Re: Looking for L75 amp meter replacement.
Have progress to share here.
Received the meter I bought from eBay.
Perfect fit as it was an 83T as the original.
The last one available. It was a 0-300 DC Amp. meter.
Came with an external resistor which I removed but guess what?
The original meter used by Drake for the L75 was 200 uA full scale.
The one received was 1 mA full scale. Tested it with a small circuit I put together and one amperimeter.
Opened it and couldn't find any internal resistor or anything like that inside the transparent meter.
Saw also a few improvements on the movement when compared with the original used on the Drake L75.
Looks like they corrected the issues that made the 83T model, fail on Drakes.
To make things brief...? the internal wire used on the internal meter coil was different than the one used for the 200 uA version.
As expected, all readings were pretty low, when installed it in the L75..
At the end of the day, I had to re-calculate all the meter section resistor network.
After installing the new resistors, went through the meter calibration process shown in the manual.
Have finished replacing all the resistors and now I have a fully functional meter that is a joy to see it working.
Previously, I was adjusting the Amp only by using an external Wattmeter. Actually, the Wattmeter is an Drake MN-2700.
Now, I can read Plate Voltage, Plate and Grid current and it matches what the manual says.
The Relative Output also matches perfectly.
Have written down on my notes the new values installed in case the XYL sells the Amp in the future LOL.
Anyway, wanted to share with you my experience.
Thank you all who helped me finding a solution to my Drake L75 problem.
Learnt a lot in the process.
73
Rob
YS1RS
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On Tue, Feb 6, 2024 at 11:26 AM, Jim Shorney wrote:
For slow drift I would suspect a problem with one of the voltage regulators or maybe the master crystal oscillator.
After further review (of the ckt diag and ToO section of the manual, my first guess is voltage regulation of the VCO or VCXO.Basically eveything works, just some slight drift. I'll change over from soldering iron to scope, VOM, and counter and see what I can find. BTW: I emailed Ron, WB4HFM, to see if he could suggest things to look for or perhaps take a look himself and he replied he no longer works on RV75's. So it looks like I am on my own, but with a distant but able assist from the assembled multitude here! Rick K8EZB
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Thanks Tom.
I chose to log in with google.?
73' Sjaak PA3GHL.
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It is starting to sound like this unit suffered from some sort of high voltage event on the control lines. For slow drift I would suspect a problem with one of the voltage regulators or maybe the master crystal oscillator. Rapid drift and no knob control might mean the PLL is unlocked. Don't overlook connector issues. I recently worked on an old Yaesu rig that (among other problems) had an issue where the clarifier (RIT) moved the frequency in what seemed to be a capacitor charge curve rather than following the control as you turned it. The culprit turned out to be corrosion in the VFO connector. Maybe check the RIT switch and associated circuits. And the other switches as well. Mine seem to have a little crud in them as they don't always make on the first push. Someday I will clean them... 73 -Jim NU0C On Tue, 06 Feb 2024 09:03:47 -0800 "Rick K8EZB" <frboswell@...> wrote: Summary: solid progress but more work to do
Details:
? Replaced all electrolytics with new
? Replaced burned resistor R218 150 ohm in ENABLE line
? Replaced damaged axial lead ceramic capacitor C250 .01 mfd bypass +13v to gnd with .01 mfd disc ceramic
Results:
? On power up appeared to work very briefly, then original axial lead ceramic capacitor C251 .01 mfd bypass +13v to gnd began smoking vigorously
? Powered down and replaced C251 with .01 disc ceramic
? Powered up and no new smoke.
? Now works as a VFO as one might expect except that freq does not lock; drifts lower very slowly
Notes:
? I am guessing that the passage of time may have resulted in degradation of the original ceramic bypass capacitors voltage rating.
? Will now go through the manual setup and troubleshooting procedures to identify the failure to lock.
Rick
K8EZB
-- 73 -Jim NU0C
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Thanks Steve.? I have to repair the T4B first. I miss a few tubes and have to clean it and then testing.
