Details of differences between Harman Kardon Linear Tracking tables ST-5/ST-6/ST-7/ST-8

[JHK]

There is a previous thread that has a few of the differences between these tables, but is light on details. As I've had several of each of the ST-5 through 8 series, and have answered a lot of questions on eBay and asked a few on AK, I thought to contribute a little information here. Will do this over a few posts to this thread, feedback is my primary reason for doing this, you likely know something I do not, so feel free to comment, correct, add, etc.

General:

• As best as I can tell, the sequence is ST-7, ST-8, ST-6, ST-5. But, it could also be ST-7, ST-8 as one series, and ST-6, ST-5 as another. Anyone know any better?
• The ST-8 had the (generally) same chassis / side wall, top plates and back cover as the other models, but was black anodized aluminum rather than brushed satin aluminum.
• All used the same basic linear arm drive mechanism: carriage riding on a tracking wheel riding on a tracking roller, angle of wheel tunable for speed of tracking

Motor / drive mechanisms:

On / off

• The ST-7s and ST-8s had a power switch under the front of the chassis, basic on and off.
• The ST-5s and ST-6s had a rockwer power switch on the top of the table.

There were two basic mechanisms for driving the system:

• Papst GS 38-09 - German manufacture, Hall effect sensor for speed feedback-loop - dual speed motor, with potentiometer controlled gross speed on the motor board, and individual speed controls accessible from the top plate for 33 RPM and 45 RPM fine tuning. Speed was adjustable with visual feedback from a mirrored strobe that displayed an under-platter pattern to provide visual feedback to fine adjust. This motor has been reported to be subject to speed variations, possibly due to small variations in line voltage. The under-platter pattern was either a paper pattern glued to the platter, or later a platter with the shiny dot patterns etched into the aluminum with a black background. Typical dots move to the right, slow it down, to the left, speed it up, using the fine controls. Single diameter belt pulley, two speed motor.
• Unknown mfg single speed synchronous motor, sync'd to line frequency. Not strobe feedback or adjustments, assumed to be line-frequency perfect. Used a two diameter belt pulley on the motor, and a mechanical system to move the belt from one diameter to the other.

Visual speed pattern - The visual speed pattern detection mechanism is worth discussing

• There were four circular patterns under the platter for the ST-7s and ST-8s
  • 33 RPM - 60 cycle mains
  • 45 RPM - 60 cycle mains
  • 33 RPM - 50 cycle mains
  • 45 RPM - 50 cycle mains
• The strobe was a simple 120v neon bulb, which switched on and off at a frequency depending on mains frequency
• There was a mirror that reflected the strobe light off the white/shiny dots into the viewer's eyes. The parts shipped with the TT's had a black peel-off label that the owner was instructed to place over the near or far part of the mirror in order to provide only the appropriate mains frequency reflection. Very clever.

33/45 RPM Speed selection:

• As stated above, the ST-7s and ST-8s had a two speed motor. The speed selection control was powered via three under-lit touch sensitive switches. Each switch had two small round metal terminals that when both touched would trigger the 33, 45 or off speed control. These touch controls became less sensitive over time, and now often require licking your finger before they will detect a touch. A fairly large circuit board handled this, and the motor speed control.
• Also stated above, the ST-5s and ST-6s had a lever that manually forced the belt up or down on a dual diameter pulley, effecting the platter speed. No fine adjustments.

Tonearms:

• The tonearms are interchangeable across models
• The ST-8 had a black knurled coupler, and the other models had a grooved silver one.
• There were two styles of head shells, one flat metal, the other corrugated sides - not sure if there was anything except a cosmetic difference.

Logo:

• All models I've seen of the 5s and 7s have the Harman Kardon name on the left front side panel.
• Some of the ST-8's had the name on the right of the front side panel.

