Panasonic PV-4841 VCR (from 1988) repair attempt

[@Tdub20]

just found this channel and i love it since i like repairing and using old VCRs like this too.keep doing what youre doing !

[@luvradios]

If I recall correctly and its been decades now since I've worked on one of these, the back panel of that unit should have a gold screw in the lower center, if you remove that you should be able to hinge the entire back panel without removing the board from it. I am both surprised and impressed you were able to get the cassette housing retimed in the fully unloaded position, the way we learned to do it from Panasonic was to load the test jig tape (basically just a gutted cassette housing) in the stop position (tape guides not threaded up) which should line up the timing marks of the mode switch to the cam gear. You were smart to clean the mode switch but also clean the tape position switch on the cassette housing as that will cause intermittent operation. (tape goes down and comes right back up) When the tape is glitching in SP use your finger and manually lighten the pressure on the back tension arm and see if that clears it up, if so you could have too much take up torque which would mean the clutched gear on the takeup reel is bad. The other person who serviced it was def chasing the same issue and so many times guys will change ic's or other unnecessary shit only to find the issue was mechanical all along lol, I heard you mention in the video: "is it mechanical or electrical"? so you are def asking the right the questions my friend and you are 100% correct - I did throw hundreds of paper manuals away when I closed my shop, including that model and or the training manual for that series, later Panasonic would issue us the manuals on CD ROM which I still have a few disc's, I will look and see if they went back that far and if so I can email you a PDF. Damn Good video man, takes me back!

[@probnotstech]

Good point on tape tension! I'm putting together a list of things to try from the comments and yours was extremely helpful, thanks!

[@VCRGame88]

always a good day when this guy makes a repair video

[@lawrencecavens5760]

the one thing that might help in diagnostic is If that encoded strip on the capstan drive has been subject to a heat source - it'll be ruined... just remember that - which might of been from the previous teck.

[@probnotstech]

Yeah I did mention that early in the video. I'm not sure that would be it though as all EP tapes and some SP tapes seem to play fine

[@crashbandicoot4everr]

I was able to find an NV-F65PX service manual online. It looks almost identical to this one.

[@probnotstech]

Oh neat, where at? I have a feeling the servo circuit will be at least slightly different being PAL, but worth a look.

[@crashbandicoot4everr]

@@probnotstech It's not PAL, it's actually an NTSC model for PX (American bases in other countries). I believe it's identical to the 1989 series of North American Panasonic G mechanism VCRs like the one you have. The PAL version is the NV-F65EG/B and it's totally different from the PX version. If you can't find it let me know and I'll try to post a link somehow.

[@crashbandicoot4everr]

@@probnotstech Capstan/drum motor drive board on the F65PX is a VEPS02122A1 (VJBS02122). If it's the same or similar to yours then we're on the right path...

[@ronwilgenbusch1961]

I had a similar situation recently with a JVC, it would drop in and out of hifi on some tapes and not others and it would act like the audio control head was at fault. Ended up being 2 minor issues. The pinch roller was slowing and speeding up on SP, but EP was rock stable most of the time. Lubricated the pinch roller shaft, and a slightly loose screw on the ground close to where the ribbon cable for audio control went on the circuit board. My guess is that the tape wind tension was different from tape to tape and was putting more tension on the pinch roller/capstan.

[@probnotstech]

I'll definitely be looking into that on this one, thanks!

[@jaytender5790]

Neat! Probnot, I like your videos. I used to work on these when I worked for Panasonic. One thing you did not mention checking is the power supply? And we all know about the caps in these units going bad. Maybe some excess ripple on a supply line coming out? I don't think I'd still have a service manual for this one anymore. The ic's never went bad very often, can't say I replaced alot of them. The 3 small devices on the capstan motor board are hall effect sensors, to monitor the speed of the motor. When those go bad, the motor spins out of control too fast. Good luck trying to fix this, kinda a strange problem. It's a nice example of a 'G' chassis.

[@probnotstech]

Thanks! That's a good point about the power supply. I didn't check at the supply itself, since I would expect some ripple on any of the pins providing a non-regulated power (which some VCR power supplies do) and I have no idea which ones are which. I did check all the voltages at the jungle IC with a multimeter and scope and didn't see anything concerning. But still, that doesn't fully rule out the power supply. I'm hoping that between taking a break from this repair, and maybe someone out there having more info I could get it fully fixed up. Because yeah, it is a nice little example, isn't it?

[@ipaschke]

I have a very similar problem with a Hitachi VT-LC50EM. It plays most SP tapes just fine, but LP tapes have exactly the same speed dips like on your machine (mine has these with the slower speed)... Some SP tapes have white streaks while playing that you can't get rid of even with manual tracking adjustment, mostly commercial tapes. I'm very interested what you might find in a follow up to this.

[@waterup380]

Panasonic Romotes can be used on dvd and other VCRs that are Panasonic Brand

[@orange_light_pictures]

Did you try and adjust the hight and path of the tape on the control head. there should be two screws you can adjust for the axis of the head against the tape?

