Re: Drake TR-7 - A repair journey

Wow, Great dedication!

Congratulations.

Marty

KL7AM

From: "atlasstuff" <g4fph@...>
To: "DRAKE-RADIO" <[email protected]>
Sent: Thursday, February 8, 2024 9:08:37 AM
Subject: [DRAKE-RADIO] Drake TR-7 - A repair journey

Hi to all in the group. Below some findings from my repair journey with a TR-7 that you may find interesting.

A couple of years ago, I acquired a Drake 'job lot' on eBay. Until this week, the TR-7 transceiver (an early one in the low 1000 s/n range) had just gathered dust. I looked at the radio when I got it and knew it was going to be trouble. Externally there were missing case screws; some screws broken off in their bottom chassis nuts; and sheet metal screws of various sizes used in threaded holes. Internally, I could tell just by looking at the power supply board that the person(s) who had worked on it previously should never have been allowed to use a soldering iron. Maybe is was a gas torch they actually used:-(

This week, I decided the time had come to fix the thing. Starting symptoms were panel lights only, no signs of life in IF and AF stages and the frequency display tumbling uncontrollably. Here's what I found:

On the Power Supply board. Series pass transistor for the 10-Volt rail and the 5-Volt regulator were floating in free space; Ferrite core on the inverter transformer had come apart, giving no / low 24- and -5-Volt supplies; Tracks lifted / open-circuit where the +10 V SET and USB PBT pots had been replaced. Could really use a new power supply board, but patched it up for now.

On the IF Selectivity board. Several large solder splashes bridging PCB tracks, presumably put there when additional IF filters were installed, and which appeared to be the source of a short on the +10-Volt R rail.

On the Transmit Exciter board. Switching transistor for the 10-Volt R rail open-circuit. 2N4402 replaced with ZTX550 from junk box.

On the chassis. The scrapes around the band-switch on the rear panel told me the band switch had been removed previously. The switch wafers along the shaft were FUBAR, causing the synthesiser to be mis-programmed; the VCO to be on 'HI' range when the radio was set to the 'low' bands and loss of RF signal paths through the LPF and HPF. So bad was the mess, I almost made a service tool that could be used to flip the indexing on individual wafers 0 / 180-degrees. Eventually I made do with using the Drake band switch shaft, inserting in alternately (and only part-way) through the rear- and front-panel holes until all wafers were indexed correctly. It took a long time, not helped by not being able to see where the wipers on many of the wafers were pointing. The tension on the bandswitch as it turns is very weak. I can't understand how the single piece of (spring steel?) wire can exert much force on the switch shaft to improve matters. Perhaps there's something missing / broken here? Any knowledge from the group here?

On the Pass Band Tuning board, the CMOS switch that processes the PBT voltages was faulty. MC14016 replaced with CD4066, in IC socket, just in case;-) The PBT voltage being fed to the VCXO was nonsense with any position of the mode switch; whether any of the PBT pots on the power supply board were adjusted; and whether PBT was engaged, or not. With the fault present, the 'toppy' / restricted frequency response of the noise out of the receiver sounded like the PBT control was set hard to one end.

On the HPF daughter board, bridged tracks around the PIN diodes and a brown stain on the board where something had got hot. The UM9401 PIN diodes had been replaced with an assortment of silicon rectifier diodes. I have some sympathy here. Access to the rear of the board in-situ to make a repair job is not easy. I removed all three diodes, cleaned the rear of the board with solder wick and re-built the three diodes in a Christmas tree on the front of the board. I did not have any of the original PIN diodes. Looking at this article I substituted 1N4007. They work well on RX, but remains to be seen whether they will be good enough on TX. Any group experiences here?

On the Digital Display board, dry solder joints on the rear Molex connector.

Evidence of contact cleaner spray sticky residue near all Molex connectors in the card cage. Can't believe this was the right stuff for the job. Cleaned up and selective use of DeoxIT D100L from a needle dropper.

With all of that done, the receiver is now fully working and sounds good. The next part of the journey will be the transmitter - I feel I am overdue some luck here!

My thanks to:

Stefan, DL7MAJ, whose YouTube videos inspired me to actually start a job I had been putting off for too long and for his 'cheat sheet' of bandswitch BCD values.
Tom Evans for his 'Parent Board pinout' document and Jim Shorney's diagram of 'Parent Board Pin Numbering', both in the 'Files' section of the group, were / are essential reading.
Mike, G3ZCC, whose hi-res scans of the circuits were just right for printing and scribbling on.

Regards,

Mark, G4FPH.

Re: Drake TR-7 - A repair journey

#76011

开云体育

What a job!!!?

Thanks for sharing your journey and good luck with the TX!

I also brought back life to two ?junk TR7s“. (Yours sounds really terrible…) ?You learn a lot about the radio that way. ?And you appreciate that there isn’t really much that can’t be repaired in a TR7.?

