[Repeater-Builder] MSR2000 PA out - again...
I have an MSR2000 on 444.550 for the local ham club / county EMA. The PA (a 110W model) is out again. We just had this repaired by the local Motorola shop, with whom we've had very good results from in the past. We're running the PA at about 80W, so I'm thinking we didn't "burn it up", but I can't help but wonder if there is anything inherently wrong with the MSR2000 PA for UHF. This is the third time the PA has failed in this particular machine in about a 2-year time frame. (This was a repeater originally tuned for 460 MHZ, and brought down to the ham band.) This particular machine has been a pain in the @$% - RX sensitivity isn't what it should be, PA keeps going out, etc. Seems like we're up at the site every couple of months do make some sort of repair on it. I'm wondering if we should just cut our losses and get another machine, or should I keep plugging away at this repeater? If we do decide to chuck it, how much can I expect to spend to get a comparable replacement - we use this machine during severe weather season for forwarding reports to the NWS, and it's open other times. We want to add remote RX sites (you've probably seen my inquiries about those in the past) but I don't want to start adding remote RX sites until I get the main repeater working reliably. I'm open to suggestions... Thanks, Mark - N9WYS Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
[Repeater-Builder] MSR2000 PA out - again...
Hello ... Kevin Berlen wrote: ... snip ... > The receiver in your machine is basically a Mitrek. One thing to > look for that can cause intermittent problems are the ground > connections on the coils in the front end casting. The joints can > fracture and cause very intermittent RX sensitivity problems. Don't > over look the two injection filter resonators that are part of this > assembly. Get a friend and a couple LARGE soldering guns and > resolder all of these connections. It will take a large amount of > heat, but make sure that the solder flows properly and that the > entire joint is fluid before you remove the heat. Following this > repair, be prepared to touch up the aligmnment on the front end. This is a serious issue - about 30 years ago, the Motorola UHF Motrac receiver front end castings had a similar problem. The fix I used was to carefully remove the casting from the receiver, take the top plate with the adjustment screws off and set it aside. A trip outside and a propane torch reheating the entire front end assembly, tightening the helical resonator screws and flowing fresh solder on all the connections fixed the problem. Neil - WA6KLA > > I hope this is useful information for you. Good luck, and 73, > > Kevin, K9HX > > At 09:00 AM 9/7/2004 -0500, you wrote: > >I have an MSR2000 on 444.550 for the local ham club / county EMA. > >The PA (a 110W model) is out again. We just had this repaired by > >the local Motorola shop, with whom we've had very good results > >from in the past. We're running the PA at about 80W, so I'm > >thinking we didn't "burn it up", but I can't help but wonder if > >there is anything inherently wrong with the MSR2000 PA for UHF. > >This is the third time the PA has failed in this particular > >machine in about a 2-year time frame. (This was a repeater > >originally tuned for 460 MHZ, and brought down to the ham band.) > >This particular machine has been a pain in the @$% - RX > >sensitivity isn't what it should be, PA keeps going out, etc. > >Seems like we're up at the site every couple of months do make > >some sort of repair on it. > >I'm wondering if we should just cut our losses and get another > >machine, or should I keep plugging away at this repeater? If we > >do decide to chuck it, how much can I expect to spend to get a > >comparable replacement - we use this machine during severe weather > >season for forwarding reports to the NWS, and it's open other > >times. We want to add remote RX sites (you've probably seen my > >inquiries about those in the past) but I don't want to start > >adding remote RX sites until I get the main repeater working > >reliably. > >I'm open to suggestions... > >Thans, > >Mark - N9WYS > > > Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
RE: [Repeater-Builder] MSR2000 PA out - again...
