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2600 repair advice: 1 bad button input

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I have a nice non-heavy 6 switch 2600 on the bench to fix up. The right joystick has the button input on always. The unit works well otherwise, including the left joystick. Tested using a known working joystick.

 

Should I replace the jack first or is it more likely to be another component that I could replace?

 

 

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First thing I would try, is to reflow the jack.

 

If you have a multimeter, I would check for continuity, on the fire button pin, maybe something inside the connector cracked.

 

Next, schematic, don't have that memorized.

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The pin 6, which seems to be the button, is continuous past three solder points where it goes through to the other side under the cart port. It seems to split into two paths at one point, but i can't really be sure. I thought I could trace it visually to a couple of chips but couldn't figure out where it goes with any certainty. I guess this is why we use schematics. Mind you if I looked at a schematic with the intention of repairing something, this would be the first time. I wish I had more table space.

 

 

First thing I would try, is to reflow the jack.

 

If you have a multimeter, I would check for continuity, on the fire button pin, maybe something inside the connector cracked.

 

Next, schematic, don't have that memorized.

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Ah yes. Thanks. Looks like it goes to pin 35 of the TIA.

 

I couldn't demonstrate continuity of any joystick port pin to the TIA. Whether it was the bad joystick button or the good one. Should I be able to?

 

Could be my meter, which is not terrible, but nothing special. It's the Extech EX330.

 

 

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Sounds like the same issue with my first light sixer, the second controller port was always firing. Turned out to be a bad hex buffer chip.

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Measure voltage between pins 6 & 8 of the controller port (controller disconnected)...

 

If you measure close to 5V then....

CX2600: measure the voltage at pin 7 of the buffer chip, pin 6 of the buffer chip and pin 35 of the TIA, if at any point the 5V turns to something else that will indicate where the problem lies. If you measure 5V all the way then you may have a faulty TIA.

CX2600A: Measure the voltage at pin 35 of the TIA, if you get 5V there then again you may have a faulty TIA.

 

If you measure 0V then...

Measure the voltage between the output (right) pin of the 7805 and pin 6 of the controller port, if you measure 0V then you either have a bad pull-up resistor or a bad solder joint to the resistor/controller port pin. If you measure 5V then switch off and measure the resistance between pins 6 & 8 of the controller port, if you measure near to 0 then the capacitor may be short circuit or you may have a solder short to 0V somewhere. Look for a solder short, if you cannot see one then then try removing the capacitor to see if that solves the problem.

 

 

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Thanks Stephen.

 

I measured 4.5v between pins 6&8 using the AC setting, but the problem is, when I try to measure anything with DC, I get terrible measurements (110mV on the pins you said to check). Even when I measure the output from the power supply, the meter is weird. It measures around 5.5v AC. Shouldn't the output from the PS be 9v DC? Measuring DC just gives me low voltage fluctuating gibberish. Nothing really makes sense with this meter. I'm supposed to be using DC settings to measure voltages on the board, correct?

 

I think it's messed up. I'm going to buy a new meter and then revisit this to make sure I'm not being deceived by a messed up meter. Some measurements make sense with it but most do not.

 

I'll post follow up when I get back to this.

 

My other choice is just to try a new TIA chip and see if that solves the problem. I hate to replace the old AMP chip with a more recent one, but since this isn't a restoration, it may be worth doing anyway. I think I have a Jr. donor board that I harvested for a RIOT recently somewhere that I could use.

 

 

 

 

 

 

Measure voltage between pins 6 & 8 of the controller port (controller disconnected)...

 

If you measure close to 5V then....

CX2600: measure the voltage at pin 7 of the buffer chip, pin 6 of the buffer chip and pin 35 of the TIA, if at any point the 5V turns to something else that will indicate where the problem lies. If you measure 5V all the way then you may have a faulty TIA.

CX2600A: Measure the voltage at pin 35 of the TIA, if you get 5V there then again you may have a faulty TIA.

 

If you measure 0V then...

Measure the voltage between the output (right) pin of the 7805 and pin 6 of the controller port, if you measure 0V then you either have a bad pull-up resistor or a bad solder joint to the resistor/controller port pin. If you measure 5V then switch off and measure the resistance between pins 6 & 8 of the controller port, if you measure near to 0 then the capacitor may be short circuit or you may have a solder short to 0V somewhere. Look for a solder short, if you cannot see one then then try removing the capacitor to see if that solves the problem.

 

 

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Thanks Stephen.

