The arm in the centre is for static discharge. Without it, on a machine originally fitted with one - which most are - you tend to get little white dots on the playback picture. Provided the heads *are* exactly the same, then there are no alignment issues with head swaps on modern VCRs. It is only two screws, so give it a go. Normally, the screw holes are offset slightly to make sure that you don't get it on 180 degrees out. At worst, it just won't work. As a matter of interest, what are the symptoms for your diagnosis of failing heads on the first one ?
A child's plastic "toy" microscope of x20 or x30 magnification. Just the barrel is useful for inspecting with part of the objective end ground down at an angle, back to (or even into ) the lens, allows to get close enough for video heads to inspect, in situ , when illuminated with a torch. To inspect whether the gap is chipped and generally whether worn down too much. View in a downwards sense wherever there is enough clearance.
-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on
The OP should be advised that in certain cases (unless things have changed in the past decade)you need a head puller. I've replaced many voice coils from inexperienced techs who destroyed them while removing a head.
He's not wanting to remove just the heads, he wants to remove and replace the whole cylinder with heads attached to the other unit. Its only 2 or 4 screws on the thing and you move it over and place it down in the other VCR.I have done this sucessfully from an old Mitsubishi U-760 to a U-770 if i remember right(Its been years).
But with his situation, the parts are completely different between the units. I would advise against it with these two units.
Given that info, it's probably not going to work right. Hifi sound is critical of correct head performance, so if there are any specification differences between the head drums, there will likely be a problem. As far as swapping the entire head drum assembly goes, you will often find that even identical-looking assemblies won't fit because a screw hole or chassis locating boss has been deliberately offset to prevent it. As for having to use a puller to remove the upper head drum (which I have always thought is a far more straightforward job than swapping the whole assembly) on some machines, that used to be a given, but I always found that Pans came off ok.
Not that for some years it's been a viable proposition to replace heads, even on 'good' machines. The cost of the head drum alone, without any labour, exceeded tha cost of a bargain warehouse all singing and dancing machine with a shiny new 2 year warranty ...
I see. I took the OP's description of "Head Unit" to mean replacing the head unit (unit with the heads in it that can be replaced separately.) and not the "whole cylinder" whatever that means.
That is the upper and lower drums, spindle motor and the head electronics. Unscrew it from the chassis, unplug the cables and change the whole assembly.
That is how heads are changed on R-R broadcast tape machines, like the 1" Sony machines we used at Ch. 55 in Orlando. If you were used to it, you could drop a new $1100 head into the machine in under 15 minutes, and be back in service. It came prealigned and tested. You didn't have to take the machine out of the rack or unhook anything else. It was one of the things I liked about Sony Broadcast Electronics..
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When the video starts to get noticeably bad a screen will pop-up that says the heads need to be cleaned. So for yrs I've been taking the top off and cleaning the heads when the screen appears. (white piece of paper with rubbing alcohol holding it against the heads on the upper drum while turning it counterclockwise - alcohol and Q Tips for the erase and audio heads) Put the top back on and everything is great until they get dirty again.
So earlier this week the picture started looking *really* bad, and sure enough there is the screen telling me the heads are dirty...so I do my usual procedure, only this time, the picture still looks like crap. The warning screen isn't coming up, but previously recorded tapes in EP mode look horrible, any tapes I make in EP mode look horrible.
Tapes that I've previously made in SP mode look OK and store bought movies look OK also. Not great, just OK. (Same with making a tape in SP)
Before any of this happened, while watching a recorded EP mode tape if I were to hit rewind to back up the tape, about 25% of the upper screen was nothing but noise lines/snow.
But, this would only happen if it was near the beginning of the tape. Once you got past a certain point (3/8ths - 1/2 way) this problem would go away.
After cleaning the heads, this problem is still present. I can fix that problem by adjusting (big adjustment 1/4 turn) the feed side roller guide, but the picture still looks horrible.
So, after reading many articles, I can only come to the conclusion that one of the 4 heads in the drum/cylinder went bad.
