NOS Phaser of 1973 with 4Fet

[radio]

Hi

I was lucky to buy a 1973 Phaser(pedal) that was though to be

a P90 clone ,as it has lots of hiss I asked the schematic from Schaller

I got overnight(thanks for quick response) don't know if ever sold in
USA but it's build no more . There was 1cap different(1st) from
schematic .01uF against 6.8nF 3 others.I guess there was no intention
slight monday mistake.I d discribe sound as slightly flangerlike.

-Would you change 1st cap?
-or change to univibe 4diff.caps??
-leave it vintage and add noise gate
and finally do these caps add hiss(ceramics) and should be changed
to metal film including feedbackloop
http://webplaza.pt.lu/jmernzer/iceland/Phaser1sch.jpg
As this pedal isn't build anymore I post tis link only for reparing and
educational issues any copyright belongs to its owner.
It's solely sold at www.rockinger.com as NOS .
I'm not affiliated to Schaller and Rockinger in any way.

Thanks for any response
Ernzer Jean-Marie

[Transmogrifox]

I would leave it like it is, only start by replacing the FETs and IC components.  I have a big muff from that era that one day suddenly became a noise monster.  I suspect the effect of aging and use on the semiconductors greatly decreased their favorable noise characteristics.

[R.G.]

... or you could try reading the GEOFEX effects debugging page, which has a section explicitly for getting old, senile effects running again.

Just a thought.

[radio]

Hi R.G.

1 and 2 done,pot replaced
3 ,none seen
4 doubt about one wire ,replaced
5 I supposed that was only necessary with ol tube TVs so I was wrong
in this point.
6 nice one,will be done after internet session
7 surprise after 6 done
8 ho hiss gone or build noise gate,we'll see

Thanks R.G. exactly what I needed ,a straight methode

Kind Regards Jean-Marie Ernzer

[radio]

@Transmogrify

I suspect I would have done this if it was not a phaser

May be the Ic could be replaced as it is 1458 compatible

Maybe the bc264b could be substituted by bf245a but
my suspicions that some damage is here is only based on
an AB test with a similar model where all 4 caps ARE identical

And last:What will happen with the circuit with TL072?

After all it sound good not as dense as P90 butis more

likely to be good with further modulation effects on the pedalboard

Thanks for your help

Ernzer Jean-Marie

[puretube]

I`d swap the FB cap with the 1st shift cap;
if the big value Rs are carbon, I`d swap`em for metal;
I`d re-think the Zener bias-supply...

[radio]

Hi Puretube


Sounds familiar except for the Zener diode,what is the alternativ

voltage-splitter?

Gruss Jimini

Edit :sorry ,standard voltage divider?

[puretube]

either "ordinary" voltage splitter (low impedance, e.g. 2x 4k7);

or at least replace the 100µ across D1, as it might be spoiled,
and parallel it by a 100n;

also, I`d place a 100µ||100n across the rails...


the ceramics don`t add noise in this schem, IMHO.

[radio]

Thanks puretube

The surprise was that someone in the German forum

already had this changes,either privatly done,

or stock improvment by Schaller later in the

70s ,in both cases ,hiss was reduced a lot.

Lets heat the solder iron

Have a nice evening
Guten Abend
JMErnzer aka Jimini in German forum

[Paul Perry (Frostwave)]

Thats a good point puretube about the zener bias, it makes me laugh when some peope use zeners as a noise source & others as a regulator maybe there is a cap across the zener that has dried out?

[radio]

Well I guess its working like it should for this century

I'll try not to be to picky as I haven't compared the late 70s models

trimpot settings. How can I trust a zener diode again? :shock:

Thanks for help of all continents, really international,but fast as

usual. Depending on luck(well not a scientific approch) I may have

questions on a rotovibe,meanwhile I try not to let the solderiron

cool down

Have a nice evening , on your respectiv continent!

Regards JMErnzer

[puretube]

...maybe there is a cap across the zener that has dried out?

Brother Paul: that`s the one mentioned 2 posts ago:

"...or at least replace the 100µ across D1, as it might be spoiled..."

the points stated, are the most obvious ones - it is very probable, that Sch*ller themselves got confronted with noise issues, and had to look for improvements, as soon as they had released that pedal (although the customers weren`t  that picky about noise in the early 70`s) - so those are the nearest things to change, be it for the manufacturer 30 years ago, or for someone who wants to "clean up the golden oldie -

after that, you can always go and look for a more up-to-date opamp with lower noise-figure...

schafft euch!!

[radio]

Not to picky about noise.....

Ahem not a good sentence,but bare in mind they could limit output

to some7khz as the guitar boxes didn't deliver more :wink:

Just imagine th synth guy uses this (instead of 12stages moog phaser)

:lol: ,well yes they had cutoff filters in those days :oops:

Greetings Jimini