Check the VCO voltage.
I'll do this but after reviewing the complete alignment procedue in the manual, I'll also step through this to see if my unit is properly aligned (without making any adjustments). If it is not close, I'll do a complete alignment and then see where the other issues stand.? Rick K8EZB
?
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Re: Drake UV-3 transmit offset issue
Could it be that there is a programming arrangement somewhere on the board that selects the offset? Maybe a resistor jumper somewhere that has been installed?
73, Clint, VE3CMQ
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-----Original Message----- From: [email protected] < [email protected]> On Behalf Of mike bryce via groups.io Sent: Wednesday, 7 February 2024 09:41 To: [email protected]Subject: [DRAKE-RADIO] Drake UV-3 transmit offset issue Although I promised myself I¡¯d never work on one of these UV3s again¡ I can¡¯t say that anymore The one I have on my bench has a weird problem with the transmit offset. I set the dial to the local repeater, 147.18 and of course that¡¯s +600khz. However when you transmit, the offset is 1 mHz. I¡¯m expecting to see 147.7800 on TX. Instead, I get 148.7800. Switching to -600kHz, I get the same result, 1 mHz lower than it should be Simplex works as expected. Simple things out of the way. YES! I did clean the contacts. Yes, I do have the service manual. This problem is on the offset board. I have several boards and two work, and two don¡¯t. That also means the control head is working correctly (according to the drake manual) Of course I checked all the diodes on the offset board, and there are quite a few¡ Frankly, I¡¯m baffled by this problem. The service manual doesn¡¯t go into too much detail on how the offset is generated. Ideas anyone? Mike wb8vge
|
Hi Rick.
?
Have you checked the reference oscillator frequency?? It doesn¡¯t take much for this to put the entire system out of wack.? It¡¯s frequency should be 5.12MHz exactly. This is on the digital
board. I have seen some synthesized radio¡¯s being off quite a bit because the reference oscillator is out of adjustment, but this seem excessive.
?
I noticed that on the RF and Analog board there is another crystal oscillator running at around 18 MHz.? I can¡¯t read the print on the schematic, it could be 15 MHz.? This is controlled
by a DC voltage and this could put the RV-75 out quite a bit.? It doesn¡¯t seem to be monitored directly by the digital board.
?
I hope this helps somewhat.? These problems can drive one nuts, and often, it¡¯s something simple that¡¯s easily overlooked.
?
73, Clint, VE3CMQ
?
?
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From: [email protected] <[email protected]>
On Behalf Of Rick K8EZB via groups.io
Sent: Wednesday, 7 February 2024 13:55
To: [email protected]
Subject: Re: [DRAKE-RADIO] RV75 Issues: Part 3
?
Lucky for you that I took good pictures of mine. :)
Thanks, Jim. Yes, lucky for me!
I have done some additional troubleshooting.
The good news: static power supply regulation seems to be right on on both boards: 13v, 9v, and 5v, all well within Drake manual spec, however I have not yet checked this for variation over time. My guess is this will not be a problem.?
The bad news: further testing per the Drake manual Performance Checks section shows that the RV75 does not initialize to the published freq of 14.250.00, but is something like 14.441.00. High & low freq limits are also well above the published spec. Fixed freqs
also do not load correctly. At first glance all of these would seem to be related. So. somethong is not right on the digital board.
Given the farvorable results on the voltage checks, I will toubleshoot the digital board first and then come back to the drift issue reported earlier.?
I am already well past the point of knowing more about the RV75 than I ever intended!
Rick
K8EZB
|
Thanks for the all info Jim,
Yes, my TR7 has the fan fitted.
73, Dave
|
It sounds like the PLL is not locked. Check the VCO voltage. It should be between 4.5 and 7.5 Volts, stable, and move when you turn the main tuning knob. 73 -Jim NU0C On Wed, 07 Feb 2024 11:55:04 -0800 "Rick K8EZB" <frboswell@...> wrote:
Lucky for you that I took good pictures of mine. :)
Thanks, Jim. Yes, lucky for me!
