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I've built many EHT supplies over decades but have always used capacitive only, ripple-filtering. Sitting below my desk for many years, is an inductor rated 7,500V, 0.85A CCS, 10 Henries. It came from an industrial RF heater. I've never seen one used in an EHT ham amplifier supply...has anyone experience of this? 10H, even with just 1uF after it, has a -3dB frequency of 50Hz, so it would be pretty effective at 300Hz (3-phase, full-wave ripple). But how would the inductive ripple filter respond with an SSB load? What happens if the tube flashes over? Are some extra protections required? Thanks Tim
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8410/9500 Wattmeter Failure
9
I have an 8410; however, according to the schematic(s), it appears as if it probly uses the same wattmeter as the 9500. The other day, I encountered intermittent flashover in my external antenna tuner while running around 1100 watts on 160; it would cause all the reflected power LEDs on my 8410 to light up. I managed to finish working someone, let the amp cool down for five mins, then shut it down. All front panel indicators appeared to work properly at that time (although I've never, ever, seen a grid current LED light up, nor the FAULT LED even though I once did have a real fault where I thought that LED SHOULD light... but it didn't). The output power and reflected power indicators have always been very accurate and worked fine. Later that day, I fired it up again... and was chagrined to find NO output power indicated on the front panel LEDs... neither forward nor reverse. But the amp was still amplifying normally; output power on an external wattmeter indicated full power out. I fired up the AE9K Alpha Monitor program and it, too, shows no output power. But the amp does still have full output power; so something common to both forward and reverse power that drives the front panel display failed in my amp. When the tuner flashed over, my external LP-100A power meter usually indicated something really high like over 2500 watts momentarily.. once, I think I saw 2932 watts indicated ===8-O Since then, I've fixed the tuner problem... but have no output power indication on either the amplifier front panel, nor with the AE9K Alpha Monitor program, even though the amp is actually still correctly putting out full power. I'm now printing out all 19 pages of the schematics, but an eyeball perusal in Acrobat hasn't yet identified exactly which connector carries the output of the tube deck to the TR system and what it plugs into on another schematic page. Meanwhile, I thought I'd ask here, in case someone else has already "invented the wheel" and fixed this kind of problem. Any help? TNX, Steve K0XP
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Hi, I am looking for Bandswitch Rear Wafer E4C-N18 for my Alpha 78. Anybody in the group either has one for sale or know where to buy it? Thanks 73 de Arturo, LU6ETB
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I'm currently fabricating several versions of ferrite bead loaded plate chokeS. I used 1" OD, hollow teflon tubing (.145" wall thickness) (.710" ID). Each of the .687" OD beads (type 61) was shimmed with tape, so they make a snug fit, when stuffed into the hollow teflon tube. A 1" electrolytic capacitor bracket is used to hold the base of the choke to the chassis. 1/2" copper straps wrapped around the hollow teflon tube, and machine screwed with a single brass 8-32 machine screw etc. A 1/4" to 3/8" hole is drilled into the amplifier chassis, to allow compressed air in the plenum, to flow up though the .374" ID of all the beads. Easy way of air cooling. Actual top temps will be taken with a fluke 62 IR. The actual winding is made from 22 ga, silver plated, stranded teflon wire. Insulation is pretty thick, and the OD of the wire is exactly .060". ( wire inside is only .028" OD) Upper + lower winding terminated on the upper / lower straps, then soldered. Lower strap is 1" from the top of the electrolytic bracket. That provides 1" of exposed teflon. On paper, should be good for 10 kv of...'surface creep'. After measuring the inductance with my LCR meter, it was time to see where the 2 x series resonance freqs are located. I used the S11 output, then a single provided coax cable to a (SMA female / BNC female adaptor)....then the BNC plugged into a dual binding post fitting, with it's BNC male connector built into the bottom end. Then 1 SHORT test lead to top of choke...and the other test lead to bottom o f choke. Test leads have an alligator clip at one end...and other end is a banana plug. Did the usual open / short / 50 ohm calibration. Ok, found the 2 x series resonance freqs asap...on both HB chokes. ( I also compared to a new Ameritron choke, since I know where the 2 x series resonant freqs are on the Ameritron choke). I had the chokes being tested, laying on top of my bed mattress...along with vna etc. I then placed the choke on Styrofoam, so only the extreme ends of the choke were supported, in the horz plane. 