7800 won't power off?!

[alortegac]

Thank you both for your responses. Let me start with Crossbow, can you tell me which Capacitor I should buy? I checked and there several capacitors 0.22 uf ceramic axial options, what are the specs of C55?

 

Stephen, It starts up immediately when I connect it the power source. The power button does not respond at all, ON or OFF.

 

Just to be more specific in my process:

The problem: The console was running and suddenly died.

 

The first thing I did, was replacing the 7805, that did not correct the problem.

 

Then I change the zenner and checked R53 was ok. I made the console work for a brief moment but not properly, I was not able to run any 2600 games and some 7800 would run the start up and the crash. Then the console would just shut itself off.

 

So I then change the zenner for a new one again, and changed Q9. Result: it only run for a little bit with problems and then died again.

 

Then I changed MJE210. Result: it only run for a little bit with the same problems and then died again. ( I have to admit, I am unsure I installed this one correctly, I tried to follow the schematics, but 50 / 50 change of error here). Even when bypassing MJE210, the console would turn on but with the same problems running games.

 

Then I change the power button for the first time. and nothing, still dead.

 

Then I decided to go back to the original 7805. and replaced all components again, including a new Q9, zenner and a new MJE210.

 

Then BOOM! moment and smell, I think I might blew up the MJE210 while probing it.

 

I replaced the button again, to make sure.

 

Now is RUNNING GREAT, but cannot power it off or on using the button. But all games run great, video/sound/functions are ok, including, pause, reset and select..

 

 

Thanks for your help!!!

[+Stephen Moss]

Typically for a unit that is on at power on and cannot be turned off the MJE210 would be primary suspect, just ensure you connect it the correct way around, Emitter (e) to the unregulated +9v/R55, Collector (c ) to the 7805 and the Base (b) to R56. The data sheet for the device ( https://www.fairchildsemi.com/datasheets/MJ/MJE210.pdf) will indicate which pin in which.

 

If you are not certain which hole on the PCB is which you can either trace the connections visually or do a continuity test with a multimeter/DVM (power off) to the points mentioned, alternatively if you do not have access to a multimeter you could build yourself a simple logic probe from a 390 Ohm resistor connected to the two standard 5mm LED (not low current type) connected in parallel, but in opposite directions (polarity independent), using that the hole that is 9V will brightly light the LED, while anything at 5V will light it at a medium brightness, the Base hole should dimly illuminate the LED and it should not illuminate at all at 0V (Collector).

 

If a new, correctly inserted MJE210 does not resolve the problem than as I said on earlier posts you need to check the on/of latching circuit comprised of U10 (4013) and associate components as either the output of that circuit being permanently high or Q9 shorted are the other most likely causes. Once all those have been eliminated can you consider other possible causes.

[alortegac]

Ok, I will check with a multimeter to make sure, and replace the MJE210 again (I have the same exact part from Fairchild). I replaced Q9 once already, but I can do it again. I would like to know how to measure 4013 the right way, I mean where to place the multimeter terminals on the board. Perhaps I am not measuring things correctly there. BTW, I could not get to the on/off latching circuit using the link on your previous post.

 

In another question, about C55. Do you know what I should buy?

 

Thank you for your help!

[Dauber]

Just my two cents...

 

If my 7800 refuses to turn off, I take it as a sign that I need to keep playing it.

[alortegac]

_{Dauber, I did not think about that possibility before, thanks!! I must agree with you, signs come in many different ways.......but sometimes we just do not listen to them. I am very frustrated with this console.....but my friends from this forum will help me I am sure.}

Edited December 15, 2015 by alortegac

[+Stephen Moss]

Not sure why the schematic link did not work, try http://atariage.com/7800/archives/schematics_pal/

If that does not work go to the AA home page, from the menu on the left hand side click on 7800 (under systems), then on Archives, then Atari 7800 Schematics from the main page area, does not matter if you select pal or NTSC as the power stages are identical, then you want the view of the "upper left corner".

