+-^CrossBow^- Posted April 6, 2014 Share Posted April 6, 2014 Yes this is the opposite of what you normally hear about. I have a 7800 that I acquired sometime ago I'm just now getting around to testing. Soon as you plug the AC plug into it it powers on? Thinking the button was the culprit I replaced the power switch with a new one and still the same results? I've heard of them not wanting to power on because of bad power switches, but this is the first I've heard of one staying on as soon as AC is applied to it. Any ideas on what would cause this? Thanks. Quote Link to comment Share on other sites More sharing options...
rhcocker Posted April 6, 2014 Share Posted April 6, 2014 I had the same problem. Was it modded or opened? Quote Link to comment Share on other sites More sharing options...
+-^CrossBow^- Posted April 6, 2014 Author Share Posted April 6, 2014 Nope. But is a very late model 7800. The shielding is grey in color and not the usual shiny sheet tin I'm used to seeing on them. The switch I took off it must have been good but I'm really curious what is causing this one to be powered on as soon as you plug in the AC? Guess I need to look for shorts between the pins off the 7805 or something. Quote Link to comment Share on other sites More sharing options...
rhcocker Posted April 6, 2014 Share Posted April 6, 2014 I modded my 7800 with s-video and when I put it together, I had this same issue. I fixed it simply by carefully re-seating my motherboard in it's natural position. I can only assume that the pressure of the case screws had shorted something. Personally, I would try lifting the motherboard out and carefully testing the switch with its guts out. Quote Link to comment Share on other sites More sharing options...
+-^CrossBow^- Posted April 6, 2014 Author Share Posted April 6, 2014 I've been doing this with no luck. It is just stuck in the on position. i read elsewhere this can happen if the voltage regulator is shorted and while looking at it, it appears that the voltage regulator has been replaced on this 7800 in its past. I'm going to next take the switch completely out and see if anything changes. That will at least tell me if the issue is at the voltage regulator or elsewhere along the board. Quote Link to comment Share on other sites More sharing options...
+-^CrossBow^- Posted April 6, 2014 Author Share Posted April 6, 2014 Well removing the switch has zero effect. the 7800 without a power switch is powered on as soon as you plug in the AC. However, I did just notice something that didn't look right at all. C59 not too far from the power plug section looks to be burned to a crisp?! Is that an actual capacitor as the C letterings usually indicate or is it a diode or something else? Time to see if I can figure it out on the schematics... Quote Link to comment Share on other sites More sharing options...
CPUWIZ Posted April 6, 2014 Share Posted April 6, 2014 C59 is an electrolytic cap (.22uF). Quote Link to comment Share on other sites More sharing options...
+-^CrossBow^- Posted April 6, 2014 Author Share Posted April 6, 2014 Yeah...I took another .22 off my old 5200 main board that is a parts board and put that in C59s place. No change, the 7800 still powers on as soon as you plug in the AC cord. Keep in mind I still don't have a power switch even installed on it? Doesn't matter if there is a cart in it or not either. Any one else know a common place I should look as to where this is caused from? Quote Link to comment Share on other sites More sharing options...
Brian R. Posted April 6, 2014 Share Posted April 6, 2014 (edited) 7800 says: Keep playing with me... forever and ever and ever and ever... Now, if you unplug it and it stays powered on, then get worried... Edited April 6, 2014 by Brian R. 5 Quote Link to comment Share on other sites More sharing options...
CPUWIZ Posted April 6, 2014 Share Posted April 6, 2014 Now, if you unplug it and it stays powered on, then get worried... Quote Link to comment Share on other sites More sharing options...
+-^CrossBow^- Posted April 7, 2014 Author Share Posted April 7, 2014 I guess it was a mistake to assume I might be able to get some assistance here? Thanks anyway. 1 Quote Link to comment Share on other sites More sharing options...
+LS650 Posted April 7, 2014 Share Posted April 7, 2014 Several people did offer suggestions. One guy made a very mild, light-hearted joke. 2 Quote Link to comment Share on other sites More sharing options...
Jinks Posted April 8, 2014 Share Posted April 8, 2014 Install a switch on your power cord. Problem solved.. maybe the clapper could help?? http://www.amazon.ca/gp/aw/d/B0000CGKLR Quote Link to comment Share on other sites More sharing options...
ApolloBoy Posted April 8, 2014 Share Posted April 8, 2014 Try replacing the 4013 chip near the power jack and filter cap. Quote Link to comment Share on other sites More sharing options...
