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 Post subject: Re: Ballast replacement. Beyond my pay grade!
PostPosted: Jun Fri 18, 2021 11:07 am 
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Location: Winter Haven, FL
Quote:
So if your line supply was was 120V, half waving produces an effective voltage of 0.707 x 120v = 84.8V, close to what you need for your heater string, you can then get the rms voltage up a little to 94V by trickling through some extra current, by placing a relatively high value resistor across the diode/s. the overall heat loss would be very low.


Since these radios are not played with any regular frequency, would this method be O.K.? Would a resistor increase the current? And if so, what value would be appropriate?

As far as the pilot lamp, I have a lot more 10W resistors than 20W, so wouldn't 2 10W 1.5KΩ in parallel be better than a single 20W, since each would only need to dissapate 1/2 the heat?

I can probably fit 2 10W and 1 20W resistors, along with 2 1N4007's inside the can.

Or should I look at other methods?


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 Post subject: Re: Ballast replacement. Beyond my pay grade!
PostPosted: Jun Fri 18, 2021 7:51 pm 
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Location: La Mesa Califonia
Here is an Excel that does all the math for you. For dial light use #44 bulb and shunt across it with 47 ohm 2 watt resistor.


Attachments:
Vintage Radio Calculations.xls [28 KiB]
Downloaded 29 times
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 Post subject: Re: Ballast replacement. Beyond my pay grade!
PostPosted: Jun Fri 18, 2021 8:32 pm 
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Location: S. Dartmouth MA 02748-1225 USA
Kudos on getting it right.

When is a ballast not a ballast? When it is a barretor :lol:

-------------------------------------------------------------------

I can't find my ballast cross reference at the moment so I ask the "helpful" question...

Are we sure there is no substitution for the b.. (voltage dropping device). If so what brand and its part number. If all there is, is an OEM ballast what is its part number?

I understand it is a 4-pin (standard) tube base... Are the cold resistances known?

I have a couple of bankers boxes full of ballasts, most new, they keep company with vibrators.

I will never use them. If I can get the proper "numbers" for this ballast and I have it, I will send for postage.

Another fellow who may have the correct ballast is Don Sturtzbecker, ARF "dsturtz"

In seeing the corrosion I can guess that it was callous assembly using acid flux without neutralization. You can solder nichrome with plumbers liquid acid flux, then rinse off with hot water. Do not get overly generous with the flux...

>>>> I am editing this post:

Any nichrome connection that gets ~HOT~ cannot be soldered, a crimp sleeve or spot weld must be used, very HOT that sleeve must be Monel.

JFD used a crimp to the nichrome then an extended tab to socket connections. The extension allowed heat to dissipate before reaching the soldered connections in the base.

The universal ballast is rather ingenius. A series of coiled nichrome wire is tapped. Each tap brought to the base. Though the base has but 4 terminals and only three are used, the base has holes and a shunt that shorts all those resistors. To create the correct ballast resistance, the correct shunt is cut. That puts the resistance in between that shunt to use. See the scans of the instructions provided below...

Chas

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Last edited by Chas on Jun Sat 19, 2021 6:36 pm, edited 1 time in total.

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 Post subject: Re: Ballast replacement. Beyond my pay grade!
PostPosted: Jun Fri 18, 2021 8:40 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 6286
Location: Minneapolis, MN USA
Pat,
Yes, you can use two smaller wattage resistors in place of one single resistor.
The total heat developed is the same but reducing dissipation in each resistor will help with their lifespan.
Resistors also have a power rating curve that is de rated as the surface temp climbs. It may be a ten watt resistor at 0 Celcius but only three watts at high temp.
As noted by others, there are other methods to drop xs voltage besides resistors.

the original ballast is an 878r48. There is no known direct sub. The pinout (basing) was published but not the resistance specs. Thus my resistance calcs.


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 Post subject: Re: Ballast replacement. Beyond my pay grade!
PostPosted: Jun Sat 19, 2021 2:29 am 
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Pat,

I found 6 "new" JFD "C" ballasts, boxed :roll:

They have clear signs of corrosion and some paint loss to the perforated shell, none are perfect. Each ballast has a "detailed" instruction sheet, two sides that tells what the internal cold resistance values are. A cross reference, but the desired number is not listed. However, JFD states that the ballast can sub for others by proper cutting of shunts and opting for slightly higher resistance values. The data sheet says it will replace a 23 volt drop, the next level drop is 30 volts. IMHO opting for the 30 volt drop may help with today's higher line voltages.

