Re: [Repeater-Builder] Astron P/S question
Bob Astron 35A supplies and probably other sizes are sensitive to the SCR triggering. One of the causes I found was due to a shift in the initial routing from the rectifier to the capacitors. When you put a supply back together be sure to give as much space as possible between the gate lead of the SCR and those wires going to the rectifier. Capacitor inrush at the peak of the 60Hz power turn on is prone to trigger the SCR. Gran K6RIF At 07:53 AM 12/8/2008, you wrote: I've had DMMs also go nuts at my site too. Luckily the Astron supply hasn't had that problem yet. The fuse usually blows when something catastrophic happens. One such thing is when the output voltage goes too high and the built-in SCR crowbar fires. It shorts the supply immediately, and the excess current usually causes the fuse to blow. Sometimes it also causes the diodes to short out, and they end up blowing the fuse. RF getting back into the supply can trip the SCR. Even RF riding on the supply lines can cause the voltage that the SCR sees to be high enough to trip it, even though it may not show up with a meter or even a scope. You've probably done all you can with the ferrites unless you missed the wires going to the SCR. On some supplies it's mounted to the chassis and has fairly long wires (just waiting to pick up RF) running to it. You'd be better off with ANY kind of unregulated power supply, such as what you had with the MICOR supply. Ferro-resonant transformers usually aren't susceptible to such RF problems, and there's nothing electronic such as a crowbar inside to trip and blow the fuse. This doesn't explain why your MICOR supply blew its fuse, unless you exceeded the output current capability. Most MICORs were only rated up to 100 watts, and the supplies probably are good to 25-30 amps MAX; it seems that your PA is already exceeding that. Then you tack on a receiver, exciter, etc, and you've gone past the limit for the MICOR supply. Even an MSF5000 supply would be strained to handle that much current; that's why the bigger stations have TWO supplies, one for each PA, and the VHF stations have 28V supplies in them. Solutions? You might consider a battery and a charger that's strong enough to keep the PA happy, to run just the PA. Split everything else off and run that on another smaller supply. Consider a switching regulator supply, rather than a linear regulator supply, to run the rest of the equipment. I know that some of the high power amps are now being built to run on 24-28VDC. This cuts the current consumption in half and they can be run with switching supplies. Let's hope Skip comes aboard here. I know he's had experience with these units. Bob M. == --- On Mon, 12/8/08, n9wys mailto:n9wys%40ameritech.netn9...@ameritech.net wrote: From: n9wys mailto:n9wys%40ameritech.netn9...@ameritech.net Subject: [Repeater-Builder] Astron P/S question To: mailto:Repeater-Builder%40yahoogroups.comRepeater-Builder@yahoogroups.com Date: Monday, December 8, 2008, 10:20 AM For the learned group here  I know there has been some discussion on one the list regarding Astron Power supplies. Unfortunately, searching hasnât revealed what I am looking for, so I pose my query here and apologize in advance if this was a subject that was discussed at length in the past  I will ddescribe my problem in detail, so forgive me for being so verbose right off the bat; but I figure if I provide a lot of info now, it will avoid a lot of question and answer exchanges later in order to get an understanding of my problem.  I have a UHF ham repeater system (TKR-820 as transmitter, MICOR SpectraTAC receiver and comparator, Astron RM-70 Power Supply, and Crescend 150W P/A) that is experiencing issues with the power supply. Seems that when the repeater is on the air for any time (for example, over three minutes key-down) the power supply blows a fuse. The first time this happened, I changed out the P/S with a MICOR supply I had from a 100W continuous duty station. It also blew THAT fuse  The Astron supply that blew the fuse had two bad diodes in the rectifier, so that was repaired. There was nothing found wrong with the Motorola supply, other than the main fuse had blown.  I took the PA back to Crescend, but they found nothing wrong with the P/A.  The station was put back on the air with the repaired Astron supply. Was on the air for about two weeks, and failed again while I was talking to another ham. Went back to the tower and found the fuse blown again in the supply. I took the PA offline and brought it back to Crescend, told them of the issue with the P/S, and that I needed them to check the PA for problems. Their service tech called me and said heâd had the PA running on his workbench as we spoke, and had it transmitting for about 45 minutes with no problems all operating within spec (~32AA nominal - 38A max draw
RE: [Repeater-Builder] Astron P/S question
