+OLD CS1 Posted December 15, 2010 Share Posted December 15, 2010 The console OLD CS1 sent me is also fixed, 1 bad DRAM. The power supply buzzes though, so I'll probably swap it out now that I have a stock of consoles in various conditions. Interesting. I wonder if it was a bad power supply which popped the RAM. Quote Link to comment Share on other sites More sharing options...
thej Posted December 28, 2010 Share Posted December 28, 2010 I thought you had a black screen with a death screech ??? Not mine; mine was the garbled Master Title Screen. What was the source of this problem ?!? I have a TI99/4a with the same problem and I want to fix it myself. @Mathew180 Have you considered writing a Symptom/Solution Guide? I'm sure there are lots of people that would fix their own units (or a friends) if they had a reliable starting point. I've scoured the internet and Repaired Macs, C64s, Colecos, NES and now hopefully a TI99/4a I know others can contribute to the cause too! TheJ Quote Link to comment Share on other sites More sharing options...
matthew180 Posted December 29, 2010 Author Share Posted December 29, 2010 To some extent. So far the only problems I have seen with a 99/4A have been a bad DRAM, aside from the obvious physical problems (busted keyboards seems to be very common). Maybe a power supply too. I am planning to take a bad DRAM and put it in each of the 8 locations of the VRAM memory and take a picture of the screen. This might help people isolate which DRAM is bad (if the screen is unique enough between each location with a bad DRAM.) Also, I might write a simple VRAM memory test that runs from a cartridge. I already did this for the 32K module I was working on and it helped locate both bad DRAMs. By the way, desoldering chips from flow-soldered boards is a serious pain, and the age of the 99/4A does not help any. It is very easy to lift a pad or a trace, at least where the DRAM chips are concerned. On some of the DRAM chips where the bottom was just a pad without a trace connection, simply heating the solder, like if you were just going to reflow the pin to fix a cold solder joint, was enough to lift the pad! Luckily it did not affect the top pad or through-hole and did not affect the functionality of the chip. Quote Link to comment Share on other sites More sharing options...
marc.hull Posted December 30, 2010 Share Posted December 30, 2010 By the way, desoldering chips from flow-soldered boards is a serious pain, and the age of the 99/4A does not help any. It is very easy to lift a pad or a trace, at least where the DRAM chips are concerned. On some of the DRAM chips where the bottom was just a pad without a trace connection, simply heating the solder, like if you were just going to reflow the pin to fix a cold solder joint, was enough to lift the pad! Luckily it did not affect the top pad or through-hole and did not affect the functionality of the chip. Sound like you need a six dollar Radio Shack desoldering plunger !! Sorry, couldn't resist... Quote Link to comment Share on other sites More sharing options...
+OLD CS1 Posted December 30, 2010 Share Posted December 30, 2010 Sound like you need a six dollar Radio Shack desoldering plunger !! Sorry, couldn't resist... You got ripped, Jack. I paid $6 for the whole kit! Quote Link to comment Share on other sites More sharing options...
matthew180 Posted December 30, 2010 Author Share Posted December 30, 2010 Actually I have a robotic, double optic, triple lindsey, radar, laser aligned, thermal heat couple controlled, atomically aligned integrated circuit extractor. And the pad still lifted. I think the pad probably lifted during the original soldering and was just being held there by the IC's pin and solder. Quote Link to comment Share on other sites More sharing options...
thej Posted December 30, 2010 Share Posted December 30, 2010 Actually I have a robotic, double optic, triple lindsey, radar, laser aligned, thermal heat couple controlled, atomically aligned integrated circuit extractor. And the pad still lifted. I think the pad probably lifted during the original soldering and was just being held there by the IC's pin and solder. What is the best method to desolder theses chips? I currently have a solder station (adjustable heat setting) with solder wick (I'm too good for desolder bulbs TheJ Quote Link to comment Share on other sites More sharing options...
matthew180 Posted December 30, 2010 Author Share Posted December 30, 2010 The "best" method depends on who you ask. Desoldering is like 10 times harder than soldering, and for the last few years I've been using a poor-mans version of a hot-air bath in conjunction with ChipQuik. Start here: http://zeph.com/ They have a really good set of white papers on the soldering / desoldering process, as well as nice tools if you can afford them (I can't). You can find ChipQuik kits on DigiKey, Amazon, and other places, and the $20 kit will do quite a bit of delodering for a hobbyist. I made a hot-air bath with my heat gun (temperature controlled Makita), and a metal stand made from big joist hangers. I used an oven thermometer to calibrate the heat at the location of the circuit board when placed on my stand above the heat gun. Basically you are reproducing the pre-heat cycle of the manufacturing process. Once the board is pre-heated, I touch a little ChipQuik to each pin with my soldering iron, and the mixing of the new alloy stays liquid at the hot-air bath temperature (which is way lower than soldering temperatures). The is a very low temp, low stress desoldering method. Once all the pins have been mixed with ChipQuik, I can remove the part with hemostats. Then I use a solder sucker, 99.9% alcohol, and Q-tips to clean the holes. Oh, and there is some cleaning and no-clean flux through out the whole process. Pre-cleaning is a must and I usually use 99.9% alcohol and a plastic-bristle brush to clean the area first. Quote Link to comment Share on other sites More sharing options...
