The formula for grid dissipation is?
Pg = Vgc X Ig
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where vgc is the peak positive grid to cathode voltage.
Ig is the DC grid current.?
grid dissipation is peak voltage multiplied by Grid current.?
If you run 100W CW exciter drive into an Eimac 3-500Z at the SB-1000 and AL-80B max limits listed in their manuals of Ig 200mA and Ip 550mA, then this is what calculates.?
as per Eimac data sheet, drive impedance is 115 and ?grid dissipation is 20W.?
2 figure out peak voltage:
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if
voltage squared divided by resistance = power.?
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then
100W CW drive X 115 drive impedance = 11,500. Extracting the sq root = 107.2V RMS.?
for peak voltage, 107.2V x1.4 (2sq) = 150 peak voltage.?
finally
150 peak V multiplied by 0.2mA Ig = 30W grid dissipation. That exceeds Eimac listed grid dissipation by 50%.?
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On 4/17/2025 6:51 AM, Jim VE7RF via groups.io wrote: ###? ?On the SB-1000,? AL-80B, they rate it at 1000w? pep out on SSB? (550 ma).....and? only 850 watts out on CW (450 ma). The person to ask to clarify this would be the man who designed the SB1000 and AL-series: Mr. W8JI, hisself. Steve, K0XP
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On 4/17/2025 6:41 AM, Jim VE7RF via groups.io wrote: (A) 70.7 vrms x .3 =? 21.21 watts? ?grid diss
(B) 100 V peak? x .3? =? 30 watts grid diss. V-rms obviously yields watts-RMS, and Volts-peak gives watts-peak. Perhaps Reid Brandon? will chime in.? ?Right now, I can't fathom why Eimac would use peak cathode RF voltage? instead of RMD cathode voltage. Because SSB is measured by it's peak: Peak Envelope Power. RMS only applies under continous carrier conditions. Steve, K0XP
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On Wed, Apr 16, 2025 at 08:20 AM, KG2RG wrote:
Jim, W6SAI, best book around!!! Sometimes called the West Coast book, sometimes called the big green book, the Radio handbook by William ?I Orr, great stuff!!!
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Heathkit and Ameritron were able to convince Eimac to give a 1 year warranty. This was also back when tubes were plenty and cost less. ?
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the question is what happens when you run a Eimac at Ip at 550mA CW? You exceed the Eimac specs by 37.5%
what is the most fragile part of a tube? the grid, and it’s rated at 20W dissipation.?
so what happens at 200mA of Ig with 100W of drive? ?
the drive impedance of the 3-500Z is 115 per Eimac.?
Grid dissipation is peak voltage X grid current.?
at 100W drive, peak grid voltage is 150V
150x0.2=30W. At 30W, max specified Grid dissipation is being exceeded by 50%?
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As I mentions, I do run a little over for SSB since voice modulation duty cycle is 50% or less, so I may run around 150mA of grig and a little over 400mA on the Ip. But for CW, I do not exceed the Eimac specs. I also run it with just a little color to activate the getter.?
###? ?On the SB-1000,? AL-80B, they rate it at 1000w? pep out on? SSB? (550 ma).....and? only 850 watts out on CW (450 ma).??
?
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On Wed, Apr 16, 2025 at 08:59 AM, Peter Voelpel wrote:
Yes, power is never calculated with peak voltages.
73
Peter, DJ7WW
That's what I thought too.? It shoulda been? RMS cathode voltage? X? DC grid current? =? Grid dissipation.................. BUT it's not.? Eimac uses? PEAK? RF? cathode voltage X? DC grid current =? grid diss.? On a L4B, it runs 300 ma? DC grid current and 800 ma plate current? at 2.5 kv under load.? With 100 watts? drive it amounts to either: (A) 70.7 vrms x .3 =? 21.21 watts? ?grid diss (B) 100 V peak? x .3? =? 30 watts grid diss.? The above is for TWO tubes.? ?Each tube has? 20 watts of? CCS grid diss.? ?So a total of 40 watts? CCS grid diss.? Perhaps Reid Brandon? will chime in.? ?Right now, I can't fathom why Eimac would use peak cathode RF voltage? instead of? RMD cathode voltage.?
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On Wed, Apr 16, 2025 at 07:32 AM, Fran?ois wrote:
Just to add some elements to the discussion. Here's what I noticed on my Drake L-7, so with 2 x 3-500Z. The -9V bias on the grid is generated directly on the grid; the 9V zener is not in the cathode circuit.
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Note that the grid current is lower when the plate voltage increases.
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In France, we're limited to 500W, but I wonder how in the USA you can reach 1 kW without exceeding the maximum Eimac values.
That 1 kw pep output from the single 3-500Z? is because they are using IVS? (intermittent voice ratings) for SSB.? ?That operation was approved by Eimac. IE:? it's because of the low duty cycle on SSB.? They rate the same amp at 850 watts? output on CW mode.? Same idea,? CW is a reduced duty cycle....... but not as much as SSB...... hence the 1000/850 ratings? for SSB / CW.?
