Ray Jefferson regulated D.C. Battery guard

[Eduard]

Hi, I have broken battery charger in my sailboat and I try to repair it. It has burned resistor 1K (R7 on blueprint), but I 'm not sure what kind part I need. I mean how much W ( 1/8W, 0,25W.....). I see I can buy it on eBay. What is right size?

 

[(*steve*)]

You could replace it with a 1/2W metal film resistor (assuming it's a resistor).

But there may be a fault which has caused this resistor to fail as a symptom rather than as a cause.

What happened immediately before it failed?

 

[Eduard]

You could replace it with a 1/2W metal film resistor (assuming it's a resistor).

But there may be a fault which has caused this resistor to fail as a symptom rather than as a cause.

What happened immediately before it failed?

It is resistor. I don't know what is happened - I bought boat with this broken charger. 3a fuse also burned

 

[Eduard]

It is resistor. I don't know what is happened - I bought boat with this broken charger. 3a fuse also burned

it look like 1/2w is in blue color, i had yellow-is 0.25w(i guess). Is 0.5w would be better?

 

[(*steve*)]

well, if there's a fault it may last a little longer. Generally speaking a higher power resistor is not going to cause problems.

 

[Eduard]

well, if there's a fault it may last a little longer. Generally speaking a higher power resistor is not going to cause problems.

Thanks. Will update when I fix it.

 

[Eduard]

Well, did put new transistor (R7 1/2w 1K)-burned as soon I plug it in the wall. Next step I'll try to replace R6 and R7 together. Question: is R6 resistor 75K ?

 

[(*steve*)]

As I suggested, replacing resistors is likely to achieve nothing more than confirming that the resistor failure is a symptom not a cause.

Most likely you have a semiconductor which has failed short circuit. Look carefully for a transistor with burn or smoke marks, or with cracks our pieces missing.