Re: L75 Amp Main Power Switch Availability
Great info!!! Will save it.? Thanks for sharing.
Rob
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On Mar 13, 2021, at 07:44, Gregory Beat via groups.io <w9gb@...> wrote:
? [Edited Message Follows]
Rob - The Power Switch used on the Drake L75 HF Amplifier was Very Common in 1960s and 1970s. I was used as the Power Switch on Window Air Conditioners (240 VAC) in North America. Numerous Rocker Switch manufacturers (Eaton, Carling, etc.) Eaton still manufacturers this Rocker Switch series: Rockette (page 56-57 of catalog)
—
Look at 1960s Star Trek episodes, and you will see that switch.
Used ones can be “Harvested” from Junk Yards where old Air Conditioners are sent, OR
you can find NOS switches at HVAC contractors with historic parts inventory.
==
For those with DIY Skills, disassembly can repair many (corrosion, carbon from Arc).
Need to Replace the Drake L75 Band Switch?
gb
|
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On Mar 13, 2021, at 8:11 AM, MIke Stover <n9qr@...> wrote:
?So I can tighten a loose foot, attach replacement full height rear feet AND inspect the inner workings.....That enuff reasons??
--
Mike Stover N9QR
Fort Wayne, IN
N9QR@...
|
So I can tighten a loose foot, attach replacement full height rear feet AND inspect the inner workings.....That enuff reasons??
--
Mike Stover N9QR
Fort Wayne, IN
N9QR@...
|
Re: L75 Amp Main Power Switch Availability
Rob - The Power Switch used on the Drake L75 HF Amplifier was Very Common in 1960s and 1970s. I was used as the Power Switch on Window Air Conditioners (240 VAC) in North America. Numerous Rocker Switch manufacturers (Eaton, Carling, etc.) Eaton still manufacturers this Rocker Switch series: Rockette (page 56-57 of catalog)
—
Look at 1960s Star Trek episodes, and you will see that switch.
Used ones can be “Harvested” from Junk Yards where old Air Conditioners are sent, OR
you can find NOS switches at HVAC contractors with historic parts inventory.
==
For those with DIY Skills, disassembly can repair many (corrosion, carbon from Arc).
Need to Replace the Drake L75 Band Switch?
gb
|
Re: L75 Amp Main Power Switch Availability
Maybe, maybe not. You may be able to find out on the NTE web site. The originals are IRC SPH 0.82Ω 2W 73 -Jim NU0C On Fri, 12 Mar 2021 20:45:03 -0600 "Roberto - YS1RS via groups.io" <ys1rs@...> wrote: The ones I ordered are from NTE electronics.... maybe are not the ones needed for safety....?
Ups
Rob
YS1RS
On Mar 12, 2021, at 19:36, Jim Shorney <jshorney@...> wrote:
?
Harbach also has them. Not that these are failsafe safety resistors.
73
-Jim
NU0C
On Fri, 12 Mar 2021 17:18:08 -0600
"Roberto - YS1RS via groups.io" <ys1rs@...> wrote:
Yes, found them there.
I just placed a small order of three.
Will take 15 days to come.
Now the sweet waiting with patience.
73 de Rob
YS1RS
On Mar 12, 2021, at 16:23, Dick <w1ksz@...> wrote: ?
Those Resistors are available on e-Bay.
73, Dick, W1KSZ
From: [email protected] <[email protected]> on behalf of Roberto - YS1RS via groups.io <ys1rs@...>
Sent: Friday, March 12, 2021 3:16 PM
To: [email protected] <[email protected]>
Subject: Re: [DRAKE-RADIO] L75 Amp Main Power Switch Availability
Hola Dave and group...
Yes! I've sinned. Don't kick me off the group, please... but availability of parts is not always easy here in YS; specially 2W and higher wattage resistors or high voltage parts for applications found in tube equipment.
I am using modern caps found locally 150uF x 450 VDC x 105 degrees, which thought I was not going to find but was blessed finding them.
