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Sound repair to terra cresta pcb


gameroom

Question

Hi,

 

I have a terrra cresta pcb in my possession for a while now, and would like to have a go at repairing it.

 

It only cost me $10 including the $10.90 postage. Bargain, reckon.

 

The sound is not working (reason for the price), and after visual inspection have found the following problem.

 

attachment.php?attachmentid=15182&stc=1&d=1267941883

 

The pins are still in the board but the component missing. Not sure what it was or where to find the information about what it could be. Any ideas? :unsure Looks like it was bolted to the pcb.

 

Everything else on the pcb looks visually intact.

 

Will keep everyone up to date with my progress.

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I reckon it will be the same as a moon cresta (but I could be wrong - I was once:D).

 

Here is the audio circuit from Moon Cresta:

 

http://www.homepin.com/pics/mcaudio.jpg

 

It shows an MB3712 as the audio output amp. If you follow the track pins on the PCB see if they match the diagram.

 

Looking at your pic pin 4 is ground (which is correct) and it seems that pin 7 goes to ground via a largish electro cap so I'm betting this circuit (if not exact) would work, but check the other pins.

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I reckon it will be the same as a moon cresta (but I could be wrong - I was once:D).

 

Here is the audio circuit from Moon Cresta:

 

http://www.homepin.com/pics/mcaudio.jpg

 

It shows an MB3712 as the audio output amp. If you follow the track pins on the PCB see if they match the diagram.

 

Looking at your pic pin 4 is ground (which is correct) and it seems that pin 7 goes to ground via a largish electro cap so I'm betting this circuit (if not exact) would work, but check the other pins.

 

But an MB3712 is an 8 Pin SIL, whereas, the pictures shows that the missing Amp has 7 pins. Pin 5 on an MB3712 is un-used and as such, not shown in your schematic. Regardless, best to double check first before fitting anything.

 

Regards,

 

Johns-Arcade.

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Many thanks to johns-arcade and homepin for your advice.

 

I have traced the tracks and found the following:-

 

pin 1 - goes to the var resistor so must be input

pin 2 - 22uf 25v cap

pin 3 - 220uf 16v cap

pin 4 - ground

pin 5+6 - these tracks follow together across both pcbs so assume output

pin 7 - 470uf 16v cap and to 12v jamma connector

 

The only thing I can find different to the schematics of MB3730 is the cap on pin 7.

 

I usually buy my ICs from WES but they dont have the MB3730 listed in their catalog.

 

Does anyone have one they wish to sell, or know of an australian supplier?

 

Thanks again for your help.

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I don't know of anyone in Australia that would stock them - maybe a member has one he would part with?

 

I am still in the electronic markets in China so I will grab some today for my stock anyway so then they *will* be stocked in Australia for the future. PM me your postal details and I can get one in the post to you tommorow.

 

Should only take 3 or 4 days to arrive (we send a staff member to Hong Kong to post as it is faster and more reliable). We go to the HK post office almost every day so it's no problem to add one small envelope for you.

 

Cheers.

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Thanks homepin.

 

Could you send 2 x MB3730 to me please (as a spare)

 

also could you please be on the lookout for 2 x STK392-110 (Convergence IC).

 

These are for a Toshiba 50D9UXA rear projection, and I think the chips are SANYO.

 

PM of address sent, thank you.

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I'll send you one of these as well with the other gear

 

Thanks Mike. I'm starting to get the shakes now. Had this board 3 years now, and may finally get some sound out of it.

 

Cheers.

 

ps. do you have any LM1875T. Looking for 2. If you have them, I would rather get them from you.

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Thanks Mike. I'm starting to get the shakes now. Had this board 3 years now, and may finally get some sound out of it.

 

Cheers.

 

ps. do you have any LM1875T. Looking for 2. If you have them, I would rather get them from you.

 

SURE HAVE

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