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Post by dummyload on Mar 17, 2016 10:22:51 GMT -5
The HTHD was likely running (HTHD led burning) before tda switch , so q101 should be fine ,failure of q101 is mostly collector emitter short = fuse blows.
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Post by dummyload on Mar 17, 2016 10:29:31 GMT -5
So you changed I101 and now I1 fix supply starts having +17v (so must have 14v on c25 this time) but HTHD not present .
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Post by radiohead314 on Mar 17, 2016 10:34:31 GMT -5
Yes it seems so. And still squeeling but no other boards present.
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Post by dummyload on Mar 17, 2016 10:48:56 GMT -5
Check if all connections on tda are still valid ,you have changed several times pcb can be damaged
Measure if d101 ,d111 ,r102 and r103 are still good to be sure.
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Post by dummyload on Mar 17, 2016 13:45:51 GMT -5
Did the test again same configuration as yesterday but measuring HTHD and it's 1,5v meaning it suposed to be off ,whithout the horizontal board (no feedback) Still the HTHD led on subboard slightly lights up but chasis is in very dark area in room so led maybe not visible in daylight conditions. Should not have used led as reference.
So chance your HTHD is working fine after all ,measure it . And put some boards in so +17v is at normal value , if the +17v is correct the other values of the fix power supply will likely be fine to. |
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Post by radiohead314 on Mar 17, 2016 13:55:15 GMT -5
Yes I just measured 1.5V exactly hthd. I think the def on signal needs to come from the horizontal?
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Post by radiohead314 on Mar 17, 2016 14:01:24 GMT -5
18.5V with video vertical and eht. No more squealing  |
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Post by dummyload on Mar 17, 2016 14:27:11 GMT -5
The def.on comes from the horizontal board and should be zero (puldown to ground) There is also the amp signal (horizontal amplitude) that one is made on smps2 I403 and I405 set with data from the controller. |
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Post by dummyload on Mar 17, 2016 14:31:15 GMT -5
Take the fuse out of the eht then sure having hv is impossible.
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Post by radiohead314 on Mar 17, 2016 14:39:18 GMT -5
Ok good point. With the hthd normal I think there is little risk for SMPS2 but I have to securely fix the cooling on the SMPS tighten the screws checking for enough pasta etc. WhenI go on with testing. I will do that tomorrow I will make mistakes if I do it now. Thanks!
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Post by radiohead314 on Mar 17, 2016 15:28:22 GMT -5
One thing I learned is that the hthd overvoltage protection only works when both the q101 and the i101 are ok. When q101 is shorted the ov signal does nothing to lower the voltage and only the fuse can stop it. Also when the tda does not work this ov signal is useless.
So I think I have had very high hthd all through the system untill the fuse blew and unfortunately that was to late.
Might be over and under voltage are there to protect when the potmeter is used for the horizontal width of the image.
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Post by dummyload on Mar 18, 2016 3:50:51 GMT -5
Q101 is a passive component , only I101 can make an overvoltage.
An overvoltage can happen with a bad tda that drives q101 the wrong way killing it and the fuse but can happen whithout the overvoltage to , a short or overload at the HTHD output can do that to.
A bad connection between sub and main board or a problem on circuit subboard that drives the HTHD or the amp output on smps2 can make the HTHD go max to.
What is the damage to the smps2 ,what's wrong with it?
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Post by radiohead314 on Mar 18, 2016 4:47:47 GMT -5
I think that if Q101 is shorted max voltage will be on primary and secondary side of the trafo. PWM can only switch it lower.
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Post by radiohead314 on Mar 18, 2016 5:42:37 GMT -5
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Post by radiohead314 on Mar 18, 2016 5:50:15 GMT -5
Damage report: One dead 2SC3998 and one dead TDA4601 (likely). Three new bought TDA4601 where broken but I bought them cheap. Lesson buy these from trusted companies. And one DOA cap. And a number of fuses.
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