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Thread ID: 122847	2012-01-16 00:50:00	Using replacement AC adaptor - help needed	tims (10184)	Press F1

Post ID	Timestamp	Content	User
1254397	2012-01-16 00:50:00	I have a Compaq CQ61 laptop that has a dead power supply AC adaptor (18.5V). To get it going I want to use another adaptor (same output voltage) but the plug that fits into the laptop on this adaptor is different so I have to use the old plug from the dead adaptor. The problem I have is that the +18.5V goes to the center pin of the original plug but this plug also has two other separate connections on the inner and outer barrel, each of which has a separate connection to two separate co-ax type shields/braids in the cable. My replacement AC adaptor only has an inner cable (18.5V) with one outer shield so my question is (finally!:clap); would the -18.5 V be connected to the inner or outer part of the plug or can I just connect the shield to both the inner and outer barrel? Hope the attached photo makes the above clearer! 3515	tims (10184)
1254398	2012-01-16 03:04:00	Two layers of shielding seems a bit over the top, but if they're braided then they're most certainly shielding. Chances are your regular single shield coax will be fine. To further eliminate doubt you could hack your way into the dead transformer/power pack and ensure that the two layers of braids have a common origin in the power pack. If they do share the same origin then they're simply earthing/shielding in purpose - not that I'm an expert - that's just an opinion.	Paul.Cov (425)
1254399	2012-01-16 03:27:00	Laptop Battery NZ have got new ones for $29.95 why risk it	jinja_thom (4306)
1254400	2012-01-16 03:40:00	The problem I have is that the +18.5V goes to the center pin of the original plug but this plug also has two other separate connections on the inner and outer barrel, each of which has a separate connection to two separate co-ax type shields/braids in the cable. My replacement AC adaptor only has an inner cable (18.5V) with one outer shield so my question is (finally!:clap); would the -18.5 V be connected to the inner or outer part of the plug or can I just connect the shield to both the inner and outer barrel? The photo isn't a lot of help unfortunately because the resolution is too low, however if there are two negative connections it may be that one is simply a shield. Being grounded it should have whatever polarity the computer ground is, but there could be a small element of risk in making connections to an alternative supply unless you know how the Compaq original is configured. You might have to find somebody who has a working supply to be able to check it, otherwise cut off the plug leaving about 200mm of cable attached, link the two outers and feed it from your good 18.5 volt supply. If they are both at a potential of -18.5 volts I can't see any harm arising unless they are two separate negative lines within the computer, but that wouldn't make sense, so one is possibly a shield connected to negative. Compaq hasn't been around for a few years now, so that must be quite an old computer. There's no need to hack into the old supply, if you have a meter just measure between the two negatives and if directly connected you'll be OK. If in doubt a web search might help. Cheers Billy 8-{)	Billy T (70)
1254401	2012-01-16 05:14:00	OK, thanks for the replies . I took apart the dead adaptor and checked how the shields (inner and outer) were connected on the cct board in the adaptor . The outer shield on the cable appears to be connected to the inner shield via a small capacitor so maybe the outer shield is just more protection against electrical interference or whatever . I'll connect the -18 . 5V on my replacement adaptor to the inner shield only (the inner part of the plug barrel) and see what happens . The photo isn't a lot of help unfortunately because the resolution is too low, however if there are two negative connections it may be that one is simply a shield . Being grounded it should have whatever polarity the computer ground is, but there could be a small element of risk in making connections to an alternative supply unless you know how the Compaq original is configured . You might have to find somebody who has a working supply to be able to check it, otherwise cut off the plug leaving about 200mm of cable attached, link the two outers and feed it from your good 18 . 5 volt supply . If they are both at a potential of -18 . 5 volts I can't see any harm arising unless they are two separate negative lines within the computer, but that wouldn't make sense, so one is possibly a shield connected to negative . Compaq hasn't been around for a few years now, so that must be quite an old computer . There's no need to hack into the old supply, if you have a meter just measure between the two negatives and if directly connected you'll be OK . If in doubt a web search might help . Cheers Billy 8-{)	tims (10184)
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