I've seen this strange fault twice in recent times. Once on a JVC S-VHS, also on a Panasonic NV-W1. Both times it was a bad electrolytic capacitor (high ESR) on the lower drum PCB. Neither decks were used often, but it happened "suddenly" when the decks were next used (after not being used for a few months). Took me a while to find the cause on the JVC, but when the exact same fault appeared on the Panasonic, I knew exactly what to do!

@MarcosAlmeidaNet

5 ай бұрын

I've seen It too. If i'm not mistaken is a 10uF SMD.

The noise could be to do with the alignment of the Guide(s) posts. I have had this problem on the NV-HS1000B that was mistracking because the entry guide was very stiff and needed to be replaced which then cured the fault. Panasonic AG6810/6800/6840s always needed to be regularly serviced when ready for duplication of VHS cassettes. I use to come across many of these Panasonic machine that needed new guide posts along with time when servicing them. On the NV-HS930, Capacitors in the power supply could also cause this fault and cause the machine to drift in tracking. The new alignment that you have carried out on the machine Colin could affect the Hi-Fi audio in playback and record which may cause it to mistrack. Good Troubleshooting...

Colin, my friend... You are near the root cause of the problem but not spot on. I'm telling you the real cause: These decks suffer from magnet micro cracking/seizing in the drum rotor. You will realize the magnet will "slide" inside the metal can if you make a little rotational force with your fingers. The only thing you need is drawing a line with a pen, crossing the edge of the rotor, just for reference. Then, move a bit the magnet in one direction or the other just to see the problem disappears, in a hit-and-miss fashion. Then, lock the magnet wit a couple tiny drops of glue and perform a fine adjustment with the own PCB lateral play. Last, you can perform the electrical adjustment (optional). I've repaired dozens of Pana decks with this issue in the past 10-15 years. Now, you (all) owe me a beer hehe 😊.

I even own this machine not having any problems right now...but if there any....i like to get in contact...you are great in repair....nice demonstration of finding the problem...i am very impressed

Now that I watched to whole video before commenting OMG you are a ""GENIUS"" how in the world did you figure that out by making an adjustment that most anyone would think is factory set and couldn't possibly be an error?? I enjoy your videos you are very intelligent! Don't pay any attention to those 30 year techs you are very good my friend. Simply amazing fix!!

Nice diagnosis and fix.

Many many thanks for this video. I just repaired a telefunken A960 N for a friend of mine and was blown away of the crystal clear image down to the last half line as the switching point was below the visible area. I researched the last two days how I can achive the same on my JVC HR-S9500 for digitizing some precious old recording. Now I know what to try! As I said: thank you very much! Feel free to have a look on my channel where I put some VHS-recordings AI-upsacled to HD.

Very interesting video!

Thanks Colin you carry on with your youtube channel you are helpful and explain the repairs so we understand. We don't need sum dick blowing his own trumpet for the past 30 years. Cheers

The weirdest thing is that the signal from the head that's supposed to be switched out isn't completely gone, and still breaks through. I've had a couple of VHS machines that have lost their head switching point, and the picture completely disappears below the erroneous switching point, and you just get and band of 'snow' from the head that hasn't come into contact with the tape yet.

@video99couk

5 ай бұрын

This is normal I'm told. Some early video recorders didn't bother to mute the off-tape contact heads at all.

I knew it was going to be a head switching-related problem as soon as I saw the picture shift downwards in forward search and pause. Would be insteresting to see the head switching point aligning itself to 6.5H before vertical sync on the oscilloscope whilst the machine was going through the automatic adjustment procedure.

Nice win. Almost at 12voltvids level.

No record button on the front panel? weird design there by Panasonic. every S-VHS player i have from JVC has a rec button on the front. The jog wheel on a JVC S8700ek is sublime to use!

Did you find the grub screw that holds the brass collar tightened properly? It might also be that the head drum changed its angular position because of a too loose grub screw.

@video99couk

5 ай бұрын

Yes it tightened. If it had been loose then the threaded holes in the top wouldn't have been in the vertical position as mentioned in the service manual, and the PCB would have been at a very different angle.

I'm pretty sure this was indeed what you think, a corrupted EEPROM content. You can probably rotate the stator back to its original position little by little, by doing the switching point alignment after each step. It was too far off do do it right away. I have an NV-HS850, very similar to this, but no service manual available for that model (althogh probably the service mode works mostly the same way). It has at least 3 EEPROMs in it that I can see, two on the main board, and one on the Y/C board. I want to read and save them all, before they develop dementia. This is a common thing with EEPROM / Flash memory, they can't reliably retain data after ~20 years. UV EPROMs are somewhat better, but not always, I have a JVC BR-7000 in which the UV-EPROM content got corrupted in 2009, when it was "only" 22 years old. I have also seen UV-EPROMs close to 50 years old with intact data. It is just unpredictable how long each piece of non-volatile memory chip will retain its data intact. I would suggest you to read out and save all the EEPROM contents from this machine, then erase and re-program them all with their original content, because one of them has reached the end of its data retention time. Next time it might loose a bit which will completely brick the VCR. It might be a good idea to replace that one EEPROM in which it stores the head switching point setting, because it lost its content a bit too early.

Well done Colin :-D What a strange fault. i was cross eyed just thinking about it :-D I didn't know some machines had a store for some non user settings. Sneaky engineers :-D

Usted puede con todo👍

@video99couk

5 ай бұрын

I wouldn't go that far, but I try.

