Gibbon 5 Active Speaker Repair. Any help appreciated.

[superdelicious]

Greetings!
Long time lurker, first time poster. Do let me know if this is the wrong thread to post this.

After 10 years of wonderful use, both units are now in amplifier heaven. I'm fairly competent with repair and soldering but in no way an engineer so I'm hoping anyone with expertise can chime in.
I tried emailing Monkey Banana for a schematic and they couldn't be assed to help me out. oh well.

Each speaker has 3 circuit boards:

1 - The Amp/Rectification board
2 - The Preamp board - help needed here
3 - Input board

Context
The transformer splits the secondary ±16v and ±10v to the amp board which has the rectifier and big caps and they seem to measure fine. But I dont really understand the PreAmp circuit. So the main winding is being fed to what looks like a mini PSU section?? Its also the section that seemed damaged... the x2 caps were dead (Open), 400v 2.2µF caps -dead and the SJE13003 (MJE13003 Clone? ) seemingly just blew up in one of em and crumbled in the other unit.
Replaced the x2 and caps, but still waiting on the 13003's .

BUT my question is, what is the purpose of this section?

- I assumed the 7812/7912 regulators were powering both the amp and preamp boards.
- Is this bit for adjusting 220v -->120v mains? Im confused because the transformer seems to already have the wires for 120v use, so i thought the mains voltage selector switch simple changes between the two..

Apologies if this all sounds convoluted. Any advice or correction on my assumptions is welcome.

Thank you all.

 

[DVDdoug]

I'm not sure why there is a separate preamp board either. Maybe it's for the controls. Or if it's bi-amplified it could be a crossover or maybe it's not a preamp but a tweeter amp.

I assumed the 7812/7912 regulators were powering both the amp and preamp boards.

Those regulators can only handle 1 Amp (and that's usually "optimistic") so they are probably for the preamp.

I think the "absolute maximum" rating is 40V input for the 78xx regulators, and in any case they don't work at 120 or 240V.

I don't know if it's worth re-building the thing... Maybe so if the power supplies are useful. The thing you usually never know with an active speaker is if there is some built-in "secret" EQ that you won't be able to duplicate.

Or you could get a pair of passive crossovers and make passive speakers.

 

[superdelicious]

I'm not sure why there is a separate preamp board either. Maybe it's for the controls. Or if it's bi-amplified it could be a crossover or maybe it's not a preamp but a tweeter amp.

Yes its bi-amped. TDA2052 each for the woofer and tweeter. The crossover is fairly basic at 3khz and ±6db cut/boost for low and high but theres 7 Opamps ( seems like a lot? ) but I dont really understand gain staging.. or is it because its fully differential?

Or you could get a pair of passive crossovers and make passive speakers.

lol... thats pretty much my setup right now. Found a single din kenwood 50w/4Channel and a random 150w sfx psu. Not ideal but works just fine.
If the replacements dont pan out, i might acquire one of those cheapo class D TPA3116 on AliExpress. I've yet to hear any of these TI amps in person but Im seeing rave reviews everywhere.

 

[AnalogSteph]

But I dont really understand the PreAmp circuit. So the main winding is being fed to what looks like a mini PSU section?? Its also the section that seemed damaged... the x2 caps were dead (Open), 400v 2.2µF caps -dead and the SJE13003 (MJE13003 Clone? ) seemingly just blew up in one of em and crumbled in the other unit.
Replaced the x2 and caps, but still waiting on the 13003's .

Be mindful that some 13003 clones have a pinout that is backwards from the original MJE13003. One end should be switching a transformer winding (usually the collector), the other go to local circuit ground (usually the emitter).

BUT my question is, what is the purpose of this section?

Looks an awful lot like some sort of standby power supply. Are you absolutely sure the primary side is not involved? (That would handily explain the 400V caps and 13003, alongside the "high voltage" symbol next to the power connector.) My guess would be that relay RL1 switches the main transformer, is it a 5 V or 12 V type?

Do these have an auto-standby function by any chance? That might explain the association with the preamp board. I don't see an optoisolator though... (This has to be a very loosely regulated supply, supporting the notion that it's not used for anything more critical than driving a relay.)

My theory would be that the supply got hit with a nice mains surge, hence why both speakers are toast.

If my deductions are correct, you should be able to bodge things back together in an always-on state.

 

[superdelicious]

Be mindful that some 13003 clones have a pinout that is backwards from the original MJE13003. One end should be switching a transformer winding (usually the collector), the other go to local circuit ground (usually the emitter).

Thanks.. ill keep that in mind. I only found one datasheet for the SJ13003 in the whole internet.. I hope it works and it seems to match up to the older TO-92

Looks an awful lot like some sort of standby power supply. Are you absolutely sure the primary side is not involved? (That would handily explain the 400V caps and 13003, alongside the "high voltage" symbol next to the power connector.) My guess would be that relay RL1 switches the main transformer, is it a 5 V or 12 V type?

Do these have an auto-standby function by any chance? That might explain the association with the preamp board. I don't see an optoisolator though... (This has to be a very loosely regulated supply, supporting the notion that it's not used for anything more critical than driving a relay.)

The thing is im not sure hence my confusion. To your question, yes it does. Mutes if nothing plays for 10mins. This is the relay datasheet.... 5A 250VAC || 5A 30VDC .
So its possibly a dedicated standby psu circuit? Hmmm.. They died differently.. the left speaker was taking FOREVER to turn on before going belly up but the right speaker just gave up which possibly might be some surge.

Thank you for replying!

 

[AnalogSteph]

The thing is im not sure hence my confusion. To your question, yes it does. Mutes if nothing plays for 10mins. This is the relay datasheet.... 5A 250VAC || 5A 30VDC .

What does the second line on the relay say? It should start with the nominal coil voltage.

So its possibly a dedicated standby psu circuit?

Sure looks like it. The only part I'm not yet sure of is how the auto-on works.