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hey everyone this is wartime workshop and this is a model BC 654 transmitter and receiver the main component of US Army radio set SCR 284 this 45 pound absolute unit of a radio was made by Crosley Corporation during World War two I'm interested in wartime technology so I got this radio planning to clean it up and get it working again I'm gonna document that process in videos on this channel my hope is that someone else finds this interesting entertaining or educational if that sounds like you I hope you'll stick around and consider subscribing this will be the first in a multi-part series on the BC 650 for today I'll be disassembling the radio assessing the construction and design and replacing some missing components the BC 654 was technically considered portable able to be mounted in a vehicle or carried on foot but it was still an old fashioned vacuum tube radio in addition to the 45-pound main unit you needed to carry around another 60 pounds of accessories for it to be of any use the radio itself contains delicate tubes intricate wiring and a surprising number of moving parts multiple sources quote soldiers as saying that these devices were exceedingly cumbersome on the battlefield and I can see why if you needed to transmit and you weren't in a vehicle you often had to power the radio using a hand crank generator that looks a lot like a piece of exercise equipment I would imagine that factor becoming especially significant if you just rocked the equivalent of a mini-fridge on your back for several miles in exchange for all the inconvenience you got a complete portable radio station comprising a high frequency receiver in the top part of the case a transmitter on the same band in the bottom and a built-in antenna tuner the frequency coverage overlaps conveniently with amateur or ham radio bands so I'll be able to legally transmit once my unit is working as per the typical traditions of ham radio I expect about 90% of the conversations I have using this thing to be discussions about the radio I'm using seriously though I think the radios from this period are fastened despite being electronic products at heart they're highly mechanical much of the design is motivated by the need to fit numerous large delicate components into a portable container now that I've said that you'll probably want to see the inside to disassemble the BC 650 for you first remove the lid from the case then you loosen thumb screws around the front panel and the radio can be pulled out the front of its enclosure the enclosure by the way is great it's just a metal box but inside there's a beautiful schematic of the radio there are also military markings including dated order numbers flipping around to the back of the assembly the receiver is dominated by a huge variable capacitor with a geared mechanism driving it in the transmitter section there are several large tubes and capacitors plus all the hardware for the antenna tuner subsystem a fair amount of thought went into making the innards of the radio accessible a really cool example of that is the linkage on the side it's a toggle arm that allows you to pivot the top receiver section forward and access the transmitter section from above so this isn't just a rigid frame but an articulated assembly just to make maintenance easier i know'd it out as soon as I got a look at this thing physically this radio is in great condition only requiring a little bit of cleanup a few mechanical components are missing and I'll need to install a power supply the electronics inside are also likely to require some serious repair it's common for the paper capacitors in these radios to stop working with age requiring replacement now that I'm inside I'm noticing that this radio has a particularly heavy coat of moisture and fungus proofing lacquer or MFP with a labelled coating date of July 1945 it looks like at least some of the tubes have been replaced since the coating potentially by another ham or collector that may bode well for getting it working it's also possible that the coating has protected the notoriously bad paper molded capacitors for moisture but 75 years is a long time and I'm not holding my breath we'll get into the details of the capacitor issue in a future video although there are several missing parts I was able to steel replacements from another radio that's in worse condition the first part that's clearly missing is the receiver tuning knob this piece sits on top of a felt washer and attaches to the receiver tuner shaft with a set screw the tuning gears take a fair amount of torque to rotate so the crank style handle is actually very helpful the other missing component is less obvious until you try to install a power supply there are two options for the internal power supply of the BC 654 one is a battery pack the other is a power converter module called a PE 104 whichever of these is used it needs to be mounted in the top right corner of the radio so it can plug into this wiring harness normally there's a small sheet metal shelf that holds the power supply but that assembly is missing from this unit apparently it's very common for this shelf to be missing so I was lucky to be able to find a replacement the installation of the shelf is pretty easy it's held in place by a few machine screws and the wiring harness wraps around some support pegs on the side I think I spent more time making sure I had all the fasteners in the right place then I actually spent installing the shelf as I mentioned the power supply shelf can host either a battery pack or an electronic power converter these devices both produce all the voltages required by the receiver and several of the voltages for the transmitter I do have a PE 104 converter unit but it makes me a little nervous it uses a really neat but really finicky electromechanical circuit to step up a low voltage source I'm afraid that the output voltages could be unstable if I make any mistakes during my restoration some of these voltages are critical for instance the filament supply nominally 1.5 volts can destroy all the tubes in the radio if it goes too high since I really don't feel like buying a whole new set of tubes I'm gonna set the PE 104 aside for now and attempt to build a working replica ba 43 battery in its place this will give me stable consistent voltages that I can fully control as a bonus the BA 43 battery can be used with any transmitter voltage source the transmitter requires a separate high voltage supply of 500 volts which can come from either a hand-crank generator or a vehicle Dyna motor I have a dynamo tur and I'm working on collecting the parts for the generator so I'd like to try them both the Signal Corps manual advises not to use the power converter with the crank generator except in emergencies so if I use the PE 104 converter I'd have to stick to the Dyna motor the battery leaves me with either option creating the replica battery pack will allow me to test the receiver section so this will probably be my task for part 2 I've got a few ideas for how to do this and I think it will make for an interesting project so stay tuned before I end this video I need to mention one more thing I'm far from the first to work on one of these radios sets like this and other sets from world war ii have been operated by hams for as long as they have been available i really couldn't get anywhere on this project if it weren't for the fantastic resources already available online i've included several links in the description to resources that taught me what I needed to know for this project these sites deserve thanks and patronage from anybody who is interested in this sort of work and this video wouldn't be possible without them with that all have left to say as I hope you'll be back for part two and of course thanks for watching