These will be the final words I have to say about my experiences of trying to get hold of a working Mustool G600 microscope. I'm offering these by way of closure on the subject of replacing damaged Mustool G600 display panels'.
The Ebay supplier of the second broken unit refunded the purchase price and just like Banggood, gifted me the broken unit for me to dispose of rather than be burdened with return postage costs. Shortly afterwards, I received the replacement TFT panel I'd ordered from buydisplay.com only to be greeted with a blank but lit up screen when I connected it to the Banggood unit followed by the same result when I tested it with the second unit I'd bought from the Ebay seller.
I'd never seen any sign of an image on the broken Banggood unit but the first Ebay unit had displayed an image on the part of its broken screen that could still respond so although the Banggood unit may have suffered damage beyond that of just a cracked display panel, I knew the first Ebay unit was still outputting video data over the 40 wire interface, hence my retesting with that unit.
At that point, I had no other means of testing any of the display panels other than by using the first Ebay unit. I couldn't even run a basic DMM test to confirm power supply connections and signal input lines at that point for lack of a breakout converter to give me access to the individual contacts in the 0.5mm pitch 40 lane flexi-pcb connector so landed up trying to convince buydisplay.com to accept my assertion that they'd sent me a faulty display panel.
Eventually, I did manage to source a suitable breakout adapter board, cheap enough to take a chance on spending yet more money (£1.98 in this case from an Ebay seller shipping out of a UK based warehouse in a more reasonable time frame of a week - it turned up just 4 days later) which finally allowed me to buzz out the interface connections with a DMM to compare the Mustool panels against the buydisplay panel.
Buydisplay had asserted all along that the issue could only be a matter of compatibility but rather unhelpfully, failed to suggest any ways in which such an incompatibility could arise making it look like they were trying to bluff their way out of refunding me for supplying a defective panel.
Unfortunately, whether by bluff or a genuine belief that their display was defect free by virtue of their alleged pre-shipping inspection and testing, it looks like they were correct in this assertion. Both panels matched except for the green and blue data lines (pins 13 to 28) all being open circuit (NC) in the Mustool display interface whilst the buydisplay panel conformed exactly to the 40 wire 24 bit parallel RGB ttl level interface of the common 40 wire standard used by virtually all such display panels (and in accordance to the data sheet I'd downloaded from buydisplay.com for their panel).
From what I've been able to glean from the on-glass controller IC datasheets (which are difficult to interpret in relation to any 40 wire interface pinout schemas), it looks as though the Mustool display is using a bastardised 8 bit parallel interface where the RGB data is multiplexed over those 8 data lines at a dot clock frequency of 20MHz which is just over twice the normal 9MHz dot clock frequency used in the ubiquitous 40 wire common standard colour TFT LCD panel interface.
In all my researches of the 40 wire TFT LCD panel interface standards, I'd seen no references at all to this bastardised 8 bit version, not even when I started searching specifically for such a supposed bastardised version (other than seeing indirect hints of such a possible bastardisation in the TFT panel on-glass controller IC datasheets).
Regardless of whether my supposition about multiplexing the RGB data with a 20MHz dot clock frequency is actually correct (ICBA to examine 'scope traces even though I now have a breakout adapter to make such testing a real possibility), the differences are sufficient to support buydisplay's claim of incompatibility rather than a defective panel being the cause of my not being able to get their panel to work with these Mustool microscopes, leaving me to admit that their supposition was correct all along and make my apologies for doubting their diagnosis.
In the meantime, I'd placed another order for yet another of these Mustool G600 microscopes (just a mere £25.58 this time since I didn't need the more expensive aluminium stand option - I already had a couple to spare) with yet another Ebay trader also shipping from a UK warehouse which actually arrived intact... Yay!!! The only
minor issue being that the blue SMD LED was missing from the main camera board.
