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Hi Everyone, I built this little 2m amp a couple of years ago, it works perfectly in every way..... except for the thermal drift. Tuned up with key down, 300W out with 12W drive, within a few seconds it droops to under 150W. Keeping the power up requires *constant* re-tuning of the plate. The drift is so fast I think it must be within the tube or close to it, there just isn't time for the tank circuit to heat up. I don't know if I made a mistake in the engineering of the tank circuit, or if the tube is faulty Open to all ideas about how to fix it. Thanks Tim G4LOH
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Gi46b on 2m - Thermal drift problem -Sorted
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Sorted! Changed the blocking cap and replaced the muffin fan with a blower big enough for a GS35. Power 350W drifts down to 330W after about 30 seconds, but that could just be the driver power changing. Thanks for the helpful comments here :-) 73
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KW1000 amp renovation, filaments, bias and neutralization.
I recently acquired a British KW1000 linear which uses a pair of 572Bs and is somewhat similar to the SB200. The power transformer was missing but I have been able to fit a replacement from the junk box, it has 2 x 6.3 volt 4 Amp winding with no centre tap so am thinking of connecting the filaments in series. The first problem with this is one tube light up brighter and had 7 volts, the other 5 volts (these were old tubes, one Centron, the other Taylor). When I tried a newer matched pair from Penta the voltages were quite close. Looking at the schematic for my TL922A I see the CT is connected to the linked filament pins via a 80 uH choke where the drive appears to be applied, although there is also a 0.01 uf capacitor whose purpose is unclear to me, across to one side of the main choke (22 uH). Any advice would be appreciated, also is any bias required in tx and is there a need for neutralization? - am directly grounding the grids. The KW1000 has a few additional turns on the filament choke which goes to a flat plate about 1" square and close to one of the tubes. Mike VK2AMF / G3XEF. Mike Fleetwood Canberra Australia and Sidcup UK. Worldwide email address is: mfleetwood@...
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AL-80B fan
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Hi all, I'm going to help a friend replace the fan in his AL-80B amp. Is this an hour job or do I need to count on a half day or so? Thanks, Bob W4JFA
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AL80-B tuned input
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The 2 prior posts are a perfect segue into my question. My input SWR on 30 is over 3 to 1 and 12 meters is about 2 to 1. The rest seem ok. I have searched high and low for instructions on the proper method to tune the input slugs. I know there will be compromises between 20/30, 15/17 and AUX output per band. Do any of you guys have a simple way to adjust the slugs to get the input SWR down to a better place? I'm lost here. Thanks and 73 Warren / NI5L
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30L-1 ALC
What negative voltage ranges should a find in this amplifier¡¯s ALC circuitry? I know it depends on the setting of the pot. Just curious about what variation I should see. Richard WB5NEN
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Tim and anyone interested : Here¡¯s looking inside the RF box. You can see the original blocking cap - just like yours ! This is a YU1AW ¡°Lazy Builder¡± design. Suited my construction capabilities perfectly ! You can see the thick Teflon sheet insulation between the tune (right) and the¡±load¡± caps. I was so dumb back then, I thought I could adjust the loading like a HF triode amp. As Lou said, we all still learning about amps. The lower pic shows the RF box inside the amp cabinet. The large blower feeding cooling air into the bottom of the RF box, Russki REW14 input and output relays, many 6A10 diodes for operating bias, toroidal filament tranny, metering, etc. are visible. The only other stuff up I made was not using proper terminated cables for the input and output N-Type connectors. I¡¯ll fix that soon. Good luck with it, and let us know how you go. Cheers, John VK6JX
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Tim - here¡¯s what happened to my 2200pF blocking cap. Cracked and a little burnt. This caused ALL of the ¡°thermal¡± power output drift in my 2m amp. She¡¯s rock solid now, for complete JT65B overs. Love it ! John
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[Amps] [ham-amplifiers] Fw: [yccc] Followup: KM1H
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We are always learning! Sent from the all new AOL app for iOS
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Fw: [yccc] Followup: KM1H
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Sent from the all new AOL app for iOS Begin forwarded message: On Tuesday, December 26, 2023, 3:43 PM, Rudy Bakalov <r_bakalov@...> wrote: ----- Forwarded Message ----- From: Doug Grant <dougk1dg@...> To: YCCC <[email protected]> Sent: Tuesday, December 26, 2023 at 03:38:10 PM EST Subject: [yccc] Followup: KM1H Since nobody had any direct info on Carl's status, I drove to his house and knocked on the door today, not quite sure what to expect. Carl's ex-wife answered the door and invited me in. She announced me to Carl, who then made his way down the stairs . We had a nice visit and yakked for about a half-hour. He knew me, and even asked how my "twin" (K1AR) was doing. He was unaware that his ham license had expired, but at age 83, sometimes events like that slip by. So now you know "...the rest of the story". 73, Doug K1DG
