Only mod was V bias to R bias. At key down, there is 7.5V at the zener.
Maybe I should do the diode bias or get a 5.1V zener, or maybe just the old
tubes are a little soft
On Fri, Feb 12, 2010 at 10:38 AM, Carl <km1h@jeremy.mv.com> wrote:
> Did you modify the bias circuit or check the voltage?
>
> Carl
>
>
>
> ----- Original Message -----
> *From:* Tom Prohigh <tomp@prohigh.com>
> *To:* Carl <km1h@jeremy.mv.com>
> *Cc:* amps@contesting.com
> *Sent:* Friday, February 12, 2010 10:34 AM
> *Subject:* Re: [Amps] TL-922 voltage / bias
>
> There are 2 tubes in the TL-922. The grids are DIRECTLY connected to
> ground, I removed the caps and chokes and also put in a second ground wire
> from VC1. This eliminated some arcing/parasitics I was having. The tubes
> are original Eimac 3-500Z not 3-500ZG. The color on the plates is fine, no
> color at idle and red/orange at full drive. I do get about 600-700W out on
> CW, but only about 1000 key down on SSB on 20M. 80M is somewhat higher
>
> Tom - AB3FL
>
> On Fri, Feb 12, 2010 at 10:30 AM, Carl <km1h@jeremy.mv.com> wrote:
>
>> That idle current is fine for 1 tube and the voltage drop is excessive.
>> Start by measuring the grid chokes for an open or looking for color on both
>> plates.
>>
>> Carl
>> KM1H
>>
>>
>> ----- Original Message ----- From: "Tom Prohigh" <tomp@prohigh.com>
>> To: <amps@contesting.com>
>> Sent: Friday, February 12, 2010 9:47 AM
>>
>> Subject: [Amps] TL-922 voltage / bias
>>
>>
>> I have recently aquired a TL-922. It is on a stiff 240V line which
>>> actually
>>> measures 245V. No load voltage on CW is 2200 and on SSB is 3100. Under
>>> full load the CW drops to 1900V @ 600ma and the SSB drops to 2400V @
>>> 800ma.
>>> Is there really suppose to be this much drop? It has the original 200uf
>>> caps in it and I was thinking about replacing them with 560uf units.
>>> Also
>>> the grid bias on CW is 60ma and on SSB 120ma which seems a little low.
>>>
>>>
>>> thanks
>>>
>>> Tom - AB3FL
>>> _______________________________________________
>>> Amps mailing list
>>> Amps@contesting.com
>>> http://lists.contesting.com/mailman/listinfo/amps
>>>
>>
>>
>
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