|
Amazing the 7300 has this rail end RF issue. ?Seems like Icom has be plagued with with these RF issues either on make or break. ?I recall a friend had an Icom 781 and. alpha 86a or 9500 and he was a CW contester. ?The leading edge spike would fault the amplifier very often. ?He raised hell with Icombut they didn’t offer a fix. ?Seems like the 7300 had the opposite problem.
On Sunday, August 4, 2024, 8:23 AM, Jim VE7RF <jim.thom@...> wrote: On Fri, Aug 2, 2024 at 06:37 PM, Louis Parascondola wrote:
A 7300 or just about ANY solid state radio without RF delay control will hot switch an SB200,SB220,TL922, Drake etc etc unless the modern radio has an RF delay, the? amp will hot ?switch. ?In?the case of the old open frame relay amps, the TR relay can be mechanically sequenced so that the contacts won’t hot switch by insuring that the output contacts switch?before the amplifier is biased on with the bias switching contact of the relay. The 7300 isn’t necessarily singled out on this regard. ?Use a 20ms RF delay when using old amps with new radios.
##? Lou, even if u tweaked the output contacts of the old style clunker 3PDT mech relays such that the output closed before the input+ bias,? it will still hotswitch !? The xcvr puts out RF? NOW.? ?Hence the requirement for the 20 msec delay....so the slow 3PDT TR relay in the amp gets a 20 msec? head start. ##? There is no provision in my fT-1000D for any delay.
##? On my MK-V, there is an adjustable 0-30 msec delay, in 1 msec increments.... BUT that only works on cw mode, using the internal keyer.?
##? My....'fix' for that ( ssb on either xcvr....and CW + SSB on a FT-1000D)? was to RE-use the internal spst mech relay in each xcvr (that was intended to key an amp)..and instead use the internal xcvr spst relay to instead grnd the TX inhibit lead.? ? That tiny spst relay in the MK-V operates in 5 msecs...which is ample for my modified drake amps, since the 3 x sped up vac relays in the drake amps operate in 1 msec.?
##? The oem 3pdt relay in the drake amps operate in 17 msecs.? And 15 msecs in the older ameritron amps.? (The ameritron amps with the newer cube relays operate in 5 msecs. ).? ? ?So the advice of using a 20 msec delay when using the older amps with the slow relays is valid.??
##? here is where I screwed up.? ?You want the 3-20 msec delay when going from RX to TX...... (grnding the TX inhibit lead after 3-20 msecs. )? However, when going from TX back to RX, you want zero delay, or close to zero.?
Here's why. If a say 20 msec delay is used going from RX to TX, fine...... but when going back to RX.....and it takes the same 20 msecs to UN ground the TX inhibit lead.... what happens is..... stop talking on SSB, zero watts out of xcvr on the scope...... and 400 msecs later..... VOX drops out.......(and tiny spst relay in the xcvr starts to drop out, or any external delay)....then? TR relays in the amp also start to drop out. With TR relays in mid air, cough into the mic, and bam, instant RF coming out of the xcvr.....since the TX inhibit lead is STILL grnded.? ?TR relays in mid air = hot switching.
##? It works on my sped up vac relays in the drake amps? since the tiny SPST-NO? relay in the MK-V takes 5 msecs to operate (giving the 1 msec vac relays in the drake amp, ample head start) . Going back to RX, the tiny relay in the MK-V takes 1 msec to open off by .0001"...so the tx inhibit lead is UN grounded asap.... before the vac relays start to rls. ( I slow down the rls of all 3 x vac relays a bit, with a single rvs diode across each coil).?
## On buddy's hb 3x6 amp? (built back in 2007)? it used an external electronic delay...to grnd the TX inhibit lead.? ? Think it was set for 5-10 msecs. What I don't remember is ..what the rls time of it was.?
|
On Fri, Aug 2, 2024 at 06:37 PM, Louis Parascondola wrote:
A 7300 or just about ANY solid state radio without RF delay control will hot switch an SB200,SB220,TL922, Drake etc etc unless the modern radio has an RF delay, the? amp will hot ?switch. ?In?the case of the old open frame relay amps, the TR relay can be mechanically sequenced so that the contacts won’t hot switch by insuring that the output contacts switch?before the amplifier is biased on with the bias switching contact of the relay. The 7300 isn’t necessarily singled out on this regard. ?Use a 20ms RF delay when using old amps with new radios.
