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Title: PTT relay for Viking II Post by: WV9R on January 25, 2009, 07:51:17 PM Hi all, I'm looking at doing the PTT mod to my Viking II, I have the schematic for the Johnson mod. Of course the relay mentioned is no longer available, at least I havent been able to find it if it is. Can someone point me in the right direction to get a relay that will work for this? I'd greatly appreciate it. ???
Title: Re: PTT relay for Viking II Post by: Steve - WB3HUZ on January 25, 2009, 07:52:43 PM What are the specs? Or can you post the schematic?
Title: Re: PTT relay for Viking II Post by: WV9R on January 25, 2009, 08:00:38 PM here is the schematic, at least I hope it shows up , it's the one off of the AM Window. It's a 10K coil and activates at 200ma, if the info I was able to find is correct. Thanks !
Title: Re: PTT relay for Viking II Post by: WQ9E on January 25, 2009, 08:35:40 PM Suitable relays are still available new such as the model from Mouser: http://www.mouser.com/Search/ProductDetail.aspx?qs=sGAEpiMZZMtSzCF3XBhmW8aDEVUWqbwomQ9p0uhaKHE%3d
It is a DPDT unit (15 amp contacts) with an 11K coil (normally designed for 110V DC operation). There are others available but this is one I have used before, it is around $8 in single unit quantity. Rodger WQ9E Title: Re: PTT relay for Viking II Post by: WA1GFZ on January 25, 2009, 08:53:45 PM V2 added 2 diodes and a cap to generate a positive voltage off the bias winding to make around 110 VDC. The contacts are in parallel with the TX front panel switch. The low side of the coil connects to the mic connector ptt input. ground to TX. High side 0f the coil goes to the positive 110 VDC. You will still need an antenna relay controlled by 115 VAC primary of the hV transformer.
Title: Re: PTT relay for Viking II Post by: Steve - WB3HUZ on January 25, 2009, 08:56:02 PM Yep. That high coil resistance is needed to drop the voltage down so there is only a few volts on the PTT switch. If you can find such a relay, just build a simple half-wave rectifier off the filament line and use a 6 or 12 VDC relay.
Title: Re: PTT relay for Viking II Post by: WA1GFZ on January 25, 2009, 09:03:15 PM PTT voltage will be 110 VDC with the contact open so it is actually a safer idea to use a lower voltage. A small transformer could be mounted on the chassis side wall or rectify the 6.3 VAC. The coil resistance is to only limit current on the ptt line once shorted. Not sure how much of a shock you will get if you happen to grab hold of it. Don't use AC or it will get into mic audio.
Title: Re: PTT relay for Viking II Post by: W3NP on January 25, 2009, 09:16:10 PM When adding PTT to any older rig, I usually just use a 12vdc relay and power it with a simple voltage doubler off of the 6.3v filament line. Most 12v relays will pull in reliably at 9v or so. I jerked out the "stock" PTT relay in my Ranger and used this system - same as in my Viking II.
Title: Re: PTT relay for Viking II Post by: KM1H on January 31, 2009, 06:19:06 PM How did Johnson do it in the VikingII CD model?
Carl KM1H Title: Re: PTT relay for Viking II Post by: WA1GFZ on January 31, 2009, 06:32:26 PM CD, As I said. They mounted 2 diodes and a cap to make positive 110 VAC for the relay. The low side goes to the mic connector and the contacts are in parallel with the front panel TX switch. IF I was adding one to a rig I would use a lower voltage coil and maybe rectify the heater voltage. You need heavy duty contacts on the HV primary. They spark pretty well.
Title: Re: PTT relay for Viking II Post by: W7SOE on January 31, 2009, 10:36:42 PM When adding PTT to any older rig, I usually just use a 12vdc relay and power it with a simple voltage doubler off of the 6.3v filament line. Most 12v relays will pull in reliably at 9v or so. I jerked out the "stock" PTT relay in my Ranger and used this system - same as in my Viking II. This is what I did in my Viking II, very simple, works great. There is a schematic out ther somewhere, look at BAMA.... Rich Title: Re: PTT relay for Viking II Post by: W1RKW on February 01, 2009, 08:47:37 AM I took a very minimal approach with my V2. Used a 12vdc wall wart, 12v relay with suitable contacts and a momentary switch.
Title: Re: PTT relay for Viking II Post by: KB3DKS on February 03, 2009, 01:40:05 AM In my Viking II used a 110/220VAC 20A solid-state relay (black square brick), which requires only 3 to 27VDC max to switch on the AC. The back of it is metal and acts as a heat sink and it only has 4 terminals. 2 terms (SPST) to switch on the hot side of the plate transformer’s primary, etc. and the other 2 terms are for the DC control. These relays can be found in most electronics catalogs and online stores. Mouser, Allied, Newark, etc. Makes for a really simple PTT mod. Just make sure that you have the SSR wired after the main power switch as a failsafe ! The failure mode of those bricks is shorted ON !. They should never be used as a main power control without a normal backup in line. Otherwise they work fine. I have installed several commercial sound systems using 40 amp rated SSR's for simple dumb operator single button or keyswitch power up. The racks had locked doors to prevent any unauthorized changes. If buying these surplus make sure that they are of the zero crossing type, most common, as they are also available for use as phase control dimmers/speed controls and need an AC line sync'd square wave control voltage. I use a small 2 amp block to power the 110V AC Dow Key when operating a transmitter other than the killer VKII's. Once my shack is set up again will standardize the relay control voltages to something normal like 12-24 or so depending on what I have the most relays for. Bill, KB3DKS in 1 Land |