Channel Master/Sanyo xstr
 

Taking a stab at a CM 6 xstr radio. 5 caps at 30mf/6v and not polarity stamped. Is the black dot +/-? Meter thinks -. Not sure how the exclamation got included. Not needed

I second the (-) mark notion that you were thinking, because most electrolytic capacitors I've ever seen (with a few rare occasions) almost always have the negative polarity marked on them and the positive polarity unmarked. :yes:

I had my way with a Channel Master model 6515 a few years back. 10 capacitors and it plays like a champ!

Forgot to mention: The original capacitors in mine had black dots but, as I remember, the "+" was also well marked on top.

I have that radio under the Sanyo name and also got confused on the polarity of the caps when replacing them.

I ended up measuring the voltage across a few and confirmed the black dot was negative (-).

I'm currently working on a mid 1960s vintage Akai AM/FM Transistor radio that the capacitors in that thing were a mish-mash of those capacitors that look like the ones that were used in these Channel Master/Sanyo radios, some Nichicon (Nippon Chemicon), and the notoriously bad "ELNA" capacitors, which the "ELNA" Caps of course flunked the ESR test on my newly acquired Analog ESR Meter, and the Nichicon caps of course passed with flying colors and the "Sanyo" caps (as I'll call them because they seem to almost always be in Sanyo made electronics from the 1960s and 1970s) were mediocre at best (they were measuring on the verge of failing.)