Marshall Stanmore bluetooth amp.

[Tech. Tom]

I'm not sure if this is something that is topical for this website but I'd appreciate any help. I'm working on this Marshall Stanmore bluetooth amp. It's dead. I have 160V raw B+ but that's it. I can't find a schematic. There is black hard glue on components covering part numbers. Has anyone had success repairing one of these? Thanks for any input.

[Jazz P Bass]

Can you elaborate on 'dead'?
No power led?
No sound output?
No Bluetooth connection?

160Vdc on a small unit like this seems a bit excessive.
Or is that on the SMPS capacitor?

This video seems to show a short at the power in jack, possibly caused by the 'black goop'.
https://www.bing.com/videos/search?q...7&&FORM=VDRVRV
(Cannot understand the language, Vietnamese maybe?)

[Tech. Tom]

Hello Jazz P Bass: Dead...no lights anywhere, no sound at all. It does have a SMPS which is where the 160V is on the capacitor, no secondary voltages.

[xtian]

I did repair a Marshall bluetooth speaker, and the odd trick was, it would not power up (EVEN WHEN PLUUGED IN) until I replaced the dead lithium battery pack, then it worked fine. Good luck!

EDIT: I looked at my records--it was the Marshall Tufton.

[Tech. Tom]

Thanks Xtian, but this one doesn't have a battery.

[The Dude]

Often, the cause of a SMPS not running is shorted diodes on the secondary, so I'd start by checking those. If you have a scope, see if it tries to fire up and then shuts down repeatedly. If it does, it's likely protecting itself and there is a short on the secondary. If it doesn't fire at all, it's more likely a primary side issue. That's about all the help I can offer without a schematic. Also remember that an SMPS primary has it's own ground, so don't connect a scope to primary ground unless you like fireworks.

[Tech. Tom]

Thanks for the suggestions. Yes there is a lot of black goop on the board so it's hard to check components. I think I'll scrape as much as I can then try check for secondary shorts. I'm wondering if this black goop is conductive.