All bent out of shape (3-500z)
OK guys, have a look at this close-up pic of a 3-500z. This was found in an L7 (not mine). That's not lens distortion or an optical illusion, it really looks like that. makes noise when you pick it up and move it around. This LOOKS like brand new tube. As does its partner. 93xx date codes, paint that looks fresh and not burned. I can't figure how this got out of the factory this way but it doesn't look like shipping damage to me. The wonky tube has a yellow dot sticker on top like someone knew... Wow. The moral of this story is always give unknown tubes a good look before you power them up. I hate to think of what would have happened if I had hit this one with full HV.
--
73
-Jim
NU0C
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Does anyone have a RV7 front panel they are willing to sell?
73
Stan
KM4HQE
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Re: Drake UV-3 DEAF receiver FIXED!!
Hi Mike
Good work. Just a shorted coax, go figure. Was it the aspect of long term teflon creep that let those sharp shield wire strands work there way thru the dielectric ? Those measurements are very good. Receiver is as hot as a pistol, as good as repeater receivers measure. Looks like 5 or 6 poles total in the front end so very good for intermod for a (at the time) mobile multiband rig. Had my 2M single bander in the car when I commuted and would work 146.52 simplex along the long 80 mile commute. Rig was 35 years old then and never missed a beat. Was working a ham 60+ miles away on 146.52 simplex with me being mobile and a 5/8 wavelength mag mount on the roof. No amp, just the rigs 25 watts. I could copy him when I was crossing the Tappanzee Bridge NY and the other station was just north of Atlantic City NJ. What are you using for PL on the UV3's ?
Paul - W2NMI
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Re: Drake UV-3 DEAF receiver FIXED!!
Good on you!? Great Sleuthing! David Assaf III W5XU, VP8RXU ?
On Sat, Feb 10, 2024 at 5:11?PM Mike Bryce < prosolar@...> wrote: Paul and group¡
I have said it in the past that I¡¯m no RF engineer. However I am persistent.
It made no sense to me why the receiver should be so deaf when nothing was staring me in the face. All of the transistor voltages were just about spot on.
As Paul suggested, I too thought maybe the pin diode CR301 might be shorted or very leaky. Turns out it was fine.
What else could it be?
To paraphrase an old sleuth, Mister Sherlock Ohms;
¡°After you eliminate the impossible, whatever is left, however improbable, must be the truth.¡±
So went back to the beginning and in this case that was the input to the receiver. The input does show continuity to ground, because there is a inductor ?(L1504) connected directly to the antenna connector. I checked this before, and decided it was normal.
However when I re-visited this, I removed the inductor, easy to do by taking out a nut and screw.?
And the ground remained! The bloody input was shorted to ground. No wonder the receiver couldn¡¯t hear a thing.
To condense this rather long story down, the problem with the deaf receiver was traced down to a 2¡± piece of miniature coax that connects the T/R relay to the 140 board front end. Apparently, over time, a couple of sharp braid wires managed to punch through the teflon insulator and short out the coax, and with the antenna at DC ground, it was simply overlooked.?
The UV3 can now hear a .06 uV signal and .14 uV opens the squelch.? With .3 uV, the meter deflects a bit.
Sometimes the birds do sing.
A special call out and thanks to Paul, W2NMI, for all his help in describing how this beastie works. Paul, I owe you a beer!
Mike, WB8VGE
A man with one clock knows what time it?is. A man with two clocks is never sure.
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Re: Drake UV-3 DEAF receiver FIXED!!
Paul and group¡
I have said it in the past that I¡¯m no RF engineer. However I am persistent.
It made no sense to me why the receiver should be so deaf when nothing was staring me in the face. All of the transistor voltages were just about spot on.
As Paul suggested, I too thought maybe the pin diode CR301 might be shorted or very leaky. Turns out it was fine.
What else could it be?
To paraphrase an old sleuth, Mister Sherlock Ohms;
¡°After you eliminate the impossible, whatever is left, however improbable, must be the truth.¡±
So went back to the beginning and in this case that was the input to the receiver. The input does show continuity to ground, because there is a inductor ?(L1504) connected directly to the antenna connector. I checked this before, and decided it was normal.
However when I re-visited this, I removed the inductor, easy to do by taking out a nut and screw.?
