Sony Digicube Clock Radio

[DerbyBorn]

Old but still working - analogue radio, The time display is not as bright as it was - green fuorescent. Can it be tweaked up a bit?

[Harry Bloomfield]

DerbyBorn pretended :

No, with use they wear out and become dim.

[Brian Gaff]

Not really. The inside of the little cells gets blackened and sometimes the cathode coating becomes inefficient. In one case where somebody tried to increase it it started, presumably by some kind of static system to illuminate some of the adjoining segments. that was a Casio clock radio with a similar tube type display. Worth a try, but be careful

I think the cassio one had about 100 v from a little inverter on it. Brian

[Brian Gaff]

The worst one I had was a Decimo Jumbo digital clock. Of course it was not digital at all, it was basically a rotating sequencer each contact lighting a neon behind the frosted segmaent on the front. Eventually as the neon's got blackened the segments were all different brightness's. I did take mine apart and replaced them and used a slightly larger resistor to make them all a bit dimmer to save them, but eventually the work needed and my reducing eyesight made it somewhat pointless to fix. Talk about a daft design. Brian

[Bob Minchin]

You might be able to increase the voltage VERY slightly on the heaters but if you go too far, they will pop and the thing becomes useless.

A few extra turns on the transformer wired in series antiphase to the PRIMARY will up the secondary voltage a little and increase the emission of the heaters. It should also increase the anode-cathode voltage which will also help.

If you have access to a variac then you can use that to experiment with first to see if there is a useful effect.

[The Natural Philosopher]

If its fixitorchuckit this is what someone has reported

"The filament oxidizes which reduces the number of electrons that can be emitted at the same drive current. Driving it with higher current (constant current power supply is necessary) to white hot condition for

5-10 seconds will breathe new life into the display. It's unlikely that the phosphors are damaged if the whole display is dim. You might find a few "shapes" such as a leading zero or the decimal will be permanently dimmed, but an overall rejuvenation will minimize brightness differences.

It's not a permanent solution, but it does give you a few years. I did it to both of my bedside clocks and they've managed to look good for almost four years of 24/7 operation."

[Huge]

Heaters?!?!? Do you imagine this thing has valves in it? Or are you just taking the piss?

[The Natural Philosopher]

Oh dear

Poor old Huge. No wonder he is a remoaner. He might not be able to live without an EU to wipe his botty.

[Brian Gaff]

Bit like us humans then really! Brian

[Andrew Gabriel]

I've got one of those - probably 20 years old, although never needed to look inside it as yet.

There's a brighness high/low switch on the back. Yours hasn't got knocked to low, or stuck on low regardless of setting, has it?

Display is a vacuum fluorescent tube, and these do dim over time due to the phosphor wearing out, and the cathode wire emission coating reducing in efficiency. There are things that can be done to improve brightness, lookup Vacuum fluorescent display rejuvenation. Also, if not used for a long time, it may require a few days to return to normal brightness.

Another problem could be the tube supply - they normally have a separate supply due to requiring higher voltage than the radio circuitry. You might find a smoothing capacitor has died and is pulling the voltage down.

[Brian Gaff]

Yes well, there are so many ways these things work. I thought most were cold cathode and the problem was jointly low emission from the cathode and Ion poisoning of the phosphor itself. back in the old days of CRTs they used to fire electron beams at the side of the tube then bend them back using a magnet, but the ions being heavier, went straight out the side and hence did not damage the phosphor as much long term. Brian

[Brian Gaff]

No its cold cathode if its like the Casio devices. Its still glass though and has anodes and cathodes etc. its very like the cells in old Plasma TVS on a smaller scale. Brian

[Brian Gaff]

There are obviously at least two technologies here. Do we know which one Sony used?

Either way pollution of the cathode was always an issue. Whether it was oxide or not I can only guess, sounds like they have not been evacuated well enough if it is. Like I say some do have false segments lit if you up the volts. The burning off of the cathode in the way you describe is the same system we used to use in CRT rejuvenators back in the day, when overheating of the cathode with special current limiting and some had inverted anode volts to, which could for example get a tube to work for a couple of years more. Certainly some colour tubes could get the guns rebalanced to within adjustment range doing this. The question was, was it really cost effective when labour costs started to climb. Brian

[tabbypurr]

If it's a VFD display, typically a light blue-green but sometimes other colours, there are several ways to improve output.

1. Raise anode voltage. They tend to get run around 30v, I've happily run them upto what was it, 150 or 180v I think. This is one of the easier fixes.
2. Increase filament voltage/current slightly. Others have mentioned other approaches.

If it's another type of display, different story.

NT

[Graham Harrison]

Mine must be slightly later. The min/max switch isn't a switch, it's a button and it works in a circular fashion - each press makes it brighter until, at maximum, the next press takes it to minimum and you start again!

[DerbyBorn]

[e-mail] (Andrew Gabriel) wrote in news:phq5as$ss8$ [e-mail]:

Not seen a switch. More like 30 years old.

[DerbyBorn]

[e-mail] wrote in news: [e-mail]:

The fixes are beyond me - any experience of ones that project onto the ceiling?

[Andrew Gabriel]

Actually, mine must be older than 20 years - had it in my previous place. Just inspected it for a date. Couldn't see one, but the backup battery in it says use by Feb 98 (and still works), so probably 25 years old.

[Andrew Gabriel]

The very few I've seen are not very bright, and I doubt could be read in my bedroom in the morning at this time of year. Possibly not suitable if you are short sighted either.

[Harry Bloomfield]

Huge submitted this idea :

They have heaters in, they are valves.