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The Subject is kind of vague but I have a AL-80B. I have no issues on 75-15m. The 15M Tuned Input is a little off, maybe they tuned it to 17M. On 10M when starting tune up process and I get to about 50Watts I smell a hot smell. 40 Watts of Drive,Grid Current is 85 and Plate Current is 350 Output Power is 490W NO SMELL But when I get to 50Watts I start smelling a HOT, Plastic Smell, the more drive I give it the worst it gets. @ 50Watts of Drive, Grid Current is 110, Plate is 378 Output is 615W Any Ideas where to start looking for this problem??? Next Problem on 160M 40Watts of Drive, Grid Current is 70, Plate is 300 Output power is 430W No Smell When I get to 70 Watts of Drive I smell a different smell, Like a component breaking down. When I key with 70Watts of Drive I see 148 of Grid Current that falls to 130 pretty fast. Plate current holds at 350 with Output power starting at 739 and dropping to 660 pretty fast as well. It smells almost like your heat does when you turn in on for the first time in the winter but its different that the 10M smell... Any Ideas? The other bands work perfect... Not Issue no matter how long I use it. Thanks for you help. Sorry if descriptions are off, any help will be appreciated. 73 K4MDI Scott
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Merry Xmas to all
Have a good one, fellas. Best wishes for a happy and safe 2024. Mni 73, John VK6JX
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12 KW CCS ON 160-15M...USING THE 3CX-6000A7... PART 9
Here, the paralleled pair of Jennings RJ2B output vac relays are installed.....along with the 7-16 DIN output connector. Also installed is the 1/2" silver plated tubing coil, used for 20 + 15m. Also installed is the hb 3/8" tubing coil, used for 80+40m. The hb cu discs are cut and installed for the vac tune and vac load caps. The hb 1/4" tubing coil (used for 160m) is wound, but not yet installed, nor the 100mm diam Draloric plate block cap. On the rear apron, you can also see the pair of 100 amp, superior electric ...'supercon connectors', used to terminate the cables for the 7.0 vac @ 78 amp fil supply. It's progressing pretty good. The entire B+ supply has yet to be built... but is a straight forward project, since it's already been done several times before. https://www.youtube.com/watch?v=ZdQU5HuonqA
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Good morning, all. I recently acquired a converted 6-meter amp that is named the SB-206. It was converted by KM1H in 2006 from an SB-200 and it actually works very well. I have been very carefully tuning it with the max output method, which is the only way I can do it. The "manual" is a single sheet of paper with minimal instruction. I have tried to contact the builder, but his email bounces and his phone is disconnected. Has anyone on this reflector had one of these? If so, I would like to know how you tune your amp properly. I am trying t avoid killing it with improper tuning. 73 Warren / NI5L
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commander 2500 amps
Can anybody with a two tube 2500 Commander ( those with grid trip protection) tell me at what grid current their amp trips out at? I have an older model in for work and it doesn¡¯t have a grid trip. I put a trip circuit in it and wanting to adjust the trip point to factory specs. Schematic had a notation 65ma max., but that might be for a single tube. If anyone can let me know what their¡¯ sis set to I¡¯d like some input. Thanks, Lou Sent from the all new AOL app for iOS
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I have recently acquired a Ten-Tec Centurion model 422 that is in very nice condition, but has a blown up bandswitch and the plate tuning capacitor was arced. I might be able to salvage the capacitor, but the bandswich will need to be rebuilt or replaced. If anyone has a switch/parts and/or a capacitor please contact me off list to let me know what you have.
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Henry roller inductor
I have a bad roller wheel on a 3K roller inductor. Anybody have a replacement or know of a replacement? Lou Sent from the all new AOL app for iOS
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AL-80B cooling
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Hi all, I'll condense this. A friend just got this AL-80B that had at one time melted a filament tube pin. The tube socket, the type that the socket is on a circuit board, was burned pretty badly. He got a new ceramic socket. I did what I needed to do to install it including getting the grids grounded, socket properly mounted etc. Amp works fine now but I noticed the cooling fan is basically silent and seems to barely spin. When holding my hand on the output vent I barely feel any air movement. I've never worked on one of these 80B's before so I don't know what's normal, however I feel this isn't moving nearly enuff air. I know this is hard to put into words but can anyone give me some kind of idea of how much air can be felt blowing out of the vent? I know the fan worked normally at one time because the inside of this amp was full of dust etc! Actually it was disgusting! It took me quite a while to get it clean. Thanks all. Bob W4JFA
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Replacement 3-500ZG
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Hello Group, I could use your help! Looking to pick up a 3-500ZG replacement for my AL-80B. My choices are: RF Parts Company: 3-500ZG (6-month warranty). 250$ (China) DX Engineering: Penta Labs RF Vacuum Tube 3-500ZG (no warranty listed). 300$ (assume China?) DX Engineering: Ameritron 3-500Z Replacement Power Tube (All products manufactured by Ameritron have a one-year limited warranty) 360$ (assume China?). Both vendors have always been reliable for me so my question: Is the Ameritron tube worth the additional $$ or is it branding? Is the Penta Tube worth the additional $$ What would be the best replacement? (sorry for writing a novel) Thanks in advance! 73 K5AKM - Dave
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Hopefully someone will help me out. I have 3 LD-4513 Traveling Wave Tube amplifiers. These I think operate around 2400MHz. I would like to get some information on them. A search on Google doesn't seem to come up with anything on this particular device. 73, Clint, VE3CMQ
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