[GreenKeys] Problem with Selector Magnet Driver Circuit on ASR33

[Steve Ripper]

Rob:

This is why you never leave the house with 32/33 pluged-in. Be sure you
pull the plug, or make sure the power source is turned off when not using
these machines!

Steve R.
248-787-0705
steve.ripper at gmail.com


On Sun, Jan 13, 2013 at 9:13 AM, Rob Jarratt <robert.jarratt at ntlworld.com>wrote:

> **
>
> I have noticed that when I plug in my ASR33 one of the parts becomes very
> hot, even when the ASR33 is switched off. I have located the source of
> the heat as a circuit board because there are tell-tale heat marks on the
> board and I can feel the heat there too. The heat marks correspond to the
> large area of solder on the back of the board, and the large resistor
> (R4) looks mottled and has no markings (possibly burned off?). Oddly, the
> large solder area does not appear to be connected to anything, I checked
> with a multimeter. From the markings on the metal plate that covers the
> board it would seem that R4 is getting very hot, the markings on the
> board suggest that R2, R5, R6 and R8 are also getting hot.
>
> On the back the board is marked 181823 and on the front it is marked
> 181821. The former part number is not mentioned in the parts document,
> the latter seems to be the selector magnet driver circuit and the
> description seems to correspond, so I think it is right. If that is the
> case R4 is 0.82ohm, but I don’t know its power rating.
>
> Also, while examining the components I moved one of them, when I did sothe track on back became detached from the board, although the track is
> still intact.
>
> So I have a few questions:
>
> Should this board be live when the ASR33 is plugged in, but not switched
> on?
>
> Why might there be heat marks associated with the large soldered area on
> the back, when it is not connected to anything?
>
> What are the power ratings of the large resistors R2, R4, R5, R6 and R8?
>
> What might cause R4 and possibly also R2, R5, R6 and R8 to get hot?
>
> What can I do to reattach the detached track to the board?**
>
> Regards
>
> Rob
>
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-- 
Cheers,

Steve Ripper
steve.ripper at gmail.com
248-787-0705
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