Re: DL-300 - DC Resistance?
I find that tuning up on 40M at night, on top of one of the few remaining SW stations, with an antenna tuner to get the SWR down to 1:1, ?makes a great substitute "dummy load" for certain tests. ?
I suspect the DL300 is more robust than a typical MFJ load. :)? If you look at the deratng curve it is specified for 30 seconds maximum at 300W and 75W continuous.
On Sat, 05 Apr 2025 17:33:35 -0700
"Richard Knoppow via groups.io" <1oldlens1@...> wrote:
> I am not familiar with this particular dummy loD but found others I have which are nominally 50 ohms go up to about 57 ohms when overloaded. I think the resistor us decided into sections which are in parallel and one will open up when overloaded causing the total resistance to go up. I have had this happen to at least three of them.? Not normal. They should measure 50 ohms.? These are speced at 50 to 150 watts but can handle very little power.Usually DC resistance will be the same as rf .? It takes only a second for them to burn out
--
73
-Jim
NU0C
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Re: PTO makes scraping sound
Correct. You will see a little more than 10V on the wire due to the voltage drop across the 100 Ohm resistor inside the PTO. The 11V that you saw in the other radio seems reasonable. On Sat, 05 Apr 2025 17:56:18 -0700 "Mark N2DMI via groups.io" <markkiziuk1@...> wrote: [Edited Message Follows]
Jim if I follow correctly then the PTO MUST be connected to the circuit in order to see the +10 volts on the +10 volt line of the PTO.
The zener in the circuit will make sure that the PTO is getting the +10 volts.
OK let me connect the PTO with a couple of alligator clips to the +10 volt and ground on that small board that feeds the PTO.
I'm guessing that I can leave RF output and RIT wires off?
I will then measure to see what voltage is fed to the +10 volt line of the PTO and see if I can pick up anything with my spectrum analyzer on the RF out line.
Mark -- 73 -Jim NU0C
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Re: DL-300 - DC Resistance?
I suspect the DL300 is more robust than a typical MFJ load. :) If you look at the deratng curve it is specified for 30 seconds maximum at 300W and 75W continuous. On Sat, 05 Apr 2025 17:33:35 -0700 "Richard Knoppow via groups.io" <1oldlens1@...> wrote: I am not familiar with this particular dummy loD but found others I have which are nominally 50 ohms go up to about 57 ohms when overloaded. I think the resistor us decided into sections which are in parallel and one will open up when overloaded causing the total resistance to go up. I have had this happen to at least three of them.? Not normal. They should measure 50 ohms.? These are speced at 50 to 150 watts but can handle very little power.Usually DC resistance will be the same as rf .? It takes only a second for them to burn out -- 73 -Jim NU0C
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Re: PTO makes scraping sound
Jim if I follow correctly then the PTO MUST be connected to the circuit in order to see the +10 volts on the +10 volt line of the PTO.
The zener in the circuit will make sure that the PTO is getting the +10 volts.
OK let me connect the PTO with a couple of alligator clips to the +10 volt and ground on that small board that feeds the PTO.
I'm guessing that I can leave RF output and RIT wires off?
I will then measure to see what voltage is fed to the +10 volt line of the PTO and see if I can pick up anything with my spectrum analyzer on the RF out line.
Mark
?
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Re: DL-300 - DC Resistance?
I recommend the Heathkit Cantenna. Commonly found at hamfests.
They're a little messy, and I put mine in a sealed bucket with a coax
pigtail coming out the top. Also, I disposed of the original oil,
cleaned it out and put in new mineral oil.
Not using it much now, because I acquired a 500 30dB Bird attenuator
that works great as a load.
- Jerry, KF6VB
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On 2025-04-05 17:33, Richard Knoppow via groups.io wrote: I am not familiar with this particular dummy loD but found others I
have which are nominally 50 ohms go up to about 57 ohms when
overloaded. I think the resistor us decided into sections which are in
parallel and one will open up when overloaded causing the total
resistance to go up. I have had this happen to at least three of them.
Not normal. They should measure 50 ohms. These are speced at 50 to
150 watts but can handle very little power.