Chassis / side-panel height

• Some of the ST-8's had a different side panel height, which was mounted on the chassis at a different height, and so the platters ended up at the same overall distance from the bottom of the feet

Feet

• The ST-7s had non-adjustable feet, silver, held onto the rubber isolators by a screw that fit into the feet.
• The ST-6s, ST-8s and ST5s had adjustable feet that friction-fit into the rubber isolators

Muting Circuit

• The ST-8's had a muting circuit, which was a simple straight-through relay delay triggered by a microswitch that was tripped when the cueing plate descended.

Cueing Dampener

• The ST-5s, ST-6s and ST-7's had a slow needle-drop cueing mechanism used a DashPot - an automotive carburetor deceleration (well, negative acceleration) dampener (really, look up DashPot Ford). DashPot's are still available today, because, well, cars.
• The ST-8s used an AirPot, made by AirPot company, and still available, although very expensive, and you might have to wait until the make the next product run.
• If you have an ST-8 with an AirPot with a broken base (very common), I have 3D printed replacements, into which you can insert the glass sleeve, and seal.

Slide Rod mechanism

• The carriage or the carriage tube rides on the slide rod, without lubrication and on Delrin bearings / bushings. On the ST-7, this rod was fixed (via set screws in each of the LH and RH support pillars), and HK determined that there was a very small amount of static (resting / non-moving) friction that could limit the smoothness of the linear travel. So they incorporated a belt / pulley system driven off the tracking shaft. This came in two flavors:
  • The ST-5s and ST-6s had a groove cut into the right side of the tracking shaft as one pulley, and a plastic friction fit pulley on the slide rod, same right side.
  • The ST-8s cut a groove in the tracking shaft pulley, moved the set screws, and used a shortened slide rod that only went between the center and the RH support pillars.
• The slide rod then rotates continuously, eliminating any moments of rest, eliminating the conditions of static friction and smoothing out the linear travel.
• A rotating slide rod is not necessary to the successful operation of the linear tracking, but it makes it better.

End-of-record detector

• The ST-8's end of record detection utilizes an LED, a photo-cell, and a simple circuit to detect the increased angle of the tonearm as it encounters the "fast" groove at the end (inner circle) of the record, moving the cartridge faster than the linear tracking.
• The ST-5s, ST-6's and ST-7s utilize a very sensitive mechanical lever that pushes the pin into the end-of-record gears and triggers the EOR process.

Carriage Guide

• The ST-7s used a ???? that rested on the guide rod to help keep the carriage in straight alignment
• The other models used a Delrin carriage guide that wrapped around the tracking roller and kept the carriage in straight alignment

Roller Cover

• There were two types of roller covers, one all black "RABCO" lettering, and one with silver lettering
• This roller cover is critical to the accurate operation of the tracking / cueing. It spreads the 4 little springs, providing tension to the tone arm roller. This cover must be snapped into place to provide this tension. To do this, push down on the counterweight rod and the back of, and the tonearm at the front of, the carriage assembly (this spreads the tone arm roller slightly), and simultaneously snap the cover into place. Look at it closely first to proper align, it should snap in with only a small amount of spreading pressure.

Whew. Have I forgotten anything? Of course. If you have other / additional information or corrections, please add to this thread.

 

[JHK]

Dust Covers

• ST-8s had a smokey, but transparent, dust cover. that had a black rubber edging on three sides.
• The others had clear dust covers, with usually two small short rubber seals that acted like bumpers so the lid wouldn't slam.

International - ST-7 and ST-8 only

• The ST-7's and ST-8's had voltage switches, that allow main voltage selection of 200v, 220v, 110v, 117v to adapt internationally. And therefore had a more complex main transformer.
• There is no method to switch mains frequencies, that is managed by the strobe mechanism.

