I've got a new to me KD-A5, and the deck works great, except the speed is high around 3060hz vs 3000hz test tape. The speed adjust on this deck, similar to KD-A33, KD-A6, is on the motor itself (see photo)... I don't seem to have a straight path to put a screwdriver onto the screw and would appreciate advice on how to do this. I even tried loosening a small board behind the motor and still couldn't get a straight shot. I can't "feel" the adj screw! It seems to be a solid deck, very stable with good W/F (.065% RMS), good recordings, so don't want to tear down just yet. Is there a special screw driver or approach on this deck? I've watched a YouTube on A33, and the inside electronics layout appears easier to access the adjustment screw... I attached the A33 screenshot of the motor adjustment, as well as the "clutter" inside the A5 for comparison... Experience and input appreciated mike in SC
I think it may be possible to use the correct right angle screw driver for access to the motor adjustment screw: Nando.
a plastic one would be better not to accidentally short-circuit the control given by the internal trimmer on the motor mass Kd-A33 Kd-A55 kd-A7
A7 and A8 have speed adjustment on the motor board... A33 & A55 are like the A5, adjustment inside the motor. I am hoping someone has done this adjustment and can describe how big the screw is, how far inside the motor, etc... Yes I agree, plastic or other non conductive screwdriver is the best option. I think the angle screwdrivers shown wouldn't fit the screw, but I am not sure how large the screw head is.
You could try to cut part of the plastic handle on this https://www.amazon.com/Small-Flathead-Screwdriver-Smartphones-Tablets/dp/B00BY8GAOW type of screwdriver and "isolate" the metal part with a layer of thin duct tape up to the tip.
I really like that one!! long screwdriver end! But shows not available now from Amazon... I have this one coming, which has a shorter screwdriver end but intend to cut like you recommend... https://www.amazon.com/dp/B07FDB3DLZ?ref=ppx_yo2ov_dt_b_product_details&th=1 I've avoided any metal screwdriver, but need some length, trying to get a good pic/understanding of where exactly the adjustment screw head is inside the motor... if i have to resort to metal screwdriver I'll put shrink wrap on the shaft for safety... trick has been finding something short, non conductive... i also tried these but screw tip way too large: https://www.amazon.com/dp/B006C4BXLS?psc=1&ref=ppx_yo2ov_dt_b_product_details
Removed the bottom cover of the JVC deck (as well as top) to try to access motor speed adjustment hole, but no better angle. Not familiar with this motor, but wonder if best way to access the speed screw is to remove the rear plate of the motor? I removed a small board mounted behind the motor to try to get a better angle on the access hole, worked somewhat, not great. I tried to "find" the speed screw through the rubber "protector" on the motor, but no luck. This speed adjustment (accessing the internal potentiometer) seems way too difficult for this deck. Frustrated its off so much.
For setting speed as well as measuring W/F, I play a calibration 3000hz tape (from either FixYourAudio or a NAK calibrated tape from ebay) plus i use ANT audio "WFGUI program by Alex Freed", which gives Frequency as well as W/F: "ww dot ant-audio.co.uk/index.php?cat=post&qry=library" top item on the page input to my laptop is from my best headphones into the laptop mic (I don't have audio input on this laptop...) So the tape transport needs to be working to play the tape. I've never removed a transport and played a tape... does that work? Not sure of cable reach... have to see how easy this transport is to remove.
It's possible, if the cables are long enough. I used a piece of (thick) cardboard on the top of the tape deck and the transport put on this cardboard, close to the cable connectors. On a different tape deck ...
