Calling on a monitor wizard: Sanyo 20EZ no raster

WannaTheater

Member
Joined
Jul 11, 2011
Messages
256
Reaction score
12
Location
Florida
I picked up a DKJR a few weeks ago where the prior owner tried to do a cap kit and flyback replacement. After cleaning up some bad work, re-running some traces where pads lifted, verifying continuity with meter, etc, I fired it up. Dead. It smelled like plastic heating up, so I shut it down. Found the HOT had the yellow and black wires switched. After I corrected this (HOT still seemed to test good out of circuit with meter), R473 lit up orange. I found a TINY barely visible solder bridge between C302 to the C453.

I then couldn't get B+ to 108VDC... it was either below 90VDC or about 115VDC. The metal pot was very flaky.

Today I replaced the following:
C302 (tested good with meter)
C453 (tested good with meter)
D454
R473
T901 (which tested good out of circuit)
IC601

Now I've adjusted B+ to a solid 108VDC. I have 16DVC at J7. I have neck glow. But I have nothing on the screen. When I switch the "Test" pot, I still get nothing. I can crank up brightness and subbrightness, but get nothing. When I crank up SCREEN all the way, B+ jumps to 136VDC+... I assume that it is going into HV shutdown.

The only time anything comes on the screen is when I switch the power off- A brief flash of colors comes on the middle of the screen.

The monitor also has an separate video input board that mounts on the cage that covers the flyback. I have another cable going from NON INVERT OUT, to the chassis main board. I hope that is correct! (it is also odd that this board has a power header, with only one wire connected... is this normal?)

I am running this without the audio board connected, which has its own set of issues I am working on.

Any advice on where to go from here?
(I am now wondering if the flyback got damaged with the HOT reversed, or the short pulling current across R473, but I have virtually no experience with monitors...)

Thank you!
 
It took me quite a while to learn the complexity around adjustments with my Sanyo 20EZ. I sent mine off to Buffett about 6 months ago, and he did a great job repairing the chassis and getting everything updated. Might be worth going that route if you're unsure...replacements are getting hard to find.

Jason
 
this sounds like the previuos owner did a really bad job! you will have to