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CS50 blowing uppermost fuse

 

solved. ended up being a bad diode pair (D1)
 

could i be correct in guessing that the problem couldn't be a 'blown' primary winding since the PS is blowing fuses ? i mean it shouldn't be able to bring power through the supply with a blown primary?
 

update: i haven't had much of a chance to look into this until recently- it's looking like there is an open circuit (no connection) between the BROWN and either GREY or YELLOW wires on the primary side of the transformer -? the grey and yellow have at least five ohms between them however...? i'm just wondering if it's possible the transformer somehow blew (???) - these seem very heavy duty so it seems unlikely...

thoughts?
 

Hi Florian - there are three fuses mounted on the front left of the power supply - and they are all mounted (stacked) in a? group of three horizontally - so it is the uppermost fuse... it's a 1,25A fuse that I replaced ... i hope that clarifies something? thanks
 

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Which one do you mean with "uppermost"?

On 23.07.17 05:41 , jw_dewdney@... [yamahacs80] wrote:

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My CS50 started blowing fuses. A preliminary check revealed nothing obvious in the power supply - is there a recommended routine for this? Maybe first checking for shorts in the board feeds?
 

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Find out which voltage the fuse is protecting.
Then desolder board for board all those voltages. Measure with the ohmmeter for short. Once a board shows 0 Ohm then that board has the short somewhere. Further measure out all tantalum capacitors for short as well as other capacitors. It's a bit time consuming but there is no other way to find the short. Good luck?

Csaba?

Sent from Csaba's iPhone

On 23 Jul 2017, at 05:41, jw_dewdney@... [yamahacs80] <yamahacs80@...> wrote:

?

My CS50 started blowing fuses. A preliminary check revealed nothing obvious in the power supply - is there a recommended routine for this? Maybe first checking for shorts in the board feeds?
 

My CS50 started blowing fuses. A preliminary check revealed nothing obvious in the power supply - is there a recommended routine for this? Maybe first checking for shorts in the board feeds?

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