Re: High Temperature in Toroid of the PI-L network (Alpha 78)
Well, that's no surprise.
Don't run any more than 30% of maximum power in FT8 mode. That
goes for radios and amplifiers.
Stick to that and you'll never have a problem.
73, Alek VK6APK.
On 3/03/2024 12:55 pm, Arturo LU6ETB
wrote:
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Hi,
Last week my Alpha 78 stopped working.
I found the windings of the L5 was burned.
I rewinded the toroid with new wires.
Now, it is working.
I checked the temperature after transmitting on 80 meters FT8 with
approximately 1 KW output.
Plate current 0.85 Amper, HV 2000 V and Grid current 25 mA.
After 30 minutes the temperature readings with a digital
multimeter were.
L5 119 C (246 F)
L4, 64 C ( 147 F)
L6, 49 C (120 F)
Are those temperatures right?
What maybe the cause of the high temperature?? ?
Should I have to replace also
el toroid???
?
Thanks in advance for the comments.
73 de Arturo, LU6ETB
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Re: High Temperature in Toroid of the PI-L network (Alpha 78)
I just read through the entire manual.??
On data modes, like FT-8, that amplifier HAS to be operated in the LOWER 1400 vdc? B+ position. And no? more than 1 kw dc input (aprx 500-650 watts PO).?
IE:? 1400 vdc @ .710 amps? (= 1 kw DC? INPUT).? ?I would suggest no more than 600-700 ma on FT-8.?
DO NOT run it in the SSB / 2100 vdc position.? ?You will just overheat the L5 toroid again.? ?L5 is used on 160-80-40m.?
I would use the manual tune (instead of the broadband tune).?
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Re: High Temperature in Toroid of the PI-L network (Alpha 78)
FT8 is a 100% duty cycle mode and at some point depending on wire size and physical size of the toroid it will at some point overheat. ?It it overheats too much the permeability of the core itself will change and rewiring it will change the actual inductance. ?I had the toroid in a Commsnder 2500 catch on fire and totally destroyed for running 1500 watts RTTY. ?I a customers amp that is. ?It¡¯s the nature of the beast that it will eventually burn up at some point .
On Saturday, March 2, 2024, 11:55 PM, Arturo LU6ETB <lu6etb@...> wrote: Hi, Last week my Alpha 78 stopped working. I found the windings of the L5 was burned. I rewinded the toroid with new wires. Now, it is working. I checked the temperature after transmitting on 80 meters FT8 with approximately 1 KW output. Plate current 0.85 Amper, HV 2000 V and Grid current 25 mA. After 30 minutes the temperature readings with a digital multimeter were. L5 119 C (246 F) L4, 64 C ( 147 F) L6, 49 C (120 F) Are those temperatures right? What maybe the cause of the high temperature?? ?
Should I have to replace also el toroid???
?
Thanks in advance for the comments. 73 de Arturo, LU6ETB 
|
High Temperature in Toroid of the PI-L network (Alpha 78)
Hi, Last week my Alpha 78 stopped working. I found the windings of the L5 was burned. I rewinded the toroid with new wires. Now, it is working. I checked the temperature after transmitting on 80 meters FT8 with approximately 1 KW output. Plate current 0.85 Amper, HV 2000 V and Grid current 25 mA. After 30 minutes the temperature readings with a digital multimeter were. L5 119 C (246 F) L4, 64 C ( 147 F) L6, 49 C (120 F) Are those temperatures right? What maybe the cause of the high temperature?? ?
Should I have to replace also el toroid???
?
Thanks in advance for the comments. 73 de Arturo, LU6ETB 
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Re: Kudos to Digi Key and Hammond Mfg.
On Fri, Mar 1, 2024 at 01:57 PM, Dave w6de wrote:
How do you find the Peter Dahl transformer listings on Digi Key?? Or any US seller?
Trying to find the price to decide on a tube switch for an Alpha 76PA 3-tube amp.
73,
Dave, w6de
DigiKey sells the Hammond transformers, but does not stock them. They are ordered through DigiKey, and then shipped direct from Hammond.
First, you look up the listing of Peter Dahl transformers: HERE:
Find the transformer you want, and click on the part number you want, then copy (or write down) the "Hammond Part No." from that site...
  Then go to the DigiKey website (HERE:) and enter that "Hammond Part Number" for the transformer you want into the "Enter keyword or part #" box at the top of the page, and click the search button. The detailed info for that specific part will come up, at which time you can enter a quantity and hit "Add to Cart".? Then check out!
