Discussion in 'Amateur Radio Amplifiers' started by WA6MHZ, Apr 26, 2017.
I'll scrounge around to see what's in the junque box.
Another change will be the use of a Heavy duty JONES Plug for cabling to the SB-221. In the SB-240, i used a round tube socket like the one found on the HP-23. BUT I want to beef this one up.
I will probably replace the rear panel on the SB-221 with a new assembly for power and RF in and out. I am going to mount the 2 RF RELAYS inside a metal box attached to the rear panel where the transformer was. And I will also put the power I/O in that area too. I might as well go ahead and order the 2 HC-3s and start building the relay box. That will wallop me about $120 just for those!
A few things...
1. I know we talked about this but I don't remember why you want to use an external power supply??
2. You don't need 12V standby power to turn on a contactor, just bring in low current AC (ether 120 or 240 depending now it is jumpered)
3. I would caution against using perfboard, I don't think it will handle the 3000+ volts without developing carbon tracks.
OK the HC-3s are on the way, I am 117.50 poorer. I just love PAY PAL. so easy!
12 or 26.5V coil??
The primary reason for the remote PS is to remove considerable weight to the SB-221. The only place I can put it is on the HIGH SHELF all the way near the ceiling!!! The rest of the shelving is all taken up and nothing can be moved. The Drake L7 and SM-220 and Monitor eat up the big shelf. Just imagine trying to lift a stock 221 onto the top shelf!!! It would crush it too!!! But if it is only 10 pounds it will fit just fine up there.
The reasoning for the 12V is just so I don't have to bring AC to the remote switchbox. AC is dangerous at any location and I don't want have it near where I operate. So I need to find a tiny 12VAC transformer with dual primaries to accept 120VAC or 220VAC depending on the jumpers to run the low voltage stuff. Also a 24 VAC transformer for the HC-3 relays. Or maybe I could use a voltage doubler for running those. Hmmm.....
I don't agree there will be carbon tracks on the perfboard. the perfboard material is completely inert and similar to PCB material, so if PCB holds up under HV, so should perfboard. The only reason it WOULD Conduct is if the Perfboard burns which would create carbon tracks then. So all hot resistors and diodes need to be well off the Perfboard so it doesn't burn it.
I don't use perf anymore, which is why I have a pile of it. The chunks here are clean and dry. If Pat gives them a top coat of lacquer when finished up, do you think it will be OK?
The coils are 26.5VDC. HC-3s are the better relay
according to the seller:
"Brand new Kilovac vacuum relay. Picture shows the 2 that are available but auction and price shown is for one only. Relay was modified at the factory with the addition of ring terminals on each solder lug on the relay. The ring terminals can be removed with simple desoldering. The relay was never installed or used in any way. 26.5vdc coil. SPDT contacts. Shipping is $10.50 priority mail includes insurance. Sold as is, no warranty, no returns. Over the last few years I have sold over 60 of these relays and never had one reported as defective. The primary advantage in using these relays with RF switching is that these can hot switch without damage. HC1 relays are toast if hot switched once. HC1 relays will switch 2ms faster than HC3. 6ms vs 4ms."
Okay good enough...
Better wait on that until you know what coil voltage your vacuum relays are..
The AC is not that dangerous, I wouldn't worry about it....
Your best bet would be to get a small switcher that auto switches between 120 / 240 if you really feel that strongly about not having low current AC in your power / control cable.
I have seen perfboard arc over, and in this day and age nobody uses anything but FR-4 for cheap PC boards, that is your basic fiberglass epoxy board and has a much higher breakdown voltage.
Okay good, your standby power supply should be 28V then, that way you won't be using two power supplies when one will do nicely.
So your control relay will be 28V I have one and will bring it with me tomorrow to SANDARC...