I recently picked up a 39-70 farm radio and am looking to build an all enclosed power supply for it. I found a simple design to build the 90 volt "B" supply, but am wondering if there's a way to modify this schematic to include the "A" supply for the 1.5 volt filament string?
I know you can just use a separate 1.5-volt "D" cell (flashlight battery) to supply the 1.5 but I'd really like to do away with using batteries altogether. If anyone has any idea how to incorporate the 1.5 volt into the above schematic...or any other schematic that has them both... and could sketch it out I would be very grateful.
From the AC line!!! That thing will knock on your backside if you get between B- the earth ground. Wouldn't consider it at all. Try this:
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
(This post was last modified: 12-16-2017, 11:46 PM by Radioroslyn.)
Thanks, Terry. Now I know what he meant! Quick question, what does the * at the far right of the drawing say? Looks like 5 watt but above it is says Total and then 1 but the rest is cut off.
Also the LM317T is not showing up on AES. Is that just a standard pot?
Total of 10K @ 5W. You should have abt a total of 150vdc. Use the two resistor to divide the total voltage down to 90v . Would work out to something 7K and 3K. The 5K pot is used to adjust the A voltage from 1.2v to abt 10v. You could use it to power an old battery set (from the 20's) with 6 tubes or less. The A supply is good for 1.5A. Should probably use some sort of a heat sink for the regulator. The LM317T is a to220 package regulator. Looks like a transistor. They are abt $1.
After looking the 1N4004 will only handle 1a so use two in parallel. Max current thru the regulator is 1.5A which is enough for 6 01a's. By contrast your Philco is abt .2a (200ma)
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
(This post was last modified: 12-17-2017, 12:36 AM by Radioroslyn.)
Ah...thanks again! OK, trying to put together a parts list and what I need to order. Still have a few questions:
1.) What is LM317T, is that supposed to be a center tap choke? I see the 5K pot below it. If so, what value? Does AES have one that won't break the bank? (This was an $18.50 radio purchase! )
2.) I have a diode kit that has the IN4004 and IN4007, but they are super tiny. Do these go by number alone or are there higher amp I should be looking for?
3.) I may have a 10K mfd cap at 20 volts on hand. Would that work? for the 10 V winding?
4.) The two electrolytic caps on the 140 volt winding are both 47 mfd at 250V?
5.) The resistors, 240 ohm and 1000 ohm, would 1 watt be enough?
THANK YOU AGAIN! And no problem, Steve. I just wasn't following what you meant.
1 No http://www.surplus-electronics-sales.com...gLwOfD_BwE
Just grab this off google.
1a don't understand it's 5K (pot) trim pot is fine saw some for under $1.
2 Since you already have the 4000 series diodes I'd just use them. They are good for 1a the last number determines the voltage rating. 4001 is 50v the 4007 is 800-1000v.
3 value isn't particularly critical should be ok.
4 yes
5 The 240 ohm can be a 1/2w there's not much current flow there it's passing thru the regulator. The 1K I just did a quick rough calculation abt 5w
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Thank you!! Sorry for the confusion....I thought at first that LM317T was a choke and I know some of those run $30 or more. We both must've been typing at the same time....saw you edited your first post and it answered that question.
>Found this on AES, will that work?
No not for this. It's a 7815. 78=linear regulator 05= 5v (fixed, nonadjustable).
The LM-317T is an ADJUSTABLE regulator. It has 3 terminals, in, out, and voltage set. You can put up to 37vdc in and adj it down to as low as 1.2vdc. Max current is 1.5a for the T version the K (TO-3 package) will do 3a.
The pot allows you to continuously set your output voltage ANYWHERE from the input voltage (in are case 10v) to 1.2v
You might want to grab a few extras as they are real handy when building lv p/s. I'm not sure how it does it but the output ends up being cleaner (no hum) than the input which may have a little.
On the B supply you could buy a 6-10k power resistor w/an adjustable slider to set the output voltage. Like this one.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
I do not know your current consumption, but some mfrs list max dissipated power, and some don't saying it s internally limited, but everyone gives max op temperature which is usually 125C.
In some Theta-j to Ambient 80C/W, in some 40, not sure if it is with or without heatsink.
But if it is say 80 C/W and you have 1A consumption at 1.5V which is dropped from let's say 7V input at the IN pin of 317, then you have 5.5V dropout tmes 1A which is 5.5W that would create 440 degrees C rise which the 317 will not allow to happen.
So when you see 37Vin and 1.5A I out, it does not mean you can have both (or even lower combinations) at the same time.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
Truth be told most of the times I've used the '317 is w/a 6-7v input. So the voltage drop (dissipation) across it has been minimal. The 1st time was a copy of a circuit out of Popular Electronics back in the 80's. It used the 3A version but powered it w/a 36v transformer for a 6v output. Used a big heatsink and ran hot. I didn't really understand how it worked then and thought it needed the 36v to operate properly. This isn't the case the closer the input voltage is to the output voltage the better the IC likes it and will run cooler.
When I putting this one together I used a small transformer w/a hv winding and a 6.3 filament winding. Nowdays these transformers kind of expensive. That's why I picked the one from AES. It's close to what we need to terms of voltages and current but mostly it's easy to get. The HV side rated @ 200ma which is abt 10X what you need to power any battery set requiring A and B batteries. The divider eats up some of the current @ 6000 ohms it will consume abt 26ma. Still leaves 174ma. On the A side the voltage drop across the IC is about 8v. @ 200ma it's about 1.5w. Worst case is if you didn't heatsink it might overheat but it has a fail safe if it does it goes open till it cools then goes back to normal operation. If this is the case it's simple enough mount the IC to a scrap of aluminum or to the p/s metal chassis. Must use an insulator and some heatsink grease.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
(This post was last modified: 12-17-2017, 01:25 PM by Radioroslyn.)
< Is there anything that could be used with the 317 to dissipate the heat, Terry?
Short answer is I'm not sure, if you are just going to use it for 1.5v farm sets you may not need to put a heatsink on it. @ 1.5w it might not over heat.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
)
