Tricky resistor question

[zorbzz]

Hi guys I am trying to repair a Denon avr 1804 reciever and the main problem first was the 7815 and 7915 voltage regs.
I replaced them first and then found some .22 ohm 1 watt fuse resistors were open, replaced them with the only ones I had which were 1 ohm 1/4 watt items, measured the output voltages from the regs and they were perfect but then dropped to nothing again.

Upon further inspection the 1/4 watt 1 ohm resistor on the 7815 feed side had opened again.
Do you reckon I really need some 1 watt resistors to continue diagnosis or should the 1/4 watt ones work ok, and do I really need exactly .22 ohm values.
Thanks heaps for any replies.

 

[Diver300]

Your 1 Ω, 1/4 W resistors will only allow 0.5 A before they exceed their power rating. The fuse resistors will take somewhere around 2 A before they exceed their power rating.
I would suggest checking how much current each regulator is taking. It sounds like some fault has caused them to take too much current.

I have no idea if that fault is still present.

 

[alec_t]

Until you identify what is drawing excess current you will keep on frying regulators/fuses unless you limit the current in some way. Perhaps 100Ω or so, or a car light bulb, in series with the reg output?

 

[zorbzz]

Ok thanks I never thought of that I just thought the 1/4 watt resistors were failing because of the 1 watt requirements but to think about it they must have had a high current draw in the first place to fail.