7 replies to this topic

[thegoldenband]

I'm testing a couple dead AC adapters for the VCS right now (part numbers #CO16353 and #CO16353-101), and had a few questions:

1) If my multimeter (a Radio Shack Micronta 22-202A) is set to measure resistance, and I touch both prongs (across the wall wart itself) and get no movement of the needle, that means the transformer has failed and the adapter is toast, right? Just confirming that I'm correctly understanding the guide I'm reading (written by the excellent Ray Carlsen).

1a) Should I throw these out, or can some part of them be salvaged? The cable might be good for all I know. I don't plan to salvage them myself, but if someone else is able...

2) When I tested my good adapter, it did show continuity, but I was a little surprised by one thing. When I set the ohms range switch to RX1K (meaning a multiplier of 1000), and test across the prongs of the wall wart, the needle is pegged all the way to the right (resistance decreases as the meter goes rightward). When I diminish it to RX100, it goes slightly less far to the right, reading about 1, and when I set it to RX10, the needle ends up at 14. So, a resistance of 140 ohms, if I'm understanding correctly.

However, when I set the meter to RX1, meaning no multiplier, suddenly it's pegged all the way to the right again. Shouldn't it be hanging out around 140, i.e. mostly to the left? Am I doing something wrong?

3) I tried testing continuity between the prongs and the plug, and got nothing, so I'm assuming you can't test cable continuity in a wall wart without applying voltage from the mains. Is that correct? Since the transformers appear to be shot this isn't an issue right now, but having gotten a couple nasty shocks through the years I'm a little gunshy about live 120V...

[Mitch]

You should be testing for DC volts.

Mitch

[thegoldenband]

Mitch, on Mon Aug 22, 2011 2:57 PM, said:

You should be testing for DC volts.

Which would involve plugging the adapter in, correct? The idea behind testing for resistance was to avoid working with live voltage, but I'm guessing there's no way around it if I want to test continuity with the cable.

And yeah, I did realize that I'd have to switch to measuring DC if I plug the adapter in. Kind of a moot point, though, since neither of the dead adapters seems to have a working transformer, so there's no need to test continuity -- right?

(Am I at least correct that you can test the transformer itself by measuring resistance across the prongs?)

Edited by thegoldenband, Mon Aug 22, 2011 3:23 PM.

[CRTGAMER]

thegoldenband, on Mon Aug 22, 2011 3:22 PM, said:

Mitch, on Mon Aug 22, 2011 2:57 PM, said:

You should be testing for DC volts.

Which would involve plugging the adapter in, correct? The idea behind testing for resistance was to avoid working with live voltage, but I'm guessing there's no way around it if I want to test continuity with the cable.

And yeah, I did realize that I'd have to switch to measuring DC if I plug the adapter in. Kind of a moot point, though, since neither of the dead adapters seems to have a working transformer, so there's no need to test continuity -- right?

(Am I at least correct that you can test the transformer itself by measuring resistance across the prongs?)

But what would be the correct resistance? Just plug the brick in and test the DC voltage output. Be sure to set the range on the dial to get an accuate scaled reading. Watch out for original NES plugs which are AC

Edited by CRTGAMER, Mon Aug 22, 2011 3:31 PM.

[thegoldenband]

CRTGAMER, on Mon Aug 22, 2011 3:30 PM, said:

Quote

(Am I at least correct that you can test the transformer itself by measuring resistance across the prongs?)

But what would be the correct resistance?

If I'm reading Ray Carlsen's guide correctly (linked above), the point is that you're testing whether any current (supplied via the battery in my multimeter) is making it from one prong to the other. If the resistance is less than infinite -- if the needle moves -- then the transformer is probably still working; if you get nothing, then the transformer is probably "open" and dead. Here's what he says:

Quote

"If the unit is completely dead and assuming you have a multimeter, check the primary of the internal transformer by measuring the resistance across the prongs that go into the AC outlet. If it measures infinity, the transformer is open and the device is probably not repairable. The transformer usually opens because of an overload... either in the powered device, or because the diodes or filter capacitor in the wart are shorted. [...] If you measure some resistance across the AC input terminals, the tranny is probably OK and the problem is somewhere else."

Is this advice incorrect in some way? Ray did a fantastic job repairing my C64 and seems to really know his stuff, so...

CRTGAMER, on Mon Aug 22, 2011 3:30 PM, said:

Just plug the brick in and test the DC voltage output. Be sure to set the range on the dial to get an accuate scaled reading. Watch out for original NES plugs which are AC

Will do, and that all makes sense to me. It's a VCS adapter, so I'll expect to see 9V DC.

Edited by thegoldenband, Mon Aug 22, 2011 3:40 PM.