Usually DC resistance will be the same as rf . It takes only a second
for them to burn out.
-------- Original message --------
From: n4buq <n4buq@...>
Date: 4/5/25 5:15 PM (GMT-08:00)
To: DRAKE-RADIO <[email protected]>
Subject: [DRAKE-RADIO] DL-300 - DC Resistance?
I have a DL-300 I've been using for testing my TR-4 and MN-2000. I
decided to measure it's DC resistance and found it is 56 ohms. I
expected either 50 or 52 ohms so was a bit surprised. I tried
checking it directly on the ends of the resistive element and that
also measured 56 ohms.
I presume this isn't exactly normal and perhaps someone ran it with
too much power for too long but I don't know that. From what I can
tell about it's construction, I presume these resistors wouldn't
normally drift like some other resistors but I don't know that for
sure.
56 ohms isn't exactly terrible but I am wondering if that's true.
Anyone know about these?
Thanks,
Barry - N4BUQ
Links:
------
[1] /g/DRAKE-RADIO/message/84166
[2] /mt/112109535/243852
[3] /g/DRAKE-RADIO/post
[4] /g/DRAKE-RADIO/editsub/243852
[5] /g/DRAKE-RADIO/leave/12260778/243852/767576506/xyzzy
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Re: DL-300 - DC Resistance?
I've never had a dummy load that was exactly 50 Ohms. It will also change with temperature. An interesting test would be to measure it after it has been heated up. It is also sometimes difficult to accurately measure low value resistors. You're a shade over 10%. OK for testing but I wouldn't use it for any sort of calibration. On Sat, 5 Apr 2025 20:14:59 -0400 (EDT) "n4buq via groups.io" <n4buq@...> wrote: I have a DL-300 I've been using for testing my TR-4 and MN-2000. I decided to measure it's DC resistance and found it is 56 ohms. I expected either 50 or 52 ohms so was a bit surprised. I tried checking it directly on the ends of the resistive element and that also measured 56 ohms.
I presume this isn't exactly normal and perhaps someone ran it with too much power for too long but I don't know that. From what I can tell about it's construction, I presume these resistors wouldn't normally drift like some other resistors but I don't know that for sure.
56 ohms isn't exactly terrible but I am wondering if that's true. Anyone know about these?
Thanks,
Barry - N4BUQ -- 73 -Jim NU0C
|
Re: DL-300 - DC Resistance?
I am not familiar with this particular dummy loD but found others I have which are nominally 50 ohms go up to about 57 ohms when overloaded. I think the resistor us decided into sections which are in parallel and one will open up when overloaded causing the total resistance to go up. I have had this happen to at least three of them.? Not normal. They should measure 50 ohms.? These are speced at 50 to 150 watts but can handle very little power. Usually DC resistance will be the same as rf .? It takes only a second for them to burn out.
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Show quoted text
-------- Original message -------- From: n4buq <n4buq@...> Date: 4/5/25 5:15 PM (GMT-08:00) Subject: [DRAKE-RADIO] DL-300 - DC Resistance?
I have a DL-300 I've been using for testing my TR-4 and MN-2000.? I decided to measure it's DC resistance and found it is 56 ohms.? I expected either 50 or 52 ohms so was a bit surprised.? I tried checking it directly on the ends of the resistive element and that also measured 56 ohms. I presume this isn't exactly normal and perhaps someone ran it with too much power for too long but I don't know that.? From what I can tell about it's construction, I presume these resistors wouldn't normally drift like some other resistors but I don't know that for sure. 56 ohms isn't exactly terrible but I am wondering if that's true.? Anyone know about these? Thanks, Barry - N4BUQ
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Re: PTO makes scraping sound
The +150 is connected to the collector of Q4 via the 12K resistor. Q4 is the switch that turns the PTO off when transmit control comes from the receiver, by shorting the +150 to ground through the resistor. The RIT line will have no effect as it is capacitively isolated from the DC circuits. If you connect power and ground to the PTO you should see 11-ish volts thanks to the influence of the Zener. If the Zener were shorted you should only see a couple of volts. If the Zener is open or has a bad solder joint somewhere you would see a voltage between 11 and 150 volts depending on the total resistance of the PTO circuit without the Zener influence. On Sat, 05 Apr 2025 17:06:38 -0700 "Mark N2DMI via groups.io" <markkiziuk1@...> wrote: Let me see if I follow. +150 (regulated) goes through R140 to base of Q4. +10 or +11 volts from base of Q4? I guess?