 

[JHK]

Tracking Roller

• The ST-7 had a Tracking Roller that was an aluminum wheel, with a rubber tire. The rubber tire often disintegrated over the years, turning to a thick jelly-like goo. The few that I've seen intact have a square cross section. This mess can be cleaned up with IP alcohol, and the tire replace with either a #31 O-Ring, or a Buna-N 70 Duro Square O-Ring (my preference) - 3/8"ID X 5/8"OD X 1/8"CS. To be clear, the #31 is the much more popular replacement - any hardware store.
• The ST-5s, ST-6s and ST-8s all had a steel Tracking Roller. There is a thread comment from Frank Baudile, Project Engineer for the ST-7, in which he stated that the engineers expected the steel wheel to create rumble or extra noise - metal on metal - and that this was not the case.

• Replacing the rubber tire on the ST-7 Tracking Roller isn't simple, but it is straight forward. My experience (done this 5-10 times) has lead me to spend the time up-front taking the Tracking Shaft out of the carriage for easy access to the Tracking Roller, as opposed to spending a whole lot more time trying to get my fingers and tools into the tiny space. You only need a few tools, a nut driver, a small Allen wrench for the left pulley, right gear and slide rod set screws, and maybe tweezers; 7" surgical forceps help putting the roller back in - not strictly necessary. There are these important details:
  • There is a hidden set screw beneath the top mounting screw of the "Cover, R.H.", the thin trim on the right hand upright.
  • Once the Tracking Shaft has been freed from the carriage, be careful not to stress or break the tiny audio wires
  • I haven't had any luck loosening the bolt that keeps tension on the Tracking Roller Bracket, it's got loctite on the nut I believe. So I carefully and gently pry the bracket apart at the rounded bottoms, and the roller falls out.

 

[JHK]

Bubble Level

• The ST-5 and ST-8 had a circular spirit Bubble Level added to the upright Left Hand cover (named "Cover, L.H." in the Technical Manual)
• The ST-6 and ST-7 did not have adjustable feet, and did not have a bubble level (note at least one ST-6 exception below).

Dates - these dates have been extrapolated from dates on ads and reviews, on Tehnical Manuals and on Owner's Manuals. HK archivist / librarian has confirmed them approximately.

• ST-7 : early 1975
• ST-6 : early 1976 (marketed as a less expensive alternative to the ST-7)
• ST-8 : probably late 1978 early 1979
• ST-5 : 1979

Important notes:

• Some of the above information on ST-6s was based on a late model ST-6 that I have which is far closer to the ST-5 than the earlier models of the ST-6 which are much closer to the ST-7. The pictures of the ST-6, and the technical manual, show non-adjustable feet, a carriage guide, a volatge adjustment, no Slide Rod turning mechanism, etc.
• The Technical Manual for the ST-6 shows that the power cord, and the main motor pulley, have both a domestic and an export version. This is likely how HK handled the 50Hz/60Hz differences.

 

[Blue Shadow]

Nice compilation.

Enjoyed using the ST-7 in the mid-late 70s. The table for the house of 5 plus visitors that were always playing tunes. It performed very well even with all the different users.

 

[rread13]

Tracking Roller

• The ST-7 had a Tracking Roller that was an aluminum wheel, with a rubber tire. The rubber tire often disintegrated over the years, turning to a thick jelly-like goo. The few that I've seen intact have a square cross section. This mess can be cleaned up with IP alcohol, and the tire replace with either a #31 O-Ring, or a Buna-N 70 Duro Square O-Ring (my preference) - 3/8"ID X 5/8"OD X 1/8"CS. To be clear, the #31 is the much more popular replacement - any hardware store.
• The ST-5s, ST-6s and ST-8s all had a steel Tracking Roller. There is a thread comment from Frank Baudile, Project Engineer for the ST-7, in which he stated that the engineers expected the steel wheel to create rumble or extra noise - metal on metal - and that this was not the case.