I don't have the time to confirm if any will work.

The boxes are dry rotted from the paper acid and are falling apart, the instruction sheets are O.K.

I will scan both sides of the instruction sheet and post as a PDF in the next few days.

You can have all six for the postage to your address, USA please. Reimburse the postage please, an SASE will be provided with instructions how to mail CA$H.

They may all work or none work, but the data sheet will help you and others...

What's your pleasure? chas

Now is your chance to become a voltage dropping device expert :mrgreen:

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 Post subject: Re: Ballast replacement. Beyond my pay grade!
PostPosted: Jun Sat 19, 2021 11:20 am 
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Joined: May Sat 23, 2015 3:05 pm
Posts: 666
Location: Winter Haven, FL
Chas wrote:
Pat,

I found 6 "new" JFD "C" ballasts, boxed :roll:

They have clear signs of corrosion and some paint loss to the perforated shell, none are perfect. Each ballast has a "detailed" instruction sheet, two sides that tells what the internal cold resistance values are. A cross reference, but the desired number is not listed. However, JFD states that the ballast can sub for others by proper cutting of shunts and opting for slightly higher resistance values. The data sheet says it will replace a 23 volt drop, the next level drop is 30 volts. IMHO opting for the 30 volt drop may help with today's higher line voltages.

I don't have the time to confirm if any will work.

The boxes are dry rotted from the paper acid and are falling apart, the instruction sheets are O.K.

I will scan both sides of the instruction sheet and post as a PDF in the next few days.

You can have all six for the postage to your address, USA please. Reimburse the postage please, an SASE will be provided with instructions how to mail CA$H.

They may all work or none work, but the data sheet will help you and others...

What's your pleasure? chas

Now is your chance to become a voltage dropping device expert :mrgreen:


Thanks Chas. Got too much else on my plate to spend any more time with this. I installed a 20W 750Ω for the pilot lamp, but after about 10 minutes it got hotter than I would like, so I just took the realistic approach and removed the lamp. Not really necessary.

I then gutted the ballast, and installed ceramic resistors. Still works after about 1/2 hour, and resistors didn't get that hot. Voltages are all very close to what the should be. I suppose tube life may be somewhat shortened if the radio is played all the time, but I don't see that happening.

Think I'll go this route and move on. Thanks all. I learned something here. Hope someone else did, too.


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 Post subject: Re: Ballast replacement. Beyond my pay grade!
PostPosted: Jun Sat 19, 2021 2:22 pm 
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I have learned, some of the stuff I have stored away has turned to junk :x I will still scan the instruction sheet... chas

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 Post subject: Re: Ballast replacement. Beyond my pay grade!
PostPosted: Jun Sat 19, 2021 3:37 pm 
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Joined: May Sat 23, 2015 3:05 pm
Posts: 666
Location: Winter Haven, FL
Chas wrote:
Pat,

I found 6 "new" JFD "C" ballasts, boxed :roll:

They have clear signs of corrosion and some paint loss to the perforated shell, none are perfect. Each ballast has a "detailed" instruction sheet, two sides that tells what the internal cold resistance values are. A cross reference, but the desired number is not listed. However, JFD states that the ballast can sub for others by proper cutting of shunts and opting for slightly higher resistance values. The data sheet says it will replace a 23 volt drop, the next level drop is 30 volts. IMHO opting for the 30 volt drop may help with today's higher line voltages.

I don't have the time to confirm if any will work.

The boxes are dry rotted from the paper acid and are falling apart, the instruction sheets are O.K.

I will scan both sides of the instruction sheet and post as a PDF in the next few days.

You can have all six for the postage to your address, USA please. Reimburse the postage please, an SASE will be provided with instructions how to mail CA$H.

They may all work or none work, but the data sheet will help you and others...

What's your pleasure? chas

Now is your chance to become a voltage dropping device expert :mrgreen:


Think I'll take you up in your offer. Sending a PM.


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 Post subject: Re: Ballast replacement. Beyond my pay grade!
PostPosted: Jun Sat 19, 2021 3:48 pm 
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Going back to Chas's comment: Barretter can be confusing as there is the "Hot wire Barretter" and a Liquid one. These were actually used as detectors when invented around 1903.
The hot wire is the one I described earlier & the detector version used fine Platinum wire and a form of was used for Microwave detection.