 
I think you need an account & Login info with DigiKey, but you can do that at checkout.
? -- 73,
~Alan
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Re: Yaesu FL-2100B Key Line Polarity
On Fri, Mar 1, 2024 at 09:29 AM, Jim VE7RF wrote:
I would toss the 1/2 wave rectifier......and replace it with a FWB.? ? Then bond the negative to the chassis.? ?A 1/2 wave rectifier is abt the stupidest thing I have ever seen.? You end up with DC current flowing through the xfmr secondary winding on 1/2 cycles.
About the only thing a 1/2 wave rectifier is good for is...... it's the basis for a FWD.? ?A FWD? (full wave doubler) is just 2 x 1/2 wave rectifiers in series.?
? Agree 100% Jim. I've got some nice little 3-amp FWB rectifiers. I'll toss the single diode and stick an FWB in, along with a fresh cap.
-- 73,
~Alan
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Re: Original GM3SEK/G3SEK Tetrode Boards
It's two?boards. One for control & the other for bias voltages.
On Fri, Mar 1, 2024, 20:15 Steve < k0xp@...> wrote:
Are there more than one set of boards: i.e., are you selling
multiple sets of boards for multiple amplifiers??
Or is this just one amplifier-set of boards?
TNX,
Steve K0XP
On 3/1/2024 6:48 PM, Mark Schoonover
via wrote:
Boards are 95% assembled and configured for 4-250A
tubes. If you plan on using different tetrode tubes, you'll need
to do the math outlined in the printed manual I'm including.
Includes R14 wire-wound adjustable resistor, heatsinks &
mounting hardware for TO220 transistors, off-board connectors,
500-ohm wire-wound pot, 5k 50W chassis mount resistor, remaining
discrete components, and Stancor P-8671 117V 50-60hz/36v/1A
transformer. I can provide photos of the boards. I am asking
$550 + Shipping. Send your zip code, and I'll calculate the
final cost. I prefer Zelle/Venmo and USPS money orders, too. No
PayPal. All items are sold as-is with no returns.
73! Mark KA6WKE - DM34st
Website:
Youtube:
--
See my QRZ.com page at
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Re: Original GM3SEK/G3SEK Tetrode Boards
Are there more than one set of boards: i.e., are you selling
multiple sets of boards for multiple amplifiers??
Or is this just one amplifier-set of boards?
TNX,
Steve K0XP
On 3/1/2024 6:48 PM, Mark Schoonover
via groups.io wrote:
Boards are 95% assembled and configured for 4-250A
tubes. If you plan on using different tetrode tubes, you'll need
to do the math outlined in the printed manual I'm including.
Includes R14 wire-wound adjustable resistor, heatsinks &
mounting hardware for TO220 transistors, off-board connectors,
500-ohm wire-wound pot, 5k 50W chassis mount resistor, remaining
discrete components, and Stancor P-8671 117V 50-60hz/36v/1A
transformer. I can provide photos of the boards. I am asking
$550 + Shipping. Send your zip code, and I'll calculate the
final cost. I prefer Zelle/Venmo and USPS money orders, too. No
PayPal. All items are sold as-is with no returns.
73! Mark KA6WKE - DM34st
Website:
Youtube:
--
See my QRZ.com page at
|
Original GM3SEK/G3SEK Tetrode Boards
Boards are 95% assembled and configured for 4-250A tubes. If you plan on using different tetrode tubes, you'll need to do the math outlined in the printed manual I'm including. Includes R14 wire-wound adjustable resistor, heatsinks & mounting hardware for TO220 transistors, off-board connectors, 500-ohm wire-wound pot, 5k 50W chassis mount resistor, remaining discrete components, and Stancor P-8671 117V 50-60hz/36v/1A transformer. I can provide photos of the boards. I am asking $550 + Shipping. Send your zip code, and I'll calculate the final cost. I prefer Zelle/Venmo and USPS money orders, too. No PayPal. All items are sold as-is with no returns.
73! Mark KA6WKE - DM34st
Website:
Youtube:
|
Re: Kudos to Digi Key and Hammond Mfg.
I bought one last year from? them,10 week wait and total cost was about 1K.?
?? 73s Bob W5RG
On Friday, March 1, 2024 at 01:57:47 PM CST, Dave w6de <w6de@...> wrote:
How do you find the Peter Dahl transformer listings on Digi Key??
