Advice needed for Loksound repair.

[TheDukeOfWellingtons]

Last year I managed to blow up one of the power amplifiers on a Loksound chip from a Bachmann Class 20 by causing a short circuit across the speaker terminals. Part of the circuit board was blown away, primarily around the 'extra' pin of the 21, i.e the one that stands alone at the end of the row of 11. Having found a replacement amplifier chip I now can hear the sound again but it is very quiet, like something else is not receiving power so I was wondering if anyone could suggest what else may need to be connected to this pin? A circuit diagram for a Loksound 21 pin decoder would be extremely useful but presumably difficult to obtain? Any advice would be much appreciated, Cheers.

[Pinkmouse]

What's the chip? It may well have external gain setting resistors, and you might need to replace those as well if they're in the feedback network and been damaged.

[TheDukeOfWellingtons]

The power amp was a TDA8541, one of three across one end of the ESU loksound decoder. Thanks for your suggestion regarding resistors, that could well be the problem or at least one of them anyway. I think the decoder is ready for the bin but a couple of my more electronically savvy mates want to complete a repair. Without a detailed diagram I'm not sure if its possible but I will pass on what you said and hope for the best. It will probably cost me more in beer than just replacing it with a new one. Cheers.

[TheDukeOfWellingtons]

Thanks Baldrick, I'll pass that on to my man. Unfortunately he and the faulty decoder are 40 miles away. Further to Al's reply above the gain setting resistors all check out OK.

[TheDukeOfWellingtons]

We're currently seeking suitable test equipment and will report soon. My 'expert' was expecting around 5V regulated, according to the spec sheet, so asks whether the 11 - 15V is taken from the track or is generated on-board? Many thanks for your continued interest and assistance.