On Sat, Jan 11, 2025 at 07:28 PM, Art Delibert wrote:
>Jim accurately describes the manner in which IMD is typically tested and reported ¡ª i.e., when two close-in signals produce an IMD product that exceeds the noise floor.? But it seems to me that the IMD inherent in just >about any amplifier will actually raise the noise floor, because any noise within the passband is causing some low-level IMD products that also appear within the passband.??
?
>So the noise floor might be said to consist of two components, which we'll call Original Noise and IMD Noise.? When we reduce the RF gain, we're reducing the Signal and the Original Noise by the same amount, but >reducing the IMD Noise faster, because of the 1:3 ratio between the Original Noise and the IMD Noise.
?
>If we're considering just the noise floor of the receiver circuitry, this effect would be pretty small.? But if we consider band noise as a component of the Original Noise,? and consider how the IMD products of that band >noise contribute to what we're calling IMD Noise, the effect may not be so small, particularly on the low bands where most of us experience a lot of noise.? In this case, turning down the rf gain could make a noticeable >contribution to the S/N ratio.? I think this is why Bob Heil's video is able to show a marked increase in readability of an 80-meter QSO by turning down the rf gain.
?
>Thoughts welcome.
?
>Art Delibert, KB3FJO
I find it real hard to? believe that band noise alone will? create enough IMD to? degrade anything.? ?With band noise like S4 to S8....any imd would be through the floor.? ?You wouldn't even be able to measure it, if say using 2 x test tones, and each? S8.? When turning down the RF gain, the agc threshold increases.? Assume a? S7 to S8 noise level on 75m.? ?And the SSB stations you are talking to are all S9 + 10 db.? ?Reduce the RF gain till the S meter swings up to? S9.? ?The agc threshold has risen greatly,? and any signal <S9? will drop off rapidly.? ?Ok, the S7-S8 band noise just vanishes.? ?Why, because the noise is now below the agc threshold.? And none of this has anything to do with IMD.? ?Heil didn't invent anything new.? ? This technique about reducing the RF gain control a bunch, on the lower bands, when loads of band noise is present.... is old news.? Your only other option would be to run the RF gain at MAX.....then introduce enough RX padding,? such that the S7-S8 band noise is inaudible.? IE: add say aprx? 30-40 db of padding, such that the band noise is below the S2 agc threshold.? ?Your S9 + 10 db SSB signals will drop by 30-40db.
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Re: TR7 recommission stalls.
Dear Jim and Craig
40 mhz on p19
53.695 on p17
Where is p40?
I can hear 5.645 on an adjacent rx and correctly not when the Tr7 is in AM Mode.
Sorry but I can't find the sheet I had with the pin numbers on
Kind Regards
Mike
G3ZCC
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Looks like the only way to move the dial is to loosen the screw on
the arm in this pic. Looks like that will allow one to push the gear
back enough to move the dial. This is a pic of the PTO in my RV7.
Looks like it use a bit of cleaning while I have it out.
73
Stan
KM4HQE
On 1/12/25 06:33, Steve Wedge, W1ES/4
via groups.io wrote:
toggle quoted message
Show quoted text
I¡¯m trying to remember if there was anything
special about doing it because I know that I did have a TR7 with
the 100s dial annoyingly out of whack.?
IIRC, there¡¯s a spring-loaded idle gear, just like
the older ones. Push against the tension and you can move the
dials. It almost seemed like I needed a third hand but somehow I
managed (and my hands aren¡¯t small). The problem I remember is
keeping both of them aligned at the same time.?
73,
Steve Wedge, W1ES
Time flies like an arrow. Fruit flies like a banana.
On Sat, Jan 11, 2025 at 19:20, Stan Gammons via groups.io <buttercup11421@...>
wrote:
Hi All,
We got a little bit of snow yesterday, about 4 inches, so I
decided to
finally pull the DR7 board to try and figure out what's causing
the PLL
unlock problem.? I replaced the DR7 with the jumper board and
the rig
has been solid all day. So, it's looks like a DR7 problem.?
However, the
dial on the PTO is about 9 Kc high when I'm on the right
frequency and
the knob is full clockwise and no way to get the dial to match
the
actual frequency.? I looked on the WB4HFN site but I couldn't
find an
article describing how to recenter the dial on the PTO.? Any
advice on
how to get the dial recentered so it will be a bit closer than
it is now?
73
Stan
|
Re: TR7 recommission stalls.
|
There is a good graphic of the dial in the Files area:
Drake_Dial.pdf
?