Since I’m the one who started this thread, I think it is incumbent upon me to let the collective masses know how I am proceeding… To date, I have added additional filter caps (0.1 µf disc caps) to the SCR (GATE to GND) and across the output of the supply. I have already affixed ferrites to both ends of the cabling going from the supply to the PA. I am still blowing fuses. I am planning on adding caps from each output line (POS and NEG) to chassis ground. I was also told to dial down the output voltage a bit (it is at 13.8V now) to around 13.2V, because the Astron “ramps up” the voltage to its transistors as the supply nears rated capacity, which closes the gap between the operating voltages and where the SCR triggers. Can anyone confirm this? In the end if these fixes fail, I will be relegating the Astron to other duties (AKA: the trash can). I temporarily replaced the Astron supply with a 75A switching supply, and so far no problems – even after 30 minutes of steady operation of the repeater. (The Astron would fail after about 10 – 15 minutes of operation.) I was able to get my hands on a service monitor – the building is not shielded in any way, so there is RF all over the place. The only major peak we saw, however, was about 11.7 MHZ down from the center freq of my UHF repeater (the repeater TX is at 444.5500, the bump was at 437.8500) and after some testing we found it was from the switcher. It does not seem to be affecting the receiver of my repeater… For now, I think I’m going to stay with the switcher, until I am sure we have found a permanent fix for the Astron. Besides, with the current temp at -2°F, I’m in no hurry to go to the tower site. grin How ‘bout it, Skipp?? Any ideas? I know you’ve been away and busy, but I hope you are catching up on the thread… Mark - N9WYS From: Repeater-Builder@yahoogroups.com On Behalf Of Gran Clark Bob Astron 35A supplies and probably other sizes are sensitive to the SCR triggering. One of the causes I found was due to a shift in the initial routing from the rectifier to the capacitors. When you put a supply back together be sure to give as much space as possible between the gate lead of the SCR and those wires going to the rectifier. Capacitor inrush at the peak of the 60Hz power turn on is prone to trigger the SCR. Gran K6RIF At 07:53 AM 12/8/2008, Bob M. wrote: I've had DMMs also go nuts at my site too. Luckily the Astron supply hasn't had that problem yet. The fuse usually blows when something catastrophic happens. One such thing is when the output voltage goes too high and the built-in SCR crowbar fires. It shorts the supply immediately, and the excess current usually causes the fuse to blow. Sometimes it also causes the diodes to short out, and they end up blowing the fuse. RF getting back into the supply can trip the SCR. Even RF riding on the supply lines can cause the voltage that the SCR sees to be high enough to trip it, even though it may not show up with a meter or even a scope. You've probably done all you can with the ferrites unless you missed the wires going to the SCR. On some supplies it's mounted to the chassis and has fairly long wires (just waiting to pick up RF) running to it. You'd be better off with ANY kind of unregulated power supply, such as what you had with the MICOR supply. Ferro-resonant transformers usually aren't susceptible to such RF problems, and there's nothing electronic such as a crowbar inside to trip and blow the fuse. This doesn't explain why your MICOR supply blew its fuse, unless you exceeded the output current capability. Most MICORs were only rated up to 100 watts, and the supplies probably are good to 25-30 amps MAX; it seems that your PA is already exceeding that. Then you tack on a receiver, exciter, etc, and you've gone past the limit for the MICOR supply. Even an MSF5000 supply would be strained to handle that much current; that's why the bigger stations have TWO supplies, one for each PA, and the VHF stations have 28V supplies in them. Solutions? You might consider a battery and a charger that's strong enough to keep the PA happy, to run just the PA. Split everything else off and run that on another smaller supply. Consider a switching regulator supply, rather than a linear regulator supply, to run the rest of the equipment. I know that some of the high power amps are now being built to run on 24-28VDC. This cuts the current consumption in half and they can be run with switching supplies. Let's hope Skip comes aboard here. I know he's had experience with these units. Bob M. ==
RE: [Repeater-Builder] Astron P/S question
