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Harman Kardon ST-7 ... repair ... sort of ...

Sunbird80

New Member
Hello, new here ... name's Paul ... first post ... I recently picked up an HK ST-7 at my local Goodwill for $8 ... it was completely NON-working. I tore into it blindly as I have never worked on a TT before. After blankly staring at the circuit board for an hour, I tapped on the edge of it with a screwdriver and it started working ... just got lucky I guess. The motor was making a horrible grinding sound so ... after reading a couple of other posts on here, I pulled the motor out and turned the thrust bearing adjustment screw about half a turn and now it is running silently. Awesome! So, the touch controls work now and the motor is quiet. I managed to get the tracking roller out without disassembling the mechanism but, getting it back in won't be as easy. But, I think I can manage it either way. The only questions I have really are: What is a good sized O-ring to use on the tracking roller? And, if someone would look at my cartridge a confirm that it is a Sonus Blue and is there a replacement stylus for it? Or am I going to have to replace the entire cartridge?

Thanks much!!!

Photos will follow this post ...
 
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"STOP" is working ...

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33 1/3 is working ...

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45 is working ...

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Thank you for the info ... I will look into it. I got this TT really cheap and it is such a nice looking piece ... I really want to make it functional. I know that I can make it work, I just hope that I can make all the adjustments to it afterward. It seems to have several different places to make adjustments. I am not very knowledgeable about these things ... just learning as I go. Reading other posts in the forum has already helped a lot. Thanks again.

Paul
 
I have several of these, they are great!! I went to an "O" ring distributor (among other rubber products, tubing, etc.) and found a big FAT "O" ring that works great for the tracking roller. You can also go to auto parts supply stores, and they have behind the counter "O" ring assortments that you can look thru to find one suitable.

Did you know that the light under the 45 rpm touch panel needs to be good for the 33.3 speed to work, and the 33.3 touch panel light needs to work for the 45 speed to work? Its a curious fact. The light under the stop touch pad does not need to work.
 
Phototone, yes, that is a curious thing about the lights under the touch controls. I went to Lowe's and found a suitable "O" ring for the tracking roller and spent the better part of an entire day getting it put in. Not an easy job, especially for a novice ... but, I did get it done. I accidentally pulled off one of the very fine wires that runs from the tonearm but, it will only be a minor soldering job to put it back. I still have to get a cartridge for it as well. Someone suggested an Ortofon OM series so, I believe that is what I will go with.
 
Phototone, yes, that is a curious thing about the lights under the touch controls. I went to Lowe's and found a suitable "O" ring for the tracking roller and spent the better part of an entire day getting it put in. Not an easy job, especially for a novice ... but, I did get it done. I accidentally pulled off one of the very fine wires that runs from the tonearm but, it will only be a minor soldering job to put it back. I still have to get a cartridge for it as well. Someone suggested an Ortofon OM series so, I believe that is what I will go with.

The OM's are a perfect match for that arm.

How about a description of just how you wrestled that ring onto the roller. I've been afraid to even start on mine and I've rebuilt quite a few turntables.
 
The OM's are a perfect match for that arm.

How about a description of just how you wrestled that ring onto the roller. I've been afraid to even start on mine and I've rebuilt quite a few turntables.

Some of us have also done it without totally removing the roller. Do a search for that.
 
rnorton,

I ended up getting a #31 O-ring from Lowe's ... it will stretch just enough to fit over the rim of the wheel. I have reassembled the unit and the tracking is working well with this O-ring ... final adjustments are pending me getting a cartridge.

Getting the tracking roller out of the carrier is no problem ... getting it back in isn't quite as easy. After trying for hours to get it back in without disassembling the tracking mechanism, I finally conceded to doing so. All I really had to do was remove the tracking pulley. Then the center support tower ... just take it loose at the base and it will swing out of the way. After that, remove the nylon gear at the tonearm end of the tracking cylinder. The tracking cylinder will then slide out. This was the only way that I had enough room to get my fat fingers into the space where the tracking roller sits. With the tracking cylinder out, it should be relatively easy to pop the tracking wheel back into its carrier. Then as they say in the manuals ... reassembly is the reverse of removal ... LOL. I broke one very small hair-like wire loose from its solder point while doing this so, be aware of stretching wires while working.

It is a tedious job ... I am a complete novice though and I managed it. Believe me, if I can do it ... anyone can. I can't wait to get this thing fully functional. It's a really great looking peice. I am soooooo close ... gotta get that wire soldered back on ... get a cartridge ... make final adjustments ... then I should be good to go.

Paul
 
Wait'll you hear it. Good sounding table- nothing sounds quite like a well set-up linear-tracker. I'm not saying other stuff isn't as good or better, but the linear trackers can sound great.
 
Hi Sunbird80 and others following HK/Rabco ST's! I bought one and am waiting for the shipping x-country of it. I am praying to God that the table arrives intact in all respects, it too was in VG condition. I have been lurking here for the last week or so reading all the threads on these tables and gathering up the needed parts to get mine operational.

