ART-13 LV PS Problem

[W7SOE]

I received my 20V Antek toroid transformer, which will provide the 28VDC for my ART-13.  I cobbled together a variac, SS bridge rectifier, and put a 40uF cap on the output.  I connected the 28V to the two 28V input pins on the ART-13.

Bringing the variac up slowly the PS output appears to be an only half rectified, or perhaps full rectified with 100% ripple.  ;-)

If I use a large wire wound resistor for a load it works fine.

I have not brought the input all the way up to 120VAC as the ART-13 relays (I am guessing) produce a nasty hum/chatter.

Sheeesh, did not expect to run into trouble with a 28V power supply.   

Ideas welcome.

Rich

[w4bfs]

believe you will need more than 40 uf filter cap ... in the early 60's ARRL handbooks, a method is shown on how to calculate the value req'd ... be glad to help with the rough spots ...73...John

[W1EUJ]

I think a whole lot more - the 28 VDC is for the filaments!

[The Slab Bacon]

The old general "rule of thumb" for chokeless capacitor input filtered low voltage power supplies is generally to use at least 1000uF per amp of output. I have always used this in the past and never ran into problems.

the whole scenario changes dramatically when you add inductors into the equation.

                                                        the Slab Bacon

[W7SOE]

Ahh, ok, that makes sense.  I will try strapping on some big caps tonight.  Big load, big caps...

The trouble is that, in the day gig, I work with big voltages of 1.8V and loads as big as 80mA....

Thanks

Rich

[KB2WIG]

For whatt it worth, do you have the book on the '13??  

It's possible (more probable) that the chatter you are hearing is the auto tune trying to  'find' one of the pre-programed frequencies. If you dont have close to 28 V, the motor may not like the load. Also, the grease in these things may be 40+ years old...   slows down the chain drive.

Try pulling the 813 and 811's out of their sockets to reduce the load on your pwr supply and see what goes on.. For that matter , run it without any tubes in it and see if the auto tune finds a place..  around 30s or a bit less at 28V

My advice is to get the Electric Radio issues for this thing.........

klc

[W7SOE]

For whatt it worth, do you have the book on the '13?? 

It's possible (more probable) that the chatter you are hearing is the auto tune trying to  'find' one of the pre-programed frequencies. If you dont have close to 28 V, the motor may not like the load. Also, the grease in these things may be 40+ years old...   slows down the chain drive.

Try pulling the 813 and 811's out of their sockets to reduce the load on your pwr supply and see what goes on.. For that matter , run it without any tubes in it and see if the auto tune finds a place..  around 30s or a bit less at 28V

My advice is to get the Electric Radio issues for this thing.........

klc

I do have the book.  I have run the rig on 28V provided by an old heathkit "battery eliminator".  (This after giving the transmitter a complete cleanup and lube).

The auto-tune works great!  So much fun to watch it go.

Rich

[KF9CM]

I used a 4000 uf cap at 35 vdc with a 10k bleeder in my power supply.
You can check it out at www.kf9cm.com

de Gary,KF9CM

[W7SOE]

I used a 4000 uf cap at 35 vdc with a 10k bleeder in my power supply.
You can check it out at www.kf9cm.com

de Gary,KF9CM

Thanks Gary.  Did your 28V bridge rectifier require a heatsink?

Rich

[KF9CM]

I mounted it on the chassis and with some heat-sink compound, it seems to be ample enough to do the job.


73 de Gary,KF9CM

[WU2D]

Gary,

Yes use as much C as you can get. I improved the regulation of my ART 28V supply by making a high current choke which I inserted before the 10,000 uF Capacitor and bleeder. I took an E core from a discarded 5 Amp Realistic transformer that I hacksawed all of the turns off. I then wrapped the core in tape. Then I took as much # 12 enamelled wire as I could fit and wound it on the form and gooped the whole thing. This Choke Input idea made a big difference with the voltage swinging up and down and brought the resting voltage down to a safer level for the Fart-13.

Mike WU2D

[KE6DF]

I stumbled across a freeware program for analyzing power supplies. You can plug in the parameters for an ART-13 supply and it will help you decide on filter capacitors, transformers, and chokes. It will give you graphs showing output voltage and ripple under various loads.

http://www.duncanamps.com/psud2/index.html

This guy has a bunch of other free software (and a few programs for sale). So far I've tried this one, plus another program that locates tube datasheets. Both seem to work OK.

[TedN]

Rich:
My 28V cap is 47,000. Bridge same as Gary's no heat sink.

Ted

[W7SOE]

Thanks all for the help.

I am getting much better results using 10000 uF.  Still ~2Vpp of ripple under load, none with no load.  Tried making a choke by winding ~20ft of heavy enameled wire on a large ferrite toroid.  Place inline, after the bridge, before the cap, it had little effect....


Rich

[WU2D]

Rich,

That says that it is not many mH. Unless the torroid happens to be the right material, it will not have much of an inductive effect at 120 Hz. Try a laminated iron core from a choke or transformer that is made to work at 60 Hz..

Mike WU2D

[W7SOE]

Rich,

That says that it is not many mH. Unless the torroid happens to be the right material, it will not have much of an inductive effect at 120 Hz. Try a laminated iron core from a choke or transformer that is made to work at 60 Hz..

Mike WU2D

OK Mike,  I will find a transformer to dismantle and report back.

Rich