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This topic has strayed a long way from "A Noisy Pilot Light". There is a lot of good information here that no one will find in the future unless the topic is corrected.

Bob, AF6C?

?=========trimmed a bit

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Don,

The downside of aging, LOL
I bought the caster thingie from Harbor Frieght and cut off the vertical handles, works well, cheap too.
Cheers,

Randy?
W7CPA

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SX-101A, HT-32B, updated HT-33A with 8295, 400v screen, blower speed control and solid state rectifiers.

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From Don:

On Sun, Oct 2, 2022 at 10:28 PM, Cal Fuhrman - WA3CTZ

<calfuhrman7@...> wrote:

Chuck, have you tried Novus-2?? Last Summer I started restoration on a Hallicrafters HT-41 and the meter face was indescribably ugly.? I used Novus-2 and copious elbow grease and now you can’t tell it from a new one.? Two years ago I restored a Williams Laser Que pinball machine.? It is loaded with various large & small plastic items and I cleaned & polished all of them with Novus-2.? That effort was a total success but there is no magic and it takes a lot of rubbing to get the clear appearance that a new piece has.

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I have before/after pics but they are at the Florida QTH.? If I remember, I’ll send them next week when I get back there.

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Cal – WA3CTZ

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From: chuckbell1952 via groups.io
Sent: Sunday, October 2, 2022 8:12 PM
To: [email protected]
Subject: [HallicraftersRadios] Hallicrafters HT32a

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Hello all. I am still looking for a meter bezel for my HT32A. The one I have has swirls in the plastic that I have tried to buff out but with no success. If someone out there has a parts radio with a good meter bezel let me know. It of course does not effect the operation of the rig but it's just a cosmetic issue I would like to correct. Thanks

Chuck

K3HHP?

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Don,

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So in support of your comments regarding overall protection, for the SX-100 I am currently working on, I have had to replace the 2 conductor AC cord with a 3 conductor so that the chassis now has a safety ground.? There is no original main fuse within that radio, so you are spot on regarding the 15A CB for the AC circuit being used to power the radio as the only thing to stop an runaway overcurrent situation.? You are absolutely correct in that the transformer will probably fail over before the 15A CB actually trips.? I have been looking for a spot on the back of the deck that has the space internally that can support an externally accessible 3AG panel mount fuse holder.? And you are right again, this particular radio draws 88W of power which is roughly 0.704 Amps at the AC line right that comes into the house.? Although, I suspect the inrush current when the radio is first turned on is roughly an amp.? So I will start out with a 1.5 Amp fast blow fuse and see how that works.? That is a much better option than waiting for a possible run away scenario to take out the transformer long before the 15A CB hopefully trips.

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Thank you,

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Mike

W5CUL? ???

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Hi once more Mike

I think we mostly agree on the first paragraph and should let it go.

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Yes to much of paragraph 2, but I think you can extend that to virtually all old radios with power transformers.

On the last part, I see it as a fight between the weakness of the transformer? and the weakness of the specific lamp and the way it fails .

Should the transformer win , the tube blows and little else happens, but if [that is an IF] the bulb wins, the transformer slowly cooks on a 15 amp circuit likely resulting in a turn to turn fault , then more current … and if and when the primary has a turn to turn? short , there is a chance the 15 amp circuit will open at the main breaker, but if the secondary has a T-T short,? the primary will boil and you will have a burned out radio and maybe a burned down house. ?

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now shifting from the bulb problem? table radios dram maybe .35 amps? to say .75 for older ones, and larger Hallis likely don’t reach 1 amp, yet they are connected to a 15 amp breaker {for any one from over one of the ponds, I am speaking of the usual North American situation where we generally use 120 Volts and 15 amp breakers in houses}, so the breaker provides no protection for the transformer. I my opinion it is criminal that the standards and regulators allow the radios to be sold without over-current protection.

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Isn’t it strange that the RT-524 ?has protection, but consumers get none.

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I better quit my rant before i boil over too,? but i’m not done about that topic. ?

Sorry for hogging so much space.

