Technics SA-EH770 No Sound

[ReeceyBurger123]

Hello chaps, need some input on this amp here. I brought this faulty originally not turning on, the speakers that came with it are also damaged badly (the actual speakers not the cabinets). After fixing the power problem the amp was not outputting any sound what so ever, the protection circuit engages normally and the sound processor shows the input working however no sound, no Dc at speaker terminals what so ever.

A few minuets later the amp module which is an RSN311W64 device blew up and there is a chip on the module with a hole in it (not fixable) Nothing else is shorted on the amp. Just wandering before I replace this Ic could anything else be causing no sound, normally if the Ic was bad it would throw up an error but no :L

Any input on what to check next is much appretiated. Thank you

[vinceroger69]

Re: Technics SA-EH770 No Sound

service manual link if anyone needs it

[Compgeke]

Re: Technics SA-EH770 No Sound

Looks like that's another variation of a Darlington pack. Those aren't exactly known for reliability, I've seen a few either go pop on their own or burn up something in the path (like a resistor or trace).

I'd say it's most likely the pack itself was bad which could very easily have destroyed the speakers. I had another Technics amp (SU-something, was BOTL) that had the "no output" until leaving it on for a few minutes until it decided to put a ceramic resistor on fire. Also used packs but an STK 2-channel pack rather than a 6-channel one.


I'd personally not put much effort into this and consider it a writeoff. This isn't exactly a high end setup, basically a home theatre in a box from the early 2000s. For the cost of finding a new pack and then speaker fixes you'll be out the same as you'd be just finding another system that doesn't use the packs.

[ReeceyBurger123]

Re: Technics SA-EH770 No Sound

service manual link if anyone needs it

Cheers

[ReeceyBurger123]

Re: Technics SA-EH770 No Sound

Looks like that's another variation of a Darlington pack. Those aren't exactly known for reliability, I've seen a few either go pop on their own or burn up something in the path (like a resistor or trace).

I'd say it's most likely the pack itself was bad which could very easily have destroyed the speakers. I had another Technics amp (SU-something, was BOTL) that had the "no output" until leaving it on for a few minutes until it decided to put a ceramic resistor on fire. Also used packs but an STK 2-channel pack rather than a 6-channel one.


I'd personally not put much effort into this and consider it a writeoff. This isn't exactly a high end setup, basically a home theatre in a box from the early 2000s. For the cost of finding a new pack and then speaker fixes you'll be out the same as you'd be just finding another system that doesn't use the packs.

Thanks for the info buddy, I have found an Ic hopefully it will fix it. The original speakers were smashed up by the owners little child lol however im unsure of how a little girl does something like that to speakers with out going un-noticed. I have the SA-EH790 with respective speakers I was using my speakers to test this amp, luckily the protection circuit actually protected my speakers when the Ic blew.

Hopefully just the Ic is bad and got too hot causing it to explode when I was testing it.

Will let you know how it goes

[ReeceyBurger123]

Re: Technics SA-EH770 No Sound

Got an Ic on order cost £20 but worth it just to see if it will work.

[ReeceyBurger123]

Re: Technics SA-EH770 No Sound

I finally installed the Ic today almost a year later, and the fucker is fixed

Replaced the RSN311W64A class H amplifier Ic and I have sound output yessssss. Will upload images later on. I need to find the parts like the back cover for this etc and put it all the way together and give it a proper test I still need to rebuild the one speaker but that will come in time