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 Post subject: BC-348, what model or version do I have?
PostPosted: Sep Wed 13, 2017 2:12 pm 
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Joined: Sep Wed 13, 2017 10:09 am
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Gentlemen, last week I picked up a nice unmodified BC-348. My problem is that the front panel ID-plate is missing. The paper label inside the cabinet is also gone. I have spent many hours trying to find traces that can tell me which version it is. Tubes are 6F7, 6B8, 6K6, 6C5, 6J7 and 3x6K7. From the tubes installed I have found that it should be any of R, H, K, or L.

Most of the caps are black Micamold a few caps are red Aerovox.
The dynamotor is a DY-2A/ARR-2 from GE. Probably replaced, there is a tag saying “date 1-56”.
"Dynamotor not electrically connected". Not intended for this unit.

The Osc tube socket is ceramic (BC-348-R only?)
Detector is stamped Jan 15.

The missing name or I.D.-tag has probably been fitted with four screws (not rivets that I have seen on other pictures). The two lower screws have washers and nuts to cover the empty holes. Upper screws are machine screws probably due to difficulties to reach from inside the chassis. The only ID or mark found is the “W” on the front.

On the backside of the cabinet there is a hole which is covered by a plate. I have not seen this hole on other pictures I have found.

In the 348-H manual and other pics I studied on internet I found that the six metal can caps are wired in parallel, mine has a somewhat different wiring. Perhaps the wiring of these 0.5uF caps can tell something.

My radio must have a “name”. Without the ID-plate, no “soul”. So I have to make my own plate with a correct number on it and with a blank serial number. I intend to keep it “as is” for 28VDC and only update caps and resistors.
Is it possible to identify the maker and model with the help from the following pictures?

Any help will be much appreciated.

Goran, SM7DLK


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front-1.jpg
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back side.jpg
back side.jpg [ 90.44 KiB | Viewed 459 times ]
Cap wirings.jpg
Cap wirings.jpg [ 101.62 KiB | Viewed 459 times ]
W mark front.jpg
W mark front.jpg [ 125.89 KiB | Viewed 459 times ]
Hole backside 1.jpg
Hole backside 1.jpg [ 63.32 KiB | Viewed 459 times ]
Top view.JPG
Top view.JPG [ 107.32 KiB | Viewed 459 times ]
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 Post subject: Re: BC-348, what model or version do I have?
PostPosted: Sep Wed 13, 2017 10:02 pm 
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It's an early unit because of the double ended tubes, that is tubes with grid caps, of which there were several suffix letters, and I'd add E, M, P versions to your list as well. Later versions incorporated several cost reduction changes.

The Dynamotor mounting doesn't appear to be "stock" because I it was mounted with shock mounts not unlike the ARC-5 units.

The original nomenclature plates were riveted on, no screws.

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 Post subject: Re: BC-348, what model or version do I have?
PostPosted: Sep Wed 13, 2017 10:58 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 30765
Location: Maryland 20709, USA
Hi Goran,

This is not an E, M, or P, based on the seventh bypass cap sitting by itself in the lower-left corner.
That was not present in the E, M, or P variants.

It's not a J, N, or Q, since those used single-ended tubes (no top caps).
And they had a rotary CW Oscillator control at upper-left of the front panel.

My guess would be an H, K, L, or R.

There are other versions for which I have inadequate information.

And there was a BC-224, almost identical.

- Leigh

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Last edited by Leigh on Sep Thu 14, 2017 12:46 am, edited 1 time in total.

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 Post subject: Re: BC-348, what model or version do I have?
PostPosted: Sep Thu 14, 2017 12:26 am 
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Joined: May Sun 28, 2017 9:08 pm
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Location: Whiteville, TN
Really nice find! Even the paint looks good! Good pictures! I am always amazed at the fount of details these guys can produce. Alas, I am not one of them! Keep on, it will all come together.

