Re: T-4XC Meter Shunt Resistor?
Totally agree with Dan on R59, the 3.3 ohm shunt resistor.
That resistor...and R49, the 2w 1.5K ohm resistor on the 250V line just above it, are often found heat damaged in the T-4XC, and I usually change them whenever a T-4XC comes my way....just because.? Your R49 looks slightly bulged around the middle to me in?your pic.? ?Check it at the very least.
73 Peter VE7PS
Yes.
Dan WB4GRA ? I'm looking to replace the 3.3ohm meter shunt resistor in the cathode circuit of my T-4XC.?
?
Is the circled resistor the right one??
--
Craig/W8CS
Greenville, SC
<shunt.jpg>
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There's a reason why Mother's Day happens a week before Hamvention ? 
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Re: Drake 2-C AVC Voltage Problem
On 2025-04-07 17:53, Jim Shorney via groups.io wrote: He wasn't a seasoned tech if he didn't know about the calibrated finger test. *** The *ouch - sizzle* test. - Jerry, KF6VB On Mon, 07 Apr 2025 16:01:38 -0700
"jerry-KF6VB via groups.io" <jerry@...> wrote:
.... I was working as a tech in a telephone equipment factory. We were
building a 24-bit telephone switch. Large boards stuffed with
rectangular
arrays of TTL ics.
One "tech" had a unique and simple way of "troubleshooting". --
73
-Jim
NU0C
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Re: Another TR7 Journey begins
On 2025-04-07 17:52, Jim Shorney via groups.io wrote: Sort of like people
drilling a hole in their iPhone because they were told that Apple
"forgot" the hole for the headphone jack. *** Were these the same people who complained when the motorized cupholders on their PCs broke? - Jerry, KF6VB
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Re: Drake 2-C AVC Voltage Problem
On 2025-04-07 16:33, Lynn KB6OKS via groups.io wrote: That was when chips and girls were affordable....maybe he was on to something!
Lynn WR7G *** I don't remember girls ever being affordable.... - Jerry, KF6VB
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Re: Drake 2-C AVC Voltage Problem
He wasn't a seasoned tech if he didn't know about the calibrated finger test. On Mon, 07 Apr 2025 16:01:38 -0700 "jerry-KF6VB via groups.io" <jerry@...> wrote: .... I was working as a tech in a telephone equipment factory. We were
building a 24-bit telephone switch. Large boards stuffed with
rectangular
arrays of TTL ics.
One "tech" had a unique and simple way of "troubleshooting". -- 73 -Jim NU0C
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Re: Another TR7 Journey begins
Reminds me of the sad Pioneer stereo receiver I picked up some years ago. Someone had aerially wired a relay and a 28 pin digital logic chip into the audio PA. WTH? The only thing I could think of was someone was pranking the owner with bogus mods. Sort of like people drilling a hole in their iPhone because they were told that Apple "forgot" the hole for the headphone jack. On Mon, 07 Apr 2025 12:20:04 -0700 "Bill NZ0T via groups.io" <nz0tham@...> wrote: And then there's this mess.? A 10 uF electrolytic cap from antenna positive to ground and the white wire to the R2001 wiper.? Huh?? None of that should be there. -- 73 -Jim NU0C
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Re: Drake 2-C AVC Voltage Problem
On 2025-04-07 17:00, Gary WB6OGD via groups.io wrote: And cost the company ten times that in uneeded
replacement parts! *** Not to mention the possibility of damaging the actual board with wholesale chip replacements- although the rework ladies were VERY good at desoldering & soldering. - Jerry, KF6VB 73,
Gary
WB6OGD
On Apr 7, 2025, at 4:20?PM, jerry-KF6VB via groups.io <jerry@...> wrote:
?On 2025-04-07 16:08, Gary WB6OGD via groups.io wrote:
If he was really high paid guy, I guess that method would make
economic sense... $5.50 an hour. This was around 1978.
- Jerry, KF6VB
But it sounds like he probably was the opposite, hi hi...
73,
Gary
WB6OGD
Links:
------
[1] /g/DRAKE-RADIO/message/84224
[2] /mt/112117533/243852
[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: TR-4CW S meter stays to the right
Check the filter cap for the bias supply. It should have the + terminal connected to ground. Some eBay sellers are offshore vendors ripping off the IP of legitimate sellers and don't have any technical knowledge. On Mon, 07 Apr 2025 17:22:48 -0700 "Mark N2DMI via groups.io" <markkiziuk1@...> wrote: Hi Tim! It has fairly brand new parts inside of the power supply. It cost me good money from someone on Ebay who rebuilds these power supplies with new boards with new parts. Hopefully its not anything to do with the power supply but who knows?
Mark -- 73 -Jim NU0C
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Re: T-4XC Meter Shunt Resistor?
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Show quoted text
On Apr 7, 2025, at 8:04?PM, Craig W8CS via groups.io <craig_severson@...> wrote:
? I'm looking to replace the 3.3ohm meter shunt resistor in the cathode circuit of my T-4XC.?
?
Is the circled resistor the right one??
--
Craig/W8CS
Greenville, SC
<shunt.jpg>
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Re: TR-4CW S meter stays to the right
Hi Tim! It has fairly brand new parts inside of the power supply. It cost me good money from someone on Ebay who rebuilds these power supplies with new boards with new parts. Hopefully its not anything to do with the power supply but who knows?
