[Amps] 4 KW?

[Adrian]

Thanks Alek, That advice lines up with what I have seen on VKC, and I 
wondered why re; 4CX1000 tubes used on DX2, DX3 (2x).


73


Adrian

On 24/6/22 14:57, Aleksandar Petkovic wrote:
> The main one is that you cannot get a good new tube in this country.
>
> Horror stories abound of people spending hundreds of dollars again and 
> again, only to have tubes fail in very short order. Even ones that 
> they bought from OM Power.
>
> All FU728F tubes that you see advertised on Ebay are factory rejects. 
> They should never have found their way onto the market.
>
> I friend of mine went through 2 tubes in 2 months. He now uses the 
> 4CX1000A in his DX-2SP and we know he'll never have another tube fault 
> in that amplifier. Thankfully Rudi  built that model such that 
> 4CX1000A tubes can easily be substituted. He had the socket modified 
> and had a 6V tap on the transformer for the heater. A quick tickle of 
> the pre-bias and bias and you are on the air with a proper tube that 
> will last forever.
>
> I bought 10 x FU728F tubes ten years ago. They all failed very 
> quickly, except for one, which has been in daily use for the past 
> couple of months now. That was when the tubes were US$100 each landed 
> here in VK. I sold them for virtual cost price. I lost a lot of money 
> on them. I still have 2 of the failed/returned tubes left. Each year, 
> I manage to give one or two away as ornaments at our local hamfest.
>
> So, as I said, don't ever go anywhere near a FU728F amplifier unless 
> it has already been retrofitted with the 4CX1000A.
>
> 73, Alek, VK6APK
>
> On 24/06/2022 10:00 am, Adrian wrote:
>> Alek, What faults / problems did you find or hear about with the 728 ?
>>
>>
>> 73
>>
>>
>> Adrian
>>
>> On 24/6/22 10:14, Alek Petkovic wrote:
>>> And those FU728F tubes are junk. It is all but impossible to get a 
>>> good one these days. The supply has completely dried up.
>>>
>>> I would not touch an amplifier that uses that tube.
>>>
>>> 73, Alek, VK6APK
>>>
>>>