Re: Using the PLJ-6LED digital display with the R4C
Just scoped the voltage at the INJ jack on the R4C across the bands.? As suspected, the voltage drops off the higher you go.? Here's what I see:
?
1.8 MHz - 1.96 VP-P
3.5 MHz - 2.08 VP-P
7.0 MHz - 5.9 VP-P
10 MHz - 3.96 VP-P
14 MHz - 1.82 VP-P
21 MH - 1.3 VP-P
28 MHz - 1.76 VP-P
?
It seems that anything below 1.9 V or so is where the problem starts.? These voltages were measured at the INJ jack without the counter connected and going straight into the scope with no probe attenuation.
?
73, Floyd - K8AC
|
Using the PLJ-6LED digital display with the R4C
I've been experimenting with the PLJ-6LED LED display with the R4C for a couple of days and have some issues.? Would like to hear what others have done to perhaps resolve these problems.? I'm feeding the signal at the INJ jack on the R4C directly into the counter and the voltage to the unit is 13.8 V.? ?On frequencies from 1.8 to 10 MHz, the display is stable and the frequency is accurate (checked against 10 MHz WWV).? On 14 MHz,? the frequency display becomes unstable, jumping around within a KHz or so of the correct frequency.? On 21, 24 and 28 MHz, the display is extremely unstable and the frequency shown is randomly up to several MHz off.? The R4C is properly aligned and I have full T4XC output on all bands when using the R4C to control the frequency.? I'm assuming that the signal level at the INJ jack for the higher frequencies is just not high enough for the unit to get an accurate sample, but haven't scoped it yet.
?
I've played with the sensitivity/bias pot on the display board but was unable to improve things.? Even on the lower bands where the signal must be adequate for the counter,? adjusting the sensitivity/bias control does not seem to provide a linear control, but rather shows a sweet spot above and below which stability is lost.? So, I wonder what others have experienced with the counter on the higher bands?? If you don't see the same issue I'm seeing, did you use a buffer stage to feed the counter as the fellow who made the Youtube videos on the subject did?? I have two of the counters and they both behave the same way.??
?
Any suggestions appreciated.
?
73, Floyd - K8AC
|
Re: AFG/RFG controls R4C (W1ES)
I'm not sure.? I bought the set at a hamfest and it had the knobs on it already.
I'm not one for making "mods" to vintage equipment but this one is really, really nice and is easily reversible.
Trying to find anything on the internet today is such a death march that I'm afraid that I'll leave it to you.? The type of knob used on 4-Line is called a "bar knob".? I'll try searching but I'm sure I will get 10 pages of "Buy it here" rubbish...
My patience with the internet is thinner than rice paper at this point.? It has been ruined.
Steve Wedge, W1ES
Time flies like an arrow.? Fruit flies like a banana.
Sent with secure email.
On Monday, January 6th, 2025 at 12:57 PM, Joseph K7CBR via groups.io <k7cbr@...> wrote:
Hello Steve,
Is the control you used still available or is it obsolete? Thanks
Joseph
On Monday, January 6, 2025 at 12:51:03 PM EST, Steve Wedge, W1ES/4 via groups.io <w1es@...> wrote:
I just took a quick look inside my late (28xxx) R-4C and it looks like there are circuits and structures that would interfere with a shield extension but I can hear the modulation a lot more when the slug/rod is out the back.
My receiver is totally stock except for having changed out the original AFG/RFG controls for a nice concentric plastic knob set that looks just like what Drake ¡°should have¡± put there.
I will likely leave things as they are, as it¡¯s more of a collector piece that I play with. ?It¡¯s similar in the auto world as a stock vs modified ¡°thing¡±. ?I am also not short on things that I need to do.
73,?
W1ES
|
Re: R4C Sherwood audio mod questions
Rob, please ignore my previous email. The attachments showed up on my laptop but not my cell phone. Bill N0CU
Steve,
I don¡¯t know, but removing most of the magnetic field is a better solution.? Paul¡¯s shield of the transformer didn¡¯t work.
Rob, NC0B?
?
I¡¯m wondering if the buzz could be tamed by extending the shield can of the PTO ¡ª slide a second metal box over the end where the slug rod comes out.?
Just spitballing¡¯¡
Steve Wedge, W1ES
Time flies like an arrow. Fruit flies like a banana.
