BC-611/SCR-536 - another hack with an MP3 player for reenactors

Radio Telephone and Telegraph Transmitting and Receiving Equipment
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YLG80
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BC-611/SCR-536 - another hack with an MP3 player for reenactors

Post by YLG80 » Mon Jan 07, 2019 8:05 am

I've recently sold my modified BC-1000 ( viewtopic.php?f=36&t=290272&hilit=bc+1000+fun+hack) and the buyer asked me to also modify his BC-611.
So here is an easy and very cheap tip to revive that legend without having to fully refurbish and restore the equipment or its power supply.
That tip has already been described in an earlier post related to the famous BC-1000/SCR-300.
Thanks to that mod you will revive your old radio set, even not working, with a dirt cheap MP3 Player (3.50€/unit), an SD card and a little battery.
That BC-611 model D has a lot of missing parts, so it's a very good candidate for that mod.
Cheap and easy to do!

You can already see that 1943 BC-611-D modified and playing the radio on youtube. It uses only 3 AAA 1.5V batteries!
https://youtu.be/RtAeDIYBbj0

Note: that video shows a BC-611 modified with a modern 8 ohm speaker replacing the death PHONE cell.
It produces a high audio output. That's good to communicate with the artillery :lol: !

By pulling the antenna, as with the original device, you can listen to the radio chatters played by the mini MP3 player.

For WWII Historical Reenactment, the idea for the radio is to be able to output the recorded chatters via the handset or loudspeaker.
A few WWII battle chatters have been recorded during WWII and are available on the Net. (also on G503 and Youtube). Other, more recent, are also available: Vietnam, AWACS conversations, etc …

The problem with the WWII military radio's is that, even if they are fully working, most of the time they cannot be used by unlicensed people.
Moreover, even if, like me, you are a licensed radio amateur, the BC-611 cannot be used because you have the quartz for only a frequency outside of the HAM bands..

So why not use that equipment only to listen to radio chatters recorded in a very cheap MP3 player that can be hidden into the radio?
This will be exciting for people visiting your shows.
You can switch the radio ON like usual an a few seconds after as if the filaments were heating up, you will hear the radio chats in your headphone.

My quick and dirty project was to put a very little MP3 PLAYER BOARD in that famous Handie-Talkie BC-611/SCR-536, the first portable ever made by Galvin/Motorola.

[ THIS COMPLETE HOWTO IN PDF CAN BE DOWNLOADED FROM : http://www.avi-plus.com/download/HOW-TO ... CR-536.pdf ]


You have two options with the PHONE/SPEAKER :
The MP3 player audio output will be connected to a 8 ohms loudspeaker that will replace the original cell.
The volume will be very loud. You will have to lower it by changing a resistor (R9) on the MP3 module.
Or you keep the original PHONE cell and the audio volume will be lower due to impedance mismatch.

The MP3 board will be switched ON using the original switch, i.e the switch activated by pulling the BC-611 antenna out.
Last edited by YLG80 on Tue Jan 08, 2019 10:48 am, edited 7 times in total.
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Re: BC-611/SCR-536 - another hack for reenactors with an MP3 player.

Post by YLG80 » Mon Jan 07, 2019 8:09 am

For the MP3 player module see fig D.
Image2.jpg
Image2.jpg (121.78 KiB) Viewed 229 times
It can be bought on eBay : https://www.ebay.com/itm/TF-card-U-disk ... rk:17:pf:0


Note : ALL MODS WILL BE REVERSIBLE SO THAT THE BC-611 COULD BE RETURNED TO ITS ORIGINAL STATE.
REMOVED PARTS, I.E A TUBE 3S4 AND THE ANTENNA COIL ARE KEPT SAFE IN THE BATTERY COMPARTMENT.

1- Remove the top cover (on screw) and unscrew the canvas strap.
2- Open the bottom cover (battery side)
3- Remove any battery if present or cardboard battery separator
4- Disconnect the plugs for the PHONE and MIKE.(red and green dot)
5- From the antenna side push firmly on the metal part to extract the chassis from the casing.
......The chassis will be extracted from the other side.
6- Remove the 3S4 tube and the antenna coil to make room for the MP3 player module.(see photo 7)
......The tube and the coil will be kept in the battery compartment.(packed in foam)
7-IMG_7864.JPG
7-IMG_7864.JPG (170.87 KiB) Viewed 229 times
./..
Last edited by YLG80 on Mon Jan 07, 2019 10:36 am, edited 1 time in total.
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Re: BC-611/SCR-536 - another hack for reenactors with an MP3 player.

