PTT For Viker2

[ve6pg]

..i lost my plate switch on my viker2....so, i am considering adding ptt...ideas?..

..tim..

..sk..

[kb3rdt]

  HI Tim here's one from johnson it on bama site.

http://bama.edebris.com/manuals/johnson/viking2/ptt

[ve6pg]

..what is the voltage ratting fer the relay?

..tim..
..sk..

[w1vtp]

..what is the voltage ratting fer the relay?

..tim..
..sk..

Assuming you have a copy of the Viking 2 manual, look at the bias circuit off V11, the 6AL5.  The output is stated to be -75 volts.  Since the same winding is used except for the different polarity of the rectifier diodes for the PTT circuit, one can assume ≈ 75 volts.  The key here is to note that it's a 10,000 ohm DC relay.  Longer than I wish to admit, I think we used to call them "Plate Sensitive relays" They are very low current draw for the coil.

One more thing: I think I would put an opposite polarity diode across the relay coil to dissipate the back EMF kick from the coil when the PTT is released. These relays might be difficult to find perhaps someone else might recommend a source.  

Al

PS: Why not replace the plate switch?

[ve6pg]

i intend to replace the switch, but along with that was considering ptt..seems between theses 2 vikers, i've replaced 4 in the last 8 yrs, or so..
..tim..

..sk..

[W3GMS]

Tim,
You should be able to use the "HLR" scheme with good success.   Most all of these transmitters can be done in a similar manner. 

one set of relay contacts in series with the voltage going to the screen of the final
one set of relay contacts in series with the screen voltage on the modulator tubes
one set of relay contacts to open up the key line in the VFO
one set of relay contacts in series with the external jack on the back which provides 120V for the antenna TR relay. 

Been using that methodology for years in my Ranger 2 with great success.

Joe, W3GMS   

[K9PNP]

I just added a 9 V AC small transformer from an old wall wart.  Half-wave rectification with a 100 mf filter cap gives enough to power a 12 VDC relay.  I use a 4PDT version which is relatively easy to find.  Even Radio Shack did carry them; hesitate to say they still do the way they change things.  Probably easier to find than the plate circuit relays.

[k7mdo]

Maybe you have seen this but maybe not.  I have the Viking II-CD and it came factory with the PTT relay in place... if you looked at the circuit diagram for it and saw the physical location in the underside of the transmitter it might give you enough ideas to get it done easily...  BAMA has the diagram for said viking and the relay really should be easy to find... I think it is 120 VDC 4 pole, dual throw.

It works really well in the II-CD version.

73, Tom