Test Equipment Anonymous (TEA) group therapy thread

[mansaxel]

And I'll bet the whole freaking stack smells of mildew. 

Most scanners lack smell sense.

Now introducing the SuperFlat 2000, with smell-o-scan!

[Neomys Sapiens]

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.
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mnem
I bet the manual for my HP 54654A Oscilloscope Training Kit is in there somewhere...

I was thinking exactly the same thing about my un- or mis-documented HP devices!

[Saskia]

The Truth is in there !

sorry, could not resist ...

[Neper]

And I'll bet the whole freaking stack smells of mildew. 

My nose is running from just looking at the photo.

[Specmaster]

I bet there a few mouse nests in there as well 

[Cerebus]

On the basis of "you are what you eat" that's how you end up with super-intelligent mice who plot to take over the world.

[Neper]

Haven't they already? 42 and all that?

[Ice-Tea]

Hey Guys 'n Gals,

Haven't been around for a bit, probably won't change in the near future but I could do with a consult... Or maybe I'll figure it out while typing. Wouldn't be the first time.

I have a number of Fluke 199C's. Very nice machines, but they always come with dead batteries. The army had them, still can't believe they couldn't be arsed to charge the battery from time to time. For the rest, most work, some don't. I have always expected the charging/power circuit to be dud on the bad ones but never got around to inventory them. Too little time, again...

Put new batteries in the ones I sold already. Roughly same capacity, measured pins, seems to check out, also measured about 10k or so so I guess the NTC is there too. Need to do a heatup test for that to see if it actually an NTC, but I doubt there's an issue there, fairly reputable source...

Anyhow, little while ago, had a customer that was rather distrought half a year after purchase because his unit died. Wasn't happy with that, offered him to exchange it for another with a minor service fee (even though the eBay return warranty lapsed obviously), but he didn't even reply. Didn't think much of it at the time...

Sold another one last week, so I put in a new battery and with the unit still open started charging it. The adapters are UK style so I took a plug and hooked it up to a Rigol DP832. Was charging fine, at some point I was happy with how much was in the battery and turned of the power supply.

R4101 blew up pretty much instantly.

https://ibb.co/bNmny41



Again, didn't think all that much about it. Figured I fumbled a wire, had some jumper wires hooked up to monitor with a 34401, made made a short or something... You know, always suspect the biggest idiot in the room, usualy the best bet. So, had another one nearby, thought, just to make sure, start with the original, pretty dead battery, at least it's 100% sure compatible. These things have a battery recycling option so I hit that.

R4101: from glow to blow in about 2 seconds.

At this point, I obviously start to doubt everything. The dead units I have? May well have blown when I turned them on. Have I been sending out crap units? And more importantly: WTF?? So I started looking at the schematic. R4101 is a 2010 0.15 resisor. For it to blow up that fast it must have been pulling, what, 3A? I could obviously take another unit out of storage and start probing around but, well, I can't really support blowing up 199c's at a pace of more than one a day. So, if any of you had some ideas: shoot. I just don't get it. Could it be because I'm using a bench PSU? Can't really see how. Had it on current limited mode (less than an amp, how is *that* supposed to blow that resistor... Happened with two types of batteries, hard to see how the ersatz battery is to blame. If it blows *both* with an original dead battery and a non-compatible new one, it's still a piss poor design.

Figured it might be the battery back-powering the turned off bench PSU. But there's diodes. Figured it might be that with the bench psu voltage decaying, the Fluke's battery charger IC goes into a bad mode and just lets it rip, but I don't see how that would happen: the battery voltage is high enough to avoid that.

Fact is I just can't come up with a mode that would lead to 3A being dumped through the battery unless the charging circuitry has some readlly bad design flaws. Can't imagine Fluke would have let that go out the door, can't imagine it not being a widely known and discussed fact. So, before I start risking more units, I'd like to undertand...

Lend a guy a hand, will ya?

