PS4 HDMI output damaged with oscilloscope? - Page 1
Forum section: electronics / beginners

author: d3l
author_rank: Newbie
timestamp: August 21, 2015, 08:02:49 pm
content: Hey, I'm new to this forum so I just gonna go for it:I recently tried to measure the clock speed of the HDMI Signal sent from my PS4.My setup was as follows:- PS4 connected to mains voltage (with Phase and Neutral, no earth ground connection)- My Oscilloscope (MSOX3104A for reference) connected to mains voltage with all three pins connected (Phase, Neutral, Earths Ground).- The oscilloscope probe was connected to TMDS_CLOCK- (GND) and TMDS_CLOCK+ (RPOBE).- I used a cut open HDMI cable to connect the probe from the oscilloscope to the hdmi signals. (one end was plug into the PS4, the other end was floating).- Input impedance of oscilloscope was 1MOhm.To my surprise, after my measurement the PS4 was unable to send a valid HDMI signal to my TV.I tried multiple cables and a different TV and didn't get any signals.I also tried multiple PS4 resets with no effect (safe boot, hdmi signal reset).I'm really confused since I see no way I could damaged the HDMI port with my measurement.Is there something I am missing? What did I wrong?For reference, I also asked on stackoverflow but only got some strange answers:http://electronics.stackexchange.com/questions/186620/hdmi-port-damaged-with-oscilloscope(I also did ask a trained electronics engineer and he couldn't tell me what went wrong)I really appreciate any help.Thanks

author: miguelvp
author_rank: Super Contributor
timestamp: August 21, 2015, 08:11:12 pm
content: QuoteQuoteYou pretty much shorted TMDS_CLOCK- and fried something.Edit: next time use differential probes, or use two channels and loose the ground leads.

author: d3l
author_rank: Newbie
timestamp: August 21, 2015, 08:13:11 pm
content: I guess, but it makes no sense to me, the PS4 should be floating.

author: miguelvp
author_rank: Super Contributor
timestamp: August 21, 2015, 08:14:26 pm
content: your scope ground is earthed.

author: d3l
author_rank: Newbie
timestamp: August 21, 2015, 08:17:35 pm
content: I'm sorry but you are telling me something I already know

author: tautech
author_rank: Super Contributor
timestamp: August 21, 2015, 08:20:36 pm
content: Quote from: miguelvp on August 21, 2015, 08:14:26 pm+1And then so is the reference lead on your probe.

author: miguelvp
author_rank: Super Contributor
timestamp: August 21, 2015, 08:21:16 pm
content: There is a voltage differential between the signal and the probe ground, so that is a short circuit.Probably not many volts but enough to kill the HDMI chip.

author: sync
author_rank: Frequent Contributor
timestamp: August 21, 2015, 08:23:54 pm
content: With only the power connection I measure ~100Vac between the PS4 ground and protective earth. In current mode I get 4.6uAac. There are capacitors between mains and ground in the PS4 which causes this.I think you fried TMDS_CLOCK- when you connect it to earth via the scope ground.

author: d3l
author_rank: Newbie
timestamp: August 21, 2015, 08:25:23 pm
content: Just FYI:The HDMI specifications guarantees that shorting any pin combination on the HDMI cable will not harm the sink or source.QuoteSo you are saying the PS4 is not isolated from earths ground? This sounds insane

author: Gyro
author_rank: Super Contributor
timestamp: August 21, 2015, 08:32:51 pm
content: The PS4 will have 'Class Y' Capacitors from both supply lines to chassis for interference suppression, typically 2.2nF. The moment you connected your scope ground to TMDS_CLOCK- you will have discharged these at roughly 1/2 mains supply voltage into the HDMI chip.