90% of the choke, and all of the winding was in mid air. Well that was a surprise. The series resonant freqs INCREASED in freq by a bunch. Instead of 19.002 mhz laying on the bed, it was 19.750 mhz, when in mid air. Same deal with the upper series resonant freq (aprx 32 mhz...which also increased). I also stood the chokes vertical on the bed, and supported the very top of the choke with the handle of a wooden spoon...same deal. Resonant freq increased by 748 khz. I can see getting any plate choke near an aluminum sidewall, or large metal triode tube, can easily lower the resonant freq, but not laying on a bed mattress. I also held my hand parallel to the choke, and once 2.5" away, resonant freq decreased, and decreased more, the closer the palm of my hand got to the choke. W8JI warned about getting plate chokes too close to any dielectric or insulator. He is correct...I shoulda listened. Next up, knowing all this, is to replace the 3/4" wide copper straps with 1/2" wide copper straps...and rewind the choke. That will allow for an extra (.5" / .060") 8.33 turns. The idea here is to lower the 1st series resonance point, (19.750 mhz) so it's midway between 21.000 mhz....and 14.350 mhz. (midpoint is 17.675 mhz). The new 3x6 linear amplifier is not used on the 17m band (18.068 mhz to 18.168 mhz) nor is it used on 12 + 10m bands. We have height constraints, so the completed choke is exactly 8.25" tall. (Top lid is exactly 9.25" above the chassis). The existing 5" winding will be increased to 5.5"..... by fabricating the new 1/2" narrower straps. Wish me luck. Existing choke measures 315 uh....which will increase a bit once the extra 8 turns are added. On choke #2, it's a full 12" tall, and uses a 8.75" winding. Measures 750 uh. Resonates at 9.7 mhz...and also 17.8 mhz. I will try the narrower 1/2" wide straps...so I can get another 8.33 turns on it. (Then the new winding will be 9.25" and uh will increase a bit). The idea here is to lower both series resonant freqs a bit. Midpoint between 14.350 mhz and 18.068 mhz is 1
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Retrofit for remote operation of tube amplifiers
Does anyone make a retrofit module for tube amplifiers that can monitor key parameters remotely, ideally via Ethernet. I could build something but if something is available ready-made, I would rather save the time. For now, I could use an IP camera for the metering, but they are noisy and not ideal for an EMEr such as I. A long shot I know. 73 Conrad PA5Y
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572's
5
I've got a friend who needs 572B's for his SB200. He's ready to buy the PSVANE tubes on Amazon for $149.99/pair. I see that RF parts is selling Svetlana's for $200/ea. He's a SSB rag chewer so no heavy digital use. Money is tight for him. What's the story with 572's now? Jim - KR9U
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Does anyone know of an after market plate current meter for the Kenwood TL-922? Any leads appreciated. 73, Alek VK6APK.
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Transformer "burn-in"
7
Hello all. I have a brand-new Peter Dahl clone transformer from Hammond coming for my Alpha 99. I am wondering if I need to condition it or burn it in prior to using it at full power. I don't want to fry a $1000 transformer due to ignorance. 73 Warren / NI5L
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Hi, Hoping someone can look at the pictures of my amp and suggest why it is oscillating? It's a PA3CSG design for 432MHz. I thought I had built it quite well, but on power up, as soon as the EHT appears it oscillates with about 500W RF showing on the meter into the load. I've checked (cold) with the VNA and dummy resitors that both cathode and aode circuits tune perfectly on 432MHz. EHT is 4kV Bias 27V Thanks G4LOH
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Palstar 2500 repair
4
Hello everyone New to this list. I'm trying to repair a Palstar 2500 ( non export 2 tube ) dated 2009. I bought the amp in non-working condition. When I first opened up the amp I noticed the plate block caps were blown. I have since replaced them with equivalent to what was in there but have heard that HEC caps would be a good choice. In checking around in the amp I also see some diodes shorted..SM84A diodes which are rather large for SM components. IN5408 were recommended but these are fairly large so may look for another alternative...I can't find the SM84A anywhere For now , I am just trying to get the amp running and it's taking some time. I'm not an expert with amplifiers and am being careful but am learning. Right now the tubes are removed and the HV transformer is unplugged. I think there are some issues deriving from the control board. I'm trying to learn from the schematics and there are some voltages that are supposed to be present that I'm not seeing, or voltages that are on different pins ( where the connectors attach ) that go to the tuned input board as well as back to the PS board. One is 30VDC that I can't find on the connector and am not too sure what it is for...from the schematic...it seems to be pointing to the TR relays on the input but these are 12V ..I have the control board, meter board and PS board removed and am trying to learn the amp from the schematics while comparing it to the boards. There is no component listing or board layout in the manual and it's a layered board. There are some notes on the schematic and the PO also changed some wiring around on the IDC connectors, this is also making things rather confusing. I have bought some new IDC connectors but need to trace out the wiring and make sure the correct control voltages are getting were they should be Is anyone on here familiar with this amp?...I understand it was a redesigned Commander 2500..I know this message likely does not contain all the pertinent info , but I just thought to reach out to see if anyone is familiar with it for a start 73 Brian
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For all you tire kickers out there.