On Sun, Jan 5, 2025 at 18:47, VE7PS via < ve7ps@...> wrote:
Floyd:
I recall looking at Rob's xformer shuffle mod a few years back and couldn't figure out why I would want to go through that, despite?having chassis punches of all sizes and having done many power supply board upgrades on many R-4C's which requires removing
most of the xformer leads.? Just didn't think it was worth it.
I'm not home much in winter and just happened to be home today and had the chance to check out Rob's (or was it Paul's?) suggestion?of listening?to the xtal calibrator at both ends of the 500 Khz dial.? WOW!? He was spot on! I had never tried this before.?
At 500 Khz on the dial, indeed the signal?is buzzy.
Now before I started unsoldering the transformer in the three R-4C's currently here, I stopped to think a bit.? How often do I use the upper portion of the 500 Khz dial?? The answer for me is not often at all.? In fact, I'm not?often above 250 Khz on the
dial, in part due to our Canadian frequency rules.? On top of that....CW is generally at the low end of the bands where I cannot audibly detect any of the AC buzz/hum I hear on the xtal calibrator signal at 500 Khz.? I have yet to check that with a scope.
There is no question it's there at the upper end.....do not even need the scope to tell me....but I rarely use that end of the bands.
YMMV!? For now that project remains a low priority.
73
Peter
VE7PS
On Sun, Jan 5, 2025 at 1:10?PM Floyd - K8AC via
<floydsense=
[email protected]> wrote:
Guess I'll look around for a chassis punch and add this to my project list.? I operate a lot of CW and really like to hear a very pure note.? I've been spoiled by the sound of CW from my RME 6900 the past few months.? RME used a balanced feed to the filaments,
no chassis ground on the filament string.? And, they applied +80 VDC to the filament circuit.? I was puzzled by that until I went to my old RCA tube manual and read about filament recommendations.? It was described there and advised that it was a way of reducing
hum.
?
73, Floyd - K8AC
|
Good point Steve, the bracket holds the lamps and have been known to short out the meters
toggle quoted message
Show quoted text
On Jan 6, 2025, at 11:56?AM, Steve Wedge, W1ES/4 via groups.io <w1es@...> wrote:
?
Also, check the terminals of each meter to ensure that none of them touch the brackets holding the lamps. ?It happened to me.
Steve Wedge, W1ES
Time flies like an arrow. Fruit flies like a banana.
On Mon, Jan 6, 2025 at 9:26 AM, Thomas W9TAB via groups.io < electron@...> wrote:
With power disconnected, take the case off and then remove the metal shield that covers the meters, look at the connections to the meters and make sure they are soldered.
I recently acquired an L7 from a Hamfest that didn¡¯t look like it had been used very much, the plate current meter wasn¡¯t working and I found the wire was just pushed through the meters solder lug and had never been soldered from the factory.?
The manual explains how to electronically check / calibrate both current meters without powering up the amp that would be a good troubleshooting start.?
On Jan 6, 2025, at 8:12?AM, Clayton kk4iz via groups.io <KK4IZ284@...> wrote:
? I have a L-7 and neither meter is working. I have not checked to see if ?the watt meeter works.
On Jan 5, 2025, at 10:25?PM, Thomas W9TAB via groups.io <electron@...> wrote:
It¡¯s
your HV meter scale adjustment R17 and is also shown on the schematic.?
Use a plastic tweaker.?
How far off is your meter??
Are the other scales correct? (Grid current, Watts)
If not your meter could be bad.?
Here is the excerpt from the manual:?
g.?
The high voltage adjustment potentiometer Rl7
is not user adjustable. If this needs readjust-
ment, return the L 7 to the factory for service
Drake knew how dangerous it was to perform this adjustment and didn¡¯t want the user to try to adjust it.?
Tom W9TAB?
On Jan 5, 2025, at 6:21?PM, Jim Shorney via groups.io <jimNU0C@...> wrote:
?
It appears that is your plate voltage calibration pot as was mentioned before. Check it against the schematic.
On Mon, 6 Jan 2025 00:16:12 +0000 (UTC)
"amfone via groups.io" <amfone20000@...> wrote:
In the back of the L7 next to the fan is a small hole with an adjustment control needing a small screwdriver to make the adjustment. I can't find anything in the manual about this, does anyone know what its for?
Thanks?
Tim
WB8UHZ
--?
73
-Jim
NU0C
73¡¯²õ
KK4IZ
Amateur Radio Operator
Warren Bryant?
124 Crestview Dr
Clanton,AL.??35045
Email:?KK4IZ284@...
Cell: 205-389-4170
|
Re: R-4 AM detector 1N625
Hello, Jan. ?It appears that this could be replaced with the very common 1N914.?
