Ah. That makes sense. The cabinet looks quite nice, BTW.
- Jerry, KF6VB
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On 2024-04-07 19:40, Stan Gammons via groups.io wrote: You use the drill bit to make the hole on the nozzle larger.?
|
You use the drill bit to make the hole on the nozzle larger.? That way
is sprays large drops, for the lack of a better word, of paint. One
holds the can about 2 ft away when spraying.
73
Stan
KM4HQE
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On 4/7/24 21:34, jerry-KF6VB wrote: On 2024-04-07 19:32, Stan Gammons via groups.io wrote:
To try to
duplicate the spackle finish; I used a #52 drill.
*** How does a drill make a spackle finish?
- Jerry, KF6VB
|
On 2024-04-07 19:32, Stan Gammons via groups.io wrote: To try to
duplicate the spackle finish; I used a #52 drill.
*** How does a drill make a spackle finish? - Jerry, KF6VB
|
Re: 78L24 regulator failure
I had a sort of similar situation. I needed to regulate a high voltage
for a tube rig. The PS that I had delivered 325V and I needed 275. I put a zener
diode across the pass transistor to guarantee that the voltage across it wouldn't fry it during turn-on and turn-off. I also used a long series string of diodes to get the 325
down to 290 or so, so the pass transistor only had to drop 15V.
- Jerry, KF6VB
|
It was a very warm day in 4 land today, so I finished painting the MS-4
cabinet. It's not "perfect" but it looks a lot better than what it did.
I'm going to leave it as is.? I used Krylon 5557 satin black. To try to
duplicate the spackle finish; I used a #52 drill.
No luck with the T-4X today. I'm going to set it aside for a while and
come back to it later.
73
Stan
KM4HQE
|
Re: 78L24 regulator failure
It is the boost voltage for the VCO so it is pretty low current. It runs one op amp that drives the tuning voltage to the varactors. Total capacitance between the 78L24 and the op amp is 3x 1uF, with an inductor in series with one of the caps. OTOH the input filter capacitor is 1uF. Apparently it doesn't take much to filter 46 KHz ripple. I don't think they run warm but I didn't check as I wanted to get the rig back on the air. I'll give it the finger test the next time I have a TR7 open. 73 -Jim NU0C On Sun, 7 Apr 2024 11:37:53 -0600 "Bill Leonard N0CU" <billincolo73@...> wrote: Jim,
Given the high input voltage, voltage spikes are certainly a possibility,
but I would also investigate how hot the device is running. High device
temps accelerate failure rates.
If I remember correctly, the protection diode across these devices is
recommended when there is a large filter cap on the output. When the input
voltage is removed, the device becomes reversed biased. The higher the
output voltage and the higher the capacitance, the more likely that there
can be a problem.
Bill N0CU
On Sun, Apr 7, 2024 at 10:13?AM Jim Shorney <jimNU0C@...> wrote:
One of my TR7s suffered a 24V regulator failure yesterday. It was just
sitting there running and failed overnight. Anecdotal evidence suggests
that the 78L24 is a high failure rate part and in my limited sample of <10
I have now replaced three over the years in different rigs. But why?
Inquiring minds want to know.
Other 78xx and 78Lxx devices are used in the 7 line gear and they don't
fail as often. Maybe it is the voltage? One data sheet that I found with
specs for the 24V chip lists 40V as the maximum input voltage. Input on the
TR7 PS board was measured at about 36V unloaded. Maybe spikes stressing the
IC causing eventual failure. Reducing the input voltage with a small series
resistor is something that could be investigated. Ten volts of headroom in
this circuit seems like overkill (pun intended). I have not tried this.
One thing in the back of my mind was that a protection diode across the
regulator is suggested in some 78xx data sheets. I had to go back to an
older TI data sheet to find it.
The idea here is that the regulator can be damaged if for some reason the
input voltage drops below the output voltage. A back biased diode from
output to input supposedly prevents this. I don't know that this is what is
happening but diodes are cheap (or sometimes free) so I added one.
