existent) PSRR of the JFET gain stages feeding through the whine of the charge pump chip.
some of the soldering looks quite bad tbh, some contacts look shady, try to address those, there might be a problem with the PS filtering.
then, it that didn't work, try an audio probe to find out which of the JFETs produces whine, but that's extremely unlikely...

cheers, Iain

[intripped]

Isolate pin one of the 7660.

I think the problem is exactly this.
PIN1 of 7660 IC is isolated,  while it should be connected to PIN8
Just look at the PCB pic.
If you look at the original PCB from effectslayout, PIN1 is actually connected to pin8...

[Kevin Mitchell]

Isolate pin one of the 7660.

I think the problem is exactly this.
PIN1 of 7660 IC is isolated,  while it should be connected to PIN8
Just look at the PCB pic.
If you look at the original PCB from effectslayout, PIN1 is actually connected to pin8...

Oops. Yeah I think I had it backwards. The trace should be cut only if using 1054 or 1044.
I should know better 

[Elijah]

do you have a schematic for us?
what are the power bus voltages?

i think its the bad (non-existent) PSRR of the JFET gain stages feeding through the whine of the charge pump chip.
some of the soldering looks quite bad tbh, some contacts look shady, try to address those, there might be a problem with the PS filtering.
then, it that didn't work, try an audio probe to find out which of the JFETs produces whine, but that's extremely unlikely...



cheers, Iain

Here's the schematic and about the charge pump. As far as I know you connect pin 1 to 8 only if using lt1054. Otherwise not connected. Audio probing I found that both Q1 and Q2's drains generate that whistle. Q1 is more quiet and Q2 is amplifying the noise.

[Elijah]

Wait...  sorry guys, will connect pins. I don't know how I looked at the schematic.

[Elijah]

Nah it still is noisy. Nothing changed

[iainpunk]

have you tried cleaning the board for inspection of the joints, and re-flow any imperfect ones?
a good cleaning method is using cleaning alcohol / spiritus and an old toothbrush to clean off the flux gunk so you (we if you make new pictures) can have a good look at all the joints, and determine if there are shorts/bad joints/sputtering/etc...

i seriously doubt that a Jfet will oscillate at audible frequency's in such a gain stage if there are no bad connections/shorts involved.

cheers, Iain

[Elijah]

Yes indeed. I have. Pls tell me if you guys find sth bc I don't see anything suspicious.

[blackieNYC]

You have some solder joints that aren't completely"filled in". They are probably fine but they make inspection by others (and via photo) challenging. 

[iainpunk]

you might want to check those?

cheers

[antonis]

If reflowing doesn't pay dividends, place 470pF or so Miller caps on Q1 & Q2 stages..
(between Drain and Base..)

[intripped]

Is it OK to connect the 4th pins of the 2 transistors?
And what about connecting them to gnd?

[iainpunk]

you could connect them to ground, connect them to source or cut them off as short as possible. 
having those hanging open could well have been the ''antenna'' that caused the positive feedback that causes oscillation... maybe...

i'd grab alligator clips and try out 'source pin' and 'ground' connections.

good luck and cheers

[Elijah]

Thank you guys for all the feedback. I've done my best but this board doesn't let me fill them all. I've  cut the 4th legs of transistors and added caps as said above but the whistle is still there. The noise does change if I touch the IC and I changed it but nothing changed.

[ElectricDruid]

A certain amount of your difficulties stem from that awful PCB. It's a cheap paper+foil thing and that's not helping you.

[antonis]

Last attempt..

Disconnect +9V from IC1 pins 1 & 8 and connect it right on C3 Cathode / C15 +leg..

Don't deal with circuit good performance ..
Whistle is your main concern..