Post by YLG80 » Mon Jan 07, 2019 8:12 am

The antenna coil and the tube 3S4 have been removed and replaced by the MP3 mini module.

The chassis is now ready to accept the module.
You will have to disconnect 4 wires and solder new wires for the MP3 module.
SCR536 - BC611 Schematic Diagram-MOD.jpg
SCR536 - BC611 Schematic Diagram-MOD.jpg (231.42 KiB) Viewed 192 times
At the bottom side of the radio, the connecting posts will be used as follows (in red):
fig-a_battery-and-speaker-contacts.jpg
fig-a_battery-and-speaker-contacts.jpg (65.68 KiB) Viewed 228 times
7- Disconnect and insulate the brown wire from the A+ battery post. (see fig B and photo 3)
fig-B_battery-connection.jpg
fig-B_battery-connection.jpg (111.74 KiB) Viewed 228 times
3-IMG_7856.JPG
3-IMG_7856.JPG (172.39 KiB) Viewed 228 times
8- Solder a red wire to the connecting post shown on fig. B. That white wire has to be long enough to reach the MP3 player location in the chassis.
......(see photo 6 for the MP3 module position in the BC-611 chassis) .
6-IMG_7861.JPG
6-IMG_7861.JPG (191.13 KiB) Viewed 228 times
That wire has to be soldered to the BAT (-) connection to the MP3 module.(near the mini usb connector)

./..
Last edited by YLG80 on Mon Jan 07, 2019 2:52 pm, edited 1 time in total.
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Re: BC-611/SCR-536 - another hack for reenactors with an MP3 player.

Post by YLG80 » Mon Jan 07, 2019 8:48 am

9- Disconnect the Orange and White wires from the Mike and Phone post on the bottom side of the chassis and insulate them.(fig C and Photo 1)
fig-C_loudspeakers.jpg
fig-C_loudspeakers.jpg (83.52 KiB) Viewed 226 times
1-IMG_7857.JPG
1-IMG_7857.JPG (198.44 KiB) Viewed 226 times
10- Solder 2 wires, the first to the MIKE and the second to the PHONE post.
......As it will be used for the MP3 module player SPEAKER, don’t care of the polarity.
......Both wires may be of the same color. (see photo 2, white wires)
......These white wires have to be long enough to reach the MP3 player location in the chassis.
......They will be connected to the MP3 player via the blue connector SP.
2-IMG_7860.JPG
2-IMG_7860.JPG (198.94 KiB) Viewed 226 times
./..
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Re: BC-611/SCR-536 - another hack for reenactors with an MP3 player.

Post by YLG80 » Mon Jan 07, 2019 8:52 am

11- As shown on photo 4, disconnect the red wire.
4-IMG_7858.JPG
4-IMG_7858.JPG (226.03 KiB) Viewed 226 times
12- As shown on photo 5, insert an insulator and solder the disconnected red wire to a white wire.
5-IMG_7859.JPG
5-IMG_7859.JPG (234.55 KiB) Viewed 226 times
That white wire has to be long enough to reach the MP3 player location in the chassis.
(again, see photo 6 above) .
That wire has to be soldered to the BAT (+) connection to the MP3 module.(near the mini usb connector) (see MP3 player board layout on fig D above)

13- Photo 6 shows the connected MP3 player module near its location in the chassis.
6-IMG_7861.JPG
6-IMG_7861.JPG (191.13 KiB) Viewed 226 times
14- Photo 7 shows the MP3 player module in its location in the chassis and protected with insulating foam.
7-IMG_7864.JPG
7-IMG_7864.JPG (170.87 KiB) Viewed 226 times
15- Photo 8 shows the battery pack inserted in the original battery compartment and maintained in place with foam. The removed tube and coil are stored behind the battery pack.
8-IMG_7853.JPG
8-IMG_7853.JPG (169.95 KiB) Viewed 226 times
./..
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Re: BC-611/SCR-536 - another hack for reenactors with an MP3 player.

