ti99iuc Posted May 4, 2012 Share Posted May 4, 2012 hi guys ! i have a broken ti99, i tried to change the TMS9929 (it's and European TI) but the problem is not solved... i think it could be a character generator chip but I do not know which chip look.. the ti99 seems to working good, only the character are not visible ok.... i have some pictures to show: and a video.... http://www.andryshou...om/tmp/ti99.mp4 what you think about ? Quote Link to comment Share on other sites More sharing options...
Willsy Posted May 4, 2012 Share Posted May 4, 2012 That looks like a problem with the VRAMs to me. The VRAMS are 1 bit wide. So, eight TMS4116 chips are required to make a single byte, so, if just one chip is dead, ALL of the video will be trashed. It could also be a problem with the power supply board inside the TI. It generates a -5V which is ONLY for the VRAMs (if I remember correctly). The 4116 chips *also* require a -5V signal. This is generated by the power supply board inside the console. There are 4 brown wires coming from the power supply board going onto the mother board. So, with the TI upside down, on the table, with the keyboard at the bottom, the 4 brown cables on the mother board are: +5V GND +12V -5V (I *think* that is correct! - please chip in folks if I am wrong) Also, please check the fuses in the 240v step-down transformer (the black brick). I thought I had killed my console just last week, but it was just the fuse in the transformer! In this thread you can see the location I am talking about (the 5th picture). Click it for a big image. I have wires soldered to GND (black) and +12V (red) for my internal amplifier. Hope this helps. 1 Quote Link to comment Share on other sites More sharing options...
ti99iuc Posted May 4, 2012 Author Share Posted May 4, 2012 T H A N K Y O U Willsy !! i checked the vRAM as you suggested... the broken chip was the 4th... changed and working now Thankyou for helped me one more TI 99er Italian User will be happy to have back his TI repaired Ciro. Quote Link to comment Share on other sites More sharing options...
Willsy Posted May 4, 2012 Share Posted May 4, 2012 Woohoo! Good job! Another console saved! :thumbsup: 1 Quote Link to comment Share on other sites More sharing options...
ti99iuc Posted May 4, 2012 Author Share Posted May 4, 2012 Yeah !! in this week i saved 6 console, this lastone included... !! tha most of ones had keyboard problems... one had a problem on the Internal AC Power and this last one the problem on VRam now i would want repair an MBX, it seems to be broken becouse not recognized from the TI... but i do not understand how disassemble it... i am afraid to break it... there are two screws at the bottom and i removed them, but i don't be able to open the plastic parts... you know ? Quote Link to comment Share on other sites More sharing options...
humeur Posted May 4, 2012 Share Posted May 4, 2012 i confirm this a vram is broken jean louis Quote Link to comment Share on other sites More sharing options...
rocky007 Posted May 4, 2012 Share Posted May 4, 2012 (edited) about your MBX, did you checked everything before opening it ? ( headseat, connectors, power supply ) ? everything else is working ? ( mbx keyboard, speech synth ? ) Edited May 4, 2012 by rocky007 Quote Link to comment Share on other sites More sharing options...
ti99iuc Posted May 4, 2012 Author Share Posted May 4, 2012 Well, i believe yes... i followed all the manual instruction for the cables connection but i have the same message on the screen: "Please Install your MBX Console" ... i tested the power supply and have the correct voltage... so i've thinking for other internal problems... as you write, maybe could be the connection cable but for test it i must open the MBX console... the speech synth seems working good and the headset could give me that kind of error message ? someone have already opened the MBX ? Quote Link to comment Share on other sites More sharing options...
marc.hull Posted May 4, 2012 Share Posted May 4, 2012 Well, i believe yes... i followed all the manual instruction for the cables connection but i have the same message on the screen: "Please Install your MBX Console" ... i tested the power supply and have the correct voltage... so i've thinking for other internal problems... as you write, maybe could be the connection cable but for test it i must open the MBX console... the speech synth seems working good and the headset could give me that kind of error message ? someone have already opened the MBX ? The MBX has a couple of pitfalls... 1) the voltage regulator is attached to the case. When taking it appart you need to be careful not to break the chip off from the legs. Not a big deal if it happens but be aware. 2) It has 2 4bit buffers (I can't remember the numbers, sorry.) They drive the connection between the joystick connector and the MBX. Uplugging the unit when powered up can blow them out. May be a good place to start. They will be the first 2 chips leading to the joystick connection cord. Quote Link to comment Share on other sites More sharing options...
ti99iuc Posted May 5, 2012 Author Share Posted May 5, 2012 The MBX has a couple of pitfalls... 1) the voltage regulator is attached to the case. When taking it appart you need to be careful not to break the chip off from the legs. Not a big deal if it happens but be aware. 2) It has 2 4bit buffers (I can't remember the numbers, sorry.) They drive the connection between the joystick connector and the MBX. Uplugging the unit when powered up can blow them out. May be a good place to start. They will be the first 2 chips leading to the joystick connection cord. Hi Marc! thankyou for the suggestions... i will check the MBX as soon as possible and back again here Quote Link to comment Share on other sites More sharing options...