I have a Sonus cartridge Red #5 stylus that came on a Yamaha p-850 that I have since pulled the headshell/cartridge assemble off and will save it for safe keeping. I found a on line seller that still has stylus for the Sonus if you want to check them out?

http://www.turntableneedles.com/SONUS_c_50074.html

I am now using a Shure M97xE and it sounds very nice. It's actually a tad lighter than the Sonus by about a 1/4 gram. The Shure is smooth on the high end, has great bass response, and nice channel separation, oh and it's a very affordable at $74 and up.

I am anxious to get my table and start working on it. Don't forget to get the service manual and owners book for the table. I downloaded from:

http://www.vinylengine.com/turntabl...earch=search&control=any&auto=any&changer=any

Rick
 
The ST-5 and I believe the ST-8 had metal tracking rollers, no rubber, and both came out after the ST-7. I guess HK figured out early that the rubber rollers were a bad idea. I have changed an ST-7 roller and used a fuel injector o-ring from Autozone. I now own an ST-5.
 
Hi everyone!

My ST-7 arrived in VG condition yesterday, no shipping damage at all. My dust cover is in VG condition, just needs some polishing to really make it look like new.

The the table needed a thorough tear down to clean outside and inside it completely. It really looks very impressive all cleaned up. The tear down really was not as bad as some may have stated. I am not an electronics technician, just a guy with a mechanical aptitude. It really was a lot easier than I had read it to be. I went straight for the "throat" and took the slide arm assembly apart being careful and attentive to what came from where and so on for the parts, the rails directions and so on. The wheel was the tricky area, being extra careful not to damage the part and the assembly that holds it. Gently prying ever so carefully on the side and using a pair of thin long nose needle pliers it came out with a gentle nudge. I installed a #31 O-ring from Home Depot (10 pack for $3 or so) It was a small battle to get on, but it fits and it works very well. I did have to make some minor adjustments to the arms lift and drop height from the small allen head screw. I did not have the right size allen tool, but I just took the top part off removing two philps screws and then re-installed it after making minor adjustments to get the correct height and drop, I think I got it on the third try.

I did have to make changes to the arms tracking, again trial and error while playing some albums and keeping an eye on the arm and the trailing arm, then looking again at it as it played further into the record. Eventually I got the correct settings and I have played a bunch of albums and am really impressed with the job I have done and the table!

I installed new belts and then started making the fine tuning adjustments. I did have to make an adjustment to the drive motor also. The motor after playing a record on one side started to make some scraping noises. I took the motor out and then made a 1/4 or more on the nylon stop and put it place, spun it some by hand and it was smooth, so it went back in and then I began the final re-assembly. I installed some velcro for the foam that dry rotted away for the two polished top pieces to prevent rattles.

I am waiting for my new lamps and LED'S I ordered to arrive, got notice today they shipped. I got lucky, the touch function lamps all work but the end of record stop light is out. When the new lamps arrive, I will install all fresh and try the LED's to see if they are in the same voltage and amp tolerances to work correctly, I am crossing my fingers!

I also got lucky too that the cartridge and stylus are in great shape ( AT12S and yes it has an OEM ATS12S stylus, it's been cleaned and my albums sound awesome on this table and cartridge combo.

I do have one small problem. My table again has working lamps for the touch controls but it plays 33's on the 45 rpm position. The 33 rpm speed is perfect on the 45 rpm's button, the 33 rpm speed is real slow. I wonder if any one has any thought here how to fix this? I don't own any 45's, so if there is no fix, it won't really matter, I just would like the table to work 100% like it used too.

Rick
 
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I do have one small problem. My table again has working lamps for the touch controls but it plays 33's on the 45 rpm position. The 33 rpm speed is perfect on the 45 rpm's button, the 33 rpm speed is real slow. I wonder if any one has any thought here how to fix this?
Page 20 in the service manual mentions a coarse speed adjustment procedure that you may want to try.
 
HK ST-7 Course Speed Adjustment

Page 20 in the service manual mentions a coarse speed adjustment procedure that you may want to try.

Thanks Les.

I'll give it a try when I get my shipment of lamps I plan on opening things up again to put them in and I'll perform the adjustment with the table opened up (the top aluminum cover piece off). I have seen the blue pot in the front circuit board, will check the page for sure and let all know soon.

Rick:thmbsp:
 
Thanks Les.

I'll give it a try when I get my shipment of lamps I plan on opening things up again to put them in and I'll perform the adjustment with the table opened up (the top aluminum cover piece off). I have seen the blue pot in the front circuit board, will check the page for sure and let all know soon.

Rick:thmbsp:
The coarse speed adjustment pot is located on the bottom side of the motor PCB and can be accessed from the top through a hole at the bottom left corner. But before doing that, I'd first treat the fine speed adjust pots with Deoxit.

Also, if your belt has a smooth side, make sure it's facing out. If the smooth side is facing in, it can slip resulting in slow speed.

Les.
 
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