And the ground remained! The bloody input was shorted to ground. No wonder the receiver couldn¡¯t hear a thing.
To condense this rather long story down, the problem with the deaf receiver was traced down to a 2¡± piece of miniature coax that connects the T/R relay to the 140 board front end. Apparently, over time, a couple of sharp braid wires managed to punch through the teflon insulator and short out the coax, and with the antenna at DC ground, it was simply overlooked.?
The UV3 can now hear a .06 uV signal and .14 uV opens the squelch. ?With .3 uV, the meter deflects a bit.
Sometimes the birds do sing.
A special call out and thanks to Paul, W2NMI, for all his help in describing how this beastie works. Paul, I owe you a beer!
Mike, WB8VGE
A man with one clock knows what time it?is. A man with two clocks is never sure.
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Re: Drake UV-3 DEAF receiver
Hi Mike. Looking at the IF/Discriminator/Audio board schematic, a 10.7 Mhz, 3 mv RF level (signal generator input) at the input side of the pin diode CR301 will produce 100 mVp-p at the drain side of Q300. This may be an easy, useful sanity check for confirming if the back end after the mixer is meeting spec. The first callout is somewhat unclear as these signal level callouts from Drake have been expressed as Peak to Peak. The 3 mv input level is labeled as "signal generator", thus would be Vrms. Hypothesis - could be a bad leaky pin diode (CR301, one example) or the diode not fully forward biased and attenuating signal or some other flaw in the back end ?
Paul - W2NMI
?
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Re: Drake TR-7 - A repair journey
To the group:
I made three corrections to the TR-7 Parent Board pinout docs and posted the updated Excel file and PDF file to the files section here:
The older version of the files have been deleted to conserve space.
Thanks again to Jim Shorney for catching the errors.
73, Tom, AG9X
On Thu, Feb 8, 2024 at 3:33?PM Jim Shorney < jimNU0C@...> wrote:
I can relate to that Tom. It does seem that no matter how many times I proof something I still miss things too often. I hope if anyone spots any errors in my stuff they will let me know. Thanks for all that you do.
73
-Jim
NU0C
On Thu, 8 Feb 2024 15:20:48 -0600
"Tom Evans" <Tom.AG9X@...> wrote:
> Thanks for catching the errors in the parent board pinout doc.? No matter
> how many times a person rechecks something, a different pair of eyes can
> spot unseen errors.
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Re: Drake UV-3 DEAF receiver
Hi Mike. This case is measuring well past scope's 3 db point. Expected then the scope would report a lower value than actual in this case. Simple way then is to compare the output at T800 (transmitter RF in) at 2.8 Vp-p to the receiver mixer LO input value of 4.0 Vp-p. The transmit level looks to be nearly correct given the transmitter power, so can then use that value of drive as a baseline to determine if the LO injection at the mixer is reasonable. If Q813 is suspect, need to look at the drain side and see if the scope can display the clipping of the LO drive.?
Paul - W2NMI
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Re: Drake UV-3 DEAF receiver
Hi Paul and the gang.
I think I may have done a serious measurement error! While this didn¡¯t fix the problem with the deaf receiver, it has laid down a different avenue for me to take.
I measured 210mv at the source of Q813. That¡¯s not even close to the 4.00 V pp as per the schematic.
However this morning, it dawned on me that I had the scope¡¯s probe in the 10X position so it won¡¯t load down the circuit. So my 210mV should be 2.10Vpp.
That however is only half the required signal level.
So I¡¯m back to square one, and the lack of LO signal to the mixer.
Mike Bryce wb8vge
"The eye is always caught?by the light, but shadows?have more to say"
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On Feb 9, 2024, at 11:50 PM, Paul Dulaff via < pdulaff@...> wrote:
Hi Mike. So looking at the transmit power out of 18 watts vs the spec of 25 watts the rig is only slightly down in transmit power. Assuming the small drop is all drive from the VCO board, this is -1.43 db down. Using this, the output voltage at T800, instead of being 2.8 Vp-p, this voltage is 2.4 V p-p. Knowing this and using the scope, this voltage being measured with a scope with rolloff, can be used to gage the scope response at 146 Mhz and a tool to check the injection level at the mixer.