I haven't had time to switch the heads yet, when I do I will post the results.
Meatplow, after removing the 2 small screws, the upper part of the drum/cylinder, what ever you wanna call it, just lifts right off.
When the video starts to get noticeably bad a screen will pop-up that says the heads need to be cleaned. So for yrs I've been taking the top off and cleaning the heads when the screen appears. (white piece of paper with rubbing alcohol holding it against the heads on the upper drum while turning it counterclockwise - alcohol and Q Tips for the erase and audio heads) Put the top back on and everything is great until they get dirty again.
So earlier this week the picture started looking *really* bad, and sure enough there is the screen telling me the heads are dirty...so I do my usual procedure, only this time, the picture still looks like crap. The warning screen isn't coming up, but previously recorded tapes in EP mode look horrible, any tapes I make in EP mode look horrible.
Tapes that I've previously made in SP mode look OK and store bought movies look OK also. Not great, just OK. (Same with making a tape in SP)
Before any of this happened, while watching a recorded EP mode tape if I were to hit rewind to back up the tape, about 25% of the upper screen was nothing but noise lines/snow.
But, this would only happen if it was near the beginning of the tape. Once you got past a certain point (3/8ths - 1/2 way) this problem would go away.
After cleaning the heads, this problem is still present. I can fix that problem by adjusting (big adjustment 1/4 turn) the feed side roller guide, but the picture still looks horrible.
So, after reading many articles, I can only come to the conclusion that one of the 4 heads in the drum/cylinder went bad.
I haven't had time to switch the heads yet, when I do I will post the results.
Meatplow, after removing the 2 small screws, the upper part of the drum/cylinder, what ever you wanna call it, just lifts right off.
Yes, that is normally the case with Pans. Sounds as though one of the heads may have become chipped, but it is also possible that one of them has become badly blocked. Sometimes when that is the case, it's necessary to get a bit vicious with it. A trick that was shown to me by a manufacturer's service course lecturer, is to hold a fingernail against a running tape, as it is around the head drum - so that you can feel the heads going "DRRRRRRRRR" against your nail, through the tape, if you see what I mean. It is amazing how quickly and how well this recovers a head that has become badly clogged from a tape that is moist from condensation, or is shedding oxide. It has got me out of trouble on many occasions.
Put the head drum from the older working VCR into the newer one, there was no signal on the face plate for "HiFi".
So I put it back into the - what was working unit - and NO HiIFi.
Don't know what happened, but the newer VCR fried something in the older ones head drum.
Now I have 2 Panasonics that don't work. :(
I feel that to be highly unlikely, as the coupling between the heads and the amplification electronics is completely isolated by a rotary transformer, the primary of which is in the upper head drum, and the secondary, in the lower.
Far more likely is that the screw-holes are not offset, and you have managed to get the upper drums 180 degrees out on the centre spindle. Unscrew the formerly good one again, and try turning it through 180 degrees, and see if the holes still line up. If they do, screw it down again, and retest. If that gets you back to working, then try your swap again, taking note of the same potential problem.
The upper drum(s) can only go on one way. It has a pilot hole for a guide and the screw holes are also slightly offset.
Don't know what happened, but switching them fried something in either the units themselves, or in the upper drums.
*Both* units with their original heads have video, but the audio is muddy. I cleaned both using the fingernail method you mentioned, followed up with paper and alcohol, no change.
I worked there in 1987/88, and the place was already a pain. I avoided I-4 as much as possible, and used 441 to go home in Lake county. Ch 55 was on Parkbreeze Ct, near 441 & Lee rd. Part of my time was spent at the transmitter sites in Orange City, or Lisbon, and the original studio site in Leesburg.
It was amazing the number of people who drove like Orlando was still a farm town. they would stop short of the buried sensors in the roads, and force the light into the default cycle, leave three or four car lengths between them and the next vehicle. The worst were the ones who waited 15 seconds after the light changed, before pulling into the intersection at 5 MPH. (And never getting close to the speed limit) :(
A few years later I worked in Altamonte Springs and the difference was amazing.
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