[Amps] Amps Digest, Vol 244, Issue 3

Sat Apr 1 22:35:47 EDT 2023

5 Volts times 10 Amps equals 50 Watts.  Assuming your measurements are
correct, something in that tube is producing 50 Watts worth of heat.  That
is not a great of deal of heat, about 20% less than an old fashioned
incandescent light bulb.  If you have air blowing on it, that may be enough
cooling to reduce the apparent warming of the tube to very little above
ambient.  Try turning off the cooling fan or somehow blocking the air flow
for a short time and see if the tube gets warmer.  If so I would say
everything is OK.
Bob W4AOS

On Sat, Apr 1, 2023 at 10:06 PM <amps-request at contesting.com> wrote:

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> Today's Topics:
>
>    1. 8877 filament (Bob Gibson)
>    2. Re: 8877 filament (Ron W4BIN)
>    3. Re: 8877 filament (Bob Gibson)
>    4. Re: 8877 filament (Steven Katz)
>    5. Re: 8877 filament (gudguyham at aol.com)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Sat, 1 Apr 2023 18:44:07 +0000 (UTC)
> From: Bob Gibson <w5rg at yahoo.com>
> To: "Amps at contesting.com" <Amps at contesting.com>
> Subject: [Amps] 8877 filament
> Message-ID: <1926159074.2171456.1680374647976 at mail.yahoo.com>
> Content-Type: text/plain; charset=UTF-8
>
> What would cause the filament not to get hot if there is continuity
> between the pins when 5 volts is applied? The tube has been sitting for
> seven or eight years. Bob
>
> Sent from Yahoo Mail on Android
>
> ------------------------------
>
> Message: 2
> Date: Sat, 1 Apr 2023 16:28:04 -0400
> From: Ron W4BIN <ka4inm at gmail.com>
> To: amp <amps at contesting.com>
> Subject: Re: [Amps] 8877 filament
> Message-ID: <0bbaa747-a5e5-f65d-0c4c-cf6c4232d445 at gmail.com>
> Content-Type: text/plain; charset=utf-8; format=flowed
>
> Bob Gibson via Amps wrote:
>
> > What would cause the filament not to get hot if there is continuity
> between the pins when 5 volts is applied? The tube has been sitting for
> seven or eight years.
> > Bob
>
>  ? Measure the filament current.
> --
>
>
> ------------------------------
>
> Message: 3
> Date: Sat, 1 Apr 2023 20:54:30 +0000 (UTC)
> From: Bob Gibson <w5rg at yahoo.com>
> To: amp <amps at contesting.com>, Ron W4BIN <ka4inm at gmail.com>
> Subject: Re: [Amps] 8877 filament
> Message-ID: <686431508.2196774.1680382470634 at mail.yahoo.com>
> Content-Type: text/plain; charset=UTF-8
>
> The voltage and current are right on..I plugged one of my tubes into same
> socket and tube heats up fine.. This other tube has a code date of 89 and
> has YU158 and 3cx1500a7 on it. Anyway I sent the tube back to my friend but
> I would like to know why it would not heat up..
>
> ?? 73s Bob W5RG
>
>
>     On Saturday, April 1, 2023 at 03:28:14 PM CDT, Ron W4BIN <
> ka4inm at gmail.com> wrote:
>
>  Bob Gibson via Amps wrote:
>
> > What would cause the filament not to get hot if there is continuity
> between the pins when 5 volts is applied? The tube has been sitting for
> seven or eight years.
> > Bob
>
>  ? Measure the filament current.
> --
> _______________________________________________
> Amps mailing list
> Amps at contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>
>
> ------------------------------
>
> Message: 4
> Date: Sat, 1 Apr 2023 21:00:50 +0000
> From: Steven Katz <stevek at jmr.com>
> To: Bob Gibson <w5rg at yahoo.com>, amp <amps at contesting.com>, Ron W4BIN
>         <ka4inm at gmail.com>
> Subject: Re: [Amps] 8877 filament
> Message-ID:
>         <
> BY5PR16MB4002D6FE200B979B24C8DD50DA8C9 at BY5PR16MB4002.namprd16.prod.outlook.com
> >
>
> Content-Type: text/plain; charset="utf-8"
>
> How could the current be right on (5V @ 10A) and the tube heater not work?
>
> I've used lots of 8877s and (B+ removed!) if you feel the tube with the
> heater only on but the blower running, they're cool to the touch and don't
> get hot at all.   In my experience, not even really warm.   It's only 50
> watts, far away from the external anode with a vacuum in between.   The
> only thing that normally gets slightly warm is the heater pins at the
> socket.
>
> -----Original Message-----
> From: Amps <amps-bounces at contesting.com> On Behalf Of Bob Gibson via Amps
> Sent: Saturday, April 1, 2023 3:55 PM
> To: amp <amps at contesting.com>; Ron W4BIN <ka4inm at gmail.com>
> Subject: Re: [Amps] 8877 filament
>
> The voltage and current are right on..I plugged one of my tubes into same
> socket and tube heats up fine.. This other tube has a code date of 89 and
> has YU158 and 3cx1500a7 on it. Anyway I sent the tube back to my friend but
> I would like to know why it would not heat up..
>
> ?? 73s Bob W5RG
>
>
>     On Saturday, April 1, 2023 at 03:28:14 PM CDT, Ron W4BIN <
> ka4inm at gmail.com> wrote:
>
>  Bob Gibson via Amps wrote:
>
> > What would cause the filament not to get hot if there is continuity
> between the pins when 5 volts is applied? The tube has been sitting for
> seven or eight years.
> > Bob
>
>  ? Measure the filament current.
> --
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>
> ------------------------------
>
> Message: 5
> Date: Sun, 2 Apr 2023 02:05:49 +0000 (UTC)
> From: "gudguyham at aol.com" <gudguyham at aol.com>
> To: Ron W4BIN <ka4inm at gmail.com>, amp <amps at contesting.com>
> Subject: Re: [Amps] 8877 filament
> Message-ID: <1712121102.2228041.1680401149666 at mail.yahoo.com>
> Content-Type: text/plain; charset=UTF-8
>
> Filaments move when they get hot from expansion that means the filament
> could open up when hot. ?Rare but I suppose possible.
>
>
> Sent from the all new AOL app for iOS
>
>
> On Saturday, April 1, 2023, 4:28 PM, Ron W4BIN <ka4inm at gmail.com> wrote:
>
> Bob Gibson via Amps wrote:
>
> > What would cause the filament not to get hot if there is continuity
> between the pins when 5 volts is applied? The tube has been sitting for
> seven or eight years.
> > Bob
>
>  ? Measure the filament current.
> --
> _______________________________________________
> Amps mailing list
> Amps at contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>
>
>
>
>
> ------------------------------
>
> Subject: Digest Footer
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> ------------------------------
>
> End of Amps Digest, Vol 244, Issue 3
> ************************************
>