Had to modify the boards though. These amps are scarce so no upgrade boards are available for them from commercial sources. All I've done is completely reversible though.
Found one diode burned out and another disolved in my hands so practically replaced them all.
Modern 2 watt resistors went in also, as all the original were high in value - out of tolerance.
Looks like someone else was in here before me, cause one 1/4W resistor that belongs to the meter network was replaced by a 1/2W. All that has now been corrected.
Had problems with the push button meter switches not closing the circuits correctly.
I guess all those years standing there, on storage, without been in use pass the bill, but now has been lubricated and contact cleaner went in to clean contacts and seems to be working as they should.
This amp belonged to a good friend who became SK eight years ago and the amp has been on storage since. I acquired it from his XYL and will be loved and used in my shack.
The only resistor I have not been able to find locally has been R46, the 0.82 ohm x 2 Watt resistor, that acts as a fuse. Too specialized to be found here. It is cracked.
Looking for two of those at present. One to go in the amp and one spare.
Apart from that, all seems to be working fine and in progress.
Will use it as companion to a Yaesu FT-450D; with a proper soft key circuit of course.
Still have my doubts how the ALC will work or will be adjusted. Have more reading to do.
I do have the original manual.
Comments are welcome.
73
Rob
YS1RS
.
On Mar 12, 2021, at 13:29, Dave Edwards <kd2e@...> wrote:
Where did you source the L75 filter caps from?
.....Dave
On 3/12/21 1:28 PM, Roberto - YS1RS via groups.io wrote:
Recently acquired a Drake L75 for which I am updating its Power Supply to be safe.
A quick question... is the main power switch on the L75 still available?
Was wondering... cause the one on my - older than me - Collins 30L-1 is no longer available. It is a pain just to reach it for service; and is really easier to fill a bottle with parrot saliva than to find one of those.
So, in order to preserve the main switch on my amp, I leave it on all the time and turn it on via an Ameritron In-Rush Current Protection Outlet (ICP-240).
If the story repeats with the Drake L75 amp, then will also take same route like I did with the old Collins.
Stay safe!
Rob
YS1RS
|
Why do you want to take it out of its case?ron W5SUM?
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On Mar 12, 2021, at 8:01 PM, william pinkava via groups.io <wjpinkava@...> wrote:
? I removed mine from the case one time, and hopefully never again. ?It was incredibly tight. ?I mean incredibly tight. ?Good luck to you my friend, 73. ?Bill AE8EA On Mar 12, 2021, at 5:31 PM, MIke Stover <n9qr@...> wrote:
?Picked up an MN-2000 tuner and just got it home.? What's the secret getting it out of the cabinet?? 4 screws on the bottom out BUT the tuner won't budge,? Thanks.
--
Mike Stover N9QR
Fort Wayne, IN
N9QR@...
|
Re: L75 Amp Main Power Switch Availability
The ones I ordered are from NTE electronics.... maybe are not the ones needed for safety....?
Ups
Rob
YS1RS
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On Mar 12, 2021, at 19:36, Jim Shorney <jshorney@...> wrote:
?
Harbach also has them. Not that these are failsafe safety resistors.
73
-Jim
NU0C
On Fri, 12 Mar 2021 17:18:08 -0600
"Roberto - YS1RS via groups.io" <ys1rs@...> wrote:
Yes, found them there.
I just placed a small order of three.
Will take 15 days to come.
Now the sweet waiting with patience.
73 de Rob
YS1RS
On Mar 12, 2021, at 16:23, Dick <w1ksz@...> wrote: ?
Those Resistors are available on e-Bay.
73, Dick, W1KSZ
From: [email protected] <[email protected]> on behalf of Roberto - YS1RS via groups.io <ys1rs@...>
Sent: Friday, March 12, 2021 3:16 PM
To: [email protected] <[email protected]>
Subject: Re: [DRAKE-RADIO] L75 Amp Main Power Switch Availability
Hola Dave and group...
Yes! I've sinned. Don't kick me off the group, please... but availability of parts is not always easy here in YS; specially 2W and higher wattage resistors or high voltage parts for applications found in tube equipment.
