Repair Marathon 21.04: #2 Aquarius MB-4D50NR Am486DX2-80

[Music] hello and welcome to the continuation of the repair marathon this time i'm going to take a closer look at this 486 main board model mb 4d33-50 this main board was made by aquarius systems and i guess 33 and 50 in the name is because this main board was originally delivered with 33 or 50 megahertz cpus question mark but i might be wrong because it has a variable clock generator which is capable to generate frequencies up to 100 megahertz so actually this main board is not limited to 33 or 50 megahertz cpus as you see from the text on the silk layer this main board supports a lot of fsb frequencies for up to 50 megahertz maybe there was another version which came with clock generator for up to 33 megahertz who knows well let's see what's wrong with it this main board has some damage from a leaky battery which was partially treated but there are still some corners which should be cleaned more properly if you remember i got this main board for this repair marathon from wolf from dolph reloaded e community he said that this main board is actually posting but the keyboard is dead he replaced the connector but it didn't help by the way i am trying to repair all this main board simultaneously in one weekend so for me it is a real repair marathon however it almost takes more time to cut the videos than the repair itself that's why the videos will pop up one after another with some delay in between and sometimes you will see one of the other main board from this marathon in the picture as well even if it is about another one okay as i told i have to make some more extensive cleanup of the oxidation therefore some parts have to be removed i already dissolved the power and the keyboard connectors fortunately there are not many parts which are affected but here you can see the damage quite well i just had to add some white vinegar and scrub the main board with the brush to get it quite shiny again also on the back most of the oxide was cleaned up quite good now i have to wash the main board but before that i have to remove the cpu and the cooler this main board uses a low insertion 4 socket to get the cpu out of it just put a wide flat head screwdriver between the socket and the cpu and rotate it gently but don't apply too much force or you could break the ceramic cpu body by the way the cpu is an amd 486 dx2 with 80 megahertz it has a front side bus of 40 megahertz and it's designed for 5 volt supply it is quite rare since such relatively late 486 cpus were usually made for three volts and were not feasible for an upgrade on an older main board which provides only five volts obviously like this one and since this main board supports up to 50 megahertz front side bus this could be a nice opportunity for overclocking in case this main board will hold its table this will end up in pretty fast 486 build however since vlb is directly connected to the cpu it runs with the same front side bus and usually starts to be very peaky with frequencies above 33 megahertz so the main board has to be very good to keep it stable at 50 megahertz back to the topic time to wash the mainboard just water and soap and as always don't forget to wash everything with a lot of clean water afterwards and give enough time to dry in a warm dry place for about 24 hours after the board got dry i removed the rest of oxide and burst solder mask from the pcb using fine polishing tool there are some residues of the old solder so i remove it using a solder wick and again clean the traces with a dremel on the back side of the pcb now the traces are clean and shiny again i cleaned the surface with some ipa already and now i add a layer of flux to tin the traces due to oxidation neutralization with white vinegar and final polishing the traces lost some strength thinning them we can restore the thickness and protect the copper from further oxidation tinning is easier than many people think with enough flux on the traces the copper surface will literally absorb the solder so if you put a drop of solder on the tip of your iron and move it along the traces the solder will magically find its way towards the traces the narrower the space between the traces the less solder you have to put on your iron tip to avoid bridges between the traces ok time to put back the connectors [Music] i don't show it every time but after every soldering never forget to clean the pcb with some alcohol plugs can be conductive and aggressive on the surface it can damage the pcb over longer periods of time as you see the tint traces on the back also look quite nice and shiny now it's time to prepare the board for the first test let's insert the cpu the 486 cpus are not safe from polarity reversal so always look twice how you insert it into the socket the cpu has this cut corner and the socket has such a marker on one corner as well these corners of the socket and the cpu must match well as i wanted to insert the at power connector i found one problem wolff said that he replaced the keyboard port it is new so i didn't bother to replace it again however it seems not to fit well if