• Replacing the rubber tire on the ST-7 Tracking Roller isn't simple, but it is straight forward. My experience (done this 5-10 times) has lead me to spend the time up-front taking the Tracking Shaft out of the carriage for easy access to the Tracking Roller, as opposed to spending a whole lot more time trying to get my fingers and tools into the tiny space. You only need a few tools, a nut driver, a small Allen wrench for the left pulley, right gear and slide rod set screws, and maybe tweezers; 7" surgical forceps help putting the roller back in - not strictly necessary. There are these important details:
  • There is a hidden set screw beneath the top mounting screw of the "Cover, R.H.", the thin trim on the right hand upright.
  • Once the Tracking Shaft has been freed from the carriage, be careful not to stress or break the tiny audio wires
  • I haven't had any luck loosening the bolt that keeps tension on the Tracking Roller Bracket, it's got loctite on the nut I believe. So I carefully and gently pry the bracket apart at the rounded bottoms, and the roller falls out.

Before letting the tracking roller pop out, I have taken a red sharpie and put a dot on the right side so I can put the trackiung roller back in the same orientation it was before assuming it was in the correct position to start with.

Excellent write up you have put together about our beloved Harman Kardon/Rabco turntables!

I've restored quite a few myself, in fact the last ST-7 I bought I did a bunch of upgrades to make it my own "factory refurbished/upgraded ST-7":

1) Installed 3-D printed reproduction adjustable feet ala the ST-8 and ST-5.
2) Upgraded/Installed the Upper Rolling Rail and Lower Roller Assembly along with the metal tracking wheel from a parted out ST-5.
3) Replaced the stock tracking adjustment with a Knurled Knob Thumb Screw.
4) Replaced the OEM RCA cables with new high quality custom made 4ft. Mogami black nylon sleaved cables, RCA connectors, and ground cable.
5) LED light upgrade for the touch controls and end of record pickup lamp. I soldered 1/4w 330-ohm 5% tolerence resistors to the blue and green lamps sockets underside the board with heatshrink where needed to prevent shorts.
6) Recapped the main control board, the power input section, and the Papst motor board with a kit sold on Ebay from a reliable electronics enthusiest.

Now this table has become my daily use table with these upgrades and is working extremely well. The next thing to do is polish out some small scratches on the dustcover lid. I have a total of three restored ST-7's, one was factory upgraded I believe??? But it did not have the adjustable feet, nor the steel tracking wheel. Years ago I found some Kenwood adjustable feet that fit with zero modifiaction, the steel tracking wheel tire is now the flat tire version. The other ST-7 is my oldest one I acquired it back in the mid 90's, this one is still stock to the OEM designs with a new #31 washer for the tire, lot's of tweeking then when I restored it, it was a super smooth working table. I intend to gift one of my ST-7's or possibly the ST-5 to my best friend whose gotten back into vinyl with his son in law also. My problem is we now live accross the country from each other, I moved from Florida when my parents passed away suddenly this past February and March. I now live in Idaho and will either ship it to him or wait and drive out in the coming spring and bring it with me. I don't know if he can handle putting this one in playable condition himself with out me there to help. Before I moved I gave him a working Sony PS-LX520 table that is so easy anyone can use, and the ST-7 needs more experience to setup.

 

[Sam Cogley]

Unknown mfg single speed synchronous motor, sync'd to line frequency. Not strobe feedback or adjustments, assumed to be line-frequency perfect. Used a two diameter belt pulley on the motor, and a mechanical system to move the belt from one diameter to the other.

Was it the Borg Death Cube? I think those were made by General Industries.

 

[JHK]

Before letting the tracking roller pop out, I have taken a red sharpie and put a dot on the right side so I can put the trackiung roller back in the same orientation it was before assuming it was in the correct position to start with.

Excellent write up you have put together about our beloved Harman Kardon/Rabco turntables!

I've restored quite a few myself, in fact the last ST-7 I bought I did a bunch of upgrades to make it my own "factory refurbished/upgraded ST-7":

1) Installed 3-D printed reproduction adjustable feet ala the ST-8 and ST-5.
2) Upgraded/Installed the Upper Rolling Rail and Lower Roller Assembly along with the metal tracking wheel from a parted out ST-5.
3) Replaced the stock tracking adjustment with a Knurled Knob Thumb Screw.
4) Replaced the OEM RCA cables with new high quality custom made 4ft. Mogami black nylon sleaved cables, RCA connectors, and ground cable.
5) LED light upgrade for the touch controls and end of record pickup lamp. I soldered 1/4w 330-ohm 5% tolerence resistors to the blue and green lamps sockets underside the board with heatshrink where needed to prevent shorts.
6) Recapped the main control board, the power input section, and the Papst motor board with a kit sold on Ebay from a reliable electronics enthusiest.

