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Re: L7 makes alot of smoke
I have looked very closely at the tuning caps and cannot find any areas of arcing. It now seems that the problem is the TR relay is hanging up with some contact not releasing. I am going to remove it and look at burnishing the contacts, and if not possible, I do have a NOS replacement relay.? I don't have high power series ballast or a bunch of incandescent bulbs.? So I will keep looking.? Thanks
73? Bob |
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Re: L7 makes alot of smoke
¿ªÔÆÌåÓýSounds to me like big vhf parasitic oscillation ¡ to start with you need to get the hv supply power reduced for testing without destruction ¡. A very handy thing to have is a high power series ballast ¡. What is needed are something like floor heater cones or large incandescent bulbs with switching arrangement ,,, do you feel this?
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Re: L7 makes alot of smoke
I don't recall the symptoms you are having, but have you checked the plate tuning cap for any signs of arcing? Bill N0CU On Fri, May 3, 2024 at 11:31?AM K6OXN Bob via <bobk6oxn=[email protected]> wrote: Well, I am at my wits end. I replaced the 47 ohm carbon resistors with 47 ohm 5 watt metal oxide film resistors and now the same thing is happening. Got the indication that there was an arc and then lost the amp. Have it on the bench and the resistors show high heat and cracked ceramic coating.? I have spares so can replace, but now I am wondering where and how to find if there is a parasitic oscillation.? I don't know where to look or how. I cannot see anything when tuning up and cannot see any other indications.? I can use some help or suggestions. |
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Re: OT: Coax bypass switches
Another option:
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You'd need two of them, but they're only $15 each. Fast enough for QSK. They can pass 200W, but only hot-switch 75W. - Jerry, KF6VB On 2024-05-03 10:04, Chuck N0CW wrote:
You might have a look on EBay for RCL Electronics S-3170 RF transfer |
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Re: OT: Coax bypass switches
Those switches have F connectors on them and are intended for Satellite TV or similar use. They might be good for a few watts but nothing more. They might be very handy for switching circuitry inside transceivers, receivers or other low level RF circuits.
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73, Clint, VE3CMQ -----Original Message-----
From: [email protected] <[email protected]> On Behalf Of n4buq via groups.io Sent: Friday, 3 May 2024 12:43 To: DRAKE-RADIO <[email protected]> Subject: Re: [DRAKE-RADIO] OT: Coax bypass switches Here's the listing to which I was referring: Caveat: These may not take much power and, with the "Static Sensitive" label, that might also rule them out. Perhaps these are better for switch signals in a lab, etc. Barry - N4BUQ |
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Re: OT: Coax bypass switches
Apparently they're 75-ohm switches. Move along, nothing to see here... Apologies. Barry - N4BUQ Here's the listing to which I was referring: |
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Re: OT: Coax bypass switches
Here's the listing to which I was referring:
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Caveat: These may not take much power and, with the "Static Sensitive" label, that might also rule them out. Perhaps these are better for switch signals in a lab, etc. Barry - N4BUQ These are going for ridiculously cheap on eBay. "N" connectors? The SPDT might |
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Re: L7 makes alot of smoke
Well, I am at my wits end. I replaced the 47 ohm carbon resistors with 47 ohm 5 watt metal oxide film resistors and now the same thing is happening. Got the indication that there was an arc and then lost the amp. Have it on the bench and the resistors show high heat and cracked ceramic coating.? I have spares so can replace, but now I am wondering where and how to find if there is a parasitic oscillation.? I don't know where to look or how. I cannot see anything when tuning up and cannot see any other indications.? I can use some help or suggestions.
73? Bob |
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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 |
Jim Shorney
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