+-^CrossBow^- Posted April 8, 2014 Author Share Posted April 8, 2014 (edited) Excellent! Thank you Apolloboy. Looks to be similar to the same flip-flop IC used on the 5200 for the same purpose. Interesting... Update: Changing out the 4013 didn't change anything. I'm thinking it is either a short some where I can't see, or maybe one of the transistors near that IC has gone bad. The IC I used was working correctly to power a 5200 on and off and I looked up the pinouts on the two and they are the same so looks like the 4013 is good. I apologize earlier but this 7800 has been very frustrating to me as it seems to work perfectly fine otherwise aside from the fact it won't power off when you plug it in. I'm almost tempted to just just wire a switch in the circuit somewhere to kill it manually but it seems like this should be something simple? Edited April 8, 2014 by -^Cro§Bow^- Quote Link to comment Share on other sites More sharing options...
Jinks Posted April 8, 2014 Share Posted April 8, 2014 . I'm almost tempted to just just wire a switch in the circuit somewhere to kill it manually but it seems like this should be something simple? See yer gonna go with my clapper idea.. Thank me later!! Quote Link to comment Share on other sites More sharing options...
+Stephen Moss Posted April 8, 2014 Share Posted April 8, 2014 Excellent! Thank you Apolloboy. Looks to be similar to the same flip-flop IC used on the 5200 for the same purpose. Interesting... Update: Changing out the 4013 didn't change anything. I'm thinking it is either a short some where I can't see, or maybe one of the transistors near that IC has gone bad. The IC I used was working correctly to power a 5200 on and off and I looked up the pinouts on the two and they are the same so looks like the 4013 is good. I apologize earlier but this 7800 has been very frustrating to me as it seems to work perfectly fine otherwise aside from the fact it won't power off when you plug it in. I'm almost tempted to just just wire a switch in the circuit somewhere to kill it manually but it seems like this should be something simple? Looking at the circuit diagram the two most obvious possibilities, considering that you have already changed the switch and 4013, are either... 1) Transistor Q9 or Q10 is short circuit or 2) The 4013 is permanently held in it's set mode either because C55 is open circuit and so it is not getting the reset pulse on pin 4 or pin 6 (Set) is open circuit and floating high instead of being permanently tied to 0V as it should be. If you have access to a DVM to measure voltages/resistances on the PCB start by measuring the voltage at pins 1, 4, 6 and 14 of the 4013. If the circuit is operating normally I would expect to see about 5V DC on Pin 14 and 0V on the other three as the static condition, you may see a brief change in voltage on pin 4 when you connect the power for the Reset pulse, however you may not due to the response time of the DVM, you really need an Oscilloscope to view the reset pulse. With the power disconnected measure the resistance between the Emitter and Collector pins of Q9 ( http://www.fairchildsemi.com/ds/2N/2N3904.pdf ) and Q10 ( http://www.fairchildsemi.com/ds/MJ/MJE210.pdf ) 1 Quote Link to comment Share on other sites More sharing options...
+-^CrossBow^- Posted April 9, 2014 Author Share Posted April 9, 2014 Looking at the circuit diagram the two most obvious possibilities, considering that you have already changed the switch and 4013, are either... 1) Transistor Q9 or Q10 is short circuit or 2) The 4013 is permanently held in it's set mode either because C55 is open circuit and so it is not getting the reset pulse on pin 4 or pin 6 (Set) is open circuit and floating high instead of being permanently tied to 0V as it should be. If you have access to a DVM to measure voltages/resistances on the PCB start by measuring the voltage at pins 1, 4, 6 and 14 of the 4013. If the circuit is operating normally I would expect to see about 5V DC on Pin 14 and 0V on the other three as the static condition, you may see a brief change in voltage on pin 4 when you connect the power for the Reset pulse, however you may not due to the response time of the DVM, you really need an Oscilloscope to view the reset pulse. With the power disconnected measure the resistance between the Emitter and Collector pins of Q9 ( http://www.fairchildsemi.com/ds/2N/2N3904.pdf ) and Q10 ( http://www.fairchildsemi.com/ds/MJ/MJE210.pdf ) Thank you Mr. Moss! It was indeed the MJE210. I forgot to mention this before, but I actually took the 4013 and the 14pin socket off the 5200 board and soldered it directly to the 7800 board to make it easier to replace in the future if needed. Now, the 4013 didn't fix it, but something else odd I noticed. With the 4013 removed, the 7800 still powered on as soon as you connected the AC cord. Thinking about this and what Stephen stated, I figured the 210 was at fault. it would also explain why the .22uf cap near it was toasted. So again having my 5200 4 port parts board near by, there are in fact two MJE210s next to the 5200 power switch and RF power cord section. Took one off, replaced the one on the 7800 and immediately it would no longer power up when plugged in since I had the 4013 still off it. Plugged the 4013 back in and this 7800 now powers on and off like it should! So thank you again! 1 Quote Link to comment Share on other sites More sharing options...
