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Hi,
I own a Drake L7 received from a silent key. The L7 seems to be in a very good condition from optical inspection. I am unsure if the tubes are in a good condition considering power output (Eimac 3-500Z).
The manual of the l7 says 1kW input on CW. So, what HF output should I measure on tuned amplifier?
On 20m connected to a dummy load, I measure 600W on the L7 meter and approx 480W on a Power meter connected in between to the DL. The HV drops from 1880V idle to 1500V load.
This calculates to approx. 50% efficiency in CW mode. From literature readings, Class B amplifier should have up to 80% efficiency ...
Should I expect a higher efficiency? Is 380V HV drop ok or should I check the capacitance of the filter caps?
Maybe an expierenced OM could give me some explaination.
Regards, Johann
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Hi Johann,?
I have an L-4B which is electrically similar to the L-7 (and uses the same power supply)
50-60% efficiency is not all that uncommon for? L-4/L7 amplifiers.? (or any 3-500 Class AB amp) 75+% can be expected with Class C amps though.
Eimac indicates about 330W output (single tube) @1500V and 400mA.... so around 600W for a pair wouldn't be totally out of line.
Depending on how well calibrated your "Power Meter" is, and if it is not , you're basically using 2 unknown wattmeters for measurement.........? You may not have any problem at all!
How much power are you getting when tuning in the SSB "mode"? (I get about 1200-1300w running the amp on 240VAC line voltage)? Measured with a Bird 43 wattmeter and 2500W "slug" and verified with an Array Solutions Power Master II
That CW/TUNE mode was included because Drake needed to provide a plate voltage that wouldn't exceed 1000W power input when that was the limit for US amateurs.? It's really not needed anymore.? I stopped using the "CW/TUNE" voltage selection long ago.? And when I clean up my power switch and install a solid state relay to protect it, I'll probably permanently bypass the switch wire it for "SSB"
Bottom line, get another watt meter to verify your outboard meter and try tuning it in the SSB position.
You're likely going to get infinite opinions on all this.?
-
73/Rick
W4XA
*Every post is created using Linux
|
Personally I like having the low power switch. You have less inrush current at power on (regardless of whether or not you have a soft start installed) and it is easier on the tubes for initial tune-up and when testing an amp. 73 -Jim NU0C On Mon, 04 Mar 2024 07:55:00 -0800 "Rick W4XA" <myr748@...> wrote: Hi Johann,
I have an L-4B which is electrically similar to the L-7 (and uses the same power supply)
50-60% efficiency is not all that uncommon for? L-4/L7 amplifiers.? (or any 3-500 Class AB amp) 75+% can be expected with Class C amps though.
Eimac indicates about 330W output (single tube) @1500V and 400mA.... so around 600W for a pair wouldn't be totally out of line.
Depending on how well calibrated your "Power Meter" is, and if it is not , you're basically using 2 unknown wattmeters for measurement.........? You may not have any problem at all!
How much power are you getting when tuning in the SSB "mode"? (I get about 1200-1300w running the amp on 240VAC line voltage)? Measured with a Bird 43 wattmeter and 2500W "slug" and verified with an Array Solutions Power Master II
That CW/TUNE mode was included because Drake needed to provide a plate voltage that wouldn't exceed 1000W power input when that was the limit for US amateurs.? It's really not needed anymore.? I stopped using the "CW/TUNE" voltage selection long ago.? And when I clean up my power switch and install a solid state relay to protect it, I'll probably permanently bypass the switch wire it for "SSB"
Bottom line, get another watt meter to verify your outboard meter and try tuning it in the SSB position.
You're likely going to get infinite opinions on all this.
-
*73/Rick* *W4XA
* * Every post is created using Linux *
*
-- 73 -Jim NU0C
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Some things to know/ realize:
With new tubes and the plate voltage on the high setting and with a reasonable dummy or antenna load, you will easily get 1200 Watts.
