Re: Another Mistake: L7 HV calibration pot ?
There are two interlocks on the L7 RF deck. ?One on the top and one the bottom, right side.
Jim so how do I disable the interlocks with the top cover off? And the adjustment pot is on the back panel near the fan cover inside of the chassis or outside and is it hot as in use an insulated tool?
Thanks Tim
On Saturday, January 4, 2025 at 07:53:47 PM EST, Jim Shorney via groups.io <jimnu0c@...> wrote:
I think it is the hole near the center of the chassis just outside of the fan cover. I suspect they state that it is not user accessible because they don't want anyone messing with it who does not thoroughly familiar with the ways of high voltage. You need to adjust it with the top cover off and the interlocks disabled so you can measure the high voltage with a suitable high voltage probe. Any ordinary Voltmeter not buffered by a HV probe will complain loudly before it disappears in a cloud of smoke. The same might happen to an inexperienced technician.
If the resistors are indeed out of range there was a ham selling suitable high voltage rated resistors online for a while but I don't recall who it was.
On Sun, 5 Jan 2025 00:26:15 +0000 (UTC) "Evan via groups.io" <k9sqg@...> wrote: >? This is the revised revision of the original revised revision, subject to change, about the L7 HV calibration pot. ? Not sure if it is accessible from that hole between the two coax connectors on the rear panel. > I apologize for the confusion. ?Settling an estate, sleep deprived, etc. and not sure anything I'm posting right now has any credibility. > 73, > Evan, K9SQG >? ? On Saturday, January 4, 2025 at 07:14:35 PM EST, Evan via groups.io <k9sqg@...> wrote:? > >? My memory is failing. ? The HV calibration pot on the L7 ?is not accessible from the rear panel. > 73, > Evan, K9SQG? -- 73 -Jim NU0C
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Re: Another Mistake: L7 HV calibration pot ?
Yes Jim, HV doesn't give you a second chance. ?HV, like the air and sea, is terribly unforgiving of mistakes. ?I have Triplett and HP meters with ?probes and 10KV scales but even so, I don't touch them when dealing with HV and keep one hand in my pocket.
Thanks for your comments.
73,
Evan, K9SQG
I think it is the hole near the center of the chassis just outside of the fan cover. I suspect they state that it is not user accessible because they don't want anyone messing with it who does not thoroughly familiar with the ways of high voltage. You need to adjust it with the top cover off and the interlocks disabled so you can measure the high voltage with a suitable high voltage probe. Any ordinary Voltmeter not buffered by a HV probe will complain loudly before it disappears in a cloud of smoke. The same might happen to an inexperienced technician.
If the resistors are indeed out of range there was a ham selling suitable high voltage rated resistors online for a while but I don't recall who it was.
On Sun, 5 Jan 2025 00:26:15 +0000 (UTC)
"Evan via groups.io" <k9sqg@...> wrote:
>? This is the revised revision of the original revised revision, subject to change, about the L7 HV calibration pot. ? Not sure if it is accessible from that hole between the two coax connectors on the rear panel.
> I apologize for the confusion. ?Settling an estate, sleep deprived, etc. and not sure anything I'm posting right now has any credibility.
> 73,
> Evan, K9SQG
>? ? On Saturday, January 4, 2025 at 07:14:35 PM EST, Evan via groups.io <k9sqg@...> wrote:?
>
>? My memory is failing. ? The HV calibration pot on the L7 ?is not accessible from the rear panel.
> 73,
> Evan, K9SQG?
--
73
-Jim
NU0C
|
First thought was that you have the Calibrator button depressed but that should be obvious because you could tune away from it with the VFO. As much as you have been digging around in there you may have knocked some adjustments off. I would do the frequency alignment starting at section 3-1 (10V adjustment) and proceeding through section 3-6 in the service manual. The fixed passband pots in 3-6 are particularly prone to getting bumped and some ops have replaced them with 10 turn trimpots. But I recommend the full frequency alignment so you know everything is correct. On Sat, 4 Jan 2025 17:38:15 -0400 "Jim Harris via groups.io" <radiove1rb@...> wrote: yes it was a very pleasant surprised when I turned it on and it worked, The
problem I have now id that when i SWITCH FROM lsb OR usB TO cw i get a
signal in the receiver 5 over 9 and if I press the morse key I hear the
tone as well. It does not seem to mute that signal. I also noticed that if
I use the PBT I can hear a tone and can swing the passband and I can go
back and forth past it. Almost sounds like an oscillation. Any ideas?
Thanks,
Jim VE1RB -- 73 -Jim NU0C
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Re: Another Mistake: L7 HV calibration pot ?
Jim so how do I disable the interlocks with the top cover off? And the adjustment pot is on the back panel near the fan cover inside of the chassis or outside and is it hot as in use an insulated tool?