[Ice-Tea]

Service manual:

https://elektrotanya.com/fluke_192b_196b-c_199b-c_scopemeter.pdf/download.html

[ch_scr]

Hey Guys 'n Gals,
[...] Fluke 199C's. Very nice machines, [...] started charging it. [...] Was charging fine, at some point I was happy with how much was in the battery and turned of the power supply.

R4101 blew up pretty much instantly.

[...] New Unit,  start with the original, pretty dead battery, at least it's 100% sure compatible. These things have a battery recycling option so I hit that.

R4101: from glow to blow in about 2 seconds.

At this point, I obviously start to doubt everything. The dead units I have? May well have blown when I turned them on. Have I been sending out crap units? And more importantly: WTF?? So I started looking at the schematic. R4101 is a 2010 0.15 resistor. For it to blow up that fast it must have been pulling, what, 3A?

To me it seems the likely current path has to be from the batteries. It seems to me the resistors blow when the units power supply starts taking current from them, which fits a switch over to bat power after charge and maybe a bat refresh that starts with a discharge to afterwards charge from empty?
And yes, to blow a 1210 like that would normally take a lot of power - it seems unlikely to me as well.
I also think a general problem would be known. Question is: with units of a shared past, might they have a common denominator of environmental influence (I think along the lines of e.g. corrosive gas) that might have weakend some of the resistors?
I've seen what ammonia from farm biogas reactors does to copper bus bars, and we had early death of resistors in S7-200 automation controllers used there - only one type of resistor failed, a tiny smd 4 resistor network used for led current limiting. Given the use and size I would say it had a high current density per area of resistive element.
On precision resistors smd datasheets some talk about advanced protection against corrosive gas.
Real questions based on that assumption: is the unit ok with just a new resistor?
Can you check the resistor value on one or more unblown units?
To test one also could set up a second power supply (with sink capability) [as a battery simulation] with external sense resistor and a scope to see transient currents and check if it really takes a gulp - if it does, new theory needed then - but I would suspect something in the power supply afterwards taking lot of current?

[25 CPS]

ROCK THE WORKBENCH!

It took some equipment rearrangement and some moving the power distribution around to fit it in but I’ve corrected this long standing problem of music being at the wrong end of the workbench:

The two 3310A’s used to be stacked where that speaker is so I kicked them on top of the 3325A to make space there and the counter and spectrum analyzer got shifted a bit left along with a Tektronix TDS 640 that’s out of frame to the left to make space at the other end.

I’m still experimenting with speaker orientation but I’m leaning towards upside down sounding a little bit better with the tweeters at pretty much exactly ear height instead of a bit above.


I've got some Simple Minds playing while dinner cooks.  Next up:

Oh well, at least it wasn't "The Smiths". 

But seriously, I'd be concerned about vibration. There's many a precision circuit that I'd want to keep a million miles away from any accidental, let alone deliberate, source of vibration.

That thought had crossed my mind and I gave it some thought along with the closeness of CRTs to the speakers.  I was able to shift that spectrum analyzer far enough away that it wasn’t affected by B&W’s magnetic field.  Vibration is going to be a bit more tricky in terms of mechanical isolation.  What I’m most likely to do is find spots for a pair of floor standing speakers and move the bookshelf pair off the bench into the other room in the basement and run them off the received’s B outputs.

[mnementh]

On the basis of "you are what you eat" that's how you end up with super-intelligent mice who plot to take over the world.   

               BWAHAHAHA!!!

Ohhh... hell. Thanks for the belly laugh. This whole afternoon has been trying to get stuff moved with my teenager whinge-assing and giving me grief like a total drama llama every fucking minute... I swear, he might not get to see his birthday next week.   

mnem
Pinky, are you contemplating what I'm contemplating...?
I think so Brain; but this time you put the rubber pants on the chimpanzee; the last one bit me so...   

[Vince]

I need your help people... lots of you are into audio stuff so I am hoping one of you will know the answer.