I am using modern caps found locally 150uF x 450 VDC x 105 degrees, which thought I was not going to find but was blessed finding them.
Had to modify the boards though. These amps are scarce so no upgrade boards are available for them from commercial sources. All I've done is completely reversible though.
Found one diode burned out and another disolved in my hands so practically replaced them all.
Modern 2 watt resistors went in also, as all the original were high in value - out of tolerance.
Looks like someone else was in here before me, cause one 1/4W resistor that belongs to the meter network was replaced by a 1/2W. All that has now been corrected.
Had problems with the push button meter switches not closing the circuits correctly.
I guess all those years standing there, on storage, without been in use pass the bill, but now has been lubricated and contact cleaner went in to clean contacts and seems to be working as they should.
This amp belonged to a good friend who became SK eight years ago and the amp has been on storage since. I acquired it from his XYL and will be loved and used in my shack.
The only resistor I have not been able to find locally has been R46, the 0.82 ohm x 2 Watt resistor, that acts as a fuse. Too specialized to be found here. It is cracked.
Looking for two of those at present. One to go in the amp and one spare.
Apart from that, all seems to be working fine and in progress.
Will use it as companion to a Yaesu FT-450D; with a proper soft key circuit of course.
Still have my doubts how the ALC will work or will be adjusted. Have more reading to do.
I do have the original manual.
Comments are welcome.
73
Rob
YS1RS
.
On Mar 12, 2021, at 13:29, Dave Edwards <kd2e@...> wrote:
Where did you source the L75 filter caps from?
.....Dave
On 3/12/21 1:28 PM, Roberto - YS1RS via groups.io wrote:
Recently acquired a Drake L75 for which I am updating its Power Supply to be safe.
A quick question... is the main power switch on the L75 still available?
Was wondering... cause the one on my - older than me - Collins 30L-1 is no longer available. It is a pain just to reach it for service; and is really easier to fill a bottle with parrot saliva than to find one of those.
So, in order to preserve the main switch on my amp, I leave it on all the time and turn it on via an Ameritron In-Rush Current Protection Outlet (ICP-240).
If the story repeats with the Drake L75 amp, then will also take same route like I did with the old Collins.
Stay safe!
Rob
YS1RS
|
I removed mine from the case one time, and hopefully never again. ?It was incredibly tight. ?I mean incredibly tight. ?Good luck to you my friend, 73. ?Bill AE8EA
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Show quoted text
On Mar 12, 2021, at 5:31 PM, MIke Stover <n9qr@...> wrote:
?Picked up an MN-2000 tuner and just got it home.? What's the secret getting it out of the cabinet?? 4 screws on the bottom out BUT the tuner won't budge,? Thanks.
--
Mike Stover N9QR
Fort Wayne, IN
N9QR@...
|
Gary:
A VK station on this list had some available a couple of years ago. I picked up several and can certainly spare one if you cannot find one anywhere else.
73
Peter
VE7PS
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On 2021-03-12 5:51 p.m., Jim Shorney wrote: Cinch 5AB2. No longer made. Rumor has it that the 5 pin variant is used for some Hammond organ cables. Also found on car stereo wiring harnesses from the 70s and 80s. The fifth pin can be removed to make it a four pin.
73
-Jim
NU0C
On Fri, 12 Mar 2021 16:14:56 -0800
"Gary Moles" <morgannz@...> wrote:
Hi . Can anyone give me the correct Brand/model of the 4-pin plug used to connect the 2B-Q to the 2B.
There seems to be a few similar plugs but of different pin spacing.
Regards
Gary.
ZL2AKI
|
Cinch 5AB2. No longer made. Rumor has it that the 5 pin variant is used for some Hammond organ cables. Also found on car stereo wiring harnesses from the 70s and 80s. The fifth pin can be removed to make it a four pin. 73 -Jim NU0C On Fri, 12 Mar 2021 16:14:56 -0800 "Gary Moles" <morgannz@...> wrote: Hi . Can anyone give me the correct Brand/model of the 4-pin plug used to connect the 2B-Q to the 2B.
