Dunbar-Nunn Unitrol 800 schematic diagram

APBT

New Member
I'm currently recapping and replacing the TO-3 noise making devices. Any leads to legible copies of the schematics would be appreciated.
 

shues

Lifetime VIP Supporter
There are a few folks on another site who had the manual, albeit more than a decade ago:

@Mike58 appears to be a member both here and there:

The manuals for the x80 series may shed some light:
 
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APBT

APBT

New Member
Shues, that's a very helpful post. Thank you. I spent a lot of time in the past week or so looking for actuals as well as substitutions for that rare matched pair. But my very early, low serial number 800 uses 2N1554 (date code from 1974) rather than SP3099.

Still plugging away at it in between my other projects,
 
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OP
APBT

APBT

New Member
Both 2N1554 TO-3s are toast. Not surprising, as they're old and have many dents. The hunt intensifies.
 

Wailer

Veteran Member
The 800 has a fast rising slow falling wail tone and a fast yelp cycle. The tones are high-pitched somewhat like the 1970s Federal electronic sirens.
 

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