First, I have a much bigger trash can at my house, so you can send that supply my way ! No sense wasting it in YOUR trash can. Second, if the supply output voltage did change as a function of load, then the 723 regulator is not doing its job. I can tell you that the whole idea of a regulated power supply is to maintain the output voltage regardless of load, at least until something draws excessive current. I set all of my supplies to 14.00VDC and label them as such; haven't had a problem in 20 years. The crowbar shouldn't fire until about 16 volts, but it certainly IS sensitive to RF, and if a lot is floating around, that can definitely trigger it. Whether it's the SCR itself, or the sense circuit driving it, something is causing it to fire and blow the fuse. You'd need to measure the actual output voltage of the supply to see if it's going that high or if the SCR is being falsely triggered. Of course, you only get one shot at trying it before the fuse blows. Astron supplies will not turn on if there's a significant load on them when AC power is applied. I had one powering a 90w amplifier that drew about 16 amps. If drive was applied when I turned the Astron supply on, it would output zero volts. I had to remove the drive, thus removing the load, then turn the supply on, then turn the drive on. Most of the time this isn't a problem. It does the same thing with a 1/2 ohm load attached to the output terminals; goes into immediate current overload foldback. Seems to be happy to sit that way, but of course you don't get any output voltage. Bob M. == --- On Mon, 12/22/08, n9wys n9...@ameritech.net wrote: From: n9wys n9...@ameritech.net Subject: RE: [Repeater-Builder] Astron P/S question To: Repeater-Builder@yahoogroups.com Date: Monday, December 22, 2008, 1:17 PM Since I’m the one who started this thread, I think it is incumbent upon me to let the collective masses know how I am proceeding… To date, I have added additional filter caps (0.1 µf disc caps) to the SCR (GATE to GND) and across the output of the supply. I have already affixed ferrites to both ends of the cabling going from the supply to the PA. I am still blowing fuses. I am planning on adding caps from each output line (POS and NEG) to chassis ground. I was also told to dial down the output voltage a bit (it is at 13.8V now) to around 13.2V, because the Astron “ramps up” the voltage to its transistors as the supply nears rated capacity, which closes the gap between the operating voltages and where the SCR triggers. Can anyone confirm this? In the end if these fixes fail, I will be relegating the Astron to other duties (AKA: the trash can). I temporarily replaced the Astron supply with a 75A switching supply, and so far no problems – even after 30 minutes of steady operation of the repeater. (The Astron would fail after about 10 – 15 minutes of operation.) I was able to get my hands on a service monitor – the building is not shielded in any way, so there is RF all over the place. The only major peak we saw, however, was about 11.7 MHZ down from the center freq of my UHF repeater (the repeater TX is at 444.5500, the bump was at 437.8500) and after some testing we found it was from the switcher. It does not seem to be affecting the receiver of my repeater… For now, I think I’m going to stay with the switcher, until I am sure we have found a permanent fix for the Astron. Besides, with the current temp at -2°F, I’m in no hurry to go to the tower site. grin How ‘bout it, Skipp?? Any ideas? I know you’ve been away and busy, but I hope you are catching up on the thread… Mark - N9WYS
Re: [Repeater-Builder] Astron P/S question
On Mon, 8 Dec 2008, n9wys wrote: Now - here's the WEIRD part. when I was at the tower with another tech and replaced the fuse the time before the last failure, we tried to use his DMM to check the P/S fuse for continuity. His meter acted as if the battery was dead - but later investigation revealed that the meter was getting hit with RF from another transmitter at the site. So I'm thinking that the RF problem may or may not be directly related to MY transmitter. (There is VHF 100W MICOR transmitter directly next to my equipment rack that is on 161.325, and transmits 24/7/365.) If you can, see about getting a spectral plot of the machine on 161.325; it's possible that it could be recieving RF in the transmitter port and mixing as well as amplifying the mix and generating garbage all over the place. However, for the DMM to act up -- you might really be in a high RF field, which shouldn't happen if you're on the ground unless there's a 50KW transmitter only 100 ft up. Might be time to invest in a NARDA RF monitor. -- Kris Kirby, KE4AHR k...@catonic.us But remember, with no superpowers comes no responsibility. --rly
Re: [Repeater-Builder] Astron P/S question
Clip the purple wire going to the crowbar. The crowbar in the Astron is one of the most messed up deals ever. Astron also makes and auto reset kit for the crowbar. Or better yet, go find a Mastr II 35 amp supply and be done with it. Paul,ZW On Tue, Dec 9, 2008 at 12:33 PM, n9wys [EMAIL PROTECTED] wrote: Thanks to all who have offered suggestions – however sarcastic – about remedying this situation. They *all* merit consideration, and I will certainly do so... and will post my results! 73 de Mark - N9WYS
RE: [Repeater-Builder] Astron P/S question
Thanks to all who have offered suggestions - however sarcastic - about remedying this situation. They all merit consideration, and I will certainly do so... and will post my results! 73 de Mark - N9WYS
[Repeater-Builder] Astron P/S question