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 Post subject: Re: BC-348, what model or version do I have?
PostPosted: Sep Thu 14, 2017 1:18 am 
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Location: Milwaukee,WI
It looks like a BC-224 to me. If it has no 200-500khz band then its the D model. See the radio in the middle at the top of this linked page.
http://www.bwgsurplus.com/web/air_recv/air_recv.htm


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 Post subject: Re: BC-348, what model or version do I have?
PostPosted: Sep Thu 14, 2017 4:09 am 
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Location: Portland, TN, USA
I'm no expert on these by any means, but I have two, a -J and an -H.

My H matches this one perfectly except it has what looks to be a factory AC supply instead of the Dynamotor.

I can post or email pictures if it would help, but I've done a pretty thorough stare and compare between my pictures and yours before posting.

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 Post subject: Re: BC-348, what model or version do I have?
PostPosted: Sep Thu 14, 2017 5:40 am 
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Joined: Aug Sat 13, 2016 6:03 am
Posts: 67
My P model uses the same tubes and has the ID plate secured with rivets. I would have to guess your ID plate was misplaced at the time the front panel was painted. I can tell by the masked area around the lettering. They did a very nice job. You've got a beautiful receiver, what ever it is.


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 Post subject: Re: BC-348, what model or version do I have?
PostPosted: Sep Fri 15, 2017 5:34 am 
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Location: Monterey California USA
Hold on, the BC-348P uses a type 41 in the audio output and as it was by Stromberg Carlson, the chassis looks somewhat different. And as Leigh says above, the P has a different arrangement of bypass caps.

This one has been repainted, you can see the areas where the person masked the lettering off. The dynamotor is from an ARC-5 and has been mounted to an aluminum sheet. I am not sure the ARC-5 dynamotor can hack the increased current from a 348. The plugged hole in the rear is not stock. A pox on people who remove nameplates... :(

I think this is either an H, K or R, or maybe a BC-224 (compare wiring to manuals.) It matches the way the Belmont sets look. My guess is an R, because those seemed the most common back in the day when these were surplus.

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 Post subject: Re: BC-348, what model or version do I have?
PostPosted: Sep Sat 16, 2017 5:53 am 
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Thanks Geoff for pointing out even more differences with my P model


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 Post subject: Re: BC-348, what model or version do I have?
PostPosted: Sep Mon 18, 2017 10:36 pm 
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Location: Beaver Falls, PA. USA
It looks like some of the dreaded Micamold capacitors have already been replaced. They all have to go, if you want to operate the set; they're not mica, but molded paper.

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 Post subject: Re: BC-348, what model or version do I have?
PostPosted: Sep Wed 20, 2017 9:12 am 
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Joined: Sep Wed 13, 2017 10:09 am
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Thanks for all feedback and thanks for informative info on https://www.nonstopsystems.com/radio/pd ... kf6nur.pdf

I have now summed all info and my radio must be a BC-348-R. It’s a CCC tube version + ceramic HFO socket. Two ** also tell that a plastic label was fitted. There are threads for four screws in the front panel, so no rivets. So I guess screws was used for plastic labels. I assume the Order then was 11414-43.

The dynamotor is not original. I found out it must belong to an ARC-5 and it was not internal wired, only mechanically fitted. But it can still be used, I separated the HV ground point from the -28V to get a separate feed for HV and thereby correct bias. All Micamould caps was defect and now changed.
At last I can now stick a label on to my "BC-348-R".

Thanks
73 Goran SM7DLK


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 Post subject: Re: BC-348, what model or version do I have?
PostPosted: Sep Wed 20, 2017 12:42 pm 
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It seems most of these types I find are BC-348-R manufactured by Belmont.
I have two of them now. The first one I got while in high school.
I remember powering it up with a power supply I made and one by one, the square Micamold caps shorted and burned up an associated resistor.
After a few incidents of this, I recapped it and it was a fine performer!

It was my first adventure into the world below the AM broadcast bands finding aircraft NDBs and weather stations. :D

So much fun!

-Steve

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