[FIXED] Venerable AIM TTI PL303QMD-P needs help - Overvoltage trip error - Page 1
Forum section: electronics / repair

author: Zucca
author_rank: Unknown
timestamp: May 09, 2024, 03:39:03 am
content: Basically the master right part shows the Output trip error and become irresponsive to any button press.It is a for parts ebay purchase, the price was low and I could not resist.Still have to try to connect by ETH and see what it is going on by reading the error codes.Meanwhile I am doing my homework, if somebody knows something about this problem... I would appreciate any help.Teardown and more analysis will be here soon, stay tuned!Thanks!

author: m k
author_rank: Super Contributor
timestamp: May 12, 2024, 07:31:08 pm
content: Maybe you can gain something by swapping feedbacks.

author: ace_ventura
author_rank: Newbie
timestamp: May 13, 2024, 09:39:26 pm
content: I have the PLH version and this error means overheating. I had the same error with faulty connection to TIP31A transistor for temperature measurement located on the common heat sink.

author: Zucca
author_rank: Unknown
timestamp: May 14, 2024, 04:35:43 am
content: Thanks ace_ventura... unfortunately I have to fix my truck first then I will have time to attack the PL303QMD.Looks promising... can't wait to open it up and see.here the datasheethttps://www.st.com/resource/en/datasheet/tip31a.pdfoh I did not know that:https://www.ti.com/lit/pdf/sboa433so they are using a BJT as a temp sensor?

author: ace_ventura
author_rank: Newbie
timestamp: May 14, 2024, 05:13:58 pm
content: Yes, that's right. The fan is controlled by PWM according to the temperature sensing by BJT.You can check inside compartment of PL601 in the thread by Baliszofthttps://www.eevblog.com/forum/reviews/thurlby-thandar-not-a-happy-bunny/msg146518/#msg146518I cannot find schematic or SM for this type of power supply but I took inspiration from the TTi QL series. On KO4BB website:http://w.ko4bb.com/getsimple/index.php?id=download&file=06_Misc_Test_Equipment/Thurlby_TTi/TTi_QL_Series_Bench_Power_Supply_Service_Manual.pdfon page 44 (fan control). Output section with MOSFET is also very similar.

author: m k
author_rank: Super Contributor
timestamp: May 14, 2024, 05:41:14 pm
content: Seems to be a PL-P model.New PL & PL-P Series Instruction Manual page 4 has that there's more for PL-P models.Maybe it's in analog remote mode.Manual page 17 has Over-temperature Protection.There the message is OtP triP.

author: Zucca
author_rank: Unknown
timestamp: May 15, 2024, 03:10:33 am
content: Baby steps... I was able via Auto-IP to get this:I was hoping for something different... but I am happy the LAN seems to work!Next step finally open the puppy up...EDIT: I couldn't resit, I opened it up.Nothing obvious! There was a little of solder residual here and there....Good news the Master and Slave boards are 1:1 the same, so I have one board working and the chance to repair the other one are very high!What to do next? Swap boards and see if the errors follow the board or dig in into the schematics and make the circle smaller in the bad one?Promising!

author: Zucca
author_rank: Unknown
timestamp: May 15, 2024, 04:43:02 am
content: 00:40 in the night here... I was about to stand up from my bench when...on the master (faulty) board, WTF...

author: m k
author_rank: Super Contributor
timestamp: May 15, 2024, 07:50:34 am
content: Do some front panel button eyeballing.Can you say that faulty side is ever used?

author: Gertjan
author_rank: Frequent Contributor
timestamp: May 15, 2024, 09:03:49 am
content: Hi Zucca,I have got a TTi PL303QMD power supply too. It is my favourite Power supply. Very stable, very clean and easy to operate. Only thing I am regretting now is that I did not buy the programmable version....So your PL303QMD-P is certainly worth the effort to repair it!Shoot TTi support an e-mail. I found them friendly and helpful.In a PM I will send you the schematics I got from them.good luck & regards, Gertjan.

