Panasonic NV-FS100 power supply fault

[Vauxfan2k]

I've dig out my fs-100 which was working when used over a year ago,

The display came on for a short while but before I got a chance to put a tape in it went off. I checked the plug fuse and the internal fuses but all check out ok.

I replaced the caps this morning after doing research online but all I get now is the initial charging sound of the capacitor but still no display. I really hope it's not the ic as they are no longer available.

Does anyone have any experience with there that can give me some things to check next?

Thanks

Steve

[steve1010uk]

Could be worth checking the diodes on the secondary side of the PSU transformer for short circuit, also the protection zener diode D1116 which will go short if the LT rails rise due to dodgy caps.

Steve

[Vauxfan2k]

Grabbed a couple of pics,

It looks like it's been pretty hot in there while in use, on hindsight I should have fitted a small fan on the back of the heat sink last time.


I tried the local tv repair place and he seemed keen to have a look until I told him it was for a vcr. He then rapidly lost interest and told me to find another psu (cos they grow on trees dont they?!)

If some kind soul could point to what I need to check in the pics I'd be very grateful.

Thanks

Steve

[steve1010uk]

Start by finding D1116 on the power supply, this is a zener diode whose only purpose in life is to go short circuit should the voltage increase, if it has gone short circuit you will probably have dried up electrolytic caps, best to change the lot !

Steve

[HamishBoxer]

Change all primary side caps except smoothing cap ,normally but not allways ok.I can see a few suspects in there.

[Welsh Anorak]

Agreed - also have a look at the secondary caps. There's a small tired looking one to the right of the transformer and also an olive green one by the fuse that looks similar to ones that are known for giving problems - it could be a replacement.
Use best quality 105 degree Panasonic replacements (CPC stock them) as they have a very hard and hot life in there.
Good luck
Glyn

[steve1010uk]

D1116 may just be marked D16, and looking at your second pic i think (but are not 100% sure) that it lt may be the black one near the top left hand corner near the fuse.


Steve

[Vauxfan2k]

I have the day off today so will look into the locations of the parts you mention. Managed to source another machine with a working psu so will use that to go by when testing this.

Thanks for the replies

[Vauxfan2k]

The replacement psu came today and after fitting it am pleased to say he machine is now fully working again. The ic chip has cooked on the original psu so not Salvagable.

Here is a pic, bottom one is a donor machine which plays vhs but not svhs.


Cheers

[Vauxfan2k]

Pic of machine working along with my nv-f75

Loving the design of these machines.

[dj_fivos_sak]

Nice work! I have a FS200 that works but has a very dim display. Could this be a PSU issue?

[Vauxfan2k]

The dim display is probably caused by the glass on the display and also the clear window on the inside of the front panel having a powdery type coating caused by the heat from the machine. One of my Ferguson 3v35s had that issue. It can be cleaned off with a bit of fairy liquid on a cloth and then drying. It makes a massive difference.

The front panel is easy to take off on the panasonics, just take off the lid, open the front flap. Remove the centre screw from the top edge of the fascia and pop the clips at the top corners and along the bottom. Pull outwards.

Will make some videos of the fs-100 working as the couple on YouTube are of ones that have faults or purely playing music.

Cheers

[Vauxfan2k]

Took the faulty psu to a friend that dabbles in electronics and has all the gear.

The zener diode d16 had gone short. The caps all checked out ok, so the one that was replaced must have been the culprit. He powered the supply out of the machine (hadn't taken the whole thing to him) and there is now voltages at the pin outs. He says it should work ok now with the diode disconnected, if it does then to source another diode or I can run the machine as is.

Does anyone know the voltage rating for the diode?

Thanks

[HamishBoxer]

No replace with correct diode to save further problems.

[Vauxfan2k]

Well it didn't work with the diode removed, the machine lit up for a few seconds and the mechanism made the usual noise when it's been left off for a while then I heard a fizz and off it went.

I'm missing the 14v and 12v supplies. Suspect c15 has blown as it's all black, tracing the wiring diagram suggests the primary voltage isn't getting past this point.

Was suggested I cut the leg of the cap so the voltage bypasses it but I don't know what else would pop if I do this.

Fighting a losing battle.

Nothing in this psu is the same as the donor f75/fs90 psu.

I could be really crude and connect up a 13v power supply to the ribbon connections for the 12 and 14v but that's not gonna be pretty or long term.

45v and 5v are present. -29 isn't however.

Any ideas?

Thanks

[HamishBoxer]

Has anyone got a circuit for this? Running without a zener and cutting legs off a cap is heading for total destruction in my view.

[Vauxfan2k]

I'm not daft enough to cut the leg off the cap duff or not. I have the wiring diagram for it, but it's finding the parts, even then I can't guarantee it won't just blow the replacement parts. It doesn't help that it's completely different to all the other machines. The f70/75 and fs90 use the same psu. The f77,fs88 and fs200 have the same type. Can't vouch for the f65 as I have only had the lid off once. Doubting the j35 or l25 are similar to any of those.

[steve1010uk]

The zener D1116 is 16V 1 watt, it's only purpose in life is to go short circuit should the 14v rail rise thereby offering protection, the fact it was short circuit means this is what happened and it did it's job, running without the zener if the increased 14v rail has not been corrected is a recipe for disaster.

The usual cause of increased 14v line is capacitor C 1122 16 v 1200 Mfd going low in value but its a good idea to replace all electrolytic caps in this power supply with good quality 105 degree devices

all part numbers on the power supply begin with 11 but may be marked on the board with only last 2 digits ie D1116 on the board may be just D16

C1115 is 330pf 1kv and is on the primary snubber network, if its black and cracked it certainly needs replacement not removing
I have the service manual although its not a great copy its readable and if you pm me with your email address i will send a copy

Steve

[Vauxfan2k]

Thanks will pm you shortly. It won't be myself doing the work on it, so may take a couple of days to do any further investigation.

[Vauxfan2k]

This is what it currently looks like.