[Amps] GU-74b amp by UX1UX

[Roger (K8RI)]

On 8/16/2013 6:12 PM, Louis Parascondola wrote:
> The Chinese have come up with the F-257???? or whatever it is to replace the Russian tubes.  I think Rudy went to them already with Emtron
>

Rudy uses the FU728F instead of the GU84B.  The Chinese FU728F is 
basically a 4CX1500B except it has a different filament voltage and the 
centering pin in the socket is slightly larger than the one for the 
4CX1500B.  Physically the FU728F is quite different than the GU84B so it 
is not a replacement for it.

The FU728F is capable of 2500 PEP and 2KW carrier with the voltages 
supplied. Tune for max screen current without exceeding any of the tubes 
ratings, then back off on the drive a bit (without retuning) to get a 
nice clean signal.

If you run digital or a lot of compression it's likely to kick into high 
blower which is a bit louder.

73

Roger (K8RI)


>
>
> -----Original Message-----
> From: Fortra <fortra at siol.net>
> To: n8de <n8de at thepoint.net>; k3it <gokoyev+k3it at gmail.com>
> Cc: amps <amps at contesting.com>
> Sent: Fri, Aug 16, 2013 6:06 pm
> Subject: Re: [Amps] GU-74b amp by UX1UX
>
>
> Hi Don,
>
> you have probably mixed GU-84B with GU-74b...
> Tube ( s ) in OM-3500 were not GU-74b's...
> Have not had such worries...bought a Dentron MLA-2500B,
> with original tubes :) When they failed we will switch to 3cx800 :)
>
> Rgds,
>
> Nermin S58DX
> ----- Original Message -----
> From: <n8de at thepoint.net>
> To: "k3it" <gokoyev+k3it at gmail.com>
> Cc: <amps at contesting.com>
> Sent: Friday, August 16, 2013 9:54 PM
> Subject: Re: [Amps] GU-74b amp by UX1UX
>
>
>> While attending the Friedrichshafen 'Ham Radio' gathering in June, I
>> was told that the GU-74b is no longer being manufactured, so is not
>> available in any large supply for replacement/repair.
>>
>> For this reason, the OM-Power people have discontinued the OM-3500 amp
>> and replaced it with another model.
>>
>> Good luck es 73
>> Don
>> N8DE
>>
>>
>>
>>
>> Quoting k3it <gokoyev+k3it at gmail.com>:
>>
>>> Does anybody see any obvious flaws in this amp http://goo.gl/lqPBie
>>>
>>> I could not find the actual schematic.
>>>
>>> I'm thinking of buying a Ukrainian made amp, for nostalgic reasons :)
>>>
>>> 73
>>> Vasiliy K3IT
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>>
>>
>>
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