73,
Gary
WB6OGD
?
|
I¡¯m trying to remember if there was anything special about doing it because I know that I did have a TR7 with the 100s dial annoyingly out of whack.?
IIRC, there¡¯s a spring-loaded idle gear, just like the older ones. Push against the tension and you can move the dials. It almost seemed like I needed a third hand but somehow I managed (and my hands aren¡¯t small). The problem I remember is keeping both of them aligned at the same time.?
73,
Steve Wedge, W1ES
Time flies like an arrow. Fruit flies like a banana.
On Sat, Jan 11, 2025 at 19:20, Stan Gammons via groups.io < buttercup11421@...> wrote: Hi All,
We got a little bit of snow yesterday, about 4 inches, so I decided to
finally pull the DR7 board to try and figure out what's causing the PLL
unlock problem.? I replaced the DR7 with the jumper board and the rig
has been solid all day. So, it's looks like a DR7 problem.? However, the
dial on the PTO is about 9 Kc high when I'm on the right frequency and
the knob is full clockwise and no way to get the dial to match the
actual frequency.? I looked on the WB4HFN site but I couldn't find an
article describing how to recenter the dial on the PTO.? Any advice on
how to get the dial recentered so it will be a bit closer than it is now?
73
Stan
|
Hi need the transformer to this board. Any ideas where to buy?
|
I have checked the relay. There was a little bit of carbon on one side of the relay contacts but hardly no pitting. Also while checking the tubes with a multimeter I found that there was no connection on one of the grid pins. It appeared that it had lost its connection inside the adapter (the round phenolic piece with the large hollow metal pins). I could slide the multimeter probe between the glass and phenolic and contact the small portion of the pin where it exits the glass. Here I had continuity between it and the other two grid pins but not when connecting to the lower soldered portion. It was that way on both tubes same pin. I desoldered all the pins and pulled the adapter off. In that pin there was very little solder. I'm now in the process of resolderind both tubes. I've got one done.
|
In order to proceed in getting new plastic dials made, that will not discolor, I need to borrow a dial from someone to use as a prototype; it doesn¡¯t have to be glass-clear as normal. ?It can be discolored, but all the printing needs to be present and undistorted. ?A little discussion about the mysterious darkening of some dials offers a good hypothesis about what is going on here. ?The normally clear plastic called Lexan (TM), a polycarbonate with production beginning in 1960, did (and still can) discolor; as most know, these radios are over 55 years old. ?¡°After 1970, the brownish polycarbonate tint was improved to glass clear.¡± ?On the other hand, acrylic often called Plexiglass (TM) will not discolor over time. ?As a reference, safety lenses and most all eyewear lenses are made of polycarbonate plastic because of its durability. ?So, this offers a plausible explanation why some dials are clear with no problems and others are this brownish color. ?Apparently the manufacturer of the dial used Lexan when the supply of acrylic ran short, temporarily, or perhaps began using Lexan altogether during the 60¡¯s in lieu of acrylic.
?
If someone can allow me to borrow a spare B-line dial, please let me know. ?I will do everything possible to keep it in the present condition.
?
Thank you.
?
73, Michael Smith, N4KZO
?
?
|
Hi All,
We got a little bit of snow yesterday, about 4 inches, so I decided to
finally pull the DR7 board to try and figure out what's causing the PLL
unlock problem.? I replaced the DR7 with the jumper board and the rig
has been solid all day. So, it's looks like a DR7 problem.? However, the
dial on the PTO is about 9 Kc high when I'm on the right frequency and
the knob is full clockwise and no way to get the dial to match the
actual frequency.? I looked on the WB4HFN site but I couldn't find an
article describing how to recenter the dial on the PTO.? Any advice on
how to get the dial recentered so it will be a bit closer than it is now?
73
Stan
|
Re: TR-4Cw RIT Squirrely on 20
Yeah, it's weird.? I tuned to the "other" null and that seems to have done it.? Initially, it was pegging the meter over most of the tune range.? Only on 20.? Very strange.
Steve Wedge, W1ES
Time flies like an arrow.? Fruit flies like a banana.
Sent with secure email.
On Saturday, January 11th, 2025 at 6:43 PM, John K5MO via groups.io <johnk5mo@...> wrote:
Steve
I think I'd follow your nose and plug in another set of PA tubes and see what happens. It's the easiest least-invasive step at this point.
Kinda surprised it doesn't take off on 10, but does on 20.
John
On Sat, Jan 11, 2025 at 4:21?PM Steve Wedge, W1ES/4 via <w1es= [email protected]> wrote: Interestingly, I have seen the following:
Disconnected one tube's plate cap at a time. No problems.
