TT030 Black screen

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TT030 Black screen

Postby paul92706 » Fri Feb 27, 2015 9:26 pm

Hi guys, once again another problem here, Anyhow upon opening up my TT030 and revising the board, and removing PSU and Harddrive and Floppy, again just to revise the board, because i wanted to implemend the Nova VME adaptor, just to get a clear view of what i was going to face upon implementing the project. Now after i quickly assembled it all back together, now the TT030 at power on i get is a BLACK screen! no video signal. Now i quickly disassembled it all and i double check and made sure all IC's were seated in there PLCC sockets and made sure everything was in it's place. I fired her up again, and same thing BLACK screen. Now i checked all clocks, and clocks are ok, now understand this i checked for Address's being floated, and that was a negative no floating of address's, i also checked the /AS line and that wasn't being asserted. I also checked the R/W and that also was not being asserted, and also checked the /DS and that wasn't being asserted, looks like all Strobing is being halted. I also checked the /BERR and that has held high, which means there is no Buss error. Hmmm something strange seems like a MPU problem? everything else was working perfect before, not a problem, i would leave the computer on for Hours and hours, without a glitch, how strange this happened upon disassembly! wierd much to wierd! thanks guys
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Re: TT030 Black screen

Postby exxos » Fri Feb 27, 2015 9:41 pm

You didn't break your reset switch did you, I did that other day, similar issues :lol:
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Re: TT030 Black screen

Postby paul92706 » Fri Feb 27, 2015 9:52 pm

exxos wrote:You didn't break your reset switch did you, I did that other day, similar issues :lol:

Good question, you know what Chris, when i recieved this TT030 the Reset swtich was broken, half of the plastic (Reset button) was broken and the other half was insidethe shell. It worked fine with it being this way, i just didn't use the Reset switch i would just power on and power off. But the Reset switch did work, i would stick a very fine peace of needle in there and it would Reset but i would have to pull it back out, so i know the Reset switch isn't jammed, just broken from the Button. I have been trying to mess with the Reset switch more and it doesn't seem to do anything, still black screen. I guess i will order a new Reset button, but i am almost certain it's not the cause of it! or maybe huh! :lol:
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Re: TT030 Black screen

Postby exxos » Fri Feb 27, 2015 10:00 pm

It can't be much if it was working and now isn't. My reset spring flew across the room, no idea where the insides went :lol: It was at night time, so I thought I would leave it until morning. When I connected it up, I forgot the switch was bust and it just sat there black screen. I changed it, then it was stuck on a white screen :lol: I added some more uF to the rest circuit and it solved it. having a working reset switch is always a good place to start :wink:
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Re: TT030 Black screen

Postby paul92706 » Fri Feb 27, 2015 10:41 pm

exxos wrote:It can't be much if it was working and now isn't. My reset spring flew across the room, no idea where the insides went :lol: It was at night time, so I thought I would leave it until morning. When I connected it up, I forgot the switch was bust and it just sat there black screen. I changed it, then it was stuck on a white screen :lol: I added some more uF to the rest circuit and it solved it. having a working reset switch is always a good place to start :wink:

:lol: Your just lucky that little spring didn't get you in the eye :x anyhow, i checked the /Reset signal over at the MPU and it's being asserted correctly, it is set to High at power on and when i press in the Reset button it goes low, as it supposed to. So this is telling me it maybe something else no? These earlier revision TT030's have alot of PLCC type Sockets and IC's im thinking maybe one of these can be gubbed, i have heard these sockets pins oxidize, and it looks like some of mine are pretty dual looking also? whats your opionion on this one? i will order a new reset switch, i just hate the down time :x of shipping!
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Re: TT030 Black screen

Postby exxos » Fri Feb 27, 2015 11:01 pm

If your reset switch is making the RESET line go high and low, then it seems good. You could spray and wipe the IC pins and sockets with IPA, cotton bud will get the black off it all. Im not sure from your post if your TT was working before you tried the card in place ? was the card knowing working to start with ? possible it could have killed the CPU ?
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Re: TT030 Black screen

Postby paul92706 » Fri Feb 27, 2015 11:05 pm

exxos wrote:If your reset switch is making the RESET line go high and low, then it seems good. You could spray and wipe the IC pins and sockets with IPA, cotton bud will get the black off it all. Im not sure from your post if your TT was working before you tried the card in place ? was the card knowing working to start with ? possible it could have killed the CPU ?

