Electronics > Beginners
Pulsing Vacuum Fluorescent Display
sarahMCML:
Hi again,
I get it now, your Vmax and Vmin readings are the peak to peak values of the 3.35 Volts that you measured across pins1 and 39 with your multimeter.
Does the VFDisplay module itself have a part number marked on the back that you can find? I ask because if we can find out the maximum operating voltage for the filament it might be possible to increase it a little, get rid of the pulsing effect, and get a little more brightness!
Regards,
Sarah.
Electro_Jr:
The service manual for the stereo calls this out as IC551 part number of....TD62C950RF Sony Part number of 8-759-075-35.
It also gives a part number for FL521 1-519-735-11 Indicator Tube, Fluorescent.
My readings are this
FLV30: +37V DC no ripple respect to Ground
FLA2: +6V DC no ripple respect to Ground
FLA1: see pics
Fla1 to Fla2: See Pics
sarahMCML:
Hi once again,
I couldn't find any data for that VFD, so the only thing to do is to try a couple of things, if you think that they are worth the risk.
You can use a DC power supply, connected directly across FLA1 and FLA2, and, starting from 0 volts, slowly raise the voltage until the filament glows visibly red. Leave it like that for about 60 seconds, remove the PSU, and power the unit. With luck this MAY rejuvenate the filament. But if you put too much voltage across it you could burn it out!
The other thing you could try is to put an extra turn or two on the transformer (if there is space for winding it around the outside of the existing windings, of course), checking that it only gives about an extra 10% voltage (0.35V-ish AC), and connecting it in phase, in series with the existing filament supply. Again, it may or may not work!
Regards,
Sarah.
vk6zgo:
Your display may be "gassy"---- in other words has lost it's vacuum to some extent.
From memory, this can cause oscillation in vacuum tubes--- usually they just stop working, but it does occur.
The vacuum displays may have the same problem.
macboy:
--- Quote from: vk6zgo on November 28, 2018, 09:47:34 am ---Your display may be "gassy"---- in other words has lost it's vacuum to some extent.
From memory, this can cause oscillation in vacuum tubes--- usually they just stop working, but it does occur.
The vacuum displays may have the same problem.
--- End quote ---
This can be easy to test. There will be a "getter" inside the VFD glass (google it). This should look like a block spot in one or more corners of the tube. If it is white or cloudy, you have air ingress.
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