JVC KD-A5 speed adjustment for on-motor speed potentiometer: DANGER: safe method is to adjust power off then re-energize to test. Working inside a deck with the power on is inherently dangerous. Risk of shock. It appears KD-A5 and below (e.g. A3) use a potentiometer on the back of the motor to adjust the speed. You’ve got to use a large enough non-conductive screwdriver to fit the pot: below 2mm will slide through and not turn the pot.. I modified a plastic tool from Amazon. I actually bought a similar Matsushita motor to dis-assemble to figure out the size of tool needed and how to hit the pot accurately. Any adjustment tool should be made of non-conductive material like plastic or nylon. If you look at the potentiometer, I found a 2mm wide by about 1mm thick fits the slot, and no longer than 5”. my tool is plastic. To get an adjustment tool into the back of the motor, I removed 2 screws and lifted a small board. To make sure the board stays electrically grounded, I made and attached a small jumper with alligator clips on each end, and connected the metal base of the board to the metal framework of the deck. I positioned the adjustment tool into the motor potentiometer while the deck was powered off. DANGER: safe method is to adjust power off then re-energize to test. Working inside a deck with the power on is inherently dangerous. Risk of shock. I wore rubber non-conductive gloves. I also used a voltmeter to carefully confirm there was no voltage on the components near the adjustment tool before I started adjustments. Items needed to adjust speed: 1) a 3000hz calibration tape 2) a computer with speed measurement software, (such as WFGUI software by Alex Freed available from ANT-audio in UK), 3) some type of input for the computer microphone, I used my headphones as an input 4) the tool to adjust motor speed potentiometer. Testing the adjustment pot, I had plenty of adjustment available: I was able to adjust from a fast 3055hz right down to a steady 2999-3004hz.
Update: the next time I checked the speed (after 24hr) it measured much slower, ~2960 vs 3000 The Problem: I had adjusted one time, not cycling through power on/off, and need to let it run longer. This time I adjusted back, but let the deck play longer, plus I stopped/started/powered down, waited, then restarted a couple times. After taking measurements using this approach, I got better results: from 2999 - 3005 when stable. I do notice when this motor first starts, the speed will drift down slightly after each restart. Probably that 40yr old lubricant has to warm up!
I love JVC Decks, I've got a KD-A33 that has been bulletproof through the years, for some reason they fly under the radar but they sold millions of them, back in the early 80's they were highly respected. I wonder if a little eyeglass screwdriver would fit into the notch or be too small.
What I saw and measured, whatever adj tool you use needs to be about 2mm wide on the blade width.. i tried a small blue ceramic screwdriver about 1.3mm tip, and it just fell through the pot and spun without contacting! 2mm seems to catch adjustment just fine. It appears the A7 and A8 have speed adjustment on a card, but the KD-V6 also uses the speed adjustment screw on the back of the motor. This KD-A5 is built like a tank, very heavy solid build, all steel and very little plastic at all! very quality feel, 1979. It's a 2head and plays back well, just not as "musical" recordings as JVC KD-V6 for sure! A5 has analog meters, but it has one LED to see rapid peaks. V6 sounds super all around! the 3 heads are mounted in a very solid casting, digital VU meters... I had not owned a JVC deck before the A5 & V6, but I'm sold on them with the experience I've had with these 2 decks! Mechanisms seem easy to work on, single capstan, belts easy to get to, and both decks don't show visible wear on their SA heads!! As time goes on, cassette technology, especially from this "golden era" of great decks, get more difficult to find... I feel fortunate to have found them!
I've been pushing JVC decks for years, I've always thought they were nicely made and full of stuff unlike Marantz and Sansui Decks that seem to have a lot of air inside of them. There was a time 20 years ago where JVCs were everywhere for sale but I haven't seen a nice one locally in a while. The last deck I bought is a TEAC, then an 80's Marantz (a nicer one), then another TEAC, maybe it's TEAC time?
...kinda like "TEA time..." Ha got that... How are the guts of those? The A5 has a solid cadmium plated steel frame (several JVC decks must share same frame: A3, A7, maybe A8?) and boards mounted to nice standoffs, and every corner of every board is completely supported! Nothing "hanging free" in the air! And when the solenoids shift with that all steel tape mechanism, you feel and hear it! really heavy quality build. The V6 is definitely a different design philosophy: most solid thing is the casting holding the 3 discrete heads, but the main board isn't fully supported! kind of hangs free on one side! and the tape mechanism appears to be mounted up against all plastic sub frame behind the faceplate! Doesn't affect operation, I was surprised at how good that deck sounds... keep an eye out for one... W/F is high, but I don't "hear" the impact of that... I had to clean up and overhaul the A5 door mechanism brake to get it working right, think it would be worth sharing?
