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Old 23rd May 2013, 04:54 AM   #1
spuddo is offline spuddo  Australia
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Default unobtanium---little help

Hi All , a little help needed finding the following.
These are used in synthesisers---old ones.
LS3954A---dual n chn jfet TO-71
UA726HC--temp controlled diff pair---10 pin can
E402------dual n chn jfet TO-71

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Geoff
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Old 1st June 2013, 12:29 AM   #2
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Quote:
Originally Posted by spuddo View Post
Hi All , a little help needed finding the following.
These are used in synthesisers---old ones.
UA726HC--temp controlled diff pair---10 pin can

Regards
Geoff
Really? There are diff pairs MAT02 or from THAT corp. that will certainly sub for these. I can't see an audio application that actually needs ultra DC stability, very strange.
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Old 1st June 2013, 12:34 AM   #3
Sprags is offline Sprags  United States
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I work with jet engine components that are made from unmachinabilium.
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Old 1st June 2013, 02:04 AM   #4
spuddo is offline spuddo  Australia
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Hi , scott. The Ua726hc is used with VCO's that require temp stability or everthing will sound like the Sex Pistols . The Mta02 been tried , it's not a straight sub.
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Geoff
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Old 1st June 2013, 03:31 AM   #5
benb is offline benb  United States
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More specifically, it's for the exponential converter in the VCO.

I googled the part # and ... long explanation short, I'd rather redesign for a currently made device than ...

I see from the datasheet, that thing includes an on-chip temperature regulator as well as the two transistors. I remember the Micromoog used an LM3046 this way, it's still made in SOIC, and NOS DIP parts should be available cheap. Here's something about using it:
Re: uA726 replacement, (the comedy of errors)

Here's a temp-regulation circuit using a multitransistor array, it should work as well (or as badly) for the LM3046:
http://www5b.biglobe.ne.jp/~houshu/synth/ExpPent.gif
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Old 1st June 2013, 04:30 AM   #6
spuddo is offline spuddo  Australia
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Hi Benb , reading the ua726 replacement article is enough to put paid to that idea,
The piece of equipment i'm repairing is a minimoog and no way would i diy a sub--it deserves a drop in replacement.
As it turns out, last night i managed to get a nos part .
Regards
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Old 1st June 2013, 11:34 PM   #7
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Quote:
Originally Posted by spuddo View Post
Hi , scott. The Ua726hc is used with VCO's that require temp stability or everthing will sound like the Sex Pistols . The Mta02 been tried , it's not a straight sub.
Regards
Geoff
I've worked before with guys restoring classic stuff, I understand that re-engineering is frowned upon and NOS replacements are the only acceptible solution. Though if Diana Krall sounded like the Sex Pistols it would be an improvement.

God Save the Queen.
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Old 2nd June 2013, 12:44 AM   #8
spuddo is offline spuddo  Australia
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Hi Scott , Diana Krall is now on my "to avoid at all costs " list.
God save the Queen , yes but which one -Andrew, Edward or Charles
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Old 21st July 2013, 07:24 AM   #9
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Try utsource.com to get some uA726. The 726 has a powered heater in the IC to keep the dual transistor section at a stable temperature; there are no other similar devices of which I'm aware. Be sure to check/test the 726 you get from ut; they take returns if they're fake.

Bridechamber have the LS3954A but it's $12.00 each:

Hard 2 Find ICs

Try getting a quote on 2N3954A from questcomp:

Quest Components Part Details

Quest are a great company and are very helpful with rare components and good quotes.
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Old 21st July 2013, 02:48 PM   #10
spuddo is offline spuddo  Australia
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Hi tape echo , thanks for your reply. How do you test the UA726 Hc out of cuircuit , i need them to build a vco but am at a loss as to how to check them before building.
The irony of all this is that 12 months ago i sold 18 that had been sitting around for a decade or to two---thought i'll never need these---DOH.
Thanks for the links.
Regards
Geoff
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