Panasonic NV-F75 - Display not working - UK Vintage Radio Repair and Restoration Discussion Forum

Nordmende · 23rd Sep 2023, 7:15 am

Cheers,
i am just working on a Panasonic NV-75. The complete Display is OFF! After a PowerSupply "Spa", there ist no change. I also tried another Display which works perfect in another machine...no change. The SM shows Heating +/- are directly coming from PwrSply. I measure neg. 20V on both Pins. Any idea where to continue fault finding?
Thanks br and take care

vhs doctor · 23rd Sep 2023, 6:40 pm

Hi

Measure the voltages on the display controller. Be sure that the voltages are the same under load.
It is better to recap all the power supply section and also check on other boards for leaky capacitors.

Nordmende · 24th Sep 2023, 5:33 am

@vhs doctor
Thanks for fast response. I measured again directly over Heater+ and Heater-. There normally should be a difference voltage about -4 to -5 V. I had no difference. I again recaped some of the capacities as well as the 20V Z-Diode. I then meausred all Voltages directly at the Terminal Strip which are distributed to the VCR. All voltages were okay. I even measured a difference voltage between the heater Pins of -5V. Strangely enough, i couldn't measure it at the Terminal Strip connected directly via the PCB Mainboard to the Display

So my conclusion was, that there must be an interruption on the Board. I tried a directly connection "On the fly" ....all of a sudden -> Display worked perfect. Strange but on this way it works perfect.

23rd Sep 2023, 7:15 am	#1
Nordmende Diode Join Date: Sep 2023 Location: Cologne, Germany. Posts: 5	Panasonic NV-F75 - Display not working Cheers, i am just working on a Panasonic NV-75. The complete Display is OFF! After a PowerSupply "Spa", there ist no change. I also tried another Display which works perfect in another machine...no change. The SM shows Heating +/- are directly coming from PwrSply. I measure neg. 20V on both Pins. Any idea where to continue fault finding? Thanks br and take care

23rd Sep 2023, 6:40 pm	#2
vhs doctor Pentode Join Date: Oct 2011 Location: Athens, Greece. Posts: 173	Re: Panasonic NV-F75 - Display not working Hi Measure the voltages on the display controller. Be sure that the voltages are the same under load. It is better to recap all the power supply section and also check on other boards for leaky capacitors.

24th Sep 2023, 5:33 am	#3
Nordmende Diode Join Date: Sep 2023 Location: Cologne, Germany. Posts: 5	Re: Panasonic NV-F75 - Display not working @vhs doctor Thanks for fast response. I measured again directly over Heater+ and Heater-. There normally should be a difference voltage about -4 to -5 V. I had no difference. I again recaped some of the capacities as well as the 20V Z-Diode. I then meausred all Voltages directly at the Terminal Strip which are distributed to the VCR. All voltages were okay. I even measured a difference voltage between the heater Pins of -5V. Strangely enough, i couldn't measure it at the Terminal Strip connected directly via the PCB Mainboard to the Display So my conclusion was, that there must be an interruption on the Board. I tried a directly connection "On the fly" ....all of a sudden -> Display worked perfect. Strange but on this way it works perfect.