The TP114 test point should be a good place to get the frequency
Clint, Yes, figured this out. Using the freq counter in my Tek 2465BCT scope. The good news: the Reference Oscillator is right on freq: 1.28000 MHz at TP114 The bad news: the VCXO appears not to be working (oscillating). No signal at VCXO Test Point on RF & Analog board. This likely explains the symptoms I am seeing. Preliminary investigation shows no reason for this; however I am just getting started with the troubleshooting. Could be many causes including more failed axial lead ceramic caps, bad xtal, etc. . This look like a substantial challenge to troubleshoot.? Rick K8EZB
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I used these guys for my L4B. Work pretty good.?
73 Mark W0NCL
On Thursday, February 8, 2024 at 08:53:02 AM CST, Bob W8RID <davet354tfd@...> wrote:
I have an L-4B Amp. Love it!!
The bulbs on my meters are starting to get dim. Want to replace them with LED's.
Just inquiring if anyone has done this and is there any tricks that I need to know to add the LED's?
I have some that already have the resistor with them. Just dont want to wire them wrong.
Thanks
Bob
W8RID
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I have an L-4B Amp. Love it!!
The bulbs on my meters are starting to get dim. Want to replace them with LED's.
Just inquiring if anyone has done this and is there any tricks that I need to know to add the LED's?
I have some that already have the resistor with them. Just dont want to wire them wrong.
Thanks
Bob
W8RID
|
Hi Rick,
?
The TP114 test point should be a good place to get the frequency.? This is to prevent loading on the oscillator.? All I have got to go on is the schematic which isn¡¯t a very good copy.?
It¡¯s all I was able to find on the net.? Use an as accurate a frequency counter as you can get your hands on.? The cheap ones, unless they are GPS disciplined can get you close, maybe withing a 100Hz or so of the operating frequency.? GPS disciplined ones
can get you down to the Hertz level.
?
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 15:13
To: [email protected]
Subject: Re: [DRAKE-RADIO] RV75 Issues: Part 3
?
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.
Clint,
Havent done this yet but its next on my list. But a bit of confusion here. The RV75 manual Section 5-5.3 REFERENCE OSCILLATOR ADJUSTMENT calls for a freq of 1.280000 MHz AT tp114, while your guidance is 5.12 MHz. On the schematic it appears tha TP114 is after
a divider stage so this may account for the difference. I can see that this can create major problems if not set correctly. Thanks for the tip!
Rick
K8EZB
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Yes, my pics are pre-recap. Capars are a ticking bomb. Check often for strange spurs. On Wed, 7 Feb 2024 13:54:53 -0800 "VE7PS" <ve7ps@...> wrote: Jim can confirm, but I assume that the P107 pic Jim sent you was from
before he changed the CAPAR caps. They look identical to the ones I still
have in my RV-75 -- 73 -Jim NU0C
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Will peak out once in a while to find out how this ends
Peter, I have downloaded the data sheets for the digital integrated circuits on the digital board and studied the ToO section of the manual until I can almost recite it verbatim. As I look at the troubleshooting data I have compiled so far in the context of the ToO explanations I am increasingly of the opinion that the digital circuitry is likley working as designed. If so, this points strongly to "alignment" iissues, especially the Reference Oscillator frequency setting.? As I currently understand the operation of the RV75,? it provides only an (synthesized)? RF frequency to the TR7, much like the RV7 (which is not synthesized). The TR7 converts this RF to a digital frequency display when the RV75 is connected and in start up, TUNE or FIXED modes, or at the end of the tuning range. If this RV75 RF signal is the "wrong" frequency due to misalignment, the TR7 will display the "wrong" frequency at start up, in TUNE, and FIXED, and at the limits of the tuning range, as I am seeing. All this is probably elementary to old RV75 hands, but to a newbie like me who is seeing all this for the first tiem, it is a bit of a revelation. I strongly suspect that I will find my problems in the analog portions of the circuitry and that correct? alignment will?be an important part of the solution. So far, this is little more than a SWAG. We'll see soon enough. Rick K8EZB
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On Wed, Feb 7, 2024 at 02:16 PM, VE7PS wrote:
Duhhhh and you told me that!? Memory is great....just really short.
