cmt-bx77dbi DAB radio flashes tuning but is not tuning

statalite

statalite

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It's an approach commonly used by repair techs ..
Narrowing down the search area to a specific board ..
Then searching that board for any likely defects with high magnification.
gently flexing the board - if faulty- will cause the functionality to come and go.
We also use a gentle tapping action with something solid and non conducting ..but this may transfer movement to adjacent boards ..so isn't wholey conclusive.

rgds
VS
Well I just tried flexing the boards on their own, but nothing came of it, it was still flashing "Tuning" with no progress.
 
statalite

statalite

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This just doesn't look right ...
can't say for sure ..but looks like oxidsation or corrosion ..??
When I look close it looks like a white color and like tip-ex type thing. Does anyone else suspect it may be corrosion?

The capacitor C823 does not appear to be bulging or its flat on to however the negative photo change was interesting. It may look like the capacitors are leaking down the sides and the top but the sides have a different colour grey stripes on them as part of its identity.
Does there appears to be leaking on the top?
 
statalite

statalite

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My Satellite Setup
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Emailed an independent dealer that said they can supply any Sony parts, they asked questions about the tuner model number but haven't come back to me with a price yet.

Emailed an approved Sony repairer asking for a replacement tuner, was quoted £80.71 without VAT and delivery, with a no returns policy. No questions about tuner model number. Anyhow there's not a chance in hell I'm going for that offer.

Hope its the PSU board? :(
 
statalite

statalite

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My Satellite Setup
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I inspected the rear of the tuner and it has what appears to be a clear liquid around all the solder joints. I assume this is leekage meaning the tuner is of no use?
 

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2cvbloke

2cvbloke

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That clear stuff, if solid, is usually solder flux, an acidic material used to clean metal prior to or during soldering to make the solder stick...

If it is actually wet to the touch, then it could be a capacitor that has emptied itself, nothing that a bit of isopropyl alcohol couldn't clean up and a soldering iron fix... :)
 
statalite

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My Satellite Setup
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That clear stuff, if solid, is usually solder flux, an acidic material used to clean metal prior to or during soldering to make the solder stick...

If it is actually wet to the touch, then it could be a capacitor that has emptied itself, nothing that a bit of isopropyl alcohol couldn't clean up and a soldering iron fix... :)
It appears wet, but don't understand how it got there as its held upside down.

If I leave it will it affect performance?

Could I instead remove it with tissue and use a cotton bud to brush
isopropyl alcohol on the pins?
I don't understand the need for a soldering iron?
 
2cvbloke

2cvbloke

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If I leave it will it affect performance?

Could I instead remove it with tissue and use a cotton bud to brush
isopropyl alcohol on the pins?
I don't understand the need for a soldering iron?
If it's wet to the touch (rather than just looks wet), then something bad has happened on the board such as a capacitor leaking (which you do need to clean off as that can make a mess of solder joints and PCB tracks), but if it's hard, it's solder flux (perfectly normal), you can remove solder flux if you wish to as it can cause problems in later years, but most modern equipment dies long before flux paste ages enough to be a problem, it's not necessary to remove, just cosmetics really...

The soldering iron part is if a capacitor has given up the ghost and requires a replacement, but cross that bridge if we come to it... :)
 
statalite

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Might have a go at
If it's wet to the touch (rather than just looks wet), then something bad has happened on the board such as a capacitor leaking (which you do need to clean off as that can make a mess of solder joints and PCB tracks), but if it's hard, it's solder flux (perfectly normal), you can remove solder flux if you wish to as it can cause problems in later years, but most modern equipment dies long before flux paste ages enough to be a problem, it's not necessary to remove, just cosmetics really...

The soldering iron part is if a capacitor has given up the ghost and requires a replacement, but cross that bridge if we come to it... :)
I have dabbed it with toilet paper and a cotton bud and have come to the conclusion it must be solid and not wet, and so solder flux, I'm going with that.

So the only remaining option is to replace the capacitor(s)?
 
2cvbloke

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So the only remaining option is to replace the capacitor(s)?
Only if you find bad ones, with the PSU being the usual place for them as this is where they are stressed the most...

If any look bulged on top, swollen in the sides or have leaked from the top or base, those are the ones to replace, but only if you find them, if not, leave them be, as to properly check for bad caps involves a lot of fiddly hard work removing them and testing them with an ESR meter (not cheap in itself) which on something like a DAB radio really isn't worth the man hours, but the odd behaviour to me says there's a bad cap in there somewhere, as a bad cap can cause all kinds of odd behaviour, it's just a case of finding them...
 
statalite

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Only if you find bad ones, with the PSU being the usual place for them as this is where they are stressed the most...

If any look bulged on top, swollen in the sides or have leaked from the top or base, those are the ones to replace, but only if you find them, if not, leave them be, as to properly check for bad caps involves a lot of fiddly hard work removing them and testing them with an ESR meter (not cheap in itself) which on something like a DAB radio really isn't worth the man hours, but the odd behaviour to me says there's a bad cap in there somewhere, as a bad cap can cause all kinds of odd behaviour, it's just a case of finding them...
The problem is none of them look bulged or leaky to me, which one would question what the strange behaviour from the system is about.

I have touched the top of the caps multiple times now. If there's no visible signs im stuck as to how to progress.
 
statalite

statalite

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However I don't mind buying quality capacitors I just need help in pointing out where to buy.
 
2cvbloke

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The problem is none of them look bulged or leaky to me, which one would question what the strange behaviour from the system is about.

I have touched the top of the caps multiple times now. If there's no visible signs im stuck as to how to progress.
It could still be that there is a bad capacitor (E.G. one that has lost it's capacitance but looks perfectly fine externally), but without stripping them all out and testing with an ESR meter, it's hard to tell which one...

