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Re: OT: Coax bypass switches
These are going for ridiculously cheap on eBay. "N" connectors? The SPDT might not work for what you're wanting to do but maybe.
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JFW 75S-111 Barry - N4BUQ ----- Original Message -----
From: "Chuck N0CW" <cwaltman@...> You might have a look on EBay for RCL Electronics S-3170 RF transfer relay for |
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Re: OT: Coax bypass switches
You might have a look on EBay for RCL Electronics S-3170 RF transfer relay for $39.95 (used). New these switches go for $150 to $400. Vendor has quantity available. Looks like BNC connectors and will operate on 24 VDC.
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Chuck N0CW On May 3, 2024, at 09:53, Lyndon VE7TFX <lyndon@...> wrote: |
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Re: L4B plate choke info
No, I did not. I will get around to that when I get the amp on the bench. I was more interested in the performance of the circuit in place so I was measuring referenced to the chassis. I will note that there is an extra 15 uH in series at the bottom after a pair of bypass caps.
On Fri, 03 May 2024 03:29:59 -0700 "Jim VE7RF via groups.io" <jim.thom@...> wrote: Did u measure the total uh with a digital lcr meter ??? ? That is what I would like to know.-- 73 -Jim NU0C |
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Re: TR4cw/rit low output, higher bands?
For issues like these, the tube tester isn¡¯t very useful, as they test either at DC or at line frequency. ?Especially for low-gain at higher frequencies, substitution is the only way to go. Steve Wedge, W1ES/4 Time flies like an arrow. Fruit flies like a banana. Sent from for iOS On Fri, May 3, 2024 at 11:15 AM, Peter A <christinepeterarsenault@...> wrote:
On Fri, May 3, 2024 at 07:45 AM, Steve Wedge, W1ES/4 wrote: |
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Re: TR4cw/rit low output, higher bands?
On Fri, May 3, 2024 at 07:45 AM, Steve Wedge, W1ES/4 wrote:
Ok Steve I think it's worth passing this on to him.? Thanks for the added info.? I did check all tubes before bring it to him, but anything is possible and sometimes it does turn out to be that "small chance", item that was the fault. I'll let you know how things play out. 73 Peter VE9KX |
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Re: TR4cw/rit low output, higher bands?
There is also a small chance that the driver tube is going bad. Strangely, I¡¯ve never seen a bad one with Drake equipment but Kenwood owners seem to have them fail more. All tubes eventually ¡°wear out¡±.? There are two other issues and those are the transmit alignments for 10 and 15 that are covered in the manual. For 10, these are set by the transformers around the driver. For 15, there are two small inductors on the band switch. Use only plastic tools on those and never force them.? 73, Steve Wedge, W1ES/4 Time flies like an arrow. Fruit flies like a banana. Sent from for iOS On Thu, May 2, 2024 at 22:03, Peter A <christinepeterarsenault@...> wrote:
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Re: L4B plate choke info
Did u measure the total uh with a digital lcr meter ??? ? That is what I would like to know.? ? As long as the plate choke doesn't series resonate near a ham band, it will.....'work'.? ?Without enough uh on the lowest band, the RF current through the choke increases a bunch.? Usually not an issue if wire ga is big enough, and correct type and value of bypass cap used at the cold end of the choke. ( .01uf disc caps are cheap, in 6/10/20/30 kv rated...and make for an excellent bypass caps for 160-30m.? 500/1000 pf doorknobs make for a better bypass cap for 10-6m).? I use 2 x .01uf @ 30 kv rated disc caps and 1-2 x 500/1000 pf @ 15 kv rated? HT-57 doorknob caps for the cold end of the? HB? plate choke on the hb amps.? EG: with a 180 uh plate choke, the C1 tune cap will have to be increased by 40 pf? on 160m? (and 10 pf on 75m)...and proportionally more if the choke is < 180 uh. Per W8JI, Rich measures, Owen duffy, software, etc, the rf current flowing through the choke is RMS RF voltage / XL of the choke at the operating freq? (assuming the choke is not series resonant).? ?The RMS RF voltage is just .6 X loaded? B+.? ( JI used .6? and? ?Measures used .66 and duffy uses .62? and I use .63 it's a moot point, but measures .66 will give the worst case current. )? ? Per JI, the typ single? 