Now this table has become my daily use table with these upgrades and is working extremely well. The next thing to do is polish out some small scratches on the dustcover lid. I have a total of three restored ST-7's, one was factory upgraded I believe??? But it did not have the adjustable feet, nor the steel tracking wheel. Years ago I found some Kenwood adjustable feet that fit with zero modifiaction, the steel tracking wheel tire is now the flat tire version. The other ST-7 is my oldest one I acquired it back in the mid 90's, this one is still stock to the OEM designs with a new #31 washer for the tire, lot's of tweeking then when I restored it, it was a super smooth working table. I intend to gift one of my ST-7's or possibly the ST-5 to my best friend whose gotten back into vinyl with his son in law also. My problem is we now live accross the country from each other, I moved from Florida when my parents passed away suddenly this past February and March. I now live in Idaho and will either ship it to him or wait and drive out in the coming spring and bring it with me. I don't know if he can handle putting this one in playable condition himself with out me there to help. Before I moved I gave him a working Sony PS-LX520 table that is so easy anyone can use, and the ST-7 needs more experience to setup.

Hi Rick, I never realized there was any handed-ness to the tracking roller; got out my calipers and while small, there is a difference. Learn something new every day.

I've got an almost complete ST-7 hardware upgrade kit, but adding the bubble level to the Cover, L.H. requires drilling a hole in the top, and I'm not yet that adventerous. I have the level, but would need to fabricate the spring retainer.

Can you tell me more about the adjustable feet (unless, of course, you got them from me).

And, how do you polish the lid? I've always been hesitant to try anything, figuring I'd make it cloudy with tiny scratches.

I'm near the end of restoring an ST-8 I just got: one new foot grip sleeve, a motor adjust to eliminate a (very loud) clicking, and just finished replacing the AirPot base with a newly printed 3D replacement. Beautiful machine.

 

[JHK]

Not all Tracking Roller Tires disintegrate, here is an original in great condition, alongside an updated one:

 

[JHK]

And here are pictures of a PETG 3D Printed AirPot base, along with disintegrated original base. I use Loctite PolySeamSeal to seal the glass cylinder to the base, air tight like new.

 

[rread13]

Hi Rick, I never realized there was any handed-ness to the tracking roller; got out my calipers and while small, there is a difference. Learn something new every day.

I've got an almost complete ST-7 hardware upgrade kit, but adding the bubble level to the Cover, L.H. requires drilling a hole in the top, and I'm not yet that adventerous. I have the level, but would need to fabricate the spring retainer.

Can you tell me more about the adjustable feet (unless, of course, you got them from me).

And, how do you polish the lid? I've always been hesitant to try anything, figuring I'd make it cloudy with tiny scratches.

I'm near the end of restoring an ST-8 I just got: one new foot grip sleeve, a motor adjust to eliminate a (very loud) clicking, and just finished replacing the AirPot base with a newly printed 3D replacement. Beautiful machine.

JHK,

Are you "HeKickedMe" on Ebay?

I bought small bubble levels off of an Ebay seller out of China last year. First I measured the original with calipers checking the size, took a measurement on the ST-7's rail cover for placement and clearence in the underside where the spring clamp rest. I drilled out the hole using smaller sizes to start and stepping up as I went along. I used a clear sealant, actually "Shoe Goo" and a cutoff a cotton ear swab to dab the sealant around the bubble level.