Thanks Tim
On Saturday, January 4, 2025 at 07:53:47 PM EST, Jim Shorney via groups.io <jimnu0c@...> wrote:
I think it is the hole near the center of the chassis just outside of the fan cover. I suspect they state that it is not user accessible because they don't want anyone messing with it who does not thoroughly familiar with the ways of high voltage. You need to adjust it with the top cover off and the interlocks disabled so you can measure the high voltage with a suitable high voltage probe. Any ordinary Voltmeter not buffered by a HV probe will complain loudly before it disappears in a cloud of smoke. The same might happen to an inexperienced technician.
If the resistors are indeed out of range there was a ham selling suitable high voltage rated resistors online for a while but I don't recall who it was.
On Sun, 5 Jan 2025 00:26:15 +0000 (UTC)
"Evan via groups.io" <k9sqg@...> wrote:
>? This is the revised revision of the original revised revision, subject to change, about the L7 HV calibration pot. ? Not sure if it is accessible from that hole between the two coax connectors on the rear panel.
> I apologize for the confusion. ?Settling an estate, sleep deprived, etc. and not sure anything I'm posting right now has any credibility.
> 73,
> Evan, K9SQG
>? ? On Saturday, January 4, 2025 at 07:14:35 PM EST, Evan via groups.io <k9sqg@...> wrote:?
>
>? My memory is failing. ? The HV calibration pot on the L7 ?is not accessible from the rear panel.
> 73,
> Evan, K9SQG?
--
73
-Jim
NU0C
|
Re: Another Mistake: L7 HV calibration pot ?
I think it is the hole near the center of the chassis just outside of the fan cover. I suspect they state that it is not user accessible because they don't want anyone messing with it who does not thoroughly familiar with the ways of high voltage. You need to adjust it with the top cover off and the interlocks disabled so you can measure the high voltage with a suitable high voltage probe. Any ordinary Voltmeter not buffered by a HV probe will complain loudly before it disappears in a cloud of smoke. The same might happen to an inexperienced technician. If the resistors are indeed out of range there was a ham selling suitable high voltage rated resistors online for a while but I don't recall who it was. On Sun, 5 Jan 2025 00:26:15 +0000 (UTC) "Evan via groups.io" <k9sqg@...> wrote: This is the revised revision of the original revised revision, subject to change, about the L7 HV calibration pot. ? Not sure if it is accessible from that hole between the two coax connectors on the rear panel.
I apologize for the confusion. ?Settling an estate, sleep deprived, etc. and not sure anything I'm posting right now has any credibility.
73,
Evan, K9SQG
On Saturday, January 4, 2025 at 07:14:35 PM EST, Evan via groups.io <k9sqg@...> wrote:
My memory is failing. ? The HV calibration pot on the L7 ?is not accessible from the rear panel.
73,
Evan, K9SQG -- 73 -Jim NU0C
|
Re: Another Mistake: L7 HV calibration pot ?
This is the revised revision of the original revised revision, subject to change, about the L7 HV calibration pot. ? Not sure if it is accessible from that hole between the two coax connectors on the rear panel.
I apologize for the confusion. ?Settling an estate, sleep deprived, etc. and not sure anything I'm posting right now has any credibility.
73,
Evan, K9SQG
My memory is failing. ? The HV calibration pot on the L7 ?is not accessible from the rear panel.
73,
Evan, K9SQG
|
My Mistake: L7 HV calibration pot
My memory is failing. ? The HV calibration pot on the L7 ?is not accessible from the rear panel.
73,
Evan, K9SQG
|
Re: Small lamp reference for Drake L7
Tim,
Not sure what to say. ? All the L7s I've owned or serviced had an access hole on the back panel for inserting an insulated tool for adjustment. ?Now the one on the L4B is different though.
I "responded" to your message in the reflector with a different title so all is well.
73,
Evan
Evan
No I have not done that in the manual from Drake it notes " not user accessible" tell me about it.
Evan I have purchased many parts for the Drake amps from you in the past and have used them.
Sorry to Bill I did not realize I posted this wrong.
Thanks Tim
On Saturday, January 4, 2025 at 06:57:53 PM EST, Bill KJ5BNE via groups.io <whb5k@...> wrote:
You¡¯ve posted a new topic about meter shunts. ?Please go to the .io group and re-post your question with a new appropriate topic title. ?Otherwise people researching this issue in the future won¡¯t be able to find the original question and possibly useful responses.
Thanks & 73, Bill AI5RP ++++++++++++++++ Bill Blodgett Arlington, Texas
On Jan 4, 2025, at 5:35?PM, amfone via groups.io <amfone20000@...> wrote:
?