There seems to be a few similar plugs but of different pin spacing.
Regards
Gary.
ZL2AKI
|
Re: L75 Amp Main Power Switch Availability
Harbach also has them. Not that these are failsafe safety resistors. 73 -Jim NU0C On Fri, 12 Mar 2021 17:18:08 -0600 "Roberto - YS1RS via groups.io" <ys1rs@...> wrote: Yes, found them there.
I just placed a small order of three.
Will take 15 days to come.
Now the sweet waiting with patience.
73 de Rob
YS1RS
On Mar 12, 2021, at 16:23, Dick <w1ksz@...> wrote:
?
Those Resistors are available on e-Bay.
73, Dick, W1KSZ
From: [email protected] <[email protected]> on behalf of Roberto - YS1RS via groups.io <ys1rs@...>
Sent: Friday, March 12, 2021 3:16 PM
To: [email protected] <[email protected]>
Subject: Re: [DRAKE-RADIO] L75 Amp Main Power Switch Availability
Hola Dave and group...
Yes! I've sinned. Don't kick me off the group, please... but availability of parts is not always easy here in YS; specially 2W and higher wattage resistors or high voltage parts for applications found in tube equipment.
I am using modern caps found locally 150uF x 450 VDC x 105 degrees, which thought I was not going to find but was blessed finding them.
Had to modify the boards though. These amps are scarce so no upgrade boards are available for them from commercial sources. All I've done is completely reversible though.
Found one diode burned out and another disolved in my hands so practically replaced them all.
Modern 2 watt resistors went in also, as all the original were high in value - out of tolerance.
Looks like someone else was in here before me, cause one 1/4W resistor that belongs to the meter network was replaced by a 1/2W. All that has now been corrected.
Had problems with the push button meter switches not closing the circuits correctly.
I guess all those years standing there, on storage, without been in use pass the bill, but now has been lubricated and contact cleaner went in to clean contacts and seems to be working as they should.
This amp belonged to a good friend who became SK eight years ago and the amp has been on storage since. I acquired it from his XYL and will be loved and used in my shack.
The only resistor I have not been able to find locally has been R46, the 0.82 ohm x 2 Watt resistor, that acts as a fuse. Too specialized to be found here. It is cracked.
Looking for two of those at present. One to go in the amp and one spare.
Apart from that, all seems to be working fine and in progress.
Will use it as companion to a Yaesu FT-450D; with a proper soft key circuit of course.
Still have my doubts how the ALC will work or will be adjusted. Have more reading to do.
I do have the original manual.
Comments are welcome.
73
Rob
YS1RS
.
On Mar 12, 2021, at 13:29, Dave Edwards <kd2e@...> wrote:
Where did you source the L75 filter caps from?
.....Dave
On 3/12/21 1:28 PM, Roberto - YS1RS via groups.io wrote:
Recently acquired a Drake L75 for which I am updating its Power Supply to be safe.
A quick question... is the main power switch on the L75 still available?
Was wondering... cause the one on my - older than me - Collins 30L-1 is no longer available. It is a pain just to reach it for service; and is really easier to fill a bottle with parrot saliva than to find one of those.
So, in order to preserve the main switch on my amp, I leave it on all the time and turn it on via an Ameritron In-Rush Current Protection Outlet (ICP-240).
If the story repeats with the Drake L75 amp, then will also take same route like I did with the old Collins.
Stay safe!
Rob
YS1RS
|
Hi . Can anyone give me the correct Brand/model of the 4-pin plug used to connect the 2B-Q to the 2B.
There seems to be a few similar plugs but of different pin spacing.
Regards
Gary.
ZL2AKI
|
Re: L75 Amp Main Power Switch Availability
Yes, found them there.? I just placed a small order of three. Will take 15 days to come. Now the sweet waiting with patience.?
73 de Rob YS1RS?
toggle quoted message
Show quoted text
On Mar 12, 2021, at 16:23, Dick <w1ksz@...> wrote:
?
