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— 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 50Ω.
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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Re: Drake UV-3 DEAF receiver
笔补耻濒….
I took the MFE521 out of the deaf receiver and put in one from the part pig UV3. No joy!
Still deaf..
Now, the voltages on the four pins of the 521 are right dead on the nose. Now that being said, if I inject a 146.000 mHz signal into the antenna port, it takes 10uV for the receiver to just barely hear the signal
However!!! If I take the signal and inject it one of the pins of the 521, there is no difference. It’s like the 521 isn’t providing any gain what so ever.?
Is it possible that the voltages could be correct and still have a popped FET?
The two coils between the antenna and the 521 do peak, as well as the other four coils in the passband filter.?
73
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On Feb 9, 2024, at 1:02 PM, Paul Dulaff via < pdulaff@...> 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
I forget which one - but one of the parts suppliers has always
given
free shipping to those who pay via check or MO - no minimum
order.
On 2/9/24 13:02, Paul Dulaff via
groups.io wrote:
toggle quoted message
Show quoted text
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. 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 TR-7 - A repair journey
Hi, Mark….
As Jim, NU0C mentioned, I do have the power supply/osc board for the TR7 along with the extension boards for the TOP cards. I’m working on the set for the bottom cards.?
This is not the place to discuss prices and such, so pop me a note at : heathkitshop at me dot com
Here are some photos of the boards
I’m mike, wb8vge? The heathkit shop
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On 
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Re: Drake UV-3 DEAF receiver
Everyone, the struggle continues.
I have reduced the stack of non working UV3s down to three.
One of the UV3s is a two meter only model. It’s kinda deaf in that it takes 10uV of signal for it to hear.
It transmits just fine, so my logic is that the VCO, the divider, the IF amp/audio are all working correctly. I did swap out all the plug in boards with known working cards and no joy. Still deaf as a stone.
The way Drake designed the 2 meter boards makes it extremely difficult to remove and or test them. But since this one only has the one 2 meter module, it might not be as hard as I think it may. Right now, I’m thinking simple, and that simple is the front end amplifier Q812 is no longer with us. It’s a MFE521 MOSFET. Looks like eBay might be the only source for this part and most likely will be a Chinese counterfeit part. Who knows what you get from eBay anymore.
Of course, I’m up for suggestions
Mike WB8VGE
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Re: Drake TR-7 - A repair journey
Hi Mark, On Fri, 09 Feb 2024 01:59:48 -0800 "atlasstuff" <g4fph@...> wrote: The Heathkit Shop used to make a nice-looking, replacement power supply board for the TR-7, but not sure whether they still do. Mike is a member of this group. I am sure he will respond. I recall mailing the owner a few years ago and he was not willing to ship to the UK because of all the trading complications resulting from the UK leaving the EU. I see there's a potential alternative here: but not sure whether these are in production and for sale yet. Mine does not have any ball and leaf spring. I may be mis-remembering that it has a ball, but the detent is at the rear panel. I do have another TR-7 - a very nice, late model, made just prior to when Drake started producing the TR-7A. Plus / minus some minor connector oxidation issues, that one has always worked well. Problem is, when stuff just works, there's little incentive to learn much about what goes on inside. Fixing up this 'basket case' TR-7 has forced me to understand the design, which will be good for maintaining the 'fleet' in future. Having needed to get to the LPF and HPF areas of the radio, I now understand why Drake decided to split the rear panel in the later models! You are behind the curve. I have three. :) Along with two R7 receivers. Only one of my TR7s has the slit panel. I wish they had done that from the start. My #1 has some band switch issues from years of use so I am currently running on one of the spares. Sadly, the one with the split panel has the fewest options... -- 73 -Jim NU0C
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Re: Drake UV-3 transmit offset issue —SOLVED
Everyone!
I have the last two offset boards for the UV3 repaired.
Basically, the 4081 ICs were bad. On one board, all three had a bad section that turned on the wrong offset.
Frankly, I’m still not sure how that offset board works.
For now, I have four working offset boards
I’ll start another thread about the receiver being deaf as a post.
