dc to dc voltage converter

[K5IIA]

http://www.ebay.com/itm/DC-400W-6-40V-12v-24V-to-8v-80v-10A-Boost-Converter-Step-up-Module-Power-Supply-/331591960238?hash=item4d346bc6ae:g:MrcAAOSwu4BVjdVC

I need to get 300vdc to run the Viking mobile transmitter I bought from the for sale section and was wondering if I can buy a few of these units and parallel the low voltage side and series up the higher voltage side for an increase in voltage.

seems kinda far fetched but man sure would be sweet if it is possible.

[KA2DZT]

What other ideas do you have??  Must be a better way to do it.

[K5IIA]

What other ideas do you have??  Must be a better way to do it.

someone email me and tell me they have the dyno motor or what ever it is called to run it, or buy a low power high quality dc to 120vac converter and build a power supply with regular iron.  Both of those seem to be a lot of work to me.

I figured if the dc to dc converters in series wouldn't blow up it would be the easiest, but that is why I asked here to see what people thought with more experience.

[Opcom]

The eBay item is not isolated input to output.  How many mA are required at 300V?

You can use a cheap 12V to 120VAC inverter at 60Hz and follow that with a voltage multiplier. Since the output waveform of the inverter is more like a square than sine wave, the voltage doubler or multiplier may work. The caveat is to not trip the overcurrent on the inverter by having too large a capacitance. If you use a cockroft walton multiplier where all the caps are effectively in series this should do well. schematic: https://en.wikipedia.org/wiki/File:Full_wave_Cockcroft_Walton_Voltage_multiplier.png in the wikipdia article for cockroft walton

If all you want is 300V then a simple voltage doubler or tripler may do. oversize your inverter 3-5x for best results. They are cheap. I say tripler because many inverters don't make the 150V peak voltage but a bit less.

As for dynamotors, yes that is a perfect way to do it if needs are modest. If an output voltage is high, the usual regulation methods work well. A buck converter with adjustable output is good. please note that a 150W or bigger dynamotor needs a big relay. I used a pair of Bosch 30A relays on my 60W/channel tube type car stereo power amp, which employs two 400V 200mA units, one for each channel to power push pull 6146s.

Attached is a list in both an image with stacked data and the excel sheet of many columns. They are available at a relative pittance for nice people who will not scrap them.  They have been briefly checked but not relubricated and cleaned, which you must do. it is easy. PM if interested.

[Opcom]

I would be willing to clean and relube it if you don't want to. It's something I have done lots of times. Usually i use a lithium grease but it depends on the bearings,.

Here is a general  dynamotor list that may be helpful to many.

[VE3LYX]

When I first fired up the No 19 transceiver I used a vibrator supply i cut frm a junked 50s Ford car radio. it ran the low hi vltage fine for the whole rig then i piggybacked a another supply to it to get the PA final 450 to 525 volts and it worked fine. In fact some who worked me when i first got it worked me on that. I have tried the inverter supplies but their auto shutdown gets in the way all the time In fact we had a power outage yesterday and I was trying to keep a sked using an old H tube rig so I dragged out the inverter doubler. with in minutes it ws cycling on and off and they are very dirty.. Vib supplies dont have such issues. They work till the filaments get too cool to operate and are much cleaner then modern inverters. So Ur original concept is usable. Ur not crazy.
donVE3LYX

[KD6VXI]

Grab a tubed Cb amp for the mobile off eBay.   Your switching transistors and transformer,  rectifier,  etc are all their.

Usually they used a doubler to get the 350-400 volts out of the  transformer up to get the sweep tubes to sing.

PAL, Palomar,  Maco,  blackcat.   All names you can eBay.

--Shane
KD6VXI

[PA0NVD]

How many mills you need at 300 VDC?
I made many small DC - DC converters and it is really very simpel. Winding a core wit approx 2 turns per volt isn't much work either. You  get approx 100 Watts out off an 1 cub inch transformer, so no need for big ferrite cores. 

[KC4VWU]

Exactly what I was thinking, snag a largish mobile CB amp parts unit from the bay or a fest. Most times, after they roast the tubes, the CB guys are reluctant to buy new ones and the amp is offered up for cheap and still usable. Either that, or get up with Patrick about a dynamotor. After a cleaning and re-lube, they're almost bulletproof. There's just no free lunch on this one.

Looking at the specs, 300v@200mA will ballpark at around 18w out. You'd really need to almost double that to get closer to the 50w mark.

[Opcom]

Second the notion of the CB amp DC DC converter. They still seem overpriced even with the inevitable bad tubes, I guess the CBers are hard up for any kind of amp and have to pay through the nose. Be aware the transistors are nearly always germanium and must not be overheated. They also tend to be PNP so the polarity looks funny. Overheating for germanium is only 'warm' for modern silicon, pls. check the data sheets. Some old CB amps use an EI laminated transformer running 60-200hz. Others use a more modern toroidal unit at 1-3Khz. Lots of choices. The larger amps I still have in the collection often use a doubler to make 600-700V on "HI" and half that on "LO" by means of a switch on the secondary side. I don't sell them or use them on the air. Converting to silicon transistors is a can of worms. They are just something to collect and tinker with/fix up when bored.

[RolandSWL]

I took a look through an old Johnson catalog and found a picture of the original dynamotor power supply. The output rating of the P.S. was 500Vdc at 200ma.

It had a big honking power resistor which adjusted the output voltage by means of a slider. It sure would be easier to get your hands on the original supply.



RSWL......

http://www.smecc.org/amateur_radio/JohnsonCatalog975.pdf

Look under Dynamotor.



[Chuck SWL]

I'm new to this forum so bear with me. I'm not familiar with the Johnson gear you are trying to power up, but if all you need is 300VDC at 200ma and you have access to 115VAC for the input you could probably do with a high power linear supply in place of a dynamotor. Perhaps something like this:

http://www.ebay.com/itm/Mid-Eastern-Industries-HV350-1A-SPC251-DC-Power-Supply-500V-/141859846945?hash=item2107817b21:g:vY8AAOSwhkRWewMH

Attached is a data sheet for the series

[K5IIA]

yea, I am going to be putting the Viking mobile in the mobile and yes one option would be to just get a 120vac supply and do it what I guess could be called the regular way as if it was at the house with transformers and all that, I was just hoping that the little dc to dc converters in series may be a nice easy way to do it but looks to not be the case.

I believe I may have a lead on a dynamotor that will fit the bill and go ahead and keep it vintage all the way.

thanks for the input

k5iia

[WB6NVH]

The most common dynamotor that hams used in the day was the PE 103, a military surplus unit originally used with the BC-654 field radio.  500V, rated at something like 160 ma but would do more.  6 or 12V jumper selected input.   Big ugly olive drab thing.   Still quite common at western hamfests, not sure elsewhere.  A few years ago you couldn't give them away but now the military re-enactors want them to put into their Jeeps and demand is starting up. 

I use a dynamotor from a scrap GE police radio of the early 1950's. 

Oh, and also, there are quite a few TCS naval transmitter 12V dynamotors showing up at the hamfests and on eBay lately, for some reason.  Many are unused.