Jen - KPS900 Phase Shifter  [schematic]

Discussion regarding early stompbox technology: 1960-1975 Please keep discussion focused and contribute what info you have...
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GodSaveMetal
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Post by GodSaveMetal »

batteryacidtea wrote:Hey guys, sorry to ressurect the topic, I have one of those to true bypass, and the unity I have here have a LM348N in place of the 3403 and works just fine!
Please PHOTOS of all you have or will do!!! thanks! :mrgreen:

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batteryacidtea
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Post by batteryacidtea »

damn, I've already closed the pedal and packed it to send it back, just have some pictures of the finished rewiring

it looks like this, now
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Jen - KPS900 Phase Shifter guts
Jen - KPS900 Phase Shifter guts

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Post by gigelmargel »

Hello and thanks all for this work!

I finished a clone, but it doesn't work. I used a LM348N instead of MC3403 and a 250K trimpot instead the 220K one.

The pots were wired following the schematic:
- Intensity (1M): lugs 1+2 to the pad from the bottom right corner and lug 3 to speed 1+2 lugs
- Speed (500K): lugs 1+2 to second pad from the top and lug 3 to first pad from the top (upper right corner)

The LFO ticks, but no phase (I've adjusted the trimpot very carefully).

Anyone has same problem? Zenner is 4.7V for sure? A LM324 or TL074 would be better? Maybe I must to try more 4007 (I used an HCF)?

Best regards!
Radu

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Post by gigelmargel »

Hello again!

After I swapped 5-6 of 4007 and 7-8 LM324/TL074/LM348, I looked at the schematic of the LFO and I saw that's very close to the Phase 45 one.
I rechecked the layout (https://www.freestompboxes.org/download/ ... &mode=view) and I found the mistake: the 4.7mF cap from the right upper corner is reversed!
In Phase 45 schematic this cap is 10mF, so replaced it with 10mF and I reversed...and it worked fine from the first time! It sounds very nice, more than a vibrato...like Phase 45 :)
I think that is a drawing error, because in the previous layout (https://www.freestompboxes.org/download/ ... &mode=view), this cap is 10mF and its position is fine...anyway, I think that someone will check the values of all the 3 electros.

Thanks all again!

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Post by Dirk_Hendrik »

That should be something like this;
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Jen_kps900_phaser.pdf
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Sorry. Plain out of planes.

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Post by gigelmargel »

Dirk_Hendrik wrote:That should be something like this;
Thank you very much, Dirk! I will change the 10mF cap to 4.7mF soon.

Best regards!

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Post by Bernardduur »

Dirk_Hendrik wrote:That should be something like this;
Hey Dirk,

The IC should be a Motorola MC3404; the IC on the schematic is stated as a 4303
'No more....... loud music.......'
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Post by Dirk_Hendrik »

#include <typo.h> :blackeye
Sorry. Plain out of planes.

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Post by Bernardduur »

:)

I got one quite cheap. A nice 2 stage phaser that shares a lot of similarities with the phase 45.

The biggest problem was the volume. When turned on the volume drops quite significant. My guess is that they 'shared' some ideas with the phase 45 but made a mistake on the inverting input of the first IC stage; they used 220k instead of 22k (which is the phase 45 value). When I change this resistor to 15k (common fix for the volume drop in a phase 45) and add some pull down resistors next to true bypasing this baby, it has unity volume and sounds pretty awesome!!
'No more....... loud music.......'
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Post by urban_paranoia »

Thread resurrection (sorry!)

I’ve just acquired a non-working Jen KPS900 and I’ve de-cased it prior to doing some testing:

Image

I just wondered (as a lot of the wiring seems non- original) - does this look correct?

One issue I did spot straight away was that the MC14007 was inserted backwards in its socket, so that won’t have helped things any… :shock:

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