[Amps] GS35B questions

[Jim W7RY]

Great idea.... 

I too am using 2 resistors for the HV return in my 8877 project. I wanted to have a resistor in the power supply as well as in the RF deck. I used a 2K in the power supply and a 2k in the amplifier chassis. The metering circuit takes the ground resistance down to a few ohms in the RF deck. 
I'm using the WD7S triode board setup and analog Simpson meters. 

73 
Jim W7RY 


> -----Original Message----- 
> From: higasa at plum.ocn.ne.jp 
> Sent: Fri, 10 Sep 2010 12:20:53 +0900 
> To: amps at contesting.com 
> Subject: Re: [Amps] GS35B questions 
> 
> Hi again, 
> 
> Regarding a grid drop resistor 
> I am using two resistors; 
> 
> A: a 500 ohm 10 W from HV- to GND in HVPS. 
> B: a 500 ohm 10 W from HV- to GND in RF deck. 
> C: a 3A Si-diode is also connected between HV- 
> and GND in parallel with resistor B; 
> anode is grounded, cathode is connected to HV-. 
> 
> I am using a 0.2 ohm shunt resistor for IP meter, 
> and a 2 ohm for IG meter between these 500 ohm 
> resistor/diode and the bias diode/cathode of the 
> tube in the RF deck; these 500 ohm resistors 
> practically provide no or little error on the meters. 
> 
> de Han JE1BMJ 
> ----- Original Message ----- 
> From: "Marius Hauki" <rezycle.bin at gmail.com> 
> To: <amps at contesting.com> 
> Sent: Friday, September 10, 2010 7:03 AM 
> Subject: [Amps] GS35B questions 
> 
> 
> Hi, I am working on a new GS35B HF amp design. 
> 
> Some questions: 
> 
> -I would like to buy some sockets instead of machining them myself. 
> Could you gentlemen direct me to a person selling sockets that 
> normally have them in stock or at least can deliver within a month or 
> so? 
> 
> -What is the proper "burn in" procedure for the GS35B? I was planning 
> on running the filament of the tube for some time (how long time?) 
> with proper airflow. Do I need to apply HV as well? I don't have a HV 
> tester at the moment. I bought the tubes from UR4RLL. They look new / 
> unused. 
> 
> -I am planning to use the triode control board from WD7S. Any things 
> that I should be specially aware of when using that board with the 
> GS35B (apart from the mod for higher bias voltage)? 
> 
> -I am planning 3650V on the anode. This is significantly higher than 
> the "official" data sheets state, however I notice that the official 
> data sheets rate the tube for military service with less cooling. Does 
> 3650V look like an OK voltage? 
> 
> -I am looking for a SAFE way of running the HV cable from an external 
> HV PSU cabinet to the RF cabinet. I know this has been discussed 
> numerous times before, but again: what is the best cable I can use and 
> what connector should I use? Did we reach a conclusion and some 
> reccomendation on that question? I would like to avoid any possibility 
> at all for the B+ (hv plus)connector connecting before the B- (hv 
> minus) because that may place the RF deck at the HV+ potential if the 
> grounding between the two boxes are broken. (I do not plan on hot 
> plugging, of course). The minus lead should be isolated from the 
> chassis since I plan on using a high wattage drop resistor from 
> chassis ground to B- to be able to measure grid current. 
> 
> -Should I place the grid drop resistor in the PSU cabinet or in the PA 
> deck? I was thinking that placing it in the PA deck would be safer 
> because in case only B+ is connected before B-, the grid drop resistor 
> would connect B- to chassis ground and not keep the PA deck at B+ 
> potential (No I am not going to hot plug the B+ connector, but perhaps 
> some other operator will attempt just that. You never know what can 
> happen in the mid of a contest battle) 
> 
> -I have read that running DC instead of AC on the filament is OK. 
> However I have read somewhere else that it is not OK. I have an AC 
> trafo, but if the primary voltage varies, the filament voltage could 
> be too high or too low and this may hurt the tube. Instead I would run 
> a regulated DC supply, since the filament current is not that high. 
> Any comments on that? Alternatively, any clever way of regulating the 
> trafo by a small series drop resistor or something? 
> 
> 73 
> LB3HC 
> Marius 
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