author: Zucca
author_rank: Unknown
timestamp: May 15, 2024, 01:15:53 pm
content: Quote from: Gertjan on May 15, 2024, 09:03:49 amGertjan, your post made me jump for joy on my bench, in my planet:Code:IF schematics THEN device_value = device_value ^ 3So the legend is real! I was aware about the very nice and friendly TTi support, who are willing to release schematics, but never needed to (well it would have been my next step...)... this is also why I pulled the trigger on that sick puppy in ebay...What a beautiful company! I will send them a message thanking them...Finally someone who understand that releasing the schematics is a good thing to do!One more reason to be proud to have ONLY AIM TTI Power Supply and DC load on my bench...Back to my problem... not sure if you spotted it from my previous post...this can't be right... wondering if this is the tragicomic culprit.PS: For everybody who helped here, if you ever come in USA, SC... free beer on me day and night!

author: Zucca
author_rank: Unknown
timestamp: May 16, 2024, 01:48:16 pm
content: Yesterday night report:1) schematics are like water in the desert!2) the misaligned molex connector above I think it is on purpose... in the aligned position there is just more filtering for VC signal.3) Both TIP31A base(=collector) in master/slave board are sitting at 0.58V4) Both master/slave fans are spinning at the same speed, did not measured it. I assume if the PIC was in thermal protection mode the fan would blow with 100% PWM. It is not the case.Tonight I will swap the power boards position and see where the error goes..I bet the problem it is not in the power board.

author: Zucca
author_rank: Unknown
timestamp: May 17, 2024, 04:12:46 am
content: Swapped power boards. Master stays in output trip.Measured FAN voltage at master power board = 5.9V, which is about 50% PWM.The power boards are fine as expected.Next step swap the control PIC boards... stay tuned the circle is getting smaller.

author: Gertjan
author_rank: Frequent Contributor
timestamp: May 17, 2024, 05:48:23 am
content: Hi Zucca,QuoteNormally, both fans are always rotating, but at very low speed (inaudible)Only when the supply is dissipating a lot of power, the fans will spin up.regards, Gertjan.

author: Zucca
author_rank: Unknown
timestamp: May 17, 2024, 01:39:07 pm
content: Quote from: Gertjan on May 17, 2024, 05:48:23 amSeems to be the case also in mine, even with output trip at the master.Both fans are spinning low, looks equal and very quietly. I measure yesterday the one at the master and it was 50%PWM... which is about reasonable as lowest point.

author: Zucca
author_rank: Unknown
timestamp: May 18, 2024, 04:33:53 am
content: Okay, the problem is in one the digital PIC board (originally master).Swapped the two and the error follows the PIC board, the other side was fixed.Two corrections from before:1) the misaligned molex (on the master power board) does not play a role... it is correct in both position misaligned or not..2) the two power boards are identical but there is a hard jumper in the master (LK1)... so for basic tests you can swap them temporarily but them put them back in place.getting closer!

author: Zucca
author_rank: Unknown
timestamp: June 20, 2024, 03:09:45 am
content: Sorry for the delay, I am selling some stuff (go to the buy/sell section to check it out) and my 2015 Ford F150 needed some immediate attention.Will resume this adventure soon, I am confident I will fix it.

author: Zucca
author_rank: Unknown
timestamp: July 02, 2024, 04:30:30 am
content: uP board has some digital and analog stuff.As a quick check the analog parts looks good.Next I will check the DAC and ADC with a scope.Can't be the uP because the display "Output trip" is sent by the uP iself.

author: Gertjan
author_rank: Frequent Contributor
timestamp: July 02, 2024, 06:01:17 am
content: Hi Zucca, good to hear that you are still at it!This very nice power supply needs to be in use on your bench, instead of sitting in your repair que

author: m k
author_rank: Super Contributor
timestamp: July 02, 2024, 01:51:09 pm
content: On the bench already.MCU can have separated on/off info pins for both channels.

author: Zucca
author_rank: Unknown
timestamp: July 04, 2024, 03:25:07 am
content: All measurement in VDCPlease confirm me something is wrong here.