It is typical that the higher frequencies are lower output power.? This is also a useful, broad based measure of your tubes.? Aged tubes have less power on the higher frequencies.? Tubes that are new and presently available?are, in my opinion, generally of poorer quality that the originally used and intended tubes.
Your watt meter?needs to be?calibrated to a known stable standard if your mode of effectiveness is output?power measurement.
There is very little difference between 1000 watts and 800 watts or less on the other end.? Having a signal at the other end of 10 over S9 is just as effective for a normal qso as S9.? Striving for full max on every tune up will have you also buying new tubes more often.? I run mine no more than 800 watts because I do not need to go higher?to make and hold a qso.??
Use the lower?plate voltage/power setting of the?initial?tune up.? If that power is ok for your purposes, no need to go higher.? But if you then need more, go to the higher plate voltage setting and do a slight adjustment on the tuning.
The L7 is a good amplifier.? Care for it and your tubes and you should have good service.
Good luck.
David Assaf III W5XU, VP8RXU ?
Hi,
I own a Drake L7 received from a silent key. The L7 seems to be in a very good condition from optical inspection. I am unsure if the tubes are in a good condition considering power output (Eimac 3-500Z).
The manual of the l7 says 1kW input on CW. So, what HF output should I measure on tuned amplifier?
On 20m connected to a dummy load, I measure 600W on the L7 meter and approx 480W on a Power meter connected in between to the DL. The HV drops from 1880V idle to 1500V load.
This calculates to approx. 50% efficiency in CW mode. From literature readings, Class B amplifier should have up to 80% efficiency ...
Should I expect a higher efficiency? Is 380V HV drop ok or should I check the capacitance of the filter caps?
Maybe an expierenced OM could give me some explaination.
Regards, Johann
|
True statement Jim! Some sort of protection is definitely needed to prevent arcing the power switch on "make" (or break) ? I'm using a solid state relay to completely eliminate stress on the "un-obtanium" switch .? (I also put one in my AC-4 too....no more thumps or bangs inside the AC-4,? nor sparks inside the T-4XC switch)   3-500's are good up to 4000V.? I'm thinking that 2700V probably won't? "hurt" them. And when tuning for maximum output, the tubes should be tuned at the voltage and (max) current they'll be drawing at peak for lowest grid current and best linearity.??? Grid current is also a little lower at the at the higher voltages.? Drake only did the "tune" position to meet the FCC max power (single-tone/CW 1KW input)? of the time. If you want to be "easy" on the amp, just drive it to a lower power output. (lower drive = lower grid/plate current and output) I am re-building the power supply for my Hallicrafters HT-45 Loudenboomer (single 3-400) using a plate transformer out of a Drake L-4PS. ? ? It'll get the same SSR and won't be wired for switchable plate voltage.
On Mon, Mar 4, 2024 at 10:39 AM, Jim Shorney wrote:
Personally I like having the low power switch. You have less inrush current at power on (regardless of whether or not you have a soft start installed) and it is easier on the tubes for initial tune-up and when testing an amp.
73
-Jim
NU0C
--
73/Rick
W4XA
*Every post is created using Linux
|
Rick W4XA writes: I am re-building the power supply for my Hallicrafters HT-45 Loudenboomer (=
single 3-400) using a plate transformer out of a Drake L-4PS. =C2=A0 =C2=A0=
It'll get the same SSR and won't be wired for switchable plate voltage. Oh do tell! I have a Loudenboomer here pining to meet a suitable PSU. I had thought about trying to replicate the original PSU (I even have the 866s!), but re-purposing an existing HV supply is probably the more relistic solution. I would be very curious to see what you come up with. --lyndon
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I would be interested in one of these for my L4 any suggestions?