If both me and the rig are still around in 20 years I will let you know
how it works out.
--
73
-Jim
NU0C
|
Re: 78L24 regulator failure
Jim, Given the high input voltage, voltage spikes are certainly a possibility, but I would also investigate how hot the device is running. High device temps accelerate failure rates. If I remember correctly, the protection diode across these devices is recommended when there is a large filter cap on the output. When the input voltage is removed, the device becomes reversed biased. The higher the output voltage and the higher the capacitance, the more likely that there can be a problem. Bill N0CU
On Sun, Apr 7, 2024 at 10:13?AM Jim Shorney < jimNU0C@...> wrote:
One of my TR7s suffered a 24V regulator failure yesterday. It was just sitting there running and failed overnight. Anecdotal evidence suggests that the 78L24 is a high failure rate part and in my limited sample of <10 I have now replaced three over the years in different rigs. But why? Inquiring minds want to know.
Other 78xx and 78Lxx devices are used in the 7 line gear and they don't fail as often. Maybe it is the voltage? One data sheet that I found with specs for the 24V chip lists 40V as the maximum input voltage. Input on the TR7 PS board was measured at about 36V unloaded. Maybe spikes stressing the IC causing eventual failure. Reducing the input voltage with a small series resistor is something that could be investigated. Ten volts of headroom in this circuit seems like overkill (pun intended). I have not tried this.
One thing in the back of my mind was that a protection diode across the regulator is suggested in some 78xx data sheets. I had to go back to an older TI data sheet to find it.
The idea here is that the regulator can be damaged if for some reason the input voltage drops below the output voltage. A back biased diode from output to input supposedly prevents this. I don't know that this is what is happening but diodes are cheap (or sometimes free) so I added one.
If both me and the rig are still around in 20 years I will let you know how it works out.
--
73
-Jim
NU0C
|
Looking for Crystals? 23.5 mhz? ?and? 25.5
Regards KB9ASU
|
Hi Richard,
Thanks.
I worked on the T-4X earlier and was able to adjust front trimmers. ?With 1 volt at the injection connector, I have around 1.8 volts at the test point on all bands. ?The next step of the alignment is where I¡¯m having trouble. ?With rf tune set per the manual I don¡¯t get any power out. ?I have to move the rf tune to a different position to get any power out. ?When I get back home I think I¡¯ll check the crystals with my NanoVNA.
73
Stan? KM4HQE?
On Thu, Apr 4, 2024 at 11:41 PM, Richard Knoppow < 1oldlens1@...> wrote: The rotor is connected to a terminal which faces pretty much straight
out of the bottom of the switch. Look carefully with the power off, its
not hard to find. You need to do this in two places, both as above are
easy to find. Insulate a screwdriver with shrink tubing so only the tip
is exposed. It will detune one side of the circuit so that other can be
peaked. Do both sides a couple of times. Despite some discussion in the
past it IS necessary and makes a difference in the tuning.
Another trick sometimes necessary on 160 and 10 meters if the
trimmers are out of range, is to set the tuning to a higher frequency
than is specified. That will bring the trimmers into range. Also works
on the receiver.
On 4/4/2024 9:44 AM, Stan Gammons via groups.io wrote:
> Hi Steve,
>
> I haven¡¯t tried the 80/75 meter alignment. I don¡¯t have the manual in
> front of me at the moment but I seem to recall it says to use an
> insulated screwdriver to touch the switch rotor to detune the circuit.
> Do they mean touch the switch shaft?
>
> 73
>
> Stan
> KM4HQE
>
>
>
> On Thu, Apr 4, 2024 at 11:18 AM, Steve Wedge, W1ES/4 via groups.io
> <w1es@... <mailto:On Thu, Apr 4, 2024 at 11:18 AM,
> Steve Wedge, W1ES/4 via groups.io <<a href=>> wrote:
>> Have you tried doing the alignment on 80/75 per the manual? I believe
>> it is set up pretty high in the band.
>>
>> I agree that you¡¯re probably dealing with old finals based on the high
>> band figures.