##? Lou, even if u tweaked the output contacts of the old style clunker 3PDT mech relays such that the output closed before the input+ bias,? it will still hotswitch !? The xcvr puts out RF? NOW.? ?Hence the requirement for the 20 msec delay....so the slow 3PDT TR relay in the amp gets a 20 msec? head start. ##? There is no provision in my fT-1000D for any delay.
##? On my MK-V, there is an adjustable 0-30 msec delay, in 1 msec increments.... BUT that only works on cw mode, using the internal keyer.?
##? My....'fix' for that ( ssb on either xcvr....and CW + SSB on a FT-1000D)? was to RE-use the internal spst mech relay in each xcvr (that was intended to key an amp)..and instead use the internal xcvr spst relay to instead grnd the TX inhibit lead.? ? That tiny spst relay in the MK-V operates in 5 msecs...which is ample for my modified drake amps, since the 3 x sped up vac relays in the drake amps operate in 1 msec.?
##? The oem 3pdt relay in the drake amps operate in 17 msecs.? And 15 msecs in the older ameritron amps.? (The ameritron amps with the newer cube relays operate in 5 msecs. ).? ? ?So the advice of using a 20 msec delay when using the older amps with the slow relays is valid.??
##? here is where I screwed up.? ?You want the 3-20 msec delay when going from RX to TX...... (grnding the TX inhibit lead after 3-20 msecs. )? However, when going from TX back to RX, you want zero delay, or close to zero.?
Here's why. If a say 20 msec delay is used going from RX to TX, fine...... but when going back to RX.....and it takes the same 20 msecs to UN ground the TX inhibit lead.... what happens is..... stop talking on SSB, zero watts out of xcvr on the scope...... and 400 msecs later..... VOX drops out.......(and tiny spst relay in the xcvr starts to drop out, or any external delay)....then? TR relays in the amp also start to drop out. With TR relays in mid air, cough into the mic, and bam, instant RF coming out of the xcvr.....since the TX inhibit lead is STILL grnded.? ?TR relays in mid air = hot switching.
##? It works on my sped up vac relays in the drake amps? since the tiny SPST-NO? relay in the MK-V takes 5 msecs to operate (giving the 1 msec vac relays in the drake amp, ample head start) . Going back to RX, the tiny relay in the MK-V takes 1 msec to open off by .0001"...so the tx inhibit lead is UN grounded asap.... before the vac relays start to rls. ( I slow down the rls of all 3 x vac relays a bit, with a single rvs diode across each coil).?
## On buddy's hb 3x6 amp? (built back in 2007)? it used an external electronic delay...to grnd the TX inhibit lead.? ? Think it was set for 5-10 msecs. What I don't remember is ..what the rls time of it was.?
|
"This article is concerned with the RF output continuing beyond the time the transmitter is keyed off, termed an
RF-tail, causing hot-switching of external linear amplifier.)
Unfortunately, there is no similar user adjustable menu setting for controlling the delay time from when the transmitter ceases RF output
and the SEND jack commands an external amplifier off. Because the IC-7300 continues to output RF energy while an external amplifier
is in the process of switching off, the amplifier's TR/RX relay is subject to hot-switching and the concomitant possibility of arcing at the
relay contact points, or worse yet, welding together of those points resulting in the amplifier taken out of service."
Lou, this is the issue with the stupid 7300? xcvr.? ?It keeps putting out RF....AFTER? it opens the key line....and amp switching back to RX.....which then hot switches the TR relays in the amp.??
The alpha amps will not RLS their TR relays, until NO RF appears on the input.? ?The alpha amps have a simple RF sense circuit on their input (which also reads the freq, if it's the 9500 auto tune).
The W7RY? qsk board does the same thing.....( RF sense on input).? ?IF u say run a 1.5 kw cxr on the alpha....and reach over and pull out the key line from the back of the xcvr ( or pull out from the back of the alpha amp)...then amp will still put out 1.5 kw...... until the ptt /footswitch is released..... or if you let go of the hand key.? And if it's a 7300...with it's .....'RF tail', the alpha will not UN key it's TR relay/pin diodes on older alpha amps like the 87A...until the RF tail has finally gone.??
This is also an issue when using high swr shut down circuits, like in the array solutions powermaster wattmeter.? With the high swr threshold exceeded, you have 3 x ways to shut down the amp asap.?