Mike W8flt
Thanks in advance
toggle quoted message
Show quoted text
On Mar 4, 2024, at 9:29?PM, Lyndon VE7TFX <lyndon@...> wrote:
?Rick W4XA writes:
I am re-building the power supply for my Hallicrafters HT-45 Loudenboomer (=
single 3-400) using a plate transformer out of a Drake L-4PS. =C2=A0 =C2=A0=
It'll get the same SSR and won't be wired for switchable plate voltage. Oh do tell! I have a Loudenboomer here pining to meet a suitable
PSU. I had thought about trying to replicate the original PSU (I
even have the 866s!), but re-purposing an existing HV supply is
probably the more relistic solution. I would be very curious to
see what you come up with.
--lyndon
|
On Mon, Mar 4, 2024 at 07:56 PM, Michael J Trussell wrote:
I would be interested in one of these for my L4 any suggestions?
Mike W8flt
Thanks in advance
If you're talking about an SSR for the L-4, here's an example of a "How-to" http://www.w8zr.net/vintage/amplifiers/Drake%20L4B%20Modification/Drake%20L-4B%20Modification.htm --
73/Rick
W4XA
*Every post is created using Linux
|
Lyndon.....you have an HT-45 too!? ? Mine is operational?with the original PS, but needs a decent T/R relay setup. I have it positioned to use with my Kenwood hybrid?gear.? I need to get the T/R setup this summer.
73 Peter VE7PS
On Mon, Mar 4, 2024 at 6:29?PM Lyndon VE7TFX < lyndon@...> wrote: Rick W4XA writes:
> I am re-building the power supply for my Hallicrafters HT-45 Loudenboomer (=
> single 3-400) using a plate transformer out of a Drake L-4PS. =C2=A0 =C2=A0=
>? It'll get the same SSR and won't be wired for switchable plate voltage.
Oh do tell!? I have a Loudenboomer here pining to meet a suitable
PSU.? I had thought about trying to replicate the original PSU (I
even have the 866s!), but re-purposing an existing HV supply is
probably the more relistic solution.? I would be very curious to
see what you come up with.
--lyndon
|
I was seeing a little arcing from the power switch contacts and installed the SSR with perfect results.? I could tell there was a little arc because the lightning detector on my weather station, only a few feet from the amp, would give me a false positive everytime i turned on the amp. Given the difficulty of finding replacement switches and rebuild kits for the switch, its a nice solution,
73 Jim, W4UCK
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That is a particularly nice implementation. I'll do this when I get my L7 out of service.
Great writeup too.
John K5MO
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Let me? make sure I have this correct. I have two L7's and one L4B. Am I right that everyone is stating to tune these amps in the SSB position and just leave the amp in the SSB position all the time?
Also what about running digital modes I use the tune position for that but perhaps I should be using the SSB position. Please advise on both situations and many thanks.
73 Tim
WB8UHZ
On Tuesday, March 5, 2024 at 08:19:02 AM EST, John K5MO <johnk5mo@...> wrote:
That is a particularly nice implementation. I'll do this when I get my L7 out of service.
Great writeup too.
John K5MO
|
Tim, the sole reason for the CW position, at the time of manufacture, was to keep within the power regulations that were in place, in the USA, at the time. ?The limitation was 1000 watts input power, which was obtained on CW by multiplying the plate voltage by the plate current. It was acceptable then to estimate the power input for SSB, since there was no easy way to measure PEP.
Having said all of that, I do consider the CW position to be useful for digital modes, as it limits the power out to a safe level for the amp. When I use the amp (rarely) for digital modes, I keep my output at around 500 - 600W. ?On CW, I use the amp on the ¡°SSB¡± position to get max power out, which is around 1200W if you keep the grid current within the tube ratings.
Steve Wedge, W1ES/4
Time flies like an arrow. Fruit flies like a banana.
On Tue, Mar 5, 2024 at 9:29 AM, amfone via groups.io < amfone20000@...> wrote:
Let me? make sure I have this correct. I have two L7's and one L4B. Am I right that everyone is stating to tune these amps in the SSB position and just leave the amp in the SSB position all the time?
Also what about running digital modes I use the tune position for that but perhaps I should be using the SSB position. Please advise on both situations and many thanks.