The 3-D reproduction feet came from you then and I finally installed them on one of the tables I worked on. I bought the feet 2-years ago and had them in waiting for use. The ST-5 Transport Upper Rail and Lower Drive Cylinder I also bought from you too. The swap upgrade was super easy, and did not need hardly any tweeking adjustment wise to get the ST-7 working correctly. The 3D feet once installed in place on the ST-7 tables original rubber mounts, I used the Shoe Goo to hold the rubber mount top side in the ST-7 in place so as not to spin. The only way I discovered to install your feet was to gently pry out/off the original feet and remove the silver plastic feet, and then gently work the 3D foot on the rubber donut, and then do the same when working the rubber donut back into the ST-7's base. I was surprised the rubber held up, none tore apart.

As for polishing the dust cover(s) I have worked on at least four or more? Depending on how deep the scratches are, if you can feel it with your finger nail then you are going to need to do some sanding first. And if sanding then you are Wet Sanding with Black Emory Sand Paper the grades go from low number (course) to high (fine). The lids condition will kind of require some trial and error to see how aggresive you go with the wetsanding. On some lids I have had to start with 400, then move up to 600 or 800 and work with till the scratch's start to disappear. Eventually you are using very fine 1000, 1500 and higher up to 2000 if you can then once satisfied with the condition you can then begin using automotive headlight polishing products and paint compounds the red to the white for clear coat finish. Once at the final stage I've used the drill with the sponge and final polishing to try to get optically clear results. The final steps when there, you then use a clear sealant and buff with a synthetic fiber cloth. It's time consuming but the results are soo satisfying!

I have this to do to two dustcovers, I'll post pictures soon of my efforts.

 

[rread13]

Not all Tracking Roller Tires disintegrate, here is an original in great condition, alongside an updated one:

I've never come accross an ST-7 original Tracking Roller that hasn't turned to goo like your third picture. It's got to be from a table that has always been in moderate tempetures I would guess? Of course we are lucky the engineers based this rubber tire on a readily available plumbing part we can buy still today!
Either the round donut #31 or the Flat Tire version that number escapes me from memeory, mine are stored together in the #31's clam shell.

 

[rread13]

And here are pictures of a PETG 3D Printed AirPot base, along with disintegrated original base. I use Loctite PolySeamSeal to seal the glass cylinder to the base, air tight like new.

It must be nice to have the 3D printer at your disposal to make virtually any part you need!

When I repaired my ST-8 table the Airpot Base was brittle and disentegrated into pieces. I used some round rubber feet that had a good snug fit with the bubble side twisted into the glass and some superglue on the interior to make it airtight, then some 3M foam tape to secure it to the base of the ST-8. It worked on my table and a (now) friends that trusted me to work on is table. Do you still make this part from time to time to sell on Ebay? Or could I have you make one I can send to my friend if he'd like one to potentially use on his table? I unfortunately sold mine some years back, and when I was ready to buy one again, I could not find a reasonably priced one and bought a ST-5 that I worked on bringing back to life.

 

[Celadon]

Informative post, very nice.
I had an ST-7 years ago, really regret selling it.

Remember, it had the designer and peoples names who worked on the production, on it, maybe under the plinth….

 

[JHK]

It must be nice to have the 3D printer at your disposal to make virtually any part you need!

When I repaired my ST-8 table the Airpot Base was brittle and disentegrated into pieces. I used some round rubber feet that had a good snug fit with the bubble side twisted into the glass and some superglue on the interior to make it airtight, then some 3M foam tape to secure it to the base of the ST-8. It worked on my table and a (now) friends that trusted me to work on is table. Do you still make this part from time to time to sell on Ebay? Or could I have you make one I can send to my friend if he'd like one to potentially use on his table? I unfortunately sold mine some years back, and when I was ready to buy one again, I could not find a reasonably priced one and bought a ST-5 that I worked on bringing back to life.

I'll look over the ones I printed, should be able to find a really good one.

JHK,

Are you "HeKickedMe" on Ebay?

