Nav radio, should be easy fix?

[darot]

I have a 2005 jeep REC radio, cd, nav, sat. Its 30 degrees outside and when I turn the car/radio on, it works fine. As soon as it starts to warm up the ldc screen goes blank (black with no power) and all the buttons do not work with the exception of the presets. Everything else still appears to work. If you drive for 20 minutes, the screen may come back to life for a min or two before going out again a couple times then it will stay off until the unit is shut off and cools down.

I have disassembled the radio, carefully looked at all the capacitors and replaced one capacitor that had a bit of orange residue on the top. None of the capacitors appeared to be bulging or misshaped.

I reassembled and i have exactly the same problem.

I really don't know what I'm looking at with this and I'm guessing there is a power supply component that is faulty. I have pictures and I"m looking for help in what components I should be looking at.

suggestions appreciated please

 

[shrtrnd]

Buy a can of 'freeze spray' from an electronics parts supply store.
Extend the radio power cord so you can have the radio chassis open and where you
can get at it (you don't NEED to hook up the speaker). Or 12VDC power supply on a workbench.
When the radio warms up, pin-point each component (probably an IC) with the freeze
spray. When the display comes back after you hit the right component, you've found
the problem.

 

[darot]

thanks for the reply, I just got of the phone with the shop that has the excluive contract to fix these (they want $500 bucks), its United Radio, I described the symptoms to them and they said the same thing, its a chip that you need a vga machine to replace. Does that sound right, is this beyond my backyard repair ability??

 

[shrtrnd]

The freeze spray will find the bad part (which fails when it's warmed-up)
The instant cooling of the IC with the freeze spray, will cause the IC to temporarily
start working again. That's how you ID the bad part.
Once you've identified the bad part, post the numbers on the device on this site, and
somebody will see if they can find a replacement for you.
The bad thing about a lot of car radio companies, is that they often put proprietary
identification numbers on the parts, so only they know what part to use to fix the radio.
Only way to find out if this is one of those companies, is to post the numbers here,
and somebody can help.
I don't know your skill level, or the circuit. Some parts are 'Surface Mount', which means
they're small and mounted flat on the board. It's not impossible for semi-skilled people
to work on these devices (and we don't know yet if you'll need to replace one of those),
but surface mount device replacement requires attention to detail.
See if you can find-out what failed, and we'll see if we can help.
good luck

 

[(*steve*)]

its a chip that you need a vga machine to replace

probably a BGA machine -- ball grid array.

This is a particularly nasty form of surface mount device.

They are difficult to examine (it requires x-raying) and the connections can be under huge stresses and may fracture.

You can attempt to repair them at home by heating the board and chip in an attempt to re-reflow the joints. I wouldn't recommend it.

 

[shrtrnd]

The repair shop guy probably knows his work.
But he's given you a diagnosis over the phone without even looking at your radio.
He probably is familiar with the problem and gave you the probable cause.
He's probably right.
He might be wrong.
I'd find the defective part before I turned my radio over to him, when he knows you've
already been given an estimate of $500.
My two cents worth. It's possible you've got a problem elsewhere.

 

[darot]

steve your reply sounds right in tune with what the shop told me. I am trying the freeze spray and will attempt to post a picture of the bad component. Hopefully by tomorrow.

 

[darot]

ok, i'm pretty sure this is the board that has the problem. i'm having trouble isolating the component because the board plugs in and you can't access/see it. When i do freeze spray blindly, it does come back on after cycling the key/electric.

do you see any likely candidates, from the video i looked at i don't see any bga chips, they must be under the silver steel covers? How do you get the covers off?

Should I just put the whole thing in the toaster oven for 3 min (after taking the lcd screen off)?

 

[shrtrnd]

Didn't you get a red plastic tube with the can of freeze spray, so you can direct the
mist with pin-point accuracy? (You push the tube into the nozzle)
Don't even consider toasting your board, there'll be all kinds of plastics in there and
you might do even further damage to the components or connectors.
I'm unfamiliar with these BGA devices *steve* was talking about. He'll probably get
on later to tell you what to look for.
I'd wait for further direction from *steve* or somebody else who knows the BGA devices.
I wouldn't try removing covers willy-nilly, if you mess the board up too bad, and the
problem IS this BGA device, the repair tech will want to charge you more money for
fixing any additional problems you send them.
My advice would be to try to make sure where your heat problem is, exactly.

 

[(*steve*)]

Unless the technician is telling you porkie pies, you should be able to find a (typically) relatively large square or rectangular black chip with no leads protruding from it and no visible solder joints.

Wikipedia has some useful details and photographs.

They're not always large, I have some 14 "pin" BGA chips that are about 3mm x 3mm. But generally speaking, problems arise for larger chips where differing expansion rates of the chip vs the board mean that the solder joints are under great stress when the board cools after soldering -- so look for something 10mm x 10mm or larger.

Once you've found it, have the radio assembled enough that it's operable and give the chip a quick blast of freeze spray. You may also be able to give the opposite side of the board a bit of a freeze if you can't get at the top.

If the problem appears (or disappears) when you do this (especially if it reverts after the board/chip have warmed again) then you have found your problem.

The DIY approach to reflowing BGA packages became "popular" with a particular game console which suffered huge problems in this area. The extreme hacker approach involved placing the board in a hot oven or something, but I wouldn't even consider that (for a whole host of reasons).

The approach I've guided a colleague through involves preheating the board to a temperature safely below the melting point of solder, then the application of hot air (above the solder melting point) to the top of the IC until you *think* the solder has melted. This is typically aided by a liberal application of liquid flux.

Personally, I wouldn't try this with anything that could be repaired professionally for less than the cost of a new item. I presume a new radio would be significantly more than $500?

This DIY fix almost certainly leaves the device with more stresses than when it was originally manufactured, using solder the second time from a process which is designed to be a once off operation. Even if it works, it may fail again soon after.

So, what I suggest is that you try to find a BGA package and confirm the fault is there. If it is, get it professionally repaired.

If you can't confirm it's the BGA package then you can try to discover if its something else.

Start by spraying relatively wide areas of the board to locate the general area of the fault, narrowing it down to (hopefully) a single component. Note that you may have to allow between a couple of seconds to a couple of minutes for the board to warm back up after each spray -- certainly after each spray that has some effect (either showing or resolving the fault)