The PTO is out of the rig entirely. I measured +44.5 volts where the +10 volts wire would be connected to the circuit referenced to chassis ground.
Should I connect the PTO's RIT wire and ground wire to see if the +10 volts node (base of Q4) will read close to +10 volts?
Or is it when the +10 volt line FROM the PTO is connected to the base of Q4 is when will it will read close to +10 volts?
When PTO was connected to the radio and gave me no stations to be heard I connected my DD-103 digital frequency counter to the bottom jones plug
which gave me an erroneous frequency of something like 9 Mhz that just stayed there no matter where i turned the PTO dial.
I then got suspicious of the PTO.
I then hooked up the DD-103? to my other TR-4VW (without RIT) and the DD-103 worked like it should.
Mark -- 73 -Jim NU0C
|
I have a DL-300 I've been using for testing my TR-4 and MN-2000. I decided to measure it's DC resistance and found it is 56 ohms. I expected either 50 or 52 ohms so was a bit surprised. I tried checking it directly on the ends of the resistive element and that also measured 56 ohms.
I presume this isn't exactly normal and perhaps someone ran it with too much power for too long but I don't know that. From what I can tell about it's construction, I presume these resistors wouldn't normally drift like some other resistors but I don't know that for sure.
56 ohms isn't exactly terrible but I am wondering if that's true. Anyone know about these?
Thanks,
Barry - N4BUQ
|
Re: PTO makes scraping sound
Let me see if I follow. +150 (regulated) goes through R140 to base of Q4. +10 or +11 volts from base of Q4? I guess?
The PTO is out of the rig entirely. I measured +44.5 volts where the +10 volts wire would be connected to the circuit referenced to chassis ground.
Should I connect the PTO's RIT wire and ground wire to see if the +10 volts node (base of Q4) will read close to +10 volts?
Or is it when the +10 volt line FROM the PTO is connected to the base of Q4 is when will it will read close to +10 volts?
?
When PTO was connected to the radio and gave me no stations to be heard I connected my DD-103 digital frequency counter to the bottom jones plug
which gave me an erroneous frequency of something like 9 Mhz that just stayed there no matter where i turned the PTO dial.
I then got suspicious of the PTO.
I then hooked up the DD-103? to my other TR-4VW (without RIT) and the DD-103 worked like it should.
Mark
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2B added connectors, why?
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Re: Could be the end of my Tr7
Do you get 10R anywhere on the main board?
Look for bad solder joints everywhere that the 10R is connected, starting at the 10R pin on the filter board? The traces are very easy to follow on the main board once the bottom cover is off.
Gary
W0DVN
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On Apr 4, 2025, at 9:41?PM, Gary Follett via groups.io <xntrick1948@...> wrote:
?Have you tried anything as simple as using an ohmmeter to test continuity between the +10R source and the +10R at the filter board? I mean to the actual +10R point on the board¡
Gary
W0DVN
On Apr 4, 2025, at 9:28?PM, Jim Shorney via groups.io <jimNU0C@...> wrote:
?
A word on the nomenclature. Sources marked as +10V are +10 always. +10R is receive only, +10T is transmit only. As Stan commented the R and T voltages are switched on the Transmit Exciter board. The text descriptions of every board are very good. It will be to your benefit to study them. The +10T/R switching transistors can be considered to be three-legged fuses. They will pop from even a momentary short to ground while the bus is ON. So be very careful when making live measurements.
Don't bin it. The TR7 is very repairable. And worthy of it.
On Fri, 04 Apr 2025 18:31:26 -0700
"Mike Davidsohn G3ZCC via groups.io" <mike@...> wrote:
Hi everyone,sad news.
I traced the issue,finally, no 10R getting to the filter board, not even on the socket.
Checked the 10R on the psu board, exactly 10.0v
Removed The front panel and the two banks of switches. No 10R but 13.6 v. On A and B
The switching seems,to work though.