(1)? open off keyline ( doesn't work on alpha amps)
(2) apply a few volts of DC? to the xcvr's ALC input? ( this method works superb)
(3) open off the xcvr's? .....'TX inhibit lead'? ?This method is the fastest if using the array solutions power master wattmeter.
The AS meter uses a SPDT fast relay to achieve any if the 3 x configs above.? ?Takes 4 msecs to get the COM contact to physically move from the NC contact over to the NO contact....(for? #2...applying a few volts to the alc jack of xcvr).??
However, when simply opening of the normally grnded? TX inhibit lead, the COM only has to move .0001" away from the NC contact, in order to open off the TX inhibit lead..... =? < 1 msec.?
|
|
|
You could try something like W1AEX to accomplish some sequencing pattern. 
|
Oops, I stay logged into groups.io and didn’t realize you have to be already logged in for that link to work.?
I stay logged in in order to be able to quickly start a new thread on groups.io.
If you log in first the link will work.
?
73,
Dave, w6de
?
toggle quoted message
Show quoted text
From: [email protected]
<[email protected]> On Behalf Of Bob via groups.io
Sent: 3 August, 2024 10:21
To: [email protected]
Subject: Re: [ham-amplifiers] Henry 2K-3 TR switching
?
Dave, That link takes me to the 7300 group IO home page but cannot find the RF tail fix.
I do not own a 7300 but have a few friends that do which each of them seem to get things confused so I end up helping them, if you know what I mean.
?
Icom IC-7300 Hot-
switch Mitigation
The Issue
The Icom IC-7300 was released with a flaw in its external amplifier keying circuit apparently caused by an incorrect
timing parameter
programmed into the SEND relay logic. The SEND jack on the rear of the transceiver is used to key an external linear
amplifier on and
off in synchrony with the IC-7300 RF output as mitigated by the Menu/Set/Function TX Delay parameter. That parameter
sets the time
the RF output is delayed from the time the transmitter is keyed on until RF output begins. (The TX Delay parameter
sets the time the
RF output is delayed from the time the transmitter is keyed on, which is not what is addressed in this article; the
TX Delay functions
nominally as expected. This article is concerned with the RF output continuing beyond the time the transmitter is
keyed off, termed an
RF-tail, causing hot-switching of external linear amplifier.)
Unfortunately, there is no similar user adjustable menu setting for controlling the delay time from when the transmitter
ceases RF output
and the SEND jack commands an external amplifier off. Because the IC-7300 continues to output RF energy while an
external amplifier
is in the process of switching off, the amplifier's TR/RX relay is subject to hot-switching and the concomitant possibility
of arcing at the
relay contact points, or worse yet, welding together of those points resulting in the amplifier taken out of service.
This RF-tail issue has been extensively addressed for years by Amateur operators on both the IC-7300 discussion group,
and
Forum. Below is finally a possible hardware solution to the
hot-switching issue originally suggested by Frank Johnson
(G0GSR)
?
Complete description of the fix in in the
ic7300 forum files.
/g/ic-7300/files/ic7300_rf_tail_fix.pdf
?
73,
Dave, w6de
?
?
On Fri, Aug 2, 2024 at 01:40 PM, Bob wrote:
?
As far as the 7300 goes, I thought all that was adjustable in the menu???
In: MENU --> SET --> FUNCTION --> TX DELAY HF
|
Hi Alan,
Here is a link to the ARRL IC7300 review article that I found on the internet.? It was in the August 2016 issue on Page 41.
?
?
It may not be a problem in semi-break-in CW, but it is a concern for QSK CW.? The problem is that RF continues 3ms after the amp key line opens.
? 73
?? Bill K3HZP
|
toggle quoted message
Show quoted text
On Sat, Aug 3, 2024 at 05:21 AM, Bob wrote:
Dave, That link takes me to the 7300 group IO home page but cannot find the RF tail fix.
I do not own a 7300 but have a few friends that do which each of them seem to get things confused so I end up helping them, if you know what I mean.
Bob W4JFA
Hey Bob,
?
I downloaded and attached the 7300 "RF Tail" document... (See attached PDF).
?
--
73,
~Alan
|
On Sat, Aug 3, 2024 at 05:21 AM, Bob wrote:
Dave, That link takes me to the 7300 group IO home page but cannot find the RF tail fix.
I do not own a 7300 but have a few friends that do which each of them seem to get things confused so I end up helping them, if you know what I mean.
