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Old 01-19-2020, 10:41 PM   #1
emilime75
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Default Dead NEC E655 - Can't find the service manual

Picked this up last week. It was used in an office setting and "one day it just wouldn't turn on". LED on the front of it shows no life. I've got it opened up and the first thing I checked were the 2 large rectifiers on the power supply(this was the problem on a Sharp I fixed a few months ago).

Now, either there is something odd happening with both rectifiers, or my meter is on the fritz...supply voltage always reads good at about 160vdc, but the 2 drop legs sometimes read good at about 80vdc, but sometimes I get no reading, and it seems to be random and it's happening on both rectifiers...like I'll measure once and it's good, move the meter probes around to different legs, and all of a sudden there's no voltage on the drop legs, but always shows around 160 on the input.

Shouldn't a rectifier always be "on" and always have voltage on all legs, except for ground, obviously? And why are there 2 of them? Part number TS10P06G.

Thanks.
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Old 01-19-2020, 10:49 PM   #2
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Default Re: Dead NEC E655 - Can't find the service manual

" but the 2 drop legs sometimes read good at about 80vdc" What the heck are the 'DROP LEGS'?
How about providing good clear pictures so we can see what we are dealing with?
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Old 01-20-2020, 09:02 AM   #3
emilime75
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Default Re: Dead NEC E655 - Can't find the service manual

Please excuse me if my terminology is incorrect. I'm just mostly a doofus trying to fix a TV.

The "2 drop legs" mentioned are the 2 middle leads.


Here's the spec sheet for the rectifier in question
https://www.mouser.com/datasheet/2/3...15-1114644.pdf
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Old 01-20-2020, 03:15 PM   #4
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Default Re: Dead NEC E655 - Can't find the service manual

I cannot see the pictures. Did you use the attachment in the 'Go Advanced'?

Last edited by budm; 01-20-2020 at 03:17 PM..
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Old 01-20-2020, 03:19 PM   #5
emilime75
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Default Re: Dead NEC E655 - Can't find the service manual

I didn't post any pictures. The link to the rectifier spec sheet works, at least it just did for me.
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Old 01-20-2020, 03:28 PM   #6
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Default Re: Dead NEC E655 - Can't find the service manual

I do not need the spec of the bridge.
I need to see the pictures of the board so we can see how the bridges are connected and also other circuit as well. Also need the pictures of the whole backside of unit showing all the boards.
"supply voltage always reads good at about 160vdc, but the 2 drop legs sometimes read good at about 80vdc," Why do you use DC mode on the meter when measuring the two inner pins of the bridge when they are fed by AC?
The 120 VAC (if that is the power line Voltage of your country since you do not indicate what that is) must have been present otherwise you will not have 160VDC between the + and - legs of the bridge.
What did you use for meter ground when working on this bridge section?

Last edited by budm; 01-20-2020 at 03:57 PM..
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Old 02-20-2020, 02:44 PM   #7
emilime75
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Default Re: Dead NEC E655 - Can't find the service manual

Had to step away from this for a bit, back at it now.
Any assistance would be greatly appreciated.

To recap, this guy is totally dead. No reponse from the buttons and nothing from the status LED.

https://www.badcaps.net/forum/attach...1&d=1582231278

https://www.badcaps.net/forum/attach...1&d=1582231278

https://www.badcaps.net/forum/attach...1&d=1582231278

https://www.badcaps.net/forum/attach...1&d=1582231278

https://www.badcaps.net/forum/attach...1&d=1582231278

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Last edited by emilime75; 02-20-2020 at 03:11 PM..
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Old 02-20-2020, 03:55 PM   #8
R_J
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Default Re: Dead NEC E655 - Can't find the service manual

Check the voltage on J914/J915, it should be +12 volts. If you don't have this voltage, then check the voltage across C9103, Use J931 (hot ground) and check the cathode of D9103, this should be arouns 10~20vdc

Last edited by R_J; 02-20-2020 at 04:20 PM..
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Old 02-20-2020, 06:15 PM   #9
emilime75
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Default Re: Dead NEC E655 - Can't find the service manual

Nothing on jumpers 914 and 915.

Measuring across C9103, the meter bounces around between about 9-22VDC.

J931 to cathode of D9103, the meter bounces around between about 9-22VDC.
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Old 02-20-2020, 06:37 PM   #10
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Default Re: Dead NEC E655 - Can't find the service manual

Are you getting any voltage at all across C9105? Also check the resistance of R9101 to see if it is open, it should read 0.24Ω

Last edited by R_J; 02-20-2020 at 06:40 PM..
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Old 02-20-2020, 07:02 PM   #11
emilime75
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Default Re: Dead NEC E655 - Can't find the service manual

Nothing across C9105.

R9101 measures .7 ohms, in circuit. I didn't remove it from the board to measure.
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Old 02-26-2020, 09:46 PM   #12
emilime75
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Default Re: Dead NEC E655 - Can't find the service manual

Bumping this. Hoping for some more assistance.

Thank you.
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Old 02-26-2020, 10:28 PM   #13
R_J
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Default Re: Dead NEC E655 - Can't find the service manual

Locate C9109, check the voltage across it. It looks like the ciruit is trying to start, thats why the voltage is jumping on C9103
Have a good look at the connections on the transformer, T9101 to make sure there are no poor solder connections.
There are two diodes D9104 & D9106, check that they are not shorted, they are on the back of the board near T9101.
If the diodes are ok, then I would try replacing C9103 and C9109, it could be they are bad.

Last edited by R_J; 02-26-2020 at 11:04 PM.. Reason: 715G6887
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