73 Tim
WB8UHZ
On Tuesday, March 5, 2024 at 08:19:02 AM EST, John K5MO <johnk5mo@...> wrote:
That is a particularly nice implementation. I'll do this when I get my L7 out of service.
Great writeup too.
John K5MO
|
From what I have read the plate circuit will be slightly more efficient if you use the CW position if you only want to run around 500 or so watts instead of the full power.??
It is true that when the FCC went by input power the legal way was to tune up in the CW position to 1 kw input and then switch to SSB position if you wanted to run the amp to the 2 kw pep level.? Not needed now as the limit is 1500 watts output.
I use an external switch with a current limit resistor and relay for a 'soft start' and leave the amp switch on all the time.
?A while back there were several people putting out a rebuild kit for the power switch and I bought one but have not needed it.
Ralph ku4pt
On Tuesday, March 5, 2024 at 10:01:46 AM EST, Steve Wedge, W1ES/4 via groups.io <w1es@...> wrote:
Tim, the sole reason for the CW position, at the time of manufacture, was to keep within the power regulations that were in place, in the USA, at the time. ?The limitation was 1000 watts input power, which was obtained on CW by multiplying the plate voltage by the plate current. It was acceptable then to estimate the power input for SSB, since there was no easy way to measure PEP.
Having said all of that, I do consider the CW position to be useful for digital modes, as it limits the power out to a safe level for the amp. When I use the amp (rarely) for digital modes, I keep my output at around 500 - 600W. ?On CW, I use the amp on the ¡°SSB¡± position to get max power out, which is around 1200W if you keep the grid current within the tube ratings.
Steve Wedge, W1ES/4
Time flies like an arrow. Fruit flies like a banana.
_,_
|
? Steve and Ralph thanks very much for the information, much appreciated.
Tim
On Tuesday, March 5, 2024 at 10:14:05 AM EST, Ralph Mowery via groups.io <ku4pt@...> wrote:
From what I have read the plate circuit will be slightly more efficient if you use the CW position if you only want to run around 500 or so watts instead of the full power.??
It is true that when the FCC went by input power the legal way was to tune up in the CW position to 1 kw input and then switch to SSB position if you wanted to run the amp to the 2 kw pep level.? Not needed now as the limit is 1500 watts output.
I use an external switch with a current limit resistor and relay for a 'soft start' and leave the amp switch on all the time.
?A while back there were several people putting out a rebuild kit for the power switch and I bought one but have not needed it.
Ralph ku4pt
On Tuesday, March 5, 2024 at 10:01:46 AM EST, Steve Wedge, W1ES/4 via groups.io <w1es@...> wrote:
Tim, the sole reason for the CW position, at the time of manufacture, was to keep within the power regulations that were in place, in the USA, at the time. ?The limitation was 1000 watts input power, which was obtained on CW by multiplying the plate voltage by the plate current. It was acceptable then to estimate the power input for SSB, since there was no easy way to measure PEP.
Having said all of that, I do consider the CW position to be useful for digital modes, as it limits the power out to a safe level for the amp. When I use the amp (rarely) for digital modes, I keep my output at around 500 - 600W. ?On CW, I use the amp on the ¡°SSB¡± position to get max power out, which is around 1200W if you keep the grid current within the tube ratings.
Steve Wedge, W1ES/4
Time flies like an arrow. Fruit flies like a banana.
