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 Post subject: ABC battery eliminator kit K-101A
PostPosted: Nov Thu 07, 2019 6:53 pm 
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I just finished the battery eliminator kit K101A from Antique Electronic Supply and it came on with no problems except the B voltages are off: 22V is 25.5, 45V is 48.5, 67V is 71.5, 90V is 94.6, ?V is 118, 135V is 141. My radio is a Philco 38-38. Will these voltage differences cause any problems? Thanks in advance!


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 Post subject: Re: ABC battery eliminator kit K-101A
PostPosted: Nov Thu 07, 2019 9:11 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Bristol TN 37620
The slight differences in voltage shouldn't affect your set. the B string is not adjustable
as the A and C strings are. Check the volts after the radio is running. The load will
probably take it down to the stated levels.


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 Post subject: Re: ABC battery eliminator kit K-101A
PostPosted: Nov Thu 07, 2019 11:38 pm 
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If you use a power supply disconnect the 900ohm resistor...
viewtopic.php?p=3011902#p3011902

Greg.


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 Post subject: Re: ABC battery eliminator kit K-101A
PostPosted: Nov Sat 09, 2019 1:26 am 
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Thanks for the replies! Funny thing is I just replaced the 900ohm res cause the original was cooked. I'll disconnect. So the PS only has one C voltage connection (2V adjustable). Do I understand that I will still need to use a battery for the other C voltage of -9V that is required?


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 Post subject: Re: ABC battery eliminator kit K-101A
PostPosted: Nov Sat 09, 2019 3:15 am 
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Location: Minneapolis, MN USA
The B string voltages vary slightly from nominal because they are determined by the zener diodes. Those zener diodes have a voltage spec where the output voltage will vary by a plus/minus percentage. The zener diodes are in series so each contributes to an overall net variance from the nominal rating.


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 Post subject: Re: ABC battery eliminator kit K-101A
PostPosted: Nov Sat 09, 2019 3:11 pm 
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It seems a shame to use batteris for the -9V with all those extra voltage outputs on the PS. Can't I just use the 22V output divided in half (accepting the extra 2V) or maybe use a DC converter?


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 Post subject: Re: ABC battery eliminator kit K-101A
PostPosted: Nov Sat 09, 2019 4:17 pm 
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Follow the link at the top of this post...
viewtopic.php?p=3013805#p3013805

and see (in blue, on the schematic) arf member Burdawg's Voltage divider network modification.

Greg.


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 Post subject: Re: ABC battery eliminator kit K-101A
PostPosted: Nov Sat 09, 2019 5:13 pm 
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Location: Keystone Heights, FL, USA 32656
Maybe something like this would work?
Attachment:
DSC03877.JPG
DSC03877.JPG [ 296.7 KiB | Viewed 5953 times ]

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 Post subject: Re: ABC battery eliminator kit K-101A
PostPosted: Nov Fri 15, 2019 9:30 pm 
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Okay I now have all the required voltages. One more question before I turn it on: On the schematic for my Philco 38-38 one of the lines is "B+ , C-". This means those are tied together at the PS? Since they are from two xfmrs isolated from each other that is okay, am I correct?
Thanks.


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 Post subject: Re: ABC battery eliminator kit K-101A
PostPosted: Nov Fri 15, 2019 11:48 pm 
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They doesn’t sound right. Don’t do it.
What diagram are you looking at that shows B+ and C- on the “same line”?

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“Nothin’s worth nothin ‘till somebody wants it.”—Irv Metter


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 Post subject: Re: ABC battery eliminator kit K-101A
PostPosted: Nov Sat 16, 2019 12:18 am 
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Philco 38-38 schematic→ viewtopic.php?p=3011902#p3011902
Image
Greg.


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 Post subject: Re: ABC battery eliminator kit K-101A
PostPosted: Nov Sat 16, 2019 1:26 am 
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I built the same K-101A battery eliminator kit for my Coronado 650 and the kit had adjustable pots allowing me to dial in the ABC voltage right where my Coronado needed them. It's still working great a few years later. Here's the radio.