1000 pf doorknob for a bypass cap at cold end of plate choke does not make for a good bypass cap at lower freqs.? What happens is.... 1/2 of the calculated RF current through the choke? flows through the bypass cap to chassis.? The other 1/2? flows into the B+? supply...which is exactly what you don't want.? ?That effect is easily fixed with the correct bypass caps used.?? ? On a side note, what is the actual breakdown V of teflon ??? ?ARRL books state? 2 kv per mil (.001")? while the consensus using google is 1.5 kv per mil.? My hi-pot tester only goes to 15 kv, so I'm limited.? I have access to? higher V rated hi-pot testers.? I was going to run some U shaped teflon wire? along a blank sheet of Aluminum, like say 6-8" straight up above the chassis, then perhaps 6" along the chassis, then another 6-8" straight up from the chassis at the other end of the U shaped teflon wire.? ?Then hi-pot test between top end of one side of the 'U'....to the chassis.? The idea of having both ends sticking 6-8" up, was to eliminate ...'surface creep'.? At 2 kv per mil, and with the 22 ga teflon wire being .060" OD...and? inside wire diam being .028",? the? teflon wall thickness is .016" thick...... the breakdown should be 32 kv.? ?At 1.5 kv per mil, breakdown should be 24 kv.? And double either of those, between adjacent turns on a plate choke, with turns butted up tight.? ? With enamel coated magnet wire,? ?V breakdown is not very much at all, esp with smaller gauges.? I have some polyimide, 8 ga magnet wire, that's rated for 15 kv, but that 15 kv rating is for larger gauges only....and I believe 8-12 ga only.? Smaller gauges are < 10 kv....and that's for polyimide.? With enamel, formvar, nyclad etc, it's far less. ? Jim? ?VE7RF |
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Re: TR4cw/rit low output, higher bands?
"Peter, it is fairly common for these tubes, as they approach end-of-life, to have lower power output on 15 and 10.? Even with fresh tubes, you can expect around 150-175W out on those bands and that is normal.? If the neutralisation is off, you can also get lower power on the higher bands.
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At any rate, on 10m you can work the world, when the bands is open, on very low power, so it's up to you if that is acceptable.
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Also, for reference, I have a strong set of 6JB6's (3) in my TR-6 and that gets around 125W out on 6m.? Drake really was pushing those tubes to use them on 6!"
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Ok Steve that's good info to pass on.? My tech mentioned that on the low bands he's getting full output with the RF gain at about 10 o'clock.??
At 21 to 28 MHz he has to turn the gain much higher to get the 100 to 125 watts out. He said he's still trying to correct the issue.?? He also noticed that receive on the higher bands is weaker than the lower bands. and that he's been tweaking the neutralization. It's kinda funny you mention working the world on 10 meters with lower power as he brought that up also.? He talked about the difference between running 180 watts and 100 watts equals about half an S unit. I'm leaving with him as I have no doubt about his skills. Thanks for your expertise Steve. 73 Peter VE9KX |
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Re: TR4cw/rit low output, higher bands?
Peter, it is fairly common for these tubes, as they approach end-of-life, to have lower power output on 15 and 10.? Even with fresh tubes, you can expect around 150-175W out on those bands and that is normal.? If the neutralisation is off, you can also get lower power on the higher bands. At any rate, on 10m you can work the world, when the bands is open, on very low power, so it's up to you if that is acceptable. Also, for reference, I have a strong set of 6JB6's (3) in my TR-6 and that gets around 125W out on 6m.? Drake really was pushing those tubes to use them on 6! 73, Steve Wedge, W1ES/4 Time flies like an arrow.? Fruit flies like a banana.
Sent with secure email.
On Thursday, May 2nd, 2024 at 2:03 PM, Peter A <christinepeterarsenault@...> wrote:
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TR4cw/rit low output, higher bands?
My tech messaged me yesterday about my TR4cw/rit.? I brought it to him for a "going over" and alignment if it was in need.? I've owned it for 2 or 3 years but never used it.? I had it on the air just before dropping it off at his QTH which is about 110 miles from me.? I tested the output on a couple of the lower bands and had about 165 to 185 watts out which was fine but I'll admit I didn't test the higher bands as I was in a hurry before bring it to him.
