Panasonic NV-F55

[AidanLunn]

Hi all. This machine has recently started a "cycle" of actions when it is switched on.

This cycle consists of:
the feed spool rolls anticlockwise then stops as the idler moves right (as it would, obviously).
the cassette tray, while at "half-load" moves towards the cassette door
The idler moving right
The idler moving left
the cassette tray moving back to it's half-loading position
The machine turning a few cogs between the idler and the pinch roller (I believe it to be a G deck). These cogs turn a bit, stop, a kind of grinding/rattling noise is heard, then it continues to turn before retracting to its starting position.

The process just repeats itself ad nauseum.

This process did happen with the head drum spinning at a very low speed, but the head drum does not spin during this process now (though it does still work - see below).

The take-up reel doesn't move at all.

The cassette tray, when even the smallest bit of force is applied to it, does not move. When it is forced towards the cassette door, the takeup spool spins fast and then the machine shuts down.

Removing the ribbon cable going over the cassette tray just makes the machine make a rattling sound from underneath (like the grinding noise when repeating this cycle but at about half the speed.)

After this , it stopped making the cycle, I inserted a tape, the cassette tray took the tape halfway down, the A/C head loading arm comes out and the pinch roller lowers, both scrunching the tape up. the machine shuts down.

Switch it on again, and it lowers the cassette a little and the video head loading arms pull it around the drum, bit now the tape is much higher than it should be in the tape path (from it being lifted halfway down just moments previously). It shuts down.

When switched on a third time, it unloads the cassette, makes a clicking noise for a few seconds and then switches off.

I've checked all plug connections and looked for bulging caps (except in the power supply). Disconnecting the main board from the tape tray makes the machine believe there is a tape in there, load up and the head drum begins spinning at full speed. Connecting this back up and pressing the on/off switch makes the machine unload, but the two head drum arms retreat to their starting positions a little slower than normal.

I'm not sure if it is a mechanical problem or an electronic one. The machine was stood for some months, maybe a couple of years unused, (it's due a belt and idler replacement soon), or if the fault is electronic, as this, to my limited experience, suggests more of an error mode/electronic fault.

[Maarten]

The mode switch could be dirty. Also, defective capacitors in the power supply (even if they aren't bulging) are a common defect in Panasonic machines like this.

[Michael Maurice]

Aiden,

Inside the power supply can you will find a number of capacitors betwen the transformer and the power chip, i cant remember all the values but 680uF/25V, 390uF/10V and i think 100uF/50V, change the lot.

Squirt some switch cleaner into the mode switch.

These decks are complex and can be difficult for the unwary to work on, the timing of the gears is precise,

Before you do any work on the mechanism you must have the manual for the Panasonic G Mech.

I speak from experience.

Michael

[murphyv310]

The gears slipping like this will wear them out in no time. Once upon a time kits were available from SEME & CHS and these would include the required gears, whether these are still available I don't know.
As Michael says a manual is a must if you are not familiar with the deck, you must follow the setting up of the timing to the letter or it won't work.
And yes replace the electrolytics in the PSU

[HamishBoxer]

Never known any or many duff NatPan power supply caps to bulge.Certainly cause some very odd faults.Changing the lot excluding the 400V smoothing cap is indeed a good answer.

David

[radioredcat]

If it's a G deck then odd behavior will be the mode switch i always remove and dismantle and clean it.

The reason for not using switch cleaner i once sprayed the mode switch in a amstrad VS1000 satcorder with similar behavior and then it would not come out of standby.

So i removed the mode switch dismantled it and cleaned it and then it worked ok.

I still have 2 J30's and a J45 which are different revisions but on the J45 i had the intermediate gear strip it's just a small gog in the mech so replacement cured that problem.


Andy

[AidanLunn]

Thank you for the replies

I have done further checks (though not repairs yet) and the clicking noise is underneath.

Next to the main idler wheel (with six holes in it) there are two cogwheels with a thick white plastic axle between them. They are the same unit but it is in two halves so they spin separately. There is a pointy bit just above the teeth of the bottom cog on this unit. Inbetween these two halves, a white rocking arm comes down on the bottom half. This white rocking arm can be lifted by pressing down a small white lever to the right of this (if the front of the VCR is facing upwards).

The clicking is the pointy bit of the bottom cog pressing against the rocking arm, which, I presume, should lift up in this mode. The top cog on this unit spins as it should, whereas the bottom half doesn't. When this arm is down, preventing the bottom half from moving, the top half moves but "twitches" in sync with the clicking noise coming from it. It's obvious that both halves are connected with some sort of spring.

So this little arm is not lifting up when it should do. That's not likely to be the cause of the problem, but at least it's a solved mystery.

[Red to black]

Hi Aidan,

G-Deck Mechanism manual sent.

Cheers,
Baz

[HamishBoxer]

Been on CHS site and dont think the gear kits are available any more,how ever it seems certain gears are.

Hope this helps.

David

[Michael Maurice]

From what Aiden tells us, the mech alignment seems fine, the mode switch might need removing and cleaning but you have to do it very carefully.

If you do go down this route follow my instructions below:

With the machine in the EJECT state, note exactly where the hole in the mode switch is, it should IIRC be in the 5 O'clock position.

Remove the cap holding the pinch roller in and remove the pinch roller. Make sure you do not lift the helter skelter gear, if you do you may have a problem refitting and realigning it.

Use solder braid to carefully remove as much solder as possible from the tags of the mode switch.

With a small jewellers screwdriver unsolder and carefully lift each tag in turn.

Remove the small screw

Lift out the mode switch.

Carefully take the top of the switch off and thoroughly clean the contacts using switch cleaner and a cotton bud.

Refit the mode switch making sure the alignment hole is in exactly the same position as it was when you removed the switch.

Resolder the 5 tags

Refit the pinch roller and cap

If you need to realign the mechanism for any reason, the mode that that the alignment is referenced to is the STOP mode.

That is carriage down and P5 gear in half load position.

Good luck