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 Post subject: "Flash" on top grid of 1176GT tube ?
PostPosted: Jan Wed 11, 2017 6:49 pm 
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I have never seen this happen before...upon turning on radio while testing a chassis,
the 1176GT tube "flashed" brightly on it's top grid. I can't test the tube at the moment,
and the radio has other issues as well as not working...sooo... What say you? :wink:

When things exceed my knowledge base, I just 'move on' to another unfinished project. :roll:

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 Post subject: Re: "Flash" on top grid of 1176GT tube ?
PostPosted: Jan Wed 11, 2017 6:55 pm 
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Never heard of a 1176GT tube-what is it,a rectifier?Ballast?
Phil

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 Post subject: Re: "Flash" on top grid of 1176GT tube ?
PostPosted: Jan Wed 11, 2017 7:11 pm 
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Philco Fan wrote:
Never heard of a 1176GT tube-what is it,a rectifier?Ballast?
Phil

Thanks, Phil...I have to run out the door right now...I will get back to you!

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 Post subject: Re: "Flash" on top grid of 1176GT tube ?
PostPosted: Jan Wed 11, 2017 7:23 pm 
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Location: Rockford IL USA
Probably a 117Z6GT--not unusual to see the heaters flash at turn-on and appear to extend further than the cathode sleeve, particularly if sublimation is present.


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 Post subject: Re: "Flash" on top grid of 1176GT tube ?
PostPosted: Jan Wed 11, 2017 7:43 pm 
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A 117Z6 is a rectifier, has no grid...

Yes they do sometimes exhibit heater flash at turn on, there's a 117Z4 around here that does same...


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 Post subject: Re: "Flash" on top grid of 1176GT tube ?
PostPosted: Jan Wed 11, 2017 8:44 pm 
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Yes, the 117Z6GT can flash at turn in. It can happen with any tube but it's usually seen in ones with high voltage filaments. I don't like it but never had one burn out from this.

This is more common in European tubes, even with 12 volt filaments.

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 Post subject: Re: "Flash" on top grid of 1176GT tube ?
PostPosted: Jan Thu 12, 2017 1:38 am 
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Location: Vancouver Island, Canada
Yeah if it's just your sublimated rectum fryer? Not a problem then.
:lol:
It sounds like a bucking transformer or thermistor would help, but only if this radio gets turned on and off more than a few times a year.

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 Post subject: Re: "Flash" on top grid of 1176GT tube ?
PostPosted: Jan Thu 12, 2017 2:38 am 
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This is normal for some tubes, they are not defective, they will last a long time, No sense in trying to fix something that is not broken.

Dave


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 Post subject: Re: "Flash" on top grid of 1176GT tube ?
PostPosted: Jan Thu 12, 2017 8:06 am 
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I shorted one once between the cathode and plate, those suckers start to incandesce when they red plate.

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 Post subject: Re: "Flash" on top grid of 1176GT tube ?
PostPosted: Jan Thu 12, 2017 9:00 pm 
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Philco Fan wrote:
Never heard of a 1176GT tube-what is it,a rectifier?Ballast?
Phil

Sorry for the delay... :oops:

Well, looks like all you guys that responded have figured it out- sooo.."OK", Good.
Yes! That's it! It is a "117Z6GT" rectifier...what does the GT indicate? ...
and don't say: "Grand Touring".

Thank you All! :)

westcoastjohn: "A sublimated rectum fryer?"
Yes...I can get that after some Jalapenos! :lol:

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 Post subject: Re: "Flash" on top grid of 1176GT tube ?
PostPosted: Jan Thu 12, 2017 10:43 pm 
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Glass tubular.
Scott


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 Post subject: Re: "Flash" on top grid of 1176GT tube ?
PostPosted: Jan Thu 12, 2017 10:48 pm 
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Location: Cleona, PA
GT = "glass, tubular," the typical "bantam" octal tube. G = "glass," indicates the ST style "coke bottle" tubes. These codes are appended to the metal tube designations to indicate the alternate envelopes.

I have seen the heaters of a 117L7GT combo rectifier/power output tube squirm at startup as they react to magnetic and thermal forces. That's a lot of heat and activity going on in a small package.

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 Post subject: Re: "Flash" on top grid of 1176GT tube ?
PostPosted: Jan Fri 13, 2017 2:43 am 
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Joined: Dec Sat 24, 2011 9:17 pm
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Location: Vancouver Island, Canada
Right, the filament is rated for 117 volts, line voltage, and that can be 120+ volts these days.
Like a miniature toaster in your radio.

That tube is used to power portable radios. Also it can get hot enough to melt plastic, so be careful.

I found a pic of a 117Z... in a 1950 Emerson 646B portable. Posted here just for fun, it is the tall 7-pin tube on the left.


Attachments:
Emers646B.jpg
Emers646B.jpg [ 70.44 KiB | Viewed 177 times ]

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Last edited by westcoastjohn on Jan Fri 13, 2017 4:51 am, edited 1 time in total.
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 Post subject: Re: "Flash" on top grid of 1176GT tube ?
PostPosted: Jan Fri 13, 2017 4:42 am 
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Tubes generally have a +/-10% voltage rating, meaning it can operate from 105 to almost 129v...

The tubes used in car radios were subject to wide variations in voltage, no one worries about those(no I can't name any that were 117v :shock: )...


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 Post subject: Re: "Flash" on top grid of 1176GT tube ?
PostPosted: Jan Fri 13, 2017 6:32 am 
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As 35Z5 said these 117 volt rectifiers can and do get hot, but that is just part of their operation, and their life will not be dramatically shortened by being over a few volts on the filament. Remember a filament is just a piece of metal, it can't count and doesn't care about figures.

BTW, I want to correct something that I have heard come up when discussing the 177Z6 or 117Z3 tubes. I have heard people say that they were designed to take up the excess voltage in the filament string so the radio can be run on AC current. This is false. The battery tubes common in radios that use a 117Z6 or 117Z3 have no cathodes and cannot be run on AC, thus the filament of the 177 volt tube s the only thing running off of the AC current while the other tube get their filament voltage from the rectified B+ line.

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 Post subject: Re: "Flash" on top grid of 1176GT tube ?
PostPosted: Jan Sat 14, 2017 3:29 pm 
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Location: Vulcan Michigan
The flash at startup is normal for my Zenith Universal, (aluminum case). The heat produced from the rectifier comes in handy for me in the cold northern Michigan winter....my daily driver.....


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IMG_20170114_082122832-240x427.jpg [ 38.78 KiB | Viewed 126 times ]
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 Post subject: Re: "Flash" on top grid of 1176GT tube ?
PostPosted: Jan Sat 14, 2017 5:46 pm 
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Not sure why there seems to be a sudden concern of the heat from a rectifier, yes they get hot... No different than 35Z5 or peanut 35W4 that because it's likely supplying 2, 3 or even 4x the amount of current, is several degrees hotter than a 117Z3... The 117Z6 is a full wave rectifier, still because battery radio current requirements are small it isn't likely to be any hotter than 35Z5... You want hot, A 117L7 that includes audio output drawing 40ish ma and the rectifier supplying probably 50 ma is going to be hot... Want really hot?? Try a 5U4 supplying 200ma...


Tom


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