JVC QL-F4 turntable - vintage but won't turn on

El Cavano

El Cavano

Active Member
My QL-F4 turntable won't turn on. It might have been damaged in an incident where my Kenwood receiver was up pretty loud playing a YT clip and then just stopped working.

This is a nice vintage TT. I plan to open her up a bit and look around, especially near where power comes in and near motor.

Anyone been down this road before? I really like this TT.

Thanks!
 
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Looks like I can get those caps out easy enough. What about cleaning all that gunk off the circuit board, contact cleaner?
 
I'm not sure about the cleanup, but I would consider it hazardous waste. Be sure to check the rectifier diodes and/or voltage regulator once you've replaced the caps.
 
Interesting. Have you seen glue like that on other circuit boards? It would have to be non conductive otherwise that whole area would be a short. I guess I can test the caps - when they blow they short right?
 
El Cavano said:
Interesting. Have you seen glue like that on other circuit boards? It would have to be non conductive otherwise that whole area would be a short. I guess I can test the caps - when they blow they short right?
Click to expand...

Hot glueing caps is very common. I work with electronics and we hot glue caps all the time.
 
By George I think I've got it. A blown fuse! Confirmed with volt meter. Now, where to get a fuse on a Sunday evening. Easy problem to solve.
 

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In the picture of the caps; that's something overheating. There is a component that has failed. The blown fuse is the result of the over current condition that caused the heat damage. Looks like there is a fair amount of repair work to be done. What does the other side of the board look like?
 
Other side looks clean, yet there is a wide swath of what looks like a plastic coating, almost varnish like over the component nubs.

So, it's blowing fuses quickly. I can see the fuse wire dancing before it blows.

When it was running, I noticed a periodic nocking from within the motor assembly. Also, just noticed that it is not rotating at the proper speed (strobe indicator doesn't "freeze" at speed).

This doesn't look good.

Thinking about picking up a Dual or something simple that works. I could do that easily for the amount the repairs may total up to. I think there's an $50 bench fee. I'm suspecting a bad motor now. That could certainly cause binding and fuse blowing and escalating repair costs.

Thoughts?
 
El Cavano said:
Spins freely. It on the bottom within the motor that I hear knocking.
Click to expand...

Direct drive motor does make a knocking sound when it's trying to spin up.
Are you using correct fuse? They have slow blow and fast acting type of fuses. They work differently.
 
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Replaced orig fuse with same 250V 500mA. half tempted to put a 1A fuse in there.
 
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Those caps look blown/leaky to me. Cheap and easy to replace. Other components around them, like special IC's, not so easy.
 
Which on-line retailer is good for electronics parts? These 220uF capacitors (50V) can be really cheap, like 7 cents. Should I spring for the expensive ones? :)
 
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