The Rabco/HK Turntable

[Arthroscope]

Karma,
I have a ST7 I bought for parts ( I needed a tone arm), a ST7 that was factory retrofit and a ST8. I got the 7 running so now all are operational. I posted a few photos of the factory retrofit a while back so you can search my posts to see them. There must have been a number of problems with the 7as HK was making the modifications on the 7 for free. The main difference between the 7 and the 8/factory altered 7 are a rotating upper tracking arm and the roller is metal. I have done AB comparison between 7 and 8 and I cant really say there is a difference. There is a tweeking period but after fine tuning the reliability is excellent.
They are certainly a fan base of these things. And those which hold them in contempt. Play with it and see which you are.

 

[Ant1-Hero]

I recently acquired an ST-7, It needs new belts and I'm sure the drive wheel. Honestly are these worth fixing up or should I get it running and sell. It's in mint condition sitting in a box. I need to check what model # it is. I did notice that when turned on the motor had noise, I may need to find a replacement if anyone has suggestions. And also the red light doesn't turn on in the off position.

It is a really nice looking table though.

 

[Karma16]

HI Arthroscope,
The only comtempt I hold was for those early ones that didn't work and were the only ones I had first hand contact with. I do hold HK responsible for pushing the early ones on the public and dealers that obviously did not work. That is close to theft as far as I'm concerned. Shame.

As for my needs, I have no needs. I have two great Eminent Technology ET-2.5 air bearing arms that I would not trade for anything.

I started this thread as a fact finding expedition. In that sense, I think this has been a great thread. I have learned a lot. I now see that my early experience was not the final story. I now see that you fans are not crazy. I now see that that my original enthusiasm was not misplaced and the design was solid. It's too bad that the basic idea has parished.

A last question. What sort of cartridge set up calibrations are provided. For example is VTA adjustable? I suspect not. Please educate me.

Also, the ST-4 looks interesting. Does anyone know if it was any good?

Sparky

 

[Pio1980]

Cart set-up was with spacers via a jig that also set tangency without need of a radial grid plate. There was no other VTA provision. Tire on tracking shaft sets the vertical of the arm gimbal, smooth evenness is critical for operation. As with any other arm, the correct set is for the cart top to be perfectly parallel with the record surface, changing the roller tire may well change the relationship with the jig and render it only useful for setting the tangency without a radial grid. It is not that difficult to set up without the jig if one understands the point of the procedure.

 

[Splatter Pak]

I had one, I think an ST-5, and it was a waste of $125. In time I saw that it was going to need almost constant tweaking, so I got rid of it. Other linear trackers had other problems, and the only one I really loved was a B&O 4004 which I recently swapped off too cheap.

 

[Pio1980]

Re the ST-4, it may have proved simply unproduceable. It looks like it may have been the first of the rotating shaft /skew wheel drives.

 

[dshoaf]

For those with motor noise, I'd check into 2 things to eliminate as potential problem areas:

- Tantalum caps: There are about 3 or so, IIRC, on the motor's own circuit board. I'd suggest their replacement due to tantalums of that era being failure points.

- There is a setup procedure for the motor to get the drive belt to sit centered in the motor pulley. I's suspect some noise from a belt chattering as it tries to pop out of the pulley's race.

- Lastly, that belt needs to be good and tight, too. Anyone using original belts, even though they look ok, are likely well-stretched. I had all sorts of problems with wow until mine was replaced. Go ahead and swap out the tonearm roller belt while you're at it. There's a guy on eBay who sells the kits, which I used.

Cheers,

David

 

[Pio1980]

I think the ST-5 has an A/C shaded 4-pole motor.

 

[Karma16]

I had one, I think an ST-5, and it was a waste of $125. In time I saw that it was going to need almost constant tweaking, so I got rid of it. Other linear trackers had other problems, and the only one I really loved was a B&O 4004 which I recently swapped off too cheap.

HI Splatter,
I agree. I loved my 4004 too. A great and beautiful machine. It's only problem for me was I wanted to go to low output MC's which was not possible with the 4004. So I went with a Yamaha PX-2 which allowed any cartridge to be mounted. I liked it a lot too but nothing can beat the sophistication of the B&O linear trackers, IMO.

Sparky

 

[Phototone]

Re the ST-4, it may have proved simply unproduceable. It looks like it may have been the first of the rotating shaft /skew wheel drives.

The ST-4 (I have 2 of them) is even more reliable than the HK versions. It doesn't need any adjustments, or require any. It is a rotating shaft/skew wheel drive, all above the top plate. The Arm just sits on the tracking shaft. You can lift it right off, to clean or inspect. End of record lift is via a mirror reflecting light to a photo diode thing.

If the ST-5 thru ST-8 are set up well, and do not have a bad tracking roller, or belts, then they can operate for years trouble free.

 

[dnpainting]

Does anyone know the size o ring roller I need for the ST-7?

The size I used was a #8 O-Ring from home depot. 9/16O.D. x 3/8 I.D. x 3/32. I bought in a package of 10.

After I did my repair on my ST-7, it took a while to get everything adjusted properly, I ran 1 complete album on it and it tracked fine. Not leading or lagging behind at all, well, only from what my eyes could tell. I have since set it aside for the time being until I get the new belts ordered and my garage set-up better. I tell you what, once you start collecting vintage gear, it's hard to stop. I keep clearing out more wood working tools. My wife even asked if we need to get a bigger house, and she wasn't joking.

 

[Karma16]

HI dnpainting,
Collecting turntables in particular. They take up a lot of storage space. As much as I love turntables and tone arms, I have managed to not collect them. At the moment, I have two, both installed in my system. I might add a third. If I do it will be a TD125. My Aesthetix Rhea phono preamp allows three to be plugged in. I see those empty RCA's on the real panel and they call to me. "Fill me, fill me" they moan. If I can get a good deal I probably will.

Sparky