Put rig on 28.7 and checked the neut. I dipped with loading cap at 0, removed screen lead, nulled the output signal on scope x10 probe. I noticed that some positions of the RF TUNE control give suddenly high-amplitude signals. Also noticed that there are two nulls on the neut cap that are 4 clock directions from each other (i.e., if one is at 10, the other is at 2). I tuned to one of them.
Reconnected screen lead. 10m loads up fine. I still can get 20m to break into whatever it's breaking into but it's at a very small place on the RF TUNE dial that's nowhere near where the receive and transmit signal peak..
I put these tubes in a few months ago but haven't played with it much. They COULD be the tubes from the scrapped TR-4C -- tubes with gremlins? For now, I seem to have tamed it. Interestingly, getting a dip on 80m is very broad. The other bands are fine. Close to 200W out on 80 and 40, about 175W on 20, dropping to 150W on 15 and a little over 120W on 10.
Has anyone out there seen the neut cap have two nulls when neutralising by disconnecting the screen lead?
I still think these tubes are suspect but I may as well use them, as they're stronger than what was in there.
73,
Steve Wedge, W1ES
Time flies like an arrow. Fruit flies like a banana.
Sent with secure email.
On Saturday, January 11th, 2025 at 3:14 PM, Steve Wedge, W1ES/4 via <w1es= [email protected]> wrote:
I had taken my TR-4Cw RIT offline and to the bench to use for comparison to Ronnie's similar rig (only difference is mine has a NB and is about a month or so older than his).
I figured that I'd go through some transmitter testing (the receive seems to be okay but has a parsimonious S meter, like many do). On 10m midband, the neutralisation looks okay (I'd done it a couple of years ago)., I bring the rig onto 20m and the plate meter pins! Connections are fine and 10m shows a little over 100W out (yeah, the finals aren't new). I can only get 20 to behave with the RF TUNE control down near 1 - 2, which isn't at peak receive.
I had another, rather ugly TR-4C that had a similar problem and I could never fix it. I finally wound up scrapping it for parts (it was pretty ugly, anyway) but there's no way I am going to scrap this rarest of all TR-4 rigs.
Any ideas?
Steve Wedge, W1ES
Time flies like an arrow. Fruit flies like a banana.
Sent with secure email.
|
Re: TR-4Cw RIT Squirrely on 20
Steve, you might also try a different driver tube. I had a squirrely TR-4x that changing the driver made it behave.
Unfortunately, I do not remember which brand of 12BY7 was in the rig but not one of those recommended.
73 ES GL, Bob K9JU
On Saturday, January 11, 2025 at 06:44:09 PM EST, John K5MO via groups.io <johnk5mo@...> wrote:
Steve
I think I'd follow your nose and plug in another set of PA tubes and see what happens. It's the easiest least-invasive step at this point.
Kinda surprised it doesn't take off on 10, but does on 20.
John
On Sat, Jan 11, 2025 at 4:21?PM Steve Wedge, W1ES/4 via <w1es= [email protected]> wrote: Interestingly, I have seen the following:
Disconnected one tube's plate cap at a time.? No problems.
Put rig on 28.7 and checked the neut.? I dipped with loading cap at 0, removed screen lead, nulled the output signal on scope x10 probe.? I noticed that some positions of the RF TUNE control give suddenly high-amplitude signals.? Also noticed that there are two nulls on the neut cap that are 4 clock directions from each other (i.e., if one is at 10, the other is at 2).? I tuned to one of them.
Reconnected screen lead.? 10m loads up fine.? I still can get 20m to break into whatever it's breaking into but it's at a very small place on the RF TUNE dial that's nowhere near where the receive and transmit signal peak..
I put these tubes in a few months ago but haven't played with it much.? They COULD be the tubes from the scrapped TR-4C? -- tubes with gremlins?? For now, I seem to have tamed it.? Interestingly, getting a dip on 80m is very broad.? The other bands are fine.? Close to 200W out on 80 and 40, about 175W on 20, dropping to 150W on 15 and a little over 120W on 10.
Has anyone out there seen the neut cap have two nulls when neutralising by disconnecting the screen lead?
I still think these tubes are suspect but I may as well use them, as they're stronger than what was in there.
73,
Steve Wedge, W1ES
Time flies like an arrow.? Fruit flies like a banana.
Sent with secure email.
On Saturday, January 11th, 2025 at 3:14 PM, Steve Wedge, W1ES/4 via <w1es= [email protected]> wrote:
I had taken my TR-4Cw RIT offline and to the bench to use for comparison to Ronnie's similar rig (only difference is mine has a NB and is about a month or so older than his).