My tech's emailed me to ask, if I was aware that the output on 21MHz and 28MHz are 125 watts and 100 watts respectively.? He thought that was low.? He too was getting around 185 watts on the lower bands. So my question is this.? Is it possible that my finals, which are 3 green label Sylvania's, could be a bit soft, but still give good output on the lower bands but much less on higher ones? My tech is very experienced in tube/solid state equipment and spent his life in the field of repair and as an electronics instructor for communications equipment.? He didn't specify what direction he was going to take to look into it further.? At this point would bringing him some spare 6JB6's to test output be a good idea or should he look at other area's first. What are the most common reason's for the issue my TR4 is experiencing, if there is in fact an issue at all other than aging out finals?? Again, I'm not going to second guess my tech, but since he's not a member here and there's so much experience within the group, I thought I'd ask for a bit of advice not knowing if he's fully familiar with "Drake" equipment in particular. I'll admit that it was an extremely difficult decision to leave this rig with anyone for a going over because of it's nice condition but I felt it was time. I forgot to mention that he swapped out the 6EA8 for a known good one with no improvement. Thanks, Peter VE9KX |
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Re: L4B plate choke info
I seem to have found the holy grail of plate chokes in the Alpha 76 that recently came into my possession. The original choke was re-wound years ago by a Hy-Gain (Telex) lab technician and fellow ham. I was pleasantly surprised when I tested it in situ with a NanoVNA and found no resonances below 32 MHz. I even thought about it for a few days and re-ran the test to make sure I wasn't crazy. I spoke with the tech about it and he was a bit fuzzy on the details from so far back. All he could say for sure was that he made it look like one he found on the internet.
Image attached. I plan to photo document it a little better before I put the amp in service. Yeah, I know, the jury is still out on me not being crazy.... On Thu, 02 May 2024 09:53:55 -0700 "Jim VE7RF via groups.io" <jim.thom@...> wrote: I had one of my L4B's apart yesterday. -- 73 -Jim NU0C |
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Re: Drake L4-B no Grid Current.
Did you check the grid metering calibration? IMO that is a must-do for any amp with an unknown history. In my limited sample of three they have all been off.
73 -Jim NU0C On Thu, 02 May 2024 09:42:12 -0700 "Jake KE8VGU via groups.io" <jkprz3@...> wrote: Hello! |
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L4B plate choke info
I had one of my L4B's apart yesterday.? Hooked up to the VNA, it series resonates at 16.464 mhz.......and also 23.373 mhz.? ?On paper, the choke should work on 160-10m, including warc bands.? ? The ceramic it's wound on is 5.0" tall......(x 1" diameter)....then the machine screw above that.? ?The Ameritron 3 x section choke is 5.5" tall ...x 1" diameter....then the machine screw above that. The lid can be down, with the Ameritron choke in there, but it's too close to the top lid.? There is not much of a gap. A small square sheet of Teflon on the underside of the top lid might work. ? I just finished winding? several? hb? ferrite loaded chokes recently.? ?They ranged from 762 uh down as low as 304 uh.? ?These consist of shimmed, type 61 ferrite beads slid down the inside of some hollow teflon tubing. (1" OD x? .710"? ID? x .145" wall thickness.? To hold the hb choke to the chassis, I used a 1" ID electrolytic capacitor bracket.? 1/2" or 3/4" copper strap is wrapped around the teflon tubing, ( top and? bottom) and pinched off with a single brass machine screw, and brass hardware.? The winding at each end terminates on the copper strap.? I used 22 ga, Belden silver plated and stranded wire to wind the chokes.? This stuff is .060" OD....and the? Teflon is thickwall....at .016" wall thickness.? ?I also have 22 ga teflon silver plated, stranded wire that is only .044" OD...and has a smaller, .008" teflon wall thickness on the insulation.? ? If required I could easily fabricate a plate choke for the L4B that would suffice, and not series? resonate anywhere from 1.8-30 mhz...and fit in the oem cabinet...with plenty of clearance.?? ? So far, so good.? I tested them in the VNA....and they have to be away from metal....and also dielectrics... otherwise, both series resonant freqs will drop a bit, like 500 khz.....fine, as long as you factor that effect in.? ? Also tested em with 3.22 amps CCS of DC flowing through em for 2 hrs. The inductance dropped by 2-3 uh.? Series resonance freqs shifted upwards by a tiny bit.? The hottest point on the winding was 117F.? The hottest the beads got inside was 90F.? ? On the hb amplifiers, there is a 1/4" hole drilled below the choke, so air from the plenum flows up through the entire choke.? If required, the hole could be reamed out to? 3/8"....(since the beads have a .374 ID).? ? Type 61 was used, since U1 and U2 cross at exactly 45 mhz.? The Q of the material drops to almost zero where they cross.? (type 43 crosses at exactly 7.0 mhz).? ?Resistivity of type 61 is a full magnitude higher vs type 43,33,31,77,75 etc.? ?Type 61 is 100 megohm per CM.? Currie temp is a lot higher too.? Still, type 43 has been used successfully on other amplifiers.? ? The latest pair of chokes I cooked up, are 397 uh....and also 416 uh. They are hand tweaked to series resonate exactly where I want them....( 17.675 mhz...and also 16.209 mhz.? ?Both are made for a specific application. (160-80-40-20-15m............ and 160-80-40-20-17-15m.? |
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Drake L4-B no Grid Current.