[@probnotstech]

I did! I tried adjusting it for best linear audio (which I got quite an improvement from) and when that didn't work, I just tried hunting around with the height and azimuth to see if it would help.

[@orange_light_pictures]

@@probnotstech I thought you prob had done, thought I'd say anyway. I did the same thing with a NEC DX 1000 until I dropped a screw I'd unwound breaking the timing of the lacing Mech. I was very angry at myself, as It was a VCR of my late Grandads.

[@jameshamric]

Try replace caps in ps. 5v I think if no improvement try the 14v. I really like these unit. Called g chairs I think. Good luck

[@WolfmanDude]

Is there a 80s Panasonic VCR that you would recommend? In terms of mechanical reliability/serviceability. I am super happy with my NV-180 but I am currently looking for a cheap, common and normal size model for a friend. We had terrible luck with bad rubber rollers so far...

[@probnotstech]

I can't really recommend one specific model as I'm not familiar enough with them. I usually say the best VCR is a working VCR. Statistically yes some are more problematic than others, but they are 30+ years old now, and there are so many factors - how much usage, storage conditions, any past repairs, or even just luck. Now if it's just down to cool factor? Any of the high end mid 80s decks are my favourites (PV-1430, PV-1631, PV-1730, PV-1640, PV-1740, PV-1742). Also really like the look of the PV-4760.

[@WolfmanDude]

@@probnotstech Thanks for the info, I check all of those models out! I am trying to avoid those models where the reels are driven by that rubber roller! Panasonic never did that, right?

[@crashbandicoot4everr]

@@WolfmanDude Panasonic switched to the geared idler in 1986 for the North American D1 deck models, and European G deck models. There's no European D1 deck machine with the gear, they all have the rubber idler (NV-G7/G10/G12 etc). The NV-G20 series/G200EM was the first G deck model for the PAL/SECAM markets. Most of these models can also be found branded as Blaupunkt. The PV-1730 and NV-180 share a very similar mechanism where both the take-up and supply spools are directly-driven by separate motors, just like the Sony 711D chassis Betamaxes (SL-C9, SL-2500, SL-2700 etc).

[@WolfmanDude]

@@crashbandicoot4everr Thank you soo much, thats invaluable info to me!!! I will look for that Blaupunkt model for my own collection. I absolutely love the the mechanism on the NV-180. Every rotating element has its own BLDC motor. I did a full restoration and alignment on my NV-180, its my favorite device. You need to do a special procedure to re-lubricate the video drum bearings on the NV-180. Are panasonic G decks any good? I found many of those for cheap, I consider getting one of those for my friend.

[@crashbandicoot4everr]

@@WolfmanDude I have a 1989 NV-L20 (G-REV(ised) deck) and a 1992 NV-FS200 S-VHS (GII deck), same as the North American AG-1970. The difference is the extra motor for reverse slow motion and reverse picture search, and much faster loading/unloading. On the L20 I had to replace one capacitor in the power supply and resolder the connector for the capstan motor. Re-timing the gears on these can be a pain as they are very complex (I have done it). The previous D1 deck is much simpler but uses lots of rubber parts.

[@jamesbennettmusic]

Have you tried recording something to it like a test tone and see if it prints to the tape with a wobble (maybe play the tape back in a known good machine or so?)

[@probnotstech]

I did! I kinda glossed over it at the end, since the video was getting so long. But I did record on all 3 speeds and it played back fine on this VCR, and another (Toshiba OEM) VCR I had handy with no issues.

[@tambarskelfir]

I love a good mystery! Seems bizarre to me that it matters what VHS cassette you use. I was entertained.

[@lukasgayer5393]

Nah, your heads are OK. This is where you A - need to change the small capacitors next to a servo circuit OR you have to glue back the felt pad to the left brake belt because it has fallen off and the tape doesn´t have enough countertension to adhere to the heads and tape path. Check on these.

[@probnotstech]

I checked the caps, but will be checking the tension next, thanks!

[@oppok5657]

had this same problem happen to a sony that would also blue screen and would only show a picture when pausing and fast forwarding. I never ended up being able to fix it

[@probnotstech]

It ended up being a dirty video head on this, but a damaged head can also cause the same problem.

[@oppok5657]

@@probnotstech i tried everything even to adjusting tape path, but i could never get it to display. i hate the blanking feature that many consumer vcrs had. I also had this other sony which was basically a similar model to the last one but was cheaper and didn't have the blanking feature. The SP heads on that one broke one day to the next and no amount of cleaning or capacitor replacing could fix it, only one field was actually complete and special effects like pause looked perfectly so that leads me to think that only one of the heads got damaged. And to add to this, i had yet another model similar to the last two that also had the same field issue. Looks like Sonys here in Argentina were manufactured very cheaply, i think the models were like SLV-L75HF, L74HF, and L44. For a few years i've had 2 Panasonic NV HV60 manufactured in 2005 and no problem with them.

[@jameshamric]

I used to change entire ps when I could get for 20.00$ or so.

[@aljosamlinaric8705]

Anything is better than Kingston usb. i had similar experience with Kingston. Just buy sandisk. The only kingston that's holding up is DT50