For the learned group here. I know there has been some discussion on one the list regarding Astron Power supplies. Unfortunately, searching hasn't revealed what I am looking for, so I pose my query here and apologize in advance if this was a subject that was discussed at length in the past. I will describe my problem in detail, so forgive me for being so verbose right off the bat; but I figure if I provide a lot of info now, it will avoid a lot of question and answer exchanges later in order to get an understanding of my problem. I have a UHF ham repeater system (TKR-820 as transmitter, MICOR SpectraTAC receiver and comparator, Astron RM-70 Power Supply, and Crescend 150W P/A) that is experiencing issues with the power supply. Seems that when the repeater is on the air for any time (for example, over three minutes key-down) the power supply blows a fuse. The first time this happened, I changed out the P/S with a MICOR supply I had from a 100W continuous duty station. It also blew THAT fuse. The Astron supply that blew the fuse had two bad diodes in the rectifier, so that was repaired. There was nothing found wrong with the Motorola supply, other than the main fuse had blown. I took the PA back to Crescend, but they found nothing wrong with the P/A. The station was put back on the air with the repaired Astron supply. Was on the air for about two weeks, and failed again while I was talking to another ham. Went back to the tower and found the fuse blown again in the supply. I took the PA offline and brought it back to Crescend, told them of the issue with the P/S, and that I needed them to check the PA for problems. Their service tech called me and said he'd had the PA running on his workbench as we spoke, and had it transmitting for about 45 minutes with no problems - all operating within spec (~32A nominal - 38A max draw @ 165W output). After we talked some more, he said he'd leave it run all night. If it was OK, he'd ship it back. I got the PA back the following Tuesday. I put the station back on the air. In the meantime, I spoke with an engineer from Crescend who told me that they had some experience with RF getting into Astron supplies. so when I took the PA back to the tower, I put ferrites on the A+ and ground leads to the P/S from the PA. (There are about 10 wires altogether in the power cable going to the PA - two bundles of three A+, and four Grounds.) I put three ferrites altogether on the DC lines, and made three turns through the ferrites with each bundle. These were installed as close as physically possible to the power supply. I also put one turn on a ferrite for the entire bundle at the PA end. (Couldn't do more than that - was running out of cable length for hook-up.) I replaced the fuse again, and got the station back on the air. Worked for about 45 minutes (or long enough for me to be far enough away from the tower where I couldn't make a return trip that day) and promptly blew the fuse again. (Or so I suspect.) I haven't had a chance to go back to examine the cause of the failure this time - yet. Now - here's the WEIRD part. when I was at the tower with another tech and replaced the fuse the time before the last failure, we tried to use his DMM to check the P/S fuse for continuity. His meter acted as if the battery was dead - but later investigation revealed that the meter was getting hit with RF from another transmitter at the site. So I'm thinking that the RF problem may or may not be directly related to MY transmitter. (There is VHF 100W MICOR transmitter directly next to my equipment rack that is on 161.325, and transmits 24/7/365.) OK - here are the questions: 1) Has anyone experienced an issue with RF getting into Astron power supplies, and how did you remedy the issue? 2) Since the P/S fails only when my transmitter is on the air, could I be getting a mix of RF (the VHF and my UHF) that is causing this? To answer a question that may be posed, I do not have a SpecAn available to me to check for spurs, but I am contacting the county radio tech (it's a county-owned tower) to see if he can assist me with this. Any ideas, other than purchasing a hardened power supply, that could remedy my situation? Thanks, Mark - N9WYS
Re: [Repeater-Builder] Astron P/S question
I've had DMMs also go nuts at my site too. Luckily the Astron supply hasn't had that problem yet. The fuse usually blows when something catastrophic happens. One such thing is when the output voltage goes too high and the built-in SCR crowbar fires. It shorts the supply immediately, and the excess current usually causes the fuse to blow. Sometimes it also causes the diodes to short out, and they end up blowing the fuse. RF getting back into the supply can trip the SCR. Even RF riding on the supply lines can cause the voltage that the SCR sees to be high enough to trip it, even though it may not show up with a meter or even a scope. You've probably done all you can with the ferrites unless you missed the wires going to the SCR. On some supplies it's mounted to the chassis and has fairly long wires (just waiting to pick up RF) running to it. You'd be better off with ANY kind of unregulated power