Trevor Wilson wrote:

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Not unusual for high value resistors to fail open.


** Well they don't fail short very often - but high rates of such in new looking equipment is very unusual.

**I've never seen them fail S/C.

** ROTFL....



This was also true for leaded resistors.

** Only those with lots of DC across them, not the case here.

**Nope. Seen lots fail over the years.


** Yawnnnn......

TW claims all kinds of impossible things.


But chip resistors are unusually vulnerable cos of exposed silver.

**Certainly are. I've seen a few fail.


** The amp in question is a "DV Mark" combo with 3 x PCBs covered in SMD.

Every chip resistor ( 100+ of them ) is corroded after storage in its original packaging for 6 years or so.

It uses just 2 obsolete Sanken SAP 5-pin darlingtons, has no VI limiting or rail fuses but has an extension speaker jack just waiting to be shorted. Peak available output current is +/- 30 amps double the max Ic of the transistor.

SMPS with the markings ground off the control chip.

Will drive 200W @ 4ohms but has totally inadequate cooling for this condition and no thermal shut down.

The fitted speaker is 16 ohms with a *tin* neo magnet.

No schem is available.

Total PITA.


...... Phil