Iifl, on the flip slde of this letten is a cincuit schematic fon the finst

Asahi lo Spotmeten cinca -1968.

I obtainod t}e diagrram by tnaclng the cincuit inside the meteF.
Took about an horir! I will e-mail you the .gif file if you rrant.
You can place it on'foun website.
Slrrce mencuql battenies aFe now unavailable fon this meter, I substituted a
slfver"olidp ceff in its place 1 a'892 size silye*ortde eett). Sllveo Oxlde potential ls
| .55 vdc compar.ed to the | .35 vdc 1m*tury cetth ao the needle will r.ead about a
stop.and-a-half high eompared to the oniginal voltage.
The meter cian now be r.ecalibrated by adfusting Rl to a highen nesistance, but
problem is that factor.y potentiometen-Rl is onty eaOO ohms-, and nuns out of
't adjustment nange i wichthe newbattcry wtagil. lt needs about -3s00 ohms, so I
substituted a little lok ten-turn pot in its place, and ne-calibnated the meten
with a gr.ey card and t'hnee othen TTL meters I have her.e. Glose enough.
In onden bflt the mueh-smallen sllver.-oxide eell into the battery compaFtmentr
one has to fabnlcate an alumlnum adapter about the scrne slze as the o"tglnat
batteryr that the new cell llves in. We did it on a metal lathe.
.llrso the meten. has a number of metal-to-motal switch c€ntaets that easlly
oxldize o.ver time and caus6 the ninding to either become erratic or fail
completely.
Theyoxidize from batteryr outgassing ! without guestion, these un.neliable
mechanleal connections are the r,roak point of the design
The way that Asahi engineered the LodHigh switch, the battery.check needs
and the battery tab is neally poon.
( EsPeclelr!fie battery tab. t goGEclean chat one wlth my poeket knife about oncea weekll )
I rronden how many l" spotmeters have been tossed into the dumpstoF due to
this deficit..- Other than thatr it is a manvelously precise instrument,
and is extromely useful fon zone-type photognaphy.

-,. I bought mlne in 1969 and didntt find much use for it until this yean
Now it is the only meten I use.
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