Heathkit GC-1093...(it glows orange..)

[orange_glow_fan]

Hi  

I need suggestions on finding a way to replace the hv driver IC's for this clock. It uses one UHP-480 and a UHP-481, Both appear to be made of unobtainium....

[Grahame]

Hi

Perhaps a couple of SN75468 but the pin outs are different so you will need a small adapter board. Or just discrete parts, again on an adapter.

Grahame

On 08/02/2021 15:38, 'orange_glow_fan' via neonixie-l wrote:

Hi  

I need suggestions on finding a way to replace the hv driver IC's for this clock. It uses one UHP-480 and a UHP-481, Both appear to be made of unobtainium....

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[Ryan B]

There is one for sale on ebay right now. I don't know if it is worth it to you to buy one just to cannibalize the ICs for another...

 https://www.ebay.com/itm/Heathkit-GC-1093-Vintage-Digital-Clock-Tested-/154322501862?_trksid=p2349624.m46890.l49292

Ryan

[Nick]

UHP481 on eBay right now... at a price...

https://www.ebay.co.uk/itm/UHP481-SemiConductor-CASE-DIP16-MAKE-SPRA/164238975574 

[gregebert]

Before delving into expensive replacement, have you done enough troubleshooting to confirm the driver IC is bad ? Those devices are pretty robust, and because they are bipolar (not CMOS), they are not susceptible to ESD damage. You would have to have a rather disastrous event to zap the driver, such as a major voltage spike from the power supply, or the display shorting-out.

Electrolytic caps dry-out and fail over time, and I've even had one short-out.

[jf03...@gmail.com]

If you have enough space, here is what I would do:  I would take a DIP header, some perfboard,  a handful of MPSA92's, and a handful of 10k 1/4 watt resistors and replicate the circuit you show (ignoring the back-biased diode which is probably a parasitic from the monolithic process).  If there were a space problem, I would use some ribbon cable between the header and the perfboard.

[Christian Riise Wagner]

If it's really the driver that's at fault, I'd agree with the above post of making a little replacement board with discrete transistors. They should be MPSA42 though, as MPSA92 are PNP.

[jf03...@gmail.com]

On Tuesday, February 9, 2021 at 11:37:18 AM UTC-8 Christian Riise Wagner wrote:

> They should be MPSA42 though, as MPSA92 are PNP.

Good catch!  I really should know better.