VHF Quantro PA fail problems
Posted: Thu Jan 15, 2015 12:06 pm
Hi guys I need some help if anyone is experienced with 350W VHF high power Quantros.
We picked up several of the recently available VHF Quantros that have been floating around, and put one of them to use on our local 2-meter repeater. It replaced a high power Micor (B93RCB) and has the analog remote receivers voted on a Digitac and coming in the MRTI (phone) interface on the Quantro, and uses the local in-cabinet receiver as it's P25 input.
This gave us dual-mode with analog voted receivers, and one local P25 receiver. It worked great, but we started to develop some weird and elusive PA fail type of problems.
It seemed like it worked flawlessly for a few weeks, but I could be wrong there. Then we started getting some "double-beeps" PA fail alarms, which seemed to later degenerate into intermittent hard PA fails where the transmitter totally drops briefly.
It might run clean for a day, then suddenly there is a rash of double-beep power alarms cutting back to half power, and then sometimes even total drops. When we just get the double-beep and half power, the logged error is "Driver overdrive alarm" and when the transmitter totally drops we get "PA no forward power alarms". Sometimes there is some "bad HC11 opcode" stuff in there too, but I am not sure if that is significant or not.
Station firmware was version 9 something and we had programmed with with RSS version 14 something, so we felt it was a good idea to update everything to the last and final version, which we did.
A lot of goofy stuff surrounding these boxes. RSS instruction manual says when calibrating the power out, you should bypass the circulator when performing the power calibration, then reconnect it when done, and program the station for 40 more watts than you expect out. But the PA won't calibrate with the circulator disconnected, it complains of a high VSWR alarm and won't calibrate. The funny thing is the circulator does not provide a VSWR sense, only a circulator dummy load temperature thermistor. I can't see why removing the circulator and replacing it with a N-barrel would cause an SWR alarm, and in any event, the reflected power voltage read by the SCM didn't seem to go up any when the barrel was in.
So I gave up on bypassing the circulator and just went back to common sense and just calibrated the thing with the circulator connected and it seemed to work fine.
Another thing bugging me is there is no schematic of the TLD2742B PA or the TLD2770B driver PA in the Quantro manual. Every other module in the station is there, but the VHF PAs are just not there. Only block diagrams. The UHF PAs are there, but not the VHF. I wonder if I would find them in the MSF manual?
I am starting to wonder if I have an AC problem with this beast. It is on a 20A outlet, and it did trip the breaker once when I was working on it. Geez, this darn thing can put out 600 watts if you let the control voltage get out of hand. (not sure for how long that would hold but it's quite impressive)
Also, we have a bunch of these so we have swapped EVERYTHING at least once and maybe even multiple times and just can't get these PA fail alarms to go away. And I am pretty convinced there is nothing wrong with any of the hardware. All these stacks of SCMs, exciters, PAs, power supplies, Quantar chassies - geez they all can't be bad!
I am down to two things now that I have put the last and final firmware version in. Either I still am not getting the PA calibrated correctly, or it is some kind of voltage sag on the AC line maybe because of current draw.
Anybody else struggle with these 350W VHF stations and getting them to run clean without PA fail alarms? They seem awful touchy, unlike a regular Quantar which is bullet-proof.
thanks!
We picked up several of the recently available VHF Quantros that have been floating around, and put one of them to use on our local 2-meter repeater. It replaced a high power Micor (B93RCB) and has the analog remote receivers voted on a Digitac and coming in the MRTI (phone) interface on the Quantro, and uses the local in-cabinet receiver as it's P25 input.
This gave us dual-mode with analog voted receivers, and one local P25 receiver. It worked great, but we started to develop some weird and elusive PA fail type of problems.
It seemed like it worked flawlessly for a few weeks, but I could be wrong there. Then we started getting some "double-beeps" PA fail alarms, which seemed to later degenerate into intermittent hard PA fails where the transmitter totally drops briefly.
It might run clean for a day, then suddenly there is a rash of double-beep power alarms cutting back to half power, and then sometimes even total drops. When we just get the double-beep and half power, the logged error is "Driver overdrive alarm" and when the transmitter totally drops we get "PA no forward power alarms". Sometimes there is some "bad HC11 opcode" stuff in there too, but I am not sure if that is significant or not.
Station firmware was version 9 something and we had programmed with with RSS version 14 something, so we felt it was a good idea to update everything to the last and final version, which we did.
A lot of goofy stuff surrounding these boxes. RSS instruction manual says when calibrating the power out, you should bypass the circulator when performing the power calibration, then reconnect it when done, and program the station for 40 more watts than you expect out. But the PA won't calibrate with the circulator disconnected, it complains of a high VSWR alarm and won't calibrate. The funny thing is the circulator does not provide a VSWR sense, only a circulator dummy load temperature thermistor. I can't see why removing the circulator and replacing it with a N-barrel would cause an SWR alarm, and in any event, the reflected power voltage read by the SCM didn't seem to go up any when the barrel was in.
So I gave up on bypassing the circulator and just went back to common sense and just calibrated the thing with the circulator connected and it seemed to work fine.
Another thing bugging me is there is no schematic of the TLD2742B PA or the TLD2770B driver PA in the Quantro manual. Every other module in the station is there, but the VHF PAs are just not there. Only block diagrams. The UHF PAs are there, but not the VHF. I wonder if I would find them in the MSF manual?
I am starting to wonder if I have an AC problem with this beast. It is on a 20A outlet, and it did trip the breaker once when I was working on it. Geez, this darn thing can put out 600 watts if you let the control voltage get out of hand. (not sure for how long that would hold but it's quite impressive)
Also, we have a bunch of these so we have swapped EVERYTHING at least once and maybe even multiple times and just can't get these PA fail alarms to go away. And I am pretty convinced there is nothing wrong with any of the hardware. All these stacks of SCMs, exciters, PAs, power supplies, Quantar chassies - geez they all can't be bad!
I am down to two things now that I have put the last and final firmware version in. Either I still am not getting the PA calibrated correctly, or it is some kind of voltage sag on the AC line maybe because of current draw.
Anybody else struggle with these 350W VHF stations and getting them to run clean without PA fail alarms? They seem awful touchy, unlike a regular Quantar which is bullet-proof.
thanks!