I have just been given a car stereo for repair. First circle of friend and he is not a time waster and first time he ever asks me to fix anything... so I agreed to " have a look " at his piece of junk. It a double DIN / height modern thing that does everything and anything, with a big LCD screen, can display video from front or rear camera on the vehicle, TV, wireless or wired, USB, all sorts of I/O. It's less than a year old, still under warranty but the seller apparently is so great that he won't take responsibility for it. Only matched by the quality of the unit itself : 100% chinesium, the worse kind : there isn't even a BRAND name or model written on it, nada ! You just don't know what it is, nor who made it. Only thing you have is a sticker with a wiring diagram/ pinout for the very many connectors this thing carries at the back !!!! 

Owner said the problem is taht the screen is dead, black, no picture no matter what.. BUT that the unit still powers up and that if he blindly plays with the knobs, unit seem to operate normally and he can listen to radio and what not. So I thought OK looks like it's just a dead display, might be worth having a look at it, especially since unit is so new and cost so much money, 300 Euros... a fortune for chinese crap that's not even branded/identified !   

So I have this thing on the bench, actually very service friendly can't complain. Easy to split and the mother board is perfectly accessible with all the components on the top side, great. Front panel assembly show you the component side of the LCD board, where I can see the connector tghat goes to the backlight, and the board carries a couple SMPS. So I can easily test the backlight and make sure the SMSP work as well.

So I give the unit power and ground... press the pwoer button but... it does not wake up ! And the ammeter shows that the unit draws 0.000mA, not a mA ! Weird....

So I am here to ask those in the know here, who are used to wiring modern car stereo... is there some other input I need to wire up other than ground and battery / +12V, the twxo beefy wires, to get the thing to power up ??   I see the unit is connected to the freaking CAN Bus of the car ! 
There is an external little box supplied with the stereo, that reads " CAN Bus decoder ". Whatever that does. I plugged it in, but no joy either.

Could a problem with the can bus, or lack there of, prevent the unit from powering up ? Do I really need to have CAN working to xwake up the stereo ? That means I can't debug the unit on my work bench then ?! 

Also there are other inputs whose name sounds mysterious, maybe they need to be wired as well, I don't know. See close up picture of the pinout diagtram below :

(1)  Steering Wheel KEY 1
(2)  Steering Wheel KEY 2
(11) CAN BUS TXD
(12) CAN BUS RXD
(14) BRAKE.  I guess it means brake pedal...
(17) ILL ...like in "Illumination" / backlight ? I see that this wire goes straight to the external can bus decoder box...
(18) ACC ... accelerator ? They monitor the brake pedal so why not the Accelerator pedal
(19) ANT .... "Antenna" I guess ? Power feed to extend a telescopic antenna ? Or power a roof mounted amplified antenna ?
(20) REVERSE :  I guess it means reverse GEAR, probably used to automatically switch to the rear view camera video feed...

Pedals, antenna, reverse gear, I guess I can safely ignore.

However ACC not sure, ILL not sure either, CAN bus I am scared, and steering wheel KEY 1 and 2 scared too...

Please help poor Vince, how the fuck can I wire this thing on my bench to get it to power up and draw some current ! If AT ALL possible ?! 

[xrunner]

  I see the unit is connected to the freaking CAN Bus of the car ! 
There is an external little box supplied with the stereo, that reads " CAN Bus decoder ". Whatever that does. I plugged it in, but no joy either.

Could a problem with the can bus, or lack there of, prevent the unit from powering up ? Do I really need to have CAN working to xwake up the stereo ? That means I can't debug the unit on my work bench then ?! 

I've heard that yes it needs the Master Compute Box to work, but let's see what others have to say ...

Yea amazing no brand name, what kind of world are we living in. 

