Author Topic: Vacuum fluorescent display rejuvenation...SUCCESS  (Read 35577 times)

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Offline Signal Simon

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Re: Vacuum fluorescent display rejuvenation...SUCCESS
« Reply #25 on: May 10, 2019, 02:10:02 pm »
I have a home cinema amplifier, Sony STR-DB985D with a very tired display.
It's a unit I acquired for repair and to use as it seems to be the only model I could find with integrated DAB tuner.

This doesn't seem to be just a case of worn phosphors, as the rarely used segments are also very dim, just a little less so.
The heaters do seem very bright compared to other VFD displays I have seen. I have not measured the voltage as yet.

I suspected a low negative rail, but it is at -18.7V as per manual (although labelled -28V).
I am going to try and source a replacement display, the same part number seems to be used in a number of models.

Could the display have been damaged by the filaments being over-run from new (production issue)?

Simon.

 

Offline james_s

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Re: Vacuum fluorescent display rejuvenation...SUCCESS
« Reply #26 on: May 10, 2019, 06:26:35 pm »
It's possible, or the filaments may be contaminated, you could try heating them up to a yellow glow for a few seconds and then return to the rated voltage and see if it makes any improvement.
 

Offline Signal Simon

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Re: Vacuum fluorescent display rejuvenation...SUCCESS
« Reply #27 on: May 12, 2019, 09:43:06 am »
Cheers, I will give it a go.
I did get another Sony AV amp, but the display was different.
In that case, there was no display because the negative supply was missing.
The negative voltage was -33V (again as per manual) once restored.
The display on that unit is good as new and there is no visible glow from the cathode.
Interestingly, the driver IC is the same, albeit one is NEC uPD16315 and the other is Princeton PT6315

I've attached a photo of the display on the DB895D, you can see how bright the cathode wires are glowing.
The display looks readable on the photo, but when you consider the relative visibility of the unlit segments, it isn't bright at all.

It will be another week or so before I have another go.

Simon.
 
« Last Edit: May 12, 2019, 09:47:36 am by Signal Simon »
 


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