Spectra dies on transmit. Any Ideas how to fix?

[Mastertech]

Ok, my 110 watt analog spectra has recently started turning off when I TX on some freqs. but not others. When I key the mic it shuts off and restarts right away with no fail codes. IT has plenty of power (correct voltage and enough current) and the swr is very low. Who can help with this> THanks MARK

[ArmsonOeg]

I had exactly the same problem 1 month ago,except i thought or (assumed) i had power. It was my battery backup maintaind by a float charge. My display faded in and out (1/2-2 sec) before shutdown and what was odd, some freq's did not shut it down until much later.

Take care of it and DO NO TX as mine now has the audio pop or thumping that it did not have prior.


GMan

[phrawg]

Is this on the bench or installed in a car ? I have many times
set my current limit on the bench to a safe level for testing
some low current device then forgot to reset it, and the next
hi power radio had me tearing my hair out till I remembered
to open the current limit back up. Also in a mobile look for
that hidden butt splice in the heavy red cable under the carpet
that has been forgotten about or that ring terminal that needs
to be soldered instead of just crimped and is making a high
resistance contact when you pull full current. The thing is that
if it has worked for at least a reasonable time as installed,
then gong bad, something has changed ! locate it even if
you have to go over the system detail by detail. Phrawg

[Josh]

furthering what Phrawg said, test the radio on a known good power source first. That will determine if it's really the radio or not.

It absolutely seems to be too low apherage.

-Josh

[jmr061]

I agree, if you are bench testing it you should have a power supply capable of at least 30 amps if not 40. These radios will exhibit this behavior with bad power supply and improper antenna hook up as well.

Jason

[wa2zdy]

If this is on the bench, be sure RF isn't shutting the regulator down in the power supply. Common problem often overlooked.

[Pj]

How big of a p/s are you using?

[Mastertech]

the power supply is a car. The instal is def not the problem the problem is confirmed to be within the radio. The issue goes away when a dummy load replaces the antenna. However, the antenna swr is very low

[Josh]

A radio resetting will occur with low ampherage and good antenna. I've seen this behavior with portable radios using cigarette lighter battery eliminators, which don't supply the radio with enough power to properly transmit through a good antenna, however it can with a dummy load or even with no antenna at all, but will simply reset under the conditions of the stock antenna.

Again, take the radio to a good high-amperage power supply and go from there.

-Josh

[Mastertech]

Ok, put the radio on the bench with a 60 amp astron supply and the radio still has the problem with an antenna, but not with a dummy load

[kcbooboo]

I'd suggest going through the power amplifier alignment and setting the output power and current limiting to their rated values with a known good wattmeter and dummy load, using quality cables.

Bob M.

[Mastertech]

the radio is rated for 110 watts power output and I have it set to 100. If I read the service manual correctly it asks for the current limiter adjustment to be set just above where you start to loose power output and this is how I set it with an brand new IFR2975. Nevertheless, Im pretty sure the curent limiter only controls power to the PA< not the rest of the radio. If I am mistaken here PLEASE, someon correct me. Thank YOU!

[Larry Page]

I had a multi-radio setup in a previous vehicle. My 50 watt VHF ICOM would, under certain circumstances that I never did figure out, create the same problem in a trunk mount 45 watt VHF Spectra. I never did determine for sure whether RF was getting into the remote panel, the remote cable, or into the radio itself. But the Spectra, which was not transmitting at all, would cycle off and back on. (On one occasion, it powered off and stayed that way.)

The experience prompted me to review my entire installation, and I changed a number of things, including adjusting antenna location, eliminating a mag mount antenna entirely, and improving ground connections by shortening wires and using improved connectors. The problem went away and never returned.

It is a well-observed truth that 2 meter transmissions can cause havoc in some newer cars because so many of the wiring components are so near 2 meters (or 1 meter) in length. In the mid-90s especially, it was very common to accidentally trigger auto alarm systems by transmitting nearby. For that reason, I have always since taken special care with routing and placement of any cables between a remote head and a transceiver. It's too hard to predict what might happen to a voltage or current induced into a near-resonant control line. The problem can exist even if these lines are shielded, because the material used usually does not provide 100% shielding.

Let us know what you find out. These problems can be very mysterious, and anything that anyone learns can be important for resolving possible future problems.

[Bob W]

Ok, put the radio on the bench with a 60 amp astron supply and the radio still has the problem with an antenna, but not with a dummy load

When you are bench testing it, where is the antenna? What I mean is: can you see it, or is it on the roof of your building. 100 watts is alot of power - induced voltage into electronics wise. If you are testing into a nearby antenna, you could be nuking the radio, causing it to shut down. Same deal with the antenna on the car. What kind of antenna, and where is it? Mag mount, and trunk, or nice hole punched in roof?

