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JVC QL-F4 DD Turntable Repair and Service

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.

Plan view of the layout of the deck internals.
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.
Here we see the power supply and motor control electronics. Note the five larger electrolytic capacitors and DC voltage potentiometer, just below the motor.
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.
Note the leg on the right has some very marginal soldering where it passes through the board. Joints like this definitely need to be re-worked.
 

Here are the same joints after re-soldering. Note the nice smooth beads of solder around each component leg.
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.

The two large capacitors have just been removed in preparation for cleaning the board. These caps are 220uF @ 50V.
I have just removed the corrosive glue from the board. The other three capacitors nearby are next.
Close-up of board where glue has been removed. I have just cleaned the area with isopropanol.
These are the two 220uF @ 50V capacitors that smooth the 22V rail. I replaced them with the same value, but in a modern high-temp, low ESR capacitor.
Another angle…
Replacement 220uF capacitors installed.
The others have also been replaced in this shot

Reverse angle of all five replacement power supply capacitors.
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.

Here is the motor, it’s really a nice design, sealed for life which is a slight bummer, but the bearing checked out very well, so no issues here.

And the underside…
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.

There are several pivot points and spindles here that should be lubricated with a very light oil, for good measure.
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!

The cracked drive gear is a bummer but will probably stay like this for many more years before finally failing. There is not much that can be done about this unfortunately.

17 thoughts on “JVC QL-F4 DD Turntable Repair and Service”

  1. Hi Dave, no quick fix unfortunately, but an experienced eye needed and some TLC I think. Are you able to get your deck in for service?

  2. HI Mike, My ql-f4 turn table quartz lock still wanders around after lubercating is there quick fix,it throws the music sic.regards dave.

  3. Hi Rick, thanks for that. I don’t have a list available but suggest you make one by opening her up and having a look, or alternatively by locating a service manual. The manual should have a list of parts, including caps. Cheers, Mike

  4. Hi, nice article! I restored my JVC QL7 a few years ago by replacing the caps. I was wondering if you could direct me to a list of the caps in this QL–F4. It looks like there may not be as many to replace, but a list would really help.
    Thanks!
    Rick

  5. Hello. Great article with meaningful pics and explanation! I have this turntable. cleaned the speed selector switch as per you instruction and no more flutter at 35! I too have noticed the large caps that have that weird dark substance that appears to have “leaked out” is that what is called a “leaky cap”? what symptom should i expect if that condition is left? So far the table has been working great for years. not sure what caused that to happen. Thanks again!

  6. Greetings Michael! Thanks for your question – to be honest, without the deck in front of me, it’s hard to offer tips that might be helpful. My main tips are always to make sure you have good tools and the skills to undertake such work. If those bases are covered, you will find the work fairly straightforward I think. Take your time, use the opportunity to assess any other work that might be required, lubricate the motor and so on. Let me know how you go or if you get stuck!

  7. Greetings Mike. Thanks for posting this. I have the same model that is my main livingroom unit. The start / auto switch slips on its shaft and I am planning to tear into there and repair it. After a quick survey of the situation, it looks like I have to completely disassemble this thing to get to that switch. Any pointers on that? Any shortcuts? Thanks for your feedback. It’s a great TT.

  8. Hi Darcy, so the drive gear is easy to repair, just clean with a fast drying solvent that won’t harm nylon and glue with cyanoacrylate (super-glue) adhesive. Try to clamp the gear gently though, to ensure the drive ratio doesn’t change from it not being snug on the shaft. Capacitors and other electronic parts are soldered in and need to be carefully desoldered with a desoldering tool or braid and good technique. They can then be replaced with a quality part that should last many years.

  9. Hey Mike I just bought this deck, it was one owner, original box, etc, very nice shape. I have the cracked gear too, I was thinking maybe I can glue it. The crack or split is just starting on the gear. I don’t know anything about electronics…forgive me….are the capacitors soldered in or are they plug in. You just made it sound so simple. Thanks Darcy

  10. Hi James, thanks for sharing this story and the great result you achieved with this deck! Cheers, Mike.

  11. Great post and photos that proved very helpful for me.

    I recently found an old JVC QL-F4 turntable in a pile of junk turntables in someone’s garage. My neighbor offered it to me for $25 with a couple vintage LPs to boot, so the deal was done. Aside from the dirt and crud of many years of neglect it didn’t look bad except for the usual scratches in the dust cover. I polished out the haze and scratches with some automotive plastic polish. The electronics and mechanical operation were both good. Just to head of future problems, I replaced all the power supply electrolytic capacitors with upgraded low ESR types that had higher voltage and max temp ratings. In the process of replacing the capacitors and cleaning the corrosive glue off the circuit board, I managed to break the D 809 5.6 volt zener diode that I also replaced. The owner’s manual came with the turntable and was very helpful. I managed to re-calibrate the quartz-lock without the usual oscilloscope. A new elliptical stylus was installed in the Stanton 500 cartridge for $14. The total cash out of pocket was less than $20 for the repair parts. With a little cleaning, lube, and the modest sum of $45 I have a great sounding turntable. This vintage TT has better specs than many new production models. I may be adding an additional headshell and the Audio Technica MLA 440 cartridge, or possibly the Ortofon M2 Blue in the near future.

  12. Thank you very much, most decks are repairs for people, but occasionally a deck comes up for sale. Regards, Mike.

  13. Beautiful article. Just had my QL-F4 apart to fix its inability to maintain speed. This one has not been dropped. I cleaned the 33/45 speed switch with alcohol and air-gunned it dry. I rotated and returned to original the two pots that seem associated with speed. I saw the corrosive material under the caps that you have detailed and it is eating resistor legs. Did nothing for that. Now it maintains speed without wow and flutter but the QL leds are flashing like crazy monkeys. Fun. Thanks for your article.

Thanks for reading, leave a comment and let me know what you think!