I have done some additional troubleshooting.
The good news: static power supply regulation seems to be right on on both boards: 13v, 9v, and 5v, all well within Drake manual spec, however I have not yet checked this for variation over time. My guess is this will not be a problem.
The bad news: further testing per the Drake manual Performance Checks section shows that the RV75 does not initialize to the published freq of 14.250.00, but is something like 14.441.00. High & low freq limits are also well above the published spec. Fixed freqs also do not load correctly. At first glance all of these would seem to be related. So. somethong is not right on the digital board.
Given the farvorable results on the voltage checks, I will toubleshoot the digital board first and then come back to the drift issue reported earlier.
I am already well past the point of knowing more about the RV75 than I ever intended!
Rick
K8EZB
-- 73 -Jim NU0C
|
Lucky for you that I took good pictures of mine. :)
Thanks, Jim. Yes, lucky for me! I have done some additional troubleshooting. The good news: static power supply regulation seems to be right on on both boards: 13v, 9v, and 5v, all well within Drake manual spec, however I have not yet checked this for variation over time. My guess is this will not be a problem.? The bad news: further testing per the Drake manual Performance Checks section shows that the RV75 does not initialize to the published freq of 14.250.00, but is something like 14.441.00. High & low freq limits are also well above the published spec. Fixed freqs also do not load correctly. At first glance all of these would seem to be related. So. somethong is not right on the digital board. Given the farvorable results on the voltage checks, I will toubleshoot the digital board first and then come back to the drift issue reported earlier.? I am already well past the point of knowing more about the RV75 than I ever intended! Rick K8EZB
|
Jim
Thank you for your comments.? Very helpful.? And than you to Dave for raising the topic.? I know now the cheap options with mine.
Nigel
On Wed, Feb 7, 2024 at 7:04?PM Jim Shorney < jimNU0C@...> wrote:
They all have some small amount of drift. How much depends partly on how well the PTO has aged and the accuracy of the factory temperature compensation. I found that mine have been plenty stable enough to run digital modes like JT65, JT9, FT8, etc. I have wondered if it might help to replace the Zener in the PTO with a high stability precision regulator. That may be a project for "someday". Of course the 7-line radios will have a different warm-up curve than the radios that glow in the dark, but every radio has a warm-up time spec. I tend to just let my 7-line run 24/7.
One point of trivia that is not thought about much is temperature variation over T/R cycles. Do you have the optional fan on the back? I did some measurements some years ago and found that a properly installed fan pulling air out of the radio does actually help keep the temperature inside the radio near the frequency determining parts more stable across T/R cycles, especially if you are running hard. The heat from the PA deck has to go somewhere, and with no fan some of that heat makes its way into the rest of the radio.
73
-Jim
NU0C
On Wed, 07 Feb 2024 05:09:07 -0800
"Dave G0GKH via " <g0gkh=[email protected]> wrote:
> Hi,
>
> New to the forum here.
>
> I've had a C line for some time but recently have got a TR7.
>
> From switch on, there is a gradual slow drift downwards in frequency of both transmit and receive.
>
> During short QSO's this isn't noticeable, but longer QSO's I end up getting comments from the station I'm working.
>
> Over the first hour or so the frequency goes down by approx. 1.6khz, after this it seems to stabilise.
>
> Is this normal for the the TR7, or is it a sign of something not right?