Those Resistors are available on e-Bay.
73, Dick, W1KSZ
Hola Dave and group...
Yes! I've sinned. Don't kick me off the group, please... but availability of parts is not always easy here in YS; specially 2W and higher wattage resistors or high voltage parts for applications found in tube equipment.
I am using modern caps found locally 150uF x 450 VDC x 105 degrees, which thought I was not going to find but was blessed finding them.
Had to modify the boards though. These amps are scarce so no upgrade boards are available for them from commercial sources. All I've done is completely reversible though.
Found one diode burned out and another disolved in my hands so practically replaced them all.
Modern 2 watt resistors went in also, as all the original were high in value - out of tolerance.
Looks like someone else was in here before me, cause one 1/4W resistor that belongs to the meter network was replaced by a 1/2W. All that has now been corrected.
Had problems with the push button meter switches not closing the circuits correctly.?
I guess all those years standing there, on storage, without been in use pass the bill, but now has been lubricated and contact cleaner went in to clean contacts and seems to be working as they should.?
This amp belonged to a good friend who became SK eight years ago and the amp has been on storage since. I acquired it from his XYL and will be loved and used in my shack.
The only resistor I have not been able to find locally has been R46, the 0.82 ohm x 2 Watt resistor, that acts as a fuse. ?Too specialized to be found here. It is cracked.?
Looking for two of those at present. One to go in the amp and one spare.
Apart from that, all seems to be working fine and in progress.?
Will use it as companion to a Yaesu FT-450D; with a proper soft key circuit of course.
Still have my doubts how the ALC will work or will be adjusted. Have more reading to do.
I do have the original manual.
Comments are welcome.
73
Rob
YS1RS
On Mar 12, 2021, at 13:29, Dave Edwards < kd2e@...> wrote:
Where did you source the L75 filter caps from?
.....Dave
On 3/12/21 1:28 PM, Roberto - YS1RS via wrote:
Recently acquired a Drake L75 for which I am updating its Power Supply to be safe.
A quick question... is the main power switch on the L75 still available?
Was wondering... cause the one on my - older than me - Collins 30L-1 is no longer available. It is a pain just to reach it for service; and is really easier to fill a bottle with parrot saliva than to find one of those.
So, in order to preserve the main switch on my amp, I leave it on all the time and turn it on via an Ameritron In-Rush Current Protection Outlet (ICP-240).
If the story repeats with the Drake L75 amp, then will also take same route like I did with the old Collins.
Stay safe!
Rob
YS1RS
|
Picked up an MN-2000 tuner and just got it home.? What's the secret getting it out of the cabinet?? 4 screws on the bottom out BUT the tuner won't budge,? Thanks.
--
Mike Stover N9QR
Fort Wayne, IN
N9QR@...
|
Re: L75 Amp Main Power Switch Availability
Those Resistors are available on e-Bay.
73, Dick, W1KSZ
toggle quoted message
Show quoted text
Hola Dave and group...
Yes! I've sinned. Don't kick me off the group, please... but availability of parts is not always easy here in YS; specially 2W and higher wattage resistors or high voltage parts for applications found in tube equipment.
I am using modern caps found locally 150uF x 450 VDC x 105 degrees, which thought I was not going to find but was blessed finding them.
Had to modify the boards though. These amps are scarce so no upgrade boards are available for them from commercial sources. All I've done is completely reversible though.
Found one diode burned out and another disolved in my hands so practically replaced them all.
Modern 2 watt resistors went in also, as all the original were high in value - out of tolerance.
Looks like someone else was in here before me, cause one 1/4W resistor that belongs to the meter network was replaced by a 1/2W. All that has now been corrected.
Had problems with the push button meter switches not closing the circuits correctly.?
I guess all those years standing there, on storage, without been in use pass the bill, but now has been lubricated and contact cleaner went in to clean contacts and seems to be working as they should.?