At a complete,loss now.
Last gasp the circuit is hard to read where do the switches derive the 10 R from? Just in case I am missing something.
It's the dustbin if I can't find the problem
Thanks
Mike G3ZCC
--
73
-Jim
NU0C
|
Re: PTO makes scraping sound
Don't panic. :) I have limited experience with the 4-line transceivers but looking at the schematic in a TR4-CW manual I see that the VFO is fed off the +150V regulated through a 12K resistor. Inside the PTO there is a 100 Ohm resistor feeding a Zener and the VFO circuitry. It seems the earlier schematic posted in this thread is likely a 7-Line PTO which does not have the Zener. With the PTO connected you will read somewhat higher than 10V, and with it out of the circuit you will see a much higher reading. The actual reading will depend on the impedance of your voltmeter in series with the 12K resistor. In the RIT version the terminal marked "FSK" in this schematic would connect instead to an internal varactor diode as shown in the 7-Line PTO schematic and to the RIT board externally. Did you check to see if you have RF output from the PTO with it in the radio? On Sat, 05 Apr 2025 14:58:34 -0700 "Mark N2DMI via groups.io" <markkiziuk1@...> wrote: I just measured the other TR-4CW (without RIT) at the sane points BUT the PTO is stll connected and I measure +11 volts. I can live with 1 volt higher but not +44 volts.
I can see if I broke something but I can't seem how I did? How can you take a PTO out, repair and clean it put it back in the circuit and the circuit breaks, pull the PTO back out and the PTO works perfectly with an external +10 volts applied to it. How does the internal +10 - +11 volts circuit break? How is that even possible?
Mark -- 73 -Jim NU0C
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Re: PTO makes scraping sound
I just measured the other TR-4CW (without RIT) at the sane points BUT the PTO is stll connected and I measure +11 volts. I can live with 1 volt higher but not +44 volts.
I can see if I broke something but I can't seem how I did? How can you take a PTO out, repair and clean it put it back in the circuit and the circuit breaks, pull the PTO back out and the PTO works perfectly with an external +10 volts applied to it. How does the internal +10 - +11 volts circuit break? How is that even possible?
Mark
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Good afternoon, fellow Drakesters!
I have a surplus T-4XB available. It has been aligned and works great. Cosmetically, the front panel and cabinet are good. Output ranges from around 100W on the lower bands to around 75W at 28.8 MHz. Chassis has darkening but not nasty.?
The frequency disc is clear, knobs are nice and it has a mid-late s/n 18xxx. Just a good, working transmitter.?
Asking $150 + shipping from 27253
I can get some photos for those interested but it will be tomorrow.?
Steve Wedge, W1ES
Time flies like an arrow. Fruit flies like a banana.
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Re: PTO makes scraping sound
I'm fighting a loosing battle! I just measured the voltage coming off of the small board that feeds the PTO its voltage.
I measure +44.5 volts!
This rig did work but it had a scraping sound due to a misaligned gear. So I removed the PTO, took pictures, re-aligned the metal bracket holding the gea so that it would correctly align, I then connected the 4 wires to the rig from the PTO. When I turn on the rig the rig cannot pick up any stations.
I then removed the PTO AGAIN and connected an external +10 volt supply to the PTO and looked at the PTO with a spectrum analyzer. The PTO has a very healthy output that is tunable across the PTO output frequency.
Today I connect a multimeter to where the +10 volts feeds the PTO red wire and ground and get +44.5 volts! Not making ANY sense to me?????
Mark
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Re: Tuning a pi-Network Output
Yep. That¡¯s what I was trying to say.?
The reason it¡¯s done on 10 is because that¡¯s the most likely band that would give you trouble.?
Steve Wedge, W1ES
Time flies like an arrow. Fruit flies like a banana.
On Sat, Apr 5, 2025 at 09:05, Mike W5RKL via groups.io < mikew5rkl@...> wrote:
Barry and Steve,
?
Neutralizing an RF amplifier is occurs ONLY on the frequency
it is performed on. This typically is done on 10 meters on an amateur
radio transmitter/transceiver final amplifier.