>
> It surprised me that the drift seems greater than my T4XC/R4C line-up
>
> Any thoughts appreciated
>
> 73, Dave G0GKH
>
>
>
>
>
--
73
-Jim
NU0C
|
They all have some small amount of drift. How much depends partly on how well the PTO has aged and the accuracy of the factory temperature compensation. I found that mine have been plenty stable enough to run digital modes like JT65, JT9, FT8, etc. I have wondered if it might help to replace the Zener in the PTO with a high stability precision regulator. That may be a project for "someday". Of course the 7-line radios will have a different warm-up curve than the radios that glow in the dark, but every radio has a warm-up time spec. I tend to just let my 7-line run 24/7. One point of trivia that is not thought about much is temperature variation over T/R cycles. Do you have the optional fan on the back? I did some measurements some years ago and found that a properly installed fan pulling air out of the radio does actually help keep the temperature inside the radio near the frequency determining parts more stable across T/R cycles, especially if you are running hard. The heat from the PA deck has to go somewhere, and with no fan some of that heat makes its way into the rest of the radio. 73 -Jim NU0C On Wed, 07 Feb 2024 05:09:07 -0800 "Dave G0GKH via groups.io" <g0gkh@...> wrote: Hi,
New to the forum here.
I've had a C line for some time but recently have got a TR7.
From switch on, there is a gradual slow drift downwards in frequency of both transmit and receive.
During short QSO's this isn't noticeable, but longer QSO's I end up getting comments from the station I'm working.
Over the first hour or so the frequency goes down by approx. 1.6khz, after this it seems to stabilise.
Is this normal for the the TR7, or is it a sign of something not right?
It surprised me that the drift seems greater than my T4XC/R4C line-up
Any thoughts appreciated
73, Dave G0GKH
-- 73 -Jim NU0C
|
Lucky for you that I took good pictures of mine. :) As found, set for 7 line. 73 -Jim NU0C On Wed, 07 Feb 2024 08:17:17 -0800 "Rick K8EZB" <frboswell@...> wrote: Update:
Further testing in accordance with manual checkout procedures indicates a possible digital board issue unrelated to the previously identified freq drift problem.
Before I take the troubleshooting much farther, I'd like to confirm the correct position of the P107 jumper on the digital board. This jumper apparently is used to accommodate differences between the 7-line radios and 5-line radios; the RV75 can be used with either by setting this jumper correctly. I am unable to find definitive info in my documentation on the correct position of this jumper for the TR7. The photo below illustrates how this jumper was set when I received the RV75. Can anyone confirm this is the correct setting for 7-line radios?
Thanks,
Rick
K8EZB
|
It bears noting that the original specification for frequency stability for the TR7 is less than 1 kHz during the first hour and less than 150 Hz / hr thereafter.
I know that we have all become spoilt from using modern equipment that has much tighter tolerances but unless you're using these sets for modes that demand high precision, the original spec is reasonable.? Of course, everyone has their own desire for how they use the equipment.? My point is that if it drifts less than 1 kHz in the first hour, it is operating within spec and you likely have no bad components.
73,
Steve Wedge, W1ES/4
Time flies like an arrow.? Fruit flies like a banana.
Sent with secure email.
On Wednesday, February 7th, 2024 at 9:57 AM, Dale Parfitt <PARINC1@...> wrote:
I also recently acquired a loaded TR-7. It came with a German version of a VFO stabilizer, and it keeps the TR-7 within 10Hz from dead cold start. Elcon is making the Elcon 34 frequency stabilizer. I used one on an RV-4C and am very happy with the results.
Dale W4OP
|
Update: Further testing in accordance with manual checkout procedures indicates a possible digital board issue unrelated to the previously identified freq drift problem. Before I take the troubleshooting much farther, I'd like to confirm the correct position of the P107 jumper on the digital board. This jumper apparently is used to accommodate differences between the 7-line radios and 5-line radios; the RV75 can be used with either by setting this jumper correctly. I am unable to find definitive info in my documentation on the correct position of this jumper for the TR7. The photo below illustrates how this jumper was set when I received the RV75. Can anyone confirm this is the correct setting for 7-line radios?? Thanks, Rick K8EZB 
|
Re: Drake UV-3 transmit offset issue
Ken
that it does. I get the 1.6mHz offset. Never gave it any thought about 220. The one I¡¯m working on does not have the 220 board. However, the offset board might think it does. Good info
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On Feb 7, 2024, at 10:54 AM, Ken, W8EK < KenW8EK@...> wrote:
Hi Mike,
You are getting a 1.6 MHz offset. ?That is
the offset that is normally used on 220 MHz.