I figured that I'd go through some transmitter testing (the receive seems to be okay but has a parsimonious S meter, like many do).? On 10m midband, the neutralisation looks okay (I'd done it a couple of years ago)., I bring the rig onto 20m and the plate meter pins!? Connections are fine and 10m shows a little over 100W out (yeah, the finals aren't new).? I can only get 20 to behave with the RF TUNE control down near 1 - 2, which isn't at peak receive.
I had another, rather ugly TR-4C that had a similar problem and I could never fix it.? I finally wound up scrapping it for parts (it was pretty ugly, anyway) but there's no way I am going to scrap this rarest of all TR-4 rigs.
Any ideas?
Steve Wedge, W1ES
Time flies like an arrow.? Fruit flies like a banana.
Sent with secure email.
|
Re: TR-4Cw RIT Squirrely on 20
Steve
I think I'd follow your nose and plug in another set of PA tubes and see what happens. It's the easiest least-invasive step at this point.
Kinda surprised it doesn't take off on 10, but does on 20.
John
On Sat, Jan 11, 2025 at 4:21?PM Steve Wedge, W1ES/4 via <w1es= [email protected]> wrote: Interestingly, I have seen the following:
Disconnected one tube's plate cap at a time.? No problems.
Put rig on 28.7 and checked the neut.? I dipped with loading cap at 0, removed screen lead, nulled the output signal on scope x10 probe.? I noticed that some positions of the RF TUNE control give suddenly high-amplitude signals.? Also noticed that there are two nulls on the neut cap that are 4 clock directions from each other (i.e., if one is at 10, the other is at 2).? I tuned to one of them.
Reconnected screen lead.? 10m loads up fine.? I still can get 20m to break into whatever it's breaking into but it's at a very small place on the RF TUNE dial that's nowhere near where the receive and transmit signal peak..
I put these tubes in a few months ago but haven't played with it much.? They COULD be the tubes from the scrapped TR-4C? -- tubes with gremlins?? For now, I seem to have tamed it.? Interestingly, getting a dip on 80m is very broad.? The other bands are fine.? Close to 200W out on 80 and 40, about 175W on 20, dropping to 150W on 15 and a little over 120W on 10.
Has anyone out there seen the neut cap have two nulls when neutralising by disconnecting the screen lead?
I still think these tubes are suspect but I may as well use them, as they're stronger than what was in there.
73,
Steve Wedge, W1ES
Time flies like an arrow.? Fruit flies like a banana.
Sent with secure email.
On Saturday, January 11th, 2025 at 3:14 PM, Steve Wedge, W1ES/4 via <w1es= [email protected]> wrote:
I had taken my TR-4Cw RIT offline and to the bench to use for comparison to Ronnie's similar rig (only difference is mine has a NB and is about a month or so older than his).
I figured that I'd go through some transmitter testing (the receive seems to be okay but has a parsimonious S meter, like many do).? On 10m midband, the neutralisation looks okay (I'd done it a couple of years ago)., I bring the rig onto 20m and the plate meter pins!? Connections are fine and 10m shows a little over 100W out (yeah, the finals aren't new).? I can only get 20 to behave with the RF TUNE control down near 1 - 2, which isn't at peak receive.
I had another, rather ugly TR-4C that had a similar problem and I could never fix it.? I finally wound up scrapping it for parts (it was pretty ugly, anyway) but there's no way I am going to scrap this rarest of all TR-4 rigs.
Any ideas?
Steve Wedge, W1ES
Time flies like an arrow.? Fruit flies like a banana.
Sent with secure email.
|
Re: TR7 recommission stalls.
The manual is very clear. The explanation of how that stage works begins in the last paragraph on page 2-50. It is an autodyne mixer. It does appear that the two output side inductors are mislabeled but that is easy enough to figure out from the photo. You should not be tweaking coils to fix a hard failure. Your main suspects are Molexia, failed Q1008, bad crystal, Q1004 not switching as it should, insufficient 13.695 injection from Q1005, and solder joint(s) (not necessarily in that order). You will not be measuring 8.050 directly. As mentioned by Craig you should see the 5.645 (nominal) BFO signal on pin 40 in any mode except AM RX. If you see 5.645 on the drain of Q1008 but not on pin 40 you have a problem in the BFO steering matrix CR1006 through CR1011. On Sat, 11 Jan 2025 10:06:50 -0800 "Mike Davidsohn G3ZCC via groups.io" <mike@...> wrote: Good evening everyone.