Beretter: Started making guns in Italy in 1526. No useable parts for radio.

Part storage, for stuff you can use comes under conservation rules. Moisture & Fauna being the main enemy. A lot of my wrecks & a lot of tubes are stored in a 40ft container, along with some other stuff & some is in a shearing shed. The main enemy is heat with them. Around sixty degrees Celsius is easily achieved in summer, inside one of these things, so you usually leave a bucket of water in there if there is wood that can crack. These containers are vented & in an area that gets wet underfoot when it rains, but they are blocked to give a decent space under them to avoid water issues. It would take a flood of biblical proportions to get them.

Very cheep vermin proof sheds if you have the luxury of room.

Acidic paper is always an issue. I have a couple of books trying to decompose from it. I was at one point, in a lab, contemplating putting it into an atmosphere of ammonia gas.

Marcc


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 Post subject: Re: Ballast replacement. Beyond my pay grade!
PostPosted: Jun Sat 19, 2021 5:25 pm 
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Joined: Jan Sat 16, 2016 4:15 pm
Posts: 343
You could consider a combination of a resistor and a diode for the pilot light as a way to have less heat.

Rebuilding a ballast with resistors inside makes sense and avoids modifying the radio. The heat dissipation with the resistors should be the same as the ballast.

As to tube life, if the voltage across the filaments is the same as with the ballast, there shouldn't be any difference.

Current at turn on is the tube life issue and should be about the same either way. For a radio that is going to be turned on frequently, as Tom pointed out earlier, a capacitor dropper would have considerable advantage.


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 Post subject: Re: Ballast replacement. Beyond my pay grade!
PostPosted: Jun Sat 19, 2021 6:21 pm 
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Location: S. Dartmouth MA 02748-1225 USA
As promised, here are two scans, page 1 and 2 of the JFD ABC type ballast instructions. They are at 300dpi, 600dpi was too large a file :D

Attachment:
JFD_Type_A_B_C_instructions-0001.pdf [1.14 MiB]
Downloaded 23 times

Attachment:
JFD_Type_A_B_C_instructions-0002.pdf [1.09 MiB]
Downloaded 14 times


They can be converted to jpg if need be... chas

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 Post subject: Re: Ballast replacement. Beyond my pay grade!
PostPosted: Jun Sat 19, 2021 8:19 pm 
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Here is a cheap Fan Capacitor. Put the Blue 3 MFD wire in series with a #47 pilot lamp. Put the Red & Yellow 3.5 and 6 MFD wires together to provide 9.5 MFD to feed the tube heaters. Black wire is the common, this could connect to the ballast socket and creates no heat.
https://www.amazon.com/HQRP-Capacitor-H ... 01N6O61EE/


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 Post subject: Re: Ballast replacement. Beyond my pay grade!
PostPosted: Jun Sat 19, 2021 8:56 pm 
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Joined: May Sat 23, 2015 3:05 pm
Posts: 666
Location: Winter Haven, FL
BikenSwim wrote:
Here is a cheap Fan Capacitor. Put the Blue 3 MFD wire in series with a #47 pilot lamp. Put the Red & Yellow 3.5 and 6 MFD wires together to provide 9.5 MFD to feed the tube heaters. Black wire is the common, this could connect to the ballast socket and creates no heat.
https://www.amazon.com/HQRP-Capacitor-H ... 01N6O61EE/


Very interesting. Ever tried it?


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 Post subject: Re: Ballast replacement. Beyond my pay grade!
PostPosted: Jun Sat 19, 2021 9:29 pm 
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Location: San Marcos, CA 92069
I've used 250VAC fan capacitors (CBB61 type) to replace candohm resistors in 4 different radios, and they have worked great. A nice side effect is turn on surge current limiting when using them, as well as no heat wasted.

I use this webpage for calculating the capacitor value. http://www.electronixandmore.com/resour ... index.html

I round up to the nearest value if necessary, as it is better to run the filaments 5 or 10% low than too high a voltage when using a film capacitor to drop the filament current.


