Electronic wizards ? A question

[wawajake]

My project is repair of a Yamaha L-A55 Stereo Turntable. Although not mechanical project for a tractor site, I respect the skills on this site. Last year turntable stopped turning. I took it apart and found an internal buss fuse (125 volt .5 amp) burnt out . I was only able to find a 240 volt .5 amp fuse in city. So bought two ( one for spare) and installed and turntable worked until today. I took apart and installed spare fuse now....and it works again , but I am wondering if fuse blows easy because it is a 240 volt half amp fuse , instead of a 125 volt half amp fuse. So if there is a electronic wizard on this web site , please enlighten me.

 

[Roadworthy]

The voltage rating on the fuse is the maximum voltage to which it should be subjected to guarantee it will blow. It would work just as well in your car or tractor if the amperage was correct. I'd be more concerned about the reason for your excess current draw. You could have a leaky capacitor in the power supply. Also, look at the original fuse. Did it just have one thin wire in it or did it appear to be kind of a coil or element of some sort inside. If that were the case you could have replaced a slow blow fuse with a fast blow. It depends on where it is in the circuit but if it's on the motor that could be a cause of your blown fuses, too. A motor draws a high current on start up and the slow blow fuse gives it time to get past the start up without blowing.

 

[wawajake]

The voltage rating on the fuse is the maximum voltage to which it should be subjected to guarantee it will blow. It would work just as well in your car or tractor if the amperage was correct. I'd be more concerned about the reason for your excess current draw. You could have a leaky capacitor in the power supply. Also, look at the original fuse. Did it just have one thin wire in it or did it appear to be kind of a coil or element of some sort inside. If that were the case you could have replaced a slow blow fuse with a fast blow. It depends on where it is in the circuit but if it's on the motor that could be a cause of your blown fuses, too. A motor draws a high current on start up and the slow blow fuse gives it time to get past the start up without blowing.

I no longer have the original fuse, but the fuse holder on the circuit board states 125v .5 amp. I suspect the blowing of fuse is caused by wife using the cleaning brush while direct drive motor is turning the record instead of turning record manually with motor off to use clean brush. So if your telling me fuse voltage and amperage is not effected by 250 volt versus 125 volt. Then only remaining factors are if slow blow needed.....and of course stop incorrect cleaning of records with motor running. Does that make sense ?

 

[Industrial Toys]

Good question about the slow blow. Many motors use a slow blow for starting, so maybe not a bad idea. BUT, slow may mean microseconds as opposed to almost intantaneous. So restricting the turntable for any length of time will probably blow it anyway. How about putting one of those old in-line lamp type switches on the power cord? Easy-Peasy!

Yes higher voltage fuses are made so they can't blow and then arc across the gap.

 

[robstaples]

I went looking for an image of your turntable and the only L-A55 was by JVC. My search was to identify if it was a DC direct drive model( did you see a belt drive under the hood? yes? then not a direct drive.) If it is a direct drive, the slow blow is not really applicable as the Capacitors provide the in-rush current. As previous stated it might be a component problem if it continues after clean procedure is modified. how old a unit?

 

[wawajake]

My bad ...it is a JVC ...the tuner is Yamaha. Hey I'm old get mixed up easier these days. Yes is direct drive, says JVC direct drive right on it. So far working fine with the 250 volt half amp fuse . So thanks everyone.

 

[grsthegreat]

Whats a turn table



Just joking. My advice...buy a bunch of fuses off of amazon and store them. The different rating means nothing for the fuse. Most modern fuses are rated either 250 volts or 600 volts.

 

[mbohuntr]

Depending on the age of your set, your main filter caps may need replacing. (As previously mentioned) Here's why...

You have a rectifier circuit in there that changes the AC supply to DC for the circuit board. (B+ for the older tube stuff). As they age, the Caps become "Leaky" Not in the physical sense, but permit the DC current to short thru them to ground. This would cause high current and blown fuses. Your power transformer may heat up and eventually fail.

I would also be inclined to look at lubrication for the turntable.

Hope this helps
Mike

 

[Fuddy1952]

Good advice all. I'm a retired electronic technician 43 years, consumer electronics so I've repaired thousands of turntables.
Everything covered I would have said. Now brush clean record, motor off and blow-off spray is good, blowing record and gently blowing stylus.

 

[3Ts]

Cleaning a record or the turntable while it is turning puts an additional load on the motor causing it to draw more current. If to much it will blow the fuse. Do the cleaning with the power off.