Author Topic: Rev eng of Jen KPS 900 phaser - confusion.  (Read 1845 times)

nelson

Rev eng of Jen KPS 900 phaser - confusion.
« on: June 13, 2008, 08:26:41 AM »
Hi everyone,


I am in the process of reverse engineering a non working Jen KPS 900 phaser. So far, I have a pretty straightforward buffer, two allpass stages and fixed feedback deal.

What is puzzling me is that U2 is a quad opamp yet seems to be used as the variable resistance to ground for the opamp allpass stages and has no V+ or gnd connections on the correct  pins 4 and 11.

I will update this thread with detailed gut shots soon.

The PCB appears unmodified, no attempt at repair.

In the early rev eng stages it appears as if either U2 should be a CMOS buffer affair or a multi transistor/jfet dip package, either that or an opamp application I have never seen before.

Does anyone have a jen KPS 900 and can pop it open to confirm what the two IC's are? I have searched for a schematic to no avail. This effect is pretty rare and I am not holding my breath - but it would be much appreciated.

 
Preliminary schematic and gut shots to follow.

 :-*
My project site
Winner of Mar 2009 FX-X

soulsonic

Re: Rev eng of Jen KPS 900 phaser - confusion.
« Reply #1 on: June 13, 2008, 12:26:09 PM »
Hey, I just repaired a Bad Stone; sounds like you have a similar circuit there. The Bad Stone I repaired uses a CD4009 hex buffer as the variable resistance. You can check out the Bad Stone schematic here:  http://www.muzique.com/schem/badstone.gif
In this schematic, the device labeled "E" is the CD4009. "F" is an LM324. All the rest are RC4558. The transistor is a 2N5088. Man, there's alot of question marks on that schematic; I should redraw it with the info I've learned from the one I repaired.

I hope this helps!
Check out my NEW DIY site - http://solgrind.wordpress.com

snap

Re: Rev eng of Jen KPS 900 phaser - confusion.
« Reply #2 on: June 13, 2008, 03:30:55 PM »
man! you haven`t been to nelsons page in a while!

soulsonic

Re: Rev eng of Jen KPS 900 phaser - confusion.
« Reply #3 on: June 13, 2008, 06:06:09 PM »
Ha! I'd never seen that corrected schematic before. It should be more widely advertised.
Yeah, I hadn't visited his page in awhile... :icon_lol:
Check out my NEW DIY site - http://solgrind.wordpress.com

nelson

Re: Rev eng of Jen KPS 900 phaser - confusion.
« Reply #4 on: June 15, 2008, 11:32:37 AM »
I popped in a CD4049UBE in the *14* pin socket and the phaser fired right up.

Strange that a 14 pin socket would be used for a 16 pin chip - 4009.

It phases nicely when biased. Not the best phaser I have ever heard.

I will finish the schematic and post gut shots. Then stick it back up on ebay where I got it.



My project site
Winner of Mar 2009 FX-X

nelson

Re: Rev eng of Jen KPS 900 phaser - confusion.
« Reply #5 on: June 15, 2008, 12:04:52 PM »


Here is what I have.....

http://electroconducive.googlepages.com/KPS900.pdf

The pedal is working......

It is not making sense to me.
My project site
Winner of Mar 2009 FX-X

alunr

Re: Rev eng of Jen KPS 900 phaser - confusion.
« Reply #6 on: May 03, 2020, 06:02:49 AM »
Hi All,

First post and with it a reigniting of a 12 year old thread!

I was gifted a KPS900 many years ago as ďnon workingĒ.  During this lockdown I've been having a good sort out and Happened across this pedal.  Unfortunately it hasnít magically fixed itself in the interim...

So, is there a circuit diagram for the original pedal around anywhere? Some good photos of the connections from the circuit to the pots and inputs would be useful too as Iíve got 2 loose wires.

 Iím going to go through the board testing the capacitors and resistors etc and then Iíll see if I can get anywhere testing the ICs too. 

The ICs are a Motorola MC14007B and a Motorola MC3403P

Thanks for any help!!!

alunr

Re: Rev eng of Jen KPS 900 phaser - confusion.
« Reply #7 on: May 03, 2020, 09:44:46 AM »




Scruffie

Re: Rev eng of Jen KPS 900 phaser - confusion.
« Reply #8 on: May 03, 2020, 10:01:53 AM »
Over on the 'other forum' https://www.....org/download/file.php?id=23599

alunr

Re: Rev eng of Jen KPS 900 phaser - confusion.
« Reply #9 on: May 03, 2020, 10:03:39 AM »
Over on the 'other forum' https://www.....org/download/file.php?id=23599

The link didnít copy properly... 

duck_arse

Re: Rev eng of Jen KPS 900 phaser - confusion.
« Reply #10 on: May 03, 2020, 10:19:30 AM »
welcome to the forum, alunr. it is compulsory for all first-time posters to read this thread ....

https://www.diystompboxes.com/smfforum/index.php?topic=124168.0
"Awww you're lookin' good, baby."
"I wanna tell you a story, every man oughta know."

Scruffie

Re: Rev eng of Jen KPS 900 phaser - confusion.
« Reply #11 on: May 03, 2020, 10:34:39 AM »
Over on the 'other forum' https://www.....org/download/file.php?id=23599

The link didnít copy properly...
It did in its own way (it's censored) .free stomp boxes. (remove the spaces).

alunr

Re: Rev eng of Jen KPS 900 phaser - confusion.
« Reply #12 on: May 03, 2020, 01:32:32 PM »
Over on the 'other forum' https://www.....org/download/file.php?id=23599

The link didnít copy properly...
It did in its own way (it's censored) .free stomp boxes. (remove the spaces).

Ah, thanks!  Iím new here so didnít know the etiquette regarding external links

Once Iíve fixed 5is Iíve got an 80s cry baby to fix then Iím going to start on some projects of my own :). Thanks all!