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Op 6 feb. 2024, om 17:08 heeft Steve Wedge, W1ES/4 via < w1es@...> het volgende geschreven:
Use all the cables except for PTO LAMP and CAR OSC. put a shorting plug in the R-4C PTO LAMP jack. Do the transceive alignment per the T-4B/T-4XB but use the trimmer that is used for the carrier oscillator in the R-4C (can¡¯t remember its designator at the moment).?
If you want to do AM, you may need to tweak that trimmer.?
73,
Steve Wedge, W1ES/4
Time flies like an arrow. Fruit flies like a banana.
On Tue, Feb 6, 2024 at 10:48, Sjaak van Meurs < Sjaakvanmeurs1@...> wrote: Hello members,
Ik have a Drake T4B and I like to use it with a Drake R4C, how can I connect these at best?
73¡¯ Sjaak, PA3GHL.
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Yeah, that is really strange. Maybe it wasn't really a cap? 73 -Jim NU0C On Tue, 6 Feb 2024 13:24:49 -0500 "John K5MO" <johnk5mo@...> wrote: Good progress! I'm not used to hearing ceramic caps fail. I wonder if
they're subject to metal migration over time as other caps can be. To
shunt enough current to create smoke, it formed a pretty stout short, and
not just a small dendrite.
Thank you for taking the time to document this for us to share in.
John K5MO
On Tue, Feb 6, 2024 at 12:03?PM Rick K8EZB <frboswell@...> wrote:
Summary: solid progress but more work to do
Details:
? Replaced all electrolytics with new
? Replaced burned resistor R218 150 ohm in ENABLE line
? Replaced damaged axial lead ceramic capacitor C250 .01 mfd bypass +13v
to gnd with .01 mfd disc ceramic
Results:
? On power up appeared to work very briefly, then original axial lead
ceramic capacitor C251 .01 mfd bypass +13v to gnd began smoking vigorously
? Powered down and replaced C251 with .01 disc ceramic
? Powered up and no new smoke.
? Now works as a VFO as one might expect except that freq does not lock;
drifts lower very slowly
Notes:
? I am guessing that the passage of time may have resulted in
degradation of the original ceramic bypass capacitors voltage rating.
? Will now go through the manual setup and troubleshooting procedures to
identify the failure to lock.
Rick
K8EZB
-- 73 -Jim NU0C
|
Good progress!?? I'm not used to hearing ceramic caps fail.?? I wonder if they're subject to metal migration over time as other caps can be.? To shunt enough current to create smoke, it formed a pretty stout short, and not just a small dendrite.
Thank you for taking the time to document this for us to share in.
John K5MO
On Tue, Feb 6, 2024 at 12:03?PM Rick K8EZB < frboswell@...> wrote: Summary: solid progress but more work to do
Details:
?? Replaced all electrolytics with new
?? Replaced burned resistor R218 150 ohm in ENABLE line
?? Replaced damaged axial lead ceramic capacitor C250 .01 mfd bypass +13v to gnd with .01 mfd disc ceramic
Results:
?? On power up appeared to work very briefly, then original axial lead ceramic capacitor C251 .01 mfd bypass +13v to gnd began smoking vigorously
?? Powered down and replaced C251 with .01 disc ceramic
?? Powered up and no new smoke.
?? Now works as a VFO as one might expect except that freq does not lock; drifts lower very slowly
Notes:
?? I am guessing that the passage of time may have resulted in degradation of the original ceramic bypass capacitors voltage rating.
?? Will now go through the manual setup and troubleshooting procedures to identify the failure to lock.
Rick
K8EZB
?
|
Sjaak,
To reset your Groups.io password:
1. Go to?
2. Enter your email address.
3. Click the link below the password field.
73, Tom AG9X
How can I make a new one, or what can I do the best?
PA3GHL, Sjaak.
|
Summary: solid progress but more work to do
Details:
?? Replaced all electrolytics with new
?? Replaced burned resistor R218 150 ohm in ENABLE line
?? Replaced damaged axial lead ceramic capacitor C250 .01 mfd bypass +13v to gnd with .01 mfd disc ceramic
Results:
?? On power up appeared to work very briefly, then original axial lead ceramic capacitor C251 .01 mfd bypass +13v to gnd began smoking vigorously
?? Powered down and replaced C251 with .01 disc ceramic
?? Powered up and no new smoke.
