Serious HDMI Problems. What's that smell? Burning Raspberry!


62 posts   Page 2 of 3   1, 2, 3
by mad-hatter » Sun Jul 08, 2012 8:56 am
Thanks to all for replying.

Hello mahjongg,
Thanks, I missed the earlier post. (PMEG2010AET)

Hello davidw ,
Using the diode test on my meter, I get 535 for a standard power diode,
and 243 for the BAT54. Meter leads reversed for both diodes no reading.

Using the resistance test, I get 109Kohm for a standard power diode,
and 16.9Kohm for the Bat54. Meter leads reversed for both diodes no reading.

I don't kmow what the CEC line is or means.

Hello pwinwood,
How did you break out the 5V line, an adapter of some sort and strip the cable.


Hello mahjongg,
The BAT54 seems to be OK from the test and my limited knowledge of electronics.
Please correct me if I'm wrong.


Regards
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by pwinwood » Sun Jul 08, 2012 10:09 am
Hello mad-hatter,

You asked: How did you break out the 5V line, an adapter of some sort and strip the cable?

I took the HDMI converter apart - this was quite easy, with gentle pressure on the HDMI lead and it's bush in the case the circuit board pops out the other side still attached to the VGA connector.
I measured continuity from the 5v feed on the HDMI plug to pins on the TD6810 switch mode regulator chips on the converter board. I then found a large pad on the underside of the circuit board that was was also part of the 5v distribution circuit. Then I found an old USB lead and clipped off the mini-USB connector on one end. I drilled a hole in the HDMI converter case and fed the USB lead through. I identified the 5v and Gnd wire on the USB lead and soldered the wires to the large pad (having scraped the lacquer off) and ground plane on the circuit board. The attachment shows the pads on the underside of the circuit board that i soldered to.
I also clipped all the whiskers of wire from around the HDMI cable termination at the circuit board as they were very untidy and could cause a short. Some of the soldering does not look very good to me - something for another day.
Attachments
hdmiconverter1.jpg
HDMI converter underside.
hdmiconverter1.jpg (20.44 KiB) Viewed 7445 times
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by mad-hatter » Sun Jul 08, 2012 2:07 pm
Hello pwinwood,

Thanks I'll have a play tomorrow.

Regards
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by davidw » Sun Jul 08, 2012 2:11 pm
The diode readings sound OK; they are basically reading the forward voltage drop and Shottky diodes have a low forward drop. That is why they are being used here.

The CEC line is used for sending remote control commands. It is pin 13. It is optional, but needs to be properly terminated, even if not used.

I forgot to mention that the I2C lines are also clamped in the same way, which probably violates i2c, however I'm not sure that i2c was ever intended for use with multiple, independent power supplies.
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by mad-hatter » Mon Jul 09, 2012 6:29 pm
Hello,

I'm in the middle of my playtime.

I have got hold of a 5V 1.5A regulated power supply, which I
can use to power the Pi and the adaptor as per pwinwood's mail.

I've also got one end of a micro USB cable (the right end).

Stripping back the cable I've got 4 wires (Red/white/black/green) and the screen.

My measurements show the 4 wires to be tied together (5 Volt line),
and the screen to be the neautral line.

Can somebody confirm this is correct, before I bake the Pi.

Regards
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by mahjongg » Mon Jul 09, 2012 6:58 pm
If its a genuine micro USB cable it should be fine in principle, there are no known wiring variations when using a micro USB connector, what is +5V and what is GND is strictly normalized.
Thats said, on the PI only pin 1 (VBUS) and pin 6 (GND) are connected to VCC and GND, all other pins (D-, D+, ID) are not connected.
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by Jens » Thu Jul 12, 2012 5:54 pm
I managed to toast the HDMI output today as well with the Neewer Black HDMI.
Had read that it should work with the Raspi - which it did for a while but after an on/off switching after ~30 minnutes the monitor just stayed black.
Tested D1 (and the other diodes surrounding the HDMI socket) with a multimeter, voltage drop is 0.2V so looks ok, but the HDMI does not work anymore even with a proper HDMI monitor.
Fortunately I had enabled SSH and installed vnc and twoftp so I can still use it in headless mode.
It seems to me that the HDMI output is too fragile if it can be toasted by connecting an external device which does not send any dangerous signals back to the Raspi, a faulty cable seems to be all it takes judging by the discussion here.
Apart from that, it is an incredible little machine for which I have many uses.
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by mahjongg » Thu Jul 12, 2012 6:10 pm
Not the fault of the Raspberry Pi, which was not designed to attach to external HDMI to VGA converters, only to monitors and TV, where the diode was only used to provide about 50mA typically (to power a very small permanent memory containing a few dozen bytes describing the capabilities of the monitor.)
Not devices that try to pull 400mA through that connection, that is rated for 50mA, just as HDMI specs demands.

