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 Post subject: Tubes getting very hot in Hallicrafters S-40A radio
PostPosted: May Tue 07, 2019 2:54 pm 
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In a previous post a gentleman mentioned that the 5Y3 and 6F6 tubes of this S-40A radio will run very hot and the others should be warm. I am looking up in the RCA tube manual to determine some kind of maximum shell temperature for these tubes that are all in metal cases. One of them burned the tip of my finger by me barely touching it.

Is there a way I can use my infrared thermometer or the temperature probe from my multimeter to determine what is the maximum temperature I should see on these tubes? They seem very very hot to me. Thanks.


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 Post subject: Re: Tubes getting very hot in Hallicrafters S-40A radio
PostPosted: May Tue 07, 2019 7:29 pm 
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Audio output tubes and rectifiers certainly run very hot and yes, can burn your fingers. Some malfunction could maybe cause them to be even hotter than typical but that would imply that there is a perceptible problem with the radio. IF it works good then you just have to keep your fingers out of the radio till it cools off.

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 Post subject: Re: Tubes getting very hot in Hallicrafters S-40A radio
PostPosted: May Tue 07, 2019 8:02 pm 
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Here is a beam power tube used in TV sweep circuits and ham transmitters.

https://frank.pocnet.net/sheets/123/6/6JS6C.pdf

Bulb temp is 225 C! Power tubes can easily reach 150 C or more, so don't touch!

Rich


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 Post subject: Re: Tubes getting very hot in Hallicrafters S-40A radio
PostPosted: May Tue 07, 2019 8:02 pm 
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Thank you Wazz!


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 Post subject: Re: Tubes getting very hot in Hallicrafters S-40A radio
PostPosted: May Tue 07, 2019 8:06 pm 
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Thank you Rich! Thats really interesting.


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 Post subject: Re: Tubes getting very hot in Hallicrafters S-40A radio
PostPosted: May Fri 10, 2019 4:00 am 
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Greetings to the Forum:

I remember seeing a 6JE6 or 6JS6 or similar tube (don't recall the exact type anymore) that had a thumb-sized dent in the glass where it had been pushed in until it almost touched the plate structure. This tube had gotten hot enough to melt the glass and the pressure differential between the ambient air and the vacuum inside pushed it in.

IMHO, this is running a bit TOO warm. :D

Regards,

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 Post subject: Re: Tubes getting very hot in Hallicrafters S-40A radio
PostPosted: May Fri 10, 2019 1:02 pm 
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Jthorusen wrote:
Greetings to the Forum:

I remember seeing a 6JE6 or 6JS6 or similar tube (don't recall the exact type anymore) that had a thumb-sized dent in the glass where it had been pushed in until it almost touched the plate structure. This tube had gotten hot enough to melt the glass and the pressure differential between the ambient air and the vacuum inside pushed it in.

IMHO, this is running a bit TOO warm. :D

Regards,

Yes sir.

I once pulled a 6JE6 that had gone to air, there was a 1/8" hole sucked into glass. No doubt cooled off when set tripped the circuit breaker. :lol:

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 Post subject: Re: Tubes getting very hot in Hallicrafters S-40A radio
PostPosted: May Sat 11, 2019 3:44 am 
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I've seen both a hole in the side of a tube like 35Z5 had and a dent like Jthorusen has seen. Both were horizontal sweep tubes that had lost their drive signal. 6CD6's or 6BQ6's, I think. The 6CD6 has a rated maximum bulb temperature of 225°C while the 6BQ6 is 220°C.
John

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 Post subject: Re: Tubes getting very hot in Hallicrafters S-40A radio
PostPosted: May Sat 11, 2019 6:57 am 
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Interesting! Where do you find those maximum temperature readings listed? thanks.


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 Post subject: Re: Tubes getting very hot in Hallicrafters S-40A radio
PostPosted: May Sat 11, 2019 5:31 pm 
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Bulb temperatures are given on data sheets for some power tubes, especially those used in transmitters.

Some of the old tube manuals also had sections on tube construction and operating conditions.

Rich


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 Post subject: Re: Tubes getting very hot in Hallicrafters S-40A radio
PostPosted: May Sat 11, 2019 9:10 pm 
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Thanks Rich! I'm going to look a few tubes up!


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 Post subject: Re: Tubes getting very hot in Hallicrafters S-40A radio
PostPosted: May Sat 11, 2019 10:49 pm 
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Not all of the tube types have that information, not even "power" tubes, but the maximum bulb temperature for both of the following tubes is on page 2 of their data sheets. It'll give you some idea of how it's listed.

Data sheet for the 6CD6GA: http://www.tubebooks.org/tubedata/hb-3/ ... CD6-GA.PDF
Data sheet for the 6BQ6GTB/6CU6: http://www.tubebooks.org/tubedata/hb-3/ ... B_6CU6.PDF

John

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 Post subject: Re: Tubes getting very hot in Hallicrafters S-40A radio
PostPosted: May Sun 12, 2019 8:01 am 
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Yes! I looked at both of the data sheets at the bulb temperatures. I understand now by also looking up tubes that I’m working with i.e. 6F6 that this information is not always listed. I’m wondering if I can do that myself for the tubes I’m working with in this radio. Once I know the set is working correctly and I’m comfortable with it, perhaps I could take these readings and keep them for reference. Makes sense? Thanks.


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