[Amps] GS35B Amps Common Problem / few more comments

[Jeff Blaine]

The grid on the 3000 is indestructible where the 8877 needs good 
protection.  On the other hand, the output C of the '3000 is quite a bit 
higher than the 8877 (about 25 pf vs 10 pf) and for a guy cooking a 
mulitband amp, it's a factor when it comes to building the output net.  
An L-PI will fix it, but I mention that because it's a complicating 
factor.  Definately not the right choice for a first build.

73/jeff/ac0c
alpha-charlie-zero-charlie
www.ac0c.com


On 11/7/19 8:52 AM, mark bitterlich wrote:
> While I totally agree that the 8877 is a great tube, and has been used successfully in many great amp designs both commercial and homebrew, I personally agree with Carl. The 3CX3000A7 gives the best performance, dollar per watt, than any other tube I've ever had experience with. Only a very few ham radio amps used it, so possibly  not as many hams have had experience with it. Wa3jpy
> -------- Original message --------From: Jim <jimw7ry at gmail.com> Date: 11/6/19  16:26  (GMT-05:00) To: amps at contesting.com Subject: Re: [Amps] GS35B Amps Common Problem / few more comments Agreed! 8877 is one the the BEST tubes for ham radio.LOTS of them out there and available. Hams bought many of them for spares that never got used; Because the 8877 was such a robust tube. Most 8877 tubes got babied... Except for contesting... But there is testimonial from K3LR's large and busy contest station below. So even in a contesting environment, the 8877 goes STRONG!8877/3CX1500A7 hard to beat!Thanks73Jim W7RYOn 11/5/2019 8:34 PM, Tim Duffy wrote:> Hello Jim,>> I agree - the 8877 - 3CX1500 is a VERY good Ham Radio tube. I have several in service here at K3LR that are 30 years plus years old.> 18 amplifiers here using 8877s that make 1500 watts output RTTY with high TX duty cycle - no problem - all the way to 220 MHz!>> The 8877 is an excellent engineered tube for amateur radio - easy to build amplifiers with the 3CX1500A7.>> 73> Tim K3LR>> -----Original Message-----> From: Amps [mailto:amps-bounces at contesting.com] On Behalf Of MU 4CX250B> Sent: Tuesday, November 5, 2019 9:12 PM> To: Carl> Cc: amps at contesting.com> Subject: Re: [Amps] GS35B Amps Common Problem / few more comments>> You may be a bit harsh, Carl!  I’ve lost two 8877s  in the past half> century or so, and it was my fault both times. The first was when I> stupidly let the filament voltage drop way below specs, and the second> was when the blower on my Alpha 9500 failed and I didn’t notice for> two weeks. My workhorse homebrew amp, built in the 1970s, has an Eimac> 8877 with a 1978 date code. Still full output, 4300V on the anode.> 73,> Jim w8zr>> Sent from my iPhone>>> The 8877 is a fragile short life wannabee befitting an oxide cathode tube>>>>>> Carl>>>>> _______________________________________________> Amps mailing list> Amps at contesting.com> http://lists.contesting.com/mailman/listinfo/amps>> _______________________________________________> Amps mailing list> Amps at contesting.com> http://lists.contesting.com/mailman/listinfo/amps_______________________________________________Amps mailing listAmps at contesting.comhttp://lists.contesting.com/mailman/listinfo/amps
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