?? Now works as a VFO as one might expect except that freq does not lock; drifts lower very slowly
Notes:
?? I am guessing that the passage of time may have resulted in degradation of the original ceramic bypass capacitors voltage rating.
?? Will now go through the manual setup and troubleshooting procedures to identify the failure to lock.
Rick
K8EZB
?
|
How can I make a new one, or what can I do the best?
PA3GHL, Sjaak.
|
Use all the cables except for PTO LAMP and CAR OSC. put a shorting plug in the R-4C PTO LAMP jack. Do the transceive alignment per the T-4B/T-4XB but use the trimmer that is used for the carrier oscillator in the R-4C (can¡¯t remember its designator at the moment).?
If you want to do AM, you may need to tweak that trimmer.?
73,
Steve Wedge, W1ES/4
Time flies like an arrow. Fruit flies like a banana.
On Tue, Feb 6, 2024 at 10:48, Sjaak van Meurs < Sjaakvanmeurs1@...> wrote: Hello members,
Ik have a Drake T4B and I like to use it with a Drake R4C, how can I connect these at best?
73¡¯ Sjaak, PA3GHL.
|
Hello members,
Ik have a Drake T4B and I like to use it with a Drake R4C, how can I connect these at best?
73¡¯ Sjaak, PA3GHL.
|
Re: Searching for AUX-7 boards¡
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Re: Copy of original documents
Please email a copy of the cards and QC tag date and Ron, WB4HFN can add those to his serial number database on his site.?
Email:??wb4hfn@...?
Thanks,
Mark, WB0IQK
|
Hello all,
On the net Sunday afternoon I checked in with my work in progress TR-3.
Someone commented on my audio being a bit off but I did not get the call.
Who was that?
Can someone point me to just what is wrong and what to look at please?
Dave KC3AM
|
Re: Searching for AUX-7 boards¡
HA!? I DID.? tHANKS FOR THE CORRECTION.? Sorry. David Assaf III W5XU, VP8RXU ?
On Mon, Feb 5, 2024 at 9:37?PM Stan Gammons via <buttercup11421= [email protected]> wrote:
I think David made a typo.
Go here
The board you are looking for is this one.? According to the price
list, the board is $6 plus shipping.
|
QST Jul82
|
WARC AND LF ON THE TR-7
|
If you are an ARRL member, you can search the archives and
download the July 82 QST article.?
73
Stan
KM4HQE
On 2/5/24 21:11, Joseph K4JNG wrote:
I am
unable to find anything related to ¡°Drake Aux-7¡± on
.
?
?
joseph
n. graif
k4jng
?
?
The aux 7 from
Fair Radio is the way to go..? the rest of parts you can
get from Mouser or other supply houses.i have used about
10 of these with no issues.
David Assaf
III
W5XU??? VP8RXU
?
On Sat, Feb 3,
2024, 10:49 AM Jim Shorney <jimNU0C@...>
wrote:
You will pay a premium price for a genuine AUX-7. A
workable substitute that gives you WARC and VLF coverage
is what I call the "FAUX-7" board available from Far
Circuits. It is a reproduction of a diode matrix AUX-7
replacement published in QST July 1982. You buy the bare
board from them and you supply the diodes and connectors.
There is also an article I think on on building your
own AUX-7 board. Neither of these includes the provision
for a fixed frequency crystal, but in all my travels I
have only seen almost one person who used this.
73
-Jim
NU0C
On Sat, 03 Feb 2024 01:38:55 -0800
"Joseph K4JNG" <jgraif1@...>
wrote:
> I am in the hunt for two AUX-7 boards, for my TR7 and
R7. Please help if you are able¡
>
> Best 73,
> joe
> K4JNG
|
Re: Searching for AUX-7 boards¡
I think David made a typo.
Go here
The board you are looking for is this one.? According to the price
list, the board is $6 plus shipping.
|
QST Jul82
|
WARC AND LF ON THE TR-7
|
If you are an ARRL member, you can search the archives and
download the July 82 QST article.?
