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All About the GI-7B (t)Last update to this page was onMay 28, 2014The GI-7B(t) is a very rugged metal ceramic tube built during the cold war for use on Russian tanks and other military vehicles. The GI-7BT is a more ruggedized version of the same tube featuring a fatter ceramic element but otherwise the same as the thinner GI-7B. You will find these tubes that have white ceramic and some that have pink or purple ceramic and we have found no difference in the performance of these tubes. NOTE: Some suppliers sell the GI-70B and the GI-70BT tube which is the same tube WITHOUT the anode cooler. Always be aware of what you are buying.Links:Homebrew.Retrofits and ConversionsAmp Supply LA-1000.Dentron Clipperton L and Clipperton QRONotes: The Clipperton L and the Clipperton QRO are both a beautiful table top near legal limit amplifier and will perform to full specifications when properly retrofitted with the GI-7B tubes.
They are easier to retrofit than the MLA-2500 and will give nearly identical performance. Please read all the notes below on the MLA-2500 before you decide to start this project.Dentron GLA-1000Notes: The GLA-1000 is a beautiful little amplifier and will perform to full specifications when properly retrofitted with the GI-7B tube. It is important to note that, as with any retrofit, you should NOT expect more out of this amplifier than it was designed to provide. You can not get more power output from this amp than the power supply is capable of providing. Also, the retrofit of the GLA-1000 (this applies to most of the other sweep tube amp retrofits too) requires changing the power supply to a voltage doubler. When you do this, the plate voltage will be higher.
Obviously if you can not get more power from the power supply, then the plate current will be lower. What this means is that the plate load impedance is going to change. What that means is that the Pi-network will no longer provide a proper match to the antenna jack. You can get the amp to work but it will not come up to full output. I have provided some general guidelines for establishing the proper tap points on a tank coil here. There are other opinions on this subject so please understand this is just one of them. I am not in a position to hold your hand through a project like this so be well aware of what you are getting yourself into before taking this on.
W4ZT.Dentron MLA-2500Notes: The MLA-2500 is a beautiful table top near legal limit amplifier and will perform to full specifications when properly retrofitted with the GI-7B tubes. This is NOT a project for the faint of heart. If you do not have experience doing metal work, schematic reading, figuring things out from pictures, troubleshooting and intuitive layout design based on available components, you may not want to take this project on. You are not going to find a list of detailed instructions here for doing this retrofit. You are not going to find a detailed list of parts for doing this retrofit.
You will find a detailed schematic that reflects most of the changes that can be made but not necessarily all of them. If you do not find the information you are looking for here, I am afraid that I do not have it. Carefully study the pictures in these retrofits. You should also study other MLA-2500 retrofits done using other tubes. All of this study will give you better ideas for doing your own work.
W4ZT. (a look at many of Lawson's projects). (worth a look no matter what amp you work on)Drake L4B.Heathkit SB-200.Heathkit SB-230Please note: Although we show you how the GI-7B can be used to retrofit the SB-230 in the original conduction cooled configuration, we feel it is only fair to tell you that the tube will not cool as well as a conduction cooled amp as it will with the factory cooler on the tube and a small fan blowing on it.
La-1000 Amplifier Tubes
If you still want to do the conduction cooled retrofit, we can supply the new cooler as well as the socket. Even if you do the retrofit as a conduction cooled amp, it is wise to blow a small amount of air around the tube to keep the base of the tube properly cooled.
It is also worth mentioning that even though the SB-230 has been retrofit with the GI-7B standing vertical, that is not the best or recommended way of doing it. Our experience indicates that there is much less work and much better operation if the tube is mounted horizontally against the right side wall. We do have sockets and can provide the cooler for the conduction retrofit but We do NOT provide complete KITS for this retrofit. Detailed pictures of the work. (462 Kb PDF updated 8/10/08).
This is NOT the way to go!Yaesu FL-2000.Construction details.GI-7B Tubes and Parts SuppliersGI-7B Tubes - I have many people ask about these tubes and where to buy them. You can purchase them from any number of dealers, most of which are outside the USA. The prices listed by these dealers usually does NOT include the shipping charge so be sure to check that before ordering. Also, be sure that the price includes the anode cooler. You don't want to pay full price for a tube that doesn't have the anode cooler. The GI-70 does NOT have a cooler.GI-7B Sockets - See the pictures at the bottom of this page.Bias Boards - variable bias for your amp.GI-7B tubes and other parts - I have purchased from each of these suppliers. I will NOT list a supplier that I have had bad experience with or that I have not had dealings with.
La 1000a
Harbach Electronics - SS-100 Universal Soft-Start -. Anthony Welsh -On Ebay:.