supply, such as what you had with the MICOR supply. Ferro-resonant transformers usually aren't susceptible to such RF problems, and there's nothing electronic such as a crowbar inside to trip and blow the fuse. This doesn't explain why your MICOR supply blew its fuse, unless you exceeded the output current capability. Most MICORs were only rated up to 100 watts, and the supplies probably are good to 25-30 amps MAX; it seems that your PA is already exceeding that. Then you tack on a receiver, exciter, etc, and you've gone past the limit for the MICOR supply. Even an MSF5000 supply would be strained to handle that much current; that's why the bigger stations have TWO supplies, one for each PA, and the VHF stations have 28V supplies in them. Solutions? You might consider a battery and a charger that's strong enough to keep the PA happy, to run just the PA. Split everything else off and run that on another smaller supply. Consider a switching regulator supply, rather than a linear regulator supply, to run the rest of the equipment. I know that some of the high power amps are now being built to run on 24-28VDC. This cuts the current consumption in half and they can be run with switching supplies. Let's hope Skip comes aboard here. I know he's had experience with these units. Bob M. == --- On Mon, 12/8/08, n9wys [EMAIL PROTECTED] wrote: From: n9wys [EMAIL PROTECTED] Subject: [Repeater-Builder] Astron P/S question To: Repeater-Builder@yahoogroups.com Date: Monday, December 8, 2008, 10:20 AM For the learned group here… I know there has been some discussion on one the list regarding Astron Power supplies. Unfortunately, searching hasn’t revealed what I am looking for, so I pose my query here and apologize in advance if this was a subject that was discussed at length in the past… I will describe my problem in detail, so forgive me for being so verbose right off the bat; but I figure if I provide a lot of info now, it will avoid a lot of question and answer exchanges later in order to get an understanding of my problem. I have a UHF ham repeater system (TKR-820 as transmitter, MICOR SpectraTAC receiver and comparator, Astron RM-70 Power Supply, and Crescend 150W P/A) that is experiencing issues with the power supply. Seems that when the repeater is on the air for any time (for example, over three minutes key-down) the power supply blows a fuse. The first time this happened, I changed out the P/S with a MICOR supply I had from a 100W continuous duty station. It also blew THAT fuse… The Astron supply that blew the fuse had two bad diodes in the rectifier, so that was repaired. There was nothing found wrong with the Motorola supply, other than the main fuse had blown. I took the PA back to Crescend, but they found nothing wrong with the P/A. The station was put back on the air with the repaired Astron supply. Was on the air for about two weeks, and failed again while I was talking to another ham. Went back to the tower and found the fuse blown again in the supply. I took the PA offline and brought it back to Crescend, told them of the issue with the P/S, and that I needed them to check the PA for problems. Their service tech called me and said he’d had the PA running on his workbench as we spoke, and had it transmitting for about 45 minutes with no problems – all operating within spec (~32A nominal - 38A max draw @ 165W output). After we talked some more, he said he’d leave it run all night. If it was OK, he’d ship it back. I got the PA back the following Tuesday. I put the station back on the air… In the meantime, I spoke with an engineer from Crescend who told me that they had some experience with RF getting into Astron supplies… so when I took the PA back to the tower, I put ferrites on the A+ and ground leads to the P/S from the PA. (There are about 10 wires altogether in the power cable going to the PA – two bundles of three A+, and four Grounds.) I put three ferrites altogether on the DC lines, and made three turns through
Re: [Repeater-Builder] Astron P/S question
Is each individual device that's running off that power supply independently fused in its A+ lead? If so, and none of those fuses are blowing, that points back to the crowbar circuit in the power supply. If not, fusing each A+ lead may help to isolate which device is drawing too much current after extended key-down. Adding an EMI/RFI filter to the PS line in might help (if you need one, I have a few laying around, scavenged from various devices), and I saw a message in another ham group over the weekend where someone had much better RFI suppression results using powdered iron toroids rather than ferrites... #6 mix (red) 2-1/2. . George, KA3HSW / WQGJ413 From: n9wys [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Monday, December 8, 2008 9:20:23 AM Subject: [Repeater-Builder] Astron P/S question For the learned group here… I know there has been some discussion on one the list regarding Astron Power supplies. Unfortunately, searching hasn’t revealed what I am looking for, so I pose my query here and apologize in advance if this