[Premium-Rx] URR-74/WJ8718 help

[Ahmet G.]

Hello

DS8857 is an IC made by National Semiconductor
It is a BCD to 7 Segment display driver, Decoder.
Current: 60mA 
Type: CA Common Anode

I believe you can replace this with a similar driver IC from the
74xxx series drivers that you can find easier in the market.
Such as: 7446, 7447, 74247 which are CA types

They have same connection diagrams and functions, each one with an 
additional function such as Ripple Blanking on the DS8857.

Usually there are power transistors that regulate the higher currents
on the display boards ( they are usually attached to heat sinks) and
these transistors tend to burn out before the driver ICs. One of the main
reasons is the fact the heat sink connection is lose or accumulated
dust thereby blocking heat flow.
So you may want to check to see if the transistors are ok before replacing
the driver IC.

Hope this helps.  

Ahmet Gundes

> 
> Hello Everyone
> Well I got my my URR-74 working after I changed my back panel for 
> one from a WJ-8718.
> However the display does not work, the f and b segments are out on 
> all displays. This looks like
> the U8 on the display board which is a DS8857 however I can not 
> find any data on it on google.
> 
> Am I correct in my logic and someone know what I can use to replace 
> it. your ideas please.
> 
> 73 Lee _______________________________________________
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