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 Post subject: BC-348(*) PL-P103
PostPosted: May Sun 10, 2020 6:28 pm 
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Joined: Mar Fri 27, 2020 2:20 pm
Posts: 45
Does anyone know of a reasonable work around the PL-P103 plug for these radios. I am restoring two of them and want to make them nice serviceable table units. I would like to find the plugs, but failing at that, I would be not particularly concerned with keeping the rear connections as they are. The rest of the radios are non modified and are in very good condition and are complete except that the dynamotors are missing. (I seriously doubt that they will be used in a B-24, B-17 or B-29 again anyway.)

Any help with the plugs or a work around idea either way will be appreciated.

HV2010


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 Post subject: Re: BC-348(*) PL-P103
PostPosted: May Sun 10, 2020 8:04 pm 
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Joined: Aug Mon 09, 2010 2:57 am
Posts: 781
Location: York PA.
Several options. Female Spade Connectors or just solder to the lugs.

I don't know if that help you or not, your question is rather general. Do you plan on using the 348 in conjunction with a transmitter, or just as a stand alone receiver? The first requires you to mute/unmute the receiver which is controlled by two of the lugs. How are you powering the radio?

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 Post subject: Re: BC-348(*) PL-P103
PostPosted: May Sun 10, 2020 8:53 pm 
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Joined: Mar Fri 27, 2020 2:20 pm
Posts: 45
Thanks Mark.

Guess there are no P103s to be had.

I could use push-ons or just solder to the lugs but I am thinking that I might change the male unit on the chassis to a male 8pos Jones plug that is currently available or maybe a 8pos Molex. While push-ons would work they aren't great for an external connection for the 120v and the relay voltage.
That way all functions would remain and it might be a bit safer it my grandson gets it, etc. That way it would still be usable with a transmitter and an external rely as well. Matching connectors would be available also.

Also considered using an IEC male for the AC and 2 other connectors for the audio and relay. Would be nicely done, no boogering it up.

HV2010


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 Post subject: Re: BC-348(*) PL-P103
PostPosted: May Sun 10, 2020 9:19 pm 
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Joined: Aug Mon 09, 2010 2:57 am
Posts: 781
Location: York PA.
They are to be had; keep your eyes on eBay. They do surface from time to time.

I have 2 BC-348s, one with a dynamotor and one without. Both get power from the back connector. You can do it safely, as well as bring out the relay lines. The wire size is not going to be a problem.

Grandson proofing it is another story I suppose.

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 Post subject: Re: BC-348(*) PL-P103
PostPosted: May Sun 10, 2020 9:50 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 287
Location: New Hampshire, USA
You didn’t indicate how you are planning to power it. If you are going to build a 120v supply inside, as I did, you can disassemble the block and spacers and retrofit a receptacle like the one in the picture below. It will fit snugly into the upper and lower blocks. Ts been a couple of years since I did it so I can’t recall if I removed the ears or not. I think I did so it would fit flush with the clamp and allow the cabinet to slide all the way back with no cutting or trimming.

Two other suggestions:
someone previously asked if you were going to install a receiver mute connection. If you’re going to pair it with a transmitter, it’s a very good idea. I used one of the 1/4” jacks located on the front for this. I used the other one for the speaker connection.

to match the audio output to 8 ohms, there’s no need to replace the existing output transformer. Use an inexpensive 70v to 8 ohm line matching audio transformer. The input impedance will match one of the output impedance taps on the existing transformer and you won’t have to retire everything. The easiest way is to mount the line matching audio transformer in the cabinet of your speaker but I was able to mount mine inside the radio.

I replaced the spring loaded antenna post on mine with a BNC jack.


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 Post subject: Re: BC-348(*) PL-P103
PostPosted: May Sun 10, 2020 10:17 pm 
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Joined: Jan Tue 07, 2020 1:41 am
Posts: 4362
Location: Belleview, FL 34420
I have not seen one for sale for years, not even on ebay. You will have to change it out with perhaps a Cinch-Jones and a home made mechanical mounting bracket.

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 Post subject: Re: BC-348(*) PL-P103
PostPosted: May Sun 10, 2020 11:07 pm 
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Joined: Mar Fri 27, 2020 2:20 pm
Posts: 45
Thanks for all the replies.
I just put an IEC AC input connector on a tube tester I bought. Works great and you will always have a line cord around.

I was thinking of using the IEC for AC and a molex two pole chassis mtg for the relay and either a 1/4" phone jack for the audio out or a phono jack.

i'll have to look at how much room there is. I've got 3 projects going on at one time. Not good.

