Re: L7 makes alot of smoke
Reducing the HV can be done with a variac, lightbulb, heater elements, ?etc. but the filament primary needs to be isolated from the HV transformer primary.
On Friday, May 3, 2024 at 02:45:34 PM EDT, John W4BFS <blivetbell@...> wrote:
Sounds 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?
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
Dow-Key transfer relay that can be placed anywhere and controlled from the operating position.
On Friday, May 3, 2024 at 12:53:23 PM EDT, Lyndon VE7TFX <lyndon@...> wrote:
I'm putting together a 6m tuner so I can get the TR-6
back on the air.? I want to be able to bypass the tuner,
but I have no idea what would make a suitable switch.
Anyone have a recommendation?
--lyndon
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Re: OT: Coax bypass switches
You want what's known as a transfer switch.? B&W made them and I see them for sale on eBay from time to time.? Here's the only one I found on a search just now, but it will do exactly what you need and it's $20.
73,
Dean K5DH
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Re: L7 makes alot of smoke
Bob,
Just so I understand fully,
When you "key" the amp (no driving power) the plate current "goes to max"??
On my L-4B the plate current max is? 1A !? If it is indeed MAX (1A) the power supply transformer will likely be "groaning and the circuit breakers would likely open!!
Does this happen with the coaxial cable from the IC-7610 not connected? and? "keying" it ?
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On Fri, May 3, 2024 at 02:22 PM, K6OXN Bob wrote:
Just got it back together after a full inspection.? Burnished the TR relay contacts, dirty but not arced. Now notice on low power CW mode, the Plate Current goes to max when I keyup and then takes awhile to reset back to 0 after releasing the key. This is with my 7610 and it releases when I unkey.? Studying the schematics to see where this hangup might be. Its as if something is setting and then not releasing when I unkey.? Also when the plate current is at max the audio on the SDR is garbled. Without the amp and keying with about 20 Watts of drive from the 7610 it seems ok.? Will keep looking at suspect items.
73? Bob
? --
73/Rick
W4XA
*Every post is created using Linux
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Update: The TR7 includes a 500Hz. filter, a 1.8kHz. filter and a 6kHz. filter.
Thanks,
Robin Midgett K4IDC
On Tue, Apr 23, 2024 at 1:43?PM Robin K4IDC via <RobinK4IDC= [email protected]> wrote: One owner TR7 station?available in Nashville, TN. $1500 for all of it, will ship with insurance at buyer's expense, not interested in trades, serious offers seriously considered. All the items work properly; only possible exception would possibly be the phone patch as it hasn't been utilized in quite a number of years. Please contact me directly with?any questions; I'm good on QRZ.
TR7 transceiver?(model 1337), just back from service by Ron Baker WB4HFN; details attached MS7 speaker
RV7 remote VFO PS7 power supply P75 phone patch
Also included are the original boxes for the TR7 & the PS7, a small parts cabinet with extender cards & other Drake bits & pieces.? Photos here:?
Thanks,
Robin Midgett K4IDC
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Re: L7 makes alot of smoke
Just throwing spaghetti against the wall here... Maybe your 7610 does not like the input circuit of the amp and is breaking into oscillation? Maybe you still have a relay issue. Hot switching can cause bad things to happen. Check for damaged plate choke or bypass capacitors. Excessive plate current can be a symptom of way too much drive and/or severe mis-tuning. What is happening with the grid current when this happens? Always start tune up with low drive and overcoupled Load. You might also check the input tuning adjustments per the manual procedure. You haven't said if you checked the grid current calibration. Do it. 73 -Jim NU0C On Fri, 03 May 2024 14:22:51 -0700 "K6OXN Bob via groups.io" <bobk6oxn@...> wrote: Just got it back together after a full inspection.? Burnished the TR relay contacts, dirty but not arced. Now notice on low power CW mode, the Plate Current goes to max when I keyup and then takes awhile to reset back to 0 after releasing the key. This is with my 7610 and it releases when I unkey.? Studying the schematics to see where this hangup might be. Its as if something is setting and then not releasing when I unkey.? Also when the plate current is at max the audio on the SDR is garbled. Without the amp and keying with about 20 Watts of drive from the 7610 it seems ok.? Will keep looking at suspect items.