 

I measured 4.5v between pins 6&8 using the AC setting, but the problem is, when I try to measure anything with DC, I get terrible measurements (110mV on the pins you said to check). Even when I measure the output from the power supply, the meter is weird. It measures around 5.5v AC. Shouldn't the output from the PS be 9v DC? Measuring DC just gives me low voltage fluctuating gibberish. Nothing really makes sense with this meter. I'm supposed to be using DC settings to measure voltages on the board, correct?

 

I think it's messed up. I'm going to buy a new meter and then revisit this to make sure I'm not being deceived by a messed up meter. Some measurements make sense with it but most do not.

That is odd, is it possible you were not using the meteer correctly? As it sounds like either the AC and DC ranges are reversed or that your power supply may be outputting AC instead of DC.

 

If like like most modern cheap multi-meters it has a rotary function selector are the AD (~)/DC (Line over dots symbol) voltage ranges are opposite each other? If so, it is possibly the pointer may not be correctly aligned with the switch position or an error in the bezel printing is the causing a possible AC/DC range reversal.

 

There are a couple of ways to check...

1) Check there is no low battery indicator showing as you will get incorrect readings if it is.

2) Set the voltage range to 20 DC (leads in the COM and V sockets) and measure a new or relatively new battery if you have one (preferably PP3 but AA will do).

3) Most digital meters have a buzzer indicated by a speaker or musical note symbol on one of the ranges, try setting it to that and connecting the meter leads together.

 

If you get the correct voltage reading and the buzzer works the the meter is probably fine and the power unit maybe outputting AC which would explain the readings you are getting.

If you measure close to 0 rather than 8-10v on a PP3 and it does not buzz when it should then the pointer may be incorrectly aligned with the switch position or the meter is faulty, however if the buzzer works (pointer correctly aligned) but you do not get a correct battery voltage reading then the the maybe faulty.

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That is odd, is it possible you were not using the meteer correctly? As it sounds like either the AC and DC ranges are reversed or that your power supply may be outputting AC instead of DC.

 

...

 

If you get the correct voltage reading and the buzzer works the the meter is probably fine and the power unit maybe outputting AC which would explain the readings you are getting.

If you measure close to 0 rather than 8-10v on a PP3 and it does not buzz when it should then the pointer may be incorrectly aligned with the switch position or the meter is faulty, however if the buzzer works (pointer correctly aligned) but you do not get a correct battery voltage reading then the the maybe faulty.

 

 

The meter was working inconsistently. I've had it maybe 5 years. I'll try a new one and see. The meter used to make sense. It does measure low voltage stuff like batteries, although inconsistently. When I do higher voltage things using the auto range or setting the appropriate range, it never provides useful information. And DC fluctuates when I do those measurements as well.

 

I have two 9v 500mA power supplies I was using for testing 2600s. Both output the same using my funky meter. Both work to power up a console. I don't think the power supply is the issue. Of course, anything is possible.

 

Thanks again for your thoughts. I'll post more as I make progress.

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Like Banquo said above, I’ve had this happen on a few 6 switchers and it’s likely the hex buffer (CD4050) that’s failed. There was a workaround that you can use to verify and you could leave it like that or just replace the chip.

 

 

Sent from my iPhone using Tapatalk

Edited by jc13
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Measure voltage between pins 6 & 8 of the controller port (controller disconnected)...

 

If you measure close to 5V then....

 

So I did get nearly 5V from the pin 6-8 connection.

 

I did not get 5V from any of the other pins on the hex buffer chip or TIA. I got an order of magnitude less or worse. Should my first move be replacing the buffer chip? Is that an easy find? It's not socketed, but it shouldn't be a big deal for me to put a socket in and replace it.

 

I was not able to find my spare 2600 jr board for parts, I just need to order parts.

 

I did get a new meter that provides more stable output.

 

Thanks again.

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So I did get nearly 5V from the pin 6-8 connection.

 

I did not get 5V from any of the other pins on the hex buffer chip or TIA. I got an order of magnitude less or worse. Should my first move be replacing the buffer chip? Is that an easy find? It's not socketed, but it shouldn't be a big deal for me to put a socket in and replace it.

If you are getting 5V at the connector that indicates to me that the connection the the pull-up resistors is fine and that both the capacitor and input to the buffer are not shorted to ground.

Consequently you should also be getting 5V at the buffer input, the fact that you have 0.5V everywhere else suggests to me that the buffer and TIA are probably fine and that you have have a bad connection (solder joint/cracked PCB track) between the controller socket and the input to the buffer.

