Changing pilot lamps on HRO-50

[EI4CB]

I need to replace one of the two pilot lamps that illuminate the slide-rule dial of a HRO-50.  It is not obvious how to do it at either end, without a lot of trouble  As far as I can see, one needs to remove all the knobs from the front panel, including the main micrometer tuning dial, then remove the screws needed to move the main aluminum chassis back at least an inch or two inside the steel cabinet.  I can't help thinking that replacing a burned-out pilot lamp cannot be this complicated!  On most receivers, it is as simple as swapping a tube.  I must be overlooking an easier way to do it.  Please set me straight.

   Dec

[w3jn]

I moved your topic here where it'll get more exposure.  The Receivers forum is for completed articles.

Regarding your question, my HRO-60 is 6000 miles away but as I recall you remove one or two of the plastic dial scales (one screw each and then they unsnap) and that gives you access to the bulbs.  It's best not to run 'em with the dimmer cranked up to full strap - running them a bit dimmer will prolong their life considerably.

[k4kyv]

I run the 12-14v equivalents of the 6.3 volt pilot lamps in my 75A-4.  Not only do they give a warm amber glow instead of the harsh white light from the originals, the bulbs seem to last for ever.  I think the present set in mine are at least 10 years old and still going strong.  With the dimmer control on the HRO-50/60, maybe you  could just keep the stock bulbs and run them on dim.

[WQ9E]

To change the lamps you need to remove the dial scale drum which is a quick and simple process.  Behind the oscillator control you will see a small wheel that when pushed towards the panel allows the scale to slide towards the right side of the receiver.  This will free the drum and it can be angled out and removed.  Once removed you have fairly easy access to the lamps.  Reverse process to re-install.

Like JN said, use a little dimming.  As I recall just a few percent reduction in voltage more than triples the lamp life.

If you want a hard dial lamp to change, try the HRO-500

[w3jn]

...or certain models of the R-1051!

That's it, Rodger.  Yep, the dial drum just kind of snaps in on the one end.... it's all coming back to me now 

[WQ9E]

It comes back even faster when you can pop open the lid and look at the receiver   You just need to carry more of your collection with you.

I don't have any experience with the R-1051.... YET.

...or certain models of the R-1051!

That's it, Rodger.  Yep, the dial drum just kind of snaps in on the one end.... it's all coming back to me now 

[w3jn]

It's one of those that's not worth bothering with, Rodger 

[WQ9E]

JN,

The R-1051 HAS to be better than the lousiest shortwave set ever made, my American Electrola DXC-100.  It sounds lousy on FM and it has more spurs than real signals on the BCB and SW ranges.  It displays itself as proudly made in the USA and has a genuine fake wooden case.  Its only redeeming characteristic is the clock works pretty well.

[w3jn]

It's a good performer, but a giant PITA to tune around with those decade switches.  Get a working one, because fixing it's a real challenge.

[KM1H]

The HRO-500 lamps are fairly easy to replace since you probably have the damn thing half apart to align the VFO; what a stupid place to put the adjustment! I add an under chassis resistor to drop the lamp voltage down a bit in mine and all the ones that come in for overhaul.

Carl

[Pete, WA2CWA]

I've changed the dial lights in my HRO-500 in the past, but have yet to change the front panel frequency pointer lamp. I have no ambition to disassemble of the stuff to get to it.

[EI4CB]

To change the lamps you need to remove the dial scale drum which is a quick and simple process.  Behind the oscillator control you will see a small wheel that when pushed towards the panel allows the scale to slide towards the right side of the receiver.  This will free the drum and it can be angled out and removed.  Once removed you have fairly easy access to the lamps.  Reverse process to re-install.

Like JN said, use a little dimming.  As I recall just a few percent reduction in voltage more than triples the lamp life.

If you want a hard dial lamp to change, try the HRO-500

Many thanks for this tip.  Originally, I started to remove the drum and incorrectly got the impression that I still would not be able to get my fingers around the pilot lamp.  When I tried again after reading your explanation, it all worked out fine.  Thanks again!

[w3jn]

Great, glad it worked out!

And welcome to AMFone, by the way 

[ashart]

Regarding the increase in bulb life allowed by reduced voltage - I always thought that I could win bar bets with this piece of trivia, but I didn't go to many bars, so I never won any free drinks.

However, I recall reading a hundred years ago that the life of an incandescent filament was inversely proportional to the fifth power of the bulb current.

If true, running on half current would give a lamp life of 32 times normal!

al hart
w8vr

[KM1H]

Being rather lazy and finding bulb changing a royal PITA in way too many sets I simply reduce the voltage a bit in just about everything I work on. Having plenty of otherwise useless low value 2-5W WW resistors its a simple task.

Carl