73,
Steve Wedge, W1ES
Time flies like an arrow. Fruit flies like a banana.
On Mon, Jan 6, 2025 at 11:49 AM, Jan SM5MRQ < jan@...> wrote: [Edited Message Follows]
Hi guys?
?
I am working on a R-4 receiver and am not satisfied with the AM mode , I suspect the AM- detector diods 1N625 as I had to replace the V10 / 12AX7A tube which is surrounded by 3 of these diods. What do you guys use as a substitute for the 1N625 diode?
?
73 Jan SM5MRQ
?
?
|
Re: R4C Sherwood audio mod questions
Rob, can you send me a link for your presentation? Thanks, Bill N0CU
Hi Paul,
?
I was reviewing my 2012 Hamvention Drake Forum presentation and came across a picture of the AMP-4 in my R-4C.? The inverting input has a 220 uF capacitor installed.?
There may well be some AMP-4s with 330 uF capacitors for the inverting input.
?
The bulk of the attached Drake presentation deals with drastically reducing the line-related sidebands on the R-4C PTO.? I know you and I found this solution
independently about the same time, likely in 2011.? R-4C owners may find this attached document interesting.?
?
It is tedious to rotate the R-4C power transformer 90 degrees, but it really makes a difference.? A hole punch makes the job mechanically easy even if there
is a good bit of work removing and reinstalling the wires.
?
We will likely never know why Drake mounted the transformer properly in the R-4, R-4A and R-4B, but mounted it incorrectly in the R-4C.
?
73, Rob, NC0B
?
From: [email protected] [mailto:[email protected]]
On Behalf Of Paul Christensen via
Sent: Saturday, January 04, 2025 6:52 AM
To: [email protected]
Subject: Re: [DRAKE-RADIO] R4C Sherwood audio mod questions
?
On Sat, Jan 4, 2025 at 05:19 AM, Floyd - K8AC wrote:
>The text specifies the inverting input capacitor as 200 uF while the schematic shows it as 330 uF.
The computed -3 dB high-pass turnover frequency is 123 Hz for 330 uF, and 204 Hz for 200 uF.? Pick either one based on personal roll-off preference.
|
AFG/RFG controls R4C (W1ES)
Hello Steve,
Is the control you used still available or is it obsolete? Thanks
Joseph
On Monday, January 6, 2025 at 12:51:03 PM EST, Steve Wedge, W1ES/4 via groups.io <w1es@...> wrote:
I just took a quick look inside my late (28xxx) R-4C and it looks like there are circuits and structures that would interfere with a shield extension but I can hear the modulation a lot more when the slug/rod is out the back.
My receiver is totally stock except for having changed out the original AFG/RFG controls for a nice concentric plastic knob set that looks just like what Drake ¡°should have¡± put there.
I will likely leave things as they are, as it¡¯s more of a collector piece that I play with. ?It¡¯s similar in the auto world as a stock vs modified ¡°thing¡±. ?I am also not short on things that I need to do.
73,?
W1ES
|
Also, check the terminals of each meter to ensure that none of them touch the brackets holding the lamps. ?It happened to me.
Steve Wedge, W1ES
Time flies like an arrow. Fruit flies like a banana.
On Mon, Jan 6, 2025 at 9:26 AM, Thomas W9TAB via groups.io < electron@...> wrote:
With power disconnected, take the case off and then remove the metal shield that covers the meters, look at the connections to the meters and make sure they are soldered.
I recently acquired an L7 from a Hamfest that didn¡¯t look like it had been used very much, the plate current meter wasn¡¯t working and I found the wire was just pushed through the meters solder lug and had never been soldered from the factory.?
The manual explains how to electronically check / calibrate both current meters without powering up the amp that would be a good troubleshooting start.?
On Jan 6, 2025, at 8:12?AM, Clayton kk4iz via groups.io <KK4IZ284@...> wrote:
? I have a L-7 and neither meter is working. I have not checked to see if ?the watt meeter works.
On Jan 5, 2025, at 10:25?PM, Thomas W9TAB via groups.io <electron@...> wrote:
It¡¯s your HV meter scale adjustment R17 and is also shown on the schematic.?
Use a plastic tweaker.?
How far off is your meter??
Are the other scales correct? (Grid current, Watts)
If not your meter could be bad.?
Here is the excerpt from the manual:?
g.?
The high voltage adjustment potentiometer Rl7
is not user adjustable. If this needs readjust-
ment, return the L 7 to the factory for service
Drake knew how dangerous it was to perform this adjustment and didn¡¯t want the user to try to adjust it.?