This issue was
minor simply because I now happened to be blessed with
two spare broken units from which to cannibalise a rear case half with
working blue and red SMD LEDs on their control boards - I chose the first ebay unit as my donor rear case half and,
finally at long last, had myself a
fully functioning unit less than half an hour later (and it only took some seven weeks and three order attempts in total to attain this seemingly impossible goal). In this case, it was most definitely a case of "Third Time Lucky!"
Now all that remains is to sort out a return to buydisplay.com who appear to have agreed to accept such a return provided I bear the return shipping cost which in the circumstances (my mistake not theirs), seems only reasonable. Checking out Royal Mail's pricing, it looks like I'll be able to return it via their standard large letter international shipping rate (6-7 days delivery target) for just £3.45, leaving me just over 7 quid better off than if I were to simply put it in my parts bin to go unused for the rest of my natural life (I foresee no future use of such a panel... ever!).
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[EDIT 20191120 22:54]
I shipped the panel back to buydisplay a fortnight ago as per the above and finally got email replies from ebay and paypal this morning, confirming that buydisplay had received the panel intact and had made good on their promised refund. Not unexpectedly, since the original purchase had been based on their USD price, I lost £1.03 to the currency exchange rate commission charges involved in each transaction.
Overall, that exercise in how not to choose a replacement panel, based purely on assumed properties of a seemingly identically specced unit, had cost me the £3.45 return postage and currency conversion commission charges of £1.03 plus the £2.98 I'd paid for the two 40 way 0.5mm pitch breakout adaptors needed to make it possible to buzz out the connections, a grand total of £7.46 against my initial purchase cost of £11.64, leaving me better off by a net of just £4.18 by returning it for a full refund rather than just simply "Doing Nothing".
It could be argued that the £2.98 spent on the break out adaptors is a small investment in my armoury of test gear adaptors which will allow me to check out any more of these common 40 wire interfaced display panels I may need to test. Putting this test gear adaptor investment aside, I can console myself with the fact that the essential cost (return shipping and currency conversion commissions) had been a mere £4.48 leaving me with a net refund of £7.16 and a pair of break out adaptor boards to add to my test gear inventory.
The adaptors take up far less space and will more likely prove useful than a display panel which will likely remain unused as mute testament to my original folly of a doomed repair attempt on those damaged Mustool G600 microscopes.
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Just to reiterate, anyone thinking of replacing a faulty Mustool G600 display panel had better be prepared to do a lot more research before ordering a compatible 4.3 inch colour TFT LCD panel with a 40 wire interface with the very
uncommon multiplexed 8 bit parallel RGB 20MHz clocked interface protocol standard (not hard fact, just my best supposition from what little evidence I could indirectly glean from TFT controller IC datasheets).
Finding a suitable panel is far from the straight forward job that all my extensive research efforts had led me to believe it was going to be ("It's a 40 wire TFT panel, just how hard can it be?" - Answer:
Very!). It has been said by many (and many times over) that you only
really learn from your mistakes.
I can say I've truly learnt something from this. Not so much about display technology per se so much as never trust a China-man to do the honourable thing when designing cheap electronic gadgets you'd reasonably assume to be using commodity parts. IOW, when it comes to Chinese manufactured electronics, make no unwarranted assumptions without full documentation to back them up.
Indeed, when it comes to Chinese made mains powered smpsu circuit boards, it's definitely SOP to closely examine them
before risking a connection to your local mains supply since they so often seriously breach electrical safety regulations in their construction. In most cases, such safety breaches can be put right by a relatively trivial reworking of the smpsu components (and where required. a safety earth connection to exposed metal parts).
The KSGER T12 oled soldering station for example not only needed the low voltage diode heatsink fins to be reshaped to eliminate contact against the solder resist mask on a 350vdc trace, the metal case also required a connection to be added to the protective earth tag in the C14 mains socket which had only been wired to the soldering iron tip contact to fulfil their advertised ESD safety requirement. For some inscrutable Chinese reason, they don't seem capable of thinking '
inside of the (metal) box' let alone
outside of it!
JBG
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