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Re: Amp modification
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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Re: SB-1000
¡°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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Re: SB-1000
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.?
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Re: SB-1000
¿ªÔÆÌåÓý> ?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 -- F1AMM Fran?ois |
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SB-1000
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%
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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%
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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
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Eimac Data sheet max at typical operation at 3KV
Ig = 108mA
Ip = 400mA
output 740W
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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!!!
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thanks for reading. Hope this helps someone out there.?
KG2RG |
Brandon DX
Bill K3HZP