marc.hull Posted December 30, 2010 Share Posted December 30, 2010 Actually I have a robotic, double optic, triple lindsey, radar, laser aligned, thermal heat couple controlled, atomically aligned integrated circuit extractor. And the pad still lifted. I think the pad probably lifted during the original soldering and was just being held there by the IC's pin and solder. What is the best method to desolder theses chips? I currently have a solder station (adjustable heat setting) with solder wick (I'm too good for desolder bulbs TheJ My two cents.... #1) Cut, pull and clean if your after the board. #2) suck, wick and pry if your after the chips #3) pray.... I usually don't have a whole lot of trouble with a plunger, wick and some compressed air. The biggest PITA's for me are the double sided ground traces. They tend to requires about three times the effort (and the air canister.) Of course this is the twelve dollar Radio Shack guy speaking. There are many ways to skin a cat . There is another method I know works on the TI cart boards but I have never been brave enough to try it on a MOBO. You can (and I have done it) simply pry the chip out with a flat blade screw driver and then easily get the solder out with no damage done to the chip or the board. These are single sided boards though. Perhaps I'll give it a shot on a dead MOBO and see what happens. Might be good for harvesting chips anyway. Quote Link to comment Share on other sites More sharing options...
kl99 Posted January 7, 2011 Share Posted January 7, 2011 @Mathew180 Have you considered writing a Symptom/Solution Guide? I'm sure there are lots of people that would fix their own units (or a friends) if they had a reliable starting point. I have found a guide what to do, when your console locks up (freezes): See Micropendium, 1989 August, Page 46: ftp://ftp.whtech.com/magazines/micropendium/mp8908.pdf I will continue searching and posting here... Quote Link to comment Share on other sites More sharing options...
chris36 Posted January 8, 2011 Share Posted January 8, 2011 My Broken Gear: For Donation. I bought a working black/silver model that is my working primary. I bought a beige unit to tinker with. This unit worked for 10 minutes and then quit. I bought a second beige unit to do "A-B" tests between the units. Symptoms of the broken unit are the unit powers on with a single color screen and a constant tone. Flicking power switch off/on results in a different color screen and tone. I replaced the VDP but symptom remains. I've played with it awhile but time and money constraints (i.e. gearing up cost) will probably prevent me from eventually fixing it. Since I already have two working units, I'd like to donate it with the provision that when you get around to troubleshooting it (no rush), that you post what the problem was to satisfy my curiosity. It will be sent as is (i.e. disassembled) if you want it. PM me with shipping instructions. 1 Quote Link to comment Share on other sites More sharing options...
matthew180 Posted January 8, 2011 Author Share Posted January 8, 2011 Your problem does not sound like the VDP or VRAM. Try this: there are 4 other socketed chips on the board besides the VDP. They are over by the CPU, three are the system GROM chips, the other is the sound chip. Swap the three GROM chips from one of your known good consoles. If it works, swap in the original chips until you find the bad one. If it is still broken after you try that, let me know. Quote Link to comment Share on other sites More sharing options...
chris36 Posted January 9, 2011 Share Posted January 9, 2011 Your problem does not sound like the VDP or VRAM. Try this: there are 4 other socketed chips on the board besides the VDP. They are over by the CPU, three are the system GROM chips, the other is the sound chip. Swap the three GROM chips from one of your known good consoles. If it works, swap in the original chips until you find the bad one. If it is still broken after you try that, let me know. Done. I swapped one chip at a time between mother boards, starting with the three GROM's and ending with the Sound Chip. After each chip swap, I confirmed that the working board came up to the TI start up screen and that the broken one did not. All four were swapped with no change in behaviour (the working one still works, the broken one is still borked). Chris Quote Link to comment Share on other sites More sharing options...
matthew180 Posted January 10, 2011 Author Share Posted January 10, 2011 Weird. You can send it when you want, I can't say when I might fix it though, particularly since there have been ZERO requests for gear... The symptom you described sounded just like a console I had and it turned out to be a GROM that just needed to be reseated in the socket. I have yet to see a failed VDP, and when VRAM goes bad you usually have a jumbled looking screen, not just a solid color. I suppose it could be a buffer chip or something on the bus somewhere. The sound chip's oscillator input comes from the VDP (GROMCLK), and the GPL power on routine in the system GROM turns off the sound chip (which is full on at power up). So, since you have a constant tone, the power on routine is not even getting to the point where it shuts of the sound chip. I'll PM you my address if you want to donate. Quote Link to comment Share on other sites More sharing options...