It not a faulty cable, it a user connecting a faulty device, that doesn't adhere to HDMI specs, to save in price, by not including an external power source, as it should have. There is a reason this device is much cheaper than conventional converters, its too cheap!
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by Jens » Thu Jul 12, 2012 6:28 pm
Hi pwinwood,
Which is the +5v wire from the hdmi side, the red wire just above the pad?
I take it that this should be cut so to prevent the converter taking power from the Raspi if the power to the converter is off.
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by davidw » Sat Jul 14, 2012 10:17 am
It not a faulty cable, it a user connecting a faulty device, that doesn't adhere to HDMI specs, to safe in price, by not including an external power source, as it should have. There is a reason this device is much cheaper than conventional converters, its too cheap!


The problem is that you are connecting two non-compliant devices together. The Pi is, at best compatible. I'm not convinced that it is even compatible when powered down.

There is a specific requirement that shorts must not damage a fully compliant device.

The problem with compatible, but non-compliant, devices is that they are only certain to work if the other side is fully compliant. In this case you have a device that is non-compliant in that it sinks more than 10 mA when powered up and more than 55 when powered down, and another device that is non-compliant because it is not current limited to no more than 500mA and cannot tolerate a short circuit.
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by Jens » Sun Jul 15, 2012 2:35 pm
I think that describes the situation very accurately.
I used the info from pwinwood's description + some additional probing/measuring and modified the converter using an old mobile charger (5V/460mA spec) as external power supply. I also identified and cut the +5V wire from the hdmi cable in the converter so that it cannot take any power from the Raspi hdmi interface e.g. if the converter ps is not plugged in. It turned out to be an easy and clean mod. After verifying that it worked with a PC with hdmi output I then connected the pi to the converter without much hope but it turned out that the interface on the pi was not damaged after all.
It wouldn't work yesterday with a standard hdmi monitor but today it seems to be back in full working condition.
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by mahjongg » Sun Jul 15, 2012 2:42 pm
In this case you have a device that is non-compliant in that it sinks more than 10 mA when powered up and more than 55 when powered down

Errrr, what? care to explain that, I'm not getting it. Are you referring to the PI? What does it "sink" to?

If the HDMI output is really shorted, the input fuse on the PI should blow almost immediately, before the BAT54 gets time to burn out.

In any case such a clause in the specs isn't an excuse to use eight times more current than is allowed in the specs.

Using a BAT54 is one of the many places where cost have overruled the wish to make a "technically perfect device", and its an obvious choice, even if it negatively effects a very small minority who against all warning that the PI doesn't support VGA monitors still insist in wanting to use them, even though a well designed converter would cost much more than a second hand DVI-D monitor.
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by pinoccio » Fri Nov 09, 2012 3:46 pm
Thanks pwinwood.
I've made the same modification to my HDMI-2-VGA adapter... and it works just fine :)
See the gallery: http://imgur.com/a/sLogs/all.
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by Anton_Belarus » Thu Dec 20, 2012 7:25 am
How to make external power supply for HDMI-VGA converter like this one http://www.ebay.com/itm/290701005022?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649
Here is converter
Image
First of all we need to open it. For that's reason we need knife or something like that to take off cover
Image
Here is converter circuit
Image
On the bottom left side we need to cut off red wire, that goes to hdmi side. Later we must solder to 5V pad 5V wire from external power supply(on picture I desolder and cut off red wire).
Image
Make hole for external supply cable and put it through this hole
Image
Image
As external power supply I used USB connector, that's why I check where 5V and GND wires(in my case black wire - Gnd, red - 5V)
Image
On the top side placed GND pad, here we must solder GND wire from extsupply. remaining wires we must cut off or isolate
Image
Using gluegun fill voids.
Image
All done
Image

Traditionally - sorry for my bad English =)
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by PacificDragon64 » Sun Jan 20, 2013 8:22 am
i am soo disappointed to read this thread after i purchased what looks to be this same device from Adafruit.

http://adafruit.com/products/1151

I am now totally confused. I was under the distinct impression that Adafruit was a trusted seller and sponsor of "safe" RaspberryPi accessories. Their description of this device leads me to believe that it works safely on the Pi.

