• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Harman Kardon ST-7 Turntable With a Speed Issue

jandajr

jandajr

Active Member
My ST-7 turntable that I've been using for 6 plus years, suddenly jumped up to 39+ RPM while in use.
Re-capped approx. 6 years ago. I've checked all the transistors, diodes, and resistors.
Cleaned the bulb sockets and bulbs on the speed selector. The coarse speed potentiometers no effect on the RPM.

Has anyone seen this issue?
 
Register to hide this ad
jandajr said:
My ST-7 turntable that I've been using for 6 plus years, suddenly jumped up to 39+ RPM while in use.
Re-capped approx. 6 years ago. I've checked all the transistors, diodes, and resistors.
Cleaned the bulb sockets and bulbs on the speed selector. The coarse speed potentiometers no effect on the RPM.

Has anyone seen this issue?
Click to expand...
Do you have some spare bulbs? If not try swapping bulbs from 45 to 33 and test. You say the "Course Speed" potentiometer when turned is making no speed adjustment at all, that's banana's! Use some cleaner on this and turn back and forth twenty-five times or more, this part is key to speeds being stable. Somewhere I used to have the specs for this part but I can't seem to find it. Maybe someone else know and will respond soon, it's available through parts companies.
 
rread13 said:
Do you have some spare bulbs? If not try swapping bulbs from 45 to 33 and test. You say the "Course Speed" potentiometer when turned is making no speed adjustment at all, that's banana's! Use some cleaner on this and turn back and forth twenty-five times or more, this part is key to speeds being stable. Somewhere I used to have the specs for this part but I can't seem to find it. Maybe someone else know and will respond soon, it's available through parts companies.
Click to expand...
I cleaned it, and tested it out of the circuit. It reads fine.
 
Sorry, I personally have never had the issue you are currently experiencing with the table running fast and not being able to fix with making a "course speed" adjustment to the Papst 38.09 motor. I did make a huge expensive mistake to one of my ST-7 tables motor by trying to reflow some solder joint on the motor, and this caused the speed issue for me. I bought a recapping kit from an Ebay seller for the table, and even some other parts for the motor. Nothing I did brought that motor back to normal speeds. I had to buy a replacement motor from another member here that does some Ebay selling (HeKickedMe aka John).

Read the attachment, start with the basics in trouble shooting per the HK service manual. I hope something helps and your motor starts working correctly.
 

Attachments

I've ordered the four bulbs and a new belt.
I will post my results as soon as I receive the parts.

I thank everyone for your comments/suggestions.
 
You must log in or register to reply here.
Back
Top Bottom