chris36 Posted January 12, 2011 Share Posted January 12, 2011 Weird. You can send it when you want, I can't say when I might fix it though, particularly since there have been ZERO requests for gear... The symptom you described sounded just like a console I had and it turned out to be a GROM that just needed to be reseated in the socket. I have yet to see a failed VDP, and when VRAM goes bad you usually have a jumbled looking screen, not just a solid color. I suppose it could be a buffer chip or something on the bus somewhere. The sound chip's oscillator input comes from the VDP (GROMCLK), and the GPL power on routine in the system GROM turns off the sound chip (which is full on at power up). So, since you have a constant tone, the power on routine is not even getting to the point where it shuts of the sound chip. I'll PM you my address if you want to donate. Hit me up with a PM. If your stocked up in gear then maybe I'll be your first customer. I think I've managed to get the minimum post count now. Will have to check into shipping cost. Do you want me to reassemble the console before sending? Adding a post on one or both of the TI-99 Yahoo groups might generate some more interest. Regards, Chris Quote Link to comment Share on other sites More sharing options...
Opry99er Posted January 12, 2011 Share Posted January 12, 2011 Black screen and endless screech.... What would the cause of this be? Quote Link to comment Share on other sites More sharing options...
mimo Posted January 12, 2011 Share Posted January 12, 2011 can I apply for a GSK basic or super? I have been an active Atari Ager for a few years. Not active in the 99 forums but have been following things for the last few months. That has whetted my appetite for a 99) I am in the UK though so that may be a problem, although I have lots of NTSC gear that I use regularly (heavy 6'er,7800.1200xl,32x) Quote Link to comment Share on other sites More sharing options...
Opry99er Posted January 13, 2011 Share Posted January 13, 2011 Hi mimo.... Not sure what you're looking for exactly--- GSK super? Welcome, by the way. always great to see new faces here. (or avatars). Quote Link to comment Share on other sites More sharing options...
mimo Posted January 18, 2011 Share Posted January 18, 2011 sorry for the late reply, a GSK super would be great, all depends on the shipping cost though. It may be cheaper to try and find one in the UK, but prices are pretty high over here at the moment Quote Link to comment Share on other sites More sharing options...
+retroclouds Posted January 18, 2011 Share Posted January 18, 2011 sorry for the late reply, a GSK super would be great, all depends on the shipping cost though. It may be cheaper to try and find one in the UK, but prices are pretty high over here at the moment hhmm, ok now I'm curious .... what is a "GSK super" ? Quote Link to comment Share on other sites More sharing options...
Charlie_ Posted January 19, 2011 Share Posted January 19, 2011 I *think* I have two non working computers in a box. They are all taken apart. I remember getting an ebay auction for two systems, 1 didnt work and i took the keyboard to fix another unit I had with a bad KB. Anyway I have this box of TI-99/4A parts and I'd be happy to send it to you if it would help other TI99 users. Quote Link to comment Share on other sites More sharing options...
matthew180 Posted January 21, 2011 Author Share Posted January 21, 2011 Hit me up with a PM. If your stocked up in gear then maybe I'll be your first customer. I think I've managed to get the minimum post count now. Will have to check into shipping cost. Do you want me to reassemble the console before sending? Adding a post on one or both of the TI-99 Yahoo groups might generate some more interest. Regards, Chris Sorry for the delay, been tied up with work and life. I'll send you a PM with my address. Just to clarify, you are wanting to swap bad for good, correct? Should not be a problem. Also, it does not matter to me if you reassemble the units, but that is probably the best way to package them for shipping. Quote Link to comment Share on other sites More sharing options...
matthew180 Posted January 21, 2011 Author Share Posted January 21, 2011 can I apply for a GSK basic or super? I have been an active Atari Ager for a few years. Not active in the 99 forums but have been following things for the last few months. That has whetted my appetite for a 99) I am in the UK though so that may be a problem, although I have lots of NTSC gear that I use regularly (heavy 6'er,7800.1200xl,32x) Hey Mimo, sorry for the delay. I can hook you up with a console, but I have no idea what a GSK is... Is it possible you are thinking of some gear for a different system? Quote Link to comment Share on other sites More sharing options...
matthew180 Posted January 21, 2011 Author Share Posted January 21, 2011 Black screen and endless screech.... What would the cause of this be? The only thing I have seen fail on a 99/4A so far has been VRAM (DRAM chips) or a GROM (which in my case it only needed to be reseated.) I had the same problem and after swapping GROMs with a know good console, my problem cleared up... Quote Link to comment Share on other sites More sharing options...
chris36 Posted January 21, 2011 Share Posted January 21, 2011 can I apply for a GSK basic or super? I have been an active Atari Ager for a few years. Not active in the 99 forums but have been following things for the last few months. That has whetted my appetite for a 99) I am in the UK though so that may be a problem, although I have lots of NTSC gear that I use regularly (heavy 6'er,7800.1200xl,32x) Hey Mimo, sorry for the delay. I can hook you up with a console, but I have no idea what a GSK is... Is it possible you are thinking of some gear for a different system? From your first post...GSK = Get Set Kit (basic and super versions) Quote Link to comment Share on other sites More sharing options...
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