Testing STK4142

[Andy 1964]

I have this module out of circuit for testing, from a Denon RCDM38 which is in protection mode, its the most likely failure point.
Pin 9 -VCC
Pin 10 RC out
Pin 11 +VCC
Pin 13 LC out
Testing resistance across these pin the results are
11&10=15MOhm
11&13=15MOhm
9&10=15MOhm
9&13=OL
Which suggests to me that -VCC to LC out is blown. Am I correct or should I be testing other pins?

[Andy 1964]

With the amp board completely disconnected its still in protection mode, so I am guessing power supply.

[Diabolical Artificer]

If the amp is in protection mode finding out why will help diagnose what possible circuits to test further. Depending on the protection circuit used and it's complexity they mostly work by detecting DC on the output. DC on the OP could be caused by various things, shorted OP transistors or in your case shorted power amp IC, leaky caps etc.

A good point to start is to check for DC on the speaker OP. Andy.

[Andy 1964]

The amp board is disconnected, so there cannot be any DC on the output. Its the testing of the STK I am not sure about. If I can get a pass result then move on to other circuits, if it has failed I will probably bin it. This is a micro HiFi with 9 boards crammed inside. It had a favourable review on What HiFi so thought it worth a look.

[FIXITNOW]

last time i had a STK i was not sure about i brought one off these
https://www.ebay.co.uk/itm/262935943...Bk9SR67qyuHtYA

and then built it up as a test bed with the supect STK

[Sideband]

Originally Posted by Diabolical Artificer

If the amp is in protection mode finding out why will help diagnose what possible circuits to test further.

...not forgetting the protection circuit itself! I was caught out once by a protection circuit that had actually failed. In desperation, I disconnected the protection circuit to 'see where the smoke came from' and to my surprise, everything started working (into dummy loads I hasten to add)! It was a s/c transistor in the protection circuit.

[Andy 1964]

I think I may have found the problem. Unit stripped down to test transformer. There no is continuity on the primary winding, the red and black going in.!!!

[Herald1360]

That could be easier to sort than sourcing a decent STKxxxx!

(Though it's always possible that a blown STKxxxx might have cooked the transformer in the first place )

[Analogue man]

Originally Posted by Andy 1964

I think I may have found the problem. Unit stripped down to test transformer. There no is continuity on the primary winding, the red and black going in.!!!

If that is so the amp would not even have gone into protection mode.