_,_
|
On Tue, Mar 5, 2024 at 03:50 AM, Jim Altman wrote:
I was seeing a little arcing from the power switch contacts and installed the SSR with perfect results.? I could tell there was a little arc because the lightning detector on my weather station, only a few feet from the amp, would give me a false positive everytime i turned on the amp. Given the difficulty of finding replacement switches and rebuild kits for the switch, its a nice solution,
73 Jim, W4UCK
Yeah, you only see that "arc" if the switch is closed (or opened) while the voltage is at a peak (sine wave peak) If you have ever plugged (or unplugged) in any device that's "ON" when you plug it in and have noticed a little spark, flipped a light switch on or off and heard the faint "snap" it likely happened at or near the sine wave peak (positive or negative) and of course,? you do not see that spark or hear it every time. The trick is to "flip" the switch when the voltage is crossing at or near zero.? Now maybe there are people that can "see" the sine wave in their heads and are fast enough to flip the switch at the right time,?? and won't need a little additional help getting the timing right. For the rest of us, an SSR does it nicely. W8ZR suggested using only one but you can use 2 when powering with 240AC.? (have a look at the )? page 16 You also do not have to use the DC controlled model either.? (Commander 2500 uses AC SSR's)? I am going to use the AC controlled model eliminating the need for a separate (always powered) small DC power supply? Either way, the control "side" of the SSR draws so little current as to be insignificant. I'll be operating my Loudenboomer (powered by the L-4B plate transformer) on 120AC and always in the "high-voltage" mode. (240 is really not required for a 1kw input amp)? so I'll use one? OPTO22 Model 120A25 in the"hot" side. For a 240 VAC powered amp, I would use two 240A45 (AC controlled) or? 240D45 (DC controlled) units. See the link below for specs:?
The key with these is that? they "turn-on" at zero crossing (zero voltage) and give a slight measure of ramp-up in voltage.
I seem to remember that Tom, W8JI said the only reason "step-start" is needed, is to protect the ON/OFF switch.? with an SSR, the voltage on the PS circuits doesn't "slam" on it ramps up at a "sine-wave rate".? The actual current in the SSR control circuit is on the order of mA.
See page 2 of the above publication for the features. I'm also using a CRYDOM MPDCD3 DC SSR for a keying interface to use with my IC-705 (similar to the OPTO22 DC60MP)? with a double 3v lithium battery holder for complete isolation to protect the IC-705 keying circuit? driving any amplifier. All the SSR's I have bought so far I have gotten from eBay.? All used.? If you buy them new, they're crazy expensive but there's nothing wrong with used ones.? They either work or they don't. BE VERY Careful buying the cheap knock-off SSR's.? They frequently have triacs inside that are not rated for the claimed current on the outside of the device.? And if you're going to run them at or near max current ratings, ABSOLUTELY MIND THE HEAT DISSIPATION!! I'm using a 120V 25A device on my Loudenboomer and will use two 240v 45A devices in my L-4B (The L-4B even at Key-DOWN 1200 W output doesn't pop a 15A breaker.? Mounting to the chassis will likely be more than enough heat sink in the L-4B Even after many hours the one I mounted in my AC-4 gets only slightly warm using the chassis as a heat sink (I used a little heat grease too) I do have a small heat sink that I'll probably use in the Loudenboomer. --
73/Rick
W4XA
*Every post is created using Linux
|
No, NOT everyone is saying this. Always use CW mode when powering up and during initial tune up when changing bands. After that, do final tuning to the maximum power level that you expect to operate. Note that some advise to always tune up to the full 1200-ish watts output to mitigate possible "accidents" that can be damaging to the amp. 73 -Jim NU0C On Tue, 5 Mar 2024 14:29:15 +0000 (UTC) "amfone via groups.io" <amfone20000@...> wrote: Let me? make sure I have this correct. I have two L7's and one L4B. Am I right that everyone is stating to tune these amps in the SSB position and just leave the amp in the SSB position all the time?
Also what about running digital modes I use the tune position for that but perhaps I should be using the SSB position. Please advise on both situations and many thanks.
73 Tim
WB8UHZ
On Tuesday, March 5, 2024 at 08:19:02 AM EST, John K5MO <johnk5mo@...> wrote:
That is a particularly nice implementation. I'll do this when I get my L7 out of service.
Great writeup too.
John K5MO
-- 73 -Jim NU0C
|
Thanks Jim for your input. I purchased my first L7 new in 1978, for years even on SSB I ran in the low voltage tune mode, only lately have I used the SSB mode when using that mode only, I always tune in the CW position or LV mode, then I will peak the amp as Drake notes using a watt meter.
