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Microair Radio Problem !!! Help

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Microair Radio Problem !!! Help

Postby duncanlogan » Mon Jan 11, 2016 5:01 pm

Hello Gents,

Im looking to get some help and suggestions for the problem below,

I have had my Microair M760 Rev P transceiver now for almost 4 year. Today was my first flight of 2016 and just over 2 months since I was last at the airfield due to bad weather and the forth road bridge being closed.

After starting the engine and switching the radio on, everything was normal , radio check great, until I started my take off roll, the screen began to flicker and then on climbout it packed in all together. the screen went blank but the unit still had power to it as it was still illuminated. I tried switching it on and off in mid air with no success.

After landing, I checked the voltage the unit was receiving again the unit screen is lit up but there is no text on the screen. With the engine switched off and only the battery supplying the unit it still didn't work. As for the rest of the instruments and Aera 500 they all appeared to be working.

I did notice when the engine is idle running about 950 rpm the screen lit up is duller than usual. When I increased the revs it got brighter, I had a volt meter over the terminals from the fuse and the volts would range from about 9.9v (Idle) to 16v (2000rpm). Is this normal for a jab 2200 engine or is there a problem with my voltage regulator ???? as suggested by a club member. If so could an over voltage during take off damaged the radio hence why it wont work now.

Has anyone had any similar problems with a microair radio, I know there's been loads of issues with this type, but Ive only heard of people having problems transmitting or receiving etc.

Any help or advice would be much appreciated

Is anyone aware of a contact to have my radio repaired lastly?

Regards

Duncan
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Re: Microair Radio Problem !!! Help

Postby Garyo » Mon Jan 11, 2016 7:58 pm

Hi Duncan, I seem to remember the microair is good for 15v, but I may be wrong. 16v is too high, max I think is 14.7v output
Chances are its going higher at full beans.

Sounds like the rectifier/regulator is going duff. Prob your other instrument will take a higher voltage, I would not fly it untill you sort it to avoid wrecking anything else. Try all the connections are not cruddy especially the yellow sence wire, if this is dodgy it will think the battery is flat and pump up the volts to it.

I think Deano posted something about a repair shop for them. You may be lucky and find an internal regulator or zener diode internally that has blown, follow the power supply lines through the circuit of the radio.

When sorted it is worth fitting a dc to dc convertor that has an isolated ground, this will prevent the unit ketting killed should it ever happen again.
In the archive files, Vics old site on here I posted a pade on the dc to dc convertor, the Recom part number will be there

Let us know how you get on
Gary
Former Owner of
G-OMER
Jabiru 450 UL
Engine serial 1041
1 CHT sensor on No 4 under plug
No Exhaust temp sensors
No glass panel
No xponder
Microair radio
No bells and whistles
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Re: Microair Radio Problem !!! Help

Postby Garyo » Mon Jan 11, 2016 8:01 pm

Forgot to say mine when the battery is low puts out 14.7v and normal output is 14.1v
Gary
Former Owner of
G-OMER
Jabiru 450 UL
Engine serial 1041
1 CHT sensor on No 4 under plug
No Exhaust temp sensors
No glass panel
No xponder
Microair radio
No bells and whistles
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Re: Microair Radio Problem !!! Help

Postby duncanlogan » Mon Jan 11, 2016 9:33 pm

Thanks Gary,

I've taken the cover off but there's no obvious damage inside.

I think im going to need to send off the radio to get repaired. has anyone on here sent away a radio to be repaired recently?

Regards

Duncan
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Re: Microair Radio Problem !!! Help

Postby diablo » Tue Jan 12, 2016 11:03 am

I sent my radio to the US for repairs. It turned out to be moisture (the sealing compound they use on circuit boards had broken down).

The problem you are reporting could well be due to low voltage as they seem to do all sort of weird things if the voltage is below 11.8V. There is also a max voltage and they will break down if operated above I think 15.2V.

You are right, the Jab stator is pretty unreliable and a Zener or Transorb diode as well as a capacitor (large 20,000 uF) should be used across the stator / regulator output to smoothen out any crap and shunt if voltage goes above a certain value. I would remove the radio and test it on a 12v charged battery to determine if it is working nominally and take it from there.

