repetto74

Hi Ksarul, Thanks a lot that will help for sure . I really want to fix this machine ! I do have some 1uf capacitors available here but they are ceramic so does this make a big difference if I use one of these?

So here is what has been done : Cleaning and reseating all socketed chips + cleaning the module connector pins : still the black screen. It is not possible to swap the PSU boards as the pin connector are not the same on both boards. On the broken ti99 the boards has a molex connector while on my TI99 the connector is on the board so I get a male/male connection. My PSU board do not have the diodes soldered on the power plug chassis so I think the one broken is not causing the black screen (I unsoldered it as it is completely broken off). NOw next move will be to swap any socketed chip onto my working board and check if any is faulty. Glad to have any advice that may help at this stage

Hi ! Is the Flashrom99 kit stil available for purchase?

I would like to test the PSU board of the working TI99/4A to check if the issue is related to that broken diode/resistor (cannot identify it). The very strange thing I do see is that the PSU board of the bad machine is supposed to be for model TI99/4 where here this board is mounted on a TI99/4A machine according to this link http://www.mainbyte.com/ti99/hardware/power_supply.html I suppose that both PSU are compatible ? The only main difference between the 4 and the 4A was the sprytes addition on the video chip right?

I have disassembled the TI99/4A and have some findings. What I did first is to clean of course the machine from dust. Then what I did was to remove all IC's socketed and to clean legs with light sand paper + alcohol. There are not so many chips with socket (the two with thermal paste I cannot identify and 4 IC's located on top of the CPU (video ram??)). Also cleaned the module connector pins with sandpaper and alcohol. Then here comes the most interesting finding : onto the power input connector there are 3 diodes I believe which are soldered (diodes are marked 104Z on one of them I can also read 50V). I do not think this is a mod but mostly part of the original design of the power circuitry. Now as you can see from pictures one of those diode is cracked. The glass body is broken on one side leaving the internal circuitry exposed. I do not know how much this can have an impact on a black screen on startup but I assume it should maybe not work properly if cracked that way. How can I measure the integrity of a diode with a multimeter? ref 104 does mean what exactly in terms of voltage? So probably changing this diode is the first thing to do and then retest the machine again. As most of the IC's are soldered I will have to start unsoldering if T/S will have to resume so I would like to try anyway to point out the IC's which are most commonly involved in this kind of failure. (all 8 rams on the left side I suppose). Another finding is on the power supply PCB (the small PCB inside the TI99 where to power switch is located). I can see some components I would identify as diodes also but some and in particular one look quiet odd. Inside the transparent glass cover the circuitry is not straight from lead to lead but looks like bending on one side or looks detached from the diode body (is that possible?? ). I should compare this with the PCB of my own machine to be sure. Thanks

Hi Classic GMR Thanks for the disassembling guide this is just what I was looking for . Also found a thread with same symptoms as mine : http://atariage.com/forums/topic/172939-ti-994a-console-not-working-anymore/ I will start some troubleshooting then. Hope maybe this will be only a RAM fault which can be easily repaired

Hi Guys, I have received from a friend a TI99/4A he got for a few bucks at a garage sale. The guy was not able to say if the machine was working but due to the really cheap price (10 Euros) he decided to pick it up anyway. Unfortunately the machine will not boot up. The power light is on but I do see a black screen with a continuous beep sound. Sound pitch may vary on power recycle. Is there first any tutorial on how to disassemble the TI99? I did repaired some C64 and VIC20 but this one is new for me. I tried to open the case but then leave it as a small PCB inside was attached apparently to both top and bottom cases so did not want to brake it of course. Before doing any stupid thing better to have a tutorial for this one :-) Then concerning the fault where I should start to look at? I have some good experience in soldering/unsoldering + all tools needed. The PSU has been tested working on another TI99 (my machine) so not at fault. Thanks Rick

Hi Guys, Just for you to know, I did built the cable and it is working properly except that the TI99 cannot manage to control the datassette motor so I need to manually record and stop when required :-) Anyway I friend has picked up a couple of days ago a TI99/4A at a local garage sale with the original datassette cable and REM adaptors so he gave them to me .