Hello group. I need to replace the meter shunts for the Drake L7, LV and HV reading low. From the schematic Drake used 8 2.3 meg 1/2 watt resistors it appears from the schematic and manual pictures they are located right behind the 3-500Zs. Any advice gladly accepted.
Tim
WB8UHZ
On Saturday, January 4, 2025 at 03:14:00 PM EST, Mohamed VA2MKX via groups.io <va2mkx@...> wrote:
Thanks a lot for the reference, appreciated ! :)
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Re: Small lamp reference for Drake L7
Evan
No I have not done that in the manual from Drake it notes " not user accessible" tell me about it.
Evan I have purchased many parts for the Drake amps from you in the past and have used them.
Sorry to Bill I did not realize I posted this wrong.
Thanks Tim
On Saturday, January 4, 2025 at 06:57:53 PM EST, Bill KJ5BNE via groups.io <whb5k@...> wrote:
You¡¯ve posted a new topic about meter shunts. ?Please go to the .io group and re-post your question with a new appropriate topic title. ?Otherwise people researching this issue in the future won¡¯t be able to find the original question and possibly useful responses.
Thanks & 73, Bill AI5RP ++++++++++++++++ Bill Blodgett Arlington, Texas
On Jan 4, 2025, at 5:35?PM, amfone via groups.io <amfone20000@...> wrote:
?
Hello group. I need to replace the meter shunts for the Drake L7, LV and HV reading low. From the schematic Drake used 8 2.3 meg 1/2 watt resistors it appears from the schematic and manual pictures they are located right behind the 3-500Zs. Any advice gladly accepted.
Tim
WB8UHZ
On Saturday, January 4, 2025 at 03:14:00 PM EST, Mohamed VA2MKX via groups.io <va2mkx@...> wrote:
Thanks a lot for the reference, appreciated ! :)
|
Re: Small lamp reference for Drake L7
You¡¯ve posted a new topic about meter shunts. ?Please go to the .io group and re-post your question with a new appropriate topic title. ?Otherwise people researching this issue in the future won¡¯t be able to find the original question and possibly useful responses.
Thanks & 73, Bill AI5RP ++++++++++++++++ Bill Blodgett Arlington, Texas
toggle quoted message
Show quoted text
On Jan 4, 2025, at 5:35?PM, amfone via groups.io <amfone20000@...> wrote:
?
Hello group. I need to replace the meter shunts for the Drake L7, LV and HV reading low. From the schematic Drake used 8 2.3 meg 1/2 watt resistors it appears from the schematic and manual pictures they are located right behind the 3-500Zs. Any advice gladly accepted.
Tim
WB8UHZ
On Saturday, January 4, 2025 at 03:14:00 PM EST, Mohamed VA2MKX via groups.io <va2mkx@...> wrote:
Thanks a lot for the reference, appreciated ! :)
|
Calibration of L7 plate voltage resistors
----- Forwarded Message -----
Tim,
Have you already attempted a calibration via the pot on the back panel of the RF deck?
73,
Evan, K9SQG
Hello group. I need to replace the meter shunts for the Drake L7, LV and HV reading low. From the schematic Drake used 8 2.3 meg 1/2 watt resistors it appears from the schematic and manual pictures they are located right behind the 3-500Zs. Any advice gladly accepted.
Tim
WB8UHZ
On Saturday, January 4, 2025 at 03:14:00 PM EST, Mohamed VA2MKX via groups.io <va2mkx@...> wrote:
Thanks a lot for the reference, appreciated ! :)
|
Re: Small lamp reference for Drake L7
Tim,
Have you already attempted a calibration via the pot on the back panel of the RF deck?
73,
Evan, K9SQG
Hello group. I need to replace the meter shunts for the Drake L7, LV and HV reading low. From the schematic Drake used 8 2.3 meg 1/2 watt resistors it appears from the schematic and manual pictures they are located right behind the 3-500Zs. Any advice gladly accepted.
Tim
WB8UHZ
On Saturday, January 4, 2025 at 03:14:00 PM EST, Mohamed VA2MKX via groups.io <va2mkx@...> wrote:
Thanks a lot for the reference, appreciated ! :)
|
Re: Small lamp reference for Drake L7
Hello group. I need to replace the meter shunts for the Drake L7, LV and HV reading low. From the schematic Drake used 8 2.3 meg 1/2 watt resistors it appears from the schematic and manual pictures they are located right behind the 3-500Zs. Any advice gladly accepted.
Tim
WB8UHZ
On Saturday, January 4, 2025 at 03:14:00 PM EST, Mohamed VA2MKX via groups.io <va2mkx@...> wrote:
Thanks a lot for the reference, appreciated ! :)
|
Jim:
Not sure which one is "blown".? But all four ceramic feedthroughs shown in the pic are .001 uf/350V rated.