humeur Posted May 5, 2012 Share Posted May 5, 2012 use module ti diag for testing if your ram broken. jean louis Quote Link to comment Share on other sites More sharing options...
matthew180 Posted May 5, 2012 Share Posted May 5, 2012 Definitely be careful taking the MBX apart. Like Marc said, the voltage regulator heat sink is screwed to the case, but the circuit board is free to fall out once you take the screws out and start to separate the two pieces of the case. I fixed one for someone once and he had already opened the case and accidentally ripped the legs off of the voltage regulator (he was lucky that is all that happened and that no damage was done to the circuit board). I usually take a lot of pictures when I'm working on something, but I can't find *any* for this repair. However, as usual the MainByte website has a nice photo of an open MBX: http://www.mainbyte.com/ti99/hardware/mbx/mbx.html You can see the regulator heat sink attached to the case, but the circuit board could be picked up and break the regulator legs. The way to take the MBX apart is: * KEEP THE CASE TOGETHER! Do not let the case open when the unit is upside down * Take the screws out of the bottom, looks like there will be 6 screws * Turn the MBX over so it is face up. Slowly lift the top off making sure you are not pulling something Here are the two links to threads where MBX repair is discussed: http://www.atariage.com/forums/topic/172843-the-mbx-expansion-system/page__view__findpost__p__2209221__hl__%2Bmbx http://www.atariage.com/forums/topic/175879-mbx-questions/page__view__findpost__p__2295871__hl__%2Bmbx Quote Link to comment Share on other sites More sharing options...
rocky007 Posted May 5, 2012 Share Posted May 5, 2012 a very simple test to start : when you switch MBX on, do you hear "ready" with a female voice from the MBX speaker ? Quote Link to comment Share on other sites More sharing options...
ti99iuc Posted May 6, 2012 Author Share Posted May 6, 2012 Definitely be careful taking the MBX apart. Like Marc said, the voltage regulator heat sink is screwed to the case, but the circuit board is free to fall out once you take the screws out and start to separate the two pieces of the case. I fixed one for someone once and he had already opened the case and accidentally ripped the legs off of the voltage regulator (he was lucky that is all that happened and that no damage was done to the circuit board). I usually take a lot of pictures when I'm working on something, but I can't find *any* for this repair. However, as usual the MainByte website has a nice photo of an open MBX: http://www.mainbyte....re/mbx/mbx.html You can see the regulator heat sink attached to the case, but the circuit board could be picked up and break the regulator legs. The way to take the MBX apart is: * KEEP THE CASE TOGETHER! Do not let the case open when the unit is upside down * Take the screws out of the bottom, looks like there will be 6 screws * Turn the MBX over so it is face up. Slowly lift the top off making sure you are not pulling something Here are the two links to threads where MBX repair is discussed: http://www.atariage....09221__hl__+mbx http://www.atariage....95871__hl__+mbx Perfect, i be able to open the MBX correctly, Thankyou... now there is the hard to do... repair it !! a very simple test to start : when you switch MBX on, do you hear "ready" with a female voice from the MBX speaker ? Yes i tried and no sound to hear but thankyou, it's a good and fast test to do ------- now... the MBX not power on... it's the sure thing... could be the regulator ? there is also a capacitor chipped near the power connector ... could this be the problem you think? it's a 104M ... Quote Link to comment Share on other sites More sharing options...
+acadiel Posted May 6, 2012 Share Posted May 6, 2012 The jack on mine was having issues... had to replace the jack on the main board; here's a thread with the part number from Mouser in case it's one of your issues... http://www.atariage.com/forums/topic/175879-mbx-questions/ Quote Link to comment Share on other sites More sharing options...
ti99iuc Posted May 6, 2012 Author Share Posted May 6, 2012 (edited) Ok thankyou for the suggestion... i will try it too... but it seems to be ok, is not cracked or so... it seems to be perfect... yours too was so ? Edited May 6, 2012 by ti99userclub Quote Link to comment Share on other sites More sharing options...
Willsy Posted May 7, 2012 Share Posted May 7, 2012 On this thread is the following post from Marc Hull: It is pretty easy to treat the MBX like a joystick and just plug it in while everything is hot. It should be noted though that you are basically hooking two computers together and you can cause havoc by doing this. The only MBX I have repaired had two blown 4 bit driver/buffers that handled the joystick interface because someone most likely did just this (aside from the broken VR that Matt mentioned earlier.) When using the MBX the joystick port becomes a serial interface so be careful 8-O. This could be useful information. Mark 1 Quote Link to comment Share on other sites More sharing options...
rocky007 Posted May 7, 2012 Share Posted May 7, 2012 i think first step is to check voltage inside the MBX (and especially on power regulators, if used ). Quote Link to comment Share on other sites More sharing options...
ti99iuc Posted May 10, 2012 Author Share Posted May 10, 2012 yes Rocky, i will do... o will check voltage before ... i'll back again when tested for give you the results guys Thankyou! Cix. Quote Link to comment Share on other sites More sharing options...
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