The receiver should be closer to 0.3 uV sensitivity than the measured 3 uV. So the receiver looks down at least 20 db as compared to the transmitter at 1.43 db. Seems then this issue would be Q811, Q813 section where the bigger issue exists. Now, mixers aren't linear devices so this is an imperfect comparison. The 4 Vp-p signal at the source of Q813 is substantially all local oscillator signal. Assume 20db gain at the RF Amp and we have 30 uV at the gate of Q813 with 3 uV input. Looking at the drain side of Q813 with the scope, you should see a clipped version of the local oscillator signal with gain. The Q813 device to be good mixer needs to be driven into saturation so that LO signal at the drain side (mixer output) should look like a hard clipped version of the sinusoidal signal at the source. The signal at the drain will be lower level as compared to the source as the IF input tank circuit C840/L801 is tuned to 10.7 Mhz with the LO at something like 135 Mhz. If little or no clipping exists, then low drive or Q813 JFET source or Q813 has issues as can be evidenced by no hard clipping of the LO signal at the drain.
Paul - W2NMI
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Does anyone have the adjustment/ alignment procedures for the Drake MN4?? Repaired the meter, but the readings are incorrect.
many thanks.
David Assaf III W5XU, VP8RXU ?
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Re: Another TR7 Journey begins
On Sat, 10 Feb 2024 06:55:52 -0800 "Bill NZ0T" <nz0tham@...> wrote: Got the PS working and it was mostly pilot error.? The previous owner had replaced the Jones connector on the DC cord with Molex connectors for whatever reason and had put PowerPoles on the Jones connector.. The devil is in the details... :D So that leaves the very low sidetone volume, no forward/reflected power on the meter and the wonky ALC to fix before I put the rig on the air.? I'm wondering if the ALC pot on the ALC board migt be dirty or bad.? I may try a shot of DeOxit to see if that helps.
Any suggestions are greatly appreciated! Again, do not use DeOxit on pots. Use a cleaner that is designed specifically for pots, like Faderlube. Or just clean the entire ALC board with alcohol. Drake liked high impedance circuits and crud accumulation on boards can sometimes throw things off. -- 73 -Jim NU0C
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Re: Another TR7 Journey begins
Got the PS working and it was mostly pilot error.? The previous owner had replaced the Jones connector on the DC cord with Molex connectors for whatever reason and had put PowerPoles on the Jones connector..? And for whatever reason I was thinking he had somwhow added that line so I only had to use the other connector for everything.? I finally actually looked at the photo of the PS in the owners manual I downloaded and realized that BOTH cables had to be connected - DUH!? So I cut off the Molex conectors, replaced them with the orginal Jones connector, plugged both into the rig and guess what - it worked!
So that leaves the very low sidetone volume, no forward/reflected power on the meter and the wonky ALC to fix before I put the rig on the air.? I'm wondering if the ALC pot on the ALC board migt be dirty or bad.? I may try a shot of DeOxit to see if that helps.
Any suggestions are greatly appreciated!
73, Bill NZ0T
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Re: Added photo album Drake R-4C T-4XC and MS-4 Powersupply
#photo-notice
Dwight,
You didn¡¯t give info on who is selling, seller¡¯s contact info, and price. ?When you have a moment please post that information. ? 73, Bill KJ5BNE ++++++++++++++++ Bill Blodgett Arlington, Texas
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On Feb 9, 2024, at 11:47?PM, Group Notification <[email protected]> wrote:
?
dwight_talley <dwight_talley@...> added the photo album
Drake R-4C T-4XC and MS-4 Powersupply
: For sale are a complete set of Drake Receiver, Transmitter and Supply /Speaker
From the estate of a Ham. The receiver is very sensitive and sounds good. I am unable to test the transmitter but it does powerup without issue.
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Added photo album Drake R-4C T-4XC and MS-4 Powersupply
#photo-notice
dwight_talley <dwight_talley@...> added the photo album
Drake R-4C T-4XC and MS-4 Powersupply
: For sale are a complete set of Drake Receiver, Transmitter and Supply /Speaker
From the estate of a Ham. The receiver is very sensitive and sounds good. I am unable to test the transmitter but it does powerup without issue.
