[volt-nuts] Replace neons with LEDs in Fluke 845AB

[David]

Silicon replacements should work fine; I would try the TIP30 or other
low current and slow power transistors like the BD234/BD236/BD238. The
only thing I would worry about is oscillation during switching if the
replacements are too fast and that is something I would check with an
oscilloscope by monitoring the collector waveform.

The transistors operate in saturation so the bias change will be
insignificant; the higher Vbe of silicon will lower the frequency by
about 3%.

I could not find any data on the GA2817 shown in the parts list.  The
minimum Vce in the circuit is double the supply voltage.  I think Ic
is below 100 milliamps.

On Mon, 6 Jun 2016 12:25:32 -0400, you wrote:

>Hi Lou,
>
>It's normal for some leakage in germanium transistors. Do you have a 
>curve tracer?
>If you change them to Si you will have to re-bias them (i.e. R207_8).
>The 84 Hz may change also, might have to adjust C203.
>But should be possible.
>
>Dallas
>
>
>On 6/6/2016 7:33 AM, Lou Amadio wrote:
>> For Dallas Smith
>> Thanks for the info. It is in keeping with the original design.
>> My 845AB 15v supplies are currently down and I suspect the germanium
>> transistors around T202 may be leaky?.
>> Am thinking of replacing them with Si transistors. Your thoughts?
>> Regards, Lou