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On Tue, Mar 5, 2024 at 03:50 AM, Jim Altman wrote:

I was seeing a little arcing from the power switch contacts and installed the SSR with perfect results.? I could tell there was a little arc because the lightning detector on my weather station, only a few feet from the amp, would give me a false positive everytime i turned on the amp. Given the difficulty of finding replacement switches and rebuild kits for the switch, its a nice solution,
73 Jim, W4UCK

Yeah, you only see that "arc" if the switch is closed (or opened) while the voltage is at a peak (sine wave peak)

If you have ever plugged (or unplugged) in any device that's "ON" when you plug it in and have noticed a little spark, flipped a light switch on or off and heard the faint "snap" it likely happened at or near the sine wave peak (positive or negative) and of course,? you do not see that spark or hear it every time.

The trick is to "flip" the switch when the voltage is crossing at or near zero.?

Now maybe there are people that can "see" the sine wave in their heads and are fast enough to flip the switch at the right time,?? and won't need a little additional help getting the timing right.

For the rest of us, an SSR does it nicely.

W8ZR suggested using only one but you can use 2 when powering with 240AC.? (have a look at the )? page 16

You also do not have to use the DC controlled model either.? (Commander 2500 uses AC SSR's)? I am going to use the AC controlled model eliminating the need for a separate (always powered) small DC power supply? Either way, the control "side" of the SSR draws so little current as to be insignificant.

I'll be operating my Loudenboomer (powered by the L-4B plate transformer) on 120AC and always in the "high-voltage" mode. (240 is really not required for a 1kw input amp)? so I'll use one? OPTO22 Model 120A25 in the"hot" side.

For a 240 VAC powered amp, I would use two 240A45 (AC controlled) or? 240D45 (DC controlled) units.

See the link below for specs:?

The key with these is that? they "turn-on" at zero crossing (zero voltage) and give a slight measure of ramp-up in voltage.
I seem to remember that Tom, W8JI said the only reason "step-start" is needed, is to protect the ON/OFF switch.? with an SSR, the voltage on the PS circuits doesn't "slam" on it ramps up at a "sine-wave rate".? The actual current in the SSR control circuit is on the order of mA.

See page 2 of the above publication for the features.

I'm also using a CRYDOM MPDCD3 DC SSR for a keying interface to use with my IC-705 (similar to the OPTO22 DC60MP)? with a double 3v lithium battery holder for complete isolation to protect the IC-705 keying circuit? driving any amplifier.


All the SSR's I have bought so far I have gotten from eBay.? All used.? If you buy them new, they're crazy expensive but there's nothing wrong with used ones.? They either work or they don't.

BE VERY Careful buying the cheap knock-off SSR's.? They frequently have triacs inside that are not rated for the claimed current on the outside of the device.? And if you're going to run them at or near max current ratings, ABSOLUTELY MIND THE HEAT DISSIPATION!!

I'm using a 120V 25A device on my Loudenboomer and will use two 240v 45A devices in my L-4B (The L-4B even at Key-DOWN 1200 W output doesn't pop a 15A breaker.? Mounting to the chassis will likely be more than enough heat sink in the L-4B

Even after many hours the one I mounted in my AC-4 gets only slightly warm using the chassis as a heat sink (I used a little heat grease too)

I do have a small heat sink that I'll probably use in the Loudenboomer.


--

73/Rick

W4XA
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