More JVC HR-D470U goodness and lesson learned...

[redk9258]

In the last couple of days, I have fixed 2 more broken JVC HR-D470U VCRs. Both had similar problems. They would thread the tape and it played but at the wrong speed and no real picture. After finding a bad cap in my original HR-D470U in the servo section, I was looking at the same caps and not getting anywhere. I was trying to read the sync pulse from the control head circuit. I couldn't get it so I knew something was wrong and I was thinking the head could be bad at this point. I cleaned it several times and no pulse on the scope while connected to the test point. It did read a couple of hundred Ohms so that was promising. For some reason I decided to put my scope on the power supply. Holy crap, the ripple was horrible on the 5V supply. I pulled the power supply and found 2 caps completely open with my Blue ESR meter. I think I am starting to love this thing! One of the caps was a 3300MF @ 16V. When I unsoldered it, one leg was corroded off! I recapped the power supply and now it's back to life. The VFD display is brighter now too. It works very well with one exception. The tracking knob has no effect. I have another 470U with the same problem.

I then looked at another 470U that had a similar speed / tracking problem. I immediately went to the power supply this time. Ripple was horrible on this one too! I checked the caps with my ESR meter and the 3300MF 16V cap was open. I unsoldered it and top my surprise the leg was corroded off like the other one! I only replaced that cap at this time. I put it back together and I had lines across the picture that tracking would not take out. I put my scope on the test point to check the FM envelope. It didn't look right. I was looking at the mechanism and exit side post (P3, I think) was loose! I turned it and right away the picture and HiFi sound came back to life! I used the scope and set the adjustment as close as I could using a couple of tapes, both factory recorded and ones I recorded. I have it playing a tape that was recorded in EP on Thanksgiving Day 1989.. almost 35 years ago! I recorded the radio on the HiFi tracks and whatever was on TV (Dirty Dancing). It's tracking fine and sounds great!

What I have learned is to check the power supply first before looking into anything else! If anyone is having any trouble with their HR-D470U, you might want to check the power supply caps- especially that 3300MF @ 16V. It's a Mashusita cap, BTW.

[Blast]

I worked on a lot of VCRs in the late 80's and 90's and none since so the memory is likely far gone on this one. But, if that's a late 80's model I found there were 4 or 5 issues that, once addressed and repaired made those models SOLID!

Sounds like you've found two of them- power supply caps and loose P3. The brass piece would often fall out the bottom of both P2 and P3 and, if I was lucky, would still be laying inside to make the repair with two-part epoxy. But, I also sold a lot of those guides, as well.

Some of those models had a nylon sprocket/gear attached to the bottom of the capstan motor flywheel (that engaged the belt to the idler) that would crack and fall into the bottom of the VCR. A little epoxy and I never had a callback on it.

Fourth, there was a capacitor on the lower cylinder that would fail and present with a partial playback picture. It was always a "clean" break in the picture that would change position after the cylinder was brought to a complete stop and restarted. I kept a certain tantalum cap in stock to replace the defective one. Can't remember the value.

And finally was dirty mode state switches. I cleaned many and replaced many.

After you got past those issues those late 80's JVC's were a force to be reckoned. Glad to hear you're on top of yours!

[redk9258]

I think this is the generation before those loose guide posts that fell out. It's all metal and there is an Allen screw that locks it. The Allen screw was loose. There is nothing on the bottom of this capstan motor.

I just cracked another one open and guess what.. Same symptoms as the others.. can't figure out the speed is and no clear picture at all. Same C17 cap is cooked! I think is a design flaw because it gets too hot. It's next to a heat sink so they probably should have used a 105° C cap instead of 85°. This one is an Elna capacitor. This one is bulged but the lead is not corroded off on this one. It checks completely open. It has a date code of 8630 - 1986, 30th week. The Matsushita has a code 684A. I'm assuming the 6 is the year 1986 but not sure. I've searched and found a forum post that said last time buy was in 2000 for that series of the Matsushita capacitor. I cannot find a datasheet. I don't believe these have ever been changed. I have one more to check out but he needs belts. I bought it as-is or for parts. I had to help it from underneath to change modes because the belt is loose and slips.
I think it has similar faults.. not able to detect speed / no picture. I'm willing to bet it has the same cap failed.