Don VA3DLR

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Hey Don,

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That happened so many years ago in another lifetime for me.? Although, I do recall myself and my Warrant Officer chalking it up as a one in a million manufacturing fluke in regards to the Filament Leads for that particular dial lamp.? We speculated that the filament leads within a manufacturing lot, for which that particular dial lamp was part of, were much larger than normal thus could handle some draw for a longer period of time. Long ?enough for the CB/Power Switch to say no more and trip before that dial lamp went poof.? And yes, I suspect it was considered an improbability for such a failure mode to occur thus no consideration around a preventive design for such.? ??

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If you look at all the Hallicrafters designs regarding their dial lamps, there is no protective circuitry to prevent a Filament Lead short from causing a failure mode in the transformer.? That is because it is expected that once that short occurs, the amperage draw will be so fast and intense that those tiny Filament Leads will burn up thus eliminating the short long before the transformer suffers any damage.?

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Thank you,

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Mike

W5CUL

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Hi again Mike

?I agree with your comments, and was not suggesting that you said anything wrong, but I was hoping for some response to my previous comment/question on why did the “switch” trip due to a simple bulb failure?? Was it intentionally designed to do that, or an oversight, or accepted as an unlikely event that had a tolerable probability of not happening I know we can’t generate any solid answer to the question, but we can think about it.?? However, if we do not know all the design criteria of something, it is tough to predict all the failure mechanisms, and so might be very tough to find a problem.

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When I said “fusing”, I felt awkward, I really meant over-current? protection.

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It would seem that most military equipment needs to be tough, and fuses can easily fail and can’t be reset, so are likely not allowed in this equipment, and many [mechanical] circuit breakers can be jarred open by a sudden impact, so can be difficult to produce.?? as an aside the tripping mechanism is/was highly sensitive in older 600 volt power? switchgear, which is certainly not what? we have been speaking of in here.? But one wonders, if we use a spring loaded mechanical contact with some mechanical “trigger PIN?” to release the spring,? just how many G’s can it take before it trips itself.? They must have made some special designs.?

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But, all this is off the point of the real question that you first raised about a few guys not finding the simple problem.? I can sympathize with their dilemma.

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I say: things need to be designed to allow reasonably easy repair, or, as now, throw out, and buy new.

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We should be talking about the original question of what happens when bulbs fail?? I suggest there is more than one answer, all depending on the surrounding circuitry, and, in addition, when the “bulb”? becomes? a LED the question has to be re-evaluated.

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Sorry for wandering around all this.

Don ?VA3DRL

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Hey Don,

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Please do not get me wrong, I agree with your assessment, curiosity and what you have experienced in other similar situations.? I was just pointing out that most everyone was taught that there is no such thing as a shorted lightbulb as the filament leads will end up burning themselves out thus eliminating any dead short that may have been initially incurred.? But when deployed in the right circuit design, or maybe an improper circuit design, it is possible that the filament leads will not experience enough amperage draw to burn themselves out before some other component or subsystem decides enough is enough.

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The issue with fusing any specific circuit in that radio is that an RT-524 is a Military FM Transceiver. Its design was such that it was sealed from the weather as well as designed with minimal external user controls on the faceplate to operate the radio.? It had to be simple to operate for the user and be reliable in all kinds of weather and operating conditions? It also definitely had to be rugged enough to withstand being slammed around by the user in varying combat vehicles. So there were no external facing fuse holders, and the user was not allowed inside of the transceiver, hence just the heavy duty external power switch that was user resettable

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Thank you,

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Mike

W5CUL

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Hi Mike

I guess you are commenting on my first? stuff .

I suggest that our ?typical room lights blow to oblivion, ?partly because they are protected only by a 15 amp breaker or fuse in the main panel of a house, and this allows a very high, short time current to ?burn up any shorting material in the bulb.

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In the case of the RT-524 ?I can only guess that it also has a power transformer that will limit the short circuit current to the bulb giving the

more sensitive ?power switch/ breaker ?time to ?completely open ?the circuit, before the bulb blows.

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This leaves the age old question to fuse or not and where… has a very long answer.

Don ?VA3DRL

????==== ??I trimmed a bunch, so the original situation??? is ?only in some previous posting? --- don

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Hello all. I am still looking for a meter bezel for my HT32A. The one I have has swirls in the plastic that I have tried to buff out but with no success. If someone out there has a parts radio with a good meter bezel let me know. It of course does not effect the operation of the rig but it's just a cosmetic issue I would like to correct. Thanks