Tom W9TAB?
On Jan 5, 2025, at 6:21?PM, Jim Shorney via groups.io <jimNU0C@...> wrote:
?
It appears that is your plate voltage calibration pot as was mentioned before. Check it against the schematic.
On Mon, 6 Jan 2025 00:16:12 +0000 (UTC)
"amfone via groups.io" <amfone20000@...> wrote:
In the back of the L7 next to the fan is a small hole with an adjustment control needing a small screwdriver to make the adjustment. I can't find anything in the manual about this, does anyone know what its for?
Thanks?
Tim
WB8UHZ
--?
73
-Jim
NU0C
73¡¯²õ
KK4IZ
Amateur Radio Operator
Warren Bryant?
124 Crestview Dr
Clanton,AL.??35045
Email:?KK4IZ284@...
Cell: 205-389-4170
|
Re: R4C Sherwood audio mod questions
I just took a quick look inside my late (28xxx) R-4C and it looks like there are circuits and structures that would interfere with a shield extension but I can hear the modulation a lot more when the slug/rod is out the back.
My receiver is totally stock except for having changed out the original AFG/RFG controls for a nice concentric plastic knob set that looks just like what Drake ¡°should have¡± put there.
I will likely leave things as they are, as it¡¯s more of a collector piece that I play with. ?It¡¯s similar in the auto world as a stock vs modified ¡°thing¡±. ?I am also not short on things that I need to do.
73,?
W1ES
On Mon, Jan 6, 2025 at 9:24 AM, Floyd - K8AC via groups.io < floydsense@...> wrote:
On Sun, Jan 5, 2025 at 10:18 PM, Steve Wedge, W1ES/4 wrote:
I¡¯m wondering if the buzz could be tamed by extending the shield can of the PTO ¡ª slide a second metal box over the end where the slug rod comes out.?
I wondered the same thing, but then I read a bit about the impact of the shape of the shielding on the effectiveness.? Apparently sharp corners are bad.? A cylindrical shape with the end sealed off was much better.? No idea how much the shielding is degraded by the sharp corners of a box structure.??
?
73, K8AC
|
Hi guys?
?
I am working on a R-4 receiver and am not satisfied with the AM mode , I suspect the AM- detector diods 1N625 as I had to replace the V10 / 12AX7A tube which is surrounded by 3 of these diods. What do you guys use as a substitute for the 1N625 diode?
?
73 Jan SM5MRQ
?
?
|
John, Great insight.
You care to share this document you speak of?
? ? ?Frank Krozel ? ? ? ? ? ?KG9H Life Member, ARRL ? ? (630) 924-1600 kg9hfrank@...
toggle quoted message
Show quoted text
On Jan 6, 2025, at 10:32?AM, John E. Beck via groups.io <wb0rxl@...> wrote:
Greetings.
?
Analog designer Jim Williams wrote, "The inside of a broken, but well-designed piece of test equipment is an
extraordinarily effective classroom."
?
I have found that true with my Drake B Twins (and many other radios and pieces of test equipment).? I have also found this group to be a treasure trove of insights.? I am admittedly a slow learner, but I crave understanding how things work.? ? Allow me to present an example.
?
The R-4B manual states,
"A portion of the audio signal as determined by R127 (AF Gain) is applied to Q7 (2N3394) and then to the audio output tube V7 (6EH5).?
?
From the web I learned V7 (6EH5) is for... "Audio output - a sharp cutoff, tetrode, 7 pin miniature construction.
?
After a search on this site I also learned this section is a self-balanced class A amplifier.
The 6EH5 is a tube with good output at low plate voltages. There are some equivalents, but not with the same basing.? Different biasing will introduce distortion. The 6EH5 does run hot.? A volt of ripple on the +160 VDC is about normal. The tube can get gassy causing the cathode voltage to rise and an increase in distortion. The 6EH5 isn't typically microphonic, the crackling you hear when tapping on the tube or on the chassis is a result of the tube socket contacts losing tension (contact pressure) due to heat. Often a shot of DeoxIT in each one will clear this up.
I am ending up with a sort of lab notebook with the insights others have gained that if needed in the future I can quickly reference to diagnose and repair an issue.? Or at the very least marvel at how well the engineers at Drake designed and built a wonderful radio.?
Bottom line:? THANK YOU for your contributions to this group in not only fixing past problems, but providing this poor soul with an education in electronics.
?