The fact that it works into a dummy load, but not into an antenna that has no reflected power to speak of means that it's the radiation from the antenna causing the problem. Well matched antenna, or dummy load looks the same to the radio. Try keying it FOR A SECOND with nothing attached to the antenna port of the radio on a "go to sleep" frequency. The radio will probably draw some, but not full current, but probably won't die. That will rule out mismatch causing the problem. At that point you are back to a power supply issue, or a radiation issue. Probably not a power supply issue because you've tried it on multiple supplies. What is the current difference between a good and crash frequency into a dummy load? If a crash frequency is not much different, that also would rule out a power source issue.

How far apart are the working vs. crash frequencies?

[Mastertech]

well, the radio is installed in a 2001 impalla and has never caused any problem with the vehicle itself. It is bolted with 3 other radios on a metal shelf in the trunk. The power consists of a six gauge bat pos and bat ground, both of which are fused at the battery. This then goes to the individual radio fuses. There are no butt connections within this instilation. All the ring terminals are crpimed with my snap-on crimper, soldered, and heatshrinked. The battery is new and the alternator works correctly. The radio green lead goes to switched ign and the orange lead is place at the same point as the radio B + I did instilation for a federal contractor for several years (Untill I went back for a masters) so I have a good sense of how not to do these sorts of things. Ill keep playing and let you know what I find. I believe that Chris is on to something with the voltage regulator, and I am wating to hear from him.

[Mastertech]

Ahhh, ok. The antenna is mounted in the trunk-drilled in nmo mount-. Ill try placing the antenna on the roof with a mag mount and see if that does it. Im going to be really unhappy if I need to move the antenna to the roof! These would be a 3/4 in hole in the trunk of my really nice ride. Oh, the antenna is a QS150

[Mastertech]

movedthe antenna, still the same problem

[phrawg]

AHHHHHH !!!!!! A Clue !!!! Probably not the cause but
you commented that the orange lead is to switched ign.
Maratracs are known to be VERY persnickity about having
the grn/org leads at exactly the same voltage as the main
b+ supply to the pa deck. Dont know if maybe this Spectra may be exhibiting a similar fluke. Generally recommended that they
run to the battery directly and you use the manual power
switch on the head. I know, It defeats the feature but in a
car where there is a voltage drop through the switched ign
path it can make the radio go squirley. The other thing
you might look at is the routing of the coax cable to the
antenna on the trunk lid and also install some ground straps
to bypass the trunk lid hinges. I have had a car that if the trunk
was unlatched but closed, my 50 watt vhf radio would go nuts
when I transmitted. as soon as I latched it down, Perfect!
I installed grounds by using the shield of some rg-8 coax
to the trunk lid with good metal contact. (scraped paint,
star washers etc) the other end went to the body under the back
window deck. Problem solved even with the lid up an inch or two.
These new cars DO NOT provide good ground integrity especially
where rf is concerned and it gets worse with age and corrosion
and your trunk lid is probably becoming isolated
more with the age of the hinges. Try bypassing them
with the wire braid straps around them and let us know. Phrawg

[phrawg]

Oh, BTW a mag mount on the roof would not be as good as
a real drilled mount would obviously be, so I would not still
rule our stray rf. Have you also looked at the output on
a spectrum analyzer to be sure that some spur may not have
cropped up that is on a freq that can get past your trunk lid
and into your radio gear. Maybe the primary freq is not the
culprit here. Remember that a watt meter is just giving you
a cumulative total of all of the rf, not telling you what freq it
is on. I used to get a laugh ot the CB banders with big amps
that put out 500 wats of so. 400 on the harmonic and 100
on the fundamental but they insisted they were doing 500
because their watt meter said so !
Just another thought. Phrawg

[wa2zdy]

The power consists of a six gauge bat pos and bat ground, both of which are fused at the battery. This then goes to the individual radio fuses.

My voltage regulator post refers to a bench power supply. You should not have this issue in the car.

Get rid of the negative lead to the battery. I'll bet you have individual fuses for each negative radio lead too. Get rid of all of that. Take the radio negatives, tie them to a bus bar and ground that to the nearest big bolt in the trunk. All that negative wiring is just another source of IR loss, a path for RFI and a potential ground loop.

Get someone to help you and even though you say it's fine with the dummy load, you put a VOM/DMM on the power lead to the affected radio, AT the radio, and have your helper key the rig. Make sure the engine is running at least fast idle speed. See how much the voltage drops when the radio is transmitting.

Radiated RF could be getting into something else, not sure. But the above advise is all solid too. I especially like phrawg's idea about the ignition sense lead being too far off from the main supply voltage. Fix that first, whether or not it's the problem. If it isn't now, someday it will be.

