Diamond Monitor 1997 (ACER 7279G) Help
I am attempting to fix this 19" monitor. I have found a schematic on a
Russian site :-) part of the eht section is scanned and viewable here http://users.tpg.com.au/users/verdons2/7279.htm Symptom: no EHT /green light on. I have disconnected the smps from main board and it runs ok. I have checked caps around Hor out and they look ok with regards to ESR. I can find no bad joints around the FBT or HOT drive Txfmr. I checked the FBT and it rings well, the 3000p cap on the eht lead measures ok. I pulled out the Q313 HOT BU2520DX and replaced it with a BU508D (had on hand) and also Q304 an IRF640 (was 634) and tried a 740 (on hand). Also I replaced the diode D305 and the 4 470p/2kV caps across the HOT's C-E. I got a picture for about 5 secs, there was a short blink and then back to nogo status When in this condition and I power on: the HORV signal from IC304 tda4855 driving this circuit appears for a few seconds then stops. There is a signal on the BU2520 base before HORV stops. I can see a switching signal on Q304's gate. 45V on HOT emitter There is a slight fizzing sound...perhaps heating of the FBT primary? Should I replace the HOT and Mosfet with the correct type and see what happens? Is there some other component I should check before I do this? Thanks in advance Russell (wish I had a variac!) |
Diamond Monitor 1997 (ACER 7279G) Help
I must go by your description. I have not worked on the model you have. I
am sure, you need the correct HOT for sure. The flyback most likely has to also be replaced. I have seen this before, but not in the make of monitor you have. -- Greetings, Jerry Greenberg GLG Technologies GLG ========================================= WebPage http://www.zoom-one.com Electronics http://www.zoom-one.com/electron.htm ========================================= "Verdons" wrote in message ... I am attempting to fix this 19" monitor. I have found a schematic on a Russian site :-) part of the eht section is scanned and viewable here http://users.tpg.com.au/users/verdons2/7279.htm Symptom: no EHT /green light on. I have disconnected the smps from main board and it runs ok. I have checked caps around Hor out and they look ok with regards to ESR. I can find no bad joints around the FBT or HOT drive Txfmr. I checked the FBT and it rings well, the 3000p cap on the eht lead measures ok. I pulled out the Q313 HOT BU2520DX and replaced it with a BU508D (had on hand) and also Q304 an IRF640 (was 634) and tried a 740 (on hand). Also I replaced the diode D305 and the 4 470p/2kV caps across the HOT's C-E. I got a picture for about 5 secs, there was a short blink and then back to nogo status When in this condition and I power on: the HORV signal from IC304 tda4855 driving this circuit appears for a few seconds then stops. There is a signal on the BU2520 base before HORV stops. I can see a switching signal on Q304's gate. 45V on HOT emitter There is a slight fizzing sound...perhaps heating of the FBT primary? Should I replace the HOT and Mosfet with the correct type and see what happens? Is there some other component I should check before I do this? Thanks in advance Russell (wish I had a variac!) |
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