3
This cracks me up. https://music.youtube.com/watch?v=NGR20B2cEBQ
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For your continued amusement
Sex life of an electron.....by Eddie Currents One night when his charge was pretty high, Micro-Farad decided to seek out a cute little coil to help his discharge. He picked up Milli-Amp and took her for a ride in his Megacycle. They rode across the Wheatstone Bridge and stopped by a Magnetic field with flowing currents and frolicked in the sine waves. Micro-Farad, attracted by Milli-Amp¡¯s characteristic curves, soon had her fully charged and proceeded to excite her resistance to a minimum. He gently laid her at ground potential, raised her frequency, and lowered her reluctance. With a quick arc, he pulled out his high voltage probe and inserted it in her socket, connecting them in parallel. He slowly began short circuiting her resistance shut while quickly raising her thermal conductance level to mill-spec. Fully excited, Milli-Amp mumbled ¡°OHM¡OHM¡OHM!¡± With his tube operating well into class C, and her field vibrating with his currently flow, a corona formed which instantly caused her shunt to overheat just at the point when Micro-Farad rapidly discharged and drained off every electron into her grid. They fluxed all night trying various connectors and sockets until his magnet had a soft core and lost all of its field strength. After wards, Milli-Amp tried self-induction and damaged her solenoids, and, with his battery fully discharged, Micro-Farad was unable to excite his field. Not ready to be quiescent, they spent the rest of the evening reversing polarity and blowing each other¡¯s fuses.
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New Command Tech. Commander power supplies ready.
The newly designed power supply boards I mentioned a few weeks ago are now ready. These are a replacement power supply boards that fit the One and two tube HF Commanders and the one and two tube 6 meter amps. The new technology boards are much more robust than the older original boards that have deteriorated over time. The new boards have all of the features of the old boards plus 5000 hour 105 degree electrolytics, RF bypassing and series metering resistors that should not drift and fail over time!!! I have been unable to rebuild original boards due to trace¡¯s flaking off the board and had to do something to save these amps! Contact me at gudguyham@... for further information. Boards are built and tested and ready. Limited supply at this time as more will be on the way. Thanks, Lou Sent from the all new AOL app for iOS
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recently purchased an unfinished HomeBrew 2x3-500 amp. power supply is great & tested now. Chasing wiring on RF deck and noticed the filament transformer is placed next to output relay / loading capacitor. This looks like recipe for trouble.... Time for layout change? Robert W5AJ PHOTO LINK
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GS35B anode to chassis C ?
I need to know asap.... what is the C between the anode and grid of a GS35B....when plugged into a socket. Typ, when they spec tubes like triodes in GG, they spec anode to grid C..... BUT that always rise a bit, when plugged into the grid ring...due to the proximity of the lower anode fins...to the chassis below the lower fins. I'm designing a PI network for a fellow....and don't have a GS35B in my shop. Does anybody know, or can measure the anode to chassis C on their GS35B tube amp for me ? In the case of an existing amplifier, the anode lead to the plate choke needs to be temp disconnected....and ditto with the RF connection, from anode to plate block cap assy. It would be much appreciated.