I will try this later, is this Alcohol your talking about IPA? yes my TT was working flawlessly before, i havn't added the card, i was at the starting stages of making the card. I was just revising the motherboard board when i took it all apart, to get some basic dimensions in fitting the card i was gonna make.
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Re: TT030 Black screen

Postby exxos » Fri Feb 27, 2015 11:09 pm

isopropyl alcohol. Strange how you pretty much took the lid off and it stopped working ? You could try pushing down on each chip in turn while turning on the psu and see if you can locate where abouts the a bad connection might be. Also tip it upside down and just give it a few taps in case you have a stray bit of solder floating around in there or a screw or something daft.
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Re: TT030 Black screen

Postby paul92706 » Fri Feb 27, 2015 11:37 pm

exxos wrote:isopropyl alcohol. Strange how you pretty much took the lid off and it stopped working ? You could try pushing down on each chip in turn while turning on the psu and see if you can locate where abouts the a bad connection might be. Also tip it upside down and just give it a few taps in case you have a stray bit of solder floating around in there or a screw or something daft.

ya pretty strange huh, how i just took off the lid and gubbed! Yea what i will do this weekend is clean all those pins on each PLCC socket and try and remove some off that oxide built up, and do as you say press on some chips firmly and hold the board upside down and see if any stray bits may come undone. Im thinking this is the case some stray solder or an oxide pin that just needs cleaning. I will let ya know how it all works out, thanks for your help buddy! :D
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Re: TT030 Black screen

Postby Guest » Sat Feb 28, 2015 8:59 am

if the screen is black the machine is either stuck in reset or the mpu isnt being clocked
if you test halt and reset with a voltmeter they should go low high from boot and both stay high
if the halt goes low even for a flicker there is a problem with an ic

i feel as talk about the reset button has an issue
easy done .. if you take the pcb out the TT without removing the gray plastic cover...

you can also test the PG power good signal is high

looking at the pics i see its a reva or b board with the daughter board the rev c has the cpld chips on the motherboard
and a socket for a 68030 32mhz .. the daugher board one is either an A or B
make sure its plugged in properly and the small cable for the clock is connected to it
also check the 16/32mhz clock jumper isnt missing
also why do your eproms have no UV protection labels ???
they are needed or sunlight/daylight will erase them even strip lights or energy efficient bulbs give off UV
all it takes is one cell to discharge {over 1000 X8 bits in each ic}
and the machine will malfunction with a CRC error and will give you a black screen
and the machine looks dead but usually the mpu will halt but not always...

i would rather at this point see you use a test cart and a rs232 cable
after checking the obvious stuff... read over the service manual you can get it on devdocs...
http://dev-docs.atariforge.org/files/TT ... l-1991.pdf

perhaps this is the cause... you could also try to reset the nvram
perhaps its become corrupted if you power on with all the perifs removed then info is written about the new config
so can cause an issue ive had this before with the TT it turned out to be a fautly nvram memory segment..

the pic below shows the power on reset timer and the reset button timer
you can test at the right pins of the ttl buffer the 555 timers drive and see what levels you have,,,
for xrst and xhalt xpor etc if you need a cart perhaps bradly {best} has one i know he is not far away... i think he would even lend you one
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Re: TT030 Black screen