Or any US seller?
?
Trying to find the price to decide on a tube switch for an Alpha 76PA 3-tube amp.
?
73,
Dave, w6de
?
From: [email protected]
<[email protected]> On Behalf Of Alan - W5ARM via groups.io
Sent: 1 March, 2024 01:19
To: [email protected]
Subject: Re: [ham-amplifiers] Kudos to Digi Key and Hammond Mfg.
?
Yessir!? Hammond Mfg. and DigiKey are great resources.
I've ordered a couple of their Peter Dahl transformers, and they make a first-rate product! Pricing was fair enough, and they shipped quickly.
The listing of transformers is extensive, and the documentation is great. Find the one you need, copy & paste the P/N into DigiKey's main site to order, and you're done (well... after you pay).
Hammond/PWDahl Transformers are HERE:
--
73,
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Re: Kudos to Digi Key and Hammond Mfg.
How do you find the Peter Dahl transformer listings on Digi Key??
Or any US seller?
?
Trying to find the price to decide on a tube switch for an Alpha 76PA 3-tube amp.
?
73,
Dave, w6de
?
toggle quoted message
Show quoted text
From: [email protected]
<[email protected]> On Behalf Of Alan - W5ARM via groups.io
Sent: 1 March, 2024 01:19
To: [email protected]
Subject: Re: [ham-amplifiers] Kudos to Digi Key and Hammond Mfg.
?
Yessir!? Hammond Mfg. and DigiKey are great resources.
I've ordered a couple of their Peter Dahl transformers, and they make a first-rate product! Pricing was fair enough, and they shipped quickly.
The listing of transformers is extensive, and the documentation is great. Find the one you need, copy & paste the P/N into DigiKey's main site to order, and you're done (well... after you pay).
Hammond/PWDahl Transformers are HERE:
--
73,
|
Re: Yaesu FL-2100B Key Line Polarity
I would toss the 1/2 wave rectifier......and replace it with a FWB.? ? Then bond the negative to the chassis.? ?A 1/2 wave rectifier is abt the stupidest thing I have ever seen.? You end up with DC current flowing through the xfmr secondary winding on 1/2 cycles.?
?
About the only thing a 1/2 wave rectifier is good for is...... it's the basis for a FWD.? ?A FWD? (full wave doubler) is just 2 x 1/2 wave rectifiers in series.?
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Re: Yaesu FL-2100B Key Line Polarity
That¡¯s true, once you bias the cathode instead of the grid you no longer need a negative voltage. Lou
On Thursday, February 29, 2024, 9:52 PM, Alan - W5ARM <W5ARM.mail@...> wrote: Hi Louis,
Thanks for the reply.? As I said, I can't see where the polarity change would create any problem, and sounds like you've had the same experience.
Appreciate the info!
-- 73,
~Alan
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Re: Yaesu FL-2100B Key Line Polarity
Hi Louis,
Thanks for the reply.? As I said, I can't see where the polarity change would create any problem, and sounds like you've had the same experience.
Appreciate the info!
-- 73,
~Alan
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Re: Yaesu FL-2100B Key Line Polarity
Alan, lately that¡¯s all I do with the FL2100 and SB200 amps. ?I do solid grounded grids on both. ?Change to cathode bias doing away with those awful grid resistors . ?I change to a low v current 12v relay so no soft key is needed. ?With the 2100 I switch to positive keying . ?No issues at all. ?The FL2100 jumps its output to 800 on some bands with good tubes. ?The SB200 goes to 900 watts output. ?Instead of it sweating to make 700 watts it just loads at 700-800. Well worth it.
On Thursday, February 29, 2024, 8:01 PM, Alan - W5ARM <W5ARM.mail@...> wrote: Howdy Folks,A quick question (and maybe a stupid question... but):
Can anyone see any issues in reversing the polarity on the key-line circuit (from "positive ground" to "negative ground") on the FL-2100B amp? Has anybody attempted this?Background:I'm refurbishing an FL-2100B, and have already done some upgrades and mods: New PS diodes, cap's & boards (from Harbach); Directly-grounded the grids; Performed the "Self-bias mod" (CT of filament xfmr grounded thru a 100k resistor on RX, grounded on TX thru a separate/new cube relay); Installed a new band switch (original was burned on 80m capacitor contacts), and some other general clean-up.
