NEW APPLICATION FOR OLD COMPUTER POWER SUPPLY BOX

[W2PFY]

While I made this box (transfer switch) up for TV it could be used for many other things as well. Some background: A problem I was having was with a Direct TV satellite TV receiver was that when I would switch from generator power, to battery power, the TV box would have to go through a full boot up and that is about a ten minute process. (No commercial power at my camp)  I didn't know if it would work because of the time delay switching from one source to another but it is working great.

So that's the story but the box since it already has an AC receptacle, it could be used for an antenna change over relay system as well. I found that the 110 volt coil in the relay gets very warm if not outright hot if left on for any extended period, so I also put in a DC supply for the old fan. Not shown are the diodes and cap but it runs the fan on 1/2 voltage or about 8 volts. It is very quiet and keeps the relay cool.

I suppose this is all low tech but no point throwing out a great box for a project.

So what else could you stuff in this box? Perhaps a beacon transmitter, a class D or E rig?
Only your imagination would limit what a reuse for it may be and I would like to hear suggestions.

[K9PNP]

Nothing at all wrong with low tech.  Passes the 'Keep It Simple Stupid' test.

[Opcom]

That's a great way to enclose it. I don't know the ratings for that relay but is it not a high voltage low current unit?

Just saying there's one like that in a 2500V/6KV peak circuit as an AM/CW switch here. In CW, it shorts across the modulation transformer secondary, and the other half changes the screen volts from 400 to 700 for CW. The switch always has power to it when main power is on, so it could be energized continuously.

The coil is frequently buzzing in CW mode (continuous engagement via front panel switch) and I found out it is a 220V coil operated on 110V. It doesn't get hot, but how many of this exact kind of relay can there be? Maybe the builder figured out it was getting hot during long operations and moved it from 220V to 110V power.

Thinking about a more traditional 120V relay, and considering the pull in and drop out times to use the fastest one. One with a strong spring and greedy coil..

Rather than cooling the existing coil, would it operate OK on a reduced voltage?

[w4bfs]

feed it with dc ... usually only requires half voltage and quietens it ..... zzzzzzzzzz purr

[W3GMS]

Terry,

Its great to reuse old stuff into something new! 

So help me out on what your two sources are.  I understand the AC generator source and is your battery source feeding an inverter(s)?  So your switching between your generator source and when it dies, the relay drops and your then powering your stuff from a battery bank feeding and inverter?  I think that is what your doing.  Relays have typically about 8 millisecond of delay, but most hold up time in switching supplies is typically around 20 milliseconds or so.  So the relay switch time is fast enough not to allow the bulk voltage from the switcher to
cause the switching inverter to stop working.  Sounds like you have something that works well! 

Joe, W3GMS

[Opcom]

That's what matters most 8-) 

[W2PFY]

Terry,

Its great to reuse old stuff into something new!  

So help me out on what your two sources are.  I understand the AC generator source and is your battery source feeding an inverter(s)?  So your switching between your generator source and when it dies, the relay drops and your then powering your stuff from a battery bank feeding and inverter?  I think that is what your doing.  Relays have typically about 8 millisecond of delay, but most hold up time in switching supplies is typically around 20 milliseconds or so.  So the relay switch time is fast enough not to allow the bulk voltage from the switcher to
cause the switching inverter to stop working.  Sounds like you have something that works well!  

Joe,
Sorry about not answering your questions promptly but I was away for two days. The two power sources are a 7 KW generator and a 120/24VDC 1500 watt pure sign wave inverter. You have it right, it just switches from one source to the other but I have to remember to turn the inverter back on before I shut the gen set off. I got the deal of the century on three inverters for less than $100.00 each and I suppose that was because of a little less demand for the 24 volt version. Thanks for the switching time data! I thought if this didn't work that I may have been forced to use vacuum relays. Perhaps mercury relays would have worked as well but I didn't think of that until just now.

Patric, those relays are the same ones used in the desk KW and the KW-1 and also look like the ones used in the 610's. I don't think they would be good for much over 3KV.

[W3GMS]

Hi Terry,

Thanks for the clarification.  Its great you developed a effective but simple solution.  Can't beat that!

73,
Joe, GMS

[Opcom]

Patric, those relays are the same ones used in the desk KW and the KW-1 and also look like the ones used in the 610's. I don't think they would be good for much over 3KV.

That's probably good advice. COL Tucker used what was at hand, I guess. I know he used 5500VDC in there before the explosion, so it must have stood that. Good old-time parts. However it should be changed out if it's marginal. The 610 used 2KVDC, right? Don't know the Collins voltages.

What's an appropriate 1952 or earlier style relay to short a modulation transformer secondary and stand 3KV DC / >6KV peak? Some old KW sized BC part? Sort of don't want to put a new-ish Jennings vacuum relay in there and spoil the decor. That relay's 60 years old.. maybe it will last a few more.

[W2PFY]

The 610 used 2KVDC, right? Don't know the Collins voltages.

Actual measurements were 2100 on voice and 2600 on CW. I think the relay shown will work as long as you put it above ground. In the fone position, you could get an arc over if your modulation transformer does not have spark gaps or the gaps are larger than the space between contact on the relay. Only one side of the relay is needed in your application so perhaps the other side would key something else?

Here is the actual part number AT2C115VA RELAY. Mfg Advance.

[N0BST]

At my previous job I used a lot of those cases to build small audio amps using LM386 chips.  I'd use them hooked to my transmitter remote controls so I could hear the unit's robotic voice above the blower noise instead of having my cell phone jammed next to my ear.

Scott Todd

[W2PFY]

At my previous job I used a lot of those cases to build small audio amps using LM386 chips.

Cool, yet another use. I am going to use my remaining Advance relay to build an antenna change over relay. If I come up with a better idea for switching AC power at my camp, that one will also be converted to the antenna change over scheme. I plan to have at least three operating positions up there along with more than one antenna that I am currently operating from.

I keep hearing about how all these hams are so busy since they retired and have no time. Not me! I have a lot of time but I fell into a rut and I need someone with a cattle prod to follow me around and get me to do things

[Opcom]

The 610 used 2KVDC, right? Don't know the Collins voltages.

Actual measurements were 2100 on voice and 2600 on CW. I think the relay shown will work as long as you put it above ground. In the fone position, you could get an arc over if your modulation transformer does not have spark gaps or the gaps are larger than the space between contact on the relay. Only one side of the relay is needed in your application so perhaps the other side would key something else?

Here is the actual part number AT2C115VA RELAY. Mfg Advance.

The other side shorts a dropping resistor in the screen supply for CW. I think the relay is on a phenolic board, it should be checked. B+ is 3K, so it's not much more than 2600V. Good point on the spark gap, it has not been touched at all and not been inspected lately.