Avionics recommendations near Bay Area

[frcabot]

When it rains, it pours. I.e. when one thing breaks, so do a dozen other things at the same time. 

Own a 1982 Mooney M20J. On last flight the primary vacuum pump seems to have failed. (High/low vac light plus Artificial Horizon Indicator failure, aux vacuum worked so issue is likely primary vac pump). 

In addition the radios went tits up. I don't think the problem is the radios themselves as I have two and am having the same problem on both. I had the issue before, but it auto resolved and at my last annual the folks at LASAR said they had no idea what I was talking about and couldn't reproduce the problem. 

Basically intermittent static and intermittent auto-transmitting on both radios, the problem is much much worse at higher RPMs (I had to land NORDO at KOAK with light guns). Problem occurs on both radios as I said, I pulled out the fuse for COM1, checked COM2 and vice versa. At high RPMs the radios are unusable due to the static and blocking the radio frequency with transmissions. Also heard on the intercom system regardless of squelch. 

I suspect the issue is a short somewhere or some wiring that affects the engine and both radios, not sure what it would be as I don't know nearly enough about the radio system. 

In any event both issues need to be fixed. As i said I'm out of KOAK so needs to be within flying distance (plus, I need to get back to KOAK without a car or a plane assuming the problem can't be fixed in one day, unless one of you lovely folks volunteers to fly me back). 

Edited March 19, 2018 by frcabot
Typos

[carusoam]

Frc,

Sorry to hear about your challenges...

Sounds like you have your vac issue pretty well determined...

Can you explain more detail regarding your radios’ auto transmit issue?  

What specific radios are they?

What is it you are calling auto transmit?

Do you have any push to talk buttons, or anything else plugged into the intercom system?

Any old microphones plugged in somewhere?  iPods, intercoms, etc?

Best regards,

-a-

 

[larryb]

Sounds like alternator problem. A bad diode will cause a lot of power supply noise and it will vary with rpm. Try pulling the alt field CB with the engine running and see if it goes away.

[frcabot]

19 minutes ago, larryb said:

Sounds like alternator problem. A bad diode will cause a lot of power supply noise and it will vary with rpm. Try pulling the alt field CB with the engine running and see if it goes away.

Alt field? Edit: D'oh, Alternator Field

Also, how would an alternator problem on its own cause auto-transmissions? And without the auto-transmissions that just started during my last flight (and once before, which resolved), there is ordinarily no static on the radios.

Edited March 19, 2018 by frcabot
Clarification

[frcabot]

20 minutes ago, carusoam said:

Frc,

Sorry to hear about your challenges...

Sounds like you have your vac issue pretty well determined...

Can you explain more detail regarding your radios’ auto transmit issue?  

What specific radios are they?

What is it you are calling auto transmit?

Do you have any push to talk buttons, or anything else plugged into the intercom system?

Any old microphones plugged in somewhere?  iPods, intercoms, etc?

Best regards,

-a-

 

I have a GNS 650 and an older King something or other. As I said, I doubt very much the issue is the radios themselves. Auto-transmit is exactly what it sounds like, the radios are transmitting on and off on their own, filling the frequency and intercom with static. I have 2 PTT buttons but the PTT would not be causing the static so I doubt that's the issue either. Nothing else plugged into the intercom. Again, the telling facts here are the noise level of the static, and the frequency of the auto-transmissions, both of which are directly correlated with the engine RPM (static and frequency are worse at higher RPMs, better at lower RPMs, and essentially non-existent at idle).

Edited March 19, 2018 by frcabot
Clarification

[Marauder]

I have a GNS 650 and an older King something or other. As I said, I doubt very much the issue is the radios themselves. Auto-transmit is exactly what it sounds like, the radios are transmitting on and off on their own, filling the frequency and intercom with static. I have 2 PTT buttons but the PTT would not be causing the static so I doubt that's the issue either. Nothing else plugged into the intercom. Again, the telling facts here are the noise level of the static, and the frequency of the auto-transmissions, both of which are directly correlated with the engine RPM (static and frequency are worse at higher RPMs, better at lower RPMs, and essentially non-existent at idle).

I just fixed a similar issue after my interior was redone. My problem was the exact opposite of yours. Was picking up static on low RPMs that would go away at higher RPMs only to return once I began decreasing power.

I would look over your head set jacks carefully. In my case I had rubbing from the newly relocated rear jack that was periodically touching the insulation. While doing this troubleshooting, I noticed the insulators were missing on one set of jacks and a couple of other jacks were loose.

If the mic jack is able to reach ground, it would mimic a push to talk.


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[frcabot]

8 minutes ago, Marauder said:

 

I just fixed a similar issue after my interior was redone. My problem was the exact opposite of yours. Was picking up static on low RPMs that would go away at higher RPMs only to return once I began decreasing power.

I would look over your head set jacks carefully. In my case I had rubbing from the newly relocated rear jack that was periodically touching the insulation. While doing this troubleshooting, I noticed the insulators were missing on one set of jacks and a couple of other jacks were loose.

If the mic jack is able to reach ground, it would mimic a push to talk.


