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Old 21-10-2014, 12:03   #16
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Re: Question for the Electronically Savvy

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Originally Posted by Cadence View Post
You nailed it. Apparently the OP does not have a schematic or an extensive background in electronics. Sam Photofax probably doesn't carry a schematic, if they are still in business? If a shop can be found to look at the unit? If honest would say buy a new unit, it would be cheaper than our time. Lets face it electronics a disposables.
I repaired an old Garmin plotter for a slip neighbor a while back. He had broken one of the pins in the power connector and the unit wouldn't power up. I switched the power connection to an unused (and unbroken) pin on both the unit and the cable. He took my wife and me out to a nice restaurant.

Anything more complicated is beyond most folks without a schematic and parts availability. Even when you send one in for repair they don't repair it they send you a reconditioned and tested one.

Keep in mind, this is not your stereo, this is a critical navigation and safety device. Failure could leave you lost or on the rocks and sinking. Repairs need to be done right or not at all.
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Old 21-10-2014, 12:36   #17
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Re: Question for the Electronically Savvy

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I repaired an old Garmin plotter for a slip neighbor a while back. He had broken one of the pins in the power connector and the unit wouldn't power up. I switched the power connection to an unused (and unbroken) pin on both the unit and the cable. He took my wife and me out to a nice restaurant.

Anything more complicated is beyond most folks without a schematic and parts availability. Even when you send one in for repair they don't repair it they send you a reconditioned and tested one.

Keep in mind, this is not your stereo, this is a critical navigation and safety device. Failure could leave you lost or on the rocks and sinking. Repairs need to be done right or not at all.
? I was agreeing with you.
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Old 21-10-2014, 13:17   #18
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Re: Question for the electronically savvy

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My bet is that there is a relay somewhere inside that is not latching up. When you push the button do you hear a click? Also check that any connections are clean and well seated.
I don't know how old this unit is but there are very few mechanical relays in electronics these days. And electronic relays don't go click.
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Old 21-10-2014, 13:30   #19
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Re: Question for the electronically savvy

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I don't know how old this unit is but there are very few mechanical relays in electronics these days. And electronic relays don't go click.
I don't know about anyone else, but I haven't seen a discrete 3 Pin transistor in a piece of electronic equipment in a long time either. Almost everything these days is inside an IC - integrated circuit.
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Old 21-10-2014, 13:46   #20
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Re: Question for the Electronically Savvy

Really... Look back at the main board pic.. I count 3 that I can plainly see.

In my experience, the "Black Box" thing is a complete myth. Most everything I take apart and fix has off the shelf parts. Its pretty rare that I will find an IC with a custom brand on it. We do find COB (chip on board) stuff sometimes, but they are rarely the cause of the failure..

The real problem comes with the failure of a microcontroller (very rare unless a voltage spike). The software is proprietary and you can't simply swap the component unless it comes from a spare that is the exact same model of the product your are working on (sometimes you need the exact board revision). If you are super lucky (like lottery lucky) the company forgot to protect the software and you can back it up using an ICSP tool. Then you replace with the exact same part, and reflash.

If anyone wants to learn a ton about electronics and product design, look up eevblog on youtube. Dave is super knowledgeable and has done 100s of teardowns of common products over the years. He shows what chips are in the device and links the datasheets. He recently did a teardown of a GoPro 4 and didn't find a single custom IC.
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Old 21-10-2014, 14:20   #21
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Re: Question for the Electronically Savvy

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Really... Look back at the main board pic.. I count 3 that I can plainly see.