author: marshallh
author_rank: Unknown
timestamp: August 21, 2015, 08:36:07 pm
content: Even if you probed it properly you wouldn't see much of a clock if any. At 1080p60 the clock is 1.5gbps (1.5ghz) which is going to be invisible to your passive probe. Passive 10x probes start to become increasingly useless past about 20mhz. By 200mhz you are really pushing their limits.To actually see something you'll need a 1ghz analog bandwidth scope or better and a Z0 probe, or a diff probe of sufficient bandwidth.

author: wraper
author_rank: Unknown
timestamp: August 21, 2015, 08:37:49 pm
content: Quote from: d3l on August 21, 2015, 08:25:23 pmRather you sound insane. Double insulated PSUs usually have Y1/Y2 safety rated capacitors (few nF) between mains and GND on secondary side. What happened is that you discharged such capacitor (which likely was charged to about half of the mains voltage) into TMDS_CLOCK-

author: Gyro
author_rank: Super Contributor
timestamp: August 21, 2015, 08:39:31 pm
content: Y1 by the way

author: d3l
author_rank: Newbie
timestamp: August 21, 2015, 08:43:14 pm
content: Quote from: wraper on August 21, 2015, 08:37:49 pmThanks, this sounds right. I didn't know there are capacitors between the secondary side and mains earth.

author: wraper
author_rank: Unknown
timestamp: August 21, 2015, 08:45:14 pm
content: Quote from: marshallh on August 21, 2015, 08:36:07 pmNo, clock is much lower1080p/60/8 bit per color is 148.5 Mhz

author: marshallh
author_rank: Unknown
timestamp: August 21, 2015, 08:45:29 pm
content: The good news is that you can get a new Panasonic HDMI transmitter on ebay for $25. You will need hot air to swap the chips. Also replace any ESD clamps on the TMDS lanes as well.Quote from: wraper on August 21, 2015, 08:45:14 pmI stand corrected. You should be able to see that clock OK with passive probes, provided you keep the return paths short.

author: d3l
author_rank: Newbie
timestamp: August 21, 2015, 08:49:06 pm
content: Quote from: marshallh on August 21, 2015, 08:45:29 pmIs there way to sneak that into warranty? I mean how could you tell I blew the chip?

author: Gyro
author_rank: Super Contributor
timestamp: August 21, 2015, 08:59:11 pm
content: Theoretically it is a problem that could occur due to live plugging of the HDMI cable (although in practice the connector shield sould always make contact first). It also depends what the connector contacts look like after your probing.

author: wraper
author_rank: Unknown
timestamp: August 21, 2015, 09:31:15 pm
content: Quote from: d3l on August 21, 2015, 08:49:06 pmWell, if you didn't open the case, then only conscience would stop you from doing this.

author: C
author_rank: Super Contributor
timestamp: August 21, 2015, 09:46:34 pm
content: If the PS4 was truly floating,then grounding TMDS_CLOCK-The PS4 circuit ground & power plains would need to change at TMDS_CLOCK- rate.The part of the PS4 is trying to be an antenna.C

author: d3l
author_rank: Newbie
timestamp: August 21, 2015, 09:50:19 pm
content: Quote from: wraper on August 21, 2015, 09:31:15 pmYeah, better shove some more money up in Sonys ass, no.EDIT:Some afterthoughts:How does sony know which pin actually is ground? I mean I can easly swap the plug and Phase and Neutral are swappedDoes it matter? (Regarding safety etc.)

author: homebrew
author_rank: Frequent Contributor
timestamp: August 21, 2015, 10:09:33 pm
content: Quote from: d3l on August 21, 2015, 08:43:14 pmIt might actually be even worse. In a lot of these digital systems (i.e. AT/ATX computers) the system ground is directly tied to mains earth.Y capacitors are sometimes as large as 4n7. (i.e.http://elektrotanya.com/PREVIEWS/power_supply/power_supply_vegyes/23432455/pc_atx-at/atx_200_pc_power_supply_sch.pdf_1.png)4n7@50Hz => Z ~= 670kSo basically a capacitive voltage divider that will serve you 163 V peak-to-peak and deliver up to 0.25mA.Hmm, not so nice for the input protection diodes om the chips ...But maybe, if you are really lucky there are some ESD filters on the board that have been fried and could potentially be replaced ...

