Sharp image 629 ds-r on and off sound

GMZombie

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ok i have a sharp image 629 ds-r standard/ega chassis that im trying to fix but im kinda running out of options. it sounds like the hv is coming on and shutting off. So I started to check voltages and it seems I get 168v up to c814 on the ac input side. on the other side i get nothing. i replaced the HOT originally thinking it might be it but it didnt make a difference. Can anybody help and on a side note does anybody have a service manual or schematics for this chassis?
 
??

Can you take it out and take a picture
Of the top of chassis. So we can look
For Tps...for you.I have some notes.
It always helps to take a picture of a chassis
When there's no info on the chassis
Just model numbers. Makes it harder..
To offer tips..never know we might
See the problem in the picture ..
The big filter cap should have. 168v
It comes from the bridge to the primary
of PS it iS unregulated. Voltages.
Its the secondary voltages that are regulated
Monitor them.
 
here is the pics of the top and bottom of the board. On the bottom i wrote down some levels of vdc i took at the areas of interest. Most everything i checked on the side of the power before the transformer had 170volts? i only see the one cap c814 that jumps over to the other side and on the other side of the cap it fluctuates voltage low about 6 down to 0 vdc
 

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Reading the voltages correctly?

In your picture of bottom
of chassis,shows the Hot side of chassis
the little circuit at the top left..
Need to measure the dc voltages on it using the big filter cap as a good hot ground.
then if you want to test dc on the other circuits on the chassis you have to
put your ground lead on the cold chassis ground..
Cant share the same ground for testing dc on both sides!!
Or you voltages will be way off..
Check for dc at the big diodes on the output of smps..see a reference #d801
If a chassis has the oem parts still in it the chassis
needs a cap kit first!!
 
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well i used the big filter cap as the hot ground for the hot side of the system before that transformer on the board anyways and most every place i put the test probes came up with 170-173vdc. i know you cant go past the transformer with checking the voltage from the big filter cap. when i use the big filter cap as the hot ground and check only on that side of the power supply i get 170 volts around everything it seems? d801 which is next to d807 has 170vdc? i tried to put the ground on a cold chassis spot but that gave me 0 volts dc
 
the caps would be a suspect more the
the mosfet..in primary..as long as the pins
are not broken.
shouldnt have 170vs every place you test
that makes me think your not measuring correctly.
the mosfet should only have 1 pin that has 170vs on it
not the other pins of ic..
You need more then just 170s on the filter cap.
you need a pulse from the controller to the mosfet too.

If you have no dc on secondary voltages
then rebuild your power supply first..
Unless theres a short in the chassis but in most cases
any shorts on the B+ line would make the power supply
a ticking noise,because its holding down the dc..
Id your mosfet controller Ic in the primary confirm it has voltage
on it.You look at the number on it and reserch the part Number
then look at the data sheet it will tell you the vcc pin for the ic..
If no sound from power supply then, its missing the drive pulse
for the smps..This chassis is no different from others using caps
need to replace them first!!
 
when measuring on the mosfet i was using the cap as the hot ground and checking all three pins of that fet. the middle pin didnt have 170vs on it but the back 2 did. am i measuing this wrong cause i sued the hot ground for all of that side of the transformer. it did have a chirp every no and then but that has stopped. i do have a original replacement for the hot just in case. i originally put in a nte replacement. dont suppose you have a cap kit list since i cant quite find a service manual for this chassis
 
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i just made a cap kit list and im going to try to get them all. there is quite a bit of caps on this board.
 
when measuring on the mosfet i was using the cap as the hot ground and checking all three pins of that fet. the middle pin didnt have 170vs on it but the back 2 did. am i measuing this wrong cause i sued the hot ground for all of that side of the transformer.
Please put some effort into your posts if you expect people to make the effort to reply to them.

That is not the correct way to measure the voltage of a transformer. You must measure each side of the winding.
 
i wasent taking voltage levels on the transformer at all. merely pointing out my voltage levels on the ac side of the transformer and i think this may have been misread.
 
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