author: m k
author_rank: Super Contributor
timestamp: July 04, 2024, 08:12:23 am
content: It is in balance if 2.5V has its own source.

author: Zucca
author_rank: Unknown
timestamp: July 04, 2024, 01:11:25 pm
content: sorry my bad, everything is fine there

author: Zucca
author_rank: Unknown
timestamp: July 29, 2024, 03:13:49 am
content: According to my investigation "Output trip error" meas the output is disabled because an error is detected.One error could be the over temperature, but it is unclear what are all the possible errors leading to an output trip condition.Unfortunately there are no details about these in the manual.@TTI Tech: It would be nice to have a little more info here...Example, if I use my other PL303 as DC load (with a small current just for testing purposes), I can reproduce the output trip error condition that can be cleared once I disconnect the inputs and press the output button.That said back to my unit.....somewhere in this control board there is a problem.Some tips for future repairs:1) The left leg (see blue circle) of the big "Mexico" R79 is GND2) There are many SMD fuses (very robust design) to check "FBxx" (see yellow circle as example)To the best of my knowledge all the analog input and output sections are working properly.Since the uP goes in output trip error immediately after power up, it is detecting something is off and the output are turned off.By pressing the output button there are no changes in the output analog sections, which tells me the problem is not a consequence of a bad output state but something is the inputs independently from the output state.Some of those inputs are processed directly by the ADCs in the uP PIC (like the over temperature analog signal) and some go through the IC7 ADS1241 ADC.The display shows OPT Trip so I tend to assume the uP PIC is good. So if I have to bet, the IC7 ADS1241 is the bad guy.I could just take and install the known good IC7 ADS1241 front the other control board, but first I want to be more sure about my theory.The next days I will try to dig into the digital signals I2C, clocks and so on....I will now also contact the awesome TTI support and see what they say.PS: There are also the programming pins for the uP available (PJ6), does it make sense to connect a PICKIT to diagnose the problem? Sorry for the idiot question I have not played with PIC uP too much.....

author: Zucca
author_rank: Unknown
timestamp: July 29, 2024, 04:14:45 pm
content: Aim TTI support already responded, these guys are awesome!Plot twist: the display OUP tRiP means OVP Trip, overvoltage protection!I am embarassed now, I did not noticed thatOtP tRiP(mentioned in the manual) !=OUP tRiPmore to come...

author: m k
author_rank: Super Contributor
timestamp: July 29, 2024, 05:46:22 pm
content: Dang, too late.My guess was that OUP is too wide as output.In case you have enough courage you can try creating an OCP trip using the functioning side of the machine.The feedback can be on/off style controller pins or analog inputs and then controller decides what is bad.Older version has ILIMIT as a single pin, but can't say what it actually is.Triple model 5V has OVP trip signal, others have OPON.Swapping boards and using brute force measuring tactics you can "easily" narrow possible problem pins.But schematics would be better.For PJ6 my guess is that it doesn't help.But who knows, maybe it's constantly outputting some console info.

author: Zucca
author_rank: Unknown
timestamp: August 02, 2024, 03:09:41 am
content: Thank m k to stay with me in this madness.After some emails, TTi support told me they believe/think the uP must be defective and that's it, they did not respond to my last email.... I let them go in peace...They helped me a lot for free!Despite that I think we have still cards to play, now that we know that it's an OVP problem we can dig into the right direction.Please be aware, if you see a OVP malfunction in your device, I would say 90% the bad guy is the power board, my case is an unicorn IMHO.According to my rev eng, there are 2 places where the output voltage (aka vsense+ and vsense-) comes into the control board:1 - into the ADC2 - into the VC generation analog part, basically to close the output voltage regulation feedback loop:Vset ----> Vc --> Output ----| |--------------------------- Vc is the control voltage- Vset is the target voltage coming from the uPPlease note the Vset to Vc analog part is on the control board, the Vc to Output is on the power board.Now, two facts:a) I can't find any problem in the analog control board  partb) after powering up the unit, immediately the OVP is triggered on the side (master or slave does not matter) where the offending control board is installed.Here below the startup sequence on the offending sideGreen is the 5V railBlue is VcYellow is Vsetthis means to me:1) Assuming the uP is still alive since I see "OUP tRIP" in the display, we need to check what it is going on between Vsenses lines before and after the ADC.2) I need to compare the same startup sequence on the good side with output off, to see if Vc going to the roof for about 85ms after startup is normal.I think this is not a problem... Vset stay at zero.... so...[oh I did not check if the output is spiking at startup as well... but since Vset is 0 all the time, I do not expect any movement there.]Before the ADC this is what is happening:where A17 and A16 are the two ADC inputs, simulated in QSpice we get:it's too late now, I need to sleep.... more to come.