i try to push the at power plug into the connector it doesn't go completely down this is because there is this latch which is pushing against the base of the keyboard connector i could cut off the latch on the power plug but i would prefer to make it properly and we'll have to replace the connector by this one as you see it has no plastic borders going around the base so the latch of the power connector would just pass beside the pins okay everything's connected i've been told that this main board posts so let's give it a try seems to wake up it complains about empty battery and missing controller but it's just fine i didn't plug any into the board however it also complains about missing keyboard so far everything seems to be just as wolf described previously keyboard errors are very common on all pcs so let's take a closer look on how it works on an at machine a special controller is responsible for the keyboard input it is such a big 40 pin ic there are plenty of different variants of it in the wild but they are all derived from intel's at42 chip originally used in the ibm's pc80 keyboard connector is d5 type 1. it has 5 pins where pin 1 is clock pin 2 is data pin 3 is usually unused pin 4 is ground and pin 5 is plus 5 volt power supply i will not go into details now but the keyboard uses a protocol on the clock and data pins to communicate with the pc if you are interested in the protocol itself and further details please watch the exciting video by ben ether about it i will put the link down into the description so regardless of the protocol details as i said the keyboard is connected to the keyboard controller the big 40 pin ic the clock is connected to the pin 1 of the ic and the data is connected to the pin 39 sometimes the connections are not direct but are going through inductors or a pair of inverters for filtering and stabilization purposes but basically speaking there must be a connection from pin 1 of the keyboard port to pin 1 of the keyboard controller and from the pin 2 of the keyboard port to the pin 39 of the keyboard controller furthermore you always have to check that you have plus 5 volt supply on the pin 5 of the keyboard port usually it is sufficient to look at the keyboard lamps when you turn on the power if they light up for a moment that means that the power is properly provided if not sure you can still measure it directly on the port using a multimeter on this main board the keyboard gets powered so everything's fine in that regards so let's check what happens with clock and data this is pin 39 of the keyboard controller and it is connected to the inductor l4 down here the pin 1 of the keyboard connector is connected to the inductor l3 so the clock signal should go from the keyboard port to the controller through l3 and the data through l4 let's see on the back side if we have continuity between the keyboard port and these inductors so this is pin one of the keyboard port and it is used for clock as you hear we have continuity on this trace now this is data trace on pin 2. let's see what we get here there is obviously no continuity i'll touch the trace and slide up towards the keyboard connector along it aha you see here we have a continuity and somewhere from this point it disappears we have a broken trace it is barely visible even under magnification but it is somewhere here i will again use the same technique as in the last video a lot of flux and a wire which i will solder on top of the trace i see multiple potential cracks in this tray so i will solder a longer wire in such case it is easier to solder it on one side first holding with a finger from the other one and then straighten the wire and solder the other side [Music] yes short continuation test looks good as i showed in my last video i covered the soldered wire with some nail polish to give it additional protection as well everything's built up again let's give it one more try and as you can see we have only battery error because i didn't install one however an ide controller with a compact flash is already inserted and the keyboard should now work and it does indeed let me make some settings and try to boot into dos [Music] and here we are thos did boots let's see what season 4 says 486 dx 80 megahertz 16 megabyte ram seems to be detected properly benchmark says 172 points which are not bad at all i'd be curious to know how this board behaves when overclocked but it would be a topic out of scope of this video yeah doom is running as well and i'd say this was another successful repair i'm getting a lot of repair requests from many people but i encourage everybody to trust yourself and to give it a try unfortunately one person can't repair everything but i hope my videos will help you to spot and fix the issues with your hardware and bring it back from the dead i hope you enjoyed this video please don't forget to give your feedback thumbs up down share it all the usual stuff and i say thank you and goodbye

Channel: Necroware

Views: 5,514

Keywords: retro, hardware, soldering, repair, review, nerd

Id: 3Yjy8isi5A0

Length: 12min 9sec (729 seconds)

Published: Wed Apr 21 2021