KW-Tubes - On Ebay:. QRO-Stuff - On Ebay:. kalleb - On Ebay:GI-7B Socketsby K4POZ and W4ZTThese sockets are professionally crafted by K4POZ and W4ZT to provide you the best socket for your retrofit or new construction project. These sockets are designed for the best possible connections to the tube while allowing full air flow around the socket for more than adequate tube cooling. These are PLUG IN sockets.
There are NO hold down clamps to fiddle with. The tube is completely removable and insertable from the anode side of the chassis. We have designed the grid and cathode connections using full contact finger stock to insure that you have the best RF connection possible. The socket can be mounted either on top of a chassis or sub mounted below a chassis which is pressurized for forced air cooling. Mounting can be horizontal or vertical. Please COMPARE this socket with any other socket you can find.(click on the small pictures to see larger pictures in a new browser window)1234View straight down into the socket showing the finger stock.5The socket can be mounted below the chassis by reversing the mounting hardware.6Socket shown mounted below the chassis.7Tube in the socket mounted below the chassis.8PTFE ChimneyNo longer available.Comments from users:.
Amp Supply La-1000a Manual Instructions
What a nice piece of hand-work!I thank your for your UFB and kind communication and support. IT9BLB/KF6FBC. The GI-7B socket arrived today. I was amazed at the high quality.This is much better than the other one I bought, and better than any that I have seen.
Your socket is very well built, compact and provides much better contact to the tube than the others. The socket will be ideal for all of my GLA-1000B conversions. K8KSW. That's a nice piece of work. I wont build them myself anymore, I'll use yours!
Looking for someone with knowledge of this amp.Hi Everyone,I purchased this amp at a swapfest last fall for a reasonable price as-is without a manual. I replaced the 4 finals (6JB6's) because the output was about 250 watts CW. When I located a manual, I learned the manual listed the finals as 6MJ6's. With the new tubes I show output about 300 Watts CW.Someone replaced the original meter and I can't read the plate voltage although it's suppose to be about 1170 VDC and operate about 600 ma. For about 600 watts CW. The meter appears to give a relative reading but doesn't measure the current from what I can tell.I assume the 6JB6 is interchangeble but maybe not.The 6MJ6 runs about $45, double the cost of the 6JB6 so before I invest more money I'd like to know if that's the problem.Anyone help with info on these tubes or what to actually expect from this amp, is greatly appreciated.Paul KD9FM. What company made the LA-1000?
There have been LA-1XXX linears made by several companies over the years.Also, with sweep tubes you are getting about normal output. With 600 watts input, 300 watts is about average on CW.I wouldn't 'split' for the more expensive tubes. For $180 you can add just a few more dollars and get a Heath SB-200 linear which runs a pair of 572B tubes and puts out an easy 600 watts.Sweep tube linears were very popular for the illegal use on the Class 'D' Citizen's Radio Service and were used in a few actual amateur linears (like the Dentron GLA series) back when every TV set around had a sweep tube used in the horizontal oscillator. Back then you could get sweep tubes for $3 or less when the actual transmitting tubes like the 6146 series were in the neighborhood of $10 each. Now days, the sweep tube prices have gone 'out of sight' yet you can still get the 6146 tubes for between $12 and $20 depending on the source.Glen, K9STH. Hi.in answer to your question concerning the LA-1000 (and the later LA-1000A), the unit left the factory with 6MJ6 (4 ea) tubes inside. The LA-1000 hit the market in 1983, followed by the 1000A a year or two later.This unit was basically the same as the Ameritron AL-84, but Amp Supply tended to overate their gear in the power department.Both brands (I have the AL-84, bought new in '84) use the same tubes, but Ameritron advertised 600W pep output, while Amp Supply rated theirs at 1200W pep on the same set of 6mj6's.
Both are what you would call 'light duty' units, and weigh-in at about 20-22 pounds, including the power supply.If you are looking for a KW amp for pretty regular duty, you would be better off investing in a SB-200 Heath. You would loose the 'QSK' feature of the LA-1000, but you would get a good workhorse of an amp.Just as an aside, I fire-up my AL-84 at least once a year, need to or not, and run it at 300w (CW) out.
It still works fine, and has the original tubes in it after 20 years of 'lite' duty. Then it goes back in the closet.(hi).Hope this helps!73, Jim/K7UNZ. Hi again Paul.not exactly sure about your last question but I can give you the specs for the AL-84. I would think they should be the same for your LA-1000 as they are both running the same finals.HV on the meter should read 'about' 1000V.Max power is at 800ma of plate current (about 400W out in CW mode). That is with about 100W of drive.I never run it quite that hard, as I keep the drive to around 75W, which gives me about 300W out on CW.As for the 6JB6's -vs- 6MJ6's.I can't help you there. They may be a good sub for the 6MJ6's, but I really have no info on that at all and would suggest that you go with the factory specs for finals.Items that show up on ebay often have wierd things stuffed inside, so just 'cos it arrived that way doesn't mean it's an okay swap in parts. You might just end up smokin' the whole thing with excessive current due to the tubes.
