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slaanesh

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About slaanesh

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  1. Okay well that really would exactly explain the readings I am getting. I'm thinking that both of my power boards are actually fine.
  2. Original power board: Pin 1 has 14V input Pin 3 has 11.96V output New power board: Pin 1 has 14.06V input Pin 3 has 12.5V output
  3. So what I mean is that when the power board isn’t connected to the rest of the computer, the 7805 is measuring about 10V on pin3 output pin. The 7805 is on the outside of the heatsink and pin 3 is on the right hand side. Please correct me if I’m wrong.
  4. So I have a new power board. Before using it I checked my power supply to make sure that it was providing a good constant 9VAC. It's actually providing bang on 10VAC which I thought was probably right to allow for voltage sag under load. So I connected it up and then measured the 7805 and lo and behold... it's way higher than 5V again... like WTF? This is without the board connected to the computer. I mean surely this board couldn't have the same fault as my other board? Or this is actually correct. When the board is NOT connected, that pin is delivering more volts. Maybe it shouldn't actually be powered up without having any load? Anyway, I'd really appreciate if anyone can verify what the voltage on pin3 of the 7805 is under these conditions.
  5. I’ve double and triple checked the mods and am sure they are good with no spillage, bridges or misconnections.
  6. Yes worked perfectly fine before the mod. it still worked intermittently after but I haven’t tried it for a week now as I don’t want to connect the power board to the rest of the computer anymore. i’m hoping the rest isn’t damaged... but I dunno. i have ordered a new power board and it’s on the way.
  7. I have a PAL Atari 7800 and I dislike it immensely. I've found no information or way to mod a PAL 50hz 7800 to output PAL-60. So I've bit the bullet and bought some US NTSC 60hz machines.
  8. Or any other components worth replacing? I'm starting to lose hope with this board ...
  9. The bridge of the top two pins at the 5 vertical pins is just trick of the light - there is no continuity between them. Originally I didn't do any soldering on this board at all, so there shouldn't have been any blobs or tracks. The Atari 400 was working before I performed the mods and disassembled it. Maybe I guess something bent? cracked (reflowing may solved this if I find anything). Are there any sections of the board which I should concentrate on?
  10. I lifted one leg off the CR209 and CR207. Both seem to be correct providing a reduction in voltage one way and not the other. I also put the 7805 back in and can confirm that pin 3 still is providing ~11.5v. So I dunno ... what else can I try? The 7812 seems to be correct... the input is ~27v and the output is ~11.8v. I also measured the old 7805 by connecting it to a 9v input source. It's input was 9.5v and output ~5v, so it's still operational... Something seems to be "leaking" 11.8v on the 7805's pin-3 output somehow... somewhere... The board has brand new caps - they are all smaller than the originals and have been soldered in a different orientation as these were the only ones I could get.
  11. Thanks for your suggestion. I'm not really sure what to try now but willing to learn about what to do here. --------------------------- Okay I've removed the 7805. Without desoldering one of the legs I checked the diodes CR205,6,7,8,9. They all give a voltage drop of around ~700 - I'm assuming this is 700/1000 of a volt or 0.7v Repeat: this is without removing any legs from the board I also checked R202 which is the big 33 ohms resistor and it reads as 33.1. I checked the traces on the board where the 7805 was without powering it up. In continuity/diode mode on my MM, when I connect pin 1 + 2 it reads a voltage drop ticking over until it gets to 2000 whereupon it says "1" - assuming 2.000 volts is the most it will do. The same thing happens whith pins 2 + 3. If I go to resistance mode (is this useful?) and I set it to 20k it just ticks over with increasing resistance... *shrugs* on both 1+2 and 2+3.
  12. I didn't do any work on the power board until after the issue was already happening. At this point all I have done is replace all the caps and the 7805 on the board and the symptoms remain identical. One interesting point is the traces on pin 2 and 3 of the 7805... There seems to be continuity between these two pins. Is that normal? Or would component failure cause this? This continuity seemed to be present before I replaced the 7805.
  13. Thanks for that... I am finding that I have ~11V on lines 5, 6 and 7 on J201... these should be 5V. What could be causing this? I just replace the 7805... surely the new one isn't also broken? Are there any other components that could be causing this? What about R202, that big resistor... IF that was kaput, would that be causing issues? I could successfully measure R203 floating at ~6.73k (suppose to be 6.8k) but couldn't get a reading on R202...
  14. So I'd previously re-seated all the main components that I could on the CPU board. It's a Rev D. so there were 7 chips on it. I cleaned the pins with Isopropyl but not the sockets... how do you clean them? Rub a needle into each pin socket entry? Spray contact cleaner into it? On the power board I measured the voltages on the J201 and I got ~+12V on pin 2 and ~-5V on pin 18. In line with the Atari service guide. The guide didn't say to measure two other pins 6 and 7 which are marked +5a and +5b. But I did measure these, they had about 11v if I recall... is that correct? As for measuring the 7805, I measure both pairs - the input + ground and the output + ground. The input was around 13v or so and the output was as I mentioned earlier close to 12v. And this is a replacement 7805 I just put in. Doesn't make sense...? Yet the above voltages seem to be okay? And just a note, the power board is no longer connected to the main board. The measurements have been made with it removed. I don't have any spare easily accessible components... Well I have a couple Atari 800XLs which work perfectly, one PAL and one NTSC. But if they don't have socketed components then I don't want to mess with them. I think I have to undo the mods.. surely one of these may be the issue? Both are completely reversable... painful as I don't enjoy doing these kind of things.
  15. So I've replaced all the caps on the power board. There doesn't seem to be any difference so I don't think it's the caps I didn't replace 10uF on the motherboard (yet) but I may as well do that for completeness. On first power up it did turn on... and I got the memo notepad. After that just black again. Just to recap, I'm using the Atari UAV video mode and the 48/52K RAM card.
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