Have you done any troubleshooting yourself to find out what is failing. Did you go thru the troubleshooting routine in the manual. I've found that MSR amps are very good and only fail very rarely. I've seen the Choke feeding the power to the mid level amps have a bad connection...you'll read the voltage on the collectors in idle, but when you go to TX the voltage will go away. I've seen this on a number of amps of the 2000 series. I've also seen people repair these by replacing the transistors in the mid level amp, and of course it works for a while because they disturbed the choke and got a decent connection again. But the only real way to repair it is to remove the board and remove the choke and clean the leads and reinstall it and make sure it is well soldered. Gregg R. Lengling, W9DHI, Retired Administrator http://www.milwaukeehdtv.org K2/100 S#3075 KX1 S# 57 Member: ARRL, RSGB, RCA, WERA and ORC -Original Message- From: N9WYS [mailto:[EMAIL PROTECTED] Sent: Tuesday, September 07, 2004 9:01 AM To: Repeater-Builder@yahoogroups.com; [EMAIL PROTECTED] Subject: [Repeater-Builder] MSR2000 PA out - again... I have an MSR2000 on 444.550 for the local ham club / county EMA. The PA (a 110W model) is out again. We just had this repaired by the local Motorola shop, with whom we've had very good results from in the past. We're running the PA at about 80W, so I'm thinking we didn't "burn it up", but I can't help but wonder if there is anything inherently wrong with the MSR2000 PA for UHF. This is the third time the PA has failed in this particular machine in about a 2-year time frame. (This was a repeater originally tuned for 460 MHZ, and brought down to the ham band.) This particular machine has been a pain in the @$% - RX sensitivity isn't what it should be, PA keeps going out, etc. Seems like we're up at the site every couple of months do make some sort of repair on it. I'm wondering if we should just cut our losses and get another machine, or should I keep plugging away at this repeater? If we do decide to chuck it, how much can I expect to spend to get a comparable replacement - we use this machine during severe weather season for forwarding reports to the NWS, and it's open other times. We want to add remote RX sites (you've probably seen my inquiries about those in the past) but I don't want to start adding remote RX sites until I get the main repeater working reliably. I'm open to suggestions... Thanks, Mark - N9WYS Yahoo! Groups Links Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
RE: [Repeater-Builder] MSR2000 PA out - again...
Hmmm... Interesting. I'd have thought that since we sent the PA out for repair to the MSS, they'd have checked the whole thing for proper operation, on our freq, before sending it back, but I'll check that out. Thanks! Mark - N9WYS -Original Message- From: W9DHI [mailto:[EMAIL PROTECTED] Sent: Tuesday, September 07, 2004 9:43 AM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] MSR2000 PA out - again... Have you done any troubleshooting yourself to find out what is failing. Did you go thru the troubleshooting routine in the manual. I've found that MSR amps are very good and only fail very rarely. I've seen the Choke feeding the power to the mid level amps have a bad connection...you'll read the voltage on the collectors in idle, but when you go to TX the voltage will go away. I've seen this on a number of amps of the 2000 series. I've also seen people repair these by replacing the transistors in the mid level amp, and of course it works for a while because they disturbed the choke and got a decent connection again. But the only real way to repair it is to remove the board and remove the choke and clean the leads and reinstall it and make sure it is well soldered. Gregg R. Lengling, W9DHI, Retired Administrator http://www.milwaukeehdtv.org K2/100 S#3075 KX1 S# 57 Member: ARRL, RSGB, RCA, WERA and ORC -Original Message- From: N9WYS [mailto:[EMAIL PROTECTED] Sent: Tuesday, September 07, 2004 9:01 AM To: Repeater-Builder@yahoogroups.com; [EMAIL PROTECTED] Subject: [Repeater-Builder] MSR2000 PA out - again... I have an MSR2000 on 444.550 for the local ham club / county EMA. The PA (a 110W model) is out again. We just had this repaired by the local Motorola shop, with whom we've had very good results from in the past. We're running the PA at about 80W, so I'm thinking we didn't "burn it up", but I can't help but wonder if there is anything inherently wrong with the MSR2000 PA for UHF. This is the third time the PA has failed in this particular machine in about a 2-year time frame. (This was a repeater originally tuned for 460 MHZ, and brought down to the ham band.) This particular machine has been a pain in the @$% - RX sensitivity isn't what it should be, PA keeps going out, etc. Seems like we're up at the site every couple of months do make some sort of repair on it. I'm wondering if we should just cut our losses and get another machine, or should I keep plugging away at this repeater? If we do decide to chuck it, how much can I expect to spend to get a comparable replacement - we use this machine during severe weather season for forwarding reports to the NWS, and it's open other times. We want to add remote RX sites (you've probably seen my inquiries about those in the past) but I don't want to start adding remote RX sites until I get the main repeater working reliably. I'm open to suggestions... Thanks, Mark - N9WYS Yahoo! Groups Links Yahoo! Groups Links Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] MSR2000 PA out - again...