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Francois.? No problems with removing all those grid caps and grid chokes.? ?Save the 2 x grid chokes.??
Use 3 x separate copper straps? for each tube....then bond the? 3 x grid pins directly to the chassis.? Best mod for those amps yet.
IMD improves a bit.? And also less drive required.?
But with any bias diodes installed, more drive required to overcome the grid bias,? ?so it's like one step forward.....then one step backwards.? ?It comes out a wash.?
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Jim, et al.
I just learned a few things that should be of interest on the subject of Econco.
This morning I had an inquiry from a local broadcast engineer I know.
He asked me about a 4CX12,000A knowing I was involved with taking the CC curves on the prototype when I was employed at the big E.??
I am retired and seldom do anything with tubes any longer, I like to listen to my stereo (no tubes in it either!)
He mentioned the last tube he got from Econco lasted only 12 days.
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Earlier in the year I was speaking with Debbie Storz regarding another Econco issue (re: warranty and pricing).
I just tried calling her to get help with the failure of the 12,000A but I learned she was just laid off, as was Lourdes, the other woman in customer service there (her responsibility is / was for export and Industrial tubes). The new owner TransDigm has been laying off or forcing retirements to reduce overhead. Last December the tube engineer at Eimac responsible for the tubes you all know, quit when they gave him different marching orders. TransDigm is a huge conglomerate -? check the current stock price of $1300 a share. IMHO they bought CPI MPP in order to extract as much profit as they can squeeze out of it.? ??
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Case in point, I recently found the price of an Econco rebuilt 4CX10,000D went from $2059 from last year to $3059 now, effective April 2025. (I checked my notes twice!) this means a new Eimac 10D will be $6118 provided Econco still bases the price of a rebuilt as one half of a new tube price.??
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I hate to be the bearer of bad news but there's more!
Seems Debbie had been speaking with a CB op who had an issue with a tube that he wanted some answers on, technical questions that used to be routed to Matt Lindsey and before him Joe Canaveri. The policy used to be that one of the aforementioned employees would provide test results etc. Now there isn't anyone available there that knows a volt from an amp.
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Anyhow, what I learned last Dec was the CBer insulted Debbie more than once in a long telefone call but apparently she brushed him off politely, I'm sure she wasn't insulting because that's not her nature. The man hung up and called the CEO who must have got an ear full of CB anger because he then informed Debbie that henceforth Econco wasn't accepting any rebuilds from CB or hams.?
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I can't get a clarification from her as to that policy now since she's gone but I'm pretty certain that they will not do special mods like you described where a grid flange could be added to a 3CX3000A7 for example. I was getting that done at the factory level 20 years ago no sweat, for a few bucks only. Those days are gone!?
very 73 and GL with ur project!
Reid? ?W6MTF? ? ?
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“In France, we're limited to 500W, but I wonder how in the USA you can reach 1 kW without exceeding the maximum Eimac values.”
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how do you reach 1 KW input or output?
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In France, the power limit is 500W output, or 500W DC input to the final amplifier??
in the US, power was once limited to 1KW DC input to the final amplifier.?
on SSB, that got you about 1200W to 1400W PEP. On CW, ?a class C got you about 750W out. But on AM, a KW input hot you 750W of carrier. At 100% modulation, that would be about 3KW PEP output. You could even get more if you clamp the neg peaks at 95% and it’s possible to hit 175% on your positive peaks for 7x you carrier power, PEP could be up at 5250W PEP out.?
i have never tried it, I was not a ham back in those days when all the big iron stations running the Johnson desktop, invader 2000, BC gates and stuff like a pair of 4-1000 modulated by a pair. But those guys were not happy when the FCC changed the power limits to 1500W output, regardless of mode.?
I have a Viking 2 and a home brew from the design out of QST. My RF deck is from a 1959 QST article, a class C running a pair of 1625s.? my Modulator is from a 1961 QST article. The speech amplifier is a 12AX7 coupled to a 12J5 and coupled to a driver transformer single plate to push pull grids 1625s in class AB1 into the mod iron.?  
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Yes, power is never calculated with peak voltages. 73 Peter, DJ7WW -----Original-Nachricht----- Betreff: Re: [ham-amplifiers] SB-1000 Datum: 2025-04-16T08:05:53+0200 Von: "Adrian Fewster via groups.io" <vk4tux@...> An: " [email protected]" < [email protected]> With this one to have a power result in watts, don't the formula inputs, re voltage, need to be an average, or rms value rather than peak ? 73 vk4tux On 16/4/25 15:27, Jim VE7RF via groups.io wrote:
I found that formulae buried in 1-2 places? re grid diss.? No clue
where I discovered it.
It is indeed...... Peak cathode voltage X? DC grid current = grid diss.
?
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If anyone sees this book at a Hamfest, buy it!! This is a great book.? 
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Jim, W6SAI, best book around!!! Sometimes called the West Coast book, sometimes called the big green book, the Radio handbook by William ?I Orr, great stuff!!!
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Heathkit and Ameritron were able to convince Eimac to give a 1 year warranty. This was also back when tubes were plenty and cost less. ?