In my experience, the "Black Box" thing is a complete myth. Most everything I take apart and fix has off the shelf parts. Its pretty rare that I will find an IC with a custom brand on it. We do find COB (chip on board) stuff sometimes, but they are rarely the cause of the failure..
Sorry. I guess I didn't look closely at he PCB. The OP did say that this was an old piece of kit though. I still say that you will find very few discrete transistors on today's modern stuff. And yes, you are right - I have never seen a custom brand IC, although I'm sure that they exist. Some manufactures do have standard IC's made for them without any nomenclature though.
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Old 21-10-2014, 14:22   #22
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Re: Question for the electronically savvy

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I don't know how old this unit is but there are very few mechanical relays in electronics these days. And electronic relays don't go click.
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Old 21-10-2014, 14:23   #23
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Re: Question for the Electronically Savvy

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Sorry. I guess I didn't look closely at he PCB. The OP did say that this was an old piece of kit though. I still say that you will find very few discrete transistors on today's modern stuff. And yes, you are right - I have never seen a custom brand IC, although I'm sure that they exist. Some manufactures do have standard IC's made for them without any nomenclature though.
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Old 21-10-2014, 14:39   #24
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Re: Question for the Electronically Savvy

I had the same issue with a newer Garmin unit. The problem was the video input had a ground fault. I unplugged my cctv camera input and it powered right up. Try unplugging everything from the back of the unit except the power cord. If the nmea 183 connections go through the power cord, disconnect all of them first. You may find the issue is with a peripheral device. Apparently there is a safety mechanism that will not allow the unit to fully power up if it detects a short...
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Old 21-10-2014, 14:46   #25
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Re: Question for the Electronically Savvy

Just a little more than svfinlandia's input. Relays? SCRs took their place long ago and they are probably long gone. It looked like some where troubleshooting triodes also long gone. Everything has been on a chip for years. Troubleshooting lows and highs gone with the wind. If the chip goes tits up even if you can find a replacement soldering it in would be a bitch.
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Old 21-10-2014, 15:05   #26
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Re: Question for the Electronically Savvy

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I had the same issue with a newer Garmin unit. The problem was the video input had a ground fault. I unplugged my cctv camera input and it powered right up. Try unplugging everything from the back of the unit except the power cord. If the nmea 183 connections go through the power cord, disconnect all of them first. You may find the issue is with a peripheral device. Apparently there is a safety mechanism that will not allow the unit to fully power up if it detects a short...
This is a good idea to try before tossing it, won't cost anything.
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Old 21-10-2014, 15:08   #27
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Re: Question for the Electronically Savvy

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This is a good idea to try before tossing it, won't cost anything.
Sounds like an excellent idea.
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Old 21-10-2014, 15:30   #28
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Re: Question for the electronically savvy

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I don't know about anyone else, but I haven't seen a discrete 3 Pin transistor in a piece of electronic equipment in a long time either. Almost everything these days is inside an IC - integrated circuit.
The discrete transistor is alive and well. The modern Icom M506 VHF/AIS has over 60 of them as does the M802 SSB. Still commonly used elsewhere in marine electronics power supply circuits, power control circuits and power amplifiers. Very commonly used to switch power on/off in marine electronic equipment. In the case of momentary membrane power buttons, low level logic is being used but the actual power is being switched via discrete transistors. Very difficult to figure out without the schematic and board layout diagrams found in service manuals. Equally difficult to get service information for most modern marine electronic equipment. Very few of us doing component level repairs these days.

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Old 21-10-2014, 15:42   #29
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Re: Question for the electronically savvy

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The discrete transistor is alive and well. The modern Icom M506 VHF/AIS has over 60 of them as does the M802 SSB. Still commonly used elsewhere in marine electronics power supply circuits, power control circuits and power amplifiers. Very commonly used to switch power on/off in marine electronic equipment. In the case of momentary membrane power buttons, low level logic is being used but the actual power is being switched via discrete transistors. Very difficult to figure out without the schematic and board layout diagrams found in service manuals. Equally difficult to get service information for most modern marine electronic equipment. Very few of us doing component level repairs these days.

Eric
Probably with a transmitter? The OP was strictly reception. actually it wasn't even that it was a display problem.
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Old 21-10-2014, 16:14   #30
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Re: Question for the Electronically Savvy

I quoted svfinlandia, who claimed "I haven't seen a discrete 3 Pin transistor in a piece of electronic equipment in a long time", but the point is, discrete transistors are still widely used in electronic equipment including the OP's GPS receiver.

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