?
Once the neutralizing adjustment is performed on 10 meters, do NOT
make any changes to the neutralizing circuit on any lower band. You
will not see the same maximum RF output at maximum PLATE current
dip on any lower band. This is NORMAL and should NOT mean you have
to make changes to the neutralizing circuit on the lower bands.
?
Follow the manufacturer's transmitter loading/tuning instructions
in the operator's manual.
?
The Drake MN-2000 watt meter is an "average watt meter". Do not
expect to see "SSB PEP" RF levels on the MN-2000 watt meter.
?
73
Mike W5RKL
?
?
?
|
Re: Tuning a pi-Network Output
Mike,
I've read where there are some circuits that can have individual circuitry for each band that allows for "tweaking" the neutralization on each of the lower bands.? Of course, the Drake circuits don't have that but I presume it is possible.
I'm currently only using the watt meter in my MN-2000 for CW as I don't have a mic wired up for the TR-4 yet.
Thanks, Barry - N4BUQ
Barry and Steve,
?
Neutralizing an RF amplifier is occurs ONLY on the frequency
it is performed on. This typically is done on 10 meters on an amateur
radio transmitter/transceiver final amplifier.
?
Once the neutralizing adjustment is performed on 10 meters, do NOT
make any changes to the neutralizing circuit on any lower band. You
will not see the same maximum RF output at maximum PLATE current
dip on any lower band. This is NORMAL and should NOT mean you have
to make changes to the neutralizing circuit on the lower bands.
?
Follow the manufacturer's transmitter loading/tuning instructions
in the operator's manual.
?
The Drake MN-2000 watt meter is an "average watt meter". Do not
expect to see "SSB PEP" RF levels on the MN-2000 watt meter.
?
73
Mike W5RKL
?
?
?
|
Re: Tuning a pi-Network Output
Barry and Steve,
?
Neutralizing an RF amplifier is occurs ONLY on the frequency
it is performed on. This typically is done on 10 meters on an amateur
radio transmitter/transceiver final amplifier.
?
Once the neutralizing adjustment is performed on 10 meters, do NOT
make any changes to the neutralizing circuit on any lower band. You
will not see the same maximum RF output at maximum PLATE current
dip on any lower band. This is NORMAL and should NOT mean you have
to make changes to the neutralizing circuit on the lower bands.
?
Follow the manufacturer's transmitter loading/tuning instructions
in the operator's manual.
?
The Drake MN-2000 watt meter is an "average watt meter". Do not
expect to see "SSB PEP" RF levels on the MN-2000 watt meter.
?
73
Mike W5RKL
?
?
?
|
Re: Could be the end of my Tr7
Have you tried anything as simple as using an ohmmeter to test continuity between the +10R source and the +10R at the filter board? I mean to the actual +10R point on the board¡
Gary
W0DVN
toggle quoted message
Show quoted text
On Apr 4, 2025, at 9:28?PM, Jim Shorney via groups.io <jimNU0C@...> wrote:
?
A word on the nomenclature. Sources marked as +10V are +10 always. +10R is receive only, +10T is transmit only. As Stan commented the R and T voltages are switched on the Transmit Exciter board. The text descriptions of every board are very good. It will be to your benefit to study them. The +10T/R switching transistors can be considered to be three-legged fuses. They will pop from even a momentary short to ground while the bus is ON. So be very careful when making live measurements.
Don't bin it. The TR7 is very repairable. And worthy of it.
On Fri, 04 Apr 2025 18:31:26 -0700
"Mike Davidsohn G3ZCC via groups.io" <mike@...> wrote:
Hi everyone,sad news.
I traced the issue,finally, no 10R getting to the filter board, not even on the socket.
Checked the 10R on the psu board, exactly 10.0v
Removed The front panel and the two banks of switches. No 10R but 13.6 v. On A and B
The switching seems,to work though.
At a complete,loss now.
Last gasp the circuit is hard to read where do the switches derive the 10 R from? Just in case I am missing something.
It's the dustbin if I can't find the problem
Thanks
Mike G3ZCC
--
73
-Jim
NU0C
|
Jim Shorney
Mark N2DMI
