Hantarex Polo Star 25 Keeps HOT blowing :((

[ID4]

Hi!

My monitor Hantarex Polo Star 25 is keeing the Hot (Horizontal Output Transistor) shorted (BU2727AW), always that I power on the monitor it happens, and the "click ... click" sound appears.

I have seen some topics about Polos 2/28/etc with the same issue, but nobody posted the solution.

At the first, I brought new BU2727AW form ICS, and replaced the original philips one with this, but they keeping blowing too, so I brought a new Flyback (ELDOR 1242.0358B) to replace the HR 8068.

Soldered the new FLYBACK and the new BU2727AW, but the HOT blow again.

Then I chaged the diodes D44, D48 and the Cap C99, altought the original ones seemed Ok. Tested a new BU but it get blow again.







So I tested the D52 Diode and it was ok, the I checked the T1 (IRF 640), T4 (IRF 630), T6 (IRF 630), T7 (IRF 630) form the SWITCH BOARD and the T6 was shorted, so I replaced the four IRF transistors.

Then I tested the monitor WITHOUT the BU2727AW soldered, to test the voltages in the PIN 1 and PIN3 of the FLYBACK, and te voltage in the collector of the BU2727AW;

FLYBACK Voltage in PIN 1 and 3: 94,2 V

BU2727AW Voltage: 94,2 V

Tested the BASE of BU2727AW with my osciloscopie:



It seems Ok.

Then I soldered the HOT, powered on the monitor and it get blow again, the "click ... click" sound appears.

I have a second Hantarex Polo Star 25 in working orden, so I took this working chassis and tested it with the Controls Board, E - W board and tube with yoke of the faulty monitor, THE MONITOR WORKED PERFECTLY.

So I know that my faulty Hantarex Polo Star 25 don't have the problem in the Controls Board, E - W board or the tube / yoke, I must be in the switch board, PSU or the mainboard.

I desoldered and tested D4, D6, D16, D10, D13, D48, D52, D47, C103, C101 an all of them was Ok, but the monitor keeps blowing Bu2727AW and the IRF630 (T6) form the switch board.

PLEASE HELP ME !!!!

[ID4]

Hi!

I'll post the components that I have tested and results

MAINBOARD

R135 - 10,6 Ohm

T19BC (BDX53C) - NPN / Hfe= 36, Vf = 1,21 V

C99 (MKP 8N2J1600) - 7913 pF, ESR = 20 Ohm

C101 (MKP 1N5J1600) - 1650 pF, ESR = 26 Ohm

C103 (MKP 012J630) - 15,44 nF, ESR = 30 Ohm

D52 - Vf = 941 mv, C= 91 pF

D6 - Vf = 909 mv, C= 109 pF

D4 - Vf = 881 mv, C= 102 pF

D10 - Vf = 818 mv, C= 196 pF

D13 - Vf = 791 mv, C= 183 pF

D16 - Vf = 820 mv, C= 93 pF

D48 - Vf = 679 mv, C= 90 pF

D47 - Vf = 693 mv, C= 94 pF

T22 BU2727AW (ICS) - NPN / Hfe= 13, Vf = 173 mv - NOW CAN BE SHORTED -

SWITCH BOARD

C4 (82J250) - 780,5 nF, ESR = 0,63 Ohm

C6 (18J400) - 201,5 nF, ESR = 4,63 Ohm

T1 (IRF640, Replaced by IRF640N) - MOSFET / C = 2,22 nf, Vt = 4,72 v

T4 (IRF630, Replaced by IRF630N) - MOSFET / C = 1,11 nf, Vt = 4,52 v

T6 (IRF630, Replaced by IRF630N) - MOSFET / C = 1,54 nf, Vt = 4,12 v - NOW CAN BE SHORTED -

T7 (IRF60, Replaced by IRF630N) - MOSFET / C = 1,95 nf, Vt = 3,55 v

I need to check C109, DX1 and CX4.

Any more?

Where is DX1 and CX4?

Thanks!

ID4

[ID4]

According to the scheme, I unsoldered and tested components  "aurround" the T6 ( IRF630 ) of the switchboard.