 

For measurement connect the Ground/COM lead of you multi-meter to 0V, the easiest place to pick that up will be the metal tab of the 7805, as with all DIL semiconductor ICs there should be either a circular indent near one corner or a semicircular cut out in the center of one end (occasionally you get both), Pin 1 is located to the left of that and pins are numbers sequentially in an anticlockwise direction so Pin 1 = Top left, Pin 7 = bottom left, Pin 8 = bottom right and Pin 14 = top right.

 

As for the capacitor without seeing an original I cannot be certain you will get an exact replacement from the circuit diagram it looks like a 22uF, if so it would either be an electrolytic (cylindrical) or Tantalum (sort of pear shaped) however as it is not shown as being polarised an 0.22uF (220nF) would seen more likely in which case multilayer ceramic should suffice,

As I said previously I highly doubt that is the cause of the problem as if C55 was shorted I would expect you not to be able to turn the unit on and with C55 open or missing completely I would expect you to be able to switch the unit on and off - it would just start in the on condition at power on instead of the off condition.

[alortegac]

Thanks Stephen. I found this C55 on ebay. (I just want to have them just in case, as there is no Radio Shack around here anymore)

 

http://www.ebay.com/itm/50pc-22uF-224-50V-20-Z5U-Axial-Capacitor-Ceramic-MLCC-KEMET-C410C224M5U5CA-/381218294136?hash=item58c2618978:g:5K0AAOSwpDdVIxik

 

I will replace MJE210 and Q9 and do the measurements this Saturday and report back. Should I replace the zenner again too?

 

Before I do all that, one more question: Will it be too bad if I just bypass all this circuit with a On/Off switch on the AC power points? I can do the power supply mod to a 2.1 MM round jack (to replace the original proprietary jack) and take the power from there to a On/Off Switch that I can install ion the side of console without affecting its looks that much.

 

I am afraid if it is the 4013. I am not very experienced replacing chips. I do not know if I could find an original 4013.

 

thanks a lot for your help..

[+Stephen Moss]

There is no point replacing the Zenner if it is working, if you have it in the wrong way round you will be dropping around 8 volts across R53 leave only around a volt for the supply to the 4013, if it is the correct way round and operating as it should then will be dropping around 4 volts across R53 and the 4013 will have a supply of around 5V.

 

You could bypass the whole on/off circuitry with a switch if you want, I guess it depends on if you think it is more or less work than getting it back operating correctly and how bothered you are with keeping the unit as original as possible. You could modify it as you suggested but the easiest way to fit a switch that would bypass the on/off circuitry is to just to remove the MJE210 and wire the switch in to the points where its Emitter and Collector connections are.

 

You should be able to find a 4013 reasonable easily, if it is in a socket it should be easy to replace, if it is soldered it is a little more difficult but should still be manageable.

[alortegac]

Zenner is in the correct way, with the darker band in the same direction of the original, I was just saying in case it could have gotten damaged when the smell occurred, I will leave it alone as you suggested.

 

Aside from my concern about being able to replace 4013 without damaging it or more or less work, I was asking about the on/off bypass because I read that this 4013 circuit resets the system so that the programs start up properly, so bypassing it may cause other issues. I have not seen those issues happening, so I was not sure.

 

I will search for the CD4013 on ebay or such. I will let you know. Is there any difference in the CD4013B, or it is the same?

 

Another thing that still bothers me is why the console was not working properly when I made it work the last time before the BOOM moment? Or it is something else in the circuit that can affect the function of the whole console. If you recalled, after replacing the zenner the first time around (before touching the MJE210/Q9), the console turned on and I was able to make few games to startup (none 2600's on 7800's and getting garbage). However, after a short period of time the console would die again. This happened twice with the new and the original 7805. But not now, the console works great, so I am ruling out the big capacitor, 7805, MJE210 (when I replace it again, I expect the same issue), Q9(when I replace it again), R53, zenner and new switch.

 

 

thanks a lot!!