Mark
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Re: TR-4CW S meter stays to the right
Happened to me years ago and its been long time since I looked at the bottom of a AC4 but as I recall there are two rectangle higher wattage white resistors, one of those was the problem.
73 Tim
WB8UHZ
On Monday, April 7, 2025 at 08:11:02 PM EDT, Mark N2DMI via groups.io <markkiziuk1@...> wrote:
Not to my knowledge? I am very new to Drakes. There are settings for VOX and anti-VOX which to be honest might not be set right?
I'm still trying to tune this thing up. As a matter of fact, I tuned up on 40 and 20 then went to 80. When I was at 80 is when the problem kicked in.
I believe I was tuning it up correctly? Then the S meter started to go to the right and stay there with no sound.
Then as I adjust the RF gain metal finger lever it will not do anything to the S meter. Then about 2 minutes later the rig shut down. I looked inside the drake and the 2 fuses measure OK so I believe the 5 amp fuse in the power supply blew. I'm not having much luck.
Mark
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Re: TR-4CW S meter stays to the right
Not to my knowledge? I am very new to Drakes. There are settings for VOX and anti-VOX which to be honest might not be set right?
I'm still trying to tune this thing up. As a matter of fact, I tuned up on 40 and 20 then went to 80. When I was at 80 is when the problem kicked in.
I believe I was tuning it up correctly? Then the S meter started to go to the right and stay there with no sound.
Then as I adjust the RF gain metal finger lever it will not do anything to the S meter. Then about 2 minutes later the rig shut down. I looked inside the drake and the 2 fuses measure OK so I believe the 5 amp fuse in the power supply blew. I'm not having much luck.
Mark
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T-4XC Meter Shunt Resistor?
I'm looking to replace the 3.3ohm meter shunt resistor in the cathode circuit of my T-4XC.?
?
Is the circled resistor the right one??
--
Craig/W8CS
Greenville, SC
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Re: Tuning a pi-Network Output
Regardless of how I go about it, with C77 in place, C76 minimizes the output at fully open and with C77 disconnected, C76 minimizes the output at fully closed.
With one leg of C77 disconnected, I started checking its value and I kept getting very weird values: either several microfarads (yes with a "micro") or somewhere around 140 picofarads.? I decided to de-solder the other end and checked it again and it went complete to "Unknown or damaged part" on my T7 component checker.? Apparently it was on the verge of completely bad and de-soldering finished it off (short lead on one end).
I don't have a proper replacement yet but I do have a 27pF 500V SM that I might throw in there just to see if changes things much the same way the original cap did.? I presume it will still be too much extra capacitance but it might be interesting to see, with it in circuit and even though it's about double the original capacitance, whether C76 gets the output closer to a full null when it's at or nearly fully open.
I presume a disk ceramic is still the appropriate cap to use for C76?
Thanks, Barry - N4bUQ
Steve, I'll run through it that way.? As I said, all I did was monitor the output at the antenna jack with no dummy load.? Since the controls didn't seem to affect what I was seeing on the scope.? Perhaps it was mostly due to there not being a proper load resistance.? I'll report back - hopefully tomorrow. Thanks so much! Barry - N4BUQ Just to check, the transmitter should be tuned for a dip at the highest frequency or where specified by the procedure. You then leave the plate and load controls as they are, then disconnect the screen supply. Then, after disconnecting the screen supply, go into transmit with the minimum drive to see a reading on the scope. The transmitter remains connected to the dummy load. Adjust the neut cap for minimum amplitude. Reconnect the screen supply and verify that max power out coincides with plate current dip.?
Steve Wedge, W1ES
Time flies like an arrow. Fruit flies like a banana.
On Sun, Apr 6, 2025 at 17:01, n4buq <n4buq@...> wrote:
Yesterday, I disconnected the screen grid supply to the PA tubes and monitored the output at the antenna jack with my scope.? While I can see a reduction in what appears to be the spurious oscillation, that occurs at the point where C76 is fully open (which might explain why it was in that position when I saw it earlier).? I find this odd and likely a problem.? Unlike needing to change C77 just a bit for some of the tube brands, it appears there's already way too much there.
I disconnected C77 and that didn't have much, if any, affect on the value I'm seeing across C76.? That reading is somewhere around 40 nF which I think may be very much out of line as to what it should be.? Changing the band switch, varying the tune control, and varying the plate circuit caps had little, if any, affect on that capacitance value.? Disconnecting the plate connections also didn't change it much, if any.
Does that reading make any sense?? I'm thinking it doesn't and something else is very wrong but I'm at a loss to explain it.? Is what I'm seeing completely abnormal?
Thanks,
Barry - N4BUQ
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
?
?
?
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Re: TR-4CW S meter stays to the right
Almost sounds like it was keyed? Was it in tx??
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Show quoted text
On Apr 7, 2025, at 6:45?PM, Mark N2DMI via groups.io <markkiziuk1@...> wrote:
? On the TR-4CW the S meter swung to the right and stays there also there is just a very faint sound of audio. Then about two minutes later the fuse in the power supply blew!
Mark
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TR-4CW S meter stays to the right
On the TR-4CW the S meter swung to the right and stays there also there is just a very faint sound of audio. Then about two minutes later the fuse in the power supply blew!
Mark
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Re: Drake 2-C AVC Voltage Problem
That was when chips and girls were affordable....maybe he was on to something!
Lynn WR7G
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Re: Drake 2-C AVC Voltage Problem
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Jim Shorney
Mark N2DMI
Craig W8CS
Gary WB6OGD
Ronnie Hull - W5SUM