[sdiy] ARP 4027-1 VCO cloning?

[Luís Marka]

Same here in Brazil. Such values are hard to obtain, unless you make an
overseas order. Anyway, I'll give Farnell a try here. This VCO looks nice &
easy!

Cheers,
Luis Marka

----- Original Message ----- 
From: "St Eric's..." <sainteric at piramiden.demon.nl>
To: "Dana Scott" <turbo at mustangs.com>; <synth-diy at dropmix.xs4all.nl>
Sent: Wednesday, August 25, 2004 4:16 PM
Subject: RE: [sdiy] ARP 4027-1 VCO cloning?


> Thanks for the info,
>
> Well, in my local shop here in the netherlands, these values were a
problem.
> next time I need values like these, I'll check Mouser or companies like
> that.
>
> Do you have more interesting arp issue's to share?
>
> cheers,
>
> Eric van Baaren.
> _____________________________
> http://www.piramiden.demon.nl
>
>
>
>
> -----Oorspronkelijk bericht-----
> Van: owner-synth-diy at dropmix.xs4all.nl
> [mailto:owner-synth-diy at dropmix.xs4all.nl]Namens Dana Scott
> Verzonden: woensdag 25 augustus 2004 20:47
> Aan: synth-diy at dropmix.xs4all.nl
> Onderwerp: Re: [sdiy] ARP 4027-1 VCO cloning?
>
>
> Those are all standard 1% values.  The FETs ARP used were 2n5459's that
were
> selected for a low pinchoff voltage. You can use 2n4392's with guaranteed
> results.
> You might have a little trouble finding the 2n5910 transistor. If you use
> something with a different switching speed you will have to adjust the
> resistors that are in the compensation loop. They are 2 equal value
> resistors with a .01 to ground in the middle. Can't remember the resistor
> values, probably 61.9K or 100K if I had to guess.
> I had an email from someone, probably on this list, that had 1.87K
tempco's
> for sale( rather high price IIRC).
> The TZ81/TZ581 expo pairs can be replaced with 2n3904/2n3906 pairs. No
> selecting or matching was done by ARP, Just replace the expo pair if it
does
> not meet spec.
> Somewhere in my pile of ARP stuff I have a 1:1 film negative of an early
> 4027-1. Not sure how I could copy it for you.
> I also have a copy of the ARP factory testing fixture schematic for the
> 4027-1 and a copy of the test procedure if that is of any interest.
>
> -Dana
> ARP Production Engineer 1974-1980
>
>
> Subject: Re: [sdiy] ARP 4027-1 VCO cloning?
>
>
> > > 61k9,121k,30k1,45k3,33k2,8k87,1k65,....and all of them 1%.
> >
> > You could use trimpots. (100K, 250K, 50K...)
> > --
> > john
> >
>
>
>