Positive or negative tip: how to tell?

Question

I have an old Sanyo cassette recorder, model M 1540A. Can find no information on what polarity of tip it uses. Only know that it's 6.0 Volt. No markings on outside of case to show what it is. Sanyo website and customer service has no information and websearches come up empty.

I have opened the unit. It takes 4 "C" cell batteries. The circuit board is old and isn't labeled. I can't tell how the AC adaptor jack is wired to the board. A label on the outside says to use AC Adaptor

6CV120 or 6CV121.

I have two adaptors I am considering using with it, both positive tip. One is a class 2 transformer that outputs 6V DC and 300mA. The other (much bigger)is labeled AC Adaptor and outputs 6V DC and 2000mA.

Any ideas?

Bob Myers · Accepted Answer

Check to see which end of the battery stack connectsto the PCB "ground" or common (generally, this willbe fairly easy to find on the PCB).  The "tip" willalmost certainly be the OTHER end.Bob M.

Ban · Answer

With your ohmmeter put one side to the battery negative connection and check out which of the adaptors poles has continuity with it (possibly the outside). Then you can insert the plug without modifications. You can then try either supply.

Mike · Answer

Don't connect the meter when set to measure ohms to a power source! Makesure you're measuring volts instead of ohms.Mikecheck

John Fields · Answer

---It would probably have confused the original poster less (and possiblyprevented him from damaging his meter or blowing a fuse, orwhatever...) if you'd have advised him to remove the batteries beforedoing any continuity testing, don't you think?-- John Fields

John Fields · Answer

---How do you know he can't?  Usually it's pretty easy, you just stickthe probe in there.------See "Me-JF.tif" on abse. ;)-- John Fields

Ban · Answer

Read again what I wrote and do not confuse the original poster please.Ban

Ban · Answer

How can you reach the terminal with the batteries inside? And I want to see the guy that has working batteries in a years-old gadget?-- ciao BanBordighera, Italy

DAW · Answer

Idiots, both of you.

John Fields · Answer

---Ha,ha, you're wrong. Ban isn't an idiot.----- John Fields

Positive or negative tip: how to tell?

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