Panasonic nv fs 90 no clock or display

[rs2klee]

hi, new to the site and just wanted to say hi to everyone

For those who know more about these recorders than i ever will, my trusty fs 90 Panasonic was working fine. Then one day i noticed that the clock was not on, So thinking oh the plugs probably loose but no the power was on and it turned on and beeped. It accepted a cassette and plays ff rw with picture. Just no display any ideas on this one ?

[paulsherwin]

Assuming this is a VFD display, this is usually caused by the heater power supply failing. Sometimes this is protected by a Wickman fuse which has failed through old age rather than any actual fault. These can be replaced by a conventional fuse of the same value in a holder, but look like a PCB capacitor or inductor.

https://uk.farnell.com/littelfuse-wi...ing/dp/1716616

[Red to black]

The NV-FS90 certainly used VFD displays, I don't think they used any wickmans in that circuit though, I will have a look at the diagram sometime tomorrow, more likely to be one of the well cooked capacitors in the enclosed power supply.

[dj_fivos_sak]

Hi. Is the filament heater supply working? It should be measured between pins 12 and 13 in the power supply, labeled HEATER + and HEATER - in the schematic. There is an electrolytic cap (470uF 6V) across this supply line.

Fivos

[John123]

Originally Posted by Red to black

more likely to be one of the well cooked capacitors in the enclosed power supply.

Agreed, it gets pretty toasty in there..and given the age of the unit it sounds like it's done quite well, all things considered. Blanket replacement of all PSU capacitors is the only reliable long-term solution..

I recall it was Philips that favoured those Wickmann fuses. JVC had those IC protectors that looked like two-pin transistors. I wonder if Panasonic went with those white fusible resistors like in their tellies?..

[rs2klee]

hi, Thanks for the replies, I have another 2 power supplies I tried and they all did the same thing. it powers on but no display I know its a long shot but would anyone have a picture on the board that needs to be changed ? I can take a couple pictures as its all in bits at the moment, my other one is working kinda, but will not play svhs tapes just a black screen! I have 5 of them so hoping i can get at least 2 working again. I just bought caps for the power supplies thinking thats what i needed and just bought another 2 as the screens power on fine both just have no picture and is just a mess, but does have good sound!

[rs2klee]

Update: I have changed all the power supply caps and still same thing, so the other 2 power supplies i have do the same thing but thought re capping the lot might change the way it behaves. here is the list of the ones i replaced:

C 26 = 16v 47uf #
C 14 = 16v 47uf #
C 25 = 10v 100uf #
C 24 = 10v 100uf #
C 32 = 16v 10uf #
C 19 = 16v 680uf #
C 20 = 16v 680uf #
C 27 = 6.3v 470uf #
C 21 = 50v 10uf #
C 18 = 50v 100uf #
C 22 = 10v 680uf #
C 9 = 400v 1uf #
C 8 = 400v 68uf #
C 23 = 50v 10uf #

I did at one point think oh its that screen that does not work so put that screen in another machine but it works just like the other 3 I have.

So power is going into the main board but getting lost somewhere. I`m really stuck now and to top it off the one im working on has now lost sound! if I pause and play the sound comes on for about 2 seconds then goes off again.. I think im loosing the battle even though I have 4 of the things!

Originally Posted by Red to black

Blanket replacement of all PSU capacitors

Done them all, to no avail

Just a small update, managed to get the screen working by swapping out the board from another on into my main one... now no picture at all! loving these old players they are like a puzzle game in real hardware

[berry62]

Maybe there is a dc to dc convertor circuit on the front panel that has failed?

This converts the dc up to -30vdc

[Station X]

Originally Posted by rs2klee

hi, Thanks for the replies, I have another 2 power supplies I tried and they all did the same thing. it powers on but no display I know its a long shot but would anyone have a picture on the board that needs to be changed ? I can take a couple pictures as its all in bits at the moment, my other one is working kinda, but will not play svhs tapes just a black screen! I have 5 of them so hoping i can get at least 2 working again. I just bought caps for the power supplies thinking thats what i needed and just bought another 2 as the screens power on fine both just have no picture and is just a mess, but does have good sound!

Have you taken any voltage readings as suggested up thread?

[berry62]

I downloaded the service manual for the FS-90.

If the power supply delivers the right voltages check the voltages on the display.

It could well be caused by a crack in the front circuit board or bad solder joints.