author: m k
author_rank: Super Contributor
timestamp: August 02, 2024, 01:18:24 pm
content: Chopped startup of PID controller.First D goes through the roof, then 'I' start kicking in and finally everything is steady again.Maybe this startup shouldn't go through the feedback.

author: Zucca
author_rank: Unknown
timestamp: August 07, 2024, 03:50:47 am
content: Back to the ADC section, this is the correct output sense circuit. The previous one is not good.basically the Vsense+ is connected to GND (when sense is set to local of course).And this is the output voltages to the ADC (sweep 0V to 35V output voltage):And this make sense, because the ADC input range is 0V-2.5V, in my previous one input was above 2.5V so it would had not work well.In my previous measurements, I confirmed those ADC inputs lines are sitting at 2.4V when the outputs are disabled, which again matches the simulation.

author: Zucca
author_rank: Unknown
timestamp: August 09, 2024, 03:58:49 am
content: Startup voltages, yellow output, green 5V railsince the output doesn't move, again either the ADC or the uP (unlikely) are bad.Next step sniff the ADC SPI

author: m k
author_rank: Super Contributor
timestamp: August 09, 2024, 03:38:21 pm
content: The chip has 8 inputs, have you tried comparing them?It probably has the same stuff for left and right.It's also possible that OVP is the first message and so misleading.Means that only if there's no OVP other messages are appearing.A bit far fetched, surely stuff like missing ADC is messaged before it.

author: Zucca
author_rank: Unknown
timestamp: August 11, 2024, 04:19:48 am
content: Well I did not compare the good/bad side ADC inputs because the ADC inputs on the bad side make sense coming from the Sense lines...More over I dig into the analog part and I coudn't find any error.Tonight I compared at the SPIs good ADC and bad ADC, no major differences just looking at the signals/edge... still have to decode the traffic.One more interesting find, if I swap the control boards again, the good one (was slave) at the master place report a FAIL 4 and won't turn on the output.Once I reverted it, the error disappears and at least one side (slave) is working as expected.Did not see a fail 4 on the bad one at the wrong place (master in slave)... mmmm hope the uP is not toasted.

author: m k
author_rank: Super Contributor
timestamp: August 11, 2024, 05:47:02 am
content: Maybe you got a bad connection.I don't like those IDC style connectors, too many times pin coatings are sub-standard.And ribbon cable side knife connection is what ever after few twists.Are there many possible serial bus connections out from MCU?Maybe you can map most of them and find out how the thing is initialized.

author: Zucca
author_rank: Unknown
timestamp: August 12, 2024, 01:26:13 am
content: thx m k, I am too tired to work on it tonight.Here the startup video,https://www.dropbox.com/scl/fi/1rs3myawu33dif7xj68vr/20240811_205119.mp4?rlkey=wenaqjdetib6d5u4kn7ly6tae&st=wsuwg4s9&dl=0uP is booting, then goes in error mode ovp immediately.

author: Zucca
author_rank: Unknown
timestamp: August 13, 2024, 03:21:19 am
content: SPI madness...Now I just have to do some homework...FUUUU I was not expecting such a hard job, it is just a damm power supply!

author: m k
author_rank: Super Contributor
timestamp: August 13, 2024, 06:30:43 pm
content: Dang, I though it has only one MCU.Well, then you just compare 8 ADC inputs to other 8 ADC inputs.Very simple.

