Back on the air - Finally (long)
Group,
As of today, my T4XC and R4C are reunited.
I bought them last spring, and over the months have been equipping them with Noble filters, band crystals, Shure 444,? W4 wattmeter...and RTFM.? Each had to go to Ron Baker for work beyond my skill? (patience?) level.??
Thanks to your help, I was able to repair the finals (slagged by a failed Morse key).? I replaced the 15-ohm resistors with a higher wattage;? 68-ohm resistors; parasitic suppressors and the GE 6JB6As with the same.? On the low bands, power out is 130 watts.? On 15 & 10, about 90 watts.? PO and Ip seemed to track, so little or no neutralization needed.
73 from the LA dystopia? ???????
Jay W6CJ
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Not all problems are Single-point Failures...
I figured that I'd pass this one along today, as I wind up fixing a T-4XB that had a number of problems.? It got sent to me because the owner has having trouble aligning it and got down a rabbit-hole.? It happens.?
It's a nice-looking example; cosmetically about an 8/10 with all controls having decent feel, etc.? I inspected it for charred components because the owner mentioned that he smelled smoke before boxing it up.
I couldn't find any burnt parts.? I begin testing and quickly find that I can get good output on 80 and 15, lower output on 10 and nada on 40 & 20.? I deceided that starting an alignment was the best start, as the owner said he had tried making adjustments.? Yep -- 40 & 20 had trimmers that were way off.? The best way to find these is to see if you can get the wattmeter to budge even a tiny bit.? That allowed me to get 40 & 20 back into the ballpark.?
A full alignment followed.? I could see that the finals had been replaced at least once because the Phillips screw was reinstalled on the back of the cage cover.? Checking neutralisation showed that it was off.? I did the normal tune for a dip, remove screen voltage and adjust the cap for minimum.? In this case, this gave me no joy.? I had to end up setting the neut cap by "feel".? This doesn't happen often but it happens.
Happy with plenty of power out on 160-10, I checked with a mic and had output.? Checked on CW with no key in the jack and got output.? Not thinking, I figured -- Oh, OK, CW has power (this would be okay with early T-4X's but not the B!).? Put it into my B Line station and CW isn't working right!
I find that the can cap is open.? This was the 60 uF part, as the 20 uF part was still reading 22 uF.? Replaced both with discrete caps underneath.
Go back on CW and... Still acting wonky!??
As it turned out, D9 and D12 were leaky.? In the diode test position of my Fluke 77, they tested okay on forward drop and something like 980 and 1100 on reverse,? I unsoldered one side of each and confirmed that they were leaking when reverse biased.??
It's best to partially remove that board to gain access to these diodes, which are close to the underside of the chassis.? Two lead connections to the tube and it was nicely accessible.? Replaced the diodes and everything now works.
There were two issues causing trouble with the VOX (and thus, CW).? One was the open cap and the other the two bad diodes.? Some had also replaced R94 with a 220k (should be 680k).? I will assume that someone played around and got the rig to work for a while before the parts got really bad.
Moral of the story is to try and find all problems.? If you replace a part and it still isn't working right, look for more problems!
73,
Steve Wedge, W1ES
Time flies like an arrow.? Fruit flies like a banana.
Sent with secure email.
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Might try Ron Baker, WB4HFN.
I'm in need of a vintage repair service that is familiar with Drake radio's. I have a Drake 2-NT that has lost it's output. I have changed all the tubes but no joy. Looking for recommendations.
Thanks in advance.
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I can surely fix your 2NT.
Estimate is $100 plus any shipping.
Gary
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On Jan 17, 2025, at 12:45?PM, Peter K8PT via groups.io <k8pt@...> wrote:
I'm in need of a vintage repair service that is familiar with Drake radio's. I have a Drake 2-NT that has lost it's output. I have changed all the tubes but no joy. Looking for recommendations.
Thanks in advance.
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Can you please share what you learn and what's quoted as their
hourly rate, please?
I have a TR-3 that's been giving a buddy fits (he can usually fix
almost anything).
It's been on and off his bench for 2 years and still isn't
working right.
Thanks,
David KD4E
On 1/17/25 13:45, Peter K8PT via
groups.io wrote:
toggle quoted message
Show quoted text
I'm in need of a vintage repair service that is familiar with
Drake radio's. I have a Drake 2-NT that has lost it's output. I
have changed all the tubes but no joy. Looking for
recommendations.
Thanks in advance.
|
I'm in need of a vintage repair service that is familiar with Drake radio's. I have a Drake 2-NT that has lost it's output. I have changed all the tubes but no joy. Looking for recommendations.
