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Thanks, appreciate the clarification.

Am I correct in thinking that the AC frequency determines how many times a second the speaker moves in and out?

I can't say now. Some problem manifested that I never solved, it hung around the place for years and then sold cheap. Do not recall what the problem was. I'd say if cheap enough it's good enough to see if basic tlc will render it usable for in the shop.

It is damned likely that you know more about grounds and amplifier output stages than I do. But speakers operate on AC, which is my main point. I always assumed the amp did not change the 60 cycle alternating frequency as supplied, but I don't know everything....

Speakers run on AC at 60 cycles per second. It would not matter which wire was connected to + or - if you were just using one speak on a mono system. It has no relation to trumpet sounds. Speakers do not imitate the blowing (or sucking?) of air in a wind instrument, they use electric transducers...

Just reviewed this thread, there was a little new traffic, and I saw the OP contains a set of files I hosted on Photobucket. They now bear unsightly watermarks, and may go away altogether. So I just uploaded those pics to an album here. So here's the photo documentation of my T-70 find in 2013...

T-70's as found

T-70 wins A/B test with Boston A-60s

T-70 crossover

T-70s as HT and stereo mains

view with woofer removed

I got an all-in-one solder melter and suction gadget, the Parts Express #370-325 mentioned her previously. Seems to have done the trick! Initially got very small diameter hole, but my ugly paper-clip-on-a-soldering-iron tool then worked to enlarge. New part soldered-on on, it remains only to...

Hakko or Pace units would be very nice to have I'm sure, if I did this sort of thing all the time and got paid to do it. For my one-off job, let me put it this way: I can buy a whole refurbished board for this TV for $50.00, an option I am getting closer to exercising all the time....

OK. How would you do that?

By putting more solder on the bottom side and heating with iron, I am able to melt what's inside, at least enough that solder will flow through and come out on other side. I've not been able to clear hole even so. The solder hardens instantly when I remove the iron, so neither toothpick nor...

Near as I can tell, it's single layer, circuits on top and bottom only.

All seemed fine. Problem with this device was mechanical--the flapper door that serves to hold the inserted optical cable in position had broken.

OK, that's what I wanted, some rationale for what's been happening. So we need a blob of solder and the tip of actual soldering iron with it's excellent thermal mass to melt the plug. Then try toothpick or solder sucker.

The tip of the paper clip melts fresh solder off the roll like crazy. That's 60/40 lead stuff.

I can't get over the feeling that my hot paper clip ought to melt its way through. Either heat transfer is not occurring, or there is now non-meltable stuff in the holes. Can that happen?

Sucker won't work unless you melt the solder. That's what I can't seem to do.

A classic noob problem I'm sure. I've solderd discrete stuff like crossovers like crazy but haven't messed with PCBs much. Pictured is I/O board from TV. Removed a bad toslink jack from it but wound up with four plugged holes. Cleared two with the lashup shown on a 40 watt soldering iron, or its...

Pictures of work and process

Toslink jack location bottom