The Tr7 has stopped working.
I have traced it to the PBT/REFERENCE board.
Have it fitted to extenders, all oscillators working fine except the 8.050, which does not appear to be working at all.
I think the manual has a typo on the number of the coils.1101
I have also tried testing this by draping both the frequency counter and a gc rx listening on the frequency..
Manual not too clear (just my luck).
Anyone have any ideas?
Thanks in advance.
Mike
G3ZCC -- 73 -Jim NU0C
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FWIW, when I was experimenting with RF stages in an old receiver I added a manual gain control to the first RF only. Simply a bypassed variable cathode resistor. I found it necessary when there were many strong signals but only for some tubes. Not necessary for a 6BA6 on AVC but when I tried some very high gain pentodes and a cascode I found it was necessary. This was a war time Super-Pro which had been worked over before I got it. Eventually I restored the original circuits except for adding a VR tube to the local oscillator. Unfortunately I do not still have it. I think part of the reason for needing the gain reduction was the linearity of the following RF but I did not have the instruments to measure it at the time.
toggle quoted message
Show quoted text
On 1/11/2025 12:58 PM, Jim Shorney via groups.io wrote: I provided you with an eloquent explanation from W8II and you did not accept it. So I leave it up to you to find your own as you will likely not accept mine either. 73 AR SK
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
Re: TR-4Cw RIT Squirrely on 20
Interestingly, I have seen the following:
Disconnected one tube's plate cap at a time.? No problems.
Put rig on 28.7 and checked the neut.? I dipped with loading cap at 0, removed screen lead, nulled the output signal on scope x10 probe.? I noticed that some positions of the RF TUNE control give suddenly high-amplitude signals.? Also noticed that there are two nulls on the neut cap that are 4 clock directions from each other (i.e., if one is at 10, the other is at 2).? I tuned to one of them.
Reconnected screen lead.? 10m loads up fine.? I still can get 20m to break into whatever it's breaking into but it's at a very small place on the RF TUNE dial that's nowhere near where the receive and transmit signal peak..
I put these tubes in a few months ago but haven't played with it much.? They COULD be the tubes from the scrapped TR-4C? -- tubes with gremlins?? For now, I seem to have tamed it.? Interestingly, getting a dip on 80m is very broad.? The other bands are fine.? Close to 200W out on 80 and 40, about 175W on 20, dropping to 150W on 15 and a little over 120W on 10.
Has anyone out there seen the neut cap have two nulls when neutralising by disconnecting the screen lead?
I still think these tubes are suspect but I may as well use them, as they're stronger than what was in there.
73,
Steve Wedge, W1ES
Time flies like an arrow.? Fruit flies like a banana.
Sent with secure email.
On Saturday, January 11th, 2025 at 3:14 PM, Steve Wedge, W1ES/4 via groups.io <w1es@...> wrote:
I had taken my TR-4Cw RIT offline and to the bench to use for comparison to Ronnie's similar rig (only difference is mine has a NB and is about a month or so older than his).
I figured that I'd go through some transmitter testing (the receive seems to be okay but has a parsimonious S meter, like many do).? On 10m midband, the neutralisation looks okay (I'd done it a couple of years ago)., I bring the rig onto 20m and the plate meter pins!? Connections are fine and 10m shows a little over 100W out (yeah, the finals aren't new).? I can only get 20 to behave with the RF TUNE control down near 1 - 2, which isn't at peak receive.
I had another, rather ugly TR-4C that had a similar problem and I could never fix it.? I finally wound up scrapping it for parts (it was pretty ugly, anyway) but there's no way I am going to scrap this rarest of all TR-4 rigs.
Any ideas?
Steve Wedge, W1ES
Time flies like an arrow.? Fruit flies like a banana.
Sent with secure email.
|
I provided you with an eloquent explanation from W8II and you did not accept it. So I leave it up to you to find your own as you will likely not accept mine either. 73 AR SK On Sat, 11 Jan 2025 16:55:25 +0000 (UTC) "Joseph K7CBR via groups.io" <k7cbr@...> wrote: I was looking forward to an explanation. -- 73 -Jim NU0C
|
On Saturday, January 11, 2025 at 03:18:31 PM EST, Thomas W9TAB via groups.io <electron@...> wrote:
Tim,?
You¡¯re welcome, glad to have been some help
On Jan 11, 2025, at 12:36?PM, amfone via groups.io <amfone20000@...> wrote:
?
? Tom
Thanks for your help, I did as you noted and adjusted R17, now it? reads 1900V LV no load and 2700V HV? no load, a little high on the HV but unless you think there is another issue I'm happy.
