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!!!
?
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. ?
?
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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Typical grid of 75V only happens when you do not exceed your Ig and Ip limits. If you follow the Heathkit and AL80B limits, you will exceed all of the max metrics per Eimac, including grid Dissipation. Grid voltage will not be 75V if you drive the amp with 100W or 150W or 200W.?
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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
?
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
?
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.?
?
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.
?
example:
100W X 115 = 11,500 and extracting the square root = 107.2V RMS.?
107.2 X 2sq (1.4) = 150V?
?
150 X 0.2 =30 and so 30W of grid dissipation is exceeding Eimac 20W of grid dissipation by 50%.?
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Eimac states driving impedance is 115 Ω grid dissipation = peak voltage X grid current.?
so at 100W drive, peak grid voltage is 150V 150V X 0.2Ig = 30W grid dissipation. ?30W ? I don't think you can calculate the power dissipated on the grid this way : grid dissipation = peak voltage X grid current. What are your sources on this interesting topic? I don't know where the 100W of the input are dissipated. ? If your formula is good, it would be very worrying. De la part de Adrian Fewster via groups.io
贰苍惫辞测é?: dimanche 13 avril 2025 22:56
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Great Post thankyou, I recently ordered a replacement tune cap
for my sb-220 from RF Parts, should be here soon.
I am wondering what the current Tariff situation will do to amp
parts pricing, we will see.
That's a great amp, you should be proud of that repair.
73
vk4tux
On 14/4/25 06:25, KG2RG via groups.io
wrote:
toggle quoted message
Show quoted text
I own a Heathkit SB-1000. Have not had it to long, just a few
months. Had a few issues and just wanted to share them and what
I did to fix them.?
one day on 80M I think I hit a bad something. Bad tune or
wrong ant, I’m not sure but had an arc or something. After that,
80 was not tuning up at all. 40M and up worked fine but ones in
a while, I could swear I seen and even Hurd an arc. I thought it
was the tube, but it was just the reflection off the tube that
is visible through the right side cabinet. This started
happening more and especially while tuning up. And the breaker
kicked off the amp and it went back on.?
I took the cabinet off and had a good view at the area that I
suspected was arcing and I noticed the wire from the wound core
L9 to the band select was broken. There was a small gap between
the wire and the chassis about 1/8 or less and I seen it arc
across.?
Also, turn 11 on the 80M/160m tank L8 was tarnished black and
the plastic form/turn spacers were melted to the point that the
shape collapsed into two pieces, pushing into each other with
some of the turns, touching each other. ?
Also, the 2.5mH RF choke fried. It lost value but was not
open. This agile junctions with the lead to L9 wound core wire
that broke.?
I replaced the RF choke, fixed the wire, pulled the L8 tank
out, cleaned with toothpaste, water mix, rinsed with water, then
rinsed with 91% alcohol, Fabricated plexiglass, spacers and
reformed the tank.?
I also used strips of paper soaked with DeoxIT to clean the
relay contacts, a trick I learned from my friend Paul. I tested
all of the diodes on the rectifier board, inspected everything,
tightened all bolts, including the loose ones that hold the tube
socket, they also ground the grids. I did the washer mod on the
band select junction that runs to the door knob, capacitor on
the plate capacitor to prevent corona. I cut many long leads at
many junctions from the original builder. and I cleaned
everything.?
now she is working great, here is some of the data I recorded
after tune up on several bands.?
160M
68W drive = 600W out
Ig = 150mA
Ip = 380mA
Vp = 2900
Zp = 7632
input = 1,102W
efficiency = 54.45%
?
?
80M?
62W drive = 800W out
Ig = 150mA
Ip = 425mA
Vp = 2900
Zp = 6824
Input = 1,232.5W?
efficiency = 65%
40m
63W drive = 810W out
Ig = 150mA
Ip = 400mA
Vp = 2910
Zp = 7275
input = 1,164W
efficiency = 69.6%
?
20M and 15M Efficiency about 63%
10M?
58W drive = 700W out
Ig = 150mA
Ip = 435mA
Vp = 2900
Zp = 6667
input = 1,261.5W
efficiency = 55.5%
I have ran about 10 hours or so since I repaired the amp and
I’m pretty happy. I do not run the limits in the manual, the
manual max limits are:
Ig = 200mA
Ip = 550mA
Output power = 1KW
thats nuts and contradicts Eimac data sheet for a 3-500Z
?
Eimac Data sheet max at typical operation at 3KV
Ig = 108mA
Ip = 400mA
output 740W
?
Heathkit manual max limits = 37.5% over Eimac max specs and
has you exceeding grid dissipation by 50%. Grid is the most
fragile part of the tube.?
Eimac states driving impedance is 115.?
grid dissipation = peak voltage X grid current.?
so at 100W drive, peak grid voltage is 150V
150V X 0.2Ig = 30W grid dissipation. ?30W grid dissipation is
50% over Eimac 20W Grid Dissipation.?
I do runs a little over on SSB, about 150mA of Ig and 400mA
of Ip, but on CW I run a max of 100mA of Ig and/or 400mA of Ip,
no more.?
well, thanks to my friend Paul for his great mind and
others!!!
?
thanks for reading. Hope this helps someone out there.?
