[Hallicrafters] SX28 hot & blue 6V6s

[Richard Knoppow]

    Well I agree with Carl that the grid coupling caps could 
also be bad. I had not thought of that at first because 
_both_ tubes are overheating but both caps could be bad.
     I am pretty sure the SX-28 manual has a chart of tube 
socket voltages. When using it see if it specifies the type 
of meter to be used. A lot of older equipment has voltages 
measured with a 1000 ohm/volt meter and a more modern 20,000 
ohm/volt meter or electronic voltmeter will read high for 
some measurements.
     Another thing to look for is color on the plates. You 
may have to look in the dark but the plates of normally 
operating tubes of this sort should show no color. If there 
is any red glow it indicates the plate current is too high, 
a sign that something is wrong.


--
Richard Knoppow
Los Angeles
WB6KBL
dickburk at ix.netcom.com


----- Original Message ----- 
From: "Guido" <laffitte at prtc.net>
To: <hallicrafters at mailman.qth.net>
Sent: Thursday, August 25, 2011 6:51 PM
Subject: Re: [Hallicrafters] SX28 hot & blue 6V6s


> The responses indicate that a complete 6V6s circuit 
> component checkup is
> coming up. The monster must come out of the cage yet 
> again. Let me see if I
> have enough time this weekend. I will report the findings. 
> Thanks guys!
>
> 73s
>
> Guido KP4FAR
>
> -----Original Message----- 
> From: Carl
> Sent: Thursday, August 25, 2011 9:22 PM
> To: Guido ; hallicrafters at mailman.qth.net
> Subject: Re: [Hallicrafters] SX28 hot & blue 6V6s
>
> Likely leaky input coupling caps putting some positive 
> bias on the grids.
> That will also take out the transformer.
>
> Carl
> KM1H
>
>
> ----- Original Message ----- 
> From: "Guido" <laffitte at prtc.net>
> To: <hallicrafters at mailman.qth.net>
> Sent: Thursday, August 25, 2011 8:40 PM
> Subject: [Hallicrafters] SX28 hot & blue 6V6s
>
>
>> Gents,
>>
>>  It has been a while since my last post but I keep a 
>> daily track of this
>> list. My SX28 had its first audio transformer replacement 
>> about two years
>> ago with two new audio tubes. These are running hot and 
>> with a clear all
>> around bluish glow. They run too hot and I don’t think 
>> this is normal
>> although we know that 6V6s tend to run with some extra 
>> heat but not this
>> much. I am sure that this has been discussed before but 
>> either I missed it
>> or my almost 59 years neurons are being depleted. 
>> Opinions will be
>> appreciated.
>>
>> Best 73s
>>
>> Guido KP4FAR
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