Now the funny thing is about 4 days ago that was the first thing I did, that is adjust R17 using the method you noted. However I first turned it a little to the right and then a little to the left and really did not see a
change on the meter so I went in another direction, but it worked this time turning the amp off and adjusting just a little bit at at time. The first time I saw movement on the meter but I turned it in the wrong direction, so with about 4 times turning the
amp on to read the meter and off to make the adjustment making certain the bleeders drained of any existing voltage I kept moving it little by little, then I had to move it back just a bit.
I'll tell you seeing that tiny adjustment is difficult, using a flashlight you have to get at the right angle or the light just reflects back into your eyes.
Thanks for your HELP Tom very much.
73 Tim
WB8UHZ
On Saturday, January 11, 2025 at 09:32:51 AM EST, amfone via groups.io <amfone20000@...> wrote:
OK Tom thanks for the advice I will do so, very much appreciated. I have the amp apart now I'll do so today.
Tim,?
If you¡¯re sure the meter itself is ok then tweak the pot to see if you can increase the reading on the L7 meter.?
Use a non conductive tool.
To be safe give it small adjustments with the amp off and make sure the plate ¡°Ep button is pushed in¡± plate voltage meter is reading ¡°0¡± (Capacitors discharged) before adjusting.?
You want to move it in the direction of ¡°More¡± resistance (Wiper in the direction of the ground side) as one side is directly grounded.?
CCW looking at the back of the amp.?
Then turn the amp on and check the reading.
Repeat as necessary.?
Tom
On Friday, January 10, 2025 at 06:15:43 PM EST, Thomas W9TAB via groups.io <electron@...> wrote:
Tim,?
If you¡¯re sure the meter itself is ok then tweak the pot to see if you can increase the reading on the L7 meter.?
Use a non conductive tool.
To be safe give it small adjustments with the amp off and make sure the plate ¡°Ep button is pushed in¡± plate voltage meter is reading ¡°0¡± (Capacitors discharged) before adjusting.?
You want to move it in the direction of ¡°More¡± resistance (Wiper in the direction of the ground side) as one side is directly grounded.?
CCW looking at the back of the amp.?
Then turn the amp on and check the reading.
Repeat as necessary.?
Tom
On Jan 10, 2025, at 4:49?PM, amfone via groups.io <amfone20000@...> wrote:
?
Tom I have two L7's and one L4B so I did not use anything to measure it against other than the meter on the other two amps, both of which read the proper voltage. I also used two different supplies as I have four all which I have rebuilt. Using
two different supplies the one L7 I'm working on read low in the LV and HV position. The other two amps with the same supplies read correctly.
73 Tim
WB8UHZ
On Friday, January 10, 2025 at 05:44:23 PM EST, Thomas W9TAB via groups.io <electron@...> wrote:
Tim,
What did you use to measure it with to compare against the meter in the amp??
Color TV HV probe, HV probe with DVM etc.?
I use a Fluke 80k-40 with a Fluke 87 DVM in my shop.?
Tom?
On Jan 10, 2025, at 11:33?AM, Evan via groups.io <k9sqg@...> wrote:
?
I typically see 1800 volts and 2500 volts BUT that is for my specific line voltage! ?Low line voltage results in low readings.
Tom
The B+ voltage is reading about 1500 to 1600 on the LV reading no load and about 2200 to 2300 on HV? no load. I took it out of line to work on it and can't give accurate numbers at this time but suffice to say it reads low.
I did not do the other adjustments.
Thanks Tim
On Thursday, January 9, 2025 at 09:35:48 PM EST, Thomas W9TAB via groups.io <electron@...> wrote:
Tim
I missed your response on an earlier post, how far off is the B+ voltage? (Measured vs indicated)?
How did the Grid / Plate current calibrations turn out??
(Verifying a 100% working meter)?
Tom W9TAB?
On Jan 9, 2025, at 5:08?PM, amfone via groups.io <amfone20000@...> wrote:
?
Tom I opened up the L7 today and the 2.2 meg resistors 8 of them rather than reading 17.6 Megs are actually reading 16.66 Meg. or just less than 5% off. Not sure if that is the problem perhaps? R17 is the issue, R17 is 10K and adjustable any
idea of where to get that little thing?
If you think I'm wrong on the dropping resistors and the effect they would have on the proper voltage reading let me know please.