+Stephen Moss Posted April 9, 2014 Share Posted April 9, 2014 Glad to help, at least it only took one post to do it. The last power problem I helped resolve (Jaguar) time took about 6 lengthier posts so I am writing a guide on how to check it to save me doing it again. Perhaps I should write one for the 7800 as well. Quote Link to comment Share on other sites More sharing options...
ApolloBoy Posted April 9, 2014 Share Posted April 9, 2014 Surprised I didn't think about that transistor before. The 4013 actually receives power even if the system is shut off, and the MJE210 transistor passes down the incoming voltage to the 7805. It'd really be nice if GCC used a pushbutton switch as opposed to a momentary switch so the 4013 and extra components wouldn't be necessary. Quote Link to comment Share on other sites More sharing options...
7800 Posted April 9, 2014 Share Posted April 9, 2014 Nice to see that this got resolved. I know I would have gone with some kind of inline switch to solve the problem... but that's because I'm not tech savvy enough. lol! Quote Link to comment Share on other sites More sharing options...
+Stephen Moss Posted April 10, 2014 Share Posted April 10, 2014 Surprised I didn't think about that transistor before. The 4013 actually receives power even if the system is shut off, and the MJE210 transistor passes down the incoming voltage to the 7805. It'd really be nice if GCC used a pushbutton switch as opposed to a momentary switch so the 4013 and extra components wouldn't be necessary. The could have used a switch however some devices can start up in random states/containing random data which my have undesirable effects on system operation. Hence the circuit used in which the second D-type in the 4013 holds the Reset pin of the other device active for a short period after the main power is active thus both ensuring a know starting state of various devices at system start and allowing the main power voltage to stabilised before running any code commences. Quote Link to comment Share on other sites More sharing options...
alortegac Posted December 13, 2015 Share Posted December 13, 2015 (edited) I have a similar situation with a 7800 that will not turn on...it was working and then it shut itself off and could not be restarted again....... By following other discussions, I replaced 7805, MJE210, Zenner diode, R53 and power button. After changing the zenner, I only made the console to turn on for a little while and then it shut itself off again. However, I was not able to get any 2600 game to display correctly, only 7800 games would start up sometimes. I thought maybe the new 7805 was not good, so I put the original one back. Well, now the strangest thing has happened, I connected it to the power and try to turn it on, an electronic smell, not burnt just a bit of smell....and BOOM! It working, I tested it for hours....and does work all functions all games,,7800's and 2600's.....BUT IT WILL NEVER POWER OFF. I replaced the power button again....and nothing. I have to unplug it to change games or re-start. From what I am reading above, perhaps MJE210 is open circuit(it got damaged again)...or 4013 is bad, or C55. I am lost now..... I am thinking to install an on/off switch, and be done with it,.....but I want to know what might have happed. Any help is welcome! Edited December 13, 2015 by alortegac Quote Link to comment Share on other sites More sharing options...
+-^CrossBow^- Posted December 14, 2015 Author Share Posted December 14, 2015 Try replacing the c55 cap as that most likely took a hit from whatever power issues were going on there. Also MJE210 likely needs to be replaced again. Quote Link to comment Share on other sites More sharing options...
+Stephen Moss Posted December 14, 2015 Share Posted December 14, 2015 You say it does not power off but does do you need to press the power switch to it on or does it come on as soon as the power is applied? If the latter then the MJE210 had probably died, did you insert the replacement components the correct way around? If you do need to press the power switch to turn it on then I suggest you go back to my post in the won't turn of thread ( http://atariage.com/forums/topic/163769-my-7800-wont-power-on/?do=findComment&comment=3009271) which I see you have also posted to and check the output of the on/off latch (Pin1 , 4013) is giving the correct output and changing states correctly as you press the power button to turn the unit on and off. You can change C55 if you want however I don't think that should prevent the 7800 from turning off as to me its purpose appears to be the ensure the 4013 is reset to the default "unit off" state when power is applied. Quote Link to comment Share on other sites More sharing options...
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