In brackets are the values indicated in the scheme:

D8 (18V) - Uf = 964 mv / c = 30 nf

C11 (47n) - 59nf / Esr = 22 Ohm

D14 (BAV21) - Uf = 1,04 v / c = 22 pf

D16 (BAV21) - Uf = 1,03 v / c = 26 pf

C14 (220p) - 253pf / Esr = 23 ohm

R28 (10k) - 9,77 k

R25 (18k) - 10K - According to his color codes this component is 10k, and 10k gives the tester,  but the scheme indicates 18k

R32 (100R) - 101 Ohm

R2 (56K) - 56k

R26 (100k) - 99,6 K

D4 - Uf = 873 mv / c = 15 pv

T2 - NPN HJfe = 164v / Uf = 777mv

R33, R34, R5 y R11 do not exist.

[ID4]

Hi!

The BU2727AW is desoldered, the flyback too and the T6 was replaced by a new one.

I hooked up an incandescent 120V/60W bulb to the D20 Cathode and It light up perfectly.

Values:

Anode D20 - 90,5 V

I adjusted the RV1 to the Maximum, and get this values:

Anode D20 - 92,6 V

Cathode D20 -  92,6 V

Other componets:

Cathode D10 -  28 V

Cathode D4 -  179,4 V

SP8 - 17,79 V

IC2 PIN3 - 11,81 V

IC2 PIN1 - 17,67 V

[grantspain]

you don't want to be turning rv1 up to max unless you wish to kill the chassis
b+ test point is flyback pin 3,i think it should be about 105vdc

a low b+ would not cause the transistor to blow

[ID4]

you don't want to be turning rv1 up to max unless you wish to kill the chassis
b+ test point is flyback pin 3,i think it should be about 105vdc

a low b+ would not cause the transistor to blow

Hi!

Thanks for answering, turning RV1 to max onny give 92,6 V in D20.

I Will test the voltaje in FLYBACK Pin 3.

ĄThanks!

ID4

[emospt]

Hi,
I know it's an old topic, but I have the same problem.

can you please help me and tell mehow you solved this repair?

Thank you for your time

Hi!

My monitor Hantarex Polo Star 25 is keeing the Hot (Horizontal Output Transistor) shorted (BU2727AW), always that I power on the monitor it happens, and the "click ... click" sound appears.

I have seen some topics about Polos 2/28/etc with the same issue, but nobody posted the solution.

At the first, I brought new BU2727AW form ICS, and replaced the original philips one with this, but they keeping blowing too, so I brought a new Flyback (ELDOR 1242.0358B) to replace the HR 8068.

Soldered the new FLYBACK and the new BU2727AW, but the HOT blow again.

Then I chaged the diodes D44, D48 and the Cap C99, altought the original ones seemed Ok. Tested a new BU but it get blow again.







So I tested the D52 Diode and it was ok, the I checked the T1 (IRF 640), T4 (IRF 630), T6 (IRF 630), T7 (IRF 630) form the SWITCH BOARD and the T6 was shorted, so I replaced the four IRF transistors.

Then I tested the monitor WITHOUT the BU2727AW soldered, to test the voltages in the PIN 1 and PIN3 of the FLYBACK, and te voltage in the collector of the BU2727AW;

FLYBACK Voltage in PIN 1 and 3: 94,2 V

BU2727AW Voltage: 94,2 V

Tested the BASE of BU2727AW with my osciloscopie:



It seems Ok.

Then I soldered the HOT, powered on the monitor and it get blow again, the "click ... click" sound appears.

I have a second Hantarex Polo Star 25 in working orden, so I took this working chassis and tested it with the Controls Board, E - W board and tube with yoke of the faulty monitor, THE MONITOR WORKED PERFECTLY.

So I know that my faulty Hantarex Polo Star 25 don't have the problem in the Controls Board, E - W board or the tube / yoke, I must be in the switch board, PSU or the mainboard.

I desoldered and tested D4, D6, D16, D10, D13, D48, D52, D47, C103, C101 an all of them was Ok, but the monitor keeps blowing Bu2727AW and the IRF630 (T6) form the switch board.

PLEASE HELP ME !!!!