Thanks 73 Tim
WB8UHZ
On Wednesday, January 8, 2025 at 11:19:24 AM EST, amfone via groups.io <amfone20000@...> wrote:
Thank you Thomas yes these are carbon style resistors that Drake used back in the day and over time they age, take in moisture etc. and change in value I'm hoping that is the issue as I purchased new resistors from Mouser.
Thank you
Tim
On Wednesday, January 8, 2025 at 09:43:20 AM EST, Thomas W9TAB via groups.io <electron@...> wrote:
Tim,
Carbon composition resistors typically increase in value over time due to absorbing moisture.?
That is the reason the voltage divider network resistance has increased causing the voltage to read low.?
Military spec publications identified this a long time ago and Allen Bradley recommended taking the resistors and putting them in an oven at 150F for 5 days to return them to spec.?
Naturally in your case it makes more sense to just replace them if you cannot adjust it with the potentiometer, after all, that¡¯s why it¡¯s there. ?
On Jan 7, 2025, at 10:47?PM, amfone via groups.io <amfone20000@...> wrote:
?
OK sorry for the mistake I used the term in reference to the meter not reading correctly.
73 Tim
WB8UHZ
On Tuesday, January 7, 2025 at 10:55:56 PM EST, Jim Shorney via groups.io <jimnu0c@...> wrote:
OK but please stop calling them shunts. They are series voltage dropping resistors. The only shunt is the pot. A shunt is a resistance across the meter terminals to increase the current value needed for a full scale reading.
On Wed, 8 Jan 2025 03:38:34 +0000 (UTC)
"amfone via groups.io" <amfone20000@...> wrote:
>? Jim thanks for your help regarding the location and the voltage requirements of the shunts.
--
73
-Jim
NU0C
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Tim,?
You¡¯re welcome, glad to have been some help
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On Jan 11, 2025, at 12:36?PM, amfone via groups.io <amfone20000@...> wrote:
?
? Tom
Thanks for your help, I did as you noted and adjusted R17, now it? reads 1900V LV no load and 2700V HV? no load, a little high on the HV but unless you think there is another issue I'm happy.
Now the funny thing is about 4 days ago that was the first thing I did, that is adjust R17 using the method you noted. However I first turned it a little to the right and then a little to the left and really did not see a
change on the meter so I went in another direction, but it worked this time turning the amp off and adjusting just a little bit at at time. The first time I saw movement on the meter but I turned it in the wrong direction, so with about 4 times turning the
amp on to read the meter and off to make the adjustment making certain the bleeders drained of any existing voltage I kept moving it little by little, then I had to move it back just a bit.
I'll tell you seeing that tiny adjustment is difficult, using a flashlight you have to get at the right angle or the light just reflects back into your eyes.
Thanks for your HELP Tom very much.
73 Tim
WB8UHZ
On Saturday, January 11, 2025 at 09:32:51 AM EST, amfone via groups.io <amfone20000@...> wrote:
OK Tom thanks for the advice I will do so, very much appreciated. I have the amp apart now I'll do so today.
Tim,?
If you¡¯re sure the meter itself is ok then tweak the pot to see if you can increase the reading on the L7 meter.?
Use a non conductive tool.
To be safe give it small adjustments with the amp off and make sure the plate ¡°Ep button is pushed in¡± plate voltage meter is reading ¡°0¡± (Capacitors discharged) before adjusting.?
You want to move it in the direction of ¡°More¡± resistance (Wiper in the direction of the ground side) as one side is directly grounded.?
CCW looking at the back of the amp.?
Then turn the amp on and check the reading.
Repeat as necessary.?
Tom
On Friday, January 10, 2025 at 06:15:43 PM EST, Thomas W9TAB via groups.io <electron@...> wrote:
Tim,?
If you¡¯re sure the meter itself is ok then tweak the pot to see if you can increase the reading on the L7 meter.?
Use a non conductive tool.
To be safe give it small adjustments with the amp off and make sure the plate ¡°Ep button is pushed in¡± plate voltage meter is reading ¡°0¡± (Capacitors discharged) before adjusting.?
You want to move it in the direction of ¡°More¡± resistance (Wiper in the direction of the ground side) as one side is directly grounded.?
CCW looking at the back of the amp.?
Then turn the amp on and check the reading.
Repeat as necessary.?
Tom
On Jan 10, 2025, at 4:49?PM, amfone via groups.io <amfone20000@...> wrote:
?
Tom I have two L7's and one L4B so I did not use anything to measure it against other than the meter on the other two amps, both of which read the proper voltage. I also used two different supplies as I have four all which I have rebuilt. Using
two different supplies the one L7 I'm working on read low in the LV and HV position. The other two amps with the same supplies read correctly.