Weird fault with a weird solution! I also think it could either be a sensor, or a settings memory issue. I'm wondering if the hi-fi audio playback is working properly? [Edit - just checked description!] Very interesting video.

I got the exact same error on a Panasonic NV-FJ621. It had the fault when I got it so idk if it happened when the previous owner had it or during shipping or something. Also did the same fix as you which got the switching point in order. It does however output a white comet/interference type thing at one line on the video which may or may not be related. Alternatively it may be something with the anti-static brush underneath the drum but I damaged the threads on the brass nut so can't get it off again and it's anyway not a fancy vcr so I've not bothered spending that much effort on it for now. I've got 2 Z mech SVHS decks but neither of those have developed this issue thankfully - though my NV-HS870 has another problem with dropout masking making it kinda unusable. I've also seen someone else in a forum post the same issue on a later panasonic though that was with the later R4 mech but they may still have been using similar parts for the drum motor. Will be interesting to see your analysis of the sensor.

I don't particularly like a VCR, where the placement of the cassette insert is in the centre. I am used to the placement of the insert on the left. This makes maintenance and or a repair much easier to access. Don't judge me on this ! 😇

Nice test card ;-)

I like that magic fix. But can we talk about the rusty dirt-like stuck in the lower drum ? Should i be worried and inspect the drum. Scary

@video99couk

5 ай бұрын

I revisit this machine on my next video, due out tomorrow....

Congratulations. This was very interesting. I saw a video of someone changing the head switching point by moving the PCB that sits on the upper cylinder of the drum. This allowed to digitize tapes with the lines on the very bottom part of the picture being clean. But not all VCRs have a PCB there. Are there techniques to achieve this ?

Sir...with is f 04 error in Panasonic vcr plyer.

I've watched one of your older VCR repair videos where you applied a voltage to some part of the vcr. I think it was for increasing the speed of the loading motor or something. What test equipment do you use to apply a voltage to a VCR? I'm really new to all this.

@video99couk

5 ай бұрын

Probably to run a loading motor when the machine has a fault. I use a variable bench power supply with current limiting. But you could get away with say three AA cells in series.

I wonder if there is some change or degradation of a timing capacitor somewhere? Given the muck on the head drum is it possible that there is also similar build up on part of the circuit board?

@video99couk

5 ай бұрын

But it went suddenly from working to not. I think a sensor has failed in the head motor PCB.

An interesting problem and I'm not a VCR repairperson either but I would also have guessed that the problem would be that the head alignment setting got lost in the non-volatile memory of the microcontroller. If so, the problem will probably come back after being disconnected from the mains for a while. Looking forward to your analysis of the head position sensor. By the way, I didn't know until yesterday (when I ran into another KZread video about mastering audio recordings on VHS HiFi) that there were any European VHS VCR's that had EP/SLP mode. My understanding was that they simply never implemented it because PAL already had slower running tape and longer duration and there was simply no need. I remember before I emigrated I even had some E300 tapes which would record up to 10 hours in LP.

@video99couk

5 ай бұрын

Or the cynical me might say, VHS is quite bad enough already, do we really need to make it even worse?

@analogvideochannel4612

5 ай бұрын

PAL EP/SLP was mainly found on VCRs from SHARP and Panasonic plus some SVHS decks from JVC. It came very late though, the panasonic and JVCs with it are from the early 2000s, SHARP may have had it a little earlier in the late 90s but not sure. Don't think anyone else bothered with it, there wasn't much need for it as you say, even LP had been more of a premium feature on PAL decks already so most people tended to just use SP. Panasonic even made some 2 head models in the early 2000s that had PAL EP/SLP mode, I've never tried them but I doubt it looks good. It's bad enought on the 4 head ones.

@stpworld

5 ай бұрын

I think i have the 2005 version of this from Japan its one of my better machines I use it for playback somethings wrong with my svhs 1970 I havent had the time to sort it out yet. @@video99couk

@zhaohaigaogu7821

5 ай бұрын

テープガイドポストが緩くなり、ずれてしまうことが多いです。調整すると良くなります。調整後、細い六角レンジで固定しました。この方法はやったことありますが、テープの磁性のくずが残っていることは知らなかったです。勉強になりました。👍

Hi you have had so much experience with so many different units you are about the best one on the planet to get an opinion. I'm only asking because it's a "medical" S-VHS unit. I'm referring to the "Panasonic MD-835". Is this a good machine for movie playback? I noticed that recording with the HIFI setting it sounds good but not a punchy and clean as the source, say a CD I used to record to it should they record audio as good as the source?. What are your overall thoughts on these "Medical" S-VHS machines?

Perhaps I missed something here, but once you had managed to get the heads to switch correctly by misaligning the head motor board to compensate for the the head switch timing error I don't understand why then you then needed to use the calibration tape to set the head switch time?

@video99couk

5 ай бұрын

The mechanical adjustment was a course set. The electronic one sets it accurately. I should have mentioned that.

My guess is a hall sensor in the motor. If you get hold of a scrap machine it would be interesting to know. Not a bodge I would call it a justifiable modification Lol

I thought it was a motor issue before it was mentioned.

multi pole capstan motor/head motor shorted emf cap.

17:31 that's some good beat boxing going on there; a bass and a snare! Someone make a remix of this guy.

I had this one or very similar from New in 2001. Worst machine I ever had, it didnt last much more than a year.

It was guide adjustment fault but you accidently ended in opening the head and doing unncessary opreation

@video99couk

4 ай бұрын

No it wasn't a guide adjustment fault. See next part and you will see what the actual cause was. And it was inside the head assembly.