Discussion in 'Technical' started by W6MQI, May 20, 2016.
Thanks Dave that is exactly what I was looking for.
Ok Frank,,I see Dave gave you the normal functioning when your power supply imitates the original dynamotor supply.
Mines the same.
K1 turns on all 28vdc to the radio when you switch Emissions from OFF to any mode
B+ (via K2 relay operating) is only turned in when you turn to VOICE mode AND you operate PTT ,or hold the TEST switch .
B+ (by the same K2 relay) turns on as soon as you turn to the CW or MCW mode.
Note: B+ (via K2) will turn on if you switch the FUNCTION switch to CALIBRATE.
K2 is also always controlled by the interlock safety switch on the lid. Opening the lid will drop out K2 in the power supply and kill ac to the high voltage transformers.
My K3 relay and K4 time delay relays are used to slowwwly apply AC to the 400 and 1200 volt supplies.
The large value electrolytics in the supplies and the low forward resistances of the diodes will give a LARGE inrush current for the time it first charges the caps .
With tube rectifiers and low value oil filled caps in the old day power supplies...None of that was needed, except when we used 866 mercury vapor rectifiers.You had to heat up the filaments for a minute before applying high voltage.
Most of the commercial transmitters and stuff we worked on in the service used Ampetite thermal time delay relays for this.
Anyway on this supply, energizing K2 supplies ac to the 40 watt light bulb (and the coil of timing relay K4) and THAT LOWERED AC through the light bulb onto the transformers.The bulb will first glow almost full brilliance from the inrush current to the caps.In a tenth of a second it will get dim, indicating the capacitors are charged.Then K3a shorts out the bulb and the transformers get full line voltage.
K3 is operated by K4, the inexpensive Omron adjustable time delay relay.The time can be set to a half second or more.You dont need much delay.
I had a spare contact from K3, K3b which I used to open the 400 volts to the radio as another safety feature.
I should do the same to the 1200 volts , but ran out of contacts with high enough voltage rating.
Thats pretty much it.
The 15 ohm resistor in the negative return of the 1200vokt supply is the meter shunt for the plate current meter in the ART13.
The 15ohms will give you close to a 200 milliamp full scale reading.I put the 100ohm rheostat across it and set the meter to read 400 milliamps full scale.
With only a 200 milliamp meter , in AM fully modulated , at times the meter will peg on voice peaks.So,I increased the full scale read to double.
My ART-13 doesn't have an interlock switch do you know if yours is a late model or early modal? Found a stamp noting 1942 in my unit also the modulation transformer is an early version as well so Henry seems to think mine is an early version I'm wondering if the early units didn't have interlock switches?
Mine is an ATC, so no ART-13 designation at all. No interlock and the early modulator with the 12SJ7 tubes and the 200khz plug in Crystal.
Yes, then yours is the early version.That is kind of neat to know!
So now you REALLY have to watch your fingers.
Operation will be the same,
I dont know what year this one is Dave.
By my serial number, with the CZR designation , Henry says its Zenith radio.
It does have the later model mod transformer, so I can only assume its post 44.
Did you see my post in regards to the article you found in ER on the b+ keying modif to the radio?
I almost only use cw and was making a board to do the same thing..Keying the 400 volts in the power supply..But I like the info he had on the source of chirp.
Did you try any keying mods.?
Zenith that's different learn something everyday never knew Zenith contracted to build the ART-13
No never did I kinda gave up on the idea of using the ART-13 for any CW operation, I found the transmitter too clunky to QSY and line up on CW stations. CW stations with tight filters like to yell at you if your not exactly on their frequency guess they don't know what a VFO or RIT is for. If I do ever get another ART-13 someday I may try out the keying mod described by I0JX.
Ok Dave, yeah, I know what you mean...It ain't easy to do a quick QSY.
So far I have been able to "spot" the Art13 in Calibrate with a center position on my external T/R box between the Bc348 and the ART.
Im going to try just keying the 400volts and see what it sounds like...
Was interested to see that your high school ham club had one that wasn't working..
So did we!
I graduated from El Cerrito High School over by Berkeley in 1967.
And your Valiant project...I had to chuckle.Mine was sitting in the basement of my folks place for 50 years since I left.
When the folks passed away and we sold the house, I took the Valiant up to Colfax where it sat in the basement there.
Now its in Reno in the shack and Ive been ordering miscellaneous parts for it as another project.
Or maybe I should drop it off at your place while your on a roll with getting yours all rebuilt