I normally tune for about 500 watts on the meter, this is below of course the ratings for the tube noted by Drake in the manual. If I run AM phone with the amp using a modern rig I will have a carrier output of not more that 125 watts, running digital, mostly Olivia, when I use the amp I will run about 110 watts, all in the LV/CW position or position on the amp.
Running at the lower voltage will raise the grid current a little but you just need to keep an eye on it.
73 and thanks again.
Tim
WB8UHZ
On Tuesday, March 5, 2024 at 02:06:44 PM EST, Jim Shorney <jimnu0c@...> wrote:
No, NOT everyone is saying this. Always use CW mode when powering up and during initial tune up when changing bands. After that, do final tuning to the maximum power level that you expect to operate. Note that some advise to always tune up to the full 1200-ish watts output to mitigate possible "accidents" that can be damaging to the amp.
73
-Jim
NU0C
On Tue, 5 Mar 2024 14:29:15 +0000 (UTC) "amfone via groups.io" <amfone20000@...> wrote: >? Let me? make sure I have this correct. I have two L7's and one L4B. Am I right that everyone is stating to tune these amps in the SSB position and just leave the amp in the SSB position all the time? > > Also what about running digital modes I use the tune position for that but perhaps I should be using the SSB position. Please advise on both situations and many thanks. > 73 Tim > WB8UHZ > >? ? On Tuesday, March 5, 2024 at 08:19:02 AM EST, John K5MO < johnk5mo@...> wrote:? >? >? That is a particularly nice implementation. I'll do this when I get my L7 out of service. > Great writeup too. > John K5MO >? > > > > > -- 73 -Jim NU0C
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I've run my amps at a kilowatt out on CW (with SSB plate voltage of course) with no issues. Digital modes, well, depends on your TX time. Short contest bursts you could probably do at 1 KW. They will tolerate FT8 at not more than 700 Watts, and in fact that is a good way of getting red in the plates of classic 3-500s to activate the getter material. Back in the pre-FT days I used to run JT65 at about the same level. W8JI has some great articles on amps at his web site, if you haven't been there yet. 73 -Jim NU0C On Tue, 5 Mar 2024 19:21:55 +0000 (UTC) "amfone via groups.io" <amfone20000@...> wrote: Thanks Jim for your input. I purchased my first L7 new in 1978, for years even on SSB I ran in the low voltage tune mode, only lately have I used the SSB mode when using that mode only, I always tune in the CW position or LV mode, then I will peak the amp as Drake notes using a watt meter.
I normally tune for about 500 watts on the meter, this is below of course the ratings for the tube noted by Drake in the manual. If I run AM phone with the amp using a modern rig I will have a carrier output of not more that 125 watts, running digital, mostly Olivia, when I use the amp I will run about 110 watts, all in the LV/CW position or position on the amp.
Running at the lower voltage will raise the grid current a little but you just need to keep an eye on it.
73 and thanks again.
Tim
WB8UHZ
On Tuesday, March 5, 2024 at 02:06:44 PM EST, Jim Shorney <jimnu0c@...> wrote:
No, NOT everyone is saying this. Always use CW mode when powering up and during initial tune up when changing bands. After that, do final tuning to the maximum power level that you expect to operate. Note that some advise to always tune up to the full 1200-ish watts output to mitigate possible "accidents" that can be damaging to the amp.
73
-Jim
NU0C
On Tue, 5 Mar 2024 14:29:15 +0000 (UTC)
"amfone via groups.io" <amfone20000@...> wrote:
? Let me? make sure I have this correct. I have two L7's and one L4B. Am I right that everyone is stating to tune these amps in the SSB position and just leave the amp in the SSB position all the time?
Also what about running digital modes I use the tune position for that but perhaps I should be using the SSB position. Please advise on both situations and many thanks.
73 Tim
WB8UHZ
? ? On Tuesday, March 5, 2024 at 08:19:02 AM EST, John K5MO <johnk5mo@...> wrote:?