author: m k
author_rank: Super Contributor
timestamp: August 14, 2024, 04:27:50 pm
content: ADS1241 high nibble of opcode can be only 0, 1, 5 or F.So 5 (1+4) bytes is fine, but 48 or 40 can't be any opcode.3 times the same set indicates it's close.And 1st byte is recognized as an opcode, or is it.Answer could be one from negative limit of 24bit signed value, if MSB is right.But then opcode must be 1.4 8 40100 1000 0100 0000 0000 0000 0000 0000 0000 0000MSB still right and shifting 2 bits would be xx 01.But then 1st byte doesn't fit.E,obviously not -2.E2,boot has 8 frames of right CC LED, later left CC LED on is a bit shorter.May that CC LED can be a trigger for checking the fault test moment.

author: Zucca
author_rank: Unknown
timestamp: August 15, 2024, 05:04:57 am
content: Thanks m K! So coolI will dig into it the next days... I hope there are no noise that are causing some bit flipping... I have also a Picoscope that for decoding SPI maybe it is better...Crucial will be the startup phase... what I posted above was just a proof dirty try/proof of concept...Tonight I compared the good and bad ADC inputs regarding the Vsense lines (the one causing the OVP)Good onePIN16 Vsense- 2.402V15 Vsense+ 2.402V9 REF+ 2.510VBad onePIN16 Vsense- 2.402V15 Vsense+ 2.402V9 REF+ 2.511Vas expected the analog part works and matchs my Spice sim.

author: m k
author_rank: Super Contributor
timestamp: August 15, 2024, 08:58:53 am
content: Was your measuring GND far away?Maybe the chip has some problems with it.If those boot LEDs are what they are marked to be it's like master side has equally bad voltage and current.When booting two slave side LEDs come on together, but master side has a delay.Delay can mean that boot is waiting that tested voltage is settling down, that never happens, and then does the same wait for current.

author: Zucca
author_rank: Unknown
timestamp: August 27, 2024, 01:20:43 pm
content: Quote from: m k on August 14, 2024, 04:27:50 pmm k is right!I had a wrong MSB/LSB setting in the previous screenshots.Let me dig a little bit further and I will report my findings soon!Thanks again m k!

author: Zucca
author_rank: Unknown
timestamp: August 28, 2024, 03:00:59 am
content: Here we go... here what I could sniff on the SPI on the GOOD working board:Sent:12 02 00 00 00Received:00 00 80 00 01the above repeats a lotSporadically I getSent:51 00 38OR Sent:51 00 58Sent:51 00 48OR Sent:51 00 28always Received:FF FF FFfollowed bySent:01 FF FF FF FFhere I get multiple possible responsesReceived A:FF 00 00 25Received B:00 00 15 C1and so on, attached the sniffed traffic in .csv files.Now dive into the ADC IC07 ADS1241 datasheet to understand what it is going on.cool.

author: m k
author_rank: Super Contributor
timestamp: August 28, 2024, 04:49:46 am
content: 02 after 12 is a counter, same with 00 after 51.FF can be a waiting thingy, but after 01 (read data) should be only 24 bits.So last received is a byte too long, maybe it's just a hiccup.

author: Zucca
author_rank: Unknown
timestamp: August 29, 2024, 03:37:11 am
content: sniffed the SPI from the bad uC board...There are a lot more FF FF spitted out from the ADC to the uC.Since I measured the inputs, and they are okay... I think the next reasonable step is to swap the two ADCs from the two good/bad board and see what happens.Such a unicorn failure...PS: the Picoscope for decoding serial is such a champion.

author: Zucca
author_rank: Unknown
timestamp: August 29, 2024, 04:40:40 pm
content: New ADS1241E/1K‎ ordered, finger crossed.

author: m k
author_rank: Super Contributor
timestamp: August 29, 2024, 06:54:15 pm
content: So single ended input channel 3 and differential 6-7 are open or pulled up.Channel 5 is sending 32 bits, maybe nothing, but it's also positive once.Did you check those inputs with a scope?But anyway, ADC change is pretty affirmative thing.