This amp belonged to a good friend who became SK eight years ago and the amp has been on storage since. I acquired it from his XYL and will be loved and used in my shack.
The only resistor I have not been able to find locally has been R46, the 0.82 ohm x 2 Watt resistor, that acts as a fuse. ?Too specialized to be found here. It is cracked.?
Looking for two of those at present. One to go in the amp and one spare.
Apart from that, all seems to be working fine and in progress.?
Will use it as companion to a Yaesu FT-450D; with a proper soft key circuit of course.
Still have my doubts how the ALC will work or will be adjusted. Have more reading to do.
I do have the original manual.
Comments are welcome.
73
Rob
YS1RS
On Mar 12, 2021, at 13:29, Dave Edwards < kd2e@...> wrote:
Where did you source the L75 filter caps from?
.....Dave
On 3/12/21 1:28 PM, Roberto - YS1RS via wrote:
Recently acquired a Drake L75 for which I am updating its Power Supply to be safe.
A quick question... is the main power switch on the L75 still available?
Was wondering... cause the one on my - older than me - Collins 30L-1 is no longer available. It is a pain just to reach it for service; and is really easier to fill a bottle with parrot saliva than to find one of those.
So, in order to preserve the main switch on my amp, I leave it on all the time and turn it on via an Ameritron In-Rush Current Protection Outlet (ICP-240).
If the story repeats with the Drake L75 amp, then will also take same route like I did with the old Collins.
Stay safe!
Rob
YS1RS
|
Re: L75 Amp Main Power Switch Availability
Hola Dave and group... Yes! I've sinned. Don't kick me off the group, please... but availability of parts is not always easy here in YS; specially 2W and higher wattage resistors or high voltage parts for applications found in tube equipment. I am using modern caps found locally 150uF x 450 VDC x 105 degrees, which thought I was not going to find but was blessed finding them. Had to modify the boards though. These amps are scarce so no upgrade boards are available for them from commercial sources. All I've done is completely reversible though.
Found one diode burned out and another disolved in my hands so practically replaced them all. Modern 2 watt resistors went in also, as all the original were high in value - out of tolerance. Looks like someone else was in here before me, cause one 1/4W resistor that belongs to the meter network was replaced by a 1/2W. All that has now been corrected.
Had problems with the push button meter switches not closing the circuits correctly.? I guess all those years standing there, on storage, without been in use pass the bill, but now has been lubricated and contact cleaner went in to clean contacts and seems to be working as they should.? This amp belonged to a good friend who became SK eight years ago and the amp has been on storage since. I acquired it from his XYL and will be loved and used in my shack.
The only resistor I have not been able to find locally has been R46, the 0.82 ohm x 2 Watt resistor, that acts as a fuse. ?Too specialized to be found here. It is cracked.? Looking for two of those at present. One to go in the amp and one spare. Apart from that, all seems to be working fine and in progress.?
Will use it as companion to a Yaesu FT-450D; with a proper soft key circuit of course. Still have my doubts how the ALC will work or will be adjusted. Have more reading to do. I do have the original manual.
Comments are welcome.
73 Rob YS1RS
toggle quoted message
Show quoted text
On Mar 12, 2021, at 13:29, Dave Edwards < kd2e@...> wrote:
Where did you source the L75 filter caps from?
.....Dave
On 3/12/21 1:28 PM, Roberto - YS1RS via
wrote:
Recently
acquired a Drake L75 for which I am updating its Power Supply to
be safe.
A quick question... is the main power switch on the L75 still
available?
Was wondering... cause the one on my - older than me - Collins
30L-1 is no longer available. It is a pain just to reach it for
service; and is really easier to fill a bottle with parrot saliva
than to find one of those.
So, in order to preserve the main switch on my amp, I leave it on
all the time and turn it on via an Ameritron In-Rush Current
Protection Outlet (ICP-240).
If the story repeats with the Drake L75 amp, then will also take
same route like I did with the old Collins.
Stay safe!