was a subject that was discussed at length in the past… I will describe my problem in detail, so forgive me for being so verbose right off the bat; but I figure if I provide a lot of info now, it will avoid a lot of question and answer exchanges later in order to get an understanding of my problem. I have a UHF ham repeater system (TKR-820 as transmitter, MICOR SpectraTAC receiver and comparator, Astron RM-70 Power Supply, and Crescend 150W P/A) that is experiencing issues with the power supply. Seems that when the repeater is on the air for any time (for example, over three minutes key-down) the power supply blows a fuse. The first time this happened, I changed out the P/S with a MICOR supply I had from a 100W continuous duty station. It also blew THAT fuse… The Astron supply that blew the fuse had two bad diodes in the rectifier, so that was repaired. There was nothing found wrong with the Motorola supply, other than the main fuse had blown. I took the PA back to Crescend, but they found nothing wrong with the P/A. The station was put back on the air with the repaired Astron supply. Was on the air for about two weeks, and failed again while I was talking to another ham. Went back to the tower and found the fuse blown again in the supply. I took the PA offline and brought it back to Crescend, told them of the issue with the P/S, and that I needed them to check the PA for problems. Their service tech called me and said he’d had the PA running on his workbench as we spoke, and had it transmitting for about 45 minutes with no problems – all operating within spec (~32A nominal - 38A max draw @ 165W output). After we talked some more, he said he’d leave it run all night. If it was OK, he’d ship it back. I got the PA back the following Tuesday. I put the station back on the air… In the meantime, I spoke with an engineer from Crescend who told me that they had some experience with RF getting into Astron supplies… so when I took the PA back to the tower, I put ferrites on the A+ and ground leads to the P/S from the PA. (There are about 10 wires altogether in the power cable going to the PA – two bundles of three A+, and four Grounds.) I put three ferrites altogether on the DC lines, and made three turns through the ferrites with each bundle. These were installed as close as physically possible to the power supply. I also put one turn on a ferrite for the entire bundle at the PA end. (Couldn’t do more than that – was running out of cable length for hook-up.) I replaced the fuse again, and got the station back on the air. Worked for about 45 minutes (or long enough for me to be far enough away from the tower where I couldn’t make a return trip that day) and promptly blew the fuse again. (Or so I suspect.) I haven’t had a chance to go back to examine the cause of the failure this time – yet. Now – here’s the WEIRD part… when I was at the tower with another tech and replaced the fuse the time before the last failure, we tried to use his DMM to check the P/S fuse for continuity. His meter acted as if the battery was dead – but later investigation revealed that the meter was getting hit with RF from another transmitter at the site. So I’m thinking that the RF problem may or may not be directly related to MY transmitter. (There is VHF 100W MICOR transmitter directly next to my equipment rack that is on 161.325, and transmits 24/7/365.) OK – here are the questions: 1) Has anyone experienced an issue with RF getting into Astron power supplies, and how did you remedy the issue? 2) Since the P/S fails only when my transmitter is on the air, could I be getting a mix of RF (the VHF and my UHF) that is causing this? To answer a question that may be posed, I do not have a SpecAn available to me to check for spurs, but I am contacting the county radio
RE: [Repeater-Builder] Astron P/S question
Hi, Bob. Long time, no chat! The Astron P/S only supplies the PA - all other items in the rack have their own power supplies, but I can still see where I may have exceeded the MICOR supply current limits. Other than that, I've been told to check al the coax jumpers to ensure they are in good order... to eliminate any RF issues. I do access to a 120A switcher that I may try and see what happens. Mark - N9WYS -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Bob M. Sent: Monday, December 08, 2008 9:54 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Astron P/S question I've had DMMs also go nuts at my site too. Luckily the Astron supply hasn't had that problem yet. The fuse usually blows when something catastrophic happens. One such thing is when the output voltage goes too high and the built-in SCR crowbar fires. It shorts the supply immediately, and the excess current usually causes the fuse to blow. Sometimes it also causes the diodes to short out, and they end up blowing the fuse. RF getting back into the supply can trip the SCR. Even RF riding on the supply lines can cause the voltage that the SCR sees to be high enough to trip it, even though it may not show up with a meter or even a scope. You've