73
John
WB0RXL
?
?
?
?
|
Re: R4C Sherwood audio mod questions
I wonder if we could easily achieve a temporary change by using foil over the end. ?The shape would be somewhat irregular. ?
Right now, I have too many jobs lined up and have been fighting various bouts with either a severe cold or some other sort of malady.
Feel free to go ahead if I don¡¯t. ?The fact that it¡¯s being reported that the problem is worse at one end of the dial suggests a defect in shielding.
If I can achieve the same result without making holes in the chassis, I will always choose the non-surgical option.
On Mon, Jan 6, 2025 at 9:24 AM, Floyd - K8AC via groups.io < floydsense@...> wrote:
On Sun, Jan 5, 2025 at 10:18 PM, Steve Wedge, W1ES/4 wrote:
I¡¯m wondering if the buzz could be tamed by extending the shield can of the PTO ¡ª slide a second metal box over the end where the slug rod comes out.?
I wondered the same thing, but then I read a bit about the impact of the shape of the shielding on the effectiveness.? Apparently sharp corners are bad.? A cylindrical shape with the end sealed off was much better.? No idea how much the shielding is degraded by the sharp corners of a box structure.??
?
73, K8AC
|
Greetings.
?
Analog designer Jim Williams wrote, "The inside of a broken, but well-designed piece of test equipment is an
extraordinarily effective classroom."
?
I have found that true with my Drake B Twins (and many other radios and pieces of test equipment).? I have also found this group to be a treasure trove of insights.? I am admittedly a slow learner, but I crave understanding how things work.? ? Allow me to present an example.
?
The R-4B manual states,
"A portion of the audio signal as determined by R127 (AF Gain) is applied to Q7 (2N3394) and then to the audio output tube V7 (6EH5).?
?
From the web I learned V7 (6EH5) is for... "Audio output - a sharp cutoff, tetrode, 7 pin miniature construction.
?
After a search on this site I also learned this section is a self-balanced class A amplifier.
The 6EH5 is a tube with good output at low plate voltages. There are some equivalents, but not with the same basing.? Different biasing will introduce distortion.
The 6EH5 does run hot.? A volt of ripple on the +160 VDC is about normal.
The tube can get gassy causing the cathode voltage to rise and an increase in distortion.
The 6EH5 isn't typically microphonic, the crackling you hear when tapping on the tube or on the chassis is a result of the tube socket contacts losing tension (contact pressure) due to heat. Often a shot of DeoxIT in each one will clear this up.
I am ending up with a sort of lab notebook with the insights others have gained that if needed in the future I can quickly reference to diagnose and repair an issue.? Or at the very least marvel at how well the engineers at Drake designed and built a wonderful radio.
?
Bottom line:? THANK YOU for your contributions to this group in not only fixing past problems, but providing this poor soul with an education in electronics.
?
73
John
WB0RXL
?
?
?
?
|
As a side note, there appears to be two (2) styles of meter configurations. ?One has the metal shield and the other does not.
With power disconnected, take the case off and then remove the metal shield that covers the meters, look at the connections to the meters and make sure they are soldered.
I recently acquired an L7 from a Hamfest that didn¡¯t look like it had been used very much, the plate current meter wasn¡¯t working and I found the wire was just pushed through the meters solder lug and had never been soldered from the factory.?
The manual explains how to electronically check / calibrate both current meters without powering up the amp that would be a good troubleshooting start.?
On Jan 6, 2025, at 8:12?AM, Clayton kk4iz via groups.io <KK4IZ284@...> wrote:
? I have a L-7 and neither meter is working. I have not checked to see if ?the watt meeter works.
On Jan 5, 2025, at 10:25?PM, Thomas W9TAB via groups.io <electron@...> wrote:
It¡¯s
your HV meter scale adjustment R17 and is also shown on the schematic.?
Use a plastic tweaker.?
How far off is your meter??
Are the other scales correct? (Grid current, Watts)
If not your meter could be bad.?
Here is the excerpt from the manual:?
g.?The high voltage adjustment potentiometer Rl7
is not user adjustable. If this needs readjust-
ment, return the L 7 to the factory for service
Drake knew how dangerous it was to perform this adjustment and didn¡¯t want the user to try to adjust it.?
Tom W9TAB?
On Jan 5, 2025, at 6:21?PM, Jim Shorney via groups.io <jimNU0C@...> wrote:
?
It appears that is your plate voltage calibration pot as was mentioned before. Check it against the schematic.
