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Harman Kardon ST-8 revisions

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Plexicube

New Member
Hello!

A few years ago I got bitten by the linear tracking turntable bug. There's something exciting to me about seeing all the different ways that various companies solved the problem of tonearm movement. The HK/Rabco design is one of the most interesting to me, in all of its low-tech glory. I have repaired a few of these over the years but recently ran into something interesting.

My first run-in with the ST range was the ST-7 which used the first iteration of the design: a static, non-rotating upper bar. I acquired an ST-5 later on and noted the published improvements, namely a new grooved wheel at the far right side of the upper bar rotated via a belt attached to the lower rotating barrel. Everything I had read indicated that this was the mechanism that also powered the ST-8 and any factory retrofit ST-7s.

Imagine my surprise when recently repairing an ST-8 upon finding a very different mechanism than I had previously seen. In this model the upper bar is half length (not continuing under the shroud on the left) and the rotation is derived from a wheel on the *left* side attached to a grooved pulley on the rotating barrel that doesn't exist on any other model I've disassembled. I haven't been able to find any information at all about ST-8 revisions, but I'd assume this is a later model. There are also differences in the tonearm from the ones I have seen before, with a ribbed cartridge hood that extends further than the flat sheeting metal of teh previous version.

Has anyone else noted these differences?
 
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Hello,

I too was surprised to see this change, from the ST-7 to the ST-8, and then to the ST-5. The ST-5 configuration requires a substantial dis-assembly to replace the upper belt, whereas the ST-8 belt replacement can be made quite easily.

The other interesting ST-8 change I've found is in the height of the chassis (the black aluminum vertical housing / outer shell). I have two ST-8s, one where the black shell is 2-5/8" high, and one where it is 2-1/4" high - which is the same as that on the ST-7s and ST-5s.

The Harman Kardon name is printed on the left side of the front face in the shorted version and on the right on the taller.

Upon further study, the actual chassis, with all components, are exactly the same. The difference is that the taller housing is mounted to the bottom chassis plate about 3/8" lower, so on the taller version the bottom of the housing is flush with the bottom of the chassis plate, whereas on the shorter housing is mounted flush with the lip of the chassis plate, which, due to the bowl-like character of the bottom plate is about 3/8" higher than the middle of the plate. So the tops of the two turntables, with the feet on, are at the same height. as are all components, etc.IMG_3539.jpg
 
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Note: I am on the lookout for certain ST-5/7/8 parts, including spare tonearm/wand, original ST-8/ST-5 adjustable feet, original ST-8/5 adjustable foot rubber wrapper and dust-cover hinge brackets (that fit on the cover).

And, I have some original and 3D printed parts, notably ST-5 lever trim, ST-7/8 speed adjustment trim, adjustable feet (pretty nice, if I do say so myself), adjustable foot rubber wrapper (flexible and also pretty nice), and (this is cool) a replacement AirPot plastic base.

And, a partial ST-7 chassis with transformer, power switch, strobe, main circuit board, top plates, voltage changer, roller bar, pulley and a few other parts.
 
If you're the DIY sort, I can send you a replacement airpot base that I 3D printed, worth a shot. You'd need to run a glue bead around the joint between the glass and the base. Shown along with bits and pieces of the old base. Alternatively, I can send an STL file for you to 3D print your own.
IMG_3543.jpeg IMG_3542.jpeg IMG_3541.jpeg IMG_3540.jpeg
 
My ST-5 upper roller belt is also on the right and on my ST-8 is on the left. Also the case on my ST-8 is 2 5/8". Haven't seen an ST-8 with a 2 1/4 case like my ST-5, rather interesting. My ST-5 has the clear cover and my ST-8 the dark smoked cover. I see ST-8's on ebay with clear covers but they might be after market as I thought all ST-8's came with the dark covers. I also had to make an air pod for the ST-8. Used part of the old one and added a few homemade parts, works great. The 5 & 8 are great tables. It's too bad the ST-6 and St-7 gave them a bad name. My 5 & 8 are really set it and forget it, but their earlier reputation did them in.
 
I suspect you are correct, ST-7/5s had a clear dust cover, ST-8s were smokey.

I've heard that the aftermarket dust covers are also available in smokey for an extra $10, but haven't investigated.

I'm only slightly embarrassed to say I have a few too many ST-7s and ST-5s, but fixing all the little details is great fun for me. Nice to see a few others who appreciate these mechanical works of art.
 
JHK said:
I suspect you are correct, ST-7/5s had a clear dust cover, ST-8s were smokey.

I've heard that the aftermarket dust covers are also available in smokey for an extra $10, but haven't investigated.

I'm only slightly embarrassed to say I have a few too many ST-7s and ST-5s, but fixing all the little details is great fun for me. Nice to see a few others who appreciate these mechanical works of art.
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Suffice to say, I'm that guy also. I enjoy the hunt finding tables, and then repairing them. Admitedly I own an early ST-7 (that is perfect funtioning), an ST-7 factory modifed/upgraded, and lastly my last acquistion an ST-5, along with eight wands and a collection of vinatage cartridges.
 
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