probably done all you can with the ferrites unless you missed the wires going to the SCR. On some supplies it's mounted to the chassis and has fairly long wires (just waiting to pick up RF) running to it. You'd be better off with ANY kind of unregulated power supply, such as what you had with the MICOR supply. Ferro-resonant transformers usually aren't susceptible to such RF problems, and there's nothing electronic such as a crowbar inside to trip and blow the fuse. This doesn't explain why your MICOR supply blew its fuse, unless you exceeded the output current capability. Most MICORs were only rated up to 100 watts, and the supplies probably are good to 25-30 amps MAX; it seems that your PA is already exceeding that. Then you tack on a receiver, exciter, etc, and you've gone past the limit for the MICOR supply. Even an MSF5000 supply would be strained to handle that much current; that's why the bigger stations have TWO supplies, one for each PA, and the VHF stations have 28V supplies in them. Solutions? You might consider a battery and a charger that's strong enough to keep the PA happy, to run just the PA. Split everything else off and run that on another smaller supply. Consider a switching regulator supply, rather than a linear regulator supply, to run the rest of the equipment. I know that some of the high power amps are now being built to run on 24-28VDC. This cuts the current consumption in half and they can be run with switching supplies. Let's hope Skip comes aboard here. I know he's had experience with these units. Bob M. ==
Re: [Repeater-Builder] Astron P/S question
Hi Mark, Bypass the gate of the crowbar SCR with .001uF to ground (and put it?very close to the gate).?As mentioned previously,?RF is getting into your crowbar circuit?-- this is a fairly well-known problem. 73, Bob, WA9FBO -Original Message- From: n9wys [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Mon, 8 Dec 2008 10:22 am Subject: RE: [Repeater-Builder] Astron P/S question Hi, Bob. Long time, no chat! The Astron P/S only supplies the PA - all other items in the rack have their own power supplies, but I can still see where I may have exceeded the MICOR supply current limits. Other than that, I've been told to check al the coax jumpers to ensure they are in good order... to eliminate any RF issues. I do access to a 120A switcher that I may try and see what happens. Mark - N9WYS -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Bob M. Sent: Monday, December 08, 2008 9:54 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Astron P/S question I've had DMMs also go nuts at my site too. Luckily the Astron supply hasn't had that problem yet. The fuse usually blows when something catastrophic happens. One such thing is when the output voltage goes too high and the built-in SCR crowbar fires. It shorts the supply immediately, and the excess current usually causes the fuse to blow. Sometimes it also causes the diodes to short out, and they end up blowing the fuse. RF getting back into the supply can trip the SCR. Even RF riding on the supply lines can cause the voltage that the SCR sees to be high enough to trip it, even though it may not show up with a meter or even a scope. You've probably done all you can with the ferrites unless you missed the wires going to the SCR. On some supplies it's mounted to the chassis and has fairly long wires (just waiting to pick up RF) running to it. You'd be better off with ANY kind of unregulated power supply, such as what you had with the MICOR supply. Ferro-resonant transformers usually aren't susceptible to such RF problems, and there's nothing electronic such as a crowbar inside to trip and blow the fuse. This doesn't explain why your MICOR supply blew its fuse, unless you exceeded the output current capability. Most MICORs were only rated up to 100 watts, and the supplies probably are good to 25-30 amps MAX; it seems that your PA is already exceeding that. Then you tack on a receiver, exciter, etc, and you've gone past the limit for the MICOR supply. Even an MSF5000 supply would be strained to handle that much current; that's why the bigger stations have TWO supplies, one for each PA, and the VHF stations have 28V supplies in them. Solutions? You might consider a battery and a charger that's strong enough to keep the PA happy, to run just the PA. Split everything else off and run that on another smaller supply. Consider a switching regulator supply, rather than a linear regulator supply, to run the rest of the equipment. I know that some of the high power amps are now being built to run on 24-28VDC. This cuts the current consumption in half and they can be run with switching supplies. Let's hope Skip comes aboard here. I know he's had experience with these units. Bob M. ==
RE: [Repeater-Builder] Astron P/S question
Will do, Bob. Thanks! 73 de Mark - N9WYS From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Monday, December 08, 2008 12:04 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Astron P/S question Hi Mark, Bypass the gate of the crowbar SCR with .001uF to ground (and put it very close to the gate). As mentioned previously, RF is getting into your crowbar circuit -- this is a fairly well-known problem. 73, Bob, WA9FBO