Rob
YS1RS
|
Re: L75 Amp Main Power Switch Availability
I leave mine on all the time and use a pair of 25 amp light switches.? 73s Byron AC9PA? 
toggle quoted message
Show quoted text
On Mar 12, 2021, at 12:28 PM, Roberto - YS1RS via groups.io <ys1rs@...> wrote: ?Recently acquired a Drake L75 for which I am updating its Power Supply to be safe.
A quick question... is the main power switch on the L75 still available?
Was wondering... cause the one on my - older than me - Collins 30L-1 is no longer available. It is a pain just to reach it for service; and is really easier to fill a bottle with parrot saliva than to find one of those.
So, in order to preserve the main switch on my amp, I leave it on all the time and turn it on via an Ameritron In-Rush Current Protection Outlet (ICP-240).
If the story repeats with the Drake L75 amp, then will also take same route like I did with the old Collins.
Stay safe!
Rob
YS1RS
|
Re: L75 Amp Main Power Switch Availability
Where did you source the L75 filter caps from?
.....Dave
On 3/12/21 1:28 PM, Roberto - YS1RS via
groups.io wrote:
toggle quoted message
Show quoted text
Recently
acquired a Drake L75 for which I am updating its Power Supply to
be safe.
A quick question... is the main power switch on the L75 still
available?
Was wondering... cause the one on my - older than me - Collins
30L-1 is no longer available. It is a pain just to reach it for
service; and is really easier to fill a bottle with parrot saliva
than to find one of those.
So, in order to preserve the main switch on my amp, I leave it on
all the time and turn it on via an Ameritron In-Rush Current
Protection Outlet (ICP-240).
If the story repeats with the Drake L75 amp, then will also take
same route like I did with the old Collins.
Stay safe!
Rob
YS1RS
|
Re: L75 Amp Main Power Switch Availability
As far as I know they are similarly unobtainable. Your external switch idea is a good one!
Best 73 John K5MO
Recently acquired a Drake L75 for which I am updating its Power Supply to be safe.
A quick question... is the main power switch on the L75 still available?
Was wondering... cause the one on my - older than me - Collins 30L-1 is no longer available. It is a pain just to reach it for service; and is really easier to fill a bottle with parrot saliva than to find one of those.
So, in order to preserve the main switch on my amp, I leave it on all the time and turn it on via an Ameritron In-Rush Current Protection Outlet (ICP-240).
If the story repeats with the Drake L75 amp, then will also take same route like I did with the old Collins.
Stay safe!
Rob
YS1RS
|
The 7805s bolt to the right side wall of the central card cage. Easy to see on some of the nice Internet photos that Google can find. There have not been any thermal problems there. Drake conveniently marked "pin 1" on each connector with a black stripe. Although I do think that the manufacturer's recommended bypass caps on input and output should be added. 73 -Jim NU0C On Fri, 12 Mar 2021 08:23:49 -0800 "James Amos" <jimamos@...> wrote: One other thought about changing out the regulators.? ? 7805's are linear regulators, and the power they dissipate is the forward voltage drop (Vin - Vout) times the output current.? ? ?The? quiescent current is sunk through the regulator ground pin adds power but only represents 72 mW of power, it will stay cool unloaded.? If you can measure this quiescent current and it's around the standard 6mA the part should be OK.? ? ?You mentioned 290mA, so .290 x (12-5) = 2W, I've seen references state that you need a heat sink on a TO-220 above 1.25W.? ?The datasheet for the 7805 shows that 2W is about the MAX power dissipation without a heat sink, but that's probably pretty hot.? ? ?Changing the regulator, won't change the math on how hot the device is going to get if it's operating correctly.
Also, the TI datasheet for their? currently produced 7805 indicates that it has thermal overload protection.? So, if you have 5V on the output, it's still operating within it's allowable temperature range, otherwise it would shut down.? ?But, keep in mind, the maximum operating junction temperature is 125C, which is still hot enough to burn your finger.
73's Jim N8CAH
|
Roberto - YS1RS
Ronnie Hull - W5SUM
MIke Stover
Greg W9GB
Jim Shorney
Dick