[redk9258]

Update: I decided to temporarily use a 2200MF cap to see if this one would play. It plays beautifully! I will order some more 3300MF caps and put the correct one in when it arrives. I guess 2200MF is much better than 0MF!

[redk9258]

Another update.. I'm kind of embarrassed to admit it, but over the years I have managed to acquire 7 of these JVC HR-D470U VCRs. The one I bought new in 1987 and one several years ago that worked when I bought it but stopped working, I have bought 5 others cheap as-is / parts only. 1 of the as-is works perfectly fine. Anyway at this point, I have every one of these working now. 4 (!) of them have failed because of a 3300MF capacitor in the power supply! It is next to a heat sink and I guess gets cooked over the years. This causes nasty ripple on the 5V power supply and causes lots of problems. Tonight I replaced a badly slipping belt on the last one ans its running now.

3 of these still have one problem remaining. The tracking control does nothing. I don't think they are dirty pots either because I worked one of them back and forth probably 100 times. That should have got it doing something. Hopefully it won't be years until I get that figured out.

[redk9258]

Here is a picture of the 5V power supply with the bad cap on a scope..



Pretty ugly, huh?

[Blast]

That IS ugly!

[redk9258]

An update for the tracking controls. The wiper that contacts the carbon tracks when rotated is staked (plastic welded) to the plastic shaft. The little nubs broke off and the wiper comes loose inside the control. I was able to repair these using a soldering iron and carefully melting the plastic. One didn't go so well but I found a circuit board on eBay that had the same control. I bought it and swapped it out. In hindsight, I should have put a drop of superglue to hold it in place then a drop of epoxy to actually bond the part. If one comes loose again, that's what I will do.

[vortalexfan]

I have the same VCR that I had bought off a guy on facebook market place locally, and I had bought a parts unit because the front cover on the one I had bought on market place was missing the cover that went over the remote control sensor and the button for the TV/VCR Button. The issue that my VCR was having was not wanting to play the tape when it was loaded into the VCR, when I would load the tape into the VCR the auto-play would trigger and load the tape into the heads but then the tape wouldn't play, it would just back the tape out of the heads and then shut the machine down. I figured out it was because the belt for the loading mechanism (the loading mechanism for loading the tape into the heads) was bad to the point that it was slipping when it was trying to finish loading the tape mechanism and I had ordered some belts and unfortunately when I got the belts in and went to reinstall the belt I accidentally messed up the loading mechanism's timing because now I can't get the loading mechanism to load a tape properly, or even pass the start up test.

Is there anyway to fix the tape loading mechanism timing so that it will allow the machine to power on properly and load the tape correctly? I downloaded the service manual for this VCR and it wasn't very helpful with regards to adjusting the loading mechanism timing when replacing the belt for it.

Also is there a way to replace the small tape loading mechanism belt on the bottom without having to unsolder the ribbon cable that goes to the board that runs that loading mechanism? I unfortunately have had to unsolder that ribbon cable 5 times so far and each successive unsoldering and resoldering of that ribbon cable keeps messing up that ribbon cable more and more.

[redk9258]

I can't remember if I had to unsolder the ribbon cable or not. I think there is enough room to do it without unsoldering. Unsoldering is probably best. If you do unsolder it, You might as well clean the sliding mode switch. It's also soldered in. If you take your time this isn't too bad to do. If you get frustrated, walk away and come back later!

If the timing marks all line up and it won't play, it could be a dirty mode switch. That last bit of travel will test the belt. If it slips, it will not complete loading. You can put the VCR on it's side and watch the big cam gear. If it struggles at the end of the loading cycle, use a plastic pick or something to help it the rest of the way. Playback won't start unless the loading cycle is 100% complete.
You can also work the mechanism manually by turning that pully while unplugged. It takes about a million (exaggerating) turns to do a cycle.