Attached is a little spread sheet I did some time ago on line matching transforrmers vs impedance. I converted it to pdf so I could post it.

Or maybe a P103 will turn up but I would need 2!!!

Regards,

HV2010


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KR4HV-Public Address linetransformersfor speakers Rev 3.0.pdf [199.01 KiB]
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 Post subject: Re: BC-348(*) PL-P103
PostPosted: May Mon 11, 2020 1:17 pm 
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Joined: Aug Mon 09, 2010 2:57 am
Posts: 781
Location: York PA.
Depending upon how nice your radio is, please don't make non-reversable mods to the front panel etc. That being said, it's your radio and you can and do with it what you please. Radios with original unmolested front panels are getting difficult to find. You will also reduce the resell value of your radio if not original.

Here's the worksheet I did for the line matching transformer for my BC-348Q:

http://www.k3msb.com/misc/line_matching ... rmers.html

Verify your audio transformer is tapped for Hi-Z or Lo-Z (see the schematics) and proceed accordingly.

As I said, check eBay; they do show up (that's how I obtained mine and it's been in the past few years). Another suggestion is to contact Robert Downs WA5CAB. Finally, put a WTB in the antique radio section of QTH.com (free) or place an ad in Electric Radio magazine. I have another place I use for hard to get connectors but the fellow moved and I have his new contact info somewhere around here.

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 Post subject: Re: BC-348(*) PL-P103
PostPosted: May Mon 11, 2020 4:02 pm 
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Joined: Mar Fri 27, 2020 2:20 pm
Posts: 45
Hi Mark.
I agree and I don't intend to make any changes to the front panels. They are very good.

My posted chart for impedance matching transformers agrees with your chart. However, if one is going to use the 300Ω audio output a 25w line to voice coil would probably be more suitable for matching a speaker as they have a 2w tap that is ~300Ω. So I would use the 70v-1w tap one for the 4KΩ out and the 25v-2w tap for the 300Ω output. The PA guys have some that have both the 25v and the 70v primaries on the same transformer. Prices vary by output watt rating and frequency response. I found in research that they even have 100w taps on some but they are very pricey!

The only changes for my "O" and "Q" I have considered (but not done yet) are for the inputs/outputs on the rear. I would want to keep all the inputs/outputs functional that are there now. I think that there will be even less and less availability for the P103 (or variant Q103) in the future. By using a common IEC AC input connector and other common connectors for the relay and rear audio would make the BC-348s more likely to be actually used after I am gone, especially if the P103 (if I can find one or two) plug cable was lost. Just be sure not to use a common audio connector for the relay outputs, one that could be easily mistaken for audio.

That said, I believe that keeping antique radios (and other things) as close to original as possible is important. But IMO making them functional and easily usable is too. There are plenty of shelf queens around already. I want to be able to listen to mine and for my heirs to do so as well if they choose. They are good radios with good specs for general shortwave listening.

I am sure i will have more questions as the electrical work proceeds.

Thanks for the info and the help.

Regards,

HV2010


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 Post subject: Re: BC-348(*) PL-P103
PostPosted: May Sat 22, 2021 11:46 pm 
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Joined: Mar Fri 27, 2020 2:20 pm
Posts: 45
Go to BC-348-) topic


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 Post subject: Re: BC-348(*) PL-P103
PostPosted: May Tue 25, 2021 7:56 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 3711
Location: Monterey California USA
jimbenedict wrote:
I have not seen one for sale for years, not even on ebay. You will have to change it out with perhaps a Cinch-Jones and a home made mechanical mounting bracket.


Nor have I seen one, and if you do, it is going to cost about a much as the whole receiver. They are usually still attached to the shock mount tray. The shock mounts, connectors and dynamotors, once ignored, are now sought after, more than the receiver itself.

I have used a Cinch Jones chassis male on my own bracket where the whole original thing was missing. Where the original was in place, I used appliance style push-on connectors with heat shrink over them.

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 Post subject: Re: BC-348(*) PL-P103
PostPosted: Sep Thu 16, 2021 6:54 pm 
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Joined: Sep Thu 16, 2021 3:21 pm
Posts: 1
Thanks to all for the ideas. I'm also not wanting to modify the receivers of which I have 4. So here's my plan.

As suggested I'll use 8 female spade sockets to mate with the P103. They'll be wired with very short wires to an 8 position Jones socket mounted in a shell that will also accommodate the spade sockets. Then plug the sockets to the BC348 to establish their proper positions and fill the shell with epoxy. This will simply be an adapter from the P103 to a Jones.


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