I have limited experience with the MSR2000 however if the PA keeps toasting, and if RX sensitivity is low ( MSR2000's were not super hot to start with) I would suspect the load being presented to the transmitter may have high swr. (Like maybe duplexer, maybe the Isolator ) That would seem to be the place I would start...It is possible these factory parts may not be re-tuned properly and/or like operation at 444 mhz. In general I know of one here ( MSR2000) in Cleveland on 444.xxx which has never toasted a PA to my knowledge... While it has limitations due to the general design, as far as replacing the Duplexer and Isolator with lower insertion loss versions, it has been serving well for a long time. Even if the duplexer was mis-tuned, it would seem like the Isolator should protect the transmitter... Is it possible it is taking lightning strikes or severe discharges That would seem more likely, although damage should occur to more things... Doug Bade Cleveland Comms. At 10:00 AM 9/7/2004, you wrote: >I have an MSR2000 on 444.550 for the local ham club / county EMA. The PA (a >110W model) is out again. We just had this repaired by the local Motorola >shop, with whom we've had very good results from in the past. We're running >the PA at about 80W, so I'm thinking we didn't "burn it up", but I can't >help but wonder if there is anything inherently wrong with the MSR2000 PA >for UHF. This is the third time the PA has failed in this particular >machine in about a 2-year time frame. (This was a repeater originally tuned >for 460 MHZ, and brought down to the ham band.) This particular machine has >been a pain in the @$% - RX sensitivity isn't what it should be, PA keeps >going out, etc. Seems like we're up at the site every couple of months do >make some sort of repair on it. >I'm wondering if we should just cut our losses and get another machine, or >should I keep plugging away at this repeater? If we do decide to chuck it, >how much can I expect to spend to get a comparable replacement - we use this >machine during severe weather season for forwarding reports to the NWS, and >it's open other times. We want to add remote RX sites (you've probably seen >my inquiries about those in the past) but I don't want to start adding >remote RX sites until I get the main repeater working reliably. >I'm open to suggestions... >Thanks, >Mark - N9WYS Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] MSR2000 PA out - again...
I must agree with Doug. There is very likely an unfavorable load presented to the PA, and it manifests its displeasure by burning up! Most of us (me included) do the initial tune-up of a commercial transmitter with a Bird 45 wattmeter feeding a good 50 ohm dummy load. Transistorized PAs adore dummy loads, because they are resistive. By definition, such loads are broadband- often from DC to 1 GHz- and the PA is "comfortable" with such a laid-back, non-confrontational, non-reactive sink for its RF power. Ah, but the Real World (duplexers, isolators, and antennas) are not so forgiving; they are REACTIVE! By definition, such RF devices present different impedances at different frequencies. We should not be surprised that a PA that works (or SEEMS to work) perfectly into a dummy load for hours on end, suddenly goes belly-up when feeding a highly reactive load such as a duplexer. HELLO? A duplexer is the quintessential unstable load for a PA, and it seldom presents a 50 ohm load at any frequency. Although the use of impedance matchers has been hotly debated in these pages, along with recipes for cutting cables to "magic" lengths, we must acknowledge the fact that any PA that works perfectly into a precise 50 ohm load, "may" not work perfectly- or even close- when presented a reactive load. So, let's improve our odds! The first step, especially when dealing with a solid-state PA, is to adjust its output impedance to properly match a 50 ohm load. I don't care if you do this with a Z-matcher or with laborious cut-and-try cable lengths, it's a step in the right direction. The second step is to ensure that the next component seen by the PA, whether an isolator or a duplexer, is tuned for a 50 ohm source. Despite passionate denials by some "experts," you cannot tune a duplexer to match a wayward impedance. All adjustments on a duplexer affect its frequency response, and since the frequency is not going to change, neither should the tuning of a duplexer be tinkered with. A lot of my work is undoing the "tweaking" performed by self-styled experts who sincerely believe that a duplexer can be tuned to a PA. NOT! The results prove my point, and are supported by those firms that make duplexers. The bottom line is that a well-made, commercial-grade PA should not die unless something is very, very wrong. I can live with the rare death due to natural causes, but repeated toastings... NOT! 73, Eric Lemmon WB6FLY Doug Bade wrote: > > I have limited experience with the MSR2000 however if the PA keeps > toasting, and if RX sensitivity is low ( MSR2000's were not super hot to > start with) I would suspect the load being presented to the transmitter may > have high swr. (Like maybe duplexer, maybe the Isolator ) That would seem > to be the place I would start...It is possible these factory parts may not > be re-tuned properly and/or like operation at 444 mhz. In general