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HK ST-7 new belt. Too tight?

sloober

sloober

Super Member
I ordered a new belt for my ST-7 from turntable basics along with some silicone damping fluid. The old belt works, but I thought a new one might be in order. The old one is a yellowish clear, the new is black rubber. The new one is about an inch shorter. The old belt is slightly larger than the portion of the platter that it goes around, and would fall off if you looped it on and turned it over. The new one fits tighter and will not fall off.
There is more tension on the belt which made getting it on a bit tougher. A first test showed the belt rode off the motor pulley, and was over the flange at the bottom of the pulley. I think I can adjust the motor mounts to get it to ride on the pulley in the middle. But I am scared it may be too tight and could wear the bearing. Is my old one just stretched or is the new one too tight? Since I can't get parts for this thing, I surely don't want to mess it up.
John
 
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For more info. The new belt measures 11 inches folded in half. The old one is more like 11 3/4 folded in half.
 
sloober said:
For more info. The new belt measures 11 inches folded in half. The old one is more like 11 3/4 folded in half.
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John, I have a NOS original belt at home unused. I will measure it and report back. Be careful as the new belt may be a bit tight on there right now and is entirely different material. I would not move that motor to accomodate it.
 
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Thanks for checking your belt. I was not going to move the motor, but there are 2 nylon screws that adjust the angle of the motor slightly. I had to adjust it before to get the belt to ride the motor pulley straight. I think because of the new belt, it is pulling it off of vertical.
John
 
I run a ST-7 and have spent lot's of time under the hood of this thing. Strange about the black belt material as the one's I've got look a clearish silicone rubber. I certainly wouldn't modify the unit for the belt, but maybe try to find a different one. As I recall, the platter underside has a prong to hook the belt when you put things back together. More often than not, it want's to ride the motor pully highside rim. Sometimes it takes a few shot's.
 
I have contacted TTbasics but no response yet. I can surely swap it with a larger one. I am not going to modify anything, just adjust the motor. Just the nylon screws.
But I think the best solution is a larger belt.
There is no prong under my platter, or a hole to make it easy to loop on. You sort of have to loop the belt on the platter, hold the belt with your finger to get it on the motor, then carefully put the platter over the spindle. It is tricky, but I have gotten pretty good at it. John
 
sloober said:
I have contacted TTbasics but no response yet. I can surely swap it with a larger one. I am not going to modify anything, just adjust the motor. Just the nylon screws.
But I think the best solution is a larger belt.
There is no prong under my platter, or a hole to make it easy to loop on. You sort of have to loop the belt on the platter, hold the belt with your finger to get it on the motor, then carefully put the platter over the spindle. It is tricky, but I have gotten pretty good at it. John
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John,
I measured my new belt and it is 11 and 5/16 inches long. Just under 11 3/8 inches. Definitely not 11 1/2. I folded it in half and did not stretch in any way.

You are right on the installation, its tricky but thats how I do it. A tight belt will ride off the outer crown of the pulley I am sure of it. Don't screw around with the motor mounting. I would use the old belt as their is nothing wrong correct? Just make sure the shiny side is facing out and the dull side rides the pulley.
Ron
 
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Had a quick look and my platters got the pin. Nothing really much, as it doesn't work very good anyway. The tech manual shows messing with the nylon motor mounting screws could affect rumble performance. Probably best leaving things alone, as this is one of the ST-7's finest attributes.
 
Thanks Ron. It is great to know others that have this TT and not to be alone in the world. I am going to use the original I have as it does work well. I will have TTbasics send me a larger one. John
 
Waaaay cool, Sloober. I just picked up one of these today myself. It is in passable shape but looks like it will need a rebuild of the tonearm carriage's rubber parts including the 2 drive belts. It wouldn't power up but the fuse is blown.

On your original question about belt size, the research I've done so far is that this is a 22.4 inch belt. That tends to agree with Old Tech's measurements.

This one came to me with an Ortofon M15E Super mounted to the arm wand but the needle is busted.

Should be a fun project....

Cheers,

David
 
sloober said:
Thanks Ron. It is great to know others that have this TT and not to be alone in the world. I am going to use the original I have as it does work well. I will have TTbasics send me a larger one. John
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John, You're welcome first... but why are you replacing the belt? Just for GP?
I am running the original and it is fine I know others will say replace it but its fine. I need to deoxit my speed controls though.

Trust me this table is a bit complex but nothing a good careful techy cannot handle.