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the question is what happens when you run a Eimac at Ip at 550mA CW? You exceed the Eimac specs by 37.5%
what is the most fragile part of a tube? the grid, and it’s rated at 20W dissipation.?
so what happens at 200mA of Ig with 100W of drive? ?
the drive impedance of the 3-500Z is 115 per Eimac.?
Grid dissipation is peak voltage X grid current.?
at 100W drive, peak grid voltage is 150V
150x0.2=30W. At 30W, max specified Grid dissipation is being exceeded by 50%?
?
As I mentions, I do run a little over for SSB since voice modulation duty cycle is 50% or less, so I may run around 150mA of grig and a little over 400mA on the Ip. But for CW, I do not exceed the Eimac specs. I also run it with just a little color to activate the getter.?  ?
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> ?I would not run the tube at their stated? zero bias....... idle current is way too high.? It needs bias.? ? 50 ma? for idle current is ample. ? I agree with you. That's why with a 2500 V HT I chose a -9 V bias which brings the quiescent current to 2 x 50 mA. ? The curves I posted are with the original Drake L-7 schematic where the grids are not actually grounded. The difficulty is being able to easily return to the original assembly, if the ground-grid wiring was, for example, unstable. ? 
? I am currently making a wiring modification to ground the grids. ? I kept the possibility of setting the polarization to zero so as to make the plates redden periodically, on the simple rest current, to perfect the degassing of the tubes
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I believe the problem isn't the voltage itself, which would be found (measured) between gate and ground. The problem is knowing where, in the circuit, the input power is dissipated. The gate-to-ground connection is actually a kind of feedback loop, much like an input-to-gate connection with a resistor between cathode and ground, not decoupled by a capacitor. ? I assume that part of the input power goes, among other things, to the output circuit. Why would this power be dissipated by heating the gate? ? This doesn't mean that the gate doesn't heat up.
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Just to add some elements to the discussion. Here's what I noticed on my Drake L-7, so with 2 x 3-500Z. The -9V bias on the grid is generated directly on the grid; the 9V zener is not in the cathode circuit. ?
? Note that the grid current is lower when the plate voltage increases. ? In France, we're limited to 500W, but I wonder how in the USA you can reach 1 kW without exceeding the maximum Eimac values.
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VK4TUX.? ?Nope.? that -75 vdc is for BIAS? voltage and only when operating Class C.... (either grid or cathode driven).?
Look under? cathode driven....and 0 vdc? bias voltage. U will see 215 V peak grid voltage.?
When u drive the cathode negative,,,,,,,? u are putting positive on the grid.?
I found that formulae buried in 1-2 places? re grid diss.? No clue where I discovered it.?
It is indeed...... Peak cathode voltage X? DC grid current = grid diss.?
That 1 kw pep out in the? SB-1000.....and also the AL-80B? ?is the ...'ICAS'? rating....... or as Bill Orr calls it.... the IVS? (intermittent voice service)? rating....... both terms are used for SSB only.?
Per W8JI,? who designed those amps ( the heathkit version was licensed from Ameritron)? the 1 kw pep out rating on the single? 3-500Z? was fully approved by EIMAC.?
Once tuned up..........? while talking on SSB,? you will notice that the AVERAGE DC plate current....and also the AVERAGE? ?DC grid current is only 1/2 of the key down CXR value.? ?This is how they can get away with the 1 kw pep out on SSB? ( and also 850 w out on CW)? ?rating on that amp.? ?IE: lower duty cycle.? ?
Here is another eimac spec sheet.? ?I would not run the tube at their stated? zero bias....... idle current is way too high.? It needs bias.? ? 50 ma? for idle current is ample.?
https://frank.pocnet.net/sheets/088/3/3-500Z.pdf
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Yes, that’s what Eimac says typical grid should be. I Eimac also states max limits:
Ig 108mA
Ip 400mA
max output 740W
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but Heatgkit SB-1000 and AL 80B must have special permission from god. Their manuals say max limits are:
Ig 200mA
Ip 550mA
output 1000 watts
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To do this, you will need to drive the exciter around 100W and you will exceed the typical 75V grid and likely porn up your 3-500Z.?
In other words, ignore the manual limits and just follow the Eimac data sheet limits and you won’t exceeded your grid dissipation?
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> The Eimac formula for grid dissipation is: > Pg=Vgc X Ig ? I can't find this magic formula in the Eimac documents I have. Could you post this document or a URL that allows us to find it? De la part de Adrian Fewster via groups.io
贰苍惫辞测é?: mercredi 16 avril 2025 03:18
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1st,
voltage squared divided by resistance equals power.?
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2nd,
The Eimac formula for grid dissipation is:
Pg=Vgc X Ig
where Vgc is the peak positive grid to cathode voltage
and Ig is the DC grid current.
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example:
100W X 115 = 11,500 and extracting the square root = 107.2V RMS.?
107.2 X 2sq (1.4) = 150V?
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150 X 0.2 =30 and so 30W of grid dissipation is exceeding Eimac 20W of grid dissipation by 50%.?
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Brandon DX