Attachments:
Coronado_650_front.jpg
Coronado_650_front.jpg [ 175.6 KiB | Viewed 5799 times ]

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 Post subject: Re: ABC battery eliminator kit K-101A
PostPosted: Nov Sat 16, 2019 4:33 pm 
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Location: Keystone Heights, FL, USA 32656
B- C+ wire is NOT connected where it crosses B+90.
Attachment:
Untitled-01.jpg
Untitled-01.jpg [ 120.82 KiB | Viewed 5766 times ]

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“Nothin’s worth nothin ‘till somebody wants it.”—Irv Metter


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 Post subject: Re: ABC battery eliminator kit K-101A
PostPosted: Nov Sat 16, 2019 5:03 pm 
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Old schematics can be a problem to read. The connection dots can be hard to read, and worse, wires crossing but not connected often look like they are connected. When I draw my own schematics I use the little "jump over" symbol (don't know the tech name.) and a big dot for connections..
An old RCA schematic left no doubt.


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rsz_untitled.jpg
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 Post subject: Re: ABC battery eliminator kit K-101A
PostPosted: Nov Sat 16, 2019 5:56 pm 
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If you would like a high-resolution scan of the service manual, let me know.
Image
Greg.


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 Post subject: Re: ABC battery eliminator kit K-101A
PostPosted: Nov Sat 16, 2019 7:39 pm 
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I appreciate everyone trying to help, be patient my skull is thick. There's actually two things I'm not sure about. The B-, C+ wire: Where does it connect on the power supply? The other is more curiosity. I've been told a couple of times to disconnect the 900ohm resistor because I'm using a power supply. Why is that?
Thanks all.


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 Post subject: Re: ABC battery eliminator kit K-101A
PostPosted: Nov Sat 16, 2019 8:39 pm 
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Location: Mountains of Mourne. Ireland.
Burdawg wrote: If you use a power supply disconnect the 900ohm resistor (item 38 on the Rider's schematic) that drops the C- voltage down to -9V

This was put in with the battery pack in mind which had a single C output. I just finished a 37-623 console that has this same power supply. The power supply that AES sells is a good source for this type of radio. Build it on a small breadboard instead of the wood board. I built one using a gutted out AT style computer power supply case (I find these to be good free project boxes).

I modified the C output by not using the adjustable pot and just using a voltage divider network, since the C supply doesn't need to supply any appreciable current. I have -3, -9, -12V available.

Put an old tube socket on the case to provide a connection point (or a terminal strip) and you have a good general purpose power supply for this type of battery radio.
Image
Just replace the 50K pot with a voltage divider network of 6.8K, 13K, and 30K (in that order) wired in series from the C+ terminal to the low side of the C supply. The network will still be about 50K so the load on the C supply will be about the same.

Connect the C+ terminal to B- to reference the C supply to B-. Then you will have -3V at the junction of the 6.8K and 13K resistors, and -9V at the junction of the 13K and 30K resistors, referenced to C+. I said earlier that I also had -12V but forgot that I eliminated that to make it simpler.

You could always play around with the values to get other C voltages if needed. Remember to disconnect that 900ohm resistor or it will load the supply and the voltages won't be right.

Complete discussion here: viewtopic.php?p=261456#p261456

My skull is thick too... :)
Greg.

The 50K pot is R7 on the AES power supply schematic.
The voltage divider network modification is shown in blue above.

B- and C+ connections can be seen here - - prior to removing the 50K pot (potentiometer) as mentioned above.
viewtopic.php?p=3011913#p3011913


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 Post subject: Re: ABC battery eliminator kit K-101A
PostPosted: Nov Sat 16, 2019 9:06 pm 
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Joined: May Sat 30, 2015 11:49 pm
Posts: 942
Location: Keystone Heights, FL, USA 32656
On the AES supply run a jumper from C+ to B-. Then, using Greg's colors, connect yellow to B-.
Then, looking at the diagram, when the radio is switched ON, A-, B-, and C+ are all connected together.
Also, the C- is switched to ground through the 900 ohm resistor, which will load the C voltage down, probably to zero. That is why the 900 ohm resistor needs to be left out of circuit.

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“Nothin’s worth nothin ‘till somebody wants it.”—Irv Metter


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 Post subject: Re: ABC battery eliminator kit K-101A
PostPosted: Nov Sat 16, 2019 10:25 pm 
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Okay - here we go!
Thanks.


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 Post subject: Re: ABC battery eliminator kit K-101A
PostPosted: Nov Sun 17, 2019 3:04 am 
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