Currently, the key line is "positive ground" (utilizing a simple, single-diode 1/2-wave rectifier and 1000uF cap). The positive side of this DC circuit goes to the chassis ("ground"), and negative side to the keying relay. Thus, when the RCA jack is shorted to "ground" by a transceiver, it is actually switching the "positive" side.? I have read elsewhere that this "reversed" polarity could cause issues with some "modern" transceivers which require a "negative ground" key-line circuit (particularly those employing solid state/transistor switching), and therfore requiring the use of an external key-line "buffer" (which I have built and used succesfully).Anyway, since the bias-circuit no longer has anything to do with the keying relay circuit, any issues that anyone might be aware of, by reversing the polarity?? I've studied the circuit schematic (and corrected it, as per my other changes), and I can't see anything that would prevent this from working. Since doing that bias mod, the key-line power supply only supplies power the key-line relay, and has nothing to do with bias.The key circuit currently runs at 19 volts (open circuit) and 280 mA keyed.
Ultimately, this amp will be put up for sale, but I wanted to do the upgrades & mod's before I put it up for sale. Following the aforementioned modifications, I have run it, driving it with my Yaesu 101D (using my key-line buffer), and it works quite well, giving about 650-700 watts PEP (on a Telepost LP-100A). Of course... I wouldn't run it that hard in regular service, but it did work fine for the short testing done. The newer "Taylor" 572B's are in great shape.
Lastly, I'm quite well aware of the many other quirks and issues with the FL-2100's, so no need to get into a discussion about all of their other problems... LOL!
Thanks for the help.-- 73,
~Alan
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Re: Kudos to Digi Key and Hammond Mfg.
Yessir!? Hammond Mfg. and DigiKey are great resources. I've ordered a couple of their Peter Dahl transformers, and they make a first-rate product! Pricing was fair enough, and they shipped quickly. The listing of transformers is extensive, and the documentation is great. Find the one you need, copy & paste the P/N into DigiKey's main site to order, and you're done (well... after you pay). Hammond/PWDahl Transformers are HERE: -- 73,
~Alan
|
Yaesu FL-2100B Key Line Polarity
Howdy Folks,A quick question (and maybe a stupid question... but):
Can anyone see any issues in reversing the polarity on the key-line circuit (from "positive ground" to "negative ground") on the FL-2100B amp? Has anybody attempted this?Background:I'm refurbishing an FL-2100B, and have already done some upgrades and mods: New PS diodes, cap's & boards (from Harbach); Directly-grounded the grids; Performed the "Self-bias mod" (CT of filament xfmr grounded thru a 100k resistor on RX, grounded on TX thru a separate/new cube relay); Installed a new band switch (original was burned on 80m capacitor contacts), and some other general clean-up.
Currently, the key line is "positive ground" (utilizing a simple, single-diode 1/2-wave rectifier and 1000uF cap). The positive side of this DC circuit goes to the chassis ("ground"), and negative side to the keying relay. Thus, when the RCA jack is shorted to "ground" by a transceiver, it is actually switching the "positive" side.? I have read elsewhere that this "reversed" polarity could cause issues with some "modern" transceivers which require a "negative ground" key-line circuit (particularly those employing solid state/transistor switching), and therfore requiring the use of an external key-line "buffer" (which I have built and used succesfully).Anyway, since the bias-circuit no longer has anything to do with the keying relay circuit, any issues that anyone might be aware of, by reversing the polarity?? I've studied the circuit schematic (and corrected it, as per my other changes), and I can't see anything that would prevent this from working. Since doing that bias mod, the key-line power supply only supplies power the key-line relay, and has nothing to do with bias.The key circuit currently runs at 19 volts (open circuit) and 280 mA keyed.
Ultimately, this amp will be put up for sale, but I wanted to do the upgrades & mod's before I put it up for sale. Following the aforementioned modifications, I have run it, driving it with my Yaesu 101D (using my key-line buffer), and it works quite well, giving about 650-700 watts PEP (on a Telepost LP-100A). Of course... I wouldn't run it that hard in regular service, but it did work fine for the short testing done. The newer "Taylor" 572B's are in great shape.
Lastly, I'm quite well aware of the many other quirks and issues with the FL-2100's, so no need to get into a discussion about all of their other problems... LOL!