That's solved then. I had to turn the color pot full counterclockwise position and now the video is cleared from shadows 😉

I have modded today the 6 switch Atari 2600 with the small PCB adapter provided by TheFuturewas8Bit (thanks to them ). I do have an output with color and sound but I would like to be sure that this is the best result I can have with composite. I did the mod following instructions closely, so removed the RF modulator, resistors, transistor and the red coil then wired everything up. As per the pictures taken from an LCD and a CRT TV I can see that colors are a little bit too bright and that there are those annoying vertical shadows lines across the screen. Can this be fixed to improve image or maybe someone can suggest me to check the mod if something may be not correct? There is a resistor I can tweak with a screwdrive I think to adjust color. Thanks Rick

Hi Guys, The cassette recorder is old yes, dated around beginning of the 80's so it should be fine and ouputs mono only. I will build this cable and test it then to check it is properly working . Thanks Rick

I would like to build the cassette deck cable to hook the Ti99/4A to the cassette tape recorder. I have a link to the schematic here : http://mainbyte.com/ti99/hardware/cables/cassette.html so MIC and Speaker will need a 3,5mm MONO audio jack but what about the Remote port ? Which kind of jack do I need for this input? This is smaller than the 3,5mm input. Thanks Rick

Hi Apersson850, Ok now I understand what you mean. Well I would say that considering the fact that the CPU can address 32k of ram maximum I would say that this will be enough for me. I am just a newbie for what concerns TI99/4A and have a lot of work to do in order to use the machine correctly. Actually I need to build a cassette tape cable to use with the cassette recorder. Then I can consider modding the total ram to 32k (found this tutorial https://www.harmlesslion.com/text/TI%2032k%20Mod.pdf)and then maybe later on I may consider a nanoPEB if this piece of electronic is still available for sale :-)

Yes the TV can handle RGB as I connected a Spectrum 128k +2 Grey model which comes with a RGB video output through a SCART cable. Any tutorial on how to do this also?

Hi Apersson850 Any link for a tutorial explaining how to mod the TI99/4A to 64K ?

Hi Stuart Thanks a lot for the schematic. Actually I have various working 8bit machines I would like to output to the same HD TV and with the best option possible. Wherever an S-video mod was possible it was done (Atari XL, VIC-20), composite is the second option when S-video is not possible (ZX Spectrum). The C64 and the Spectrum 128k are respectively S-video and RGB native. I am using a video upscaler AV/S-Video to HDMI which gives a really nice conversion to the HDMI TV. A composite mod to the TI99/4A will be a very good result then :-)

Hi Arcadeshopper, Nope the RF modulator is not the one with the SCART (PERITEL) output for the french market. I got this from an italian e-bayer and the modulator has been manufactured in Italy also but will need a TV antenna input. To Sinphaltimus : thanks for the greetings and will read closely the thread :-)

Working for me also on 10.12.6 !. Thanks that rulez!

Hi to all, I am an happy owner of a PAL TI99/4A since today (I am located in Europe) :-). The machine comes with the RF antenna cable with the big RF PAL modulator and the 6 pin DIN video socket output. I can test this with an old CRT TV I still have but I would like to know what are the best video modding options available to increase video output? Composite, S-video? Any tutorial? Besides that are there also hardware mods available to increase total memory or to improve the machine performance in general? Sorry I am really a noob with the TI99/4A so trying to sum up what is possible to do. Consider that I do have soldering and basic electronic skills + all tools required for the job :-) Many thanks, Rick

Ok looks sorted out now. I had cleaned the unit, added some solder on the swiches solder joints. Now I do have a B&W image for a few seconds then back to color..weird. Anyway I am waiting for the AV composite pad modification to give this machine a video boost!

So I have disassembled the unit. I have read that first thing to do is to turn the pot to fine tune colors. The pot is the white one (regulated resistor) or the red coil in the middle?

So I managed to tune the TV to the have a display. Poblem : -image is in black and white even with the switch TV TYPE set to color (the TV is a color one of course). All other functions seem to work and joysticks will work. I did select a manual + a fine tuning and I did get colors but the problem is that it will return to B&W when turning off the Atari and switching it back on.

Hi guys, I picked up today an Atari 2600 model CX-2600. I had this for few bucks without any guarantee it is working. Hi hooked it up to a standard CRT TV with the RF antenna input at the back but I do not know how to tune the TV. The console does not have a power up light so I cannot be sure that power is applied when turning on the power switch. What should I check first to ensure that the board is correctly powered? I was maybe thinking to go for the composite mod before and check if there is an output on the TV through the video composite inputs. There is also a Channel Select switch at the back for A or B channel selection. What does this mean? Any suggestions? Rick

10 ; 20 .OPT OBJ 30 *= $8000 40 CLR LDA 53770 50 STA 53274 60 LDA 53770 70 STA 53272 80 JMP CLR Yep this will give like the classic loading pattern of a C64 tape . How is that big difference? Ok I see, the VBLK act like a delay so when using the shadow register the video refresh is slower.

Ok guys thanks a lot for your advices I am a beginner in ML coding I need to get deeper into that and I know there are always better ways to code in ML for optimal execution :-)