Postby paul92706 » Sat Feb 28, 2015 4:24 pm

Hi simbo, I will definitly check the Reset Circuitry and if there is a problem. ALso good point on the NVRAM, i did not know this could cause a problem when removing devices, so i will need to check this out also, how do i Reset the NVRAM?. I will also check (PG) power good signal to see if thats active high. Ah! yes i forgot to cover those Eproms, i just burned a fresh pair and was dam lazy to protect them, thanks for that advice. I will also check thos outputs from 555 Timer, huh, i never knew Brad lends out test cards, i will give him a ring, and see if i can borrow. thanks kindly! :)
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Re: TT030 Black screen

Postby paul92706 » Sun Mar 01, 2015 9:02 pm

ok update, i cleaned all PLCC sockets and IC's and, i doubled checked Xrst and Xpor and are asserted correctly. I reburned new EPROMS and protected them from UV. I also check PG signal it is high at power on, so this is good. I check VCC and GND at MPU and all is good. I also check all clocks and all is good. After all this checking the same problem, black screen. Now i check again Address/Data/Strobe signals and there is no activity going there. I also check /Halt signal and it does not flicker at power on, it is asserted to high, so this good. I am getting a strong suspicion that my MPU took a dump!. Is there anyway i can check to see if the MPU is really Gubbed? thanks
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Re: TT030 Black screen

Postby Guest » Mon Mar 02, 2015 11:25 am

so when you burned the eproms
did you disable the 'write 0XFF to the end of the ic' ???
you need to disable it
first thing to do is flash the ics without this setting

then double check the CRC

black screen is no bios load white screen is bad stram or bad funnels
only no tos load
because you need tos to start too load the gdi to init the video ??
perhaps its just the roms :cheers:

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Re: TT030 Black screen

Postby paul92706 » Mon Mar 02, 2015 11:36 pm

simbo2 wrote:so when you burned the eproms
did you disable the 'write 0XFF to the end of the ic' ???
you need to disable it
first thing to do is flash the ics without this setting

then double check the CRC

black screen is no bios load white screen is bad stram or bad funnels
only no tos load
because you need tos to start too load the gdi to init the video ??
perhaps its just the roms :cheers:

Hi, simbo, ok i reburned eproms and disabled write 0XFF. Did a power on and samething black screen. Now i strongly believe it's the MPU gubbed. How can i be certain that MPU is really gubbed? before i order a new on ebay. thanks
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Re: TT030 Black screen

Postby Guest » Tue Mar 03, 2015 12:21 am

if the halt is low the mpu is halted

did you check its getting clock signals

the jumpers for the roms are set too the right type???

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Re: TT030 Black screen

Postby paul92706 » Tue Mar 03, 2015 4:23 am

simbo2 wrote:if the halt is low the mpu is halted

did you check its getting clock signals

the jumpers for the roms are set too the right type???


the halt is held high, and all clock signals are ok, now on jumpers for ROMs were previously set and was working with these ROM's, so i think they are ok.
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Re: TT030 Black screen

Postby Guest » Fri Mar 06, 2015 10:01 pm

its a good guess then the mpu has failed or the mcu or dma
usually you get a white screen even if the dma fails
so leaves mpu and mcu...
lets hope a working mpu will fix it
otherwise its a few tests and making a chart of results to track the issue down

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Re: TT030 Black screen

Postby paul92706 » Fri Mar 06, 2015 10:27 pm

simbo2 wrote:its a good guess then the mpu has failed or the mcu or dma
usually you get a white screen even if the dma fails
so leaves mpu and mcu...
lets hope a working mpu will fix it
otherwise its a few tests and making a chart of results to track the issue down

You are 110% right simbo, mcu and dma give off a white screen, as i had this happen on another board. i already desoldered the mpu from the daughter board, it wasn't as difficult as i though it would be, i just used the old hot air gun and wah-la!. I already gave you my mailing address simbo threw private mail, so as soon as the mpu arrives i will solder it back on and cross our fingers and see what gives! :D
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Re: TT030 Black screen

Postby ST Graveyard » Fri May 04, 2018 4:50 pm

Did you ever manage to fix the TT? I am having a similar problem...
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