Here is microair's addy in the US:

Rick Lord
Microair Customer Support
MicroairUSA Service Centre
1903 West 8th Street PMB 224
Erie, Pa 16505-4998 USA

On another note, I dont think microair US or AU do repairs on older models any longer (erarlier than Rev Q). The only model they service is the Q rev model. However, there is a service agent in the US and he may repair it. It is expensive at $200.00 + shipping (to and back) and customs is another pain in the backside !
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Re: Microair Radio Problem !!! Help

Postby Steevo » Tue Jan 12, 2016 11:07 am

What you are getting in your voltage readings are certainly not normal for the Jab engine. A lot of instruments now days are designed for both 12v and 24v systems with many being able to function as low as 8v. This is probably why your other instruments are still functioing ok.The Microair is not that tolerant of voltage change and has a very limited range.

I suspect that your regulator has given up the ghost and has probably damaged the Microair. Not all is lost, the regulator is very easy to change and the Microair can be repaired. Probably not much damage done. I would leave the Microair disconnected for now as you don't want to cause any further damage to it. I certainly wouldn't fly it until the fault has been rectified.
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Re: Microair Radio Problem !!! Help

Postby duncanlogan » Wed Jan 13, 2016 12:01 pm

Morning Guys,

Thanks for all the advise.

I have spoken to Rick at MicroAir USA about the radio and he was telling me that there are small over voltage fuses on the PCB which protect the Radio but don't protect the backlight, hence why its still lit when plugged in.

I've removed the radio and sent it to Rick for repair. I've been told there's about a 10 day turnaround. Hopefully its still salvageable as its a REV P version.

The voltage range was quite large somewhere between 10vdc and 16vdc. It defo sounds like the regulator has packed in. The fact that it packed in when full throttle was applied on take off.

I've ordered a new regulator KU - RP201-53710 from a british company called motoelectrical, it should arrive in a couple of days. Once fitted I can measure the voltage output and confirm the range compared to the old one. Im hoping i'll have the new regulator fitted by Friday afternoon, and i'll post my findings

Cheers
Duncan
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Re: Microair Radio Problem !!! Help

Postby diablo » Thu Jan 14, 2016 9:45 pm

I recommend you get yourself a transob diode (see below):

http://www.partsforaircraft.co.uk/downloads/tz.pdf

and a couple of 10,000uF Electrolytic Capacitors (connect them in parallel) accross your power circuit. It will protect your electronics from spikes and smoothen out the output of your regulator.

Paul at PartForAircraft atocks the parts and cost is under £20.00 - Money well spent !!

Should you want to work it all out, here is the formula ... I was making good progress with the formula till I got to the part that says "where" and lost myself.

20000uf.png
20000uf.png (20.26 KiB) Viewed 3570 times
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Re: Microair Radio Problem !!! Help

Postby Garyo » Fri Jan 15, 2016 9:34 am

is the transorb a zener diode that saturates when the voltage hits the value of the diode? do you have the diodes part number?
Former Owner of
G-OMER
Jabiru 450 UL
Engine serial 1041
1 CHT sensor on No 4 under plug
No Exhaust temp sensors
No glass panel
No xponder
Microair radio
No bells and whistles
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Garyo
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Re: Microair Radio Problem !!! Help

Postby Steevo » Fri Jan 15, 2016 10:17 am

Transorb is available from Parts4Aircraft. But you have to get the right one and considering the Microair has such a limited and low voltage range, you cannot always rely on the Transorb. The transorb will cause a current to short circuit if the voltage goes above a certain level for a certain time, this will cause the circuit breaker to trip. But the voltage has to have a range and a time and even one designed within the Microair voltage range could still cause damage. Most devices now (new ones) are designed for both 12v and 24v systems so will go upto about 30v before damage. That's easy on a 12v system because you just get a 20volt Transorb which will trip the circuit anywhere between 20v and 25v. The problem with the Microair is that if you get a 12v transorb it could keep tripping at normal voltage and you cannot go for a higher rated one because the Microair fries at 15v and a 12v transorb could go above 15volts for a limited time.

The best thing for the Microair, would be a step-up/down converter that holds the voltage at 12v as long as the input voltage is between about 8v and 40v. You could put a transorb on the other side of that to protect the converter with say a 20v transorb.

The transorb from Paul at Parts4Aircraft clamps at 33v. This is selected because the MGL stuff can handle 40v but would fry the Microair.
Jabiru J160 2009
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