Bob W4JFA
Hey Bob,
?
I downloaded and attached the 7300 "RF Tail" document... (See attached PDF).
?
--
73,
~Alan
|
Dave, That link takes me to the 7300 group IO home page but cannot find the RF tail fix. I do not own a 7300 but have a few friends that do which each of them seem to get things confused so I end up helping them, if you know what I mean. Bob W4JFA
Icom IC-7300 Hot-
switch Mitigation
The Issue
The Icom IC-7300 was released with a flaw in its external amplifier keying circuit apparently caused by an incorrect timing parameter
programmed into the SEND relay logic. The SEND jack on the rear of the transceiver is used to key an external linear amplifier on and
off in synchrony with the IC-7300 RF output as mitigated by the Menu/Set/Function TX Delay parameter. That parameter sets the time
the RF output is delayed from the time the transmitter is keyed on until RF output begins. (The TX Delay parameter sets the time the
RF output is delayed from the time the transmitter is keyed on, which is not what is addressed in this article; the TX Delay functions
nominally as expected. This article is concerned with the RF output continuing beyond the time the transmitter is keyed off, termed an
RF-tail, causing hot-switching of external linear amplifier.)
Unfortunately, there is no similar user adjustable menu setting for controlling the delay time from when the transmitter ceases RF output
and the SEND jack commands an external amplifier off. Because the IC-7300 continues to output RF energy while an external amplifier
is in the process of switching off, the amplifier's TR/RX relay is subject to hot-switching and the concomitant possibility of arcing
at the
relay contact points, or worse yet, welding together of those points resulting in the amplifier taken out of service.
This RF-tail issue has been extensively addressed for years by Amateur operators on both the IC-7300 discussion group, and
Forum. Below is finally a possible hardware solution to the hot-switching issue originally suggested by Frank Johnson
(G0GSR)
?
Complete description of the fix in in the ic7300 forum files.
/g/ic-7300/files/ic7300_rf_tail_fix.pdf
?
73,
Dave, w6de
?
?
On Fri, Aug 2, 2024 at 01:40 PM, Bob wrote:
?
As far as the 7300 goes, I thought all that was adjustable in the menu???
In: MENU --> SET --> FUNCTION --> TX DELAY HF
|
On Thu, Aug 1, 2024 at 07:25 PM, Alan - W5ARM wrote:
Howdy Bob,
?
Your second picture provided a better view... I think I figured it out.
?
The "big" 2-pole relay appears to have a micro-switch - or some sort of auxiliary contact -? attached to it (see your pic that I annotated).
?
The micro-switch (or aux contact) (I believe) is actuated by the big relay arm. The "big" relay contacts provide the RF switching (input & output), and the micro-switch/aux contacts provide the bias control via the purple and [barely visible] green wires, which bypass the bias resistor (R-27 on the schematic) located elsewhere.
?
In any case, it appears everything is right there on top, and it should be easy to modify it with a pair of vacuum relays, and a third high-speed relay for bias control.? You'll have to fabricate a little bracket to mount the relays on, and then replace the OEM "big" relay with your new bracket & relays, in the same location.
?
Also, just as an FYI, those Greenstone vacuum relays (from Henry Radio) are pretty compact (see pic below). A pair of them won't take up a whole-lot of room, and should easily fit in the old OEM relay location. I have a pair of them on-hand for a Heathkit HL-2100 project that is on the bench.
?
ON EDIT: FOR SOME REASON, MY TWO SMALL PICS ARE NOT COMING THROUGH... Oh well.
?
--
73,
~Alan
?
--
73,
~Alan
|
Icom IC-7300 Hot-
switch Mitigation
The Issue
The Icom IC-7300 was released with a flaw in its external amplifier keying circuit apparently caused by an incorrect timing parameter
programmed into the SEND relay logic. The SEND jack on the rear of the transceiver is used to key an external linear amplifier on and
off in synchrony with the IC-7300 RF output as mitigated by the Menu/Set/Function TX Delay parameter. That parameter sets the time
the RF output is delayed from the time the transmitter is keyed on until RF output begins. (The TX Delay parameter sets the time the
RF output is delayed from the time the transmitter is keyed on, which is not what is addressed in this article; the TX Delay functions
nominally as expected. This article is concerned with the RF output continuing beyond the time the transmitter is keyed off, termed an
RF-tail, causing hot-switching of external linear amplifier.)