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This sounds like it would fit the issue. It would also explain why the problem occurred before, resolved, and then came back (the insulators could be loose, and being periodically displaced or something).

[Marauder]

This sounds like it would fit the issue. It would also explain why the problem occurred before, resolved, and then came back (the insulators could be loose, and being periodically displaced or something).

 

At least it is something you can check yourself and not pay $100 to someone to tell you something is loose.

 

 

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[frcabot]

6 minutes ago, Marauder said:

At least it is something you can check yourself and not pay $100 to someone to tell you something is loose.

 

Assuming I can visibly see the problem (the rear jacks are located in the armrests and so would the armrests would have to be taken apart, etc.). The vacuum issue requires someone to take a look at it, unfortunately.

Still don't have any recommendations for avionics shops. (Actually, does the vacuum pump require an avionics shop or could any A&P fix the issue (and the radio issue assuming it is not simply jack wiring?).

[Marauder]

An A&P can certainly look at both problems.


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[frcabot]

So likewise, any recs for A&P in the area? I don't want to go to LASAR or Top Gun, they will charge a couple thousand dollars just to look at the thing. I don't think either of the issues are very complicated and I don't think they need an MSC billing at $110/hr.

Edited March 19, 2018 by frcabot

[larryb]

I would think you would want an A&P for the vac pump and an avionics shop for the radio issue. Most (not all of course) mechanics are not electronics experts. Ideally this would be somebody local to you. Who has been maintaining your aircraft so far? Or are you new to the area? I don't know anybody in Oakland, although I do know a couple at my field KRHV.

 

I suggested the alternator issue because your symptom varies with rpm and also because it is very easy for you to test yourself. I also suggested it because power problems often cause very random and hard to track fails that don't necessarily make sense. I once had a marine radio that transmitted on the wrong frequency. The replacement radio did the same thing. Ultimately I found the radio power was wired with wire too small causing a voltage drop under transmit which caused this strange fail.

 

If it were me I would do a bit more debugging on the radio issue myself before I turned it over to a shop for repair. Lets talk about the self-TX symptom. Does this happen on both radios simultaneously, or only on the radio selected by the audio panel? If it is just the selected radio it would be likely to be Marauder's issue. Only the pilot positions have PTT, so the rear passenger jacks could not cause this. And the pilot jacks are easy to see, no disassembly required. If both radios self-TX at the same time that would suggest the audio panel, which is the only common device which could cause this. While observing the failure you could slide out the audio panel from the rack and observe if the problem stops. Most avionics use a 3/16 hex in a little hole in the front panel to release them from the rack.

 

Finally, in both my previous J and current Encore there is a 2nd set of headset jacks wired directly to the #1 radio. For me these are located next to the pilot right knee. These are for emergency purpose when the audio panel fails. Assuming your install is similar, you could slide out the audio panel and connect your headset to the backup jacks and observe any changes.

 

Larry

 

 

[OR75]

A&P in the east bay.  I do my own maintenance on my J. Happy to help you out of you are still looking . PM me. 

[frcabot]

It happens on the ISOCOM system and whichever radio is selected. So the intercom for example is unusable. A workaround I found for the radios is to pull out the com2 fuse, set com1 phone on (essentially monitor com1 whether or not it's selected) switch to com1 to transmit and switch back to com2 (off) to monitor. The opposite also works. I couldn't find any obvious wiring issues but one of the two PTT buttons may have gone bad. Pretty sure that's where the issue is. So I think an A&P could look at both. 

Still looking for an A&P with a reasonable rate in the bay area as I don't want to pay a $110-120 shop rate at LASAR or Top Gun. 

[bradp]

I had a similar issue with... well I don’t even know how to describe the wonky behavior but com1 went bad for transmit but not receive and com2 worked just fine.  It was the headset jack. The nut had worked itself loose so that the transmit shorted to something beside low (ground). It wreaked havoc with a GNS but KX-170 seemed not to mind too much.  I troubleshoot and figured out the cause by asking some folks on the CTAF to help me out while I sat and thought through the failure mode.  I was literally about to pull into the radio shop when I noticed the nut was a little loose, tightened it, problem fixed and taxied home.  As much troubleshooting as you can do yourself will help narrow down the problem.  

[amillet]

Paying LASAR or Top Gun $120/hr is cheaper if they can diagnose and solve the problem in less time, due to their experience.  I have used both and find them to both be very efficient and fair in their pricing.  As a lawyer with 37 years experience I can perform tasks in 15 min. that took me two hours 35 years ago.

[glenn reynolds]

I have had two electrical issues which several shops couldn't fix but got fixed at executive autopilot in less than half a day.  Frankly I wish I hadn't gone to the other shops at all.  The bad news is that it was a several week wait to get an appointment, but to their credit they had me on my way before noon.  Im sorry to say that too many a&p just are not quick with electrical issues.  Good luck 

[wishboneash]

+1 to Exec Autopilots at KSAC. They fixed my ancient autopilot (Century IIB) while others tried many times. I use them for all my avionics installs. Things must be lot busier these days there with lot of the ADS-B out installs going on.