onix oa21 + soap.

[mangoy]

Help desperately needed. I have had this amp for over twenty years and have hardly given it any thought as it has been faultless. Now,however, I am stricken. The oa21 (e) has started blowing it's internal fuse. Anybody have a clue as to why or what to look at first? Does anyone have a schematic? Any help putting my amp back on it's feet would make me eternally grateful.

[mjf]

hello.
probably the outputstage is damaged - that often happens......
i have no schematic (it is hard to find).
do you have a multimeter?
so you can measure the emitter res at the output transistors (0,22 ohm or so.....) and so on..............
perhaps there are three fuses,one for the mains and two for the output to speaker.............? which one is bad?
you can have a look if there are burnt parts or damaged (psu)elcos...........
greetings.......

[mangoy]

Well there is no schematic to be had. I have got an email from Tony Brady and he doesn't have one.The fuse that blows is the mains 2.5v time delay one. On advice received I disconnected the transformer from the pcb, fuse didn't blow and led on indicator remained dark. I have now to check the rectifier and output transistors. Hopefully it will be one of them that is faulty and i will only have to find suitable replacements for these old parts. Hopefully mr. Brady will reply to my last entreaty and recommend something.

[mangoy]

Also I have no multimeter and I cannot see any obvious damage.The next stage is to find someone to diagnose exactly what has occurred and then source replacements.