"We tried this out with a Raspberry Pi and an old VGA monitor we had and found the display output to be very crisp and vivid. For use with a Raspberry Pi we suggest editing config.txt to set "hdmi_safe=1" output for best results (otherwise, the Pi may not 'recognize' the HDMI display and revert to composite output)"

Is this in fact the very same device described here in this thread?
Do I need to return it for fear of damaging my Pi?

Any help here would be greatly appreciated. Thanks in advance.

Disappointed in Vancouver.
Cheers!

:-)
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by jamesh » Sun Jan 20, 2013 8:59 am
PacificDragon64 wrote:i am soo disappointed to read this thread after i purchased what looks to be this same device from Adafruit.

http://adafruit.com/products/1151

I am now totally confused. I was under the distinct impression that Adafruit was a trusted seller and sponsor of "safe" RaspberryPi accessories. Their description of this device leads me to believe that it works safely on the Pi.

"We tried this out with a Raspberry Pi and an old VGA monitor we had and found the display output to be very crisp and vivid. For use with a Raspberry Pi we suggest editing config.txt to set "hdmi_safe=1" output for best results (otherwise, the Pi may not 'recognize' the HDMI display and revert to composite output)"

Is this in fact the very same device described here in this thread?
Do I need to return it for fear of damaging my Pi?

Any help here would be greatly appreciated. Thanks in advance.

Disappointed in Vancouver.


Note that the original thread is pretty old now, so the information in it may be out of date. Check with Adafruit to ensure that the device is safe.
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by DanielChai » Mon Jan 21, 2013 5:47 pm
mahjongg wrote:Yes, all of the above is true.
Note that the more expensive (well built ones) use external PSU's, which is what I would expect if they contain frame buffers etc.
The extremely cheap "cable powered" ones probably only contain LVDS receivers, deserializers, and simple resistor ladder D/A converters for R G and B. And make no attempt to change anything in the signal resolutions and timings, just turn the HDMI LVDS signals into analog signals and sync signals.
They probably also usurp the power that would otherwise go to the monitors EEPROM, that is why you cannot get any monitor info, they need every mA.


Really good point.

Most people using hdmi-vga converter do not use a very high resolution vga monitor. A typical one, say 1024x768@60Hz, does not require as much power as a 1980x1080 one.I can't help to wonder whether this would help if one:
1. forces the Pi to output a low resolution hdmi instead of the default one
2. turn off the hdmi audio output to save some current
and then use the adapter.

I didn't try myself. just wondering..

I found this page might be helpful
http://www.amazon.co.uk/review/R29NB3DW ... lectronics

Another thought I have is replacing D1 with a diode allowing more current, as suggested by [quote="mahjongg"]. But this will probably burn the fuse too. I saw some people played with the fuses to allow the Pi drain much more current. I am not sure whether this is good for the Pi or not, but considering how much time and effort and risk it takes to modify the Pi, it might be better to play with the hdmi-vga adapter. For example, do a little soldering job and have the adapter powered by external 5V power supply like a powered usb hub
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by nerdynernerd » Fri Jan 25, 2013 12:01 am
For an easy solution that worked for me please see what I posted here.
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by arunagirinathar » Thu Mar 21, 2013 6:37 pm
pwinwood wrote:For what it is worth I have measured the current consumption of the "Neewer Black HDMI Input To VGA Adapter Converter" to be 400mA. There are two 800mA switch mode power supply chips in the Converter. Therefore it is likely to damage the diode on the Raspberry Pi board. To fix this I have added a separate power lead to the Converter to feed it with 5v from the USB hub - the power lead has a USB connector on the end of it. No current is consumed now from the Raspberry Pi HDMI interface because the protection diode is reverse biased.