73? Bob
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Re: OT: Coax bypass switches
Those units have F connectors...typically used in 75 ohm CATV circuits. Probably?not suitable for 50 ohm radio circuits.?
Thanks,
Robin Midgett K4IDC
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
> These are going for ridiculously cheap on eBay.? "N" connectors?? The SPDT might
> not work for what you're wanting to do but maybe.
>
> JFW 75S-111
>
> Barry - N4BUQ
>
> ----- Original Message -----
>> From: "Chuck N0CW" <cwaltman@...>
>> To: "DRAKE-RADIO" <[email protected]>
>> Sent: Friday, May 3, 2024 12:04:42 PM
>> Subject: Re: [DRAKE-RADIO] 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.
>>
>> Chuck N0CW
>>> On May 3, 2024, at 09:53, Lyndon VE7TFX <lyndon@...> wrote:
>>>
>>> ?I'm putting together a 6m tuner so I can get the TR-6
>>> back on the air.? I want to be able to bypass the tuner,
>>> but I have no idea what would make a suitable switch.
>>>
>>> Anyone have a recommendation?
>>>
>>> --lyndon
>>>
>>>
>>>
>>>
>>>
>>
>>
>>
>>
>
>
>
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Well, Alpha must have put that extra choke in there for a reason. :) This amp was built in 1977 and was still working. It was idle for many years before it saw light duty in the W0BJQ club shack until our European masters shut the plant down. On Fri, 03 May 2024 12:33:48 -0700 "Jim VE7RF via groups.io" <jim.thom@...> wrote: Yes, pse measure the uh when u have a chance.? ?BTW, that extra 15 uh is effectively out of the circuit.? Once you add the bypass caps at the base of the main plate choke, it's then game over.? Put the vna between chassis and top of the oem choke...and u will see that asap.? ?Or measure the rf current between cold side of the bypass cap at the base of the big choke...and chassis -- 73 -Jim NU0C
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Re: L7 makes alot of smoke
Bob,
I know you probably
don't want to hear this, but have you considered 'exorcism'?
Keep plugging away at
it and I'm sure you'll figure it out.
73 de Steve, NR4M
On 5/3/2024 5:22 PM, K6OXN Bob wrote:
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Just got it back together after a full inspection.? Burnished the
TR relay contacts, dirty but not arced. Now notice on low power CW
mode, the Plate Current goes to max when I keyup and then takes
awhile to reset back to 0 after releasing the key. This is with my
7610 and it releases when I unkey.? Studying the schematics to see
where this hangup might be. Its as if something is setting and
then not releasing when I unkey.? Also when the plate current is
at max the audio on the SDR is garbled. Without the amp and keying
with about 20 Watts of drive from the 7610 it seems ok.? Will keep
looking at suspect items.
73? Bob
|
Re: L7 makes alot of smoke
Just got it back together after a full inspection.? Burnished the TR relay contacts, dirty but not arced. Now notice on low power CW mode, the Plate Current goes to max when I keyup and then takes awhile to reset back to 0 after releasing the key. This is with my 7610 and it releases when I unkey.? Studying the schematics to see where this hangup might be. Its as if something is setting and then not releasing when I unkey.? Also when the plate current is at max the audio on the SDR is garbled. Without the amp and keying with about 20 Watts of drive from the 7610 it seems ok.? Will keep looking at suspect items.
73? Bob
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Re: OT: Coax bypass switches
Down the page the specs say? +20 dbm.? Isn't that 100 milliwatts ?? Very low power .
Ralph ku4pt
On Friday, May 3, 2024 at 01:56:10 PM EDT, Clint VE3CMQ <ve6cmm@...> wrote:
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.
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: L7 makes alot of smoke
I have tried 2 different sets of tubes. Both were matched sets and seem to work perfect in my friends L4B..
