Ampilfone Deflection "fish-hook" diode mod?

kiphartzell

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Ampilfone Deflection "fish-hook" diode mod?

I have a green Amplifone deflection board that I am getting ready to rebuild with suggested mods. Searching the forums and other on-line documentation, I see some potential conflicting information that I hope someone can clarify regarding the "fish-hook" zener diode modification.

The original Atari Field Service bulletin calls for
2 - 1N754A 6.8V Zener Diode
2 - 1N756A 8.2V Zener Diode
Note: Gregg Woodcock's Atari Vector Monitor Repair Upgrade doc reprints the same info from the Field Service bulletin


Michael Kelley's Amplifone HV & Deflection FAQ and Guide calls for
4 - 1N5342B 7.5v 5 watt Zener Diodes (though Ataricade.com points out that 1N5343B is the right part # for the deflection board diode mod (not 1N5342B since 1N5342B is really a 6.8v diode)). I would agree that 1N5343B is the proper choice, if a 7.5v should be used?.

Also, from a Vectorlist archives, I read an append that suggested using 2 x 1N5342 and 2 x 1N5344 for this mod.

So what is the best approach to take? Using a 6.8v/8.2v combination of diodes or all 7.5v diodes?

I have 1N5342B diodes and 1N4738 (Bob Roberts replacement for a 1N756A) diodes in stock. 7.5v diodes would need to be ordered.

For the sake of discussion:
1N754A (0.5w) = 1N5342B (5w) 6.8v zener diodes
1N5343B (5w) 7.5v zener diode
1N756A (0.5w) = 1N4738 (1w)= 1N5344 (5w) 8.2v zener diodes
 
I always used Kellys guide.
You're dealing with zener diodes that are the same wattage. Chances are it'll never see 8.2v and why Kelly suggested using 7.5v instead of the 6.8v because he clearly felt it'll never even see 7.5v either.

So bottom line ALL ar 5W zener diodes. Use 7.5v or 8.2v - doesn't matter.
 
Thanks, I'll go with the 1N5343B 7.5v diodes then. Besides, I'm sure I can come up with a few more items I need to make another Bob Roberts order.....
 
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