Acoustic 122 restoration

[Nyqusit5]

Hi,

I have an Acoustic 122 in for retoration. It has been butchered by someone trying to repair it. I have found gut pics online but if anyone has the scheamtic for this unit, it would be most welcomed.

Thanks in advance!

[gbono]

Not sure oif you found this site? WebHome < Acoustic < Wiki

Search the forum for 122 related topics. I believe the 122 was similar to the 126. What is the issue with the amp you have?

[Nyqusit5]

Yes, I have thanks. I could have missed the schematic but I think it is not there (I have looked for 126, 122 and 120).

The amp has been hacked with a lot of missing parts, some burnt components and disconnected cables. I'll really need the schematic to rebuild it as the gut shots I have found won't be sufficient.

[J M Fahey]

Acoustic 120/122/126 share the exact same electronics, including same PCB.

The "famous" one was 126; 122 is the cheaper watered down version, with lighter speaker, smaller chipboard (or MDF) cabinet instead of plywood, silkscreened Graphic EQ front panel instead of their trademark injected plastic "mask", etc.
But guts are the same so same schematic.

And 120 was same in a head version.

[Nyqusit5]

The one I have in has been put in an original head cabinet (probably swapped).

Still looking for the schematic...

[g1]

Could you post the board numbers? There may be other models using the same boards and it may be easier to find a schematic that way.
Otherwise, if you have to, musicparts.com has them for sale

[Nyqusit5]

Yes good idea. I'll check them up tomorrow.

[Fragger]

These guys? Model 124 schematic/ help in 11x, 12x, 220, 230, 320, 330 Forum

[Nyqusit5]

I'll try that , thanks!

[Nyqusit5]

The power board reference is 170102B and the preamp board reference is 170105. Hope this helps...

[Nyqusit5]

The power section seems to be identical to the schematic of the Acoustic 215B-120 on ampix.

Well, hum, after all, I am not sure about that...

[Nyqusit5]

Got it, but the output stage is playing...

A very generous person has sent me the schematic.
I have all the wiring and preamp back to normal but the power amp is still faulty.

When no load is connected, it works fine but when I connect a load (4Ohm), my current limiter's lightbulb lights brightly. I have used 2N3055 instead of MJ15024 for now as my local supplier is short of the latter but I believe that shouldn't be the problem?

[J M Fahey]

2N3055 is not enough there , but that's not the point today.
Do you have DC at the speaker out, with speaker unconnected?
And replacing outputs usually is not enough, you may very well have dead drivers or other problems.

[Nyqusit5]

I have no noticeable DC on output (30mA or so). I have also checked all transistors including the drivers. Do you think they could be faulty even though they check ok (in the circuit)?

[Jazz P Bass]

A very generous person has sent me the schematic.
I have all the wiring and preamp back to normal but the power amp is still faulty.

When no load is connected, it works fine but when I connect a load (4Ohm), my current limiter's lightbulb lights brightly. I have used 2N3055 instead of MJ15024 for now as my local supplier is short of the latter but I believe that shouldn't be the problem?

[ATTACH=CONFIG]25116[/ATTACH]

With a load connected, at idle, no signal,does the lamp limiter bright?
I can't tell from your post what you meant.
If the lamp is bright when running a load, well, don't do that.
All of the voltages are not up to par with the limiter in series.