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Re: Drake UV-3 DEAF receiver
Hi Mike. So looking at the transmit power out of 18 watts vs the spec of 25 watts the rig is only slightly down in transmit power. Assuming the small drop is all drive from the VCO board, this is -1.43 db down. Using this, the output voltage at T800, instead of being 2.8 Vp-p, this voltage is 2.4 V p-p. Knowing this and using the scope, this voltage being measured with a scope with rolloff, can be used to gage the scope response at 146 Mhz and a tool to check the injection level at the mixer.
The receiver should be closer to 0.3 uV sensitivity than the measured 3 uV. So the receiver looks down at least 20 db as compared to the transmitter at 1.43 db. Seems then this issue would be Q811, Q813 section where the bigger issue exists. Now, mixers aren't linear devices so this is an imperfect comparison. The 4 Vp-p signal at the source of Q813 is substantially all local oscillator signal. Assume 20db gain at the RF Amp and we have 30 uV at the gate of Q813 with 3 uV input. Looking at the drain side of Q813 with the scope, you should see a clipped version of the local oscillator signal with gain. The Q813 device to be good mixer needs to be driven into saturation so that LO signal at the drain side (mixer output) should look like a hard clipped version of the sinusoidal signal at the source. The signal at the drain will be lower level as compared to the source as the IF input tank circuit C840/L801 is tuned to 10.7 Mhz with the LO at something like 135 Mhz. If little or no clipping exists, then low drive or Q813 JFET source or Q813 has issues as can be evidenced by no hard clipping of the LO signal at the drain.
Paul - W2NMI
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Re: Drake UV-3 DEAF receiver
Spent all day on this project, Here what I have accomplished¡
replaced the FET with a second one¡ª I¡¯m getting fairly good at taking the 2m rec/vco boards apart.
No joy¡.
I decided that the problem does not appear to be a faulty front end RF amplifier, so I started to dig a bit further back. And that brings me to the mixer. According to the manual, I should have 4 V at 133.3 mHz at the source of the mixer.
I don¡¯t!
I have millivolts instead.
Now my scope runs out of snot at 100 mHz, so maybe a measuring issue, but still millivolts is not volts. It¡¯s not clear to me if the voltage on the source of Q813 is the total of the incoming signal plus the buffer amp or strictly from the buffer amp?
The transistor voltage are good, except for Q810, the VCO buffer, they were off a bit, ?So, I popped in a device stolen from my part pig. No joy.
Back to the buffer/amp. Both L809 and L810 tune, but they are very broad. ?L804 is used to adjust the VCO and everything went as it should. The receiver is locked as well as the transmitter. I get a good 18 W output into 50¦¸.
After hours and hours of tinkering with this thing, I have managed to get the receiver to hear a 3uV signal. That¡¯s hear, and I mean weakly¡To quiet the receiver, it takes lots of signal. Something is still amuck with the receiver.
So, right now, it looks like I don¡¯t have enough drive coming out of Q808 (yet the transmitter works at full power) and for the life of me, I can¡¯t find the fault
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On Feb 9, 2024, at 4:30 PM, Paul Dulaff via < pdulaff@...> wrote:
Hi Mike. So lets consider the RF Amp as working at the moment and something perhaps in the mixer is the issue. If not already done, check the DC voltages on Q813 and the LO injection levels. The injection level as shown on the schematic is easy to check with a scope. The LO should also be showing up at the drain side (output) of the mixer. Try injecting a 2M signal at the gate of the JFET mixer and compare to what you get at G1 of the RF Amp. To further test the RF Amp device, short G2 to ground. The current thru that dual gate device should drop and you should see nil voltage drop across R842 (68 ohms). This should shut down the RF Amp such that the signal will drop I would think at least 10 to 15 db yet further from where it is now. Paul - W2NMI
_._,_._,_
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Re: Another TR7 Journey begins