Unfortunately, there is no similar user adjustable menu setting for controlling the delay time from when the transmitter ceases RF output
and the SEND jack commands an external amplifier off. Because the IC-7300 continues to output RF energy while an external amplifier
is in the process of switching off, the amplifier's TR/RX relay is subject to hot-switching and the concomitant possibility of arcing
at the
relay contact points, or worse yet, welding together of those points resulting in the amplifier taken out of service.
This RF-tail issue has been extensively addressed for years by Amateur operators on both the IC-7300 discussion group, and
QRZ.COM Forum. Below is finally a possible hardware solution to the hot-switching issue originally suggested by Frank Johnson
(G0GSR)
?
Complete description of the fix in in the groups.io ic7300 forum files.
/g/ic-7300/files/ic7300_rf_tail_fix.pdf
?
73,
Dave, w6de
?
toggle quoted message
Show quoted text
From: [email protected]
<[email protected]> On Behalf Of Alan - W5ARM via groups.io
Sent: 2 August, 2024 19:00
To: [email protected]
Subject: Re: [ham-amplifiers] Henry 2K-3 TR switching
?
On Fri, Aug 2, 2024 at 01:40 PM, Bob wrote:
?
As far as the 7300 goes, I thought all that was adjustable in the menu???
In: MENU --> SET --> FUNCTION --> TX DELAY HF
|
On Fri, Aug 2, 2024 at 01:40 PM, Bob wrote:
As far as the 7300 goes, I thought all that was adjustable in the menu???
Bob W4JFA
It is...
In: MENU --> SET --> FUNCTION --> TX DELAY HF
--
73,
~Alan
|
Guys, I ordered that board from Tom. Thank you for all the help etc. As far as the 7300 goes, I thought all that was adjustable in the menu??? Bob W4JFA
On Fri, Aug 2, 2024 at 12:38?PM Louis Parascondola via <Gudguyham= [email protected]> wrote:
Many amplifiers have a watch dog circuit that avoids the amp relays from being hot switched. Many amps will delay the closing of the relays until the PTT signal is present and no RF is at the input.? This is mostly prevalent when using CW.? The amp will clip the first bit of RF until there is none and then the relays close.? A 7300 or just about ANY solid state radio without RF delay control will hot switch an SB200,SB220,TL922, Drake etc etc unless the modern radio has an RF delay, the? amp will hot ?switch.? In? the case of the old open frame relay amps, the TR relay can be mechanically sequenced so that the contacts won’t hot switch by insuring that the output contacts switch?before the amplifier is biased on with the bias switching contact of the relay. The 7300 isn’t necessarily singled out on this regard.? Use a 20ms RF delay when using old amps with new radios.
On Friday, August 2, 2024, 11:42 AM, Alan - W5ARM <W5ARM.mail@...> wrote: On Fri, Aug 2, 2024 at 08:23 AM, Bill K3HZP wrote:
Sequencing is required for some rigs. The classic example is the ICOM 7300 which releases the amplifier key line before the RF goes to zero.? See QST review for IC7300.? In this case, sequencing is required on the release transition.??
? .... Bill K3HZP
I find that really hard to believe. That means that using a 7300 with ANY amplifier - even a modern tube or solid state amp - would allow the 7300 to hot-key (or hot "un-key") the amp? This would mean that, in reality, ALL amplifiers are effectively unusable (or subject to damage) if using a 7300, unless "sequencing" were employed.
?
I had (abut sold) a 7300. Never heard of such a thing...
?
I was unable to access the referenced QST article ("members only"), so please provide a quote or screen-shot of the appropriate article section to validate this claim.
?
--
73,
~Alan
|
On Fri, Aug 2, 2024 at 11:37 AM, Louis Parascondola wrote:
Many amplifiers have a watch dog circuit that avoids the amp relays from being hot switched. Many amps will delay the closing of the relays until the PTT signal is present and no RF is at the input. ?This is mostly prevalent when using CW. ?The amp will clip the first bit of RF until there is none and then the relays close. ?A 7300 or just about ANY solid state radio without RF delay control will hot switch an SB200,SB220,TL922, Drake etc etc unless the modern radio has an RF delay, the? amp will hot ?switch. ?In?the case of the old open frame relay amps, the TR relay can be mechanically sequenced so that the contacts won’t hot switch by insuring that the output contacts switch?before the amplifier is biased on with the bias switching contact of the relay. The 7300 isn’t necessarily singled out on this regard. ?Use a 20ms RF delay when using old amps with new radios.
