MOTM

a) the part I would potentially use is: 248J-9-10-104 (I could also use 
248J-9-10-503 which is 50K)

b) I have not seen stock of these anywhere. If somebody has seen stock, please 
contact me.

c) the parts have 2 "issues"

1 - the plastic bushings can be easily stripped. And I mean *easily* you have to 
be very careful
2 - the shaft rotation is not the standard 300 degrees, which is what the front 
panel graphics are laid out for.
Instead the 248/249 uses 270 degrees, so the '0' and '10' ticks will not ever 
align (meaning, when the pot
is fully CCW, instead of on the '0' tick the knob pointer is on the '1' tick).

See how thrilling and exciting synthesizer design can be??!? :)

I'm not as concerned about (1) as I am about (2).

Comments? Anybody even locate the 248Js?

Paul S.

Hi Paul,
Why not try the plastic shaft 248's? They are in stock in a number of
suppliers, rather than plated brass. In my experience the plastic bushing is
not a problem, unlike Omeg. I do find some 1/8" shaft Spectrol 248's are
DOA, but I have never had that with 1/4". 
 
The electrical and mechanic rotation of the 148 and 248 are very similar.
 
148 is 300 degree machnical and 270 electrical
248 is 295 degree mechnical and 265 electrical
 
Rotation life is the same, although resistive tolerance is higher on the
248. And yes the 149/249 have some advantages over 148/248 but also a
shorter life span.
I can't see a major problem with switching to 248's. 
 
Regards
Rob
www.emulatorarchive.com
 
 
 


 

a) the part I would potentially use is: 248J-9-10-104 (I could also use 
248J-9-10-503 which is 50K)

b) I have not seen stock of these anywhere. If somebody has seen stock,
please 
contact me.

c) the parts have 2 "issues"

1 - the plastic bushings can be easily stripped. And I mean *easily* you
have to 
be very careful
2 - the shaft rotation is not the standard 300 degrees, which is what the
front 
panel graphics are laid out for.
Instead the 248/249 uses 270 degrees, so the '0' and '10' ticks will not
ever 
align (meaning, when the pot
is fully CCW, instead of on the '0' tick the knob pointer is on the '1'
tick).

See how thrilling and exciting synthesizer design can be??!? :)

I'm not as concerned about (1) as I am about (2).

Comments? Anybody even locate the 248Js?

Paul S.

It sure does.  I've used the 248s in DIY projects and never had any issues.
The pot torque is more than the 148s, but in all honesty I had never noticed
until Paul posted that info to the group.

 

John Loffink

The Microtonal Synthesis Web Site

http://www.microtonal-synthesis.com

The Wavemakers Synthesizer Web Site

http://www.wavemakers-synth.com

-----Original Message-----
From: motm@yahoogroups.com [mailto:motm@yahoogroups.com] On Behalf Of Paul
Schreiber
Sent: Thursday, May 24, 2007 3:37 PM
To: rob@emulatorarchive.com; 'MOTM litserv'
Subject: Re: [motm] Spectrol 248J pots?

 

My bad, they are both 300 degrees mechanical.

 

I will get some to try out.

 

This appears to me a more reasonable solution over paying $12.25ea.

 

Paul S.