I know of > one here ( MSR2000) in Cleveland on 444.xxx which has never toasted a PA to > my knowledge... While it has limitations due to the general design, as far > as replacing the Duplexer and Isolator with lower insertion loss versions, > it has been serving well for a long time. Even if the duplexer was > mis-tuned, it would seem like the Isolator should protect the > transmitter... Is it possible it is taking lightning strikes or severe > discharges That would seem more likely, although damage should occur to > more things... > > Doug Bade > Cleveland Comms. > > At 10:00 AM 9/7/2004, you wrote: > >I have an MSR2000 on 444.550 for the local ham club / county EMA. The PA (a > >110W model) is out again. We just had this repaired by the local Motorola > >shop, with whom we've had very good results from in the past. We're running > >the PA at about 80W, so I'm thinking we didn't "burn it up", but I can't > >help but wonder if there is anything inherently wrong with the MSR2000 PA > >for UHF. This is the third time the PA has failed in this particular > >machine in about a 2-year time frame. (This was a repeater originally tuned > >for 460 MHZ, and brought down to the ham band.) This particular machine has > >been a pain in the @$% - RX sensitivity isn't what it should be, PA keeps > >going out, etc. Seems like we're up at the site every couple of months do > >make some sort of repair on it. > >I'm wondering if we should just cut our losses and get another machine, or > >should I keep plugging away at this repeater? If we do decide to chuck it, > >how much can I expect to spend to get a comparable replacement - we use this > >machine during severe weather season for forwarding reports to the NWS, and > >it's open other times. We want to add remote RX sites (you've probably seen > >my inquiries about those in the past) but I don't want to start adding > >remote RX sites until I get the main repeater working reliably. > >I'm open to suggestions... > >Thanks, > >Mark - N9WYS > > > Yahoo! Groups Links > > > > Ya
Re: [Repeater-Builder] MSR2000 PA out - again...
I have repaired exactly the same problem in two VHF amps, and in one UHF MSR-2000, the problem is in the feedtrough that carries the + side of voltage, seems it gets very hot at high power level and melt the solder . Juan - Mensaje original - De: W9DHI Para: Repeater-Builder@yahoogroups.com Enviado: Tuesday, September 07, 2004 7:43 AM Asunto: RE: [Repeater-Builder] MSR2000 PA out - again... Have you done any troubleshooting yourself to find out what is failing. Didyou go thru the troubleshooting routine in the manual. I've found that MSRamps are very good and only fail very rarely. I've seen the Choke feedingthe power to the mid level amps have a bad connection...you'll read thevoltage on the collectors in idle, but when you go to TX the voltage will goaway. I've seen this on a number of amps of the 2000 series. I've alsoseen people repair these by replacing the transistors in the mid level amp,and of course it works for a while because they disturbed the choke and gota decent connection again. But the only real way to repair it is to removethe board and remove the choke and clean the leads and reinstall it and makesure it is well soldered.Gregg R. Lengling, W9DHI, RetiredAdministrator http://www.milwaukeehdtv.orgK2/100 S#3075 KX1 S# 57Member: ARRL, RSGB, RCA, WERA and ORC -Original Message-From: N9WYS [mailto:[EMAIL PROTECTED] Sent: Tuesday, September 07, 2004 9:01 AMTo: Repeater-Builder@yahoogroups.com; [EMAIL PROTECTED]Subject: [Repeater-Builder] MSR2000 PA out - again...I have an MSR2000 on 444.550 for the local ham club / county EMA. The PA (a110W model) is out again. We just had this repaired by the local Motorolashop, with whom we've had very good results from in the past. We're runningthe PA at about 80W, so I'm thinking we didn't "burn it up", but I can'thelp but wonder if there is anything inherently wrong with the MSR2000 PAfor UHF. This is the third time the PA has failed in this particularmachine in about a 2-year time frame. (This was a repeater originally tunedfor 460 MHZ, and brought down to the ham band.) This particular machine hasbeen a pain in the @$% - RX sensitivity isn't what it should be, PA keepsgoing out, etc. Seems like we're up at the site every couple of months domake some sort of repair on it.I'm wondering if we should just cut our losses and get another machine, orshould I keep plugging away at this repeater? If we do decide to chuck it,how much can I expect to spend to get a comparable replacement - we use thismachine during severe weather season for forwarding reports to the NWS, andit's open other times. We want to add remote RX sites (you've probably seenmy inquiries about those in the past) but I don't want to start addingremote RX sites until I get the main repeater working reliably.I'm open to suggestions...Thanks,Mark - N9WYS Yahoo! Groups Links Yahoo! Groups Links<*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/<*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED]<*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/ Yahoo! Groups Links To visit your group on the web, go to:http://groups.yahoo.com/group/Repeater-Builder/ To unsubscribe from this group, send an email to:[EMAIL PROTECTED] Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.