The 7300 does have TX RF output delay... an adjustable delay setting from (IIRC) 7ms (default) to ~30ms (In: MENU --> SET --> FUNCTION --> TX DELAY HF).? My Yaesu 101D also has an RF delay, although (interestingly) it is set through the CW function (break-in delay).? Not sure about Kenwood radios...
--
73,
~Alan
|
Many amplifiers have a watch dog circuit that avoids the amp relays from being hot switched. Many amps will delay the closing of the relays until the PTT signal is present and no RF is at the input. ?This is mostly prevalent when using CW. ?The amp will clip the first bit of RF until there is none and then the relays close. ?A 7300 or just about ANY solid state radio without RF delay control will hot switch an SB200,SB220,TL922, Drake etc etc unless the modern radio has an RF delay, the? amp will hot ?switch. ?In? the case of the old open frame relay amps, the TR relay can be mechanically sequenced so that the contacts won’t hot switch by insuring that the output contacts switch?before the amplifier is biased on with the bias switching contact of the relay. The 7300 isn’t necessarily singled out on this regard. ?Use a 20ms RF delay when using old amps with new radios.
On Friday, August 2, 2024, 11:42 AM, Alan - W5ARM <W5ARM.mail@...> wrote: On Fri, Aug 2, 2024 at 08:23 AM, Bill K3HZP wrote:
Sequencing is required for some rigs. The classic example is the ICOM 7300 which releases the amplifier key line before the RF goes to zero.? See QST review for IC7300.? In this case, sequencing is required on the release transition.??
? .... Bill K3HZP
I find that really hard to believe. That means that using a 7300 with ANY amplifier - even a modern tube or solid state amp - would allow the 7300 to hot-key (or hot "un-key") the amp? This would mean that, in reality, ALL amplifiers are effectively unusable (or subject to damage) if using a 7300, unless "sequencing" were employed.
?
I had (abut sold) a 7300. Never heard of such a thing...
?
I was unable to access the referenced QST article ("members only"), so please provide a quote or screen-shot of the appropriate article section to validate this claim.
?
--
73,
~Alan
|
On Fri, Aug 2, 2024 at 08:23 AM, Bill K3HZP wrote:
Sequencing is required for some rigs. The classic example is the ICOM 7300 which releases the amplifier key line before the RF goes to zero.? See QST review for IC7300.? In this case, sequencing is required on the release transition.??
? .... Bill K3HZP
I find that really hard to believe. That means that using a 7300 with ANY amplifier - even a modern tube or solid state amp - would allow the 7300 to hot-key (or hot "un-key") the amp? This would mean that, in reality, ALL amplifiers are effectively unusable (or subject to damage) if using a 7300, unless "sequencing" were employed.
?
I had (abut sold) a 7300. Never heard of such a thing...
?
I was unable to access the referenced QST article ("members only"), so please provide a quote or screen-shot of the appropriate article section to validate this claim.
?
--
73,
~Alan
|
Sequencing is required for some rigs. The classic example is the ICOM 7300 which releases the amplifier key line before the RF goes to zero.? See QST review for IC7300.? In this case, sequencing is required on the release transition.??
? .... Bill K3HZP
|
I agree. You never had any kind of sequencing with the old relay.
The new vacuum relays will be so much faster that you probably
won't need to bother with all that.
73, Alek VK6APK.
On 31/07/2024 11:37 pm, Bob wrote:
toggle quoted message
Show quoted text
Hello Jim, I was hoping you would respond. I've
read just about every amp article/post you've written the past
few years. Thank you.
I believe my 2K-3 OEM relay looks like this... Three
contacts.
You said in your last sentence... Simplify
it....just operate all 3 of em at once ( even if u don't
speed em up....and all 3 operate in 3 msecs) .? I
would be thrilled over that!
If so, that's what I had been thinking, basically, much
better than before/OEM. I didn't know if I was missing
something or not. Can it really be that simple?
Thanks again, Bob W4JFA
I just went through this with my 4 x Drake L4B's.?
I used 3 x new Gigavac GH1's.? ?You can buy em with either a
12 vdc coil or a 26.5 vdc coil.? ?Jennings version is called
an RJ1A. The kilovac version is called a HC-1.....and the
coils in all 3 x brands are field swappable to either a 12 /
26.5 / 115 vdc coil.? ?The Gigavac uses metric threads on
the big lockdown nut.