I bought small bubble levels off of an Ebay seller out of China last year. First I measured the original with calipers checking the size, took a measurement on the ST-7's rail cover for placement and clearence in the underside where the spring clamp rest. I drilled out the hole using smaller sizes to start and stepping up as I went along. I used a clear sealant, actually "Shoe Goo" and a cutoff a cotton ear swab to dab the sealant around the bubble level.

The 3-D reproduction feet came from you then and I finally installed them on one of the tables I worked on. I bought the feet 2-years ago and had them in waiting for use. The ST-5 Transport Upper Rail and Lower Drive Cylinder I also bought from you too. The swap upgrade was super easy, and did not need hardly any tweeking adjustment wise to get the ST-7 working correctly. The 3D feet once installed in place on the ST-7 tables original rubber mounts, I used the Shoe Goo to hold the rubber mount top side in the ST-7 in place so as not to spin. The only way I discovered to install your feet was to gently pry out/off the original feet and remove the silver plastic feet, and then gently work the 3D foot on the rubber donut, and then do the same when working the rubber donut back into the ST-7's base. I was surprised the rubber held up, none tore apart.

As for polishing the dust cover(s) I have worked on at least four or more? Depending on how deep the scratches are, if you can feel it with your finger nail then you are going to need to do some sanding first. And if sanding then you are Wet Sanding with Black Emory Sand Paper the grades go from low number (course) to high (fine). The lids condition will kind of require some trial and error to see how aggresive you go with the wetsanding. On some lids I have had to start with 400, then move up to 600 or 800 and work with till the scratch's start to disappear. Eventually you are using very fine 1000, 1500 and higher up to 2000 if you can then once satisfied with the condition you can then begin using automotive headlight polishing products and paint compounds the red to the white for clear coat finish. Once at the final stage I've used the drill with the sponge and final polishing to try to get optically clear results. The final steps when there, you then use a clear sealant and buff with a synthetic fiber cloth. It's time consuming but the results are soo satisfying!

I have this to do to two dustcovers, I'll post pictures soon of my efforts.

Yep, that's me. I've got a few dust covers with broken sides that I can experiment on, I'll try your method, by "from red to white" is that a common color scheme for headlight polishing products? Do you have a favorite?

 

[JHK]

I've never come accross an ST-7 original Tracking Roller that hasn't turned to goo like your third picture. It's got to be from a table that has always been in moderate tempetures I would guess? Of course we are lucky the engineers based this rubber tire on a readily available plumbing part we can buy still today!
Either the round donut #31 or the Flat Tire version that number escapes me from memeory, mine are stored together in the #31's clam shell.

If you can find the flat tire number, I'd appreciate it. I've ordered mine only based on size, numbners would make it hardware store easy. Thanks, John

 

[JHK]

JHK,

Are you "HeKickedMe" on Ebay?

I bought small bubble levels off of an Ebay seller out of China last year. First I measured the original with calipers checking the size, took a measurement on the ST-7's rail cover for placement and clearence in the underside where the spring clamp rest. I drilled out the hole using smaller sizes to start and stepping up as I went along. I used a clear sealant, actually "Shoe Goo" and a cutoff a cotton ear swab to dab the sealant around the bubble level.

The 3-D reproduction feet came from you then and I finally installed them on one of the tables I worked on. I bought the feet 2-years ago and had them in waiting for use. The ST-5 Transport Upper Rail and Lower Drive Cylinder I also bought from you too. The swap upgrade was super easy, and did not need hardly any tweeking adjustment wise to get the ST-7 working correctly. The 3D feet once installed in place on the ST-7 tables original rubber mounts, I used the Shoe Goo to hold the rubber mount top side in the ST-7 in place so as not to spin. The only way I discovered to install your feet was to gently pry out/off the original feet and remove the silver plastic feet, and then gently work the 3D foot on the rubber donut, and then do the same when working the rubber donut back into the ST-7's base. I was surprised the rubber held up, none tore apart.