There are two way of trying to confirm this, one is to perform a continuity check between the controller socket and the buffer input (Pin 7), the other is to use a piece of wire or a reistor (1-10K in value) and hold it in place connecting pins 1 (5V) and 7 of the buffer together, if the fire button on issue goes away then the buffer & TIA would seem to be operating correctly again pointing to an bad connection between the controller port and the buffer input.

 

I doubt that shorting the input pin of the buffer to the output pin and bypassing the buffer as jc13 suggested would solve the problem as you indicated you have 0.5V going in not 5V but feel free to try it.

Edited by Stephen Moss
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There are two way of trying to confirm this, one is to perform a continuity check between the controller socket and the buffer input (Pin 7), the other is to use a piece of wire or a reistor (1-10K in value) and hold it in place connecting pins 1 (5V) and 7 of the buffer together, if the fire button on issue goes away then the buffer & TIA would seem to be operating correctly again pointing to an bad connection between the controller port and the buffer input.

 

 

 

There is continuity between pin 6 of the right controller port and pin 7 of the hex buffer chip. I went back and measured voltage on pin 6 & 7 of the hex buffer chip (with my new meter), and they read 0.5v and 0.0v respectively. I'm thinking that I should replace the hex buffer chip.

 

It's funny, I saved some cutout pages I got in a lot from Electronic Servicing and Technology magazine (January 1983 p50) and I stumbled upon them while cleaning up. For "Continuous or no joystick firing" they recommend replace either the Hex Buffer chip or the joystick ports, which is in agreement with what you've been helping me diagnose.

 

And while I have you, which capacitors should I routinely replace on these boards? This is a Rev B C010433 board for a six switch, which I believe is a CX2600 not a CX2600A. I thought CX2600A's were alwaysl 4 switches, like with Vader cases.

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There is continuity between pin 6 of the right controller port and pin 7 of the hex buffer chip. I went back and measured voltage on pin 6 & 7 of the hex buffer chip (with my new meter), and they read 0.5v and 0.0v respectively. I'm thinking that I should replace the hex buffer chip.

 

It does not make sense to me, if there is continuity between them they should be at the same voltage, but you indicated that the voltage was 5V at the controller port and 0.5V at the buffer input. Whether the buffer IC is good or bad both point should be connected and thus at the same voltage unless either you are measuring the wrong points or the the physical pressure/conduction of the probe tip was restoring a bad connection during the measurement.

 

By all means replace the buffer if you want but from the information you have provided I am not convinced that is the problem, f you can try the pin 1 to pin 7 bridge I mentioned in my previous post. that will put 5V on the buffer input which should result in 5V out and into the TIA if both the buffer and TIA are powered and operating correctly.

If you do decide to just change the buffer and see what happens then before inserting the new one try shorting buffer pins 6 & 7 and check you are getting 5V at TIA pin 35 (remeber to remove the short afterwards).

 

And while I have you, which capacitors should I routinely replace on these boards? This is a Rev B C010433 board for a six switch, which I believe is a CX2600 not a CX2600A. I thought CX2600A's were alwaysl 4 switches, like with Vader cases.

Capacitors should not need routinely replacing, while it is true that the electrolyte in electrolytic capacitors can go a bit funny if they are unused for 10 years+ they can be reformed with use. If you really want to replace capacitors then I would only replace the electrolytic ones, they are easy to spot as the look like cans/cylinders metal cap one end and plastic at the other.

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It does not make sense to me,

 

 

 

I'd like to thank everyone for their help. The continuous fire problem was solved by replacing the hex buffer with a hex buffer from a donor Jr. that I had lying around. I put in a socket just in case. I love resurrecting old hardware and this was a satisfying result. And the process was good fun. Thanks for the information.

 

I sometimes worry about the future of hardware repair as knowledgeable people die off, especially for the more obscure systems and problems. There should always be a good number of people to help fix 2600s, but weirder old computers and even mainframes will become more and more difficult to troubleshoot.

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I have a nice non-heavy 6 switch 2600 on the bench to fix up. The right joystick has the button input on always. The unit works well otherwise, including the left joystick. Tested using a known working joystick.

 

Should I replace the jack first or is it more likely to be another component that I could replace?

 

 

Best thing I could say is open the stick up and see if all 6 wire clips are facing the right direction and make sure 2 of them might not be on a single tab, I got in a stick once that had this on the PCB, and I had to flip the wire around so 2 clips were not on a SINGLE tab

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