>>
>> Steve Wedge, W1ES/4
>>
>> Time flies like an arrow. Fruit flies like a banana.
>>
>>
>> Sent from Proton Mail <https://proton.me/mail/home> for iOS
>>
>>
>> On Thu, Apr 4, 2024 at 12:01 PM, Stan Gammons via groups.io
>> <buttercup11421@... <mailto:On Thu, Apr 4, 2024
>> at 12:01 PM, Stan Gammons via groups.io <<a href=>> wrote:
>>> I got around to replacing the grid resistors. I get the following now.
>>>
>>> 3.5 Mhz -75 watts
>>> 3.98 Mhz - 30 watts
>>> 7.2 Mhz - 100 watts
>>> 14.2 Mhz - 100 watts
>>> 21.2 Mhz - 40 watts
>>> 28.7 Mhz - 10 watts
>>>
>>> Unsure why the power drops off on the upper end of 80/75 meters. I'm
>>> sure the low power on 15 and 10 meters is due to weak finals.
>>>
>>> 73
>>>
>>> Stan
>>> KM4HQE
>>>
>>>
>>> On 3/31/24 19:11, Steve Wedge, W1ES/4 via groups.io wrote:
>>>> Check your other bands.
>>>>
>>>> We need to know if your band oscillator is kaput.
>>>>
>>>> Steve Wedge, W1ES/4
>>>>
>>>> Time flies like an arrow. Fruit flies like a banana.
>>>>
>>>>
>>>> Sent from Proton Mail <https://proton.me/mail/home> for iOS
>>>>
>>>>
>>>> On Sun, Mar 31, 2024 at 19:42, Stan Gammons via groups.io
>>>> <buttercup11421@... <mailto:On Sun, Mar 31,
>>>> 2024 at 19:42, Stan Gammons via groups.io <<a href=>> wrote:
>>>>> Halfway between 10 and 0.
>>>>>
>>>>> Yes, checking the oscillator is next on the to do list.
>>>>>
>>>>>
>>>>> 73
>>>>>
>>>>> Stan
>>>>> KM4HQE
>>>>>
>>>>>
>>>>> On 3/31/24 18:38, Steve Wedge, W1ES/4 via groups.io wrote:
>>>>> > Where is your RF TUNE setting at max?
>>>>> >
>>>>> > I'm guessing you have no band oscillator...
>>>>> >
>>>>> > Steve Wedge, W1ES/4
>>>>> >
>>>>> > Time flies like an arrow. Fruit flies like a banana.
>>>>> >
>>>>> > Sent with Proton Mail secure email.
>>>>> >
>>>>> > On Sunday, March 31st, 2024 at 7:14 PM, Stan Gammons via
>>>>> groups.io <buttercup11421@...> wrote:
>>>>> >
>>>>> >> I have a T-4X which has some odd problems. On 40 meters it will
>>>>> put out
>>>>> >> 100 watts, but the output on other bands, 80 for example is about 50
>>>>> >> watts. On 75 meters output is like 10 watts. Output on higher
>>>>> bands is
>>>>> >> also low. Weak finals? Yeah, I know it's not a real test, but the
>>>>> >> Sylvania tubes check good with my B&K 707. The grid resistors
>>>>> are out of
>>>>> >> tolerance. One reads 77 ohms and the other reads 84 ohms. I also
>>>>> found
>>>>> >> that Drake failed to solder C51 which goes from V5 pin 1 to
>>>>> ground. But,
>>>>> >> I doubt replacing the grid resistors and soldering C51 will fix the
>>>>> >> problem I have. So, I'm looking at doing an alignment. My
>>>>> question is
>>>>> >> what does Drake mean when they say detune T5 and T4 by touching an
>>>>> >> insulated screwdriver on the rotor of S4A and S4B? Touch the
>>>>> >> screwdriver on the switch shaft in front of those switch wafers?