Is it possible that somehow (don't ask me how)
that the crazy thing thinks you are on 220 MHz
and gives you that offset?
Just something to check.
Thanks.
73,
Ken, W8EK
|
Re: Drake UV-3 transmit offset issue
Hi Mike,
You are getting a 1.6 MHz offset. That is
the offset that is normally used on 220 MHz.
Is it possible that somehow (don't ask me how)
that the crazy thing thinks you are on 220 MHz
and gives you that offset?
Just something to check.
Thanks.
73,
Ken, W8EK
mike bryce wrote on 2/7/2024 10:41 AM:
toggle quoted message
Show quoted text
Although I promised myself I¡¯d never work on one of these UV3s again¡ I can¡¯t say that anymore
The one I have on my bench has a weird problem with the transmit offset.
I set the dial to the local repeater, 147.18 and of course that¡¯s +600khz. However when you transmit, the offset is 1 mHz.
I¡¯m expecting to see 147.7800 on TX. Instead, I get 148.7800. Switching to -600kHz, I get the same result, 1 mHz lower than it should be
Simplex works as expected.
Simple things out of the way. YES! I did clean the contacts. Yes, I do have the service manual.
This problem is on the offset board. I have several boards and two work, and two don¡¯t. That also means the control head is working correctly (according to the drake manual)
Of course I checked all the diodes on the offset board, and there are quite a few¡
Frankly, I¡¯m baffled by this problem. The service manual doesn¡¯t go into too much detail on how the offset is generated.
Ideas anyone?
Mike wb8vge
|
Drake UV-3 transmit offset issue
Although I promised myself I¡¯d never work on one of these UV3s again¡ I can¡¯t say that anymore
The one I have on my bench has a weird problem with the transmit offset.
I set the dial to the local repeater, 147.18 and of course that¡¯s +600khz. However when you transmit, the offset is 1 mHz.
I¡¯m expecting to see 147.7800 on TX. Instead, I get 148.7800. Switching to -600kHz, I get the same result, 1 mHz lower than it should be
Simplex works as expected.
Simple things out of the way. YES! I did clean the contacts. Yes, I do have the service manual.
This problem is on the offset board. I have several boards and two work, and two don¡¯t. That also means the control head is working correctly (according to the drake manual)
Of course I checked all the diodes on the offset board, and there are quite a few¡
Frankly, I¡¯m baffled by this problem. The service manual doesn¡¯t go into too much detail on how the offset is generated.
Ideas anyone?
Mike wb8vge
|
I also recently acquired a loaded TR-7. It came with a German version of a VFO stabilizer, and it keeps the TR-7 within 10Hz from dead cold start. Elcon is making the Elcon 34 frequency stabilizer. I used one on an RV-4C and am very happy with the results.
Dale W4OP
|
Hi,
New to the forum here.
I've had a C line for some time but recently have got a TR7.
From switch on, there is a gradual slow drift downwards in frequency of both transmit and receive.
During short QSO's this isn't noticeable, but longer QSO's I end up getting comments from the station I'm working.
Over the first hour or so the frequency goes down by approx. 1.6khz, after this it seems to stabilise.
Is this normal for the the TR7, or is it a sign of something not right?
It surprised me that the drift seems greater than my T4XC/R4C line-up
Any thoughts appreciated
73, Dave G0GKH
|
Re: Looking for L75 amp meter replacement.
Sounds great, Rob! ?I didn¡¯t change anything with mine other than the scale. Mine said ¡°200uA FS¡± at the bottom of the scale. I didn¡¯t try calibrating it, as it appears to be showing the expected values.?
My amp is an L7, so that may be the difference. You probably don¡¯t need 1A readings at full scale.?
Glad it worked and glad you got one before they were gone!
