I've been asked to repair 2 old metal detectors
The 1976 "Yukon 77B" I've repaired but if anyone knows more about the 2
National Semiconductor 8 pin DIL custom? chips marked 274 0-004 and 624
0-001 I would be interested.

The 1978 "Coin Magnum" seems to be vaguely working in the opposite sense to
how i'd expect , does anyone have an operation guide or any
technical details before I delve in deeper , at least it uses industry
standard chippery. Anyone know what the central lump covered in vacuum
moulded cover is hiding?

"N Cook"  wrote in message
news:f4n32f$7fk$1@inews.gazeta.pl...
> I've been asked to repair 2 old metal detectors
> The 1976 "Yukon 77B" I've repaired but if anyone knows more about the 2
> National Semiconductor 8 pin DIL custom? chips marked 274 0-004 and 624
> 0-001 I would be interested.
These may not be "custom" chips, but just manufactured with house codes
printed on them in place of the normal type numbers.
If the detector is repaired, probing around the chips with an oscillloscope
may give you a better clue what's happening.

"N Cook"  wrote in message
news:f4n32f$7fk$1@inews.gazeta.pl...
> I've been asked to repair 2 old metal detectors
> The 1976 "Yukon 77B" I've repaired but if anyone knows more about the 2
> National Semiconductor 8 pin DIL custom? chips marked 274 0-004 and 624
> 0-001 I would be interested.
These may not be "custom" chips, but just manufactured with house codes
printed on them in place of the normal type numbers.
If the detector is repaired, probing around the chips with an oscillloscope
may give you a better clue what's happening.

"N Cook"  wrote in message
news:f4n32f$7fk$1@inews.gazeta.pl...
> I've been asked to repair 2 old metal detectors
> The 1976 "Yukon 77B" I've repaired but if anyone knows more about the 2
> National Semiconductor 8 pin DIL custom? chips marked 274 0-004 and 624
> 0-001 I would be interested.
These may not be "custom" chips, but just manufactured with house codes
printed on them in place of the normal type numbers.
If the detector is repaired, probing around the chips with an oscillloscope
may give you a better clue what's happening.

"N Cook"  wrote in message
news:f4n32f$7fk$1@inews.gazeta.pl...
> I've been asked to repair 2 old metal detectors
> The 1976 "Yukon 77B" I've repaired but if anyone knows more about the 2
> National Semiconductor 8 pin DIL custom? chips marked 274 0-004 and 624
> 0-001 I would be interested.
These may not be "custom" chips, but just manufactured with house codes
printed on them in place of the normal type numbers.
If the detector is repaired, probing around the chips with an oscillloscope
may give you a better clue what's happening.

"N Cook"  wrote in message
news:f4n32f$7fk$1@inews.gazeta.pl...
> I've been asked to repair 2 old metal detectors
> The 1976 "Yukon 77B" I've repaired but if anyone knows more about the 2
> National Semiconductor 8 pin DIL custom? chips marked 274 0-004 and 624
> 0-001 I would be interested.
These may not be "custom" chips, but just manufactured with house codes
printed on them in place of the normal type numbers.
If the detector is repaired, probing around the chips with an oscillloscope
may give you a better clue what's happening.

"N Cook"  wrote in message
news:f4n32f$7fk$1@inews.gazeta.pl...
> I've been asked to repair 2 old metal detectors
> The 1976 "Yukon 77B" I've repaired but if anyone knows more about the 2
> National Semiconductor 8 pin DIL custom? chips marked 274 0-004 and 624
> 0-001 I would be interested.
These may not be "custom" chips, but just manufactured with house codes
printed on them in place of the normal type numbers.
If the detector is repaired, probing around the chips with an oscillloscope
may give you a better clue what's happening.

"N Cook"  wrote in message
news:f4n32f$7fk$1@inews.gazeta.pl...
> I've been asked to repair 2 old metal detectors
> The 1976 "Yukon 77B" I've repaired but if anyone knows more about the 2
> National Semiconductor 8 pin DIL custom? chips marked 274 0-004 and 624
> 0-001 I would be interested.
These may not be "custom" chips, but just manufactured with house codes
printed on them in place of the normal type numbers.
If the detector is repaired, probing around the chips with an oscillloscope
may give you a better clue what's happening.

"N Cook"  wrote in message
news:f4n32f$7fk$1@inews.gazeta.pl...
> I've been asked to repair 2 old metal detectors
> The 1976 "Yukon 77B" I've repaired but if anyone knows more about the 2
> National Semiconductor 8 pin DIL custom? chips marked 274 0-004 and 624
> 0-001 I would be interested.
These may not be "custom" chips, but just manufactured with house codes
printed on them in place of the normal type numbers.
If the detector is repaired, probing around the chips with an oscillloscope
may give you a better clue what's happening.

"N Cook"  wrote in message
news:f4n32f$7fk$1@inews.gazeta.pl...
> I've been asked to repair 2 old metal detectors
> The 1976 "Yukon 77B" I've repaired but if anyone knows more about the 2
> National Semiconductor 8 pin DIL custom? chips marked 274 0-004 and 624
> 0-001 I would be interested.
These may not be "custom" chips, but just manufactured with house codes
printed on them in place of the normal type numbers.
If the detector is repaired, probing around the chips with an oscillloscope
may give you a better clue what's happening.

"N Cook"  wrote in message
news:f4n32f$7fk$1@inews.gazeta.pl...
> I've been asked to repair 2 old metal detectors
> The 1976 "Yukon 77B" I've repaired but if anyone knows more about the 2
> National Semiconductor 8 pin DIL custom? chips marked 274 0-004 and 624
> 0-001 I would be interested.
These may not be "custom" chips, but just manufactured with house codes
printed on them in place of the normal type numbers.
If the detector is repaired, probing around the chips with an oscillloscope
may give you a better clue what's happening.