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JVC QL-F4 SPEED PROBLEM

ghamilton

ghamilton

Super Member
Ok guys, I have a JVC QL-F4 Quartz lock turntable that has a consistent speed problem. I can play records but the music sounds like the players are drunk!!
I put oil in the shaft motor bearing because I thought it was dry causing this. No luck.
Any suggestions?
Thank guys
 
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There are 2 diodes that mouser or digikey don't have.
1s2473
And
Rd5,6EC
These go on the pwr supply board right beside the two big electrolytics.
What can I use because the old ones look bad because of the glue damage.
Thanks guys
 
1N4148 will work but I doubt that is the problem. If the speed is varying, clean the speed selector switch and internal speed adjustment trim pots before doing anything else.
If that doesn't work, place a finger against the platter, creating a gentle drag, and see if there is a point in rotation where the motor doesn't turn. If so, there is a bad winding, or drive transistor (or bad solder joint on a transistor) or a bad hall effect sensor.
 
The two bigger electrolytics have that glue that has bled onto those diodes. They look bad and need replacing. The electrolytics will be replaced and glue removed.
I will also do what you suggested.
Thanks
 
I had a speed problem with a QL-A2 but only in a hot, humid, environment. I could find no bad components. What I did find is that the board had a wax, like bees wax, poured on the main controller IC. I completely removed the wax and cleaned off the residue, problem solved. My suspicion is that the wax was soaking up moisture and becoming conductive. This was disrupting the tiny signals that flow through that speed control chip. I can't prove this, but it worked
 
I have a QL A5 with varying speed or audible wavering (like drunken wobbling music - slight. the speed seems to lock in at 45 and 33, but there is something pitch and wavering (just off a little).. What am I looking at doing here and how. Russ T.
 
RussT said:
I have a QL A5 with varying speed or audible wavering (like drunken wobbling music - slight. the speed seems to lock in at 45 and 33, but there is something pitch and wavering (just off a little).. What am I looking at doing here and how. Russ T.
Click to expand...
Start by turning the platter by hand with the power off and listen for scraping sounds. Make sure it spins freely and coasts to a stop. Clean the controls.
 
Thank you! I checked with an RPM Calculator on my Android Phone and speed seemed right and pitch control workedand Quartz Lock seemed to work, but a third party hears warbling. I will clean the potentiometers and controls and re test.
 
dr*audio said:
Do you have an oscilloscope?
Click to expand...
I do not have an Oscilloscope. However, the third party states they hear a scraping or rubbing sound from the spindle area, thus affecting the audio. I was going to do a side by side comparison with my JCC QL 5 and record a waveform contrast/compare of the same recording to Audacity. I can "see" a lot that way. However, what to do about the scraping is the question.
 
RussT said:
I do not have an Oscilloscope. However, the third party states they hear a scraping or rubbing sound from the spindle area, thus affecting the audio. I was going to do a side by side comparison with my JCC QL 5 and record a waveform contrast/compare of the same recording to Audacity. I can "see" a lot that way. However, what to do about the scraping is the question.
Click to expand...
JVC QL 5
 
Sounds like the problem I had. Mine is fixed.
You probably need to replace all the electrolytics on the board. If there is glue take q tip and alcohol to it. Look for damaged parts due to the glue.
 
dr*audio said:
Start by turning the platter by hand with the power off and listen for scraping sounds. Make sure it spins freely and coasts to a stop. Clean the controls.
Click to expand...
As I said before. Try removing the platter and turn the spindle and listen.
 
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