Hitachi SR-903 Restoration

Fredrik 1977

Super Member
So i´m back with my receiver threads:D i finally got some time to dig in to this one!
after my last receiver thread the DUX-TA-12000 there was a vote on what i should restore next and this one was the winner:)

anyway here it is. its sort of working, it clicks (good sign), but it takes awhile before any music is coming through, i bet that will be sorted out along the way as we go. according to previous owner it has been in for service where they "lubed the relay"? yeah right! think i´ll just replace it:)

i think this unit really means business! judging by the looks of things!
bet this will be a killer once finished.

as allways: i go in to this with the intetion to totally recap it, replace any crap trannys i find, and also have a look at the signalpath where i will replace any tantalums/lytics for wima MKS2. but there is allways something more to do.

feel free to come with ideas on how to make this monster a top performer.

here she is, with some broken bulbs,
im not shure but i think the wood cabinet is spay painted black. could be stock also.
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thats a pretty heavy transformer right there!...along with the two 6800/80V maincaps. i will up these atleast to the double uF
also visible is some sloppy selector lamp replacements, just some white electrical tape :thumbsdown:
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strange looking pcb! but i believe its factory mounted
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PowerAmp, the heatsink is screwd to the backplate wich is made entirely of aluminum
there is 2SB611/2SD581 TO-3´s AND 4x batwing looking trannys along with 4xTO-220 ( probably the drivers) thermally connected to the heatsink. and a thermal fuse in the middle?
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and down under we find.....well the usual:)
also here you can see the aluminum backplate
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Psu/Protection: looks very serious
that big can is a dual cap, this might turn out to be a problem once i start to make the order for parts.
some sort of modification is probably required to accommodate 2 regular caps
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more relays
upper half of the pcb must be the phono stage?
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Looks like there may be a few 'surprises' coming... :lurk:

i´m afraid your right:) lets hope they will be nice surprises.


also i have been poking around a bit and trying to set up a list of what i need and MAN! there are a lot of 2SC1344/C1345 havnt counted em yet but its gotta be atleast 20 of them.
also 2SC1451 on the main amp pcb.

so i have some work to do.
 
i´m afraid your right:) lets hope they will be nice surprises.


also i have been poking around a bit and trying to set up a list of what i need and MAN! there are a lot of 2SC1344/C1345 havnt counted em yet but its gotta be atleast 20 of them.
also 2SC1451 on the main amp pcb.

so i have some work to do.
Hmmm...Where have i seen the 2SC1451 before...Cough Cough Pioneer time bombs Cough
 
made about half the list, now i need to access the preamp and in order to do that i have to pull the face plate, and in order to do that i have to get the bloody tuning knob off the damn axle.
i unscrewed the hex screw holding it and the knob was somewhat loose but as soon i started pulling it off its axle it got more and more stuck....so im stuck :)

i tried holding a steady grip on the flywheel with one hand and the knob in the other, tried to turn it on the axle and pulling at once. and let me tell you im a pretty big/strong guy (worked in construction and factories all my life,) but MAN! that thing is on there!!

have to grab some bigger tools! im afraid im gonna have to destroy the knob.
 
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i´ve checked the hole with a flashlight and i can see the axle in there.

shure i have come across knobs before that ppl glued and what not but this is insane:)
 
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Steam or boiling water on the knob - may expand it a bit / soften any glue in there ?
WD40 or a solvent into the hole ?

...... otherwise, Carlsberg ?
 
F%¤K! me....

been sweating it out for an hour with this, tried 2 beers, CRC 5-56, and a plumbing wrench :D
i have gotten it so far off the axle that i dont see it in the hole anymore...must take a break and attack it again. this sucker aint gonna get the chance to gather strength, regroup or what the heck its up to..

man this is like working on an old car
 
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Strange - I can't think of a glue that wouldn't have surrendered long ago - it must be mechanical.
Maybe galvanic corrosion ? or an extra metal 'shim' wedged in with the pot shaft ? something fairly solid in any case....

Must be one of the surprises...... !
 
yeah surprise surprise!:)

i have been struggeling about 20min more now and its not gonna come off!

think i´ll move the project out to the garage and show this one a thing or two about surprises. see i got some to:) its spelled anglegrinder :D
think i´ll split the knob right by where the shaft goes. trying to miss the shaft:)

the knob is massive aluminum. i will be able to make a new knob at work. only it wont get the decorative grip pattern. or i have to find some spare part (highly unlikely)

i dont see any other way out of this.
prying wont work! not with the forces involved here. i would pry out the whole assembly holding the shaft and flywheel.

surprise #1
note: faceplate is unscrewed therefore things look a little strange.
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If it's that bad - maybe drill the centre (onto the end of the shaft) and make up / use a puller ? might still be more or less salvageable then.
 
not a bad idea!
i´ll see what pullers i might be able to get. might be able to make one.

knob had some dings a scratches from the start and the shaft was a little wobbly, so i think its gotten a blow sometime in the past


(pic above after you answered)
 
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ok anglegrinder might be a little drastic i concur:)

i´ll try drillig the center and see if i can get it off. anyway knob will be scraped. might use it as a heatsink instead:)
 
If you drill a hole dead center in the front of the knob with a tap drill for a 8-32 or a 10-24 tap and then tap threads in it and use a screw to jack it out. You can plug the hole later with a piece of alum. threaded rod or find an alum. screw. Cut it off a little long ,maybe a 1/32" and peen it over so its tight and file it. Won`t hardly be able to tell hole was there. Can lightly sand blast the knob and that will help hide it and give it some finish too.
 
great ideas both! will hook up the drill tomorrow.
i´ll try to thread it first and if that dont work out i´ll build some puller.
 
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