This is the front panel. Note that LSB and USB have separate outputs, separate gains, separate meters, and separate headphone output jacks. "Stand-By" on the selector switch keeps the heaters of the two RF amplifier tubes warm. The five frequency control knobs have the most annoying feature that they have stops that prevent them from switching directly from '9' to '0'. One of the first things most R-1051 owners do is take the knobs off and remove the little piece that enforces these stops. It is much easier if you can just crank it in any direction to the number you want.

This picture shows how deep the unit is. Despite the fact that this is a "modern" transistorized unit, it is still a boatanchor. It weighs about 70 pounds, which is almost exactly what the SP-600 weighs. The electronics are on slides in the case, so you just loosen the 6 captive screws on the front panel and all the guts slide out. There is an umbilical cable that connects to the case. This is a bit deceptive - all the weight is in the electronics rather than the case, so if you have this sitting on your bench and slide it out of the case, it will probably end up in your lap. You are better off to extract it on the floor and take it off the slides, then put the whole mess back up on the bench.

When you slide the electronics out, you get immediate access to a number of test points and adjustments. All the modules just plug in and are easily removed. Each one has a few captive screws, then just pops out. Mind you, this means that it is relatively difficult to debug these things, since you can only get at the signals that are on the test points. No, you can't just turn it over and get at the pins on the connectors - that is where the Rube Goldberg mechanical tuning contraption are located. The bottoms of the module connectors are not readily visible. The people that spend a lot of time working on these things have butchered a junker and made up a bunch of extender cables so that each module (except maybe the RF module) can be taken out and probed on the bench. You can take the covers off the modules, so it is not hard to tack a few wires onto key places. This works in most places, but there are a few places where you really shouldn't do that.

This is a good view of the modules. The large unit in the lower left is the RF deck. There is a turret inside that has 28 positions - one for each megahertz of the tuning range. Each position selects a different set of coils for the RF amplifiers. Top middle are the two (identical) IF amplifiers. There is a separate IF amplifiers of USB and LSB, since they are received simultaneously. The bottom right is the "six-pack", which is the frequency synthesizer and mixer. The actual mixing happens on the skinny unit on the left, called the "translator." Note that here is probably the easiest way to distinguish a R-1051 from a R-1051B. In the 'B' (and higher) revisions, there is a "100 CPS SYNTHESIZER" in place of the "500 CPS SYNTHESIZER." Other than that, the differences are pretty subtle, and the performance is largely indistinguishable. The pretty yellow labels on the frequency standard and the 100 KC synthesizer inform us that we shouldn't be trying to repair those on the ship. As with stickers that say things like "breaking this seal will void the warrenty", we can admire their quaintness, then ignore them.

This is the underside of the unit. Note that the connectors the modules are seated in are nowhere to be seen. The first three knobs (10 MHz, 1 MHz, 100 kHz controls) take a right turn then connect to bicycle chains that go to the three-headed selector. Each control goes to a wafer switch. The 10 and 1 MHz wafer switches encode a number. A motor drives the RF turret around until its selector switches produce a matching number. So every time you change the MHz knobs, it goes "whir-whir-whir-klunk!" as it rotates the RF turret to the appropriate band. Note also that this means if the contacts on the wafer switches on the turret are dirty, it might not ever find the number and will sit there and go 'round and 'round forever! The first time this happens to you, you immediately jump for the power. Since the motor that drives the turret has a limited service lifetime and there are probably no modern replacements, you don't want to let it run on for too long.

I was trying to show here how the 10 MHz change knob is connected directly to that sprocket that drives the chain. On the extreme right is the blue, plastic cable cover. Maybe it shows better in the previous picture. These are almost always broken right in the middle. The reason? The bolt hole for the bottom middle front-panel bolt catches it as you slide the radio back into the case. It only takes a couple of cycles of taking the electronics out and putting them back in before the cable cover catches on the raised part of the inside of the case and it is broken in the middle. You want to put something on the cable cover when you slide the electronics back in to make sure it doesn't snag on the case. Just a shim is all it takes so it will slide in easily. Be sure not to leave the shim in with the electronics - all you need is to get something caught in those chains.

This shows the 4-layer wafer switches on the 10 kHz and 1 kHz selector switches. I have a hard time imagining why they didn't do that on the other three knobs as well. Granted, you have to run a mess of wires from these wafers back to the RF turret, but it would eliminate the chains and sprockets and all that stuff. This was all before the day of flex-cable.

Navships 0967-034-2000 "Repair of AN/WRC-1 and R-1051/URR 2N Modules"  This is a 44-page manual on the repair of some of the modules in the R-1051. These are the RF amplifier, the frequency standard, and the translator/synthesizer. Hmm. There is not much left after these - the IF cans, I guess. It is 44 pages. It is not my scan, but I did go through and de-screen the halftone images. Thanks to Norman Dulebohn of Wapakoneta, Ohio for this manual. Thanks, Norm!

NAVELEX 0967-LP-970-9010 "Technical Manual: Maintenance Instructions, Radio Receiver R-1051/URR"   This is the whole manual, with all the wide pages in the PDF right where they are in the physical manual.

NAVSHIPS 0967-970-9010 (Formerly NAVSHIPS 94841(A)) "Volume I: Technical Manual for Radio Receiver R-1051/URR and R-1051B/URR" dated 1969   This covers the R-1051 and R-1051B. The only difference, really, is that the "B"-model has a 100 Hz minimum frequency step whereas the original has a 500 Hz step. The 100 Hz step is REALLY, REALLY handy for SSB.

NAVSHIPS 0967-878-3010 "Volume I: Technical Manual for Radio Receiver R-1051D/URR" dated 1970   This covers the R-1051D. This one has crystal IF filters! Whew! The selectivity of the previous receivers was just awful. You can see the beginnings of the use of LSI here and there, but the frequency synthesizer is still all discrete-transistor flip-flops!.

EE125-AF-0MI-010/E110-R1051H "Technical Manual, Operation and Maintenance Instructions With Parts List, Organizational And Depot, Radio Receiver R-1051H/URR"   Watch out! This one is huge. It is 660 pages with lots of them really, really big. This manual is specifically for the "H" model and may or may not have anything to do with the other models. That having been said, many parts are applicable to other models. For instance, this manual has many more drawings of the mechanical linkage among the turrets and motors, and that feature seems to be pretty consistent across the models. The "H" model is interesting in that it uses SSI and MSI logic. It is not exclusively discrete transistors. That notwithstanding, it still has the most baroque frequency selection scheme I've ever seen. Most of the circuitry is dedicated to frequency synthesis. This radio has four (count them - four!) consecutive mixers to get the input signal to the IF band. There can't have been many of these receivers built. Thanks to Cecil Acuff for the loan of his manual (for several months!) for me to scan.