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I am thinking of adding a tuned input to one of my amps. Does anyone make a board? I searched around and there seems to be nothing available. Does anyone have a board laying around? Maybe from an amp supply or ameritron? I saw there is a nice 200w low pass filter board with relays. I guess I could repurpose it and make it a tuned input. It needs to be relay switched. I have control voltages for 5 bands.
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Repost added pix: Rebuilding another LK cap here and another Plate Tuning cap with nasty pits and therefore....arcing. Any info to secure those rotor and stator plates appreciated. Rich k0zx
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Groups IO Reverification Message
If you haven't done it yet, please log in to groups.io. This will let their servers know your account is still active. If you don't, you will stop receiving e-mails this weekend and be removed from all your groups in February. You should have received an e-mail explaining this. Logging in one time reverifies ALL your groups. Here is what I, as an owner, received today... You are receiving this email because you are an owner or moderator of one or more Groups.io groups. We are in the process of reverifying some of our users and we wanted to make sure you knew what was happening and why. For more detail about this, please visit the Reverification FAQ, at /static/reverifyfaq On Saturday January 13th, 2024, an anti-spam service called Spamhaus labeled one of our email servers as a spam sender. This caused any email service that uses Spamhaus to stop accepting email from our server. Because of this, we began a reverification process and sent out reverification emails to a subset of our users on Sunday January 14th. Spamhaus lifted their block on Monday, January 15th, 2024, but we need to continue the reverification process. You can see which, if any, of your users are affected. Go to the Admin section of your group and look at the Members page. Next to each user's email, there may be a badge with the letters RI or RS. RI means the confirmation/reverification is in progress, but has not been completed. RS means the confirmation/reverification has been successfully completed. Here are the next steps in the reverification process: On Sunday, January 28th, group emails to people in the RI state will be disabled. Messages from moderators and login link emails will still work. Until February 11th, people will still be able to reverify themselves and the RI and RS badges will still show up in the Members page. After that, members still in the RI state will be removed from groups. The activity log entry will be Membership - Member Removed, with the added reason of reverification failed. For domains where no reverifications happened, no invites or direct adds will be permitted going forward. If there is a valid person on one of those domains, they should contact [email protected] to have the domain ban lifted. We apologize for the inconvenience this process may cause, but it is necessary to ensure that we are able to continue delivering group email reliably. Thank you for using Groups.io. Best Regards, The Groups.io Team
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Rebuilding another LK cap here and another Plate Tuning cap with nasty pits and therefore....arcing. Any info to secure those rotor and stator plates appreciated. Rich k0zx
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Brand new updated PS board for Command Technology amplifiers
4
Recently I had occasion to have to rebuild THREE power supply units ( located under the chassis) of the Commander line of amps. Two HF2500¡¯s and one VHF2000. Both use the same power supply board. Unfortunately all 3 boards were damaged by heat and the traces flaked off the boards in many spots. The traces that didn¡¯t lift normally did when tried to unsolder and resolder new parts. The old boards are basically unsalvageable to rebuild. The boards are obviously old technology. They are a one time board as far as I¡¯m concerned! As usual confronted with the need, I¡¯ve developed a brand new board using new technology on boards with masking etc. I need these boards to professionally rebuild the power supplies in these amps. I don¡¯t trust Gerry rigging these old decrepit boards. The whole amplifier RF deck must be removed from the amp chassis to get to the power supply. You don¡¯t want to go back on after using band-aid methods on the old boards. These amps are terrific amps and can go another 35 years with the breath of life from an all new board. Hopefully within the next month I will have these boards ready. I ordered extra for my supply for further repairs and for those who would like to attempt their own replacement I will have a limited supply I¡¯ll be offering them fully assembled and ready to install The price is unknown at the moment until I can fully asses the expenditure. If interested I¡¯ll take orders on a FCFS basis. I¡¯m going to be installing one in my own personal amp as well. I have my own transformer for testing so if you don¡¯t feel confident in doing the replacement yourself I only need the RF deck and can do it here. It¡¯s a shame to see these good old amps sidelined for lack of parts. Thanks for reading Lou Sent from the all new AOL app for iOS
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Sat 8:39am
Sat 8:39am