Edited December 17, 2015 by alortegac

[+Stephen Moss]

Obviously the zenner would need replacing if it is defective, I was only indicating that it would be pointless doing so it if that were not the case.

 

The only real way of getting to the bottom of the problem is to measure voltages/checking logic levels, if you are not going to do that you are just wasting time.

You may get lucky by blindly changing parts but you could be changing components you don't need to and it may only result in a temporary fix because if the same part keeps failing you need to identify the cause in order to implement a permeant cure, additionally repeated soldering/de-soldering of the same part of a PCB will eventually lead to problems with tracks and pads coming away from the board.

 

Any 14 pin Dual D-Type Flip Flop logic device with the number 4013 should be the same both in regard to operation and pin compatibility, the letters before and after vary by manufacturer and can be used to identify things like the manufacture, what material the external packaging material is, if it is lead free and the package type.

As long you make sure you get a through hole (DIP/DIL) type where the pins extend below the body of the device and not a surface mount type where the pins are bent parallel to and level with the bottom of the body you should be ok and if it is not already in a socket you may want to consider soldering a socket to the PCB as it will make it easier to replace again if you have to.

 

As for bypassing the circuit entirely, yes you will have to account for the reset. I forgot to mention that before as I more concerned with suggesting a better method to the power mod than you were suggesting, although replacing the original power connector with something more standard would make obtaining replacement power units easier but then the same thing could be achieved but cutting the original power connector off with a little extra cord and wire it to a 2.1mm free (cable mount) socket to create a plug in interface cable if you wanted to keep the original connector.

 

If you are bypassing the startup circuit you should use a double pole double throw (DPDT) switch, these have two rows of three connections.

Row 1 (Power):- connect the centre pin/tag (Pole) to the PCB hole where the MJE210 Collector (connected to the 7805) goes and one of the other pins (Throw) to the PCB hole where the Emitter (has arrow in schematic) of MJE210 goes, this replaces the MJE210 as I previously described.

Row 2 (Reset):- connect the centre pin/tag (Pole) to the PCB hole where pin 13 of the 4013 would be (best to remove the 4013 or at least cut pin 13 off and remove that), connect the throw at the same end you used for the Emitter connection on row 1 to the hole for pin 8 of the 4013 (again remove pin) and the other throw to 0V (pick up from the GND pin of the 7805).

 

I usually hole up and unplug for a couple of weeks over Christmas and new year so do not be surprise if I do not reply to any further post until the new year.

[alortegac]

Stephen, Once again thank you for all you insight, Thanks for teaching me. I will follow due process and report back result. In the meantime, I wish you the best for this Holiday season.

[alortegac]

Stephen, here some measurements.

 

Console that would not turned Off (ON STATE):

 

7805: : Output: 4.81v G: 0v : Input:6.61v

MJE210: E: 10.35v C:6.74v B:7.24v

R56: 7.24v

Q9: E:0v B:0v C:8.79v

R56: 8.79v

Zenner: Cathode: 4.97v Anode: 0v

R53: 10.35 to 4.97v

S1: 4.95v,0v,0v,4.95v

R55: 10.35v

4013: PIN 1: 0v ; PIN 14: 4.96v

 

THEN I replaced MJE210 and Q9 as we discussed, the console is dead again:;

Measurements (OFF STATE):

7805: Input:0v; G:0v; Output: 0v

MJE210: E:13.2v; C: 0v B: 13.20v

Q9: E:0v B:0v C:13.2v

S1: 4.00v,0,0,4.99v

4013: PIN 1: 0v, PIN 14: 4.99v

R56: 13.20v

Zenner: Cathode: 4.99v Anode: 0v

 

 

I was able to take measurements on second WORKING 7800 console, these are the readings for comparison:

 

ON STATE

7805: Input: 10.41, G:0v Output: 4.91v

MJE210: E: 10.57v C: 10.46v B: 9.81v

Q9: E:4.90 B: 6.22v C:0v

S1: 4.63v,0,0,4.63v

4013: PIN 1: 4.50v PIN 14: 4.63v

Zenner: Cathode: 4.63v Anode: 0v

 

OFF STATE:

7805: I nput: 0v G:0v Ouput:0v

MJE210: E: 13.11v C: 0v B:13.11v

4103: PIN 1: 0v PIN 14: 4.70v

Q9: E: 0v B:0v C: 13.2V

 

 

Thanks!

