sanyo 20ez troubles

elfyhead

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moved from the sticky - mods can remove my post there if needed.

so i've had this DK3 sitting in my garage for more than a year now, waiting for me to fix the monitor on it (after a long saga back then of trying to get it fixed but only partially succeeding). so i finally got some time to work on it.

it started out with washed out colors, couldn't sync, and couldn't quite focus.

so i first did the bob roberts cap kit (deluxe version). pic was then pretty good, but wavy. reading here it seemed like that's a B+ problem, and sure enough B+ was stuck at 82V and i couldn't adjust it with the pot.

i ordered IC601 and Q901 from riptor, and i had a B+ pot replacement from bob roberts from the previous attempts at repair.

i put those in last night, and now i've got a short somewhere. 0V and diode beep right at the AC input on the board (AE and AF). grrrrrr.

turns out that was because the fuse at the 120V AC had burned out. replaced that, and turned it on, and the AC fuse on the chassis flared and burned out. tried a new fuse, since the fuse that was in there was old, same result. double grrrrr.

i've gone over the solders on the three new components, and they're all good (to my eye at least).

it might be a bad diode in the bridge circuit, but how could putting in those other three components cause that?

any help is appreciated.


i really do hate this monitor.
 
nope.

made that mistake last year - won't repeat it! there's a thread on my stupidity somewhere back then...
 
D601-604 are all fine. R601 as well. desoldered and tested them. reflowed IC601 just in case. tested the B+ pot, it's fine. F302 blew again.

sad panda :/...
 
some progress.

turned out i had not put in the mylar back on the current limiter (2SD1090). sigh.

so, put that in, along with a new chip, but now i've got vertical collapse. i've replaced TR402 and TR403, and checked D401 and D403 (which are fine). switch is in "normal" position, so that's not the problem. what else should i check?
 
sanyo

chances are sd1090 has blown again.. its a short when the mylar piece is not installed. i would pull it and test it. also check the solder pads of the heat sinks, which hold tr402 and 403. and the wave is caused by the big filter cap.
 
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sorry - should have been clear. i replaced the SD1090 with one from a donor chassis because i was afraid i had blown it. i'll check the pads on the heat sinks - i didn't think of that.

it's not wavy any more (since it's in vertical collapse) :)...
 
OK - back from travel and tackled this again. very frustrating.

it's still in vertical collapse. things i have checked:

. switch is in "normal" position
. TR401 (have tried two that test good out of circuit)
. TR402 & TR403 (have tried *four* of each that all test good out of circuit)
. reflowed heat sinks on TR402 & TR403
. checked that D401 & D403 are good (desoldered from circuit)
. checked C407 & C408 - both good
. checked R414, R415, and R423 - all good
. checked VR354 - it's good
. checked for broken traces & hairline cracks - found none

i'm at wit's end on this. what else could cause vertical collapse? B+ is still at 108 V, so the circuit up to that point seems OK...
 
I have had a TON of problems with cracked traces on Sanyos. The board is thin, brittle, and poorly supported. It cracks easily when you remove it for cap kits and the like....
 
I have had a TON of problems with cracked traces on Sanyos. The board is thin, brittle, and poorly supported. It cracks easily when you remove it for cap kits and the like....

yeah, that what i keep thinking. cant tell you how many chassis ive had with vertical collapse and it was a trace. wonder if he used a magnifier?
 
yep - used a magnifier. but i'll do it again since you guys recommend it, and i'll be doing continuity checks tonight or tomorrow. while checking continuity i'll be looking at various voltages to see if that sheds any light on the matter...

i just don't think it's a cracked trace since it worked before (*and* i've inspected fairly carefully). i'm afraid i blew something out when i had the SD1090 shorted.
 
sanyo

Hey guy, sometimes those broken traces are hard to find. You may even show continuity with a meter,but if you have vert collapse and all other components check out, you have a broken trace. You may want to clean all the flux off. It hides them sometimes. Pay close attention to the corners especialy the left side. Also where anything protrudes high on the top side, like a heat sink, flyback etc.
 
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