When in doubt, go original!Hope this helps a bit.again, remember this is a lite duty amp!Amp Supply did make other higher power units, the LK-500ZA/ZB (3-500Z finals), LA-500NT/NT-B (3-500Z finals), and the LA-800A/LA-800NT (3CX800A finals).Jim/K7UNZ. The 6MJ6 is a beefier tube and will handle a bit more power, for sure. I wouldn't spend $180 on a set of sweep tubes unless I had a sucker lined up to buy the amplifier only if it came with new tubes! The sweep tubes originally used cost about $7 each, and that's about what they're worth.Problem with sweep tube amps made by anybody, including the LA1000(A), AL-84 and all the others, is that they are good only for SSB service with limited duty cycle (no compression) and very short tune-up cycles. When I've used these amps, even back when they were brand new, it was obvious that a 20-second long tune-up cycle was simply too long for the tubes, which began to degrade very quickly after a few tune-ups.
Remember, their original intended service was switching pulses at a frequency below 16 kHz, where average power dissipation was very low.I'd go for an amplifier with a real transmitting tube or tubes for anything other than very occasional, and not very serious use.WB2WIK/6. Quote (KD9FM @ Feb. 23 2004,20:57)Looking for someone with knowledge of this amp.Hi Everyone,I purchased this amp at a swapfest last fall for a reasonable price as-is without a manual. I replaced the 4 finals (6JB6's) because the output was about 250 watts CW. When I located a manual, I learned the manual listed the finals as 6MJ6's. With the new tubes I show output about 300 Watts CW.Someone replaced the original meter and I can't read the plate voltage although it's suppose to be about 1170 VDC and operate about 600 ma. For about 600 watts CW.
The meter appears to give a relative reading but doesn't measure the current from what I can tell.I assume the 6JB6 is interchangeble but maybe not.The 6MJ6 runs about $45, double the cost of the 6JB6 so before I invest more money I'd like to know if that's the problem.Anyone help with info on these tubes or what to actually expect from this amp, is greatly appreciated.Paul KD9FM /QUOTEI did some consulting work for Amp Supply. I managed Ameritron, and did design work for them and other companies. Ameritron and Amp supply were different companies.The LA1000 can use either 6JE6 or 6MJ6 tubes.
There is about 5 watts difference in dissipation in favor of the 6MJ6, no big deal.The LA1000 ties the control grid back to the cathode, that is a bad idea. It causes the amp to be a bit unstable on 15 and ten meters becuase feedthrough capacitance is increased.The AL84 grounds the grids, and has a negative feedback resistor to improve IM performance. So they are not similar.300 watts is OK for four tubes on CW. You could get more, but tube life would be shorter.Myself, I'd sell it and get a real amplifier that uses transmitting tubes. Sweep tubes will bankrupt you in the long term. They were OK when they were $5 each brand new, but are not a good deal today.73 Tom. Quote (w8ji @ Feb.
24 2004,12:53) Quote (KD9FM @ Feb. 23 2004,20:57)Looking for someone with knowledge of this amp.Hi Everyone,I purchased this amp at a swapfest last fall for a reasonable price as-is without a manual. I replaced the 4 finals (6JB6's) because the output was about 250 watts CW. When I located a manual, I learned the manual listed the finals as 6MJ6's. With the new tubes I show output about 300 Watts CW.Someone replaced the original meter and I can't read the plate voltage although it's suppose to be about 1170 VDC and operate about 600 ma. For about 600 watts CW.
The meter appears to give a relative reading but doesn't measure the current from what I can tell.I assume the 6JB6 is interchangeble but maybe not.The 6MJ6 runs about $45, double the cost of the 6JB6 so before I invest more money I'd like to know if that's the problem.Anyone help with info on these tubes or what to actually expect from this amp, is greatly appreciated.Paul KD9FM /QUOTEI did some consulting work for Amp Supply. I managed Ameritron, and did design work for them and other companies. Ameritron and Amp supply were different companies.The LA1000 can use either 6JE6 or 6MJ6 tubes. There is about 5 watts difference in dissipation in favor of the 6MJ6, no big deal.The LA1000 ties the control grid back to the cathode, that is a bad idea. It causes the amp to be a bit unstable on 15 and ten meters becuase feedthrough capacitance is increased.The AL84 grounds the grids, and has a negative feedback resistor to improve IM performance.
So they are not similar.300 watts is OK for four tubes on CW. You could get more, but tube life would be shorter.Myself, I'd sell it and get a real amplifier that uses transmitting tubes. Sweep tubes will bankrupt you in the long term.
They were OK when they were $5 each brand new, but are not a good deal today.73 Tom/QUOTEBy the way, I never tried 6JB6s in that amp. So I have no idea if that is why the 'gain' is low. 400-500 watts out would be normal with 100w drive, but it is hammering the tubes pretty hard!!!73 Tom.