[neonixie-l] Heathkit GC-1195 circuit guru question...

['orange_glow_fan' via neonixie-l]

Working on this GC-1195


I need to replace the diodes in the power supply (along with the two 
electrolytic caps. For some reason Heathkit used different diodes for 
(D101,102) and (D103,104). 

D101,102 are three amp diodes while D103,104 are 1 amp diodes. It's my 
intention to use three amp diodes (NTE-156) to replace all four diodes. 
Then self doubt crept in and I am questioning my choice.

Is there any reason you can think of that you can think of, other than cost 
savings, that Heathkit engineers used diodes of differing current ratings 
in this full wave bridge? Note that the emitter of Q1 goes off to power the 
incandescent bulbs of the display segments. Q1 is sourced from the center 
tap of the transformer.

So, can I simply use 4 three amp diodes or am I missing something??

Thanks

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[neonixie-l] Heathkit GC-1195...

['orange_glow_fan' via neonixie-l]

I have the above clock. (it lights up more or less orange (Struggling to 
stay on topic..))

It's the grandfathers clock version, that uses filament bulbs for the digit 
segments.

After all these years, it has finally failed. It sits, displaying 12:00, 
and refuses to do anything else. Normally, if there had been a power 
failure, it would display a blinking 12:00. There is no blink.

I can not identify the 40 pin IC. No markings. If I look up the schematic, 
it shows they used one of two ICs, depending on which manual I use. The 
Heathkit part numbers are 443-702 or 443-848. The 443-848 seems to cross to 
a MM5316, the other, 443-702, MAY cross over to a F3817PC. I can find a 
datasheet for the MM5316, but not the F3817PC. 



I guess what I need to know is if they are interchangeableI can locate 
the MM5316, but the F3817PC seems to be made of unobtainium... The MM5316 
actually crosses to an NTE number.

Any thoughts or inspirational advice appreciated...

Kerry

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