Hbl htv-160c1

[3d0]

Hi guys, got this AC adapter with no output.
The large transformer is making a strange noise, I think it's toast?

What do you think, thanks!

[budm]

Re: Hbl htv-160c1

I do not think the circuit is Oscillating. It that really a thermal fuse? it looks more like Thremistor. What is the resistance reading? If it is Thermal fuse, then you would have 220V at both end since Thermal fuse will have <1 Ohm resistance.

[3d0]

Re: Hbl htv-160c1

Tried searching for a datasheet, didn't find much.
The part is Aupo A3-F and the resistance is 1 Ohm?

Thanks

[stj]

Re: Hbl htv-160c1

if those voltages in the foto are rfom the board,
then it's running.
i'd say the big toroidal inductor is open-circuit.

[budm]

Re: Hbl htv-160c1

You have to measure the primary voltage using AC mode on the meter to know if it is running or not, the circuit is just a high frequency self oscillating. It can also be that your meter cannot display high frequency (>30KHz) AC at the out put (it is not 50 or 60 Hz AC output). Also, what do you use for the Ground ref point for those voltage measurement?

[stj]

Re: Hbl htv-160c1

board says 11.5v output,
his foto shows 11.5 going into the choke - look at the underside foto again.

[budm]

Re: Hbl htv-160c1

It is not 1:1 power transformer, that drive voltage of 11.5 on the primary side is way to low, those two large transistors (or MOSFETs) are running from the primary line voltage, you can see that one of the Collector pin has 162VDC, another Emitter has 230V, so primay is not driven by 11.5V.
He needs to find out how many windings there are on that power transformer. He also needs to tell us which point he uses for the circuit ground ref point.
"The part is Aupo A3-F and the resistance is 1 Ohm?" if one end has 220V and another end is showing only 9.9V that means the voltage drop on that 1 Ohms is 210V which is impossible.

[budm]

Re: Hbl htv-160c1

Thermal fuse voltage drops reading error, need to verify circuit ground ref point. You can also see the error in reading of the two points (where I indicate the B+) that are on the same trace, one point show 228V, anther poInt next to it shows 230V.
BTW, the B+ feeding the circuit is not clean steady DC (100Hz pulsing DC), as you can see, there is no large electrolytic cap for filtering.

[3d0]

Re: Hbl htv-160c1

I pulled out the transformer and tested it for continuity from the primary to secondary side, then tested the primary side for resistance it was 0.8 Ohms, the secondary was 0.5 Ohms that doesn't look good does it.

[budm]

Re: Hbl htv-160c1

The DCR reading will be very low (that is typical for power transformer), but to the circuit driving it , the circuit will see at as high impedance.
You need ringer tester to find out if the transformer has shorted winding or not, I do not believe it does, otherwise the Thermal fuse would have blown up by now.
Did you test those two large transistors to see if they are OK? P/N as printed on the body of those transistors?

[3d0]

Re: Hbl htv-160c1

Thanks budm, I used one of the primary ac inputs as a ref. thats why the readings are sketchy, sorry.
I'll post the new ones soon, no I didn't test them. They are BUL38DA.

Sorry to confuse you stj.

The DMM was set to AC.

[budm]

Re: Hbl htv-160c1

OK, that explained the strange readings you are getting.
Can I also get better focused picture of the bottom side, and bottom side in sections (may be in 4 sections) so I can easily trace those copper traces on the board.
So those two transistors are NPN.
http://elcodis.com/parts/432008/BUL38D.html#datasheet

[budm]

Re: Hbl htv-160c1

That one with 640V? That cannot be, that is the out put of the bridge rectifier circuit, non filtered.

[3d0]

Re: Hbl htv-160c1

That one with 640V? That cannot be, that is the out put of the bridge rectifier circuit, non filtered.

Checked it again, its 640V. I used the ref. point in the previous image you pointed out as ground? If I look at it now its D1 on the anode (+) side where I put the black probe. Using the cathode side as gnd. the readings are different, I measured the thermal fuse 229V on one side and 15V AC on the other.

The transistors tested good, also the small npn transistor C945 is ok.

Thanks for the guidance and explanations, much appreciated.

[3d0]

Re: Hbl htv-160c1

I'm not sure how a CAT II device could survive readings over 640V without blowing up something internally, so I went out and bought a new auto range DMM, and all the readings up till now are false.
I feel bad for giving misleading info. Srry guys

[momaka]

Re: Hbl htv-160c1

I'm guessing this PSU is for driving 12V halogen bulbs for a house lightning fixture?

I've repaired one similar to this design before (self-oscillating, no secondary feedback, and no controllers of any kind). On mine, two of the bridge rectifier diodes were blown and the two BJTs were OPEN. So I say pull your BJTs out and check them either for short or open circuit. Also test all small signal diodes for S/C and resistors for O/C.

[budm]

Re: Hbl htv-160c1

BTW, How many wires are there for the power transformer? 4 or more?

[3d0]

Re: Hbl htv-160c1

I'm guessing this PSU is for driving 12V halogen bulbs for a house lightning fixture?

I've repaired one similar to this design before (self-oscillating, no secondary feedback, and no controllers of any kind). On mine, two of the bridge rectifier diodes were blown and the two BJTs were OPEN. So I say pull your BJTs out and check them either for short or open circuit. Also test all small signal diodes for S/C and resistors for O/C.

Yes momaka, it's a halogen lamp transformer.
I've already tested all 3 npn transistors out of circuit, they tested good, might as well take them out again and double check with the new dmm.

BTW, How many wires are there for the power transformer? 4 or more?

Only 4 wires on the big transformer.

Thanks guys

[stj]

Re: Hbl htv-160c1

meters giving stupid readings are caused usually by a flat battery.
dont trust any "low battery" indicators - they arent worth shit!

[3d0]

Re: Hbl htv-160c1

meters giving stupid readings are caused usually by a flat battery.
dont trust any "low battery" indicators - they arent worth shit!

I replaced the battery but still get abnormal values. Tough I would like to know what fools one meter and not the other, it's beyond this topic for sure.
It might be leaking diodes in the bridge rectifier, or just the unfiltered/rippling dc running at 100-120Hz not being filtered through a capacitor.

Tonight I will have more time to investigate, and maybe with some help and guidance figure out whats really wrong with it.