KG2RG
|
I own a Heathkit SB-1000. Have not had it to long, just a few months. Had a few issues and just wanted to share them and what I did to fix them.?
one day on 80M I think I hit a bad something. Bad tune or wrong ant, I’m not sure but had an arc or something. After that, 80 was not tuning up at all. 40M and up worked fine but ones in a while, I could swear I seen and even Hurd an arc. I thought it was the tube, but it was just the reflection off the tube that is visible through the right side cabinet. This started happening more and especially while tuning up. And the breaker kicked off the amp and it went back on.?
I took the cabinet off and had a good view at the area that I suspected was arcing and I noticed the wire from the wound core L9 to the band select was broken. There was a small gap between the wire and the chassis about 1/8 or less and I seen it arc across.?
Also, turn 11 on the 80M/160m tank L8 was tarnished black and the plastic form/turn spacers were melted to the point that the shape collapsed into two pieces, pushing into each other with some of the turns, touching each other. ?
Also, the 2.5mH RF choke fried. It lost value but was not open. This agile junctions with the lead to L9 wound core wire that broke.?
I replaced the RF choke, fixed the wire, pulled the L8 tank out, cleaned with toothpaste, water mix, rinsed with water, then rinsed with 91% alcohol, Fabricated plexiglass, spacers and reformed the tank.?
I also used strips of paper soaked with DeoxIT to clean the relay contacts, a trick I learned from my friend Paul. I tested all of the diodes on the rectifier board, inspected everything, tightened all bolts, including the loose ones that hold the tube socket, they also ground the grids. I did the washer mod on the band select junction that runs to the door knob, capacitor on the plate capacitor to prevent corona. I cut many long leads at many junctions from the original builder. and I cleaned everything.?
now she is working great, here is some of the data I recorded after tune up on several bands.?
160M
68W drive = 600W out
Ig = 150mA
Ip = 380mA
Vp = 2900
Zp = 7632
input = 1,102W
efficiency = 54.45%
?
?
80M?
62W drive = 800W out
Ig = 150mA
Ip = 425mA
Vp = 2900
Zp = 6824
Input = 1,232.5W?
efficiency = 65%
40m
63W drive = 810W out
Ig = 150mA
Ip = 400mA
Vp = 2910
Zp = 7275
input = 1,164W
efficiency = 69.6%
?
20M and 15M Efficiency about 63%
10M?
58W drive = 700W out
Ig = 150mA
Ip = 435mA
Vp = 2900
Zp = 6667
input = 1,261.5W
efficiency = 55.5%
I have ran about 10 hours or so since I repaired the amp and I’m pretty happy. I do not run the limits in the manual, the manual max limits are:
Ig = 200mA
Ip = 550mA
Output power = 1KW
thats nuts and contradicts Eimac data sheet for a 3-500Z
?
Eimac Data sheet max at typical operation at 3KV
Ig = 108mA
Ip = 400mA
output 740W
?
Heathkit manual max limits = 37.5% over Eimac max specs and has you exceeding grid dissipation by 50%. Grid is the most fragile part of the tube.?
Eimac states driving impedance is 115.?
grid dissipation = peak voltage X grid current.?
so at 100W drive, peak grid voltage is 150V
150V X 0.2Ig = 30W grid dissipation. ?30W grid dissipation is 50% over Eimac 20W Grid Dissipation.?
I do runs a little over on SSB, about 150mA of Ig and 400mA of Ip, but on CW I run a max of 100mA of Ig and/or 400mA of Ip, no more.?
well, thanks to my friend Paul for his great mind and others!!!
?
thanks for reading. Hope this helps someone out there.?
KG2RG
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Re: Commander HF-2500 meter lamps and HV PS
Jim, VE7RF,?
that is a boatload of FB info!!! I had not had a chance to respond but have read it twice and may need to read it a few more times and drill it in. Thank you!!! Great contribution to me and likely many others too.?
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Is there a way to remove the red tx led without taking off the front panel?? I cannot see in the back because of the large filter caps.? TU ..Bill?
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Re: CTR Engineering/W8JI Response?
Tom is great. Just email him again
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Re: Commander HF-2500 meter lamps and HV PS
Yeah. Weird.
It printed out fine here.
"Email me at gudguyham@.... Lou"
Alek VK6APK
On 13/04/2025 12:31 am, Steve wrote:
toggle quoted message
Show quoted text
Come to think of it... if your ISP won't display A O L dot com,
then it may not even allow you to e-mail to A O L dot com.
On 4/12/2025 9:26 AM, Steve wrote:
"That" was supposed to be "at A O L dot com" without the
spaces. Your ISP probly doesn't like the A O L part and
removed it.
Steve K0XP
On 4/12/2025 8:27 AM, KG2RG via
groups.io wrote:
gudguyham@....
Lou.
what
is that??? ? Not an email?
--
See my QRZ.com page at
--
See my QRZ.com page at
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Re: Commander HF-2500 meter lamps and HV PS
Ok, thanks. I just emailed you Lou
|
Re: Commander HF-2500 meter lamps and HV PS
toggle quoted message
Show quoted text
On Saturday, April 12, 2025, 11:27 AM, KG2RG via groups.io <justinandyazny@...> wrote: gudguyham@.... Lou.
what is that??? ? Not an email?
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Bill K3HZP