73 Tim
WB8UHZ
On Friday, January 10, 2025 at 05:44:23 PM EST, Thomas W9TAB via groups.io <electron@...> wrote:
Tim,
What did you use to measure it with to compare against the meter in the amp??
Color TV HV probe, HV probe with DVM etc.?
I use a Fluke 80k-40 with a Fluke 87 DVM in my shop.?
Tom?
On Jan 10, 2025, at 11:33?AM, Evan via groups.io <k9sqg@...> wrote:
?
I typically see 1800 volts and 2500 volts BUT that is for my specific line voltage! ?Low line voltage results in low readings.
Tom
The B+ voltage is reading about 1500 to 1600 on the LV reading no load and about 2200 to 2300 on HV? no load. I took it out of line to work on it and can't give accurate numbers at this time but suffice to say it reads low.
I did not do the other adjustments.
Thanks Tim
On Thursday, January 9, 2025 at 09:35:48 PM EST, Thomas W9TAB via groups.io <electron@...> wrote:
Tim
I missed your response on an earlier post, how far off is the B+ voltage? (Measured vs indicated)?
How did the Grid / Plate current calibrations turn out??
(Verifying a 100% working meter)?
Tom W9TAB?
On Jan 9, 2025, at 5:08?PM, amfone via groups.io <amfone20000@...> wrote:
?
Tom I opened up the L7 today and the 2.2 meg resistors 8 of them rather than reading 17.6 Megs are actually reading 16.66 Meg. or just less than 5% off. Not sure if that is the problem perhaps? R17 is the issue, R17 is 10K and adjustable any
idea of where to get that little thing?
If you think I'm wrong on the dropping resistors and the effect they would have on the proper voltage reading let me know please.
Thanks 73 Tim
WB8UHZ
On Wednesday, January 8, 2025 at 11:19:24 AM EST, amfone via groups.io <amfone20000@...> wrote:
Thank you Thomas yes these are carbon style resistors that Drake used back in the day and over time they age, take in moisture etc. and change in value I'm hoping that is the issue as I purchased new resistors from Mouser.
Thank you
Tim
On Wednesday, January 8, 2025 at 09:43:20 AM EST, Thomas W9TAB via groups.io <electron@...> wrote:
Tim,
Carbon composition resistors typically increase in value over time due to absorbing moisture.?
That is the reason the voltage divider network resistance has increased causing the voltage to read low.?
Military spec publications identified this a long time ago and Allen Bradley recommended taking the resistors and putting them in an oven at 150F for 5 days to return them to spec.?
Naturally in your case it makes more sense to just replace them if you cannot adjust it with the potentiometer, after all, that¡¯s why it¡¯s there. ?
On Jan 7, 2025, at 10:47?PM, amfone via groups.io <amfone20000@...> wrote:
?
OK sorry for the mistake I used the term in reference to the meter not reading correctly.
73 Tim
WB8UHZ
On Tuesday, January 7, 2025 at 10:55:56 PM EST, Jim Shorney via groups.io <jimnu0c@...> wrote:
OK but please stop calling them shunts. They are series voltage dropping resistors. The only shunt is the pot. A shunt is a resistance across the meter terminals to increase the current value needed for a full scale reading.
On Wed, 8 Jan 2025 03:38:34 +0000 (UTC)
"amfone via groups.io" <amfone20000@...> wrote:
>? Jim thanks for your help regarding the location and the voltage requirements of the shunts.
--
73
-Jim
NU0C
|
TR-4Cw RIT Squirrely on 20
I had taken my TR-4Cw RIT offline and to the bench to use for comparison to Ronnie's similar rig (only difference is mine has a NB and is about a month or so older than his).
I figured that I'd go through some transmitter testing (the receive seems to be okay but has a parsimonious S meter, like many do).? On 10m midband, the neutralisation looks okay (I'd done it a couple of years ago)., I bring the rig onto 20m and the plate meter pins!? Connections are fine and 10m shows a little over 100W out (yeah, the finals aren't new).? I can only get 20 to behave with the RF TUNE control down near 1 - 2, which isn't at peak receive.
I had another, rather ugly TR-4C that had a similar problem and I could never fix it.? I finally wound up scrapping it for parts (it was pretty ugly, anyway) but there's no way I am going to scrap this rarest of all TR-4 rigs.
Any ideas?
Steve Wedge, W1ES
Time flies like an arrow.? Fruit flies like a banana.
Sent with secure email.
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Mike Davidsohn G3ZCC
Gary WB6OGD
Jim Shorney
Thomas W9TAB