Edited December 24, 2015 by alortegac

[+Stephen Moss]

I think there are some typo's in regard to the measurements from the working console, specifically the voltage you have ascribed to the pins of Q9, but compensating for that all the voltage appear to be correct except possibly the Base of the MJE210/Collector of Q9 which I would have expected to be lower as the base of the MJE210 is barely low enough for it to turn on, but then it has been a long time since I was taught transistor theory so I may have forgotten something.

 

The voltages for the not turning off Console (On State) are generally what I would expect, the Zenner appears to be operating correctly and the output of the 4013 first stage of the on/off latch is in the default "Off" State as it should be. The voltages at the input to the regulator and possible those at the Base of the MJE210/Collector voltage of Q9 seem a little off and there seems to be a lot of voltage dropped across the MJE210. If the MJE210 had blown as the result of being inserted the wrong way that could explain those voltages.

Depending on the manufacture the case type used for the MJE210 sometimes has a metallic patch on one side, that patch is on the rear of the MJE210, the pin diagram on data sheet shows the device from the front.

 

Regarding the measurements having changed the MJE210 and Q9 (Dead Console) and allowing for a probably typo on one of the S1 voltages they are all as I would expect. So if the 7800 is still in this conditions lets take this as our starting point for tracing the problem.

 

The On/Off circuit can be broken down into three sections, On/Off latch, Reset Latch, and the power switching, the first thing to check is the On/Off latching, a High logic state is 2.7 - 5V DC, a Low Logic state is 0 - 0.4V DC.

 

The logic states for the 4013 On/Off latch default "off" condition at main power on (not S1 controlled console power on) should be...

Pin 1: Low

Pin 2: High

Pin 3: High

Pin 4: Low

Pin 5: High

Pin 6: 0V

Pin 7: 0V (Supply Voltage)

Pin 14: 4.7 - 5.2V (Zenner derived "5V" supply voltage)

​​

If the above is correct then Pin 3 should be Low when S1 is pressed and High when it is not, check this is occurring. If this is occurring then every time S1 is pressed the On/Off latch should toggle between its off condition and on condition, in the On condition the Logic states of Pins 1, 2 and 5 should be the opposite of those for the off condition.

In both the On and Off conditions the logic states should be stable until S1 is pressed to change the On/Off condition of the latch, if all appears well we can look at the other stages, if not report what is different.

 

 

 

[alortegac]

Hello Stephen, Happy new Year.

 

Thanks for your response.

 

Comments:

About MJE210 in the "On" State console, definitely I blew the MJE210 by shortening it or something while probing to measure, this was the action that left the console in "ON STATE". However, a new MJE210 is inserted in the correct way now. I checked the datasheet several times. This is the link to the data sheet. https://www.fairchildsemi.com/datasheets/MJ/MJE210.pdf

 

I will check the latch circuit per your instructions and report back. However, I will be able to get to it until the weekend, thanks for your patience and assistance.

 

Alberto

[alortegac]

Stephen,

This is my report:

 

The logic states for the 4013 On/Off latch default "off" condition at main power on (not S1 controlled console power on) is

 

7805: Input:0v; G:0v; Output: 0v

MJE210: E:13.2v; C: 0v B: 13.20v

Q9: E:0v B:0v C:13.2v

S1: 0.00v,0,0,0v (NOTE I DO NOT HAVE 4.99V anymore???)

 

 

Pin 1: = 26.5 mV

Pin 2: = 54 mV

Pin 3: = -14 mV

Pin 4: Low = 0V

Pin 5: = 0V

Pin 6: 0V = 0V

Pin 7: 0V (Supply Voltage) = 0V

Pin 14 = 2.5 mV

​​

I think R53 is open circuit because I am getting continuity when I test it. I am getting 0 to intermittent OHM readings from it.??

