Magnavox 32MF369B/F7 volume stuck

[dick_barton]

Re: Magnavox 32MF369B/F7 volume stuck

Can you use your meter set to ohms and with the set powered off and measure across the solder pads as shown in the photo.

First connect across Volume Up Button and take a reading without pressing the button and then another reading when pressing the the button.
Repeat with the Volume Down button.

Volume Up Not Pressed = xx Volume Up Pressed = yy
Volume Down Not Pressed = zz Volume Down Pressed = zz

[hairywbush]

Re: Magnavox 32MF369B/F7 volume stuck

This forum is not notifying me of responses anymore!! Sorry about that.
I used my other multimeter. Looks like it's doing what it's supposed to...
At your exact points, I got infinite for volume unpressed, and 1.1 for volume up pressed, volume down measured infinite for volume not pressed, and 1.1 for pressed.

[dick_barton]

Re: Magnavox 32MF369B/F7 volume stuck

I'll assume that the 1.1 measured is ohms. If so then the buttons are working as they should.

[hairywbush]

Re: Magnavox 32MF369B/F7 volume stuck

yes ohms...and yea that's what I'm saying so what now?

[dskall]

Re: Magnavox 32MF369B/F7 volume stuck

Have you tried firmware update or reset?

[hairywbush]

Re: Magnavox 32MF369B/F7 volume stuck

how do you do either? and does the reset procedure work with all makes and models?

[bman4]

Re: Magnavox 32MF369B/F7 volume stuck

i think you can turn tv on then disconnect buttons and if it stops get some lubricating crc contact cleaner.

button might be shot from many hard pressed so i actaully recommend just buying a new button board.

[Agent24]

Re: Magnavox 32MF369B/F7 volume stuck

Considering how many dodgy tactile buttons I have replaced, I'd replace the lot just to see what happens. They don't always test out obviously bad on a multimeter either.

Also, it looks like this board uses analogue voltage sensing with the buttons and resistors all in a "ladder" arrangement.

This means it's entirely possible for some of the other buttons to go faulty, and cause a completely different button to seem bad, because the IC does not address the buttons individually as it would if they were read digitally.

[hairywbush]

Re: Magnavox 32MF369B/F7 volume stuck

i think you can turn tv on then disconnect buttons and if it stops get some lubricating crc contact cleaner.

button might be shot from many hard pressed so i actaully recommend just buying a new button board.

was wanting to do this initially, however they are soldered. I think that's where I might be headed real soon though

Considering how many dodgy tactile buttons I have replaced, I'd replace the lot just to see what happens. They don't always test out obviously bad on a multimeter either.

Also, it looks like this board uses analogue voltage sensing with the buttons and resistors all in a "ladder" arrangement.

This means it's entirely possible for some of the other buttons to go faulty, and cause a completely different button to seem bad, because the IC does not address the buttons individually as it would if they were read digitally.

are you saying it might not be the button board? because I get your trickle down effect scenario. how would I know
also I'm interested in taking one of the simplest steps such as this reset or update that was mentioned. anyone want to add to that?

[Agent24]

Re: Magnavox 32MF369B/F7 volume stuck

I'm saying it would not surprise me if the buttons on the button board were faulty.

You can buy new switches very cheap to replace them with.

[hairywbush]

Re: Magnavox 32MF369B/F7 volume stuck

update
I turned the tv on to try something and noticed the volume wasn't showing 100% like it was. I was able to access the menu without it going crazy, however I could not easily access the options 100%. something was still off. So, I went to try and program this universal remote. I got the remote to turn it off but not on so I had to do something else...well anyway, I turned the tv on and it's back to its old self, showing 100 volume and menu going whacky.

[hairywbush]

Re: Magnavox 32MF369B/F7 volume stuck

bump
I want to buy a new button board, but this is the closest I've found https://encompass.com/item/8088635/P...ction_Assembly

the site has this listed under my model, but it has extra boards attached.

[Agent24]

Re: Magnavox 32MF369B/F7 volume stuck

There's no need to, just replace the switches with brand new ones and check that the resistors on there haven't failed. If that doesn't fix it, then the problem is something else...

