Quantar PA Fail Issue. Any Advice

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MrQRO
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Quantar PA Fail Issue. Any Advice

Post by MrQRO »

Hi Folks,
I just purchased a Quantar a few weeks ago to set up for dual-mode use and IRLP to replace our old MSR2K unit.
Took a few days to get it all programmed up and working with the GM300 we are using for our IRLP link.
During the course of the reprogramming and testing I set the PA output down to 20W, and had it working into a good dummy load.

About the time I had everything working fine and all set up as far as wildcards, and PL options, etc. I started to notice that when I would try to
key the repeater the PA would indicate PA Fail on the front panel. I also noticed no power out through the Bird at the dummyload.

The messages I’m getting on the status screen are:

INT_WM_VSWR_ALARM
INT_WM_FWD_PWR_ALARM

Which if I’m reading the manual correctly is between the IPA and FPA, NOT the FPA, and the ANTenna (then it would be an EXT_ alarm?).
The manual also says this can be caused because you have to go through the power alignment procedure, so I set the power back to the 80W
output that it was originally set to when I got the unit, and tried to do the alignment, but as soon as I do "PA Init", the Red LED comes on/PA Fail
is expressed, and I can't go into keydown.

My gut tells me that the PA unit isn't fried, since it worked fine through all the work I did, and I took all proper precautions to protect it, so am I
having wishful dilusions, and I toasted it, or am I missing something that may have gotten out of adj., or confused in SW, and I need to do something to
get it back on track again?

Mike - N3EAQ
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Bill_G
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Re: Quantar PA Fail Issue. Any Advice

Post by Bill_G »

Check your cables and dummy load.
MrQRO
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Re: Quantar PA Fail Issue. Any Advice

Post by MrQRO »

Obviously the 1st thing I did, along with reseating the cards, cleaning and checking the edge connectors, checking the output voltage from the supply, the output from the exciter and it's jumper cable, etc. and all the easy stuff.

I probably should have put that in the original post. Sorry.

This is something more complicated than that.
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Astro Spectra
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Re: Quantar PA Fail Issue. Any Advice

Post by Astro Spectra »

I would check that the PA P/N matches the station config.
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Bill_G
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Re: Quantar PA Fail Issue. Any Advice

Post by Bill_G »

Have you opened up the rfpa to see if the solder connection to the ant port has burnt open?
MrQRO
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Re: Quantar PA Fail Issue. Any Advice

Post by MrQRO »

Yes, it's the correct P/N for the station. as I said, it was working fine previously. Yes, I did open the PA and all looks fine inside, I examined all the components and connections under my bench scope and don't see anything burnt, or broken. As I mentioned in the original post the messages are coming back as INT not EXT, which would point toward an issue between the Intermediate PA and the Final PA, rather than the FPA and the antenna. The maual tends to point to an alignment issue in the cases when these alarm/status messages are being issued. I was hoping someone had seen a similar situation where somehow the software, or codepulg had gotten out of "sync" with the PA, and it was going into fail. (My gut is telling me that the PA is being told to go to power X via Vcont/Vomni and is actually going to Power Y, and the mismatch is being read as a fail), or again, maybe that's all just wishful thinking on my part!

As I mentioned I've checked all the physical possibilities short of actual failed components on the PA that are not visibly damaged, or hands-on metering. I do have a list of voltages from the RSS metering screen for the PA in both keyed, and deykeyd state if that would be of use to anyone. The manual even suggest that these messages can be caused by a WL board, but I fail to see how that can be involved, anyone know how a WL can affect INT_WM_VSWR_ALARM and INT_WM_FWD_PWR_ALARM? I even tried pulling the WL card and setting the codeplug to WL=NONE

Thanks for the suggestions. Any other input is welcome!
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d119
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Re: Quantar PA Fail Issue. Any Advice

Post by d119 »

The station contains internal metering for both forward and reflected power that are continuously monitored by the station control board.

INT_WM_VSWR_ALARM indicates there is a VSWR problem along the transmit antenna network.

INT_WM_FWD_PWR_ALARM indicates that there is insufficient forward power to the antenna network.

I just powered up my known-good Quantar test station here at work and keyed it up with nothing connected to either antenna port on it. The result was that the station keyed up, gave me the two-beep PA alarm and indicated "PA Low" on the exciter, not "PA Fail".

Now I'm not that experienced with failures on 900MHz stations, but I would think that station behavior would be identical between bands. You've most definitely got an issue somewhere in either the exciter or the PA.

I would start looking more closely at the exciter. Have you attempted to realign the station?
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fineshot1
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Re: Quantar PA Fail Issue. Any Advice

Post by fineshot1 »

I did not know you could set a 100w quantar pa down to 20w.

