[Amps] Alpha 77 snap-disk thermostat replacement

Jim Barber audioguy at q.com
Fri Aug 17 18:03:42 PDT 2012


I'm finally getting around to finishing the latest overhaul on my last 
Alpha 77.
I had the blower rebuilt locally, but since I have everything open I'd 
like to
replace the blower snap-disk thermostat, or "thermal switch" if you will.

The original switch is epoxied onto the metal blower exhaust tube, but 
common
replacements these days have a 2-bolt flange. It won't be difficult to 
adapt, but
I'm left with a question -

Assuming I surface-mount the new switch to the exhaust tube, I can put a 
little
silver-bearing thermal compound between the switch and the tube, then use
a couple of sheet-metal screws to attach it. My actual question is what 
do you
think would be a good temperature to switch the blower from low to high 
speed at?
I've ordered both 100F and 120F switches from an NTE distributor, but 
that's only
based on my armchair guess.

Here's what's available from NTE that close on temperature *rise* at 
140F and below.

NTE-DTC-100
Closes @ 104F
Opens @ 68F

NTE-DTC-120        (this is the one I had planned to use)
Closes @ 122F
Opens @ 95F

NTE-DTC-140
Closes @ 140F
Opens @ 113F
...

Opinions? Options from other sources?

Thanks,
Jim N7CXI



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