73,
Steve Wedge, W1ES/4
Time flies like an arrow. Fruit flies like a banana.
On Tue, Feb 6, 2024 at 22:15, Roberto - YS1RS via groups.io < ys1rs@...> wrote: Have progress to share here.
Received the meter I bought from eBay.
Perfect fit as it was an 83T as the original.
The last one available. It was a 0-300 DC Amp. meter.
Came with an external resistor which I removed but guess what?
The original meter used by Drake for the L75 was 200 uA full scale.
The one received was 1 mA full scale. Tested it with a small circuit I put together and one amperimeter.
Opened it and couldn't find any internal resistor or anything like that inside the transparent meter.
Saw also a few improvements on the movement when compared with the original used on the Drake L75.
Looks like they corrected the issues that made the 83T model, fail on Drakes.
To make things brief...? the internal wire used on the internal meter coil was different than the one used for the 200 uA version.
As expected, all readings were pretty low, when installed it in the L75..
At the end of the day, I had to re-calculate all the meter section resistor network.
After installing the new resistors, went through the meter calibration process shown in the manual.
Have finished replacing all the resistors and now I have a fully functional meter that is a joy to see it working.
Previously, I was adjusting the Amp only by using an external Wattmeter. Actually, the Wattmeter is an Drake MN-2700.
Now, I can read Plate Voltage, Plate and Grid current and it matches what the manual says.
The Relative Output also matches perfectly.
Have written down on my notes the new values installed in case the XYL sells the Amp in the future LOL.
Anyway, wanted to share with you my experience.
Thank you all who helped me finding a solution to my Drake L75 problem.
Learnt a lot in the process.
73
Rob
YS1RS
|
Re: Looking for L75 amp meter replacement.
Have progress to share here.
Received the meter I bought from eBay.
Perfect fit as it was an 83T as the original.
The last one available. It was a 0-300 DC Amp. meter.
Came with an external resistor which I removed but guess what?
The original meter used by Drake for the L75 was 200 uA full scale.
The one received was 1 mA full scale. Tested it with a small circuit I put together and one amperimeter.
Opened it and couldn't find any internal resistor or anything like that inside the transparent meter.
Saw also a few improvements on the movement when compared with the original used on the Drake L75.
Looks like they corrected the issues that made the 83T model, fail on Drakes.
To make things brief...? the internal wire used on the internal meter coil was different than the one used for the 200 uA version.
As expected, all readings were pretty low, when installed it in the L75..
At the end of the day, I had to re-calculate all the meter section resistor network.
After installing the new resistors, went through the meter calibration process shown in the manual.
Have finished replacing all the resistors and now I have a fully functional meter that is a joy to see it working.
Previously, I was adjusting the Amp only by using an external Wattmeter. Actually, the Wattmeter is an Drake MN-2700.
Now, I can read Plate Voltage, Plate and Grid current and it matches what the manual says.
The Relative Output also matches perfectly.
Have written down on my notes the new values installed in case the XYL sells the Amp in the future LOL.
Anyway, wanted to share with you my experience.
Thank you all who helped me finding a solution to my Drake L75 problem.
Learnt a lot in the process.
73
Rob
YS1RS
|
On Tue, Feb 6, 2024 at 11:26 AM, Jim Shorney wrote:
For slow drift I would suspect a problem with one of the voltage regulators or maybe the master crystal oscillator.
After further review (of the ckt diag and ToO section of the manual, my first guess is voltage regulation of the VCO or VCXO.Basically eveything works, just some slight drift. I'll change over from soldering iron to scope, VOM, and counter and see what I can find. BTW: I emailed Ron, WB4HFM, to see if he could suggest things to look for or perhaps take a look himself and he replied he no longer works on RV75's. So it looks like I am on my own, but with a distant but able assist from the assembled multitude here! Rick K8EZB
|
Thanks Tom.
I chose to log in with google.?
73' Sjaak PA3GHL.
|
Jim Shorney
Roberto - YS1RS