I have always been advised by the moto and mss techs to never try
setting a higher power pa lower than half its rated output. They
never did provide any details as to what would happen but i always
took heed of what they were telling me and i never had a need to
try lowering any of them lower than 80 or 90w.
fineshot1
NJ USA
MrQRO
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Re: Quantar PA Fail Issue. Any Advice

Post by MrQRO »

Yeah, I was probably a DA for setting it down to 20W. The universal opinion seems to be that this is a bad thing to do. Although the RSS wil let you do it, you probably should NOT!
Mistake #1....

I've set it back to the 80W that it was originally set for, and working at, but now I can't seem to go through the alignment. As soon as I try I get "PA Fail" and can go no farther.
As per the manual, I should be able to do a "PA Init" w/ RSS, and try again, but PA Init doesn't do squat any more... The LED stays in PA fail.

I've tried to fake-out the alignment and put in 80W, did an adjust and save, but that doesn't get me anywhere either...

Here's how I understand operation.... The exciter sends V_cont to the PA, which gets turned into V_omni* that is fed back to the Exciter. The Exciter then compares this with Tx_VF.
If the PA cant put out the selected power, ultimately V_cont (V_omni*) goes to MAX, and the exciter shuts down drive.

I've put my monitor set on the RF out of the exciter (20mW), and I see that now nothing comes out of the exciter on keydown. i.e., it's RF switch is immediately set OFF.
So, of course the PA will have no Tx_VF, since it's not being driven. I guess I need to resign myself to the fact that the exciter, or PA (or both) are toast.. I can't quite fathom why.
Since I took good precautions, AND the PA has the circulator that will shunt bad VSWR to 50 ohm load in case of mismatch, but I've tried everything, and it seems I'm stuck!

If anyone has an idea, let me know. Other wise I'm looking for a Quantar PA, and/or exciter for UHF range 2.....

Grrrrrr.

M. K. Hess - N3eaq
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xmo
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Re: Quantar PA Fail Issue. Any Advice

Post by xmo »

"... Quantar PA, and/or exciter for UHF range 2.."

That being the case - this thread is in the wrong forum - this one is for 900.
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d119
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Re: Quantar PA Fail Issue. Any Advice

Post by d119 »

I think he's stating that if he cannot fix this, he wants to convert the station to UHF R2.

I've got UHF R2 and VHF R1 Quantars, both with 110W/125W PA's respectively, on my desk at work for testing, and I have them both set to 20W TX. I've never experienced anything screwy with them, and I've had them on some LONG keydowns for fan/PA testing.

We have a few 800MHz Data stations out there with 100W PA's in them set to about 35W TX. They just loaf along, we've not seen any trouble with them.
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N4DES
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Re: Quantar PA Fail Issue. Any Advice

Post by N4DES »

I found that the VHF Quantar's do not like anything under 20 to 25 watts if it is a high power PA.
I don't remember the UHF limitiations, but I'm sure it is close to that.

What I have is a high power VHF Quantar set at around 30 watts into a 3db attenuator/load feeding into a 150 Watt VoCom amp that put out around a buck 40 with around 15 watts in. The amp has been a workhorse for years and the Quantar just hums right along and happy at 30 watts. If something should happen to the VoCom I can take it out of the equation and turn up the Quantar PA to 100 watts and no one will know the difference.
MrQRO
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Re: Quantar PA Fail Issue. Any Advice

Post by MrQRO »

Thanks guys for the observations. It would sound like running it at 20W should not have caused me harm after all.
Is there a way to run the unit without the PA? I'd like to reliably test to see what the output of the exciter is. But, with the unit going into
immediate PA fail I can't get a reading from the Exciter output. I assume that I'm correct that if the exciter isn't putting out 20mW this
could be causing my issue as well.

As of now I am NOT reading 20mW (+13dBm) out of the port w/ my station monitor, but I believe that's because it goes into immediate fail.
Anyone know if/how I can pull the PA, but still make the station happy so I can test this?

Mike
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xmo
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Re: Quantar PA Fail Issue. Any Advice

Post by xmo »

There are other Quantar family products that use different PA types such as the Quantro which has an MSF style PA and the PDR3500 which uses a Spectra PA.

You could look in the manual for one of those [e.g. PDR = 6881093C75] to see how they make the exciter happy without a 'real' Quantar PA.
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kcbooboo
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Re: Quantar PA Fail Issue. Any Advice

Post by kcbooboo »

The Nucleus transmitter has a "PA TEST MODE" which will let the PA key up even with a failure or error. I don't know if the Quantar has a similar mode. It's a toggle (on/off). When on, one of the LEDs on the exciter will blink. This might let you do some measurements without the station immediately de-keying due to the fault. You must manually reset it when done.