author: Chris C
author_rank: Frequent Contributor
timestamp: August 22, 2015, 01:56:35 pm
content: Quote from: d3l on August 21, 2015, 09:50:19 pmLet's say that you do swap the plug, and that the PS4 and TV are initially disconnected from each other. Thanks to the Y1 capacitors, each piece of equipment has a different ground.Now you connect them via HDMI cable. The first thing to make contact is the metallic shell of the plug, which connects as a ground terminal, and it's very deliberately designed this way. Because there will be an initial surge of current through it, as the differing grounds equalize. And a bit of continuing current through it as the Y1 capacitors fight each other. But no damage is done.But what if the first connection was through an analog 1/8" audio cable instead? Upon insertion of the plug into the second piece of equipment, tip will come in contact with ground first, routing that initial surge through the audio input/output of the first piece of equipment. Hopefully it's designed properly, in a way that it can survive this (but this isn't always the case). Assuming it does, and the connection is completed, the continuing current through ground can cause hum in the analog audio signal. An issue the HDMI connection doesn't have, since it carries only signals which are digital, and differential.From my reference library, here's someone else who wrote about this damage/interference mechanism:http://sound.westhost.com/articles/external-psu.htm#kil

author: trigger-99
author_rank: Newbie
timestamp: August 22, 2015, 09:08:47 pm
content: did you open the ps4 if not send it back to sony thay want noquote author=d3l link=topic=52827.msg737111#msg737111 date=1440187369]Hey, I'm new to this forum so I just gonna go for it:I recently tried to measure the clock speed of the HDMI Signal sent from my PS4.My setup was as follows:- PS4 connected to mains voltage (with Phase and Neutral, no earth ground connection)- My Oscilloscope (MSOX3104A for reference) connected to mains voltage with all three pins connected (Phase, Neutral, Earths Ground).- The oscilloscope probe was connected to TMDS_CLOCK- (GND) and TMDS_CLOCK+ (RPOBE).- I used a cut open HDMI cable to connect the probe from the oscilloscope to the hdmi signals. (one end was plug into the PS4, the other end was floating).- Input impedance of oscilloscope was 1MOhm.To my surprise, after my measurement the PS4 was unable to send a valid HDMI signal to my TV.I tried multiple cables and a different TV and didn't get any signals.I also tried multiple PS4 resets with no effect (safe boot, hdmi signal reset).I'm really confused since I see no way I could damaged the HDMI port with my measurement.Is there something I am missing? What did I wrong?For reference, I also asked on stackoverflow but only got some strange answers:http://electronics.stackexchange.com/questions/186620/hdmi-port-damaged-with-oscilloscope(I also did ask a trained electronics engineer and he couldn't tell me what went wrong)I really appreciate any help.Thanks

author: Godzil
author_rank: Frequent Contributor
timestamp: August 22, 2015, 10:51:43 pm
content: Quote from: marshallh on August 21, 2015, 08:36:07 pmNot only that, but as this clock is a differential clock (as the - and + in the name of each pin) if the PS4 was floating (which is not the case) or the oscilloscope was (which is not the case too) probing a diff pair like that will just get not what you think

author: d3l
author_rank: Newbie
timestamp: August 23, 2015, 09:28:35 pm
content: Thanks to c4757p (and some others) I finally got a answer which satisfies me:Between the primary and secondary side of the transformer is a small cap to mainly prevent noise:By coincidence if you plug the plug in reverse, the cap is between Phase and System Ground from the PS4:By connecting the TMDS_CLOCK- output to earths ground it discharged the cap through the HDMI transmitter, most likely destroying it.Thanks for all answers, I think this topic can be closed.