I used em for input / output / bias.? ?In my case, I used
the 12 vdc coil version.....and wired all 3 x coils in
series.? The oem drake fil xfmr also has a 22 vac winding on
it to run the oem 3PDT clunker TR relay.? Drake used a 1/2
wave rectifier, so the output was 31 vdc no load.? ?In my
case, I changed that to a FWD ( full wave doubler) to obtain
63 vdc no load.? ?A 175 ohm @ 25 watt metal finned dropping
resistor is used in series with the 3 x series coils. 36 vdc
used to operate the 3 x series 12 vdc coils.? 27 vdc is
dropped across the 175 ohm series drop resistor. Drop
resistor dissipates 3.9 watts on TX....and 0 watts on RX.?
IE: when T=0, the relay coils get hit with an initial over
voltage. (63/3 or 21 vdc per coil)....which will? speed em
up.? To speed em up even more, a 50uf @ 150 vdc lytic is
wired in parallel with the 175 ohm drop resistor.? This is
called a ...'RC hotshot' circuit. Jennings, Kilovac, Gigavac
all mention it's use.? ( Alpha used it on their older amps,
that used a vac relay.? Alpha used 36 vdc applied to the
26.5 vdc coil, and also a small lytic across the series drop
resistor).? With the small cap in parallel with the drop
resistor, it sustains the over voltage a hair longer.? The
concept works superb.? ?All 3 x vac relays in each drake amp
operate in slightly under 1 msec.?
80% of the total operate time is spent just building up the
magnetic field in the coil. (The XL of the coil impedes DC
current flow).? The over voltage? makes the current flow
faster.
The ONLY thing that needs to be sequenced is the RF output
from the xcvr itself.? You want to key the amp NOW,? but
delay RF from the xcvr by 1-2 msecs.? This gives the sped up
vac relays in the amp a head start.?
Modern xcvr's have an adjustable TX RF output delay...which
works on both CW + SSB.? ?My yaseu MK-V has an adjustable
0-30 msec delay, ( in 1 msec increments) to prevent hot
switching? the slow 3PDT mech relay in the older tube amps.
The drake 3PDT operates in 17 msecs.? ?The 3PDT in the
ameritron amps operates in 15 msecs.? ? The delay in the
MK-V was set at 20 msecs to ensure the oem drake relay got a
head start.? BUT the adjustable delay in the MK-V only works
on CW.? ?For SSB use, plan B.... which is to re-use the spst
tiny relay in the MK-V? (was used to key an amp)? to instead
GRND the TX inhibit lead in the MK-V.? ?UNTIL u grnd the TX
inhibit lead, you can key the amp, but zero RF coming out of
the xcvr.? ?To actually key the relays in the amp, I use an
opto isolator. The input of the opto is keyed? via the
'electronic TX grnd'? from the MK-V.? Input of opto only
draws a few ma.? ?You can get em with a 5-15-24 vdc input (
and each of those has a super wide operating range)..and the
output side is rated for either? 60 vdc @ 3 amps CCS...or
250 vdc @ 1 amp CCS.? 5 kv? isolation between input side and
output side.?
You can also use a 2nd opto to do the bias in the amp, which
works good.?
Ok, back to the henry 2K-3.? ?The small relay? xfmr in the
2K-3 is 8.5 vac on either side of the CT.? ?It's a FWCT
config.? Output is 8.5 vac x 1.414 = 12 vdc.? ?I would
reconfigure the small relay xfmr to a FWB..and use the
entire sec winding ( CT not used).? ?Then it becomes 17 vac
x 1.414 = 24 vdc no load.? ?Ok, then? wire the 3 x 12 vdc
vac relay coils in parallel.? ?Each 12 vdc coil is 80 ohms.?
?12 vdc / 26.67 ohms, ( 80/3 = 26.67 ohms)? ?= .450 amps.
The series drop resistor will be 26.67 ohms.? Diss in the
resistor will be (.45 x .45) x 26.67 ohms = 5.4 watts.?
?Each relay coil will diss? 1.8 watts.? Each coil has 150 ma
flowing through it.? Wire a 50 uf @? 100-150 vdc (axial
lead) lytic across the drop resistor.?