If you don't feel confident about the soldering, send it to someone who is. Lots of people on this forum, I'm sure you could find someone to help you out!

[vinceroger69]

Re: Magnavox 32MF369B/F7 volume stuck

Considering how many dodgy tactile buttons I have replaced, I'd replace the lot just to see what happens. They don't always test out obviously bad on a multimeter either.

Also, it looks like this board uses analogue voltage sensing with the buttons and resistors all in a "ladder" arrangement.

This means it's entirely possible for some of the other buttons to go faulty, and cause a completely different button to seem bad, because the IC does not address the buttons individually as it would if they were read digitally.

i have now had a few older ccfl tvs where as you say the switch tests fine but set still plays up i replaced all the tactile buttons and cleaned pcb with cleaner to remove all flux etc and set 100% fine afterwards i think ive done 3 now with this type of fault volume always high or low or menu stuck on screen etc

[hairywbush]

Re: Magnavox 32MF369B/F7 volume stuck

There's no need to, just replace the switches with brand new ones and check that the resistors on there haven't failed. If that doesn't fix it, then the problem is something else...

If you don't feel confident about the soldering, send it to someone who is. Lots of people on this forum, I'm sure you could find someone to help you out!

when you say switches, do you mean the buttons, and do you mean all of them?

[Agent24]

Re: Magnavox 32MF369B/F7 volume stuck

i have now had a few older ccfl tvs where as you say the switch tests fine but set still plays up i replaced all the tactile buttons and cleaned pcb with cleaner to remove all flux etc and set 100% fine afterwards i think ive done 3 now with this type of fault volume always high or low or menu stuck on screen etc

Yeah, it's pretty weird. I've seen it mostly on LCD monitors and even on a cheap CRT TV - and you're right - electrical tests don't usually show anything wrong, either, except for just one button which had (on testing) a very intermittent ~30 Ohm short.

My theory is that they go electrically leaky (for whatever reason - contamination\wear\defect\tin whiskers(?)) just enough to upset the high-impedance inputs or confuse the ADC on the microcontroller.

I also wonder if these buttons expect to be self-cleaning, and if the current through them in these applications is too small to do it.

when you say switches, do you mean the buttons, and do you mean all of them?

Yes and likely yes. In my experience, if one has gone bad, the rest often follow suit in quick order. So if you're going to the trouble to replace one, you might as well replace all of them at the same time, and avoid the hassle of having to go back in and replace another a month later. (Lesson I learned from the first time I encountered this problem)

The other problem is, that it's hard to find out which one is actually the problem. Like vinceroger69 also experienced - electrical tests don't typically show any symptoms of a fault, and with the analog resistor ladder\divider types (like yours here) the control which *seems* stuck may not correspond to the actual bad button, because the ADC in the microcontroller doesn't actually know which button it's reading, it just measures the voltage coming out of the string.

When you have several buttons all chained on a 5v or 3.3v supply, the voltage difference to distinguish between each one is pretty small. If a button or buttons is leaky, it throws off the voltage reference and the ADC reads the voltage output as the wrong button.

Therefore I find it much more time-efficient and a way to provide insurance against repeat faults to just replace the whole lot at once.

Of course, the problem might.. MIGHT.. be a bad resistor, maybe one that's gone high in value, but that's pretty unlikely. You could easily verify those with a multimeter though. You'd still have a bad button somewhere though, as a resistor by itself wouldn't cause the control to be stuck, just get read incorrectly.

[hairywbush]

Re: Magnavox 32MF369B/F7 volume stuck

ok I see what I have to do now. I just have to measure the buttons because there's several different sizes

[Agent24]

Re: Magnavox 32MF369B/F7 volume stuck

Yes, make sure the actuator (the white plastic bit) is about the same length as the originals. Some slight difference might be OK depending on the tolerance of the case\panel.

The actual button housing is a fairly standard form factor, but check you get the right version (right angle)
Also, bear in mind that stock photos of products are not always accurate, check the datasheet or description to be sure.