author: Zucca
author_rank: Unknown
timestamp: September 04, 2024, 03:23:06 am
content: DISCLAIMER: I never reworked a SSOP28.I did it without microscope.... long story.... you don't wanna know...Here the awful result: not centered at all.I did cleaned the pads, eyeballed the chip and soldered it downNext time I will presolder the pads and then let the hot air do its magic.Yes I used tacky flux, no worries.Then I give it a shot andFUUUU YES! No more OVP Trip!Now I have to fully test my repaired PL303QMD.Finally I just want to thankm kandGertjanfor helping me in this madness.PS: C18, C17 and C15 will be installed once I am sure that ADS1241 is installed correctly..More to come! FW Upgrade? Calibration? yummm...

author: mk_
author_rank: Regular Contributor
timestamp: September 04, 2024, 05:27:12 am
content: Quote from: Zucca on September 04, 2024, 03:23:06 amWell done... and who cares about not perfect alligned pads as long as they don`t short to others? The lid hides those little lapsi

author: ArdWar
author_rank: Frequent Contributor
timestamp: September 04, 2024, 05:44:28 am
content: No bridges, no overhanging pins, no one notices if not for the shiny lead.

author: Gertjan
author_rank: Frequent Contributor
timestamp: September 04, 2024, 07:32:05 am
content: Hi Zucca,Well done!Congratulations with a well deserved successful repair! You did the extra mile, and it paid off.QuoteI would not do that. Hot air is splendid for small SMD IC packages, like TQFN. You heat the whole package, and it will float in place when all solder has melted.In my experience with a (relative) larger package, like this ADS1241, it is best to solder it just like you did:- Clean the pads- Add some flux- Position the new IC, and solder two opposite corner pads.(After tacking the first corner pad, check position of the IC, and adjust if necessary, then solder opposite corner pad)- The IC is now held in place, solder the rest of the pads.This is how I do it without much problems. Only difference is that I use a microscope.(But your handy-work does not look too shabby too...)Lastly, do not tinker too much with your PL303QMD. Just use it, and start to enjoy and appreciate it!regards, Gertjan.

author: m k
author_rank: Super Contributor
timestamp: September 04, 2024, 10:00:20 am
content: Quote from: Zucca on September 04, 2024, 03:23:06 amIt's a camera effect, see C19.If you ever start having intermittent issues, check through holes.Factory tin is thin.

author: Zucca
author_rank: Unknown
timestamp: September 09, 2024, 01:21:56 am
content: ok I fully tested it. Not a single problem to report, I am a happy camper!What a nice device, definitely my first choice as my daily work horse!Upgraded to last FW went well, and no need for calibration it was bang on.I report here below what AIM TTi support told me to do as sanity checks as first step:QuoteWhat killed the ADC? My guess is an ESD zap from the outputs.

author: m k
author_rank: Super Contributor
timestamp: September 09, 2024, 10:22:22 am
content: Are all fuses original?Maybe it saw a glimpse of mains.

author: Zucca
author_rank: Unknown
timestamp: September 09, 2024, 01:19:04 pm
content: all fuses original, at least the ones on the boards. the glass mains ones don't know.

author: nomead
author_rank: Contributor
timestamp: September 09, 2024, 02:36:30 pm
content: Quote from: Zucca on September 09, 2024, 01:21:56 amI am kind of amazed by that kind of openness and helpful attitude. Are they fighting the planned obsolescence, eastern imports or both?

author: Zucca
author_rank: Unknown
timestamp: September 09, 2024, 03:21:17 pm
content: Quote from: nomead on September 09, 2024, 02:36:30 pmIf you designed a product and sold it, you should be responsible to provide all the support your customers need.It simply should not matter how old the device is or from where the competitors are...Unfortunately in 2024, bad customer support is so common that the few good ones are seen as "strange" or "suspicious"I know AIM TTi is reading this, so please continue with your awesome good customer support.I will continue to buy stuff from you, support youand make sure others understand why.