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1300DC blown fuses

StyX

StyX

Lets go!
Hello,

My brother came over with his 1300DC that had the fuses blown on the power supply board.
To narrow down the problem we removed the output boards, still blows the fuses.
Then we removed all leads connected to the power supply board except ground leads.
Still the fuses blow.
My conclusion is that it is something on the power supply board that is broken.

Please tell me that this procedure is OK, and feel free to give suggestions for further analysis.

Thanks
 
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ManyMoonsAudio said:
I would say you have shorted outputs for starters..
Click to expand...

But I removed the output boards and the fuses still blew.


I will pull out the power supply board tomorrow and have a closer look at those rectifier diodes. (tried to measure them in circuit yesterday, and they seemed all right)

Any other suggestions are more than welcome.
 
In the service manual it looks like there are two rectifiers right after the transformers and before the P800 power supply board, that is where I would start looking for a problem.
 
Finally got around to test the rectifier diodes, and sure they were shorted.
Is this a common problem? I.e. Is the root cause believed to be the diodes failing due to old age or might there be a more serious problem causing the diodes to fail?

Anyway, anybody knows the specification for those diodes? They are called DS133B but my google skills led me nowhere :(
A wild guess is that something like: "FEP16DT 200V 16A TO-220AB Dual Diode" should do it, what do you think?
 
Which rectifier/diode(s) were shorted?

I have had rectifiers fail suddenly on rebuilt equipment for no apparent reason. Typically I think they fail on units in original condition because there is a flaw in the unit which overloads them.
 
I think the "FEP16DT 200V 16A TO-220AB Dual Diode" are common cathode types. If you look at the schematic and the board layout for the 1300DC you will see that the original DS133 internal diodes are connected anode to cathode. You may just have to use 4 rectifier diodes. Since this is the low voltage power supply, I would try some 1N4007 rectifiers.

Tom
 
after replacement of diodes or maybe better before if you have to order the diodes .is check the output transistors for short circuit . you may need to order more components . if outputs are shorted check the drivers as well .
in all cases power up with a dim bulb tester until its cured of faults .
edited because i got confused ..
looked at schem . and i think would check transistors on power board as well . something may well have shorted to cause the diodes to short
 
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catrafter said:
I think the "FEP16DT 200V 16A TO-220AB Dual Diode" are common cathode types. If you look at the schematic and the board layout for the 1300DC you will see that the original DS133 internal diodes are connected anode to cathode. You may just have to use 4 rectifier diodes. Since this is the low voltage power supply, I would try some 1N4007 rectifiers.

Tom
Click to expand...

Yep, listen to Tom. I had the same problem with my 3650 about 20 years ago. Used 2 1N4007 back to back. Never had a problem with it.
 
Yes, I will go for the 1N4007. Will also go through the rest of the board and probably take the opportunity to do a recap, as I have the board out of the box.
 
Hi,

Just wanted to say that we finally have replaced those diodes.
And the result is: no more blown fuses! :banana:

Thanks a lot to all that contributed in this thread!:beerchug:

However, we noticed that one channel is sounding kind of dull comparing to the other, not a big difference in volume but it sounds kind of muffled, missing treble.
My hunch is pre amp problem, my brother will hook it up as power amp soon, then we'll know.
Edit:
It seems to have been caused by our quickly hacked together pre-main jumpers. It is now in my brothers system and it plays very well.
 
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