[mnementh]

Apply (+12V) to the ACC (vehicle Accessory) wire. Modern car audio has a large, heavy B+ for the amplifiers and turn themselves on/off with the ignition switch rather than killing main power to the unit.

mnem
 

[tautech]

Apply (+12V) to the ACC (vehicle Accessory) wire. Modern car audio has a large, heavy B+ for the amplifiers and turn themselves on/off with the ignition switch rather than killing main power to the unit.

mnem
 

This ! ^^^
mnem beat me to it. 

[mnementh]

  I see the unit is connected to the freaking CAN Bus of the car ! 
There is an external little box supplied with the stereo, that reads " CAN Bus decoder ". Whatever that does. I plugged it in, but no joy either.

Could a problem with the can bus, or lack there of, prevent the unit from powering up ? Do I really need to have CAN working to xwake up the stereo ? That means I can't debug the unit on my work bench then ?! 

I've heard that yes it needs the Master Compute Box to work, but let's see what others have to say ...

If it is an aftermarket stereo, then no, it doesn't NEED the CAN bus to operate as a stereo; that is probably for either antitheft or CarPuter integration. Some units are custom made to integrate into the factory radio's amplifiers and mimic the factory radio so that the car doesn't think it's being molested, but those too should not need to be connected to the body computer/antitheft module to at least light up; they will in fact usually light up and whinge aboot not being connected, so also good for Vince in this case.

EDIT: As it is a low mileage unit, my first guess would be a ribbon cable either broken or unplugged between the LCD and the unit, especially if said LCD is mounted in a motorized sled. I would also look for PCB edge-connectors dislodged or partially unplugged in either the main uint or the LCD module; modern car audio is built like a fucking Tetris stack all connected with those horrible things.

mnem
 

[mnementh]

Oh, wait... I see the pix now. 

Yeah, this is one of the Chineseum Android car stereos that have been all over Amazon and fleaBay for the last few years. They don't have the brand name on the unit, as they're batch made for an importer/exporter to slap in a box with their own name on it. They also repackage these with custom bezels as custom-fit for the integrated-dashboard factory radios like in my Rav4.

First thing I'd do is check every ribbon cable for continuity, and look for FETs & voltage regulator ICs that might have let loose their magic smoke. Some of these will be in SOT-23 package; don't overlook any component. Also, look all over the main PCB and the LCD module for anything that indicates a voltage, and check for that voltage present.

If you do a google for "Android Car Stereo" or "Double DIN Android Stereo" you should be able to identify the one you have by pictures.

mnem
 

[Wolfgang]

Anyone with access to a N8974A, N8975A or compatible noise figure analyzer? Would like to test something, quite willing to pay...

What do you need exactly ?

[Vince]

Thanks for all the good info ! 

1) I wired +12V to the ACC wire. That meant I had to unplug the CAN bus box because the ACC wire goes straight to that box !
Result = no change, still no power, still does not draw even ONE mA... nothing at all.

2) Visual inspection leads nothing, damaged components or dislodged flat flex cables.

3) Probed main board for voltages... checked all electrolytic caps, all "SMPS" looking SMD coils, and all discrete components, diodes and what not, in the immediate vicinity of the main/power connector at the back of the unit. ZERO voltage everywhere. If the screen/front panel was at fault, the mainboard would still be running so I would be able to see supply VOLTAGES and theunit would draw at least SOME current ! But it draws absolutely zero, and zero voltage anywhere. So there is no point worrying about the display or flat flew cables at this point I think ! 

4) REGARDLESS of whatever magic the unit might perform to "decode" its numerous inputs, to decide if it will be so kind as to power up the unit... this smartness is embodied by circuitry, a CPU, or a dedicated power management chip or discrete circuitry or SOMETHING.... this means that even if the conditions for the unit to power up were not satisfied, the smarts inside the unit would be powered up anyway and therefore draw some current and need voltage to run.... but since I can't even witness the slightest current draw... it means the main board is just not "upset" with the way I wired it... it's more like it's simply not powered up AT ALL !

So I am now shifting from a "No display" fault, to a "No Power" fault.... not at all the same thing...