Depending on xcvr used, it has to handle? 24 vdc OCV (open
circuit voltage)? @ 450 ma under load.? You do NOT want to
use a slow mech relay in the xcvr to key the sped up vac
relays!? ?Hence the use of either an opto isolator or a fast
switch transistor.?
Ok, the 3 x relays will operate / rls in just a hair < 1
msec.? No hot switching.
I found a sidewall on the L4B, that would take all 3 x vac
relays.? ? A 9/16" hole is required.? ( A 5/8" will also
work).? ?The greenlee 1/2" -? 9/16"? - 5/8"? punches all use
a 1/4" draw stud....and hence require a 1/4" pilot hole.? I
used my roper whitney hand punch to punch the 3 x 1/4"?
pilot holes....bam, done.? Then the greenlee 9/16" punch
(die and cup, just tighten the wrench).?
You could use just 2 x vac relays...for input /
output.....and an opto for the cut off bias.? That would
save one vac relay.? ?You could maybe, use a super fast SPDT
tiny mech relay for the input side.? I wanted vac relay on
both the input and output, so the amp will handle 2 kw on
bypass mode.? ?I do that, since I string several drake amps
in series, one per band, or one at each end of 80m etc, or
any other combo.? A simple rotary switch in the key line of
the xcvr ensures only one amp can ever be keyed at one
time.? ? ?On the drake L4B, the only way to calibrate the
internal wattmeter is to take it apart to get to the
underside of chassis....and apply 1 kw cxr from a 2nd
amplifier ( with a bird 43)? to the drake amp...which of
course is powered down, and on bypass.? IE: it has to handle
a kw on bypass mode anyway.?
You could mount one vac relay near the input coax connector,
and a 2nd vac relay near the output side....or near the load
cap.? Then a short length of RG-400 between the NC contacts
of the input + output relay. ( aka..the 'bypass leg' ).? ?
All 3 of my vac relays are dead quiet.? ?The gigavac GH1 hi
-pot tests to 7.5 kv.?
The idea of using a 12 vdc coil came from the eng dept at
Kilovac, during a phone call I had with em years ago.? "IF u
are voltage limited, use the 12 vdc coil".?
There is also another method to obtain 28 vdc in ur henry
amp.? It uses a 10 vac fil xfmr ( with fils in series).?
?Tap off the 10 vac sec...and use a FWD ( doubler)? to
obtain 28.28 vdc.?
Without the speedup circuit, the vac relays typ operate in
2-3 msecs.? ?In the past, folks would use a semi complicated
sequencing mess...so the output relay would operate
1st.....like say 3 msec.? ?Then the input relay next, say 5
msecs...then the bias relay last....say 7 msecs.? When going
back to RX, the rls sequence was reversed, with bias relay
releasing 1st, then input relay, the output relay last.?
Simplify it....just operate all 3 of em at once ( even if u
don't speed em up....and all 3 operate in 3 msecs) .? The
only thing that has to be sequenced is to delay grnding the
handy dandy? TX inhibit lead in the xcvr.?
?
Sri? for the diatribe.?
Jim? VE7RF
|
Howdy Bob,
?
Your second picture provided a better view... I think I figured it out.
?
The "big" 2-pole relay appears to have a micro-switch - or some sort of auxiliary contact -? attached to it (see your pic that I annotated).
?
The micro-switch (or aux contact) (I believe) is actuated by the big relay arm. The "big" relay contacts provide the RF switching (input & output), and the micro-switch/aux contacts provide the bias control via the purple and [barely visible] green wires, which bypass the bias resistor (R-27 on the schematic) located elsewhere.
?
In any case, it appears everything is right there on top, and it should be easy to modify it with a pair of vacuum relays, and a third high-speed relay for bias control.? You'll have to fabricate a little bracket to mount the relays on, and then replace the OEM "big" relay with your new bracket & relays, in the same location.
?
Also, just as an FYI, those Greenstone vacuum relays (from Henry Radio) are pretty compact (see pic below). A pair of them won't take up a whole-lot of room, and should easily fit in the old OEM relay location. I have a pair of them on-hand for a Heathkit HL-2100 project that is on the bench.
?
ON EDIT: FOR SOME REASON, MY TWO SMALL PICS ARE NOT COMING THROUGH... Oh well.
?
 ? ?
?
--
73,
~Alan
|
Bob
Bill K3HZP
Alan - W5ARM