However, after some googling, it looks like this is a common fault in this model, though no solutions aside from sending it back to Sony under warranty, which ain't an option here...
 
statalite

statalite

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It could still be that there is a bad capacitor (E.G. one that has lost it's capacitance but looks perfectly fine externally), but without stripping them all out and testing with an ESR meter, it's hard to tell which one...

However, after some googling, it looks like this is a common fault in this model, though no solutions aside from sending it back to Sony under warranty, which ain't an option here...
For some reason I thought capacitors were reasonably priced. Maybe worth a go?
Having looked at a couple of website selling caps, I have no idea which type to choose in the category list? :/
 
2cvbloke

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For some reason I thought capacitors were reasonably priced. Maybe worth a go?
Having looked at a couple of website selling caps, I have no idea which type to choose in the category list? :/
Capacitors are reasonably priced, yes, but like I say, working out which one is the problem (assuming it's not a software bug that Sony missed/couldn't be bothered to fix) as I've said a few times, to find a bad cap that looks okay requires their removal and testing with an ESR meter, replacing them willy-nilly can be a wasted effort if it isn't one (or more) at fault, and if inexperienced with capacitor removal and replacement it poses the risk of permanent damage to the PCBs...

But as for which ones you need, you need to look at the ratings on the sides of the existing ones, for example a capacitor of 1000µF 6.3v 105°C should be replaced with one of the same rating (you can go higher voltage rating, but keep the capacitance, the µF (Micro Farad) value, the same) and same lead spacing (the distance between the pins of the capacitor), and try to pick 105°C capacitors as 85°C ones are prone to failure in hot environments. The type of capacitors you are after are mostly Electrolytic capacitors (as opposed to film, ceramic or tantalum types). And as for brands of capacitors, personally I prefer Panasonic caps, but other have their preferences...
 
statalite

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Capacitors are reasonably priced, yes, but like I say, working out which one is the problem (assuming it's not a software bug that Sony missed/couldn't be bothered to fix) as I've said a few times, to find a bad cap that looks okay requires their removal and testing with an ESR meter, replacing them willy-nilly can be a wasted effort if it isn't one (or more) at fault, and if inexperienced with capacitor removal and replacement it poses the risk of permanent damage to the PCBs...
In terms of the PCBs I could break is this limited to the modular dab one I have removed or the rest of the unit?
 
2cvbloke

2cvbloke

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In terms of the PCBs I could break is this limited to the modular dab one I have removed or the rest of the unit?
It depends on where you pull the caps from, if you just pull caps of that particular board it'll be limited to that one, the damage usually done (and I'm guilty of this in the past!!) is lifting the tracks off the board, either from applying too much heat or trying to force the pins out, which is a PITA to repair satisfactorily, and if it's a multi-layer board (doesn't look to be in this case), the damage can be done inside of the board which means it's scrap...
 
statalite

statalite

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My Satellite Setup
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It depends on where you pull the caps from, if you just pull caps of that particular board it'll be limited to that one, the damage usually done (and I'm guilty of this in the past!!) is lifting the tracks off the board, either from applying too much heat or trying to force the pins out, which is a PITA to repair satisfactorily, and if it's a multi-layer board (doesn't look to be in this case), the damage can be done inside of the board which means it's scrap...
I take your advice, thank you. I concider the board as already scrap as I'm not using it. The rest of the system works without it, so I think a few pennies on some caps would be worth a go. :)
 
Channel Hopper

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Looks like you are not alone

https://community.sony.co.uk/t5/hi-fi-systems/cmt-bx77dbi-dab-just-flashes-tuning/td-p/1336708

There is a small chance the earthing of the boards in the unit is not perfect, and static/power supply voltages have caused the DAB logic chip to freeze. You could try wrapping the DAB board in foil for a few minutes, which will ground all components to each other, releasing any build up of voltage. There may also be a specific chip reset (often these are short two pins whilst the receiver is powered up (on the picture, pin 19 of the board connector mentions 'sys reset', which may be the way forward.
To go into the specific chipset reset you will need to supply the chip model number for IC803.

Without a firmware port though it is highly unlikely much else will help.
 
statalite

statalite

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My Satellite Setup
Nova-HD-S2, Dr HD D15, V7S
Zone 1 @ 28.2°E with cable tied LNB @ 19.2°E
Channel Master 1.0m (to be setup)
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My Location
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Looks like you are not alone

https://community.sony.co.uk/t5/hi-fi-systems/cmt-bx77dbi-dab-just-flashes-tuning/td-p/1336708

There is a small chance the earthing of the boards in the unit is not perfect, and static/power supply voltages have caused the DAB logic chip to freeze. You could try wrapping the DAB board in foil for a few minutes, which will ground all components to each other, releasing any build up of voltage. There may also be a specific chip reset (often these are short two pins whilst the receiver is powered up (on the picture, pin 19 of the board connector mentions 'sys reset', which may be the way forward.
To go into the specific chipset reset you will need to supply the chip model number for IC803.

Without a firmware port though it is highly unlikely much else will help.
Thanks, yes I did lots of google searches and someone had experienced the same but unfortuantly had no replies.

For earthing I take it you mean "tin foil"?

On the picture of the yellow board on the back it lists 30 things, I think these refer to the 30 gold pins from the green board. I wonder what will happen if I jumpered pin 19 to another, however I cannot work out which side 19 is on?

Would it just be case of jumpering it for a few seconds while on, then removing the jumpers and everything is back to factory?

All the model numbers I have would be what is in the pictures, if I can be of any help interpreting them i will.
 
Last edited:
statalite

statalite

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My Satellite Setup
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i have now worked out pin 19!

do i only jumper pin 19 or with one other?
 
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