?
Not to worry! My memory is even shorter! Rick K8EZB
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Rick:
Duhhhh and you told me that!? Memory is great....just really short.
I'll crawl back under my rock now.? Will peak out once in a while to find out how this ends though.
73 Peter VE7PS
On Wed, Feb 7, 2024 at 01:55 PM, VE7PS wrote:
FWIW...I notice you have?different electrolytic caps in there - i.e. not CAPAR?
Peter,
I have changed out all electrolytics in accordeance with a capacitor parts list provided by Jim. No Capar, mixed brands.
?If so...hopefully all done correctly!
Well ... yes, hopefully. All new caps tested before installing? for capacitance and ESR. Then inspected at least 2 million times for correct installation including electrical integrity of solder joint. This doesn't mean that the 2,000,001th inspection wont find an error. I try hard but sometimes make mistakes!
Rick
K8EZB
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Re: Drake UV-3 transmit offset issue
Hi Mike. Looking quickly at the Offset Bd schematic, lines T, L, M, N should not be changing state in 140, 220 modes as these control the 5 Mhz offset for 440 Mhz. The 140, 220 and 10.7 Mhz (receiver LO) offsets are handled thru the W, X, 18, S control lines. In receive, the W line is low, the rest (X, 18, S) are driven high. In 600 Khz offset, lines X & 18 are high, the other two are low. 1.6 Mhz offset (220 mode), all 4 lines are high. Not clear on offset direction, as (-) offset requires diodes 1,2,3, 40,41,42 installed, but shown as optional on the schematic, should be standard ? If these signals look good, need to check the programmable dividers and see what is happening.?
Paul - W2NMI
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On Wed, Feb 7, 2024 at 01:55 PM, VE7PS wrote:
FWIW...I notice you have?different electrolytic caps in there - i.e. not CAPAR?
Peter, I have changed out all electrolytics in accordeance with a capacitor parts list provided by Jim. No Capar, mixed brands.
?If so...hopefully all done correctly!
Well ... yes, hopefully. All new caps tested before installing? for capacitance and ESR. Then inspected at least 2 million times for correct installation including electrical integrity of solder joint. This doesn't mean that the 2,000,001th inspection wont find an error. I try hard but sometimes make mistakes! Rick K8EZB
|
Here is a photo of my RV-75 which is set for a TR7. So yours seems to be ok. Some where I have some notes on the position so will have to look. 73? Bob 
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Rick:
FWIW...I notice you have?different electrolytic caps in there - i.e. not CAPAR?? Do they look original, I wonder, or have they been changed? If so...hopefully all done correctly!
Jim can confirm, but I assume that the P107 pic Jim sent you was from before he changed the CAPAR caps.? They look identical to the ones I still have in my RV-75.
Reading with interest...but flying a bit blind here....? GL!
73 Peter? VE7PS
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.
Clint,
Havent done this yet but its next on my list. But a bit of confusion here. The RV75 manual Section 5-5.3 REFERENCE OSCILLATOR ADJUSTMENT calls for a freq of 1.280000 MHz AT tp114, while your guidance is 5.12 MHz. On the schematic it appears tha TP114 is after a divider stage so this may account for the difference. I can see that this can create major problems if not set correctly. Thanks for the tip!
Rick
K8EZB
|
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.
Clint, Havent done this yet but its next on my list. But a bit of confusion here. The RV75 manual Section 5-5.3 REFERENCE OSCILLATOR ADJUSTMENT calls for a freq of 1.280000 MHz AT tp114, while your guidance is 5.12 MHz. On the schematic it appears tha TP114 is after a divider stage so this may account for the difference. I can see that this can create major problems if not set correctly. Thanks for the tip! Rick K8EZB
|
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
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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
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Bob W8RID
Jim Shorney