Nakamichi RX-303

derek92994

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#1
Picked up this one recently for a reasonable price. Of course there was the "All Functions Working" Claim. Once it arrived I set it up on the work bench to do some basic tests. Sure enough all functions were working, idler tire in good shape, pinch rollers needed a clean but not too shabby. When hooking it up to the system, this revealed its flaw, the sound would play for a few seconds then deteriorate in quality before disappearing. It turned out that someone had put a belt kit on this unit, the capstan belt being too tight causing the dual capstan system to 'lift' the tape off the head, as this unit uses a tape pressure pad lifter and relies on good tape tension to work properly.



I got to work on it, installed Marrs Belts, cleaned/re-lubed capstan bearings, mechanism, replaced reel table clutch felts, adjusted speed, azimuth and head height. This solved the tension issue, the unit now plays well. I did notice some very slight frilling of late generation TDK tapes when played in the unit (during testing). All other brands of tape were ok and did not show this symptom. I have ordered new pinch rollers to rectify this problem, none of my precious recordings have suffered from this, so I am glad the problem has been identified early.

I should mention that if you are disassembling this deck to remove the transport, that it is a bitch if you are doing it for the first time, which I found, but learnt from. Having becoming accustomed to the Nak 480 which uses almost the same transport as this RX-303, things were slightly different to pull apart. Mech screws are behind the button panels, which I did not notice at first, requiring a couple of tries. Once out it was just like working on a typical Nak "Classic" mechanism.

Type: auto reverse, 2-head, single compact cassette deck
Track System: 4-track, 2-channel stereo
Tape Speed: 4.8 cm/s
Heads: 1 x record/playback, 1 x erase
Motor: 1 x reel, 1 x capstan, 2 x mechanism
Tape Type: type I, CrO2, Metal
Noise Reduction: B, C
Frequency Response: 20Hz to 20kHz (Metal tape)
Signal to Noise Ratio: 68dB (dolby C)
Wow and Flutter: 0.04%
Total Harmonic Distortion: 1.0%
Input: 50mV (line)
Output: 1V (line)
Dimensions: 450 x 144 x 300mm
Weight: 10kg
Year: 1984

The uni directional Auto Reverse worked perfectly though which is simply the coolest part of the deck. It also has blank skip function, for those lazy days on the couch. MPX and Subsonic Filter were a couple more features I noticed, nice addition. Cosmetics are above average with some marks on the top cover.




















The next plan is to re-cap the Power Supply and Main board, considering the unit's potential age of 34 years, I think this would be a wise move. Even in its current form, I have had much enjoyment listening.
 

nakdoc

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#2
I wish I could take such clear pictures. Before you condemn the pinch rollers, which almost never wear out, disable the supply side roller by removing it's spring. Make an open or mirror cassette and observe what the tape does when you first go into play. If it skews a lot, your back tension may be zero.
 

derek92994

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#3
I wish I could take such clear pictures. Before you condemn the pinch rollers, which almost never wear out, disable the supply side roller by removing it's spring. Make an open or mirror cassette and observe what the tape does when you first go into play. If it skews a lot, your back tension may be zero.
Hey Nakdoc

Thanks for your reply. I need to re-attempt making an 'open' cassette, the last one I attempted shattered during cutting :evil4:

I'm fairly sure the slight frilling of the tape is occurring on the take up pinch roller guide. The pinch rollers don't look too bad, but replacements are on the way in case.

The Back tension is working, I do not have a gauge to test, however upon checking the BX-300 and 480 deck that I have by hand, it appears to have less than those two, so an adjustment may be in order. I assume there is no easy way to adjust without removing the mech again. I may be able to get to it by loosening the two front button panels, or by taking front panel frame off, so I can access the two cassette well plate screws.
 

derek92994

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#4
Update on the RX-303

Purchased new Pinch Rollers and this perfected the transport stability, no more 'slight' tape frilling. Have also replaced all electrolytic and those nasty orange capacitors. It has probably had about 50 hours run time since with no issues, great unit.

Here are some better and updated pics:

























 

derek92994

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#5
Capacitor Replacement Process. Pictures are mixed up but as a guide:

Light Blue Caps are the old ones (Especially in power supply section)
Pink Film Capacitors replaced those evil orange caps. There is 1 set of existing orange caps which were replaced with same type due to lack of film cap stock.

I used quality Panasonic, Nichicon, Rubycon and Vishay Caps.








































 

derek92994

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#10
You certainly are getting better...
Well, no smoke, and not a single capacitor put in the wrong way (yet) :evil4:

However, I will admit after recapping the Nakamichi 480 (Just the power supply section), I have lost all tape functions after 8 hours run time, and a burning smell was evident. I reached for the power cord real quick. So that one is in the naughty corner, which I will revisit to trouble shoot. Yep, shit does happen :la:
 

Fishoz

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#11
Hey D2...you got many hours into already, why stick it in the naughty corner? Hit it while it’s fresh! Could probably smell where the heat was.
 

derek92994

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#13
Hey D2...you got many hours into already, why stick it in the naughty corner? Hit it while it’s fresh! Could probably smell where the heat was.
There were too many other naks with higher ranking that required work. I did try to trace but knew i could gain much more by completing the others first. I will come back to it and sort it out.
 
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