Thanks in advance.
|
Re: TR-4C Problems with 28.0 and 28.5 bands
Good point, Marcus, and very easy to check. ?Try swapping the two 6EA8¡¯s if you don¡¯t have a spare.
Steve Wedge, W1ES
Time flies like an arrow. Fruit flies like a banana.
On Fri, Jan 17, 2025 at 7:25 AM, Marcus PY2PLL < py2pll@...> wrote: Did you tried to tweak L2? If not yet, give a try. Despite the instructions to set it up at 29.1MHz position, after that manual recommends that the level produced at the test point near V1 should be about the same at the 3 positions. It's a negative reading on an high Z voltmeter. On 10m positions I read -0,7V (-1,1V on 15 and -1,35V on 40m). I don't know how's the "health" of this 6EA8.
73
Marcus (PY2PLL)
Em 17/01/2025 00:30, Dave KD5FX via groups.io escreveu:
I'm pretty sure they are correct, they are 42.5, 43.0 and 43.6. The last one is working OK for the 29.1 Mhz band.
73, Dave KD5FX
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Re: TR-4C Problems with 28.0 and 28.5 bands
Did you tried to tweak L2? If not yet, give
a try. Despite the instructions to set it up at 29.1MHz position,
after that manual recommends that the level produced at the test
point near V1 should be about the same at the 3 positions. It's a
negative reading on an high Z voltmeter. On 10m positions I read
-0,7V (-1,1V on 15 and -1,35V on 40m). I don't know how's the
"health" of this 6EA8.
73
Marcus (PY2PLL)
Em 17/01/2025 00:30, Dave KD5FX via
groups.io escreveu:
toggle quoted message
Show quoted text
I'm pretty sure they are correct, they are 42.5, 43.0 and
43.6. The last one is working OK for the 29.1 Mhz band.
73, Dave KD5FX
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Re: TR-4C Problems with 28.0 and 28.5 bands
Time to bake.?
Steve Wedge, W1ES
Time flies like an arrow. Fruit flies like a banana.
On Thu, Jan 16, 2025 at 22:30, Dave KD5FX via groups.io < land.dave@...> wrote:
I'm pretty sure they are correct, they are 42.5, 43.0 and 43.6. The last one is working OK for the 29.1 Mhz band.
73, Dave KD5FX
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Re: TR-4C Problems with 28.0 and 28.5 bands
I'm pretty sure they are correct, they are 42.5, 43.0 and 43.6. The last one is working OK for the 29.1 Mhz band.
73, Dave KD5FX
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Re: TR7 - Early version 2nd Mixer Schematic and Pictorial Information (description of parts on the board)
I would go with that. I did most of the updates to an older board and it seemed to work well. There is only one schematic that I am aware of and it mostly covers the later board. You can often find decent photos of the various versions by keeping an eye on eBay auctions. All of the known (so far) updates have been documented by me and VE7PS in this forum. On Thu, 16 Jan 2025 11:07:37 -0800 "Raoul Meunier via groups.io" <rmeunier@...> wrote: My other concern is T701. On the board I have there is a transformer and I am supposed to replace it with a tapped coil. As I have no info on the tapped coil, my plan is to leave the transformer untouched and try the board. -- 73 -Jim NU0C
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Re: TR-4C Problems with 28.0 and 28.5 bands
Good idea! I inspected all the tabs on the band switches this evening. I found 3 fingers that didn't look correct and fixed them. Then gave it ALL a good squirt of deoxit. Turned it on, let it warm up about 30 minutes. Still no 28.0 and 28.5 bands.
73, Dave KD5FX
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Re: MN2000 bandswitch parts and capacitor info needed
n 2025-01-16 19:14, Evan via groups.io wrote: On a number of ham radio products the "2000 watts" actually means
input power to the final amplifier (linear) Back in the day, ALL ham transmitters were specified in terms of "DC Input". Even the FCC regulations were in terms of that. So - a Novice was allowed 75W of DC input to the final stage. They changed it to power output when suitable tools became available - and FCC inspectors got tired of sticking probes into HV final compartments. Or so I'm told. - Jerry, KF6VB
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Re: MN2000 bandswitch parts and capacitor info needed
On a number of ham radio products the "2000 watts" actually means input power to the final amplifier (linear) not necessarily power input to the product.
Ed,
?
Thanks for sending the link to that Drake group discussion on the MN2000, it is very good, Jim's discussion of the capacitor bank configurationis especially helpful.?
I followed one of the links on tuner theory from that discussion and it illustrated the potential hi voltage and RF currents that may be encountered within the tuner at various impedance mismatches.? Although they were for a different tuner configuration, the voltage varied to as high as 2KV with a 2KW input.?