73, Dieter DL5RDO

Von meinem iPhone gesendet

Show quoted text

Am 08.02.2024 um 19:08 schrieb atlasstuff <g4fph@...>:

?Hi to all in the group. Below some findings from my repair journey with a TR-7 that you may find interesting.

A couple of years ago, I acquired a Drake 'job lot' on eBay. Until this week, the TR-7 transceiver (an early one in the low 1000 s/n range) had just gathered dust. I looked at the radio when I got it and knew it was going to be trouble. Externally there were missing case screws; some screws broken off in their bottom chassis nuts; and sheet metal screws of various sizes used in threaded holes. Internally, I could tell just by looking at the power supply board that the person(s) who had worked on it previously should never have been allowed to use a soldering iron. Maybe is was a gas torch they actually used:-(

This week, I decided the time had come to fix the thing. Starting symptoms were panel lights only, no signs of life in IF and AF stages and the frequency display tumbling uncontrollably. Here's what I found:

On the Power Supply board. Series pass transistor for the 10-Volt rail and the 5-Volt regulator were floating in free space; Ferrite core on the inverter transformer had come apart, giving no / low 24- and -5-Volt supplies; Tracks lifted / open-circuit where the +10 V SET and USB PBT pots had been replaced. Could really use a new power supply board, but patched it up for now.

On the IF Selectivity board. Several large solder splashes bridging PCB tracks, presumably put there when additional IF filters were installed, and which appeared to be the source of a short on the +10-Volt R rail.

On the Transmit Exciter board. Switching transistor for the 10-Volt R rail open-circuit. 2N4402 replaced with ZTX550 from junk box.

On the chassis. The scrapes around the band-switch on the rear panel told me the band switch had been removed previously. The switch wafers along the shaft were FUBAR, causing the synthesiser to be mis-programmed; the VCO to be on 'HI' range when the radio was set to the 'low' bands and loss of RF signal paths through the LPF and HPF. So bad was the mess, I almost made a service tool that could be used to flip the indexing on individual wafers 0 / 180-degrees. Eventually I made do with using the Drake band switch shaft, inserting in alternately (and only part-way) through the rear- and front-panel holes until all wafers were indexed correctly. It took a long time, not helped by not being able to see where the wipers on many of the wafers were pointing. The tension on the bandswitch as it turns is very weak. I can't understand how the single piece of (spring steel?) wire can exert much force on the switch shaft to improve matters. Perhaps there's something missing / broken here? Any knowledge from the group here?

On the Pass Band Tuning board, the CMOS switch that processes the PBT voltages was faulty. MC14016 replaced with CD4066, in IC socket, just in case;-) The PBT voltage being fed to the VCXO was nonsense with any position of the mode switch; whether any of the PBT pots on the power supply board were adjusted; and whether PBT was engaged, or not. With the fault present, the 'toppy' / restricted frequency response of the noise out of the receiver sounded like the PBT control was set hard to one end.

On the HPF daughter board, bridged tracks around the PIN diodes and a brown stain on the board where something had got hot. The UM9401 PIN diodes had been replaced with an assortment of silicon rectifier diodes. I have some sympathy here. Access to the rear of the board in-situ to make a repair job is not easy. I removed all three diodes, cleaned the rear of the board with solder wick and re-built the three diodes in a Christmas tree on the front of the board. I did not have any of the original PIN diodes. Looking at this article I substituted 1N4007. They work well on RX, but remains to be seen whether they will be good enough on TX. Any group experiences here?

On the Digital Display board, dry solder joints on the rear Molex connector.

Evidence of contact cleaner spray sticky residue near all Molex connectors in the card cage. Can't believe this was the right stuff for the job. Cleaned up and selective use of DeoxIT D100L from a needle dropper.

With all of that done, the receiver is now fully working and sounds good. The next part of the journey will be the transmitter - I feel I am overdue some luck here!

My thanks to:

Stefan, DL7MAJ, whose YouTube videos inspired me to actually start a job I had been putting off for too long and for his 'cheat sheet' of bandswitch BCD values.

Tom Evans for his 'Parent Board pinout' document and Jim Shorney's diagram of 'Parent Board Pin Numbering', both in the 'Files' section of the group, were / are essential reading.

Mike, G3ZCC, whose hi-res scans of the circuits were just right for printing and scribbling on.

Regards,

Mark, G4FPH.

Drake TR-7 - A repair journey

#76010

Hi to all in the group. Below some findings from my repair journey with a TR-7 that you may find interesting.

A couple of years ago, I acquired a Drake 'job lot' on eBay. Until this week, the TR-7 transceiver (an early one in the low 1000 s/n range) had just gathered dust. I looked at the radio when I got it and knew it was going to be trouble. Externally there were missing case screws; some screws broken off in their bottom chassis nuts; and sheet metal screws of various sizes used in threaded holes. Internally, I could tell just by looking at the power supply board that the person(s) who had worked on it previously should never have been allowed to use a soldering iron. Maybe is was a gas torch they actually used:-(

This week, I decided the time had come to fix the thing. Starting symptoms were panel lights only, no signs of life in IF and AF stages and the frequency display tumbling uncontrollably. Here's what I found:

On the Power Supply board. Series pass transistor for the 10-Volt rail and the 5-Volt regulator were floating in free space; Ferrite core on the inverter transformer had come apart, giving no / low 24- and -5-Volt supplies; Tracks lifted / open-circuit where the +10 V SET and USB PBT pots had been replaced. Could really use a new power supply board, but patched it up for now.