Post by YLG80 » Mon Jan 07, 2019 8:56 am

16- Photo 9 shows the finished assembly.
The SPEAKER is connected via the two posts with RED and GREEN dots, and the battery pack (+=red) and (-=black) is connected to the original battery connecting springs.
9-IMG_7855.JPG
9-IMG_7855.JPG (164.74 KiB) Viewed 226 times
So you can still disassemble the radio as before.
That photo shows a connection to a new 8 ohm SPEAKER with the two wires.

If you decide to keep the original PHONE cell, you will connect the original wire with the little plug to the PHONE post.
You will then open the PHONE cell cover and disconnect the little wire that is connected to the case below the cell.

You will then connect the second wire coming from the green dot MIKE post to that wire by means of an eyelet and a screw+nut (see photo 11)and insulate the assembly with tape.

On Photo 10, the battery pack is inserted in the battery compartment and maintained with foam, and the cover can be closed.
10-IMG_7854.JPG
10-IMG_7854.JPG (152.91 KiB) Viewed 226 times
That’s all about it.

You have only 6 wires to add: 4 inside (2 for the Power Supply and 2 for the SPEAKER) 2 outside between the bottom connecting post and the SPEAKER/PHONE cell.
You add also a battery pack for 3 AAA cells. (Photo 11)
IMG_7871.JPG
IMG_7871.JPG (223.65 KiB) Viewed 226 times
The photo shows two different models.

The BC-611 radio is switched ON by pulling the antenna out as usual.
./..
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Re: BC-611/SCR-536 - another hack for reenactors with an MP3 player.

Post by YLG80 » Mon Jan 07, 2019 8:59 am

Remarks :

SPEAKER
The original BC-611 speaker has a high impedance that does not match with the low impedance of the MP3 player SP output.
This gives a reasonable audio volume which is ok for me.
However if your speaker is damaged, as in many WWII radios, you will change the speaker and install a mini 8 ohms, 2W or 3W speaker.
(similar to the ones in the old PC towers.)

The audio volume will be way too high!
You will have to change the MP3 player circuit like this.
Remove R9 and replace it with a 200Kohms or more to reduce the audio output.
You can also replace that resistor by a mini potentiometer of about 470~500 K ohms. (see fig. D)
MP3_Player_R9_audio_output.jpg
MP3_Player_R9_audio_output.jpg (129.89 KiB) Viewed 226 times

SPEAKER PLUGS
The little plugs to connect the speaker wires to the chassis are Molex crimp connectors found in a junk box.
I believe that plugs used in old PC's to connect the power supply to disk drives and hard disks should be also OK.
Usually these are Molex connectors.
IMG_7865-2.JPG
IMG_7865-2.JPG (83.16 KiB) Viewed 224 times

PARTS REMOVED
In order to make that mod reversible, keep the parts removed in the battery compartment.

End of Mod Description.
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Re: BC-611/SCR-536 - another hack with an MP3 player for reenactors

Post by creinemann » Sat Jan 12, 2019 1:33 pm

Would you be interested in writing this up as an article (PDF) that could be shared, with all credit to you? I get a lot of requests for tricks like this from my site at http://dodgem37.com/wwii-radio-restoration/. Contact me via PM if you're interested.

Thanks
Carl Reinemann
Wisconsin
1953 Dodge M37 & M101 and Military Radio Pages at

http://dodgem37.com

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Re: BC-611/SCR-536 - another hack with an MP3 player for reenactors

Post by YLG80 » Wed Jan 16, 2019 7:43 am

PM sent with the 2 links for the "Howto" pdf files (BC-611 and BC-1000)
Yves
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Re: BC-611/SCR-536 - another hack with an MP3 player for reenactors

Post by creinemann » Wed Jan 16, 2019 10:38 am

Yves,
Thanks for sharing the PDF's, I have them on the site at http://dodgem37.com/wwii-radio-restoration/ I think I make a special "hacks" section when I get some free time.

Carl
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1953 Dodge M37 & M101 and Military Radio Pages at

http://dodgem37.com

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Re: BC-611/SCR-536 - another hack with an MP3 player for reenactors

Post by YLG80 » Thu Jan 17, 2019 12:50 am

Cool, I will give you other hack descriptions soon.
Yves
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