Gunstar, on Sun Mar 26, 2006 6:42 PM, said:
MEtalGuy66, on Sun Mar 26, 2006 11:57 PM, said:
Gunstar, on Sun Mar 26, 2006 2:49 PM, said:
My guess would be a bad GTIA chip. Best Electronics and B&C both sell it inexpensively (S&H not included). Of course if you don't know your way around a soldering iron it may be tuff since XE's aren't socketed.
The most common problem Ive seen on 130xes is bad RAM. Atari used the cheapest crap ram chips they could get their hands on. Usually, if the ram that is bad is high enough that it doesnt effect the loading.operation of the rom based OS, bad ram will send it straight to self-test mode. But if the bad ram is in the section of memory that it needs to load the OS, it could very well keep the machine from doing anything.
I assume that the power LED is comming on on the machine. Its possible that the GTIA is bad.l Its also possible that the CPU is bad.. The fast that it doesnt have socketed chips doesnt prove anything as far as connections go. 130xes are FAMOUS for bad solder joints all over the place.
The guy at the atari service center told me that a common fix for a 130 xe is to lift it a about 1 to 2 feet above the table top and drop it. He said its amazing how many machines would start working correctly after this. Im sure he wasnt seriously suggesting this as a permanent fix, or even a viable one, but he did comment on the fact that the 65/130xes had the crappiest solder joints of any machine atari ever made.
I have 2 130xe's that Ive socketed every single chip, replaced all the ram chips, and been over every solder joint on them. They are both rock solid. But both of them had "issues" before I did that. One of them had never been out of the box!
I don't know how dropping an Xe with soldered chips would do anything. I know this is a solution for the ST's with their socketed TOS chips and other machines with socketed chips, as that's the hole point; if the chips aren't seated well in the sockets, the shock from the drop would jar them into place, though this was also to be done from about six inches high, not a couple of feet! How could this possibly do anything for cold solder points?
A bad solder joint on a machine was obviously good enough to pass the production test at the factory.. How did this happen? Ive never heard of dropping machines PERIOD before this fellow at the ATARI place told me that. WHy the hell would you drop a socketed machine? You could just open it up and reseat the chips manually. Point is, a bad solder connection will often make intermittant contact. Or actually make contact but just too poor (high resistance) contact to function. Often, flexing the board, or shocking the the component will temporarily cause it to make good enough contact to work. Hence the time honored practice of pounding your fist on a malfunctioning TV set, etc. I assure you, the XE series has quite a reputaton for crap solder joints, and intermitant connections as a result. Some XEs are better than others, to be sure.. But the 2 absolute most common problems Ive seen with them is Cheap (bad) ram, and poor connections due to bad solder joints... And while Ive never delberately dropped a machine for diagnostic purposes, I have had XE boards that when flexed a certain way would function properly, and when flexed another way, would act up. Its really not a mind-blowing concept.
I have owned, repaired, or upgraded more XEs than I can recount in the last 15 years or so, and I can tell you with absolute certainty: The 130xe is possibly the most advanced 8-bit machine by design that atari ever made. It is also, on average, the WORST assembled by far. My ex business partner will second this, as he's seen his share of the same thing, and commented many times about "Why couldn't atari build the XEs the same way they built the XLs?"
One thing that REALLY comes to mind is that on several occasions, Ive seen XE boards, that on the right hand side of the board, over by the joystick ports, and all the resistor networks, The solder joints appear normal on the bottom side of the board, but if you look at the component side, you realize that there wasnt even enough solder applied to the joints to wick all the way through the thru-holes. The component legs appear to just be "stuck in the holes" when looking from the top side.. This is fairly prominant on the earlier (16 ram chip) designs. I dont know if the solder they were using was of poor quality, or the plating in the thru holes was just impure, or possibly had oxidization from poor storage practices at atari. Your guess is as good as mine, but Ive often seen this and wondered.
I wasnt saying that this is DEFINITELY the problem. All I'm saying is that it doesnt matter what you are attempting to repair, the best/most efficient strategy is often to check for problems that you know are common to the particular make/model of machine you are working on. More often than not, youll find something right off the bat, and save yourself alot of fruitless testing.
Now.. Heres what ME, MYSELF, and I do with an XE that I plan to keep. I am not sugesting that everyone needs to, or should do this to theirs. First, If its a 16 chip model, I remove all the ram and throw it away. Second, I remove every other chip and IC from the board, and install high quality "double wipe" style sockets. Third, I go over every solder joint on the board with close scrutiny and reheat, clean, remove and re-apply solder as necessary until they all LOOK good. I also replace all electrolytic caps. These tend to leak with age, and while its not a real common failure, it causes nasty corrosion on the occasion that it happens. THeres only 6 of them, and they are inexpensive. At this point I usually relocate any "post production mods" (those little hand-wired "fixes" youll see on some boards) to the back side of the board, using insulated 30ga kynar wire. I also add the extra adress line on the solder-side if Im planning on ram-expanding the machine. Next, I clean the board with solvent to remove any soldering flux, and re-install all the chips, including new (decent quality) RAM DIPs. I currently have 2 machines that I've done this way over the years, and they have not had a single "flake-out" since either was done. Both were "basket cases" when I got them (rather cheaply) from people who were totally disgusted with the problems and went to XLs.
Edited by MEtalGuy66, Mon Mar 27, 2006 12:42 AM.
0
