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Drowning in broken gear, could use a little help.

brutal

brutal

YamaHoarder
Subscriber
Seems I've several slightly sick tuners on my hands.

I can probably get the T-2 low channel output resolved as I now have a good schematic, but this pesky T-7 refuses to deploy it's station memory feature. I found the following upon a second visual after resoldering a busted NiCad battery lead:

DSC_6010.JPG


Not sure if some moron put a resistor in place of a cap or it's some tuning option. There's other "cap" marked positions that are empty, and the piece looks like many others already present, but this sucker obviously grenaded. The darn thing pulls stations in great and otherwise just needs a restring due to an overzealous application of OIL on the tuning shaft and tuning knob mechanism that migrated to the string.

The schematic I have on this is unreadable at any resolution, a better scan would be appreciated if anyone has the Schem/SM.
 
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I'm sure you've checked it but I'll ask anyway. Is it possible that the NiCad has gone south and no longer holds a charge? :scratch2:
 
Wouldn't be the first time I've seen the silkscreen on the board not match. You will have to look at the circuit in the manual and see what is suppose to be there. Look at the reverse side and see if it been soldered on before, or if it looks factory soldered.
 
Punker X said:
Wouldn't be the first time I've seen the silkscreen on the board not match. You will have to look at the circuit in the manual and see what is suppose to be there. Look at the reverse side and see if it been soldered on before, or if it looks factory soldered.
Click to expand...

That was my thought, one leg looked rework, one factory wave. lol

If I knew the value, I'd just replace it.

The NiCad had a leg busted off so I'm sure that started the new and improved no-save feature, It's been charging for the requisite 3 days+ and only shows about 1/4 capacity but I don't know if the taco'd part is part of the issue. Shouldn't it at least retain station memory while powered on? If I set it per the manual, it doesn't stick.
 
just wire in another nicad. theres space in there, doesnt even have to be the same exact battery. all nicads are 1.2v per cell.
 
ke4mcl said:
just wire in another nicad. theres space in there, doesnt even have to be the same exact battery. all nicads are 1.2v per cell.
Click to expand...

After I pick one up, that's the plan. It's a standard AA size 1.2V NiCAD. All I have around here is NiMH rechargeables. Still something going on with that grenaded resistor.
 
Look at this crappy picture I downloaded from a Japanese site. It looks like your blasted part is factory installed ... and it might be a precision C0G cap maybe ... 4.7 pF possibly?
 
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It's the same part as the one just to the right of it. I think I see yellow violet black or 4, 7, and 0. It's not too likely part of your memory problem. It looks more like part of a filter circuit but I could be wrong on that.
 
Artie, Vint Age, you guys rock. I don't think I've ever seen radial caps that look like that, even when I was doing component repair in the Army 25 years ago, but that funky yellow base (and pink) are all over this thing and although it caused pause and a slightly confused look, it didn't click. Who's the moron? <looking in mirror...>

Vint Age, got a link for that site (was there any other info?)

Now if Radio Shack wasn't such a major POS and actually had a AA NiCad battery and I didn't have to order one. Oh well, I also ran out of 330K 1/4w resistors and zener diodes rebuilding my M-80's so I'll just place another mouser order.

Now to go find a suitable cap to try here...

Thanks guys. Anyone with a schematic is still welcome to jump in any time.
 
Punker X said:
Wouldn't be the first time I've seen the silkscreen on the board not match.
Click to expand...
I learned my lesson the hard way on that as well. Replaced over a hundred caps in a giant rackmount Tascam cassette thing a few months back and noticed some of the caps I put in were facing the wrong way. I then discovered that I had used the polarity marked on the opposite side of the board which didn't match the top. Had to go back through every single cap and compare against the schematic (lucky I had it). They had a few where it was marked wrong on both sides as well, and of course the majority of them were correct, but I had to sit there tracing things anyway. Serious PITA. I now instinctively double check all that crap as it comes out.
 
Vint Age said:
I'm thinking 47 pF ... rather than a 4.7. Can you measure the other one? :scratch2:

http://bluess.cocolog-nifty.com/labo/2009/04/yamaha-t-7.html
Click to expand...

It is 47pF. I put in a cheapo ceramic disk to test and you were right, filter circuit. I'm thinking someone "cut" this to change the tuning filters. Although the reason why escapes me, seems to pull in DX stations much better. Maybe it changed local station rejection or something, I'm no tuner wiz.

Thanks for the link! After google translate, I was able to find a reasonable schematic, and a couple message entries there also indicate it may be the LC7200 chip that's a common defect in these. There was mention of a diode as well, so I'll check that out and see if the IC is available anywhere in this galaxy. Else it gets cleaned up, buttoned up, and in the rack as manual tuning only.
 
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