Hi Bill, On Fri, 09 Feb 2024 14:47:22 -0800 "Bill NZ0T" <nz0tham@...> wrote: R-1613 on the ALC board is very sensitive and adjusts from? almost 0 watts to 165 watts in a very short span.? The ALC light seems to go between staying on all the time no matter where the carrier level is set or not coming on at all.? Adjustment of R-2227 on the Predriver board seems to have no effect at all. The power meter calibration also won't worl.? Adjusting R-2001 and R-2002 has no effect at all.? Maybe that and the ALC problem are related?? The sidetone volume is still very low, haven't looked into that yet. This is a puzzler. Check with a frequency counter or spectrum analyzer to see if your power is coming out where it is supposed to be. If it is, you may have a band switch, low pass filter, or T/R relay issue. ALC is derived from the wattmeter circuit so you should see something on the meter if you have power. Don't overlook the pushbuttons. Schadow switches are known to become cranky if not used for a long time. Messed with the PS7 a bit, it seems to be working fine with 13.6 volts measured inside it.? But when I plug in the Jones connector and turn on the rig the fans on the rig and PS come on (they are the original AC fans) but the rig doesn't power up. The DC power connection is shown on the parent board schematic but doesn't make much sense. Not hard to figure out though. Two of the pins are tied together as ground. Of the other two, one supplies hard power to the PA deck and the other powers the rest of the radio through the power switch. There are two sets of contacts on the power switch, one for the 120V mains and the other for the 13.6 DC. In good news the filter board is filled with the standard 2.3 filter, 1.8 SSB filter, 6.0 AM filter and 300 Hz CW filter!? And they all work just fine. Good filter complement. Very flexible. -- 73 -Jim NU0C
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Re: Another TR7 Journey begins
A lot of progress today. Got the knobs and front panel all cleaned up and put back on.? Gonna need to find some of the blue filter plastic for the VFO and meter lights but no hurry on that.? I took all the boards out and carefully cleaned the conenctions even tho they all looked relly clean.? This included taking the display board out which was a bit of a tussle but I managed to get it out, clean things up, and get it back in.? Still works too!
I managed to get the S-meter calibrated and it seems to be pretty accurate now.? Also got the mode frequency adjustments done in good shape. But the ALC adjustment did no go well.? R-1613 on the ALC board is very sensitive and adjusts from? almost 0 watts to 165 watts in a very short span.? The ALC light seems to go between staying on all the time no matter where the carrier level is set or not coming on at all.? Adjustment of R-2227 on the Predriver board seems to have no effect at all. The power meter calibration also won't worl.? Adjusting R-2001 and R-2002 has no effect at all.? Maybe that and the ALC problem are related?? The sidetone volume is still very low, haven't looked into that yet.
Messed with the PS7 a bit, it seems to be working fine with 13.6 volts measured inside it.? But when I plug in the Jones connector and turn on the rig the fans on the rig and PS come on (they are the original AC fans) but the rig doesn't power up.? I ran out of time so haven't opened up the Jones connector yet to look at it.? I haven't been able to find a pinout for the PS7 connector, anyone have that?
In good news the filter board is filled with the standard 2.3 filter, 1.8 SSB filter, 6.0 AM filter and 300 Hz CW filter!? And they all work just fine.
73, Bill NZ0T
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Re: Drake UV-3 DEAF receiver
Just remembered - it's DigiKey ...
On 2/9/24 13:16, DavidC KD4E wrote:
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I forget which one - but one of the parts suppliers has always
given
free shipping to those who pay via check - no minimum order.
On 2/9/24 13:02, Paul Dulaff via
groups.io wrote:
Hi Mike. RF Parts lists the MFE521 in their Misc parts listing.
Price $5.95 ea. BUT, minimum order is $25.00 from them. Checked
Mouser and no listing whatsoever. I agree with you on the Asian
clone parts being questionable, certainly at analog VHF. While
leaded is going away, some of these parts can be found in
surface mount and if a 1206 size can be worked with, no luck in
this case so far.
Hope this helps.
Paul - W2NMI
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Re: Drake UV-3 DEAF receiver
Hi Mike. So lets consider the RF Amp as working at the moment and something perhaps in the mixer is the issue. If not already done, check the DC voltages on Q813 and the LO injection levels. The injection level as shown on the schematic is easy to check with a scope. The LO should also be showing up at the drain side (output) of the mixer. Try injecting a 2M signal at the gate of the JFET mixer and compare to what you get at G1 of the RF Amp.
To further test the RF Amp device, short G2 to ground. The current thru that dual gate device should drop and you should see nil voltage drop across R842 (68 ohms). This should shut down the RF Amp such that the signal will drop I would think at least 10 to 15 db yet further from where it is now.
Paul - W2NMI
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Jim Shorney
David
DavidC KD4E