[Mastertech]

thanks for all the usefull info. Ill try these steps and let you know how it all worked out.

[wx4cbh]

Maybe I missed something, but it's the GREEN lead that needs to be connected at the same battery +12V source as the large red power wire, not the orange. MotherMoto is absolutely adamant about that. Without getting into circuit analysis here, suffice it to say that if there is a sufficient voltage difference between the green wire voltage source and and the red wire voltage source, the radio will begin to shutdown at some point. Also, circuit noise present on the vehicle's accessory harness (fuse panel) is always a potential source of gremlins. The orange wire can handle the majority of the offending little buggers since its function is a bit more simple.

And I concur that the grounds need to be connected to a common ground bus near the radio, not through a fuse at the battery. You could remove the fuses from the picture and connect the trunk end of the NEG wire to a heavy ground point in the trunk, and connect the radio ground there if you feel the trunk area of the body doesn't have a good ground connection. This will serve to make a secure ground connection in that area for the radios and the body, but really shouldn't be necessary if the factory body joints and connections are in good shape. If they weren't, there would be other indications of problems.

[Mastertech]

Good point, Is it the green lead on these radios that needs to be on the hot battery line, and the orange swithced?

[phrawg]

Yep, that was my typing faster than thinking. The green wire
is most critical and brings up most of the radio when powered.
The orange wire when 12v is applied allows the radio to xmit.
Thats what I get for typing during my FIRST cup of coffee !
Keep inspecting and checking things. This will be one of those
deals where when you find the problem you will probably say
that if it was a snake in the trunk it would have bit be 10 times
already. Good luck. You will get it yet. Phrawg

[wa2zdy]

Properly fuse both orange and green lines, connect them to the main red power line and just remember to turn the radio off when you park the car at night. Eliminate the whole issue.

[Mastertech]

Ok, ill make these changes this sat. and tell you all how it works out. Thanks.

[phrawg]

HEY ! Whatsup, any resolution on the dying on transmit ?

[Mastertech]

Ok..... sad to say that I moved the wires as suggested and still no fix. This is a tough one.....

[jackhackett]

It's a Spectra... so there's always the suspect capacitors. I've never seen them cause a problem like this, but who knows? You might at least try changing the caps in the PA and the control head if it has them.

I wasn't expecting to hear that rewiring the vehicle helped, since you had said the problem also occured on the bench. I would go back to the bench and do more testing. Verify that the radio has all of the proper shields in place, reseat connectors, measure voltages when keying, try turning the power down.

[phrawg]

OK, open the radio up on the bench and set it up to operate.
now take a voltmeter and start at the power supply and measure
voltage unkeyed then keyed. Then go to the main power connector
at the radio, same measurements. Then go to the pa board and
look at the b+, same measurements. Then to a power land on the
pa board, etc etc etc till you have a heavy drop on tx. if there
is one there is a high resistance connection between there and the
last measurement. If this pans out ok then start looking at rf
swamping some circuit. Check shields, check board mounting screws,
(I have seen just loosening then re-tightening several times all of the
screws fix an rf prob due to restoring ground. Especially on pa board.)
I think this is the level of troubleshooting you are into now. You will
have to become very methodical now in doing so. Also look for
possible crystalized solder on the pa transistors causing eratic signal
ans spurs. (look on a spec analyzer) pls keep us informed, Phrawg

[Mastertech]

Ok, im at grad school for a while but I will try these suggestions. I guess this will give me a chance to try out my new Pace MBT350 soldering station Thanks guys. Ill try to post again in a week.

[firetech792]

Just had this problem earlier in the week, in an ambulance. Turned out to be a loose chassis ground on the power cable. (And slightly corroded ring terminal).

[007]

The power consists of a six gauge bat pos and bat ground, both of which are fused at the battery. This then goes to the individual radio fuses.

As Chris ZDY mentioned above, get rid of that ground setup. The 6 gauge should be routed to a reliable ground stud in the trunk, not all the to the battery. There shouldn't be any fuses on the ground wires either.

There is a reason that /\/\ made the ground cable 3 feet long, and it wasn't because they are cheap and wanted the end user to install the other 15 feet to the battery.

The ground needs to be short, unfused and directly to the chassis.

[Mastertech]

To all who are still worried about this issue... Thank you cuz im still working on the problem. HOWEVER< the radio wiring IS NOT THE ISSUE. This problem occurs on the bench under very tightly controled circumstances in a very large MOTO repair shop. That being said, I think we can rule out wiring beyond a shadow of a doubt. Im convinced that the problem is inside the radio and once Columbia U gives me some time off (hopefuly sooner rather than later) im going to get into this further. Cuz, after all, there is nothing like pimpin a 110 watt 2 meter radio on youre favorite repeater. Thanks all, keep the comments comming