73
Stan
KM4HQE
On 2/5/24 21:11, Joseph K4JNG wrote:
toggle quoted message
Show quoted text
I am
unable to find anything related to ¡°Drake Aux-7¡± on
fairradio.com .
?
?
joseph
n. graif
k4jng
?
?
The aux 7 from
Fair Radio is the way to go..? the rest of parts you can
get from Mouser or other supply houses.i have used about
10 of these with no issues.
David Assaf
III
W5XU??? VP8RXU
?
On Sat, Feb 3,
2024, 10:49 AM Jim Shorney <jimNU0C@...>
wrote:
You will pay a premium price for a genuine AUX-7. A
workable substitute that gives you WARC and VLF coverage
is what I call the "FAUX-7" board available from Far
Circuits. It is a reproduction of a diode matrix AUX-7
replacement published in QST July 1982. You buy the bare
board from them and you supply the diodes and connectors.
There is also an article I think on on building your
own AUX-7 board. Neither of these includes the provision
for a fixed frequency crystal, but in all my travels I
have only seen almost one person who used this.
73
-Jim
NU0C
On Sat, 03 Feb 2024 01:38:55 -0800
"Joseph K4JNG" <jgraif1@...>
wrote:
> I am in the hunt for two AUX-7 boards, for my TR7 and
R7. Please help if you are able¡
>
> Best 73,
> joe
> K4JNG
|
Re: Searching for AUX-7 boards¡
I am unable to find anything related to ¡°Drake Aux-7¡± on fairradio.com . ? ? joseph n. graif k4jng ?
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From: [email protected] < [email protected]> On Behalf Of David Sent: Saturday, February 3, 2024 11:55 AM To: [email protected]Subject: Re: [DRAKE-RADIO] Searching for AUX-7 boards¡ ? The aux 7 from Fair Radio is the way to go..? the rest of parts you can get from Mouser or other supply houses.i have used about 10 of these with no issues. David Assaf III
W5XU??? VP8RXU ? On Sat, Feb 3, 2024, 10:49 AM Jim Shorney <jimNU0C@...> wrote:
You will pay a premium price for a genuine AUX-7. A workable substitute that gives you WARC and VLF coverage is what I call the "FAUX-7" board available from Far Circuits. It is a reproduction of a diode matrix AUX-7 replacement published in QST July 1982. You buy the bare board from them and you supply the diodes and connectors. There is also an article I think on on building your own AUX-7 board. Neither of these includes the provision for a fixed frequency crystal, but in all my travels I have only seen almost one person who used this.
73
-Jim
NU0C
On Sat, 03 Feb 2024 01:38:55 -0800
"Joseph K4JNG" <jgraif1@...> wrote:
> I am in the hunt for two AUX-7 boards, for my TR7 and R7. Please help if you are able¡
>
> Best 73,
> joe
> K4JNG
|
Re: Plate & Load Shift Couplers
Seems to me these springs are found in knobs to fit shafts with flats. Some knobs also have a flat, the spring fits into that and against the flat on the shaft when the knob is installed. I can't remember exactly how the spring is formed and don't have one to look at. My memory is some springs are formed into a partial arc so that one end goes into the knob and, when installed, the bowed up part is against the shaft. I also seem to remember U shaped springs but am less sure of that. The problem with makeshift substitutes is that they can jam making the knob difficult or impossible to remove again. Of course, shafts with flats are also used with knobs having a set-screw, to located them or keep them from turning.
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On 2/5/2024 1:02 PM, wb6ogd wrote: Bob,
Yes, I am talking about the little flat spring.? That must be what you are missing.? Normally
the coupler is so tight you have to pry it loose with a screwdriver against the PA cage.
I did see on one of the groups recently that someone found the little metal cutter that's inside
a dental floss container works perfectly..?? I haven't tried it though.
It is probably the same as the Drake knobs, maybe the knob repro guys have just the spring?
Or you might try a little piece of copper wire stuffed in there.
73,
Gary
WB6OGD
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
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Re: Copy of original documents
I placed it back in the original box along with the QC tag.? Date is 3/83 for info. Will store the original box and have it for my heirs.
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Roberto - YS1RS
Jim Shorney
Joseph K4JNG
David