[Stephen Moss]

thegoldenband, on Mon Aug 22, 2011 1:01 PM, said:

I'm testing a couple dead AC adapters for the VCS right now (part numbers #CO16353 and #CO16353-101), and had a few questions:

1) If my multimeter (a Radio Shack Micronta 22-202A) is set to measure resistance, and I touch both prongs (across the wall wart itself) and get no movement of the needle, that means the transformer has failed and the adapter is toast, right? Just confirming that I'm correctly understanding the guide I'm reading (written by the excellent Ray Carlsen).

By prongs I assume you mean the parts that go into your wall outlet, if so there should be continuity if the transformers primary is not open circuit. If you are reading infinate resistance then either the primary is open circuit or the connection between it and the prongs is open circuit.

Quote

1a) Should I throw these out, or can some part of them be salvaged? The cable might be good for all I know. I don't plan to salvage them myself, but if someone else is able...

Tha cable is worth keeping as with time and constant flexing someones cable may go open circuit, the case may also be worth keeping if someone drops theirs and breaks it.

Quote

2) When I tested my good adapter, it did show continuity, but I was a little surprised by one thing. When I set the ohms range switch to RX1K (meaning a multiplier of 1000), and test across the prongs of the wall wart, the needle is pegged all the way to the right (resistance decreases as the meter goes rightward). When I diminish it to RX100, it goes slightly less far to the right, reading about 1, and when I set it to RX10, the needle ends up at 14. So, a resistance of 140 ohms, if I'm understanding correctly.

However, when I set the meter to RX1, meaning no multiplier, suddenly it's pegged all the way to the right again. Shouldn't it be hanging out around 140, i.e. mostly to the left? Am I doing something wrong?

Generally transformers will measure very low resistance (essentially zero) as it is basically a piece or wire, the anomalous reading is probably due to current value the meter is using on that range.
If possible check it with a standrard resistor and if it reads the resistor ok then it is just a quirk of the meter on that range with very small resistnaces, if not you meter is at fault.

Quote

3) I tried testing continuity between the prongs and the plug, and got nothing, so I'm assuming you can't test cable continuity in a wall wart without applying voltage from the mains. Is that correct? Since the transformers appear to be shot this isn't an issue right now, but having gotten a couple nasty shocks through the years I'm a little gunshy about live 120V...

You cannot test continuity between the prongs that go into the wall outlet and the plug that goes into the VCS as there is no physical connection through the transformer.

[thegoldenband]

Stephen, thanks so much for your reply, which definitely helped clarify several things for me.

Stephen Moss, on Tue Aug 23, 2011 6:16 AM, said:

Tha cable is worth keeping as with time and constant flexing someones cable may go open circuit, the case may also be worth keeping if someone drops theirs and breaks it.

Got it, and I think I've already found a home for the cable!

Stephen Moss, on Tue Aug 23, 2011 6:16 AM, said:

You cannot test continuity between the prongs that go into the wall outlet and the plug that goes into the VCS as there is no physical connection through the transformer.

Ah, of course! I apologize for my naivete, but at least one lightbulb just went on. OK, here's another question:

I had a CO10472 that seemed to test good, and I played a couple games with it on a 2600 Jr. Then after a few hours I tried it out again, but when I turned on the Atari it went on for a split second before failing, and then the LED on the console slowly faded from red to nil. (The Atari works fine with other, known-good adapters.) I tried powering up the Atari again and got much the same result, but by the third or fourth attempt, I was getting nothing.

I'm getting appropriate resistance across the prongs, so the "transformer's primary is not open circuit"...right? But I'm not seeing any voltage at the VCS plug end, whereas my known-good AC adapter tests normally (it actually reads 10-11V, rather than 9V), so I know my multimeter is able to read voltage and that I seem to be doing it properly.

I seem to remember that this has happened before with this adapter -- I tested it at my parents' house and had the same result. So something about letting it sit for a period of time seems to bring it back temporarily. Any ideas? Mainly I'm just curious about what's probably happening inside on a physical/electromechanical level.

By the way the only unit I ever failed in high school physics was the one on electricity. Despite that I still pulled out a B for the quarter! For some reason I've always struggled with this stuff, but I'm trying to improve.

Edited by thegoldenband, Tue Aug 23, 2011 11:35 AM.

[Stephen Moss]

The 10-11 volts off load is quite common in fact I am surprised it is not a couple of volts higher, to save time repeately answering question about replacement power units I wrote a little article on them and posted the link to the PDF either in this or the Jaguar forum, either search for the link or go to the hardware section of my website to read it as you might find it useful background information.

Intermittent faults are difficult to track down in person, via e-mail or forum messages it is impossible. None of the components should fail in such a manner which leaves two options...
1) a dry solder joint (makes intermittend contact as it moves due to thermal expansion/contraction or vibration by moving the power unit) or
2) an intermittent connection in the cable.

Try connecting it and while holding the cable steady at its midpoint wiggle the cable each side of the center point to see if the VCS goes on and off. A break could occur anywhere although most like points are at each end or anywhere is has been repeatedly folded.

Edited by Stephen Moss, Thu Aug 25, 2011 5:51 AM.