As for polishing the dust cover(s) I have worked on at least four or more? Depending on how deep the scratches are, if you can feel it with your finger nail then you are going to need to do some sanding first. And if sanding then you are Wet Sanding with Black Emory Sand Paper the grades go from low number (course) to high (fine). The lids condition will kind of require some trial and error to see how aggresive you go with the wetsanding. On some lids I have had to start with 400, then move up to 600 or 800 and work with till the scratch's start to disappear. Eventually you are using very fine 1000, 1500 and higher up to 2000 if you can then once satisfied with the condition you can then begin using automotive headlight polishing products and paint compounds the red to the white for clear coat finish. Once at the final stage I've used the drill with the sponge and final polishing to try to get optically clear results. The final steps when there, you then use a clear sealant and buff with a synthetic fiber cloth. It's time consuming but the results are soo satisfying!

I have this to do to two dustcovers, I'll post pictures soon of my efforts.

Hi Rick, can you find the eBay listing for the bubble levels you bought? I bought some too, that were almost the right size, would love to get closer. Best, John

 

[rread13]

I'll look over the ones I printed, should be able to find a really good one.

Yep, that's me. I've got a few dust covers with broken sides that I can experiment on, I'll try your method, by "from red to white" is that a common color scheme for headlight polishing products? Do you have a favorite?

The products are from Turtle Wax, the products are automotive paint correction. The reddish one is "Heavy Duty" Rubbing Compound, and the whiteish one is a "Polishing Compound" . Both a readily sold at Walmart and other auto parts stores.

Car Paint Correct, Repair & Restoration | Exterior Care | Turtle Wax

Your car’s finish endures harsh conditions and starts to show wear and tear. That’s when you should start your car paint restoration to a like-new finish.

www.turtlewax.com

I have a 3M Headlight Restoration Kit that has a foam head for use in a power drill, that you can find in the stores or Amazon.

Amazon.com

 

[rread13]

Hi Rick, can you find the eBay listing for the bubble levels you bought? I bought some too, that were almost the right size, would love to get closer. Best, John

The original one I measured was 13mm in diameter and had dried up or leaked out. I bought a size slightly larger at 14.5mm, it's small enough to fit in rail arm cover, that's what counts. Like I said I drilled a hole in the arm cover at 31mm from the left side of the cover to the center drill location. I made mine slightly farther over than the factory because I wanted to make sure I had clearance from the internal rails spring clip when it rotates not to hit the bubble level underside. I looks fine where I chose to install mine.

 

[rread13]

If you can find the flat tire number, I'd appreciate it. I've ordered mine only based on size, numbners would make it hardware store easy. Thanks, John

I purchased the "Flat Tire" Washers from The O-Ring Store LLC the part # SN70204 has a description of AS568-204 SN70 (NBR) Buna-N70 Duro Square O-Ring. Then sold in QTY. 12. I remember paying 3 or 4 times more for shipping over the cost of the goods. Now they have a $10 minimum order system in place, and even ordering 50 pieces places the order at $7.00 plus shipping.

Here are some details of the part size:
Model: SN70204
Dimensions: 3/8"ID X 5/8"OD X 1/8"CS
0.359"ID X 0.627"OD X 0.134"CS
9.12mm ID X 15.92mm OD X 3.4mm CS

The Shopping Cart : The O-Ring Store LLC, We make getting O-Rings easy!

The O-Ring Store LLC : The Shopping Cart - O-Ring Cord for Custom Seal Fabrication OSK™ Assorted O-Ring Service Kits OSK™ O-Ring Repair Kits OSK™ Hydraulic Cylinder Seal Kits OSK™ Air Nailer O-Ring Kits OSK™ Sanitary & Brewery Gaskets O-Ring Lubrication Products Olypsys® O-Ring Measurement...

www.theoringstore.com

Maybe you can find them by the size at a Lowes or Home Depot or maybe even a local plumbing supply? I have six washer left out of the dozen I ordered, and I think I used two my own tables, I must have given some to others over the years. Try on your end and if successful let me know, otherwise I can send you a couple?