On the IF Selectivity board. Several large solder splashes bridging PCB tracks, presumably put there when additional IF filters were installed, and which appeared to be the source of a short on the +10-Volt R rail.

On the Transmit Exciter board. Switching transistor for the 10-Volt R rail open-circuit. 2N4402 replaced with ZTX550 from junk box.

On the chassis. The scrapes around the band-switch on the rear panel told me the band switch had been removed previously. The switch wafers along the shaft were FUBAR, causing the synthesiser to be mis-programmed; the VCO to be on 'HI' range when the radio was set to the 'low' bands and loss of RF signal paths through the LPF and HPF. So bad was the mess, I almost made a service tool that could be used to flip the indexing on individual wafers 0 / 180-degrees. Eventually I made do with using the Drake band switch shaft, inserting in alternately (and only part-way) through the rear- and front-panel holes until all wafers were indexed correctly. It took a long time, not helped by not being able to see where the wipers on many of the wafers were pointing. The tension on the bandswitch as it turns is very weak. I can't understand how the single piece of (spring steel?) wire can exert much force on the switch shaft to improve matters. Perhaps there's something missing / broken here? Any knowledge from the group here?

On the Pass Band Tuning board, the CMOS switch that processes the PBT voltages was faulty. MC14016 replaced with CD4066, in IC socket, just in case;-) The PBT voltage being fed to the VCXO was nonsense with any position of the mode switch; whether any of the PBT pots on the power supply board were adjusted; and whether PBT was engaged, or not. With the fault present, the 'toppy' / restricted frequency response of the noise out of the receiver sounded like the PBT control was set hard to one end.

On the HPF daughter board, bridged tracks around the PIN diodes and a brown stain on the board where something had got hot. The UM9401 PIN diodes had been replaced with an assortment of silicon rectifier diodes. I have some sympathy here. Access to the rear of the board in-situ to make a repair job is not easy. I removed all three diodes, cleaned the rear of the board with solder wick and re-built the three diodes in a Christmas tree on the front of the board. I did not have any of the original PIN diodes. Looking at this article I substituted 1N4007. They work well on RX, but remains to be seen whether they will be good enough on TX. Any group experiences here?

On the Digital Display board, dry solder joints on the rear Molex connector.

Evidence of contact cleaner spray sticky residue near all Molex connectors in the card cage. Can't believe this was the right stuff for the job. Cleaned up and selective use of DeoxIT D100L from a needle dropper.

With all of that done, the receiver is now fully working and sounds good. The next part of the journey will be the transmitter - I feel I am overdue some luck here!

My thanks to:

Stefan, DL7MAJ, whose YouTube videos inspired me to actually start a job I had been putting off for too long and for his 'cheat sheet' of bandswitch BCD values.
Tom Evans for his 'Parent Board pinout' document and Jim Shorney's diagram of 'Parent Board Pin Numbering', both in the 'Files' section of the group, were / are essential reading.
Mike, G3ZCC, whose hi-res scans of the circuits were just right for printing and scribbling on.

Regards,

Mark, G4FPH.

Re: RV75 Issues: Part 3

#76009

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

Re: LED Bulb Replacement

#76008

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

LED Bulb Replacement

#76007

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

Re: RV75 Issues: Part 3

#76006

开云体育

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

Show quoted text

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

Re: RV75 Issues: Part 3

#76005

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

Re: RV75 Issues: Part 3

#76004

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

Re: RV75 Issues: Part 3

#76003

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

Re: RV75 Issues: Part 3

#76002

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

Show quoted text

On Wed, Feb 7, 2024 at 2:11?PM Rick K8EZB <frboswell@...> wrote:

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

Re: Drake UV-3 transmit offset issue

#76001

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

Re: RV75 Issues: Part 3

#76000

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

Re: RV75 Issues: Part 3

#75999

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

Re: RV75 Issues: Part 3

#75998

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

Show quoted text

On Wed, Feb 7, 2024 at 1:13?PM Rick K8EZB <frboswell@...> wrote:

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

Re: RV75 Issues: Part 3

#75997

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

Re: RV75 Issues: Part 3

#75996

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

?

Re: Drake UV-3 transmit offset issue

#75995

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

Show quoted text

-----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

Re: RV75 Issues: Part 3

#75994

开云体育

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

?

Show quoted text

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

Re: TR7 drift

#75993

Thanks for the all info Jim,

Yes, my TR7 has the fan fitted.

73, Dave