Could you kindly post pictures/schematics of how you went about doing this ?
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by pwinwood » Thu Mar 21, 2013 10:12 pm
arunagirinathar wrote:Could you kindly post pictures/schematics of how you went about doing this ?


Not really it was a while ago and the adaptor is now sealed up and in situ.

I can however tell you how I did it. I identified the +5v and GND pads as per my photo earlier in the thread and connected them to my bench power supply set at 5.0v out. I then plugged the 'Newer' adaptor into the Pi's HDMI port and the VGA port of the monitor - the Raspberry Pi is separately powered from another 5.0v power supply so that the protection diode is not conducting; also there was no change in current consumption of the PI when the HDMI port was connected to the 'Newer' adaptor and when connected to the HDMI port of the monitor. I then powered up the PI and the Newer adaptor and then observed the current consumption on the current meter on the power supply connected to the Newer adaptor. The current consumption stablilised at 400mA.

However the absolute current consumption is not important - as has been suggested it could depend on the display resolution - just that it was more than 200mA limit for the protection diode. I also observed that the Newer adaptor had very poor construction - bare wire whiskers and dry solder joints - which I have rectified. In my opinion this alone makes it unsuitable to use with the Pi without modification and is a potential reason for the failure that caused this thread to be started. Why the interest?
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by arunagirinathar » Sat Mar 23, 2013 7:59 am
pwinwood wrote:Why the interest?


I recently purchased a similar device from e-bay advertised as 100% compatible with Nexus (??) and Raspberry Pi only to find that ebay was full of scams (?) a week ago on elinux.com and that such boards could burn Pi's Diode and plausibly even cause the whole board to wreck.

Given at http://imgur.com/a/sLogs#0 are instructions for modding a similar device; only the board schematics are not even similar to the one I got a few days back.

Thus the interest.

Regarding the images, I just noticed them. And based on what I've read so far on this topic, it seems that there are probably more than a dozen models of this shanty product.

If you could give some hints as to how you figured the +ve and -ve leads, it would be very helpful; so that irrespective of the board layout and model, enthusiasts could mod them.

The board I got, has an even shabbier hot-glue squashed all over the HDMI contacts. I'll soon post a photograph of the board, I got.
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by Buda » Sat Mar 23, 2013 11:08 am
on the cable side trace Pin 17 (DDC,CEC,Ground) and Pin 18 (+5VDc) back to the adapter board.
http://static.ddmcdn.com/gif/hdmi-connector-diagram.gif
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by arunagirinathar » Sat Mar 23, 2013 1:06 pm
Thank you for the information.
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by midix » Sat Jul 27, 2013 2:44 pm
Hi all.

I recently bought Raspberry Pi to use as an Openelec media center with my old VGA monitor.

Already tested vith composite video and NOOBS software - works fine.

Now my HDMI->VGA adapter arrived. It's this one:
http://www.ebay.com/itm/271081462659

but it looks a bit different than all the others mentioned in this thread. Here are the images of its internals (excuse me for the quality, shot with a cellphone)
Image
Image

I tested it with my PC video adapter, and it works fine. Now I want to use it with my Rasp, but I don't want to burm the Rasp. I have a Plugable USB hub which provides almost 3A for powering my Rasp and other USB devices. I would like to use it to power also the HDMI->VGA adapter.

Should I assume that the last red wire in my images is the +5V? I intend to cut it and attach a USB wire instead.

I guess, I could just measure the voltage on the red wire (I have a cheap multimeter) but I'm not sure that if I find +5V then it will be the power wire. Aren't there any other wires on HDMI, which could also measure +5V but which are not meant for power supply?
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by drgeoff » Sat Jul 27, 2013 3:59 pm
Goodness know how they can make that and ship it half way round the world for US$0.99 !!

Edit: They don't. That price only applies to the right angle adapter.

I see at least two red wires. Also, although it is an often used convention to use red for +ve power it is not mandatory. Injecting 5 volts where it isn't wanted won't do any good at best and may be fatal to the converter at worst. The way to be sure is to look at the pinning diagram at http://en.wikipedia.org/wiki/HDMI and use the resistance range of a multimeter to identify which wire at the PCB end of the cable is wired to the +5v pin at the HDMI plug.
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