Zerto votlage and zero current... it's just like the main fuse was blown, as simple as that ! Yeah, I did check the fuse... it's fine...

Next step is to unscrew the main board from the chassis, so I can inspect the underside of it, and access the pins of the power connector. I will trace the +12V pin to see where it lands on the top/component side, then trace it there.

But it's too late now, going to bed.  Before I waste time on this thing, I will the owner who actually lives just 500m from me, so he can come with his car. I will ask that we  reconnect the stereo to his car, so he can show me if he really can get this thing to work.... as a quick sanity check. If it does power up and work, then I don't understand how that's possible 

More tomorrow then, good night ! 

[Brumby]

First things first...
BATT = Battery: Continuous 12V power - required to keep memory alive for various settings
ACC = Accessory:  Switched 12V - Power supplied when you turn the ignition key to the Accessory or On position.  This restricts use of the unit when the ignition key of the car is in use.  You can defeat this "protection" by wiring it directly to constant 12V - which is what you would do for testing.  (In a car, you just might flatten the battery if you do this and leave it turned on for a time.)
GND = Ground or chassis.  The negative - or 0V - side of the power source.
Snap!

First thing I'd do is ......

The first thing I'd do - before even opening anything up - is wire up the GND, BATT and ACC connections and turn it on.  Hmmm.... no current is not a good start to this exercise... Get a nice strong light and shine it into the screen at an angle from the side and look closely to see if you can make out an image on the screen.  If there is something there, then I'd be looking at the backlight having failed.

If nothing observed, then get intrusive.

Adding an antenna and a couple of speakers (and/or other inputs) might also be good step to assist in diagnosis.

[mnementh]

Hey Guys 'n Gals,
[...] Fluke 199C's. Very nice machines, [...] started charging it. [...] Was charging fine, at some point I was happy with how much was in the battery and turned of the power supply.

R4101 blew up pretty much instantly.

[...] New Unit,  start with the original, pretty dead battery, at least it's 100% sure compatible. These things have a battery recycling option so I hit that.

R4101: from glow to blow in about 2 seconds.

At this point, I obviously start to doubt everything. The dead units I have? May well have blown when I turned them on. Have I been sending out crap units? And more importantly: WTF?? So I started looking at the schematic. R4101 is a 2010 0.15 resistor. For it to blow up that fast it must have been pulling, what, 3A?

To me it seems the likely current path has to be from the batteries. It seems to me the resistors blow when the units power supply starts taking current from them, which fits a switch over to bat power after charge and maybe a bat refresh that starts with a discharge to afterwards charge from empty?
And yes, to blow a 1210 like that would normally take a lot of power - it seems unlikely to me as well.
I also think a general problem would be known. Question is: with units of a shared past, might they have a common denominator of environmental influence (I think along the lines of e.g. corrosive gas) that might have weakend some of the resistors?
I've seen what ammonia from farm biogas reactors does to copper bus bars, and we had early death of resistors in S7-200 automation controllers used there - only one type of resistor failed, a tiny smd 4 resistor network used for led current limiting. Given the use and size I would say it had a high current density per area of resistive element.
On precision resistors smd datasheets some talk about advanced protection against corrosive gas.
Real questions based on that assumption: is the unit ok with just a new resistor?
Can you check the resistor value on one or more unblown units?
To test one also could set up a second power supply (with sink capability) [as a battery simulation] with external sense resistor and a scope to see transient currents and check if it really takes a gulp - if it does, new theory needed then - but I would suspect something in the power supply afterwards taking lot of current?

Smells to me like the batteries are trying to charge a large capacitor bank; maybe some weird interaction between that particular bench PSU and that particular BMS in the Fluke. Could be you PSU is using a FET-based crowbar that is allowing some feedback.

