FSP FSP228-3F01 ( Teco/Viewsonic TV)

[satinser]

Above power supply is from Teco tv but is also used in Viewsonic models. No standby light on tv. Checked caps in psu replaced many of them on secondary side as they had badly swollen both above and below. Fuse F1 T4.OA had not blown so thought it was only cap issue but still no standby light when retested.
Have now fitted the full power supply repair kit even though fuse F1 had not blown thinking that that should resolve the problem but still fails to work with still no standby voltage on testing back in tv. Has anyone any knowledge of this power supply with any ideas as which component is likely to be the cause of this fault probably caused by bad failing caps in power supply that didnt cause main fuse to blow? Be very grateful for any help.

[tom66]

Re: FSP FSP228-3F01 ( Teco/Viewsonic TV)

Schematic may help

[budm]

Re: FSP FSP228-3F01 ( Teco/Viewsonic TV)

Please see these links:
https://www.badcaps.net/forum/showth...F01#post302856

https://www.badcaps.net/forum/showth...F01#post373874

You may have bad transistor Q7 and Zener diode ZD4.

[satinser]

Re: FSP FSP228-3F01 ( Teco/Viewsonic TV)

Many thanks for your replies they are much appreciated.
Have already replaced Q7 and ZD4 as a part of the power supply repair kit (1001B) consisting of IC1,IC2,Q4,Q9,Q11,R65,R28 and R29 also as mentioned in original post all secondary caps on secondary side of PSU have been replaced. This kit shouldnt have been necessary to fit as main fuse F1 hadnt blown but as replacing the caps only hadnt corrected the issue thought I would fit it anyway. However even after fitting all of the above components power supply is still dead. Previously I have repaired a FSP 228-3F01 but in that case fuse F1 had blown and fitting the above components (Kit 1001B) corrected the issue. Looks increasingly like I will have to source a replacement PSU.

[ben7]

Re: FSP FSP228-3F01 ( Teco/Viewsonic TV)

Many thanks for your replies they are much appreciated.
Have already replaced Q7 and ZD4 as a part of the power supply repair kit (1001B) consisting of IC1,IC2,Q4,Q9,Q11,R65,R28 and R29 also as mentioned in original post all secondary caps on secondary side of PSU have been replaced. This kit shouldnt have been necessary to fit as main fuse F1 hadnt blown but as replacing the caps only hadnt corrected the issue thought I would fit it anyway. However even after fitting all of the above components power supply is still dead. Previously I have repaired a FSP 228-3F01 but in that case fuse F1 had blown and fitting the above components (Kit 1001B) corrected the issue. Looks increasingly like I will have to source a replacement PSU.

OK lets start by testing voltages for the ICs 1,2 and 3, and S (IDK why it isn't a number instead - it is the dual OP-AMP chip)
ICS - what is the voltage across pins 8(+) and 4(-)?
IC1 - what is the voltage across pins 12(+) and 10(-)?
IC2 - what is the voltage across pins 1(+) and 2(-)?
IC3 - what is the voltage across pins 8(+) and 6(-)?

[satinser]

Re: FSP FSP228-3F01 ( Teco/Viewsonic TV)

Many thanks for last post. I have now discovered that after several minutes of switching on this power supply the led on front of tv starts to flash. Slowly at first then faster and eventually red led light stays on constantly. When switching the tv on the led light turns green to indicate that tv is on. The tv however stays off because there is still no 24volt from power supply to run inverter. I have tried warming the power supply with hairdryer and found that if the primary side is heated the 24volts is restored and tv starts as normal. When I received this tv from customer all caps on secondary side had blown badly. As explained in my first post all secondary capacitors have been replaced. I suspect that as heating power supply seems to start the tv as normal that caps the on the primary side are also failing. I have tested all the surface mounted capacitors on primary side and found them all to be ok. I now suspect that smd capacitors underneath the board miay be at fault. Be grateful if someone could advise whether this is likely.

[budm]

Re: FSP FSP228-3F01 ( Teco/Viewsonic TV)

I would think it will be electrolytic caps in the start up/running which is in the primary side, usual value will be 22~56uf 50vdc or so. ESR of the caps will go down when heated

[satinser]

Re: FSP FSP228-3F01 ( Teco/Viewsonic TV)

I actually thought that but all tested ok. There are 5 electrolytic capacitors on primary side-
3 x 33uf 50volt and 2 x 10uf 50volt.

Underneath the board in the area I have heated there are 7 smd capacitors testing them with ESR meter capacitor c17 shows ESR of over 20. Anybody got a component list of fsp228 as all smd capacitors are unmarked.

[cheapie]

Re: FSP FSP228-3F01 ( Teco/Viewsonic TV)

Have you checked for cold joints? Has the big cap(s) on the primary side been replaced?

[satinser]

Re: FSP FSP228-3F01 ( Teco/Viewsonic TV)

Yes tested for dry joints.
The large smoothing cap is a 180uf 450volt I was sure at first that this was the problem. When I tested it with ESR meter it read 159uf but the esr was an acceptable .33 I have since subtituted a 220uf 450volt but it doesnt rectify the fault unless I again warm that area of the board with hot air. Which indicates that the faulty cap/caps are still present.
The fact that it doesnt work from cold until internal workings generate enough heat indicates that primary starter cap is at fault. However all electolytics on primary read within tolerance adding to the mystery. If the power supply is heated before being switched on it works immediately without any problems. If not heated from cold it takes about 20mins for front led to remain on constantly ( 5volt standby voltage then present). The 24volt from psu at that stage not being present and only with the introduction of hot air to the psu components does the 24volt supply to the inverter become present. Very frustrating that if warmed it behaves ok so cant be much wrong with it. Any further help in this matter would be appreciated.