Re: [Repeater-Builder] MSR2000 PA out - again...
There were two different PA decks on the MSR2000. One that was rated for continous duty and one that was not. The non-continous duty UHF PA is a real problem. It is not at all unusual to have cronic problems with it. The DC distribution is done on a circuit board that runs under the PA modules. The DC is broght up to the modules by way of jumpers made from square wire. The connection between the DC distribution board and these squre wires is very problematic. The only way to fix it is to completely disassemble to PA deck, desolder every connection, clean everything, and then resolder all of the connections using silver solder. This is a very involved job, and will result in a PA deck that will work for a few years before it is necessary to repeat the repair again. Another problem area is the interconnection straps between the various stages in the PA. Each strap should have a small "hump" in it. In other words, it should not be a flat strap between the substrates. The "hump" will allow for small amounts of movement between the substrates as the PA deck heats and cools. If you have the flat straps, the solder connections will eventually fail and the connections will be intermittent. The receiver in your machine is basically a Mitrek. One thing to look for that can cause intermittent problems are the ground connections on the coils in the front end casting. The joints can fracture and cause very intermittent RX sensitivity problems. Don't over look the two injection filter resonators that are part of this assembly. Get a friend and a couple LARGE soldering guns and resolder all of these connections. It will take a large amount of heat, but make sure that the solder flows properly and that the entire joint is fluid before you remove the heat. Following this repair, be prepared to touch up the aligmnment on the front end. I hope this is useful information for you. Good luck, and 73, Kevin, K9HX At 09:00 AM 9/7/2004 -0500, you wrote: >I have an MSR2000 on 444.550 for the local ham club / county EMA. The PA (a >110W model) is out again. We just had this repaired by the local Motorola >shop, with whom we've had very good results from in the past. We're running >the PA at about 80W, so I'm thinking we didn't "burn it up", but I can't >help but wonder if there is anything inherently wrong with the MSR2000 PA >for UHF. This is the third time the PA has failed in this particular >machine in about a 2-year time frame. (This was a repeater originally tuned >for 460 MHZ, and brought down to the ham band.) This particular machine has >been a pain in the @$% - RX sensitivity isn't what it should be, PA keeps >going out, etc. Seems like we're up at the site every couple of months do >make some sort of repair on it. >I'm wondering if we should just cut our losses and get another machine, or >should I keep plugging away at this repeater? If we do decide to chuck it, >how much can I expect to spend to get a comparable replacement - we use this >machine during severe weather season for forwarding reports to the NWS, and >it's open other times. We want to add remote RX sites (you've probably seen >my inquiries about those in the past) but I don't want to start adding >remote RX sites until I get the main repeater working reliably. >I'm open to suggestions... >Thanks, >Mark - N9WYS > > > > > > > >Yahoo! Groups Links > > > > Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
RE: [Repeater-Builder] MSR2000 PA out - again...
Thanks, everyone!! I have several items to check now, thanks to all of the suggestions provided to date. My main problem is with the location - the custodians there are not "overly friendly" when we show up to affix repairs or perform maintenance. Until lately, we overlooked that - given the fact that we were provided space gratis. However, we are currently investigating the relocation of the machine - to allow us better access if/when we need to make future repairs. (Current repairs will have to be done with the cooperation of the site owners...so it may take a while. Long story, and I don't want to elaborate here.) I have printed out all of these messages, so I can have them at the site for reference. As soon as I know what is happening, I'll report back with the findings and resolutions. Thanks again! Mark - N9WYS Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