On Mon, 6 Jan 2025 00:16:12 +0000 (UTC)
"amfone via groups.io" <amfone20000@...> wrote:
In the back of the L7 next to the fan is a small hole with an adjustment control needing a small screwdriver to make the adjustment. I can't find anything in the manual about this, does anyone know what its for?
Thanks?
Tim
WB8UHZ
--?
73
-Jim
NU0C
73¡¯²õ
KK4IZ
Amateur Radio Operator
Warren Bryant?
124 Crestview Dr
Clanton,AL.??35045
Email:?KK4IZ284@...
Cell: 205-389-4170
|
Drake Matched Pair of 6JB6's Sold
The Drake matched pair of 6JB6's have been sold.
?
Thanks,
?
Ron
K9RH
|
Hi all
?
Calibrator weaker as well.
Suspecting pin diode, anyone,know,where I can source some.
Im in?the UK.
Can't find any MPN 3404 or equivalent regards
Mike G3ZCC
|
Re: R4C Sherwood audio mod questions
In addition to trying Mu metal back 2011, Garey, K4OAH (SK), suggested placing a copper wire band around the power transformer to help absorb the magnetic field. I used copper strap as used on some transformers.? My notes show only a tiny improvement. More details are provided in the message exchange, linked below: ?
? Paul, W9AC ?
toggle quoted message
Show quoted text
From: [email protected] <[email protected]> On Behalf Of Floyd - K8AC via groups.io
Sent: Monday, January 6, 2025 9:24 AM
To: [email protected]
Subject: Re: [DRAKE-RADIO] R4C Sherwood audio mod questions? On Sun, Jan 5, 2025 at 10:18 PM, Steve Wedge, W1ES/4 wrote: I¡¯m wondering if the buzz could be tamed by extending the shield can of the PTO ¡ª slide a second metal box over the end where the slug rod comes out.?
I wondered the same thing, but then I read a bit about the impact of the shape of the shielding on the effectiveness.? Apparently sharp corners are bad.? A cylindrical shape with the end sealed off was much better.? No idea how much the shielding is degraded by the sharp corners of a box structure.??
|
Re: HYBRID NET UPDATE ( January 5, 2025 )
Whops, the title should have been DRAKE TECHNICAL NET.?
?
Mark, WB0IQK
|
With power disconnected, take the case off and then remove the metal shield that covers the meters, look at the connections to the meters and make sure they are soldered.
I recently acquired an L7 from a Hamfest that didn¡¯t look like it had been used very much, the plate current meter wasn¡¯t working and I found the wire was just pushed through the meters solder lug and had never been soldered from the factory.?
The manual explains how to electronically check / calibrate both current meters without powering up the amp that would be a good troubleshooting start.?
toggle quoted message
Show quoted text
On Jan 6, 2025, at 8:12?AM, Clayton kk4iz via groups.io <KK4IZ284@...> wrote:
? I have a L-7 and neither meter is working. I have not checked to see if ?the watt meeter works.
On Jan 5, 2025, at 10:25?PM, Thomas W9TAB via groups.io <electron@...> wrote:
It¡¯s
your HV meter scale adjustment R17 and is also shown on the schematic.?
Use a plastic tweaker.?
How far off is your meter??
Are the other scales correct? (Grid current, Watts)
If not your meter could be bad.?
Here is the excerpt from the manual:?
g.?The high voltage adjustment potentiometer Rl7
is not user adjustable. If this needs readjust-
ment, return the L 7 to the factory for service
Drake knew how dangerous it was to perform this adjustment and didn¡¯t want the user to try to adjust it.?
Tom W9TAB?
On Jan 5, 2025, at 6:21?PM, Jim Shorney via groups.io <jimNU0C@...> wrote:
?
It appears that is your plate voltage calibration pot as was mentioned before. Check it against the schematic.
On Mon, 6 Jan 2025 00:16:12 +0000 (UTC)
"amfone via groups.io" <amfone20000@...> wrote:
In the back of the L7 next to the fan is a small hole with an adjustment control needing a small screwdriver to make the adjustment. I can't find anything in the manual about this, does anyone know what its for?
Thanks?
Tim
WB8UHZ
--?
73
-Jim
NU0C
73¡¯²õ
KK4IZ
Amateur Radio Operator
Warren Bryant?
124 Crestview Dr
Clanton,AL.??35045
Email:?KK4IZ284@...
Cell: 205-389-4170
|
Floyd - K8AC
Thomas W9TAB
Mike Davidsohn G3ZCC
Paul Christensen