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Wiring PM1000II to GNC250 XL

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ultimate10201

Member
I have wired a PS Engr. PM1000II Intercom into a GNC 250XL GPS/Comm for my RV7. The Intercom works as advertised when using the pilot and copilot jacks, but the comm is so dead, I must have wired it wrong.

Assuming someone has the SubD wire diagram, here how it was wired, showing the PM1000II pins first:

PM1000II GNC 250XL

Pin 17: A/C Radio Phone Audio Hi to Pin 5: COMM AUDIO HI

Pin 4: A/C Radio Phone Audio Lo to Pin 6: COMM AUDIO LO

Pin 12: A/C Radio PTT to Pin 4: MIC KEY

Pin 25: A/C Radio Mic Audio Hi to Pin 2: MIC AUDIO HI

Pin 13: A/C Radio Mic Audio Lo to Pin 3: MIC AUDIO LO

PS Engineering says to wire aux jacks to the system and wire the radio to the aux jacks as well. So I dutifully ran wires from the intercom to the jacks in the panel, then soldered in wires from the jacks back to the GNC 250XL. In retrospect, I think I could have saved all the wire runs just by joining wires at the intercom Sub-D connector for both jacks and radio.

This makes which end to connect the shield connection a little fuzzy on top of it all.

To test, PS Engr. says to power up but leave the PM1000II off. Use the aux jacks to test the radio. I did; it?s dead.

Maybe my GNC 250XL comm needs repair. I bought it in 2006 and installed it just within the last month.

Can anyone point me in the right direction?

Thanks in advance.
 
Nowhere in your post or profile is there a clue as to where you are. If we knew what part of the country, maybe we could help. I have had the PM1000II and a GNC250XL for quite a number of years. It's a great match.
I'll dig out my wiring diagram tomorrow and take a look.
 
You will need to provide more information

Good Morning Sir,

If you want help troubleshooting, you will need to provide more information. Saying the COM is 'dead' is not very descriptive.

With the PM1000II turned off (or better yet unplugged):

Make sure a COM antenna is connected to the TX connector (not the GPS connector). Plug a known good headset into the aux jacks. If the headset is stereo, switch it to mono, or use a mono-stereo adapter plug.

Turn the GNC-250XL on and set volume to mid-range

Can you hear anything (such as ATIS) on the GNC250XL?

Does the GNC-250XL RX indicator show when ATIS is tuned?

Cycle the GNC-250XL SQ button - does the RX indicator go ON and OFF?

When you press PTT sw, does the GNC-250XL TX indicator show?

When you attempt to transmit, can you hear yourself in the headphones?

When you attempt to transmit, can a buddy with a handheld tuned to the same frequency hear anything (clicks or your voice)?

If you can do these tests, we can get some idea of at what level the GNC-250XL is functioning, if at all.

I used to have a PM1000 hooked to a GNC-300XL - that combination worked well.

Regards,
Blake Harral
RV-4 N72RV
 
Thanks to both of your for the response. I was surprised that I was still a member of the forum from a post I sent years ago, so once logged in, I launched a quick note when I didn?t really have time to do it properly. I should have waited. My apologies for being brief rather than clear, and for having no profile saved (I took care of that issue by updating my profile so I?d show myself as legitimate).

When wiring the unit, I installed dual power and ground connections as advised.

The GPS side of the unit is working just fine (I have output to my Autopilot, but I haven?t tested that since the wings are not installed and hence the roll servo is not connected). I powered it up with only battery power and after about 10 minutes, in my garage, door closed (cold outside), it had acquired satellites and announced ready to navigate. I punched in T31 (AeroCountry Airport near McKinney, TX) and it showed I was 106? at 3.21 statute which is pretty much dead on since I live east and slightly south of the airport about 3.5 miles driving distance. GPS 3D altitude showed around 740? or so. T31 is officially 792?. So at least this makes me think the unit has power and that it's available to the COM side.

Before unplugging the intercom, I had already tested the PM1000II with my headset in the pilot and copilot jacks as noted in my last post. I can hear my voice clearly, I can set squelch so that voice activation is finely controlled, pressing the mic buttons on the grips shows the intercom in transmit mode (momentary red light). This indicated to me that I had wired the jacks properly and consistently.

When testing the COM, I eventually tried it with the PM1000II Sub-D unplugged as suggested. COM Antenna was connected properly. My headset is an old DaveClark H10-40 refit with the Headsets, Inc. ANR Module. It?s stereo, I think; and I did not try it with a mono-stereo adapter. Could this be the problem?

I inserted plugs into the Aux jacks, turned on the unit, and had these results:

No sound whatsoever ? none through the COM, can?t hear my own voice. I tuned several frequencies (ATIS at McKinney Muni is about 9 miles away) with no results and there?s no RX indicator displayed when tuning any of the stations nor does the SQ control display the RX indicator when cycled. The TX indicator does not display when keying the mic, and I can?t hear myself in the headset under any conditions. We tried using a handheld with no results, as well.

It?s as if there is no power to the COM side of the unit. Wondering if the voltage was low, I connected a battery charger to the battery and noted > 14 volts in the system (per Dynon EFIS), so I think the voltage was adequate. Test results were the same.

I bought this unit in 2006. Last year, I plugged in a DC wall adapter to use the GPS unit in Simulator mode. The adapter was one I had lying around rather than the Garmin product, but the amperage and voltage on the adapter were less than the 1.4 amps and 13 volts specified in Garmin?s manual. The GPS worked fine using that adapter. Any chance my being cheap damaged the COM side?

Again, thanks for taking a look.
 
Do a careful check on these three wires to see if they really go to where you think they do...

Pin 12: A/C Radio PTT to Pin 4: MIC KEY

Pin 25: A/C Radio Mic Audio Hi to Pin 2: MIC AUDIO HI

Pin 13: A/C Radio Mic Audio Lo to Pin 3: MIC AUDIO LO
 
Sounds like the GNC-250XL has problems

From your description, I don't think you have done anything wrong.

Maybe the GNC-250XL doesn't have an RX indicator - I don't recall.

However, the failure to get the TX indicator is disturbing, that should require nothing more than a properly wired mic keying line.

If the GNC-250XL does not show TX when pin 4 is grounded to pin 3, then the unit probably needs factory service. This is a 14V radio, perhaps in its past someone applied 28V and the power input section has been damaged.

Garmin has a flat rate repair fee of $550 for this unit.

Good luck.
 
Thanks to all.

I re-checked all connections as advised by Mr. Alexander:
Pin 12: A/C Radio PTT to Pin 4: MIC KEY
Pin 25: A/C Radio Mic Audio Hi to Pin 2: MIC AUDIO HI
Pin 13: A/C Radio Mic Audio Lo to Pin 3: MIC AUDIO LO

These checked out without exception.

As 'bharral' advised, I tested continuity from the PTT contact on the Aux jack itself to pin 3 (COM removed from the rack, intercom was off); it only shows continuity when I depress the pilot's PTT button on the left stick grip as expected. But with the radio installed in the rack, it remains that I don't get the 'TX' indicator, no sound in headset, etc.

I talked to Garmin today who also advised I should test the the PTT the same way.

I'm sending it to Garmin. Sigh. Ever notice how when you get close to the end of a project, you just write the checks to get it done?

Thanks again for the help.
 
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