 

Any ideas?

 

Thanks for your help!!

Edited January 16, 2016 by alortegac

[+Stephen Moss]

The voltages for the 7805, MJE210 and Q9 all look good.

 

The voltages S1 and the 4013 are all around 0 and they should not be, the fact that you are no longer getting around 5V on both Pin 14 or S1 would suggest the problem probably lies with an open circuit R53 and/or short circuit Zenner.

If the Zenner is short circuit you should find all the supply voltage (13V) being dropped across R53 when you measure the voltage across it (one meter lead on each end) as opposed to the 7 or 8 volts you should normally get. However, if the R53 is a normal 0.25W resistor a short circuit Zenner would result in 0.5W of power going through R53 which would cook possibly resulting in it being open circuit and subsequent reading of 0V.

 

If R3 is not looking at little cooked try re-soldering the joints incase it is just a bad connection, if you are still not getting the expected voltages then measure the voltage drop across R53, if 13V try replacing the Zenner, if 0V remove R53 and measure its resistance which from the circuit diagram looks like it should be around 310 ohms (don't make contact with the metal parts of the probes or resistor as it can effect the reading). If you get an open circuit or very high resistance then replacing it and the Zenner.

[alortegac]

Removed R53 measuring only 511 not 560, OHM; I replaced it

Removed Zenner was blown or shot, measuring 0 v both ways. I replaced it with a new one. Now we are back to 0 - 5.14V

 

SHOULD BE: ACTUAL READING

Pin 1: Low ====== =LOW (MINUS) -1.40 V.

Pin 2: High ======= -10 mV LOW

Pin 3: High ===== =5.14 V

Pin 4: Low ===== 5.08 V HIGH

Pin 5: High ======1.04 mV

Pin 6: 0V === =====0V

Pin 7: 0V (Supply Voltage) ===== 0V

Pin 14: 4.7 - 5.2V (Zenner derived "5V" supply voltage) = ==== 5.14 V

 

Note: I took all the readings without the IC being present as I socketed. I have a fresh 4013 ready to be placed when we find the problem and correct it.. Hope this is alright.

 

 

Thanks for your help!!

Alberto

 

PIN 3 goes to liow when I press S1.

Edited January 19, 2016 by alortegac

[+Stephen Moss]

From the schematic it looked like R53 was 310 Ohm but it could be 510 as 310 seemed an odd value, as the resistors have a 5% tolerance values I think it was ok.

Not quite sure why you get minus voltage with a single end supply, perhaps you has you meter leads the wrong way round.

 

The voltages you are getting now look ok, you will need to insert the 4013 to test further, so try inserting that and see if you are getting the voltages you should get.

[alortegac]

Hi Again, thanks for your follow up.

 

Here are the new readings with the 4013 inserted in position. (The console still does not power up)

 

SHOULD BE: ACTUAL READING

Pin 1: Low ====== 0 volts

Pin 2: High ======= 5.14 V

Pin 3: High ====== 5.14 V

Pin 4: Low ===== 5.08 V

Pin 5: High ====== 4.21 V

Pin 6: 0V === =====0V

Pin 7: 0V (Supply Voltage) ===== 0V

Pin 14: 4.7 - 5.2V (Zenner derived "5V" supply voltage) = ==== 5.14 V

 

PIN 3 goes to LOW when I press S1 == OK

 

The reading that is off is PIN 4.

 

Please advise, Alberto

Edited January 19, 2016 by alortegac

[+Stephen Moss]

I was a little suspicios of pin 4 yesterday as it should be pulled low by R47 but for some reason was doubting myself as R47 is quite high resistance, but I am only running at about 50% at the moment - need sleep.

 

Try resoldering the connections for R47 incase it is a bad joint, if Pin 4 is still high after that then there could be a short circuit in which case the two primary possibilities are either C55 has gone short circuit or as you indicated that you have both changed C55 and put in a socket for the 4013 there could be a short circuit cause by some stray solder that is either shorting C55 or to Pin 4 of the 4013 (between pins 3 & 4 is the most likely option).

