One of the decks I worked on recently is a very cool old JVC QL-F4 direct-drive, fully automatic turntable.
The JVC QL-F4 is a mid-range deck from the once great JVC. Even in the late 70’s and early 80’s, JVC were not really known for their hifi separates. This is a shame because this series of JVC turntables had great specs. This deck is quite unique in that the platter is unusually styled, the strobe illuminator is LED-based, the motor is sealed for life and the deck allows repeat plays of sides.
The deck came to me with a couple of issues. The bottom case was badly cracked. It appeared to have been dropped at some point in the past. Also, the platter would often not spin up on its own, requiring a little nudge to get her going! Naturally the owner wanted these elements repaired and for the deck to be serviced and brought back into correct factory alignment and spec. He also wanted me to replace a headshell and cartridge that he supplied.
To begin, I cleaned the deck, to help me detect any other issues. I then removed the plastic base panel and repaired it with cyanoacrylate glue specially designed for plastics. This was a very successful repair.
Next job was to inspect the electronics. I figured that there might have been a power supply issue and it’s best to start with the cardinal rule of electronics repair: “thou shalt check voltages.” The main 22V rail was down slightly, so I adjusted this and retested the deck. She still wasn’t quite behaving herself.
What I did find though was a voltage regulator or series-pass transistor (my apologies, I can’t recall now which it was) that had at least one dry joint and needed re-working. The images below show this before and after some time with the Hakko soldering station.
Next, I had a very close look at the capacitors in the power supply supply area. There was lots of the dreaded corrosive glue around the larger capacitors, so this, and the caps, had to go. I pulled the caps and carefully scraped away the corrosive glue. I then installed some nice high-temp, low-ESR replacement capacitors. Retesting the deck showed that I had resolved the issue with poor starting torque as she now spun up every time, without assistance. I readjusted the 22V rail again and that job was complete.
I pulled the motor to attempt to lubricate the spindle bearing. Interestingly this motor is sealed for life – there is no way to separate the rotor from the main assembly, not without drilling rivets out. I wasn’t about to do this, especially as the rotor turned smoothly and with no perceptible bearing free play.
So the last couple of steps in this full service involved lubricating various points on the arm-control mechanism, setting up the deck so as to allow adjustment of the Quartz lock circuit and carefully checking and re-checking these adjustments to ensure they are perfect and stable over a decent operating period. The service manual outlines the procedure quite clearly.
After that the newly repaired bottom went back on, I installed the supplied Stanton cartridge in the supplied JVC headshell, installed that into the tonearm and then carefully aligned the cartridge and set tracking force.
The deck now plays a record very well. It is fairly quiet, wow and flutter is very low which is excellent and all automatic arm functions work well, for now – note that the drive gear attached to the spindle is cracked and it is only a matter of time before the arm return ceases to work, but this is no big deal, the deck itself will continue to play records for many years to come!