Since the MN2000 is rated for Full Power up to 2KW, I'm making the conservative assumption that similar conditions could be present in the MN2000 and need to spec the capacitors accordingly.
However, most of the mica caps of this case style (and proper capacitance value) that I have found thus far have had voltage ratings like 600V, but still looking.
?
Still hoping someone snapped a pic of those capacitors or maybe has a Drake part number cross ref to a mfg number.
?
Thanks
Craig KE5CHT
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Re: MN2000 bandswitch parts and capacitor info needed
Thanks Frank,
?
I will get the list of capacitor values and will measure the mounting bracket hole spacing for the caps and email you to see if you might have some of these.
Thanks
Craig KE5CHT
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Re: MN2000 bandswitch parts and capacitor info needed
Ed,
?
Thanks for sending the link to that Drake group discussion on the MN2000, it is very good, Jim's discussion of the capacitor bank configurationis especially helpful.?
I followed one of the links on tuner theory from that discussion and it illustrated the potential hi voltage and RF currents that may be encountered within the tuner at various impedance mismatches.? Although they were for a different tuner configuration, the voltage varied to as high as 2KV with a 2KW input.?
Since the MN2000 is rated for Full Power up to 2KW, I'm making the conservative assumption that similar conditions could be present in the MN2000 and need to spec the capacitors accordingly.
However, most of the mica caps of this case style (and proper capacitance value) that I have found thus far have had voltage ratings like 600V, but still looking.
?
Still hoping someone snapped a pic of those capacitors or maybe has a Drake part number cross ref to a mfg number.
?
Thanks
Craig KE5CHT
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Re: MN2000 bandswitch parts and capacitor info needed
Here is a MN-2000 manual FROM 1968 with a parts list. ?Won¡¯t help with voltage ratings for the caps. ?But kinda neat.
?
Here is a nice discussion on tuners with some links:
?
?
Click here: ? ? ?
?
ED WA6WGS
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Re: MN2000 bandswitch parts and capacitor info needed
hey Craig, ? ? ? ? ? ? ? ? ? ?Will keep eye out for "parts" condition MN-2000. Also when I was searching for a Clipperton bandswitch. Found several places that do or might do a custom bandswitch on the internet and ebay. ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?Tom W2TF
On Thursday, January 16, 2025 at 07:30:17 PM EST, Frank Barnes via groups.io <fbw4npn@...> wrote:
Craig, I have quite a few large mica caps, removed from various circuits in a discarded 10KW AM transmitter.? If you can find the values needed, I could send photos to see if these are what you might need.? Assuming you haven't found a reasonable source for new ones. Frank W4NPN
Hi Tom
?
I havent run across anything online yet about capacitor failures in the MN2000 but have read about a few bandswitch issues.?
In this one both the original bandswitch and original capacitors are all gone and replaced with poor substitutions, so not sure what problem the prev owner had or if they just did a poor shotgun approach in trying to fix it.? Everything else inside and out on this one look very nice so I really hope to get it restored.
Hopefully others on the group will give us some good insight into this.
?
Thanks
Craig KE5CHT
-- Frank Barnes
W4NPN
Chapel Hill, NC
Grid Square FM05
Cell 919.260.7955
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Re: MN2000 bandswitch parts and capacitor info needed
Craig, I have quite a few large mica caps, removed from various circuits in a discarded 10KW AM transmitter.? If you can find the values needed, I could send photos to see if these are what you might need.? Assuming you haven't found a reasonable source for new ones. Frank W4NPN
Hi Tom
?
I havent run across anything online yet about capacitor failures in the MN2000 but have read about a few bandswitch issues.?
In this one both the original bandswitch and original capacitors are all gone and replaced with poor substitutions, so not sure what problem the prev owner had or if they just did a poor shotgun approach in trying to fix it.? Everything else inside and out on this one look very nice so I really hope to get it restored.
Hopefully others on the group will give us some good insight into this.
?
Thanks
Craig KE5CHT
-- Frank Barnes
W4NPN
Chapel Hill, NC
Grid Square FM05
Cell 919.260.7955
|
Re: MN2000 bandswitch parts and capacitor info needed
Hi Tom
?
I havent run across anything online yet about capacitor failures in the MN2000 but have read about a few bandswitch issues.?
In this one both the original bandswitch and original capacitors are all gone and replaced with poor substitutions, so not sure what problem the prev owner had or if they just did a poor shotgun approach in trying to fix it.? Everything else inside and out on this one look very nice so I really hope to get it restored.
Hopefully others on the group will give us some good insight into this.
?
Thanks
Craig KE5CHT
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Jay W6CJ
DavidC KD4E
Peter K8PT
Marcus PY2PLL
Jim Shorney