?
? That is a particularly nice implementation. I'll do this when I get my L7 out of service.
Great writeup too.
John K5MO
?
-- 73 -Jim NU0C
|
I have read that the power switches on the R4 series
transmitters and receivers are also hard to find and/or expensive. If so, is
there any benefit to installing some type of surge current reduction on these
units to extend their life, or is the failure mechanism mostly a mechanical
issue?
Bill N0CU
On Tue, Mar 5, 2024 at 11:58?AM Rick W4XA < myr748@...> wrote: On Tue, Mar 5, 2024 at 03:50 AM, Jim Altman wrote:
I was seeing a little arcing from the power switch contacts and installed the SSR with perfect results.? I could tell there was a little arc because the lightning detector on my weather station, only a few feet from the amp, would give me a false positive everytime i turned on the amp. Given the difficulty of finding replacement switches and rebuild kits for the switch, its a nice solution,
73 Jim, W4UCK
Yeah, you only see that "arc" if the switch is closed (or opened) while the voltage is at a peak (sine wave peak)
If you have ever plugged (or unplugged) in any device that's "ON" when you plug it in and have noticed a little spark, flipped a light switch on or off and heard the faint "snap" it likely happened at or near the sine wave peak (positive or negative) and of course,? you do not see that spark or hear it every time.
The trick is to "flip" the switch when the voltage is crossing at or near zero.?
Now maybe there are people that can "see" the sine wave in their heads and are fast enough to flip the switch at the right time,?? and won't need a little additional help getting the timing right.
For the rest of us, an SSR does it nicely.
W8ZR suggested using only one but you can use 2 when powering with 240AC.? (have a look at the )? page 16
You also do not have to use the DC controlled model either.? (Commander 2500 uses AC SSR's)? I am going to use the AC controlled model eliminating the need for a separate (always powered) small DC power supply? Either way, the control "side" of the SSR draws so little current as to be insignificant.
I'll be operating my Loudenboomer (powered by the L-4B plate transformer) on 120AC and always in the "high-voltage" mode. (240 is really not required for a 1kw input amp)? so I'll use one? OPTO22 Model 120A25 in the"hot" side.
For a 240 VAC powered amp, I would use two 240A45 (AC controlled) or? 240D45 (DC controlled) units.
See the link below for specs:?
The key with these is that? they "turn-on" at zero crossing (zero voltage) and give a slight measure of ramp-up in voltage.
I seem to remember that Tom, W8JI said the only reason "step-start" is needed, is to protect the ON/OFF switch.? with an SSR, the voltage on the PS circuits doesn't "slam" on it ramps up at a "sine-wave rate".? The actual current in the SSR control circuit is on the order of mA.
See page 2 of the above publication for the features.
I'm also using a CRYDOM MPDCD3 DC SSR for a keying interface to use with my IC-705 (similar to the OPTO22 DC60MP)? with a double 3v lithium battery holder for complete isolation to protect the IC-705 keying circuit? driving any amplifier.
All the SSR's I have bought so far I have gotten from eBay.? All used.? If you buy them new, they're crazy expensive but there's nothing wrong with used ones.? They either work or they don't.
BE VERY Careful buying the cheap knock-off SSR's.? They frequently have triacs inside that are not rated for the claimed current on the outside of the device.? And if you're going to run them at or near max current ratings, ABSOLUTELY MIND THE HEAT DISSIPATION!!
I'm using a 120V 25A device on my Loudenboomer and will use two 240v 45A devices in my L-4B (The L-4B even at Key-DOWN 1200 W output doesn't pop a 15A breaker.? Mounting to the chassis will likely be more than enough heat sink in the L-4B
Even after many hours the one I mounted in my AC-4 gets only slightly warm using the chassis as a heat sink (I used a little heat grease too)
I do have a small heat sink that I'll probably use in the Loudenboomer.
--
73/Rick
W4XA
*Every post is created using Linux
|
Jim Shorney
David