But.....your HV line (+650VDC) is missing where the unused hole is.? Is this what you were referring to?? If so, there is no feedthrough capacitor at that point.? A wire carrying the B+ high voltage to the PA tubes passes through a piece of friction fit plastic insulation.? You will have to make your own - shouldn't be too hard.? All 4 line transmitters are the same in this?regard.
73 Peter VE7PS
Can anyone recommend a subsitute for a blown feed-thru cap that I need ?
?
Appreciate any help?
?
Regards
?
W6TTY
?
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Can anyone recommend a subsitute for a blown feed-thru cap that I need ?
?
Appreciate any help?
?
Regards
?
W6TTY
?
|
yes it was a very pleasant surprised when I turned it on and it worked, The problem?I have now id that?when i SWITCH FROM lsb OR usB TO cw i get a signal in the receiver 5 over 9 and if I press the morse key I hear the tone as well. It does not seem to mute that signal. I also noticed that if I use the PBT I can hear?a tone and can swing the passband and I can go back?and forth past it. Almost?sounds like an oscillation. Any ideas? Thanks,
Jim VE1RB
Well, there ya go! Nice catch. Doesn't it feel good? That is an interesting failure. Just a wild guess but I am thinking the lead had a weak spot, maybe a nick or a spot of corrosion, that caused it to break after years of thermal cycling.
On Sat, 4 Jan 2025 07:19:51 -0400
"Jim Harris via " <radiove1rb=[email protected]> wrote:
> I just wanted to let you know I managed to get the high VCO working. I
> was removing transistors and checking them on my tester, and when I
> removed Q504 and noticed that the Gate lead was broken off half way down
> to the board. I tested it and it was okay so had thought I had done that
> so I put it back in and soldered the lead together. Put the radio back
> together and decided to see what the DR7 readout said and the radio
> happened to be on the 10 meter band and it was showing the correct
> frequency. Checked 15 meter and that was working as well. I still have
> one problem but will post later on that. My thanks for all the help on
> this problem to everyone.
>
> Jim VE1RB
--
73
-Jim
NU0C
|
Re: Small lamp reference for Drake L7
Thanks a lot for the reference, appreciated ! :)
|
Re: R4C Sherwood audio mod questions
I stand corrected.? Rob, NC0B
?
toggle quoted message
Show quoted text
From: [email protected] [mailto:[email protected]]
On Behalf Of Paul Christensen via groups.io
Sent: Saturday, January 04, 2025 6:52 AM
To: [email protected]
Subject: Re: [DRAKE-RADIO] R4C Sherwood audio mod questions
?
On Sat, Jan 4, 2025 at 05:19 AM, Floyd - K8AC wrote:
>The text specifies the inverting input capacitor as 200 uF while the schematic shows it as 330 uF.
The computed -3 dB high-pass turnover frequency is 123 Hz for 330 uF, and 204 Hz for 200 uF.? Pick either one based on personal roll-off preference.
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Re: R4C Sherwood audio mod questions
Hi Floyd,
?
Thanks for pointing that out.? I¡¯ll look at the board in my R-4C and see which is correct. It likely doesn¡¯t make much difference with the inverting input impedance.
?
Rob, NC0B
?
toggle quoted message
Show quoted text
From: [email protected] [mailto:[email protected]]
On Behalf Of Floyd - K8AC via groups.io
Sent: Saturday, January 04, 2025 6:19 AM
To: [email protected]
Subject: Re: [DRAKE-RADIO] R4C Sherwood audio mod questions
?
Rob - maybe it makes no difference at all, but there is a discrepancy in the component values for the AMP-4.? The text specifies the inverting input capacitor as 200 uF while the schematic shows it as 330 uF.
73 & Happy New Year, Floyd - K8AC
|
Well, there ya go! Nice catch. Doesn't it feel good? That is an interesting failure. Just a wild guess but I am thinking the lead had a weak spot, maybe a nick or a spot of corrosion, that caused it to break after years of thermal cycling. On Sat, 4 Jan 2025 07:19:51 -0400 "Jim Harris via groups.io" <radiove1rb@...> wrote: I just wanted to let you know I managed to get the high VCO working. I
was removing transistors and checking them on my tester, and when I
removed Q504 and noticed that the Gate lead was broken off half way down
to the board. I tested it and it was okay so had thought I had done that
so I put it back in and soldered the lead together. Put the radio back
together and decided to see what the DR7 readout said and the radio
happened to be on the 10 meter band and it was showing the correct
frequency. Checked 15 meter and that was working as well. I still have
one problem but will post later on that. My thanks for all the help on
this problem to everyone.
Jim VE1RB -- 73 -Jim NU0C
|
Jim Shorney
Rob Sherwood