So first do a visual check for any solder shorts and remove any you find, if you do not see any or the problem persists after removing any solder shorts use a meter to check for short circuit, although if Pins 3 and 4 of the 4013 are shorted another way of testing for that would be to see if the voltage at Pin 4 goes low when S1 is pressed.

 

 

[Andromeda Stardust]

This is a fascinating discussion. Added to watch list. Carry on...

[alortegac]

Hello Stephen,

Great news to report today.

 

I first proceed with visual inspection of the circuit for shorts, cold joints, my not so good soldering, etc. Everything looked ok!

Then, I removed 1 pin of R47, checked with meter, perfect 1M OMH. I reinserted it.

Finally, I proceed with checking C55 (which I had not replaced yet, as we decided to first check 4013). I removed it, checked with capacitor meter.....NO READING. Check with meter, very low resistance....short!

 

C55 WAS THE CULPRIT

 

I replaced it with another 0.22 UF capacitor I had in my box of components, not quite the same cylindrical ceramic, but the same capacitance. I think a better one.

 

My old 7800 is back from zombie land! and with best picture than ever.

 

As I recap, I replaced S1, MJE210 (2 times), 7805, R53, C55, Zenner diode CR5 (3 times) and 1 4013 (now socketed).

 

I really want to thank you for your help and patience. Many Thanks!!

 

Alberto

 

PS. I still have1 final question for you: How did you know the expected on/off high/low states of 4013? where can I learn how to inspect TIA, 6057 and 6532, etc? I have another light sixer sick console......that now I feel I can try to resuscitate, hopefully with more your help!. Perhaps matter for opening another topic, this console does weird things.....like overlapping images, changing letters in the screen, numbers, etc...weird, weird...stuff.

Edited January 21, 2016 by alortegac

[Andromeda Stardust]

Bravo!

[alortegac]

It was thanks to Stephen!

[+Stephen Moss]

 

I really want to thank you for your help and patience. Many Thanks!!

 

Alberto

 

PS. I still have1 final question for you: How did you know the expected on/off high/low states of 4013? where can I learn how to inspect TIA, 6057 and 6532, etc?

 

We got there in the end.

 

Well having spent a year being taught electronic servicing and over 20 years working with circuits helps but for the layman the devices data sheet is a useful resource if you can understand it. A simple latch such as the 4013 should be reasonably easy to understand.

 

How did I know the expect states of the 4013?

If you look at the schematic then the states of the pins tied to the power rails are obvious enough, Capacitors are short circuit to AC and open circuit to DC although you will get a momentary instantaneous change of state transmitted from one plate to the other with respect to an instantaneous change in DC voltage. That allows C55 & R47 to combine to place a brief 5V signal on pin 4 (Reset) of the 4013 when the main power unit is switched on before it is pulled to 0V by R47 (with C5 shorted the latch was permanently held in Reset).

 

The truth table on the data sheet will indicate the status of the Q (pin 1) and NOT Q (Pin 2) outputs when the device has been reset, the D input at pin 5 is supplied by the NOT Q output and so should be in the same state after a brief delay as C53 is charged/discharged through R45.

 

The voltage on pin 3 is determined by the voltage on C30, as C30 is charged via R45 its voltage rises and after 1.6 x (CxR) it should be fully charged to approximately the same voltage as the Zenner derived 5V supply.

 

As for the TIA, 6057 and 6532 the data sheets may help a little but they are much more difficult to check especially without anything like a test cartridge that can maintain them in a constant/constantly repeating state and a logic analyser to record the states of input/output pins as their input and output states will change depending on the program instruction code being executed at any one time.

Consequently there are only a few pins that can be reliably read even by an experienced person with only access to a game cartridge and a DVM, those largely being supply voltages, controller inputs, Reset pins and possibly the Oscillator inputs.