Bob
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Re: L7 makes alot of smoke
This has been going on for a while, so please excuse me if I ask if you have tried different tubes.
Steve Wedge, W1ES/4
Time flies like an arrow.? Fruit flies like a banana.
Sent with secure email.
On Friday, May 3rd, 2024 at 2:59 PM, K6OXN Bob <bobk6oxn@...> wrote:
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: OT: Coax bypass switches
I use multiple Alpha Delta 4-port and 2-port switches. Good isolation and have handled legal limit for over 17 years. Good up to 2 meters, but I only run 100 watts on 2 meters. Rob, NC0B
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On May 3, 2024, at 12:19 PM, Lyndon VE7TFX <lyndon@...> wrote:
?Sorry folks, I should have been more specific.
I'm looking for a mechanical switch, not a relay. And it
needs to handle at least a couple of hundred watts.
--lyndon
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Yes, pse measure the uh when u have a chance.? ?BTW, that extra 15 uh is effectively out of the circuit.? Once you add the bypass caps at the base of the main plate choke, it's then game over.? Put the vna between chassis and top of the oem choke...and u will see that asap.? ?Or measure the rf current between cold side of the bypass cap at the base of the big choke...and chassis.
?
On some amps, like the ASI / CE? types, they used 2 x choke in series, big and small (135 uh + 45 uh).? ?A block cap at the junction to one side of a SPST-NO relay....then to chassis.? Both chokes used on 160m only.? ?(Relay open).? ?With relay closed, cold end of junction cap? is grnded to chassis...and the big choke is then outa the circuit.? ?Small choke used on 80-10m.? ?They also wired a 3 x meg resistor? between cold end of junction cap....and chassis.? That's to DC grnd the? cold end of the junction cap at all times.? Without it, the cold end of the junction cap will assume full B+.? A cap with one end floating won't block DC...due to leakage resistance.? ?We had huge arcs coming off buddy's? 2 x piece plate choke setup...until the 3 x 1megohm @ 2 watt CC? in series was installed.? ? We found the trick in alpha schematic.? ?The concept was...any plane jane spst-no relay could be used.??
We thought both chokes could be used on 160-30m..were we wrong.? Both chokes only work on 160m, that's it. Flame on when trying to use em on 80+40m.? We just re-invented the wheel.? CE / ASI did the same thing.? Both chokes on 160m only, small choke used on 80-10m.
A 2nd method using a vac relay, is to shunt the bigger choke out.? ( henry radio)? Henry used a 180 uh choke in series with a 20 uh choke.?
A 3rd method? is to use a SPDT vac relay....with COM to anode of the tube...and toggle between? 2 x chokes. NO to choke #1...and NC to choke #2.? Commander uses this method.
?
All 3 x methods are a compromise, and far from optimized.?
?
My ferrite loaded chokes have limitations too..... like trying to park both series resonances outside ham bands.? ?It's one or the other, but not both...at least not for the amount of uh I want.?
I have? a couple more configs I'm going to try out.? But with one config using 305 uh, it resonated at 23 mhz and also 39.9 mhz.? ? Problem is, to move the 1st series resonance point up to say 33 mhz, will require a huge drop in uh.? I will find out soon enough next week.?
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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
|
Re: L7 makes alot of smoke
Sounds 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?
toggle quoted message
Show quoted text
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
|
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
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
|
Re: OT: Coax bypass switches
Another option:
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
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On 2024-05-03 10:04, Chuck N0CW wrote: 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.
Chuck N0CW
On May 3, 2024, at 09:53, Lyndon VE7TFX <lyndon@...> wrote:
?I'm putting together a 6m tuner so I can get the TR-6
back on the air. I want to be able to bypass the tuner,
but I have no idea what would make a suitable switch.
Anyone have a recommendation?
--lyndon
|
Re: OT: Coax bypass switches
Sorry folks, I should have been more specific.
I'm looking for a mechanical switch, not a relay. And it
needs to handle at least a couple of hundred watts.
--lyndon
|
Robin K4IDC
Jim Shorney
Rob Sherwood