I love mine too so I understand just don't break your head over it. When they work they work great and when they need TLC then we have to abide, thats all. I know thats not much help but I think you will see that you can fix the table easily. These were well engineered.
Ron
 
David- You just got a ST-7? Yehaaa! welcome to the club! I got mine a few months ago and it is the best TT I have ever owned. A little finiky sometimes? Yes, but worth it.
The new belt I got is labeled 22.4 on the bag. Did not know that was inches, but duh. Mine is closer to 22, but I still think it is too tight for this table. Oh well.
You will love the table. I am looking for another to build on a slab of slate or marble.
Could be interesting. John
 
Ron- Why? Good question. I ordered a new one just because. I was ordering some of that silicone goo for another table to fix the cuing lever. Saw they had belts so I added it to the order. The table has no problems as I have rebuilt the entire thing. New caps on the motor and circuit board, new RCA jacks, cleaned and lubed, added sound damping stuff to the chassis, new feet, veneered the top. I just thought a new belt was in order.
I will continue with the old belt for now. I just thought that if it ever broke, it would be good to have a spare. John
 
Sloober, do you have the cartridge alignment tool? Sure hope so.....I'd like to get some measurments off of it.

Your 'table sounds nice. I can see why it might need some damping on the inside cover. Tonight, I've managed to confirm that mine does, indeed, operate but the belts are shot. The return sequence slows to a crawl then sluggishly stops. Found a broken ground wire inside, too, and some bulbs are out. Also, the speed strobe attachment underneath is falling off. Still, something cool to dink around with.

Now, if I could just find a stylus for the Ortofon M15E Super......

Cheers,

David
 
If sloober dosn't have the alignment tool, I've got one. Thinkin' you're needing to barrow one of these, as it's a rather complex jig. The indicator lamps are integral to the speed contol circuit and you'll need to replace these. They're quite an oddball part number and not easy to find. You can probably duplicate the votage/current with an LED/resistor combo. Been considering this one, myself.
 
Thanks, Renzor, I really appreciate the willingness to share.

Sloober is in the same area so it would be nice not to have to risk shipping it. I figure I'd get the measurments off of the original and make up something that would be approximate for overhand and cart height. The rest I could jig up for myself - yet another small hobby project. I'll PM you if there's a need.

Also, on the lamps, here's what I've found so far:

- Speed and Stop lamps: GE GE1302 These appear to have been covered in some sort of colored sleeve that was headshrinked to the glass. I'll likely work up an LED replacement using the dead lamp's metal base for support. I get to pick the colors in that case.

- End of LP lamp: GE 1847 This is the one that triggers the arm lift at end of LP.

Cheers,

David
 
sloober said:
Ron- Why? Good question. I ordered a new one just because. I was ordering some of that silicone goo for another table to fix the cuing lever. Saw they had belts so I added it to the order. The table has no problems as I have rebuilt the entire thing. New caps on the motor and circuit board, new RCA jacks, cleaned and lubed, added sound damping stuff to the chassis, new feet, veneered the top. I just thought a new belt was in order.
I will continue with the old belt for now. I just thought that if it ever broke, it would be good to have a spare. John
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Ok, I was not sure if you were down and out with your table. I understand your quest though. I cannot believe mine after all these years.
Treasure for sure! I would love to find another myself!
 
dshoaf said:
Thanks, Renzor, I really appreciate the willingness to share.

Sloober is in the same area so it would be nice not to have to risk shipping it. I figure I'd get the measurments off of the original and make up something that would be approximate for overhand and cart height. The rest I could jig up for myself - yet another small hobby project. I'll PM you if there's a need.

Also, on the lamps, here's what I've found so far:

- Speed and Stop lamps: GE GE1302 These appear to have been covered in some sort of colored sleeve that was headshrinked to the glass. I'll likely work up an LED replacement using the dead lamp's metal base for support. I get to pick the colors in that case.

- End of LP lamp: GE 1847 This is the one that triggers the arm lift at end of LP.

Cheers,

David
Click to expand...

Not sure where you guys are using an alignment tool for the ST-7 as there is no overhang adjustment. It is plug and play. The stylus should be perpendicular to the spindle center and within a couple mm you should be fine. Align the cartridge to be square in the shell and set the azimuth and you are done. Tilt the headshell to 11 o'clock then tighten the nut and it will turn to dead center. It may take a few tries but it is easy. I have those lamp numbers at home. The spares I bought from HK are dipped in a translucent paint of some sort. If you look at the circuit these could be easily converted to clorored LED'S!
Nice to see some people interested in this table!
 
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Yes I have the cart tool. It is used to set the proper length of the tonearm/stylus. The headshell slides in and out to adjust it. There is a screw to lock it in place.
As for the LEDs to replace the bulbs. I tried that right away and had bad results. I used some old bulb bases and soldered new LEDs in. They worked fine, but I was unable to set the speed. I tried adjusting the speed using the exterior controls, and the master adjustment on the motor. If I could get it right for 33, it was way off for 45, and visa versa. I ended up using the stock bulbs for the 45 and 33 indicators, and used a red LED for the stop indicator. It seems the speed is governed in some way by the bulbs or current through them. The bulbs are hard to find in a store, but they are available online, although clear. I think if you got a small Testors paint bottle in a candy color, you could simply dip it in a few times to make it colored.
John
 
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