grotto2

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Hey guys-

I'd like to light up one of my old tube transmitters.

Does anyone have a plans for a nice modern B+ circuit to generate 67-135V that is small enough to fit in a Tx?

A+ is 1.5V.

-Ron

jfuller

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Hi,

I'm interested too. I am replying so that I too will see any replies.

Thanks,

JamesF

iflyj3

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I may have the schematics for one at home. However, I am on a two week trip that ends in Florida at the Vintage Fly In in Punta Gorda Feb 10/11/12.
I can look on my system at home when I get back if you haven't found any in the mean time. I have one of the supplies that was kitted by ACE in one of my old transmitters.

ggeezer

THE GEEZER HIGH VOLTAGE B+ POWER SUPPLY HACK... Part 1
I too like to use my old tube type transmitters and HV batteries are very expensive if you can find fresh ones. I have found a good solution. I have converted automobile inverters, the type you plug into the cigar lighter and you get out 115VAC. The lowest power units, 75 or 80 watts are the ones I use. I hack out the innards and use only the DC section of the inverter.
The inverters work like this:
....A high frequency chopper, transformer, rectifier and filter converts the 12 VDC input to about 140 VDC.
....The HV DC is then chopped up and assembled by a micro-controller into a pulse-width modulated facsimile of 115VAC.

We only need the DC section of the inverter which provides a clean 120 to 140VDC output depending on load.
Although the inverter is very efficient at max. load it suffers somewhat when you only use 1 to 2 watts like our R/C systems need, but it still is pretty good considering how easy and how much these cost to make.
The inverter running with no load consumes about 130 to 150 milliamps. When you take 10 MA out of the output (1.35 watts), the input jumps to about 250MA.
I power my system with 10 800 MAH AA nicads and I get over 2 hours of continuous use. The hacked inverter and the 10 nicads are smaller in size than two 67.5 volt batteries.
The neat part of this adaptation is that you can get the inverters for less than $20.00 and nicads are pretty cheap now too. I paid $9.95 for my inverters. Bigger nicads or NiMH cells of greater capacity would lengthen the operating time.

I took some photos of what I am doing and was going to write an article but have been busy. If you guys are interested in this hack, it might motivate me to get at it.

Orv.

grotto2

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Lots of interesting ideas here.

ggeezer, Your idea certainly deserves an article. A couple of photos and sketches are probably enough to get us started.

HighPlains

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Simple circuit

http://www.portabletubes.co.uk/sitefiles/ausbatt.htm

ggeezer

I'll start posting the Inverter hack in a day or two as soon as I organize the data.

Orv.

H5487

Ramsey Electronics has a kit [link=http://www.ramseyelectronics.com/cgi-bin/commerce.exe?preadd=action&key=ABCE1]Click ME! Click ME![/link] that replaces the A, B & C batteries but it's a bit pricey at $199. Unfortunately, it's a bench unit only (non-portable). It's a quality kit though. I've built several of their kits and they build, look, and work just fine. They put out a free catalog that fits just fine on the toilet tank.

I think it's neat that you're toying with an old tube rig. My USAF electronics training back in the late '60s was centered around vacuum tube theory.

Harvey

ggeezer

THE GEEZER HIGH VOLTAGE B+ POWER SUPPLY HACK... Part 2

I am going to present my HV power supply hack in a number of posts:

1. I misled you somewhat when I said all my inverter hacks were 75 to 80 watt units, actually the last one I did, which is described here, was a 100 watt Duracell unit. I think what we want to have is the smallest wattage unit that can be purchased because it will have the lowest standby operating current. A search of the Net has turned up a 25 watt unit for $14.00 and I will leave the purchasing decision up to you. Check this out:

http://www.invertersrus.com/inv25w.html

2. The first photo shows the Duracell unit.

3. The second photo shows the innards.

4. The third photo shows the location of some of the important parts. Please see my first post for a description of how these inverters work.

In my next post, I will show what I did to this unit to make it into something we can use to power our tube-type R/C transmitters.

Orv.

All Day Dan

My Feedback: (5)

Thanks Orv, Its and excellent presentation of something that will be very useful. Dan.

ggeezer

THE GEEZER HIGH VOLTAGE B+ POWER SUPPLY HACK... Part 3

Here is the results of some research I have been doing on available mobile inverters:
1. The 25 watt unit from Inverter R Us is no longer available as stated in Part 2.
2. Inverters R Us lists an 85 watt Rally unit (in stock), with a low standby current of less than 100 ma, which would be a good choice for this project:
http://www.invertersrus.com/rally7424.html
3. The 100 watt Duracell unit I'm using has a stand-by current of 164 ma.
4. The Duracell unit also has a 5 volt USB output on a separate PCB. This output is powered by a very efficient switching step-down regulator able to supply 500 ma.
5. Research on the USB regulator indicates that it could be hacked into a power supply to provide voltages of 1.5 to 6 volts for the R/C transmitter's filament supply. Only one or two resistors would have to be changed on the USB board. More experimental work will have to be done to see this through, but it looks very promising. Of course, larger primary nicads or NiMH cells would be needed to power the system.
6. If one wished to have the filament supply option, I have found a low cost, low standby current inverter that looks ideal for the job (Bestek 75 watt):
http://www.amazon.com/BESTEK-inverte...sim_sbs_auto_3

Orv.

ggeezer

THE GEEZER HIGH VOLTAGE B+ POWER SUPPLY HACK... Part 4

This is a continuation of Part #2:

1. After you have removed the inverter innards from the plastic case and cut off or unsoldered the extremities like the cigar lighter plug and in my case, the 5VDC USB board, the inverter is essentially ready to use.
2. My inverter had the 115VAC receptacle clips soldered to the main PCB and these presented a shock or short circuit hazard, so instead of trying to insulate them, I elected to remove them altogether as shown in the first photo below.
3. I also removed the 4 Power Mosfets (these 8 amp,250 volt transistors will come in handy for other projects) which are not needed since we are only using the DC to DC convertor part of this inverter. I also removed the indicator LED to save about 2 ma of battery current. See the second photo below.
4. In order to have the power supply power your transmitter, you have to locate the source of the + high voltage DC. To do this, simply locate the high voltage filter capacitor which is an electrolytic type with a high voltage rating. This is easy because there will be only one on the PCB somewhere. My Duracell unit has a 16 microfarad capacitor with a 250 volt rating. Its location is shown in the third photo below. The negative (-) terminal of this capacitor is connected to the system ground which is the black wire going to the nicad battery. The positive (+) terminal of the capacitor is the positive (+) high voltage DC output. Connect a wire to this terminal on the capacitor or do as I did and solder the wire into a hole left by the removed Mosfet that connects up with the + terminal on the capacitor.
5. Now all you have to do is connect the hacked supply to a 10 cell nicad battery pack through an off-on switch (use the one on the transmitter if you can), black wire to battery negative and large red wire to battery positive. In my case, the thin red wire (+140VDC) will go to the transmitter's B+ input. The transmitter's ground or battery negative also has to go to the black wire from the inverter.
6. My 10 cell AA 1000MAH nicad pack is shown in the fourth photo below.
7. PLEASE BE CAREFUL, YOU CAN GET ONE HECK OF A JOLT FROM THE HIGH VOLTAGE OUTPUT!!!!

Orv.