>>>>> >>
>>>>> >> 73
>>>>> >>
>>>>> >> Stan
>>>>> >> KM4HQE
>>>>> >>
>>>>> >>
>>>>> >>
>>>>> >>
>>>>> >>
>>>>> >
>>>>> >
>>>>> >
>>>>> >
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>
>
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
One of my TR7s suffered a 24V regulator failure yesterday. It was just sitting there running and failed overnight. Anecdotal evidence suggests that the 78L24 is a high failure rate part and in my limited sample of <10 I have now replaced three over the years in different rigs. But why? Inquiring minds want to know.
Other 78xx and 78Lxx devices are used in the 7 line gear and they don't fail as often. Maybe it is the voltage? One data sheet that I found with specs for the 24V chip lists 40V as the maximum input voltage. Input on the TR7 PS board was measured at about 36V unloaded. Maybe spikes stressing the IC causing eventual failure. Reducing the input voltage with a small series resistor is something that could be investigated. Ten volts of headroom in this circuit seems like overkill (pun intended). I have not tried this.
One thing in the back of my mind was that a protection diode across the regulator is suggested in some 78xx data sheets. I had to go back to an older TI data sheet to find it.
The idea here is that the regulator can be damaged if for some reason the input voltage drops below the output voltage. A back biased diode from output to input supposedly prevents this. I don't know that this is what is happening but diodes are cheap (or sometimes free) so I added one.
If both me and the rig are still around in 20 years I will let you know how it works out.
--
73
-Jim
NU0C
|
Re: Removing top case cover of Drake L-4B
No, you do not have to remove the power connectors to take the covers of the RF deck. You DO have to take the bottom cover off the L4-PS and disconnect the line cord to remove the top cover of the PS, as described in a previous post. On Fri, 5 Apr 2024 13:44:10 +0000 (UTC) "Ralph Mowery via groups.io" <ku4pt@...> wrote: I have not had my cover off in a long time but seem to think that there are tabs so that you have to remove the power connector before the covers can be removed.? Probably a safety device to make sure you disconnect the power supply before putting your hands inside.
Ralph ku4pt -- 73 -Jim NU0C
|
Sounds like a relay contact problem.?
Steve Wedge, W1ES/4
Time flies like an arrow. Fruit flies like a banana.
On Thu, Apr 4, 2024 at 19:08, Tim KD2SC via groups.io < kd2sc@...> wrote:
Kevin I still troubleshooting a couple of things. The receiver in my TR4C just drops dead. I tap the top of the capacitor and it comes alive again. So, I'm not sure I need the VFO assembly. yet. In your collection would you have the electrolytic capacitor for a TR4C and I'm also looking for 2 of the wire clips thar would hold the transmit/ receive relay in place. It's a little piece of thin u-shaped spring wire. I'll let you know about the VFO as soon as I can.
Thanks? Tim KD2SC
On Thursday, March 21, 2024 at 01:38:26 PM EDT, Kevin Kampman <k8kvn@...> wrote:
I have the crystals listed in this pdf file, both new and used. They were WA8SAJ's inventory:
Let me know which you'd be interested in. My email is good on QRZ.?
--
73, Kevin, K8KVN
|
Re: Removing top case cover of Drake L-4B
Just two quick comments.
Sometimes it helps to use a thin screwdriver to ease the covers off of the RF deck. ?Slight pry on the front area, then the rear, and back and forth. ?Then pry the sides slightly outward as the respective cover is removed. ?Why? ?There are at least two variants of front panels, one has a silver edge, the other does not. ?Careless removal of the covers can result in scratching the front panel, more noticeable with the one without the silver edge.
Too, with the top cover off, might be a good idea to lubricate the blower bearings, and clean bandswitch contacts, etc. ? As to the bearings, I use a light, non-detergent small motor oil. ? I put some paper towels under the area of the motor, fill the oil ports to slight overflow, and then let it sit overnight. ?Minor cleanup and then it is ready for another year of service.
There are a lot of experts out there that can provide valuable info about the recent topics and I'm sure they will be sharing with us.
