Voltage regulator

[fastpcuser]

HI all,

I'm new to electronics and to this forum too so please have patience with me .

I'm fixing this aquarium ozone generator and I think the Voltage regulator is bad. it is a
L7815CV regulator I have 19.5 V DC input voltage but there is only 1.5 V dc output.

Is there any way to check or test voltage regulator ?

 

[(*steve*)]

The first thing to do is to measure the current being drawn and to feel the temperature of the regulator.

If the current exceeds an amp, or if the regulator is too hot to touch, the problem is in the load connected to it.

In any case, my next step would be to disconnect the load and measure the voltage again.

The 7815 is pretty cheap (and rugged) so you could go out and grab another one and just replace it. If it is the 7815 it's a quick fix. If it's not the fault then you have eliminated it.

Is the 7815 on a heatsink?

 

[fastpcuser]

Its not on heat sink , and it gets hot pretty fast within like 30 sec or so you can't even touch it. its at 115 F. I can't really disconnect the load because its all on one circuit board. so when I measure the voltage the first pin is receing 19.5 and third only gets 1.8V and this thing needs 15V to run.

IF I try the resistance between pin 1 and 3 it shows 3.063 M

 

[davenn]

are you sure you have it connected correctly ?

also as a test, disconnect the load from the output of the regulator and measure the output voltage

Dave

 

[fastpcuser]

I'm sure its connected correcty since this is original board from manufacturer and I haven't replaced the regulator yet. but let me see if I can remove it from the board and test it.

 

[fastpcuser]

OK I have removed pin 3 and the output reads 14.95 which is about right. It regulates 15V for a transformer for a pump for ozone generator so my guess would be that the transformer is bad ?

 

[(*steve*)]

No, that is an indication that your load is faulty. There may be a short circuit somewhere.

The fact that the regulator is heating up so quickly to so high a temperature indicates this (and the fact that you get the right voltage when the load is disconnected)

 

[fastpcuser]

So I found the bad part which is some kind of transformer. That is the actuall load. I can't find it anywhere. I have attached picture for it just in case anybody knows where to find one. The numbers on it are

PFB-5194
Made In Taiwan
0639

thank you

 

[fastpcuser]

also there appears to be burned resistor bu I can't find it anywhere it is a 41 OHM...
Color bands are 1. yellow 2. brown 3. black 4. Gold or can I use any other ones ?

 

[davenn]

So I found the bad part which is some kind of transformer. That is the actuall load. I can't find it anywhere. I have attached picture for it just in case anybody knows where to find one. The numbers on it are

PFB-5194
Made In Taiwan
0639

thank you

Thats a line output transformer. Generally used for creating EHT voltage to feed the back of a TV picture tube. Tho some people use them for other uses. The EHT comes off that red wire poking out the top

So how do you know that it is the bad part ? there should be other components driving that transformer.
Do you have a circuit for this system ??

Dave

 

[davenn]

also there appears to be burned resistor bu I can't find it anywhere it is a 41 OHM...
Color bands are 1. yellow 2. brown 3. black 4. Gold or can I use any other ones ?

you would probably get away with a 39 Ohm or a 47 Ohm what wattage is it ? what colour is the body of the resistor ?

Dave

 

[fastpcuser]

I don't have the circuit but I have picture of it somewhere. well I have removed it from the circuti board and voltage regulator was showing correct voltage output. and if its connected the regulator is getting how and showing low voltage. attached is picture with the board

Is there any other one I can use instead ?

 

[fastpcuser]

you would probably get away with a 39 Ohm or a 47 Ohm what wattage is it ? what colour is the body of the resistor ?

Dave

its beige .. 1/2 watt I think

 

[beckya]

HI all,

I'm new to electronics and to this forum too so please have patience with me .

I'm fixing this aquarium ozone generator and I think the Voltage regulator is bad. it is a
L7815CV regulator I have 19.5 V DC input voltage but there is only 1.5 V dc output.

Is there any way to check or test voltage regulator ?

FYI... be careful. I was fixing a tank that had a ballast hooked up to it. I was in a metal chair and got grounded in the chair. I would have died if my friend di not pull the plug out of the wall.

 

[fastpcuser]

well went to repair shop and they said there is probably bad Mosfet well the marking on it are IRF 350 and there seems to te a little symbol like a (IRF350a) is there a differennce between IRF350 and IRF350a ? or can I use either one.