Re: [Repeater-Builder] Astron P/S question
I had a home built power supply that would shutdown every time that I transmitted on HF. The protection system was a little different and caused the power supply to go into foldback rather than blow the fuse. It required me to shutdown the supply to get it going again. The solution for me was to put a ferrite bead on the gate lead of the SCR and a bypass capacitor directly on the gate to ground on the SCR. This fixed my RF problem. The SCR was rectifying the RF in the gate region causing the SCR to conduct. You may have rectification within the SCR. Hope this helps. 73 Glenn WB4UIV At 10:53 AM 12/8/2008, you wrote: I've had DMMs also go nuts at my site too. Luckily the Astron supply hasn't had that problem yet. The fuse usually blows when something catastrophic happens. One such thing is when the output voltage goes too high and the built-in SCR crowbar fires. It shorts the supply immediately, and the excess current usually causes the fuse to blow. Sometimes it also causes the diodes to short out, and they end up blowing the fuse. RF getting back into the supply can trip the SCR. Even RF riding on the supply lines can cause the voltage that the SCR sees to be high enough to trip it, even though it may not show up with a meter or even a scope. You've probably done all you can with the ferrites unless you missed the wires going to the SCR. On some supplies it's mounted to the chassis and has fairly long wires (just waiting to pick up RF) running to it. You'd be better off with ANY kind of unregulated power supply, such as what you had with the MICOR supply. Ferro-resonant transformers usually aren't susceptible to such RF problems, and there's nothing electronic such as a crowbar inside to trip and blow the fuse. This doesn't explain why your MICOR supply blew its fuse, unless you exceeded the output current capability. Most MICORs were only rated up to 100 watts, and the supplies probably are good to 25-30 amps MAX; it seems that your PA is already exceeding that. Then you tack on a receiver, exciter, etc, and you've gone past the limit for the MICOR supply. Even an MSF5000 supply would be strained to handle that much current; that's why the bigger stations have TWO supplies, one for each PA, and the VHF stations have 28V supplies in them. Solutions? You might consider a battery and a charger that's strong enough to keep the PA happy, to run just the PA. Split everything else off and run that on another smaller supply. Consider a switching regulator supply, rather than a linear regulator supply, to run the rest of the equipment. I know that some of the high power amps are now being built to run on 24-28VDC. This cuts the current consumption in half and they can be run with switching supplies. Let's hope Skip comes aboard here. I know he's had experience with these units. Bob M. == --- On Mon, 12/8/08, n9wys [EMAIL PROTECTED] wrote: From: n9wys [EMAIL PROTECTED] Subject: [Repeater-Builder] Astron P/S question To: Repeater-Builder@yahoogroups.com Date: Monday, December 8, 2008, 10:20 AM For the learned group here  I know there has been some discussion on one the list regarding Astron Power supplies. Unfortunately, searching hasnât revealed what I am looking for, so I pose my query here and apologize in advance if this was a subject that was discussed at length in the past  I will ddescribe my problem in detail, so forgive me for being so verbose right off the bat; but I figure if I provide a lot of info now, it will avoid a lot of question and answer exchanges later in order to get an understanding of my problem.  I have a UHF ham repeater system (TKR-820 as transmitter, MICOR SpectraTAC receiver and comparator, Astron RM-70 Power Supply, and Crescend 150W P/A) that is experiencing issues with the power supply. Seems that when the repeater is on the air for any time (for example, over three minutes key-down) the power supply blows a fuse. The first time this happened, I changed out the P/S with a MICOR supply I had from a 100W continuous duty station. It also blew THAT fuse  The Astron supply that blew the fuse had two bad diodes in the rectifier, so that was repaired. There was nothing found wrong with the Motorola supply, other than the main fuse had blown.  I took the PA back to Crescend, but they found nothing wrong with the P/A.  The station was put back on the air with the repaired Astron supply. Was on the air for about two weeks, and failed again while I was talking to another ham. Went back to the tower and found the fuse blown again in the supply. I took the PA offline and brought it back to Crescend, told them of the issue with the P/S, and that I needed them to check the PA for problems. Their service tech called me and said heâd had the PA running on his workbench as we spoke, and had it transmitting for about 45 minutes with no problems all operating within spec
