J. Hill wrote:
I purchased a Collins 51S1-A, the 28 volt DC, receiver that had been converted to 120 volts AC. It looks all Collins on the inside, so I am curious if there was a kit to do this or if the person doing it bought the Collins parts to do so. The wiring looks very professional, almost too good to be done in someone’s garage. However, it is wired only for 120 volts, it has the correct dual primary transformer but the wiring is not such that it can be operated on 240 volts with a power cord having the proper jumpers in the connector. Does anyone have any thoughts or information on such conversions?
Howdy,
You can get a little insight on how this "conversion" was accomplished by looking at the 51S-1 manual.
The CCA has a copy of the manual that is in the public domain that shows how Collins did the 28V DC power supply that is essentially the same as other amateur radio manufacturers did it (I.E. Drake, Hallicrafters, Heathkit, etc) except they did it using an external power supply that not only operated on 12V DC but also supplied voltages for the transmitter sections of a transceiver ....and in the case of the Drake DC-4, it could even power a complete Drake C-Line (transmitter and receiver)
You can have a look at the manual here:
http://collinsradio.org/archives/manual ... ceiver.pdfIt's pretty clear that they placed a simple solid state switching type DC power supply in a "box" that provides the correct DC voltages and mounted it on the chassis where the 60Hz transformer/rectifiers and capacitors would be placed, possibly using the same mounting holes to facilitate the manufacturing process so any 51S-1 could be retrofitted with the 28V DC power supply chassis in the field with maybe a few other wiring changes to accommodate the different filament wiring.
Anyone could also convert back if they desired once the correct transformers and other components were obtained (and even do it their "garage"!!) since they would be mounting the transformer/caps etc in already present mounting holes etc.
The only "Collins part" required would likely be actual power transformer for probably any 75S- receiver. I think those are in abundant supply new (old stock) and used. The rest of the parts would be pretty generic.
Cheers,
Rick