[ARC5] SCR-274N Dynamotor Question

[Mark K3MSB]

Problem solved!

I initially looked at purchasing a used MIL 28V power supply such as the
PP-8474G. They are on eBay but total cost with shipping would be around
$450. So, that option is out.

I then decided to purchase #6 cable. Well, you need the connectors,
standoffs etc and that was around $75.  I almost pulled the trigger... but
$75 is a lot of money.

What kept lurking in the back of my mind is that Chris and Scott kept
telling me they use floated batteries across a 28V supply and it works
great.  I tried that and it didn't work very well at all. I decided to
revisit this option and emailed them.

Chris got back to me right away.  I have an Astron LSRM-25A-BB 28V power
supply (18A 25A ICS) with battery backup output. I had my 12V tractor
batteries (2 in series) across the battery backup terminals as that's what
I was told to use. That was my mistake.  They need to go across the main
28V output terminals.

Chris also cautioned me that the batteries need to be fully charged before
each use and disconnected after each use.  I charged the batteries and put
them across the main 28V output.... and Wow!   It worked great!

Key up voltage was 27.9 and key down was maybe 0.1 volts lower.  The plate
voltage on the ARC-5s is now about 560V and my power output is 50W !!

The chirp is almost completely gone.

Cost: $0 – which ain't too bad!

73 Mark K3MSB
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