Attachments:
File comment: Here are some values I've worked out in the past for 150ma and 300ma tubes.
Capacitor voltage table .png
Capacitor voltage table .png [ 54.57 KiB | Viewed 408 times ]
File comment: Here is an example of using the website calculator I linked to earlier.
Capacitor voltage dropper.PNG
Capacitor voltage dropper.PNG [ 64.76 KiB | Viewed 408 times ]


Last edited by nash on Jun Sat 19, 2021 9:43 pm, edited 1 time in total.
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 Post subject: Re: Ballast replacement. Beyond my pay grade!
PostPosted: Jun Sat 19, 2021 9:37 pm 
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Posts: 666
Location: Winter Haven, FL
nash wrote:
I've used 250VAC fan capacitors (CBB61 type) to replace candohm resistors in 4 different radios, and they have worked great. A nice side effect is turn on surge current limiting when using them, as well as no heat wasted.

I use this webpage for calculating the capacitor value. http://www.electronixandmore.com/resour ... index.html

I round up to the nearest value if necessary, as it is better to run the filaments 5 or 10% low than too high a voltage when using a film capacitor to drop the filament current.

Great info! Thanks. How do you determine "Surge Limiter Voltage Drop"?


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 Post subject: Re: Ballast replacement. Beyond my pay grade!
PostPosted: Jun Sat 19, 2021 9:48 pm 
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I use 0 for the surge limiter voltage drop in the calculator. I don't bother with a surge resistor, and so far have been able to find a capacitor value for the voltage drop I need without one. However, it can be a small value, such as 10 or 20 ohms, to increase the voltage drop to the number you want present in your radio.

I updated my earlier post with a screen shot of the calculator I used to replace the resistive power cord on a 1933 Kadette radio, and a table of values calculated in the past.


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 Post subject: Re: Ballast replacement. Beyond my pay grade!
PostPosted: Jun Sat 19, 2021 11:16 pm 
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The issue with tubes at turn on is that their filament resistance is so much lower than when they are hot.

For the example radio, the filament voltages total 94 volts. At 300 milliamps current, they have a resistance of 313 ohms.

There isn't a lot of hard information about the difference between tube filament cold and hot resistance but it's significant.
Let's suppose the cold filament resistance for this set is 50 ohms.

With a resistor dropper of 90 ohms giving a total resistance of 140 ohms - at 120 volts AC, the initial current will be 850 milliamps.

If you used BikenSwim's recommended capacitor, for the same 50 ohm cold resistance, the initial current would be 420 milliamps.

Restorationnut could measure this set so we could get closer to an actual number.


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 Post subject: Re: Ballast replacement. Beyond my pay grade!
PostPosted: Jun Sun 20, 2021 2:39 am 
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Remember with the instantaneous, or surge current, W = VIt. "t" is often forgotten. There is one device here that has a relay and it controls the surge current by shorting out a series resistor after a time delay.

Marc


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 Post subject: Re: Ballast replacement. Beyond my pay grade!
PostPosted: Jun Thu 24, 2021 9:00 pm 
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O.K. I obtained some JFD type C ballasts. But for the life of me, I can't figure out the shunts to cut based on the following explainations, and the information we already established in order to have the proper voltage drops. The schematic and the existing wiring have the filaments to pin 2, the pilot lamp to pin 4, and the other side of the AC line to pin 1.
Image

Image


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 Post subject: Re: Ballast replacement. Beyond my pay grade!
PostPosted: Jun Thu 24, 2021 11:59 pm 
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Identify the pilot lamp resistance on the JFD "C" ballast and be sure its pin designations agree.

The pix shown indicates to cut the blue and break off pins 2&3 to do so would not complete a circuit for the pilot lamp.

Cut foils can be blob re- soldered, but a cut pin, nope. So do not cut a pin until absolutely sure.

Possibly, a cut pin can be avoided by re-wire of the ballast socket, dunno.

You got 6 chances of getting it right but one and done gives 5 spares :D

When ready to cut a foil, decide what higher resistance to use. I would opt for a resistance that satisfies a 125 volt line or closest to it...

Do test the resistance once the foil is cut to be sure it is still good. I would run the radio up with a variable transformer, so not to risk an incorrect connection, like mixing up pin number, cutting or not cutting the wrong pin, or cutting the wrong foil. The glow for the resistance should be an almost perceptible dull red, but I may be wrong.

Note the cold resistance may not agree with the hot resistance...

I do not trust the JFD chart that says cut two pins and the blue foil... chas

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