[Amps] Why 2 3CX800s instead of one 8877?

[Carl]

That is more than enough voltage to reach the then legal limit of 2000W PEP 
INPUT. That is also similar to the voltage and power of the Dentron 
DTR-2000L.

The limiting factor is the transformer and not the  tube choices.

Carl

----- Original Message ----- 
From: "Martin Sole" <hs0zed at gmail.com>
To: <amps at contesting.com>
Sent: Saturday, April 20, 2019 1:34 PM
Subject: Re: [Amps] Why 2 3CX800s instead of one 8877?


>I don't think the 8877 will be to lively with a mere 2400 volts on its pip. 
>That new transformer will need to up the HT a fair bit.
>
> Filament volts, 8877 5 volts, 8874 6.3 volts, 3CX800 13.5 volts.
>
> Martin, HS0ZED
>
>
> On 20/04/2019 06:55, Roger (K8RI) wrote:
>> I have been using a 76A for many years along with several other amps.
>>
>> I decided I had more amps than I needed even running SO2R with backups so 
>> the 76A went up for sale. I had an immediate buyer, but as the 76 had set 
>> for a few months. I told him I wanted to run it through its paces before 
>> he made the long drive to pick it up.
>>
>> You guessed it. Half power! I had used that amp for well over a decade 
>> with nary a hiccup. I go to sell it and one one of those tubes fails. One 
>> of those tubes, new costs more than the amp is worth. Now I happen to 
>> have a stash of tubes that I could modify it to use.
>>
>> I would prefer to do the mod neatly, complete with a proper transformer 
>> rather than a filament transformer mounted on the back. Yes, I realize 
>> the cost.
>> A single 3CX800 would give me what I had (it's a two hole), but going 
>> with the cost of the transformer, I might as well go with a pair of 
>> 3CX800s, or a single 8877. If I do the conversion to legal limit, I will 
>> have as much, or more into the amp than what I can get out of it, so I'll 
>> probably keep it and sell my Quadra.
>> Of course the third option is to just sell the 76 as is.
>>
>> Other than the replacement cost and availability, Is there a reason for 
>> not using a single 8877 Vs a pair of 3CX800s? Using new tubes the 8877 
>> would have been the economical choice, but I understand that the prices 
>> have gone up. Tube prices for legal limit amps are beginning to make the 
>> new SS legal limit amps look better all the time.
>>
>> I also have a completely restored HT33B (Sans 2 panel screws) with a 
>> ceramic 8295A and 3 spare ceramic 8295As . Last time I used it it had 
>> full power, but that was prior to 1997
>>
>> 73, Roger (K8RI)
>>
>
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