I’m Mike, WB8VGE 
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If you can’t find them all, let me know what you are missing and I’ll check my extensive stock of TTL and CMOS IC’s.? I have thousands if IC’s, not all the numbers,
of course, but some that are now extinct!
?
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From: [email protected] <[email protected]>
On Behalf Of Rick K8EZB via groups.io
Sent: Friday, 9 February 2024 08:43
To: [email protected]
Subject: Re: [DRAKE-RADIO] RV75 Issues: Part 3
?
You’ll get it going.
Clint,
Thanks for your vote of confidence! Right now I am much less confident than you are on this topic.
Just ordered some replacement semiconductors and waiting for these to arrive. I have checked on the availability of most RV75 semiconductors/integrated circuits and have found these still available, mostly from Mouser or DigiKey, some NOS from eBay, and at
prices often less than $1 each.?
WTB:?
RF & Analog board (complete and working preferred but for parts OK)
VCXO xtal (15.5 MHz)
Rick
K8EZB
?
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You’ll get it going.
Clint, Thanks for your vote of confidence! Right now I am much less confident than you are on this topic. Just ordered some replacement semiconductors and waiting for these to arrive. I have checked on the availability of most RV75 semiconductors/integrated circuits and have found these still available, mostly from Mouser or DigiKey, some NOS from eBay, and at prices often less than $1 each.? WTB:? RF & Analog board (complete and working preferred but for parts OK) VCXO xtal (15.5 MHz) Rick K8EZB
?
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Hi Rick,
?
You’ll get it going.? At the end of it, you’ll know the RV-75 really well!
?
73,
Clint, VE3CMQ
?
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From: [email protected] <[email protected]>
On Behalf Of Rick K8EZB via groups.io
Sent: Thursday, 8 February 2024 11:05
To: [email protected]
Subject: Re: [DRAKE-RADIO] RV75 Issues: Part 3
?
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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Re: Another TR7 Journey begins
Thanks all for the tips, I got all the knobs off last night for cleaning.? Also gently pried the clear horizontal plastic covering the meter out of it's grooves because it is dirty on the inside.? I'll get those cleaned today.? Will also steal a coat hanger from one of the closets and make the board puller.
The inside of the rig is amazingly clean considering how filthy the exterior was lol.
73, Bill NZ0T
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Re: Drake TR-7 - A repair journey
Jim,
Thanks for the pointer regarding that electrolytic capacitor on the power supply board. No, I did not change it when I had the board out. I will make a note for the future, but will not disturb the board again until I have the transmitter-side working. The Heathkit Shop used to make a nice-looking, replacement power supply board for the TR-7, but not sure whether they still do. I recall mailing the owner a few years ago and he was not willing to ship to the UK because of all the trading complications resulting from the UK leaving the EU. I see there's a potential alternative here: but not sure whether these are in production and for sale yet.
"The band switch detent is pretty light on these. Is is the ball and leaf spring at the rear. The stiff wire attached to the the bulkhead between sections is a ground point for the shaft." Mine does not have any ball and leaf spring. Probably fell on the floor of a previous OM's shack, along with some of the screws:-( If you or anyone has a picture and/or any dimensions of how things should be, I would be grateful. Otherwise, I will figure it out.
I do have another TR-7 - a very nice, late model, made just prior to when Drake started producing the TR-7A. Plus / minus some minor connector oxidation issues, that one has always worked well. Problem is, when stuff just works, there's little incentive to learn much about what goes on inside. Fixing up this 'basket case' TR-7 has forced me to understand the design, which will be good for maintaining the 'fleet' in future. Having needed to get to the LPF and HPF areas of the radio, I now understand why Drake decided to split the rear panel in the later models!
Regards,
Mark, G4FPH.
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Re: Another TR7 Journey begins
Sorry but I have to disagree in part with this. DeOxit is not appropriate for pots and there have been tales of it ruining the carbon track. It does not happen to everyone, but why chance it? Caig has a tool for pots called FaderLube. 73 -Jim NU0C On Fri, 9 Feb 2024 03:43:26 +0000 (UTC) "Evan via groups.io" <k9sqg@...> wrote: Sparingly applying DeOxit to switches and pots is a good idea too.
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Jim Shorney
DavidC KD4E