Thanks for the help.-- 73,
~Alan
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12 KW CCS ON 160-15M....USING THE 3CX-6000A7..... Part 12
Here, some updates. This is the beginnings of the elaborate chain drive assy. 2 x more chains, yet to be installed, plus tensioner's....( for the vac tune + load caps).
Note on the big model 90 switch, there is a tall, rhombus shaped black end plate....at both ends of the switch assy....(oriented vertically).
In the normal configuration, the black end plate, at the FRONT of the switch is mounted on the INSIDE of the panel (along with the spring detent / nylon assy). In normal configuration, only the 1/4" steel shaft sticks out the front of the panel....through a panel bearing.
In this amplifier, the switch was taken apart, and the FRONT end plate was mounted on the OUTSIDE of the front (inner) panel....( along with the spring detent assy).
Done like this so the switch wafer assy doesn't stick as far back on the inside of the RF deck. There is severe space constraints on the inside of the RF deck.
Ferrite loaded plate choke finally fabricated...(and tweaked)....and tested on the VNA. It will be shipped out to Scott later this week. I had to make new, narrower copper straps ( 1/2" vs 3/4") so I could get an extra 8 turns onto the assy. The winding is now 5.5" long (vs 5.0") . Final choke config is now 405 uh. This dropped the 1st series resonance freq down to where I want it. (1st series resonance now at 17. 125 mhz...midway between top of 20m..and bottom of 15m..so choke won't work on 17m). The amp only works on 160-80-40-20-15m. NO 17/12/10m on this amp. It only has a 5 position bandswitch...with 4 x sequential rotors.... to make it into a shorting style bandswitch. And no, we can't re-use the 15M tap on 17m. Reason is, with the L coil inserted between the plate block cap assy, and the C1 vac tune cap, it's designed to lower the loaded tank on 15M. In software, if 15m tap re-used on 17m, the loaded tank Q skyrockets to an unacceptable value. Without the extra '"L" coil installed, the Q is too high on 15M..... BUT if re-used on 17M, would only increase the tank Q by another 17%. So L coil installed, low Q on 15m, and no 17m operation. Since no 17m operation, having the plate choke resonate near 17m band is a non issue. The model 90 switch is a 10 position, 36 deg switch. The max you can do with that switch is a 5 pole sequential rotor...which results in a 6 position bandswitch. Scott is re-using an old model 90 switch, and it only came with a 4 pole sequential rotor...so only 5 x bands.
Original loaded plate choke with it's 5" winding, was 305 uh, and resonated at 19.750 mhz....(and also 33 mhz). Interestingly enough, as an experiment, I removed 3/4" of turns so 12.5 turns removed...and winding was now only 4.25" long. Inductance dropped to 249 uh....and 1st series resonance shifted up to 23.3 mhz.... ( and 2nd series resonance shifted up to 39.990 mhz). Ok, winding completely removed....and new, narrower straps installed. This time, winding length increased to 5.5". Choke is now 405 uh. 1st series resonance is now 17.125 mhz.... ( and 2nd series resonance is now 29 mhz).
I believe this latest, and last config will work good. It will also minimize the residual RF current through the choke on 160m.
Stay tuned for more.
https://www.youtube.com/watch?v=exY4_UBmhsI
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Re: Kudos to Digi Key and Hammond Mfg.
What does it say on the SN on the dahl / Hammond xfmrs ??? ? Dahl / Hammond told me that it is NOT a SN, but the actual date code.?
I bought 2 of the dahl FWB rectifier assy's....just when dahl announced he was retiring....and had misc items on sale cheap.? ?Both of em have identical SN's.?
Then I found out yrs later ( just a few yrs ago, 2019), that the...'SN'? is actually the date code.? ( year / week built)? with 1st 2 digits being the year...and? digits 3+4 being the week...01-52).
?
I learn something new everyday.?
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Re: Identifying some rare tubes... 2nd
Even located in the adjacent room I can still hear an arc if were to occur. The 3x6 I¡¯m building now will have a spark gap on the c1 and c2 , grid overload , plate overload , cathode return fuse , grid current fuse , plate b+ fuse , series glitch plate b+, fuse in series with one side of the plate secondary , blower pressure interlock. Should be pretty bullet proof.
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On 2024-02-25 15:51, Steve wrote: On 2/25/2024 1:28 PM, Amp Guy Llc wrote:
But the real question is why would you want a noisy pa in the same
room with you. Because you wear headphones, and external noise doesn't bother you??
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Alan - W5ARM