[AMRadio] Grounded grid amp

[John Coleman]

I have heard of guys doing that suppressor grid mod. For GG ops. But for
class B zero bias audio I drove the screens direct and had an 18K res from
screen to grid.  I thought that was a little weird but it was recommended by
RCA on the 807s so I did it on the 1625s.  There was a paper published about
this type of class B work with the 807s. and it was in the operation
descriptions in the ARRL handbook for 807s or 1625s.  For whatever reason
RCA did some extensive testing for this type of service.  I think it was
because some folks had very good luck with the 6L6s grid and screen tied
together and where not have good luck with the 807 that way.  There seemed
to be a distortion anomaly and putting the 20K resistor between the screen
and grid then driving the screen made it smooth.

John  

-----Original Message-----
From: amradio-bounces at mailman.qth.net
[mailto:amradio-bounces at mailman.qth.net] On Behalf Of Bernie Doran
Sent: Wednesday, January 26, 2011 11:50 AM
To: W9RAN at oneradio.net; Discussion of AM Radio in the Amateur Service
Subject: Re: [AMRadio] Grounded grid amp

I recall 1625s also had the suppressor/beam forming plates connected to the 
cathode. one could cut into the base from the side and reconnect that lead 
to an unused pin. that would be a little difficult with internal connection.
----- Original Message ----- 
From: "Robert Nickels" <ranickel at comcast.net>
To: <amradio at mailman.qth.net>
Sent: Wednesday, January 26, 2011 12:14 PM
Subject: Re: [AMRadio] Grounded grid amp


> On 1/26/2011 11:03 AM, David Folger wrote:
>> he 6DQ5 is cheap and easy to come by.
> I love the 6DQ5, best SSB final tube made IMHO.   My GSB-1 and Swan 240
> amaze me with what a single DQ5 final will do - 150 watts PEP or more.
> Someone has posted a nice little class AB1 linear here:
> http://www.scribd.com/doc/39134100/Linear-100w-6dq5
>
> Unfortunately, the 6DQ5 won't do grounded-grid since the suppressor grid
> is internally connected to the cathode.
>
> 73, Bob W9RAN
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