73,
Evan, K9SQG
On Friday, April 5, 2024 at 09:44:14 AM EDT, Ralph Mowery via groups.io <ku4pt@...> wrote:
I have not had my cover off in a long time but seem to think that there are tabs so that you have to remove the power connector before the covers can be removed.? Probably a safety device to make sure you disconnect the power supply before putting your hands inside.
Ralph ku4pt
On Friday, April 5, 2024 at 01:14:31 AM EDT, Jim Shorney <jimnu0c@...> wrote:
Yes there are tabs that align the edges of the two covers. But they are not relevant to order of removal.
73
-Jim
NU0C
On Fri, 5 Apr 2024 00:45:04 -0400 "Jerry Kessler" < N4JL.cw@...> wrote: > It's been a while since I've had my L-4B apart but isn't there a tab on at > least one corner of the cabinet (top or bottom) similar to a TR-4 cabinet > where in order to remove the top cover it helps to loosen the screws on the > bottom cover? > > Jerry, N4JL
|
You can get the filter caps for your TR4C from Hayseed Hamfest.?
73's,
Mark, WB0IQK
|
Why not just replace the movement?
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On Apr 5, 2024, at 9:42?AM, KM W2AQY via groups.io <kevinmulter@...> wrote:
?Hello to everyone in the group,
I am looking for a plate meter for my Drake TR-4. Let me know if anyone has one to sell.
Kevin M¡ª W2AQY
|
Re: Removing top case cover of Drake L-4B
I have not had my cover off in a long time but seem to think that there are tabs so that you have to remove the power connector before the covers can be removed.? Probably a safety device to make sure you disconnect the power supply before putting your hands inside.
Ralph ku4pt
On Friday, April 5, 2024 at 01:14:31 AM EDT, Jim Shorney <jimnu0c@...> wrote:
Yes there are tabs that align the edges of the two covers. But they are not relevant to order of removal.
73
-Jim
NU0C
On Fri, 5 Apr 2024 00:45:04 -0400 "Jerry Kessler" < N4JL.cw@...> wrote: > It's been a while since I've had my L-4B apart but isn't there a tab on at > least one corner of the cabinet (top or bottom) similar to a TR-4 cabinet > where in order to remove the top cover it helps to loosen the screws on the > bottom cover? > > Jerry, N4JL
|
Hello to everyone in the group,
I am looking for a plate meter for my Drake TR-4. Let me know if anyone has one to sell.
Kevin M¡ª W2AQY
|
Re: Removing top case cover of Drake L-4B
Yes, I have. But that wasn't the OP's question. 73 -Jim NU0C On Fri, 5 Apr 2024 05:24:07 +0000 "Jerry Kessler" <N4JL.cw@...> wrote: Not to the order of removal. My experience has been that the tabs cause binding unless the opposite cover is loosened. Jim - have you noticed that?
Jerry, N4JL
|
Re: Removing top case cover of Drake L-4B
Not to the order of removal. My experience has been that the tabs cause binding unless the opposite cover is loosened. Jim - have you noticed that?
Jerry, N4JL?
Get
toggle quoted message
Show quoted text
Yes there are tabs that align the edges of the two covers. But they are not relevant to order of removal.
73
-Jim
NU0C
On Fri, 5 Apr 2024 00:45:04 -0400
"Jerry Kessler" <N4JL.cw@...> wrote:
> It's been a while since I've had my L-4B apart but isn't there a tab on at
> least one corner of the cabinet (top or bottom) similar to a TR-4 cabinet
> where in order to remove the top cover it helps to loosen the screws on the
> bottom cover?
>
> Jerry, N4JL
|
Re: Removing top case cover of Drake L-4B
Yes there are tabs that align the edges of the two covers. But they are not relevant to order of removal. 73 -Jim NU0C On Fri, 5 Apr 2024 00:45:04 -0400 "Jerry Kessler" <N4JL.cw@...> wrote: It's been a while since I've had my L-4B apart but isn't there a tab on at
least one corner of the cabinet (top or bottom) similar to a TR-4 cabinet
where in order to remove the top cover it helps to loosen the screws on the
bottom cover?
Jerry, N4JL
|
Jim Shorney
