these days it is next to impossible to find RC-550 for under $500. I got mine off eBay, it was in such poor condition that no self-respecting collector wanted to bid against me. Here is the happy ending for El Diablo: Good efforts prevailed over Evil elements of Time and Indifference

poor Devil was in pretty miserable condition, broken antenna and paint from some construction site, bad motor plus the usual of melted belts and rust. 

Cassette mechanism, as received

I tried everything I had at my disposal as plastic jets modeller: Windex, alcohol, acetone, lacquer thinners, Naphta, Goof-Off, turpentine, but the only thing which saved me from scraping this licorice goo was lowly generic Paint Thinner. Paint Thinner removed this licorice without any pre-soaking or scrubbing: pure Magic!

Cassette mechanism fully disassembled, metal parts cleaned and oiled, rubber tyres rejuvenated with Naphta

Sintered brass cleaned with acetone, then impregnated with oil. Oily cotton stick was left in place for a few days

Pinchroller was in good shape, treatment with Naphta seems to have restored its original state. Center pin is flattened from both ends, I am not too crazy about getting a new pinchroller.

Motor grommets got Naphta treatment as well

Original belts, stretched and hardened. New belts from Turntable Needles are SBR7.2 and FBS10.5

Motor had a dead spot, plus neither motor nor control board give any provision for adjusting play speed. New motor from Pacific Stereo was bought, with CW rotation and 2.5mm shaft mod. Motor is advertised at tapeheads.net: Universal, extremely high-quality replacement cassette capstan motor available NOW!plastic shim was used to reset the pulley at the same height

Getting new JVC antenna was pure luck: one eBay seller responded to my request by selling me like-new RC-550 antenna!

The second part of restoration was more fun because everything already worked.

To keep my “idle hands” busy I opted for a full recap of the main board:ongoing…and done!

Paper cone speakers were in decent shape, once spray-painted with Red Ink the end result looks more “diabolical”

Prior to airbrushing ink was diluted 30-50% with pure Ethanol

Thorough cleaning and warm bath was the next step:

Red cones are not quite in your face, but the color of blood is there!

Final speed check before closing the case:

With new Pacific Stereo motor and Turntable Needles belts W&F is lower than factory specs of 0.17

Broken screw post got fixed with polystyrene glue, dried for 48 hrs and then reinforced with 2-ton epoxy:

Cassette mechanism buttons are color-coded: Rec as Red (as it should be) and Stop/Eject as Light Blue (strange choice for a Stop button!). When fixing the screw post, I colorized some of the epoxy and now all the buttons are happily coloured:

The end result looks nice: I recorded cassette copy of “Stereophile Test CD” and confirmed that RC-550 does play both L and R channels of stereo cassettes, but in Mono.

Yet another Mod: when looking at RC-550 Service Manual I noticed that mid-range (SPKR 2) is wired out of phase with woofer and tweeter:

I listened to restored El Diablo “as-is”, the sound was dark and bottom-heavy with some sizzle on top, the way my younger self loved it! Then I disconnected the mid-speaker (working against the huge woofer for mid-range) and El Diablo became a seriously loud boomer! Then I reconnected mid driver in the “standard” configuration. Mid-range came forward, now I can actually hear the lyrics, and tone controls started to control something, not just booming and hiss… In short, when SPKR2 wired “correctly” it is a bbox for the middle-aged guys like me, in its factory configuration it is for the younger folks. To flip two wires, this is the easiest “mod” ever!

 

Fixing the motor. Original motor had dead spot, but instead of throwing it into the spares bin I took it apart first:

after cleaning and DeoxIT-ing, leaking 10uF cap exchanged. Looks like the rotor has two weights which disconnect power to the motor when pushed away by centrifugal force. Is this some kind of speed regulator?

 

RC-550 undergoing tests in “field conditions”: