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I recently bought a faulty Eagle spectrum from ebay thinking I could fix it. But seems the beast has a desease I am too stupid to fix.
Symtoms: First it doesn't ground balance. After Choosing coin program I never get to the second screen when it says "Lower loop to ground".
If I pull the trigger to force the program to change to search mode it gives out a steady tone "detecting a quarter" VID83. If I put some metal stuff under the loop it will also sense that and show a change on the meter. But all the time it gives out a sound detecting a "ghost Quarter". I havn't had the chance to hook up another coil but even with no coil connected at all it gives out a sound detecting a ghost quarter.
With an improvised oscilloscope (My PC soundcard with Software) I could measure a 6,59 khz signal after the OPAMP U2A at C4. In a way the thing acts as if the coil is not nulled. The signal amplitude changed when I placed some metal under the coil. So the detector works in a basic sense.
If I to go to Geb Manual option I can't get rid of the ghost Quarter signal either.
After opening the box I found somebody had soldered a socket for the Eprom U29 (93C46) in the schematic. What function has that Eprom? Does it have something to do with ground balance?
If somebody here has a clue how to narrow down the source of the error and to find the faulty part I would highly appreciate it.
Ganesh
Symtoms: First it doesn't ground balance. After Choosing coin program I never get to the second screen when it says "Lower loop to ground".
If I pull the trigger to force the program to change to search mode it gives out a steady tone "detecting a quarter" VID83. If I put some metal stuff under the loop it will also sense that and show a change on the meter. But all the time it gives out a sound detecting a "ghost Quarter". I havn't had the chance to hook up another coil but even with no coil connected at all it gives out a sound detecting a ghost quarter.
With an improvised oscilloscope (My PC soundcard with Software) I could measure a 6,59 khz signal after the OPAMP U2A at C4. In a way the thing acts as if the coil is not nulled. The signal amplitude changed when I placed some metal under the coil. So the detector works in a basic sense.
If I to go to Geb Manual option I can't get rid of the ghost Quarter signal either.
After opening the box I found somebody had soldered a socket for the Eprom U29 (93C46) in the schematic. What function has that Eprom? Does it have something to do with ground balance?
If somebody here has a clue how to narrow down the source of the error and to find the faulty part I would highly appreciate it.
Ganesh
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