Bob M.
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Re: Quantar PA Fail Issue. Any Advice

Post by Astro Spectra »

A Quantar will work without a PA fitted, generating the correct drive from the transmitter in my experience. You will get heaps of errors, but what can work will.
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Re: Quantar PA Fail Issue. Any Advice

Post by Will »

What is the spec for UR2 110 watt PA for minimum power.
MrQRO
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Re: Quantar PA Fail Issue. Any Advice

Post by MrQRO »

The Quantar has such a "test mode" as well, but if I key the PA either externaly w/ an HT, or internally w/ the keydown command the PA just goes to solid red PA_Fail.

I also have an 800MHz Quantro, and honestly I don't know how they get away w/ doing things the way they do it on that unit. I note there is a backplane cable/plug on the Quantro
that goes from the "remote" PA to the exciter/main backplain, so that probably "fakes out" the system.

Thanks all.

MK
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kcbooboo
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Re: Quantar PA Fail Issue. Any Advice

Post by kcbooboo »

Isn't the PA an external device on the Quantro? If so, that extra cable carries the FWD/REV power signals back to the main chassis so it can monitor and control the output power. When the PA is internal to the main chassis, those signals come out of the PA and ride along the backplane directly, with no external cable.

Now, if your station is programmed to use an EXTERNAL wattmeter and you don't have one, that could certainly trigger a PA FAIL, because the controller won't be looking at the internal PA's FWD/REV power signals but will be looking for them to come in via the external connector.

Bob M.
MrQRO
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Re: Quantar PA Fail Issue. Any Advice

Post by MrQRO »

No, my QUANTAR, is set for NO external wattmeter. Yes, the PA is external on the Quantro.
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batdude
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Re: Quantar PA Fail Issue. Any Advice

Post by batdude »

i would try a new SCM and see if that fixes the problem.

i have seen some wierd crap on quantar stations... and i don't even deal with them that often.


i suspect you have some kind of logic problem or a firmware mismatch (somehow)


d
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The Pager Geek
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Re: Quantar PA Fail Issue. Any Advice

Post by The Pager Geek »

MrQRO wrote:Hi Folks,
I just purchased a Quantar a few weeks ago to set up for dual-mode use and IRLP to replace our old MSR2K unit.
Took a few days to get it all programmed up and working with the GM300 we are using for our IRLP link.
During the course of the reprogramming and testing I set the PA output down to 20W, and had it working into a good dummy load.

About the time I had everything working fine and all set up as far as wildcards, and PL options, etc. I started to notice that when I would try to
key the repeater the PA would indicate PA Fail on the front panel. I also noticed no power out through the Bird at the dummyload.

The messages I’m getting on the status screen are:

INT_WM_VSWR_ALARM
INT_WM_FWD_PWR_ALARM

Which if I’m reading the manual correctly is between the IPA and FPA, NOT the FPA, and the ANTenna (then it would be an EXT_ alarm?).
The manual also says this can be caused because you have to go through the power alignment procedure, so I set the power back to the 80W
output that it was originally set to when I got the unit, and tried to do the alignment, but as soon as I do "PA Init", the Red LED comes on/PA Fail
is expressed, and I can't go into keydown.

My gut tells me that the PA unit isn't fried, since it worked fine through all the work I did, and I took all proper precautions to protect it, so am I
having wishful dilusions, and I toasted it, or am I missing something that may have gotten out of adj., or confused in SW, and I need to do something to
get it back on track again?

Mike - N3EAQ
Could you humor me with the Firmware information of the station, and what CSS/RSS you are using?

tpg
Experienced Provider of Useless Information
MrQRO
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Re: Quantar PA Fail Issue. Any Advice

Post by MrQRO »

Station Ctrl Firmware(FW) = R022.10.080 Station WL FW = R020.10.025
Station Exciter FW = R020.09.005 Station Boot2 FW = R020.10.016 Station
Boot1 FW = R020.10.008 Codeplug Version = 14 WinRSS Version R14.10.00

As as aside for everyone, I just swapped PAs with a loaned from a friend... No difference! Exact same symptoms. Going to try swapping the Exciter next.
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The Pager Geek
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Re: Quantar PA Fail Issue. Any Advice

Post by The Pager Geek »

I'm leaning towards a CSS version / firmware mismatch. You are using version 14 programming software to program the station codeplug and change tuning values. Version 10 firmware hasn't learned what CSS 14 is talking about yet. I've seen a ton of issues personally with this type of configuration.

A key factor in this is... it only started getting pissed once you began to program and make changes via CSS.

Food for thought...

tpg
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MrQRO
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Re: Quantar PA Fail Issue. Any Advice

Post by MrQRO »

Hello All,

Well It looks like I found the issue!!!
I popped in a loaner Exciter, and the problem went away!
If you'd like to see my discussion and root cause analysis of the issue... Go to:

http://www.kias.org/Quantar.htm

I loaded it to my web site rather than try to format it all for BBS consumtion, etc.
Still not convinced it wasn't a corrupted exciter FW, but.... We'll see!

Thanks to all for their help so far!

M. K. Hess
N3EAQ
WWW.N3EAQ.NET
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