Hello! I have been restoring a Drake L4-b for the past year or so. However, my amp is not making power, and there's no grid current. Since it's been a while and I didn't take notes, I'll do my best to remember everything I've done. I have no experience with tubes and RF amplifiers, although I have read most of the post and articles on updating this amp. I've also restored a few stereos without blowing anything up, so I'd like to think I can handle a project like this. But I will most likely research any suggestion you give to ensure I implement it correctly. The L4-b when purchased lookedmostly stock, except for a power supply diode that looks like it was replaced at some point. The Eimac tubes appear original and clean, with little to no darkening on the glass. Here's what I've done so far: 1. Recapped the power supply using the PM-400 Replacement Power Supply Module. After recapping, I brought it up on a variac and a lightbulb. Then, I gradually brought the amp online with a dummy load. As some recommended, I let the tubes sit ideal for hours before putting power on them. I can't remember the exact output on the first RF power, but I remember that it was lower than I thought it should be, at the max output...100 watts in, maybe 700~750W out. Since I had what I believe is a working baseline, I went on to do the other mods. 2. ?ES4L4-B? I installed the ES4L4-B Soft-Start/Soft-Key/Bias Module. The installation went as it should. However, I had a problem with the module not coming out of the 2.5-second warm-up mode. After contacting Paul, he sent me some replacements and additional parts for his board. The soft start worked as it should. However, I battled with the variable bias. It scaled higher than it should on all solder pad positions.? I think I do have notes of what the bias is reading in each position. If that is needed to help solve my problem, I will see if I can dig it up. I believe I set the bias to whatever one gets me closest to the spec. I Can't recall what that is right now, but I can look at what it's set at when I get home later.?? 3. Grounding the grids. I removed the stock inductor and grounded the ground of the grids with copper straps.? 4. Removed the big bias resistors in the power supply.? 5. I added diodes to the meters. I think I have them installed correctly. After I take care of the big issue, I might take a picture and get some input. But they work or were working depending on the lack of grid current reading. My gut says they are fine. Most of the mods went well and the tubes, didn't blow up on the start-up procedure...I think?? The big start-up after mods with RF power. Remember, this is my first linear Amplifier, so I watched many videos and read the Drake manual many times for tune-up procedures.? I can't recall everything, so Cliff notes, But I brought up slowly 5,10,15, 35, 50, 75, and 90 watts. I can't remember if I made it to 100 watts.? Now, this is only my third or fourth time tuning it up, so I have to look at all the meters and understand how they all interact. It started making out put power as I raised the input.? Then I heard what I would say was a soft pop. It's been a while, but I remember it coming from the left side of the amp, possibly from the bottom side. From then on, the amp keys up with low output and no grid current.? I spent a lot of time looking for burnt or damaged components. I don't remember everything, but I have visually looked at probably every component in the amp and tested many with no culprit. So, I will take any suggestions and start over. I tested the HV to ensure it was getting power, and it was fine. Thinking back was at one point during the tune, I noticed I had a high grid current and adjusted for that. It wasn't maxed out, but it was above the recommended. Also, after reading some articles, I learned that you don't need 100 watts to make full power after grounding the grids. So it's been months since I have worked on it. ?Before spending $600 on tubes, I wanted this group's option. Thank you Jake |
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Re: L7 makes alot of smoke
Not so sure of this. I think aluminum can be soldered using aluminum solder and a flux like borax. A problem with aluminum is that pure aluminum develops a layer of oxide almost immediately. The layer is only about a molecule thick but prevents further oxidation and gives trouble with soldering. The oxide is also a very poor conductor.
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I used to repair RCA ribbon microphones. The ribbons are made of 100% pure aluminum foil (made originally for capacitors). It is soldered onto the pole piece clamps after stretching using aluminum solder and a very hot (1000F) iron. I was taught how to do this by a VP of engineering at RCA acoustical products. On 4/30/2024 5:27 AM, Jim VE7RF wrote:
You can't solder aluminum anyway. --
Richard Knoppow Los Angeles WB6KBL SKCC 19998 |
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DRAKE TECH NET UPDATE ( April 28, 2024 )
¿ªÔÆÌåÓýYesterdays net was held on 7.238?@ 4pm Eastern. We had a total of 27 check-ins. The following list of radio's were used: TWINS
= 4
TR3
= 1
TR4(x)
= 9
TR4
= 2
TR7
= 6
Our
net control for next week will be W9MXQ.?
73's,
Mark,
WB0IQK
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Jim Shorney
