spare instrument cluster

Ti Kan ti at
Thu Dec 14 14:46:17 EST 2000

cobram at writes:
> The chip is the same in both styles of clusters, early and late 5K's:
> 700Y
> The newer cluster also has an extra marking, "8851" right under the ITT.
> Checked their catalog, looks like it's been discontinued.

The 8851 is a date code: 88 for the year, 51 for the week number of the year
on which the chip was manufactured.

TCA700Y is the actual part number.  It's a positive voltage regular,
10V output, 0.22A max current rating, in a TO-202 plastic package.
The pin-out (when looking at the face of the package, from left to
right) is output, GND, input.

This particular part is used on many models of VWs and Audis (particularly
the 70s and 80s).  Early models (1980 and before) the GND pin is wired
directly to ground on the instrument cluster flex circuit, later models
have the ground go through a resistor (usually low value, like 33 ohms)
to ground.

Unless you look in junkyards, it's probably going to be difficult to buy
a 'real' TCA700Y (although a web search shows that a couple of electronic
parts warehouses in the UK still sells them).

No BTDT, but I would imagine substituting a National Semiconductor
LM78M10 or LM342-10 would work just fine (and you can cross-reference
these numbers to other manufacturers as well).  The only caveat is that
the pin-outs are reversed on these parts (input, GND, output).  So, when
mounting these on the cluster you need to do so with the part's face-side
down to match the flex circuit's pin-connections.

Hope this helps.

01 S4 2.7 biturbo quattro
84 5000S 2.1 turbo
80 4000 2.0
96 A4 2.8 quattro (sold but not forgotten)
    ///  Ti Kan                Vorsprung durch Technik
   ///   AMB Research Laboratories, Sunnyvale, CA. USA
  ///    ti at

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