I would replace the resistor in the 2nd unit with OEM battery, then try again with a small fuse and diode inline in your charge cable and see if it continues to misbehave. Alternately, look for a proper wall-wart for one of these and see if it does in fact play well with the aftermarket battery. If so, your customer may have been at fault for using a wrong power source.

mnem
 

[Specmaster]

Thanks for all the good info ! 

1) I wired +12V to the ACC wire. That meant I had to unplug the CAN bus box because the ACC wire goes straight to that box !
Result = no change, still no power, still does not draw even ONE mA... nothing at all.

2) Visual inspection leads nothing, damaged components or dislodged flat flex cables.

3) Probed main board for voltages... checked all electrolytic caps, all "SMPS" looking SMD coils, and all discrete components, diodes and what not, in the immediate vicinity of the main/power connector at the back of the unit. ZERO voltage everywhere. If the screen/front panel was at fault, the mainboard would still be running so I would be able to see supply VOLTAGES and theunit would draw at least SOME current ! But it draws absolutely zero, and zero voltage anywhere. So there is no point worrying about the display or flat flew cables at this point I think ! 

4) REGARDLESS of whatever magic the unit might perform to "decode" its numerous inputs, to decide if it will be so kind as to power up the unit... this smartness is embodied by circuitry, a CPU, or a dedicated power management chip or discrete circuitry or SOMETHING.... this means that even if the conditions for the unit to power up were not satisfied, the smarts inside the unit would be powered up anyway and therefore draw some current and need voltage to run.... but since I can't even witness the slightest current draw... it means the main board is just not "upset" with the way I wired it... it's more like it's simply not powered up AT ALL !

So I am now shifting from a "No display" fault, to a "No Power" fault.... not at all the same thing...

Zerto votlage and zero current... it's just like the main fuse was blown, as simple as that ! Yeah, I did check the fuse... it's fine...

Next step is to unscrew the main board from the chassis, so I can inspect the underside of it, and access the pins of the power connector. I will trace the +12V pin to see where it lands on the top/component side, then trace it there.

But it's too late now, going to bed.  Before I waste time on this thing, I will the owner who actually lives just 500m from me, so he can come with his car. I will ask that we  reconnect the stereo to his car, so he can show me if he really can get this thing to work.... as a quick sanity check. If it does power up and work, then I don't understand how that's possible 

More tomorrow then, good night ! 

I respect what mnem has to say, but personally I'm not so sure about not needing the Can Bus to be functioning. Everything on my car is completely controlled by dozens of ECU's, all internected via Can Bus and all switches etc are hooked into the Can Bus so that in the event of someone leaving the radio or some other gadget, light etc switched on when leaving the car, the system can detect this and switch it off to preserve the battery. I think a little more detective work might be in order to double check if the Can Bus has to be connected first in the first instance to provide the ability to power it on via the on/off switch. Another thing that you are likely to require is the security code for the radio as once the battery is disconnected the anti-theft system is also likely to have kicked into play and may have to reset the system in order to power it on again.

[mnementh]

First things first...
BATT = Battery: Continuous 12V power - required to keep memory alive for various settings
ACC = Accessory:  Switched 12V - Power supplied when you turn the ignition key to the Accessory or On position.  This restricts use of the unit when the ignition key of the car is in use.  You can defeat this "protection" by wiring it directly to constant 12V - which is what you would do for testing.  (In a car, you just might flatten the battery if you do this and leave it turned on for a time.)
GND = Ground or chassis.  The negative - or 0V - side of the power source.
Snap!

First thing I'd do is ......

The first thing I'd do - before even opening anything up - is wire up the GND, BATT and ACC connections and turn it on.  Hmmm.... no current is not a good start to this exercise... Get a nice strong light and shine it into the screen at an angle from the side and look closely to see if you can make out an image on the screen.  If there is something there, then I'd be looking at the backlight having failed.

If nothing observed, then get intrusive.

Adding an antenna and a couple of speakers (and/or other inputs) might also be good step to assist in diagnosis.

Umm.... yeah, we're already well beyond that stage at this point; if you look at the pics he already has the thing gutted like a fish. Also, evidently you completely missed where I already explained the power system in the post directly above that one. We are long past the days of having main power switched from the ignition and a battery backup for station memory/clock; main power is drawn straight from the battery (or as close as you can get) and the ACC wire just lets the radio know it's time to turn itself ON/OFF.

As it's a low-mileage unit approx a year old, I'm still betting on a cable unplugged/broken somewhere. It's old enough to be a fringe datapoint on the bell curve for infant mortality, not old enough to likely be worn-out LEDs or ballast circuit.

mnem
 

[mnementh]

Thanks for all the good info ! 

1) I wired +12V to the ACC wire. That meant I had to unplug the CAN bus box because the ACC wire goes straight to that box !
Result = no change, still no power, still does not draw even ONE mA... nothing at all.

2) Visual inspection leads nothing, damaged components or dislodged flat flex cables.

3) Probed main board for voltages... checked all electrolytic caps, all "SMPS" looking SMD coils, and all discrete components, diodes and what not, in the immediate vicinity of the main/power connector at the back of the unit. ZERO voltage everywhere. If the screen/front panel was at fault, the mainboard would still be running so I would be able to see supply VOLTAGES and theunit would draw at least SOME current ! But it draws absolutely zero, and zero voltage anywhere. So there is no point worrying about the display or flat flew cables at this point I think ! 

4) REGARDLESS of whatever magic the unit might perform to "decode" its numerous inputs, to decide if it will be so kind as to power up the unit... this smartness is embodied by circuitry, a CPU, or a dedicated power management chip or discrete circuitry or SOMETHING.... this means that even if the conditions for the unit to power up were not satisfied, the smarts inside the unit would be powered up anyway and therefore draw some current and need voltage to run.... but since I can't even witness the slightest current draw... it means the main board is just not "upset" with the way I wired it... it's more like it's simply not powered up AT ALL !

So I am now shifting from a "No display" fault, to a "No Power" fault.... not at all the same thing...

Zerto votlage and zero current... it's just like the main fuse was blown, as simple as that ! Yeah, I did check the fuse... it's fine...

Next step is to unscrew the main board from the chassis, so I can inspect the underside of it, and access the pins of the power connector. I will trace the +12V pin to see where it lands on the top/component side, then trace it there.

But it's too late now, going to bed.  Before I waste time on this thing, I will the owner who actually lives just 500m from me, so he can come with his car. I will ask that we  reconnect the stereo to his car, so he can show me if he really can get this thing to work.... as a quick sanity check. If it does power up and work, then I don't understand how that's possible 

More tomorrow then, good night ! 

I respect what mnem has to say, but personally I'm not so sure about not needing the Can Bus to be functioning. Everything on my car is completely controlled by dozens of ECU's, all internected via Can Bus and all switches etc are hooked into the Can Bus so that in the event of someone leaving the radio or some other gadget, light etc switched on when leaving the car, the system can detect this and switch it off to preserve the battery. I think a little more detective work might be in order to double check if the Can Bus has to be connected first in the first instance to provide the ability to power it on via the on/off switch. Another thing that you are likely to require is the security code for the radio as once the battery is disconnected the anti-theft system is also likely to have kicked into play and may have to reset the system in order to power it on again.

Yeah, this is an aftermarket radio, so shouldn't need the CANbus to turn on... at least for initial setup. If it has already has been configured for CANbus on a specific car (this is sometimes a specific CANbus decoder brick, sometimes a setting in the FW or both) so that the steering wheel, climate control, door locks, etc all integrate with the head unit, then it MAY need to be connected to that car to turn on at all. Hmmmm...

It may need to have factory reset done on it to be able to power it up out of the car, once it has been configured... which you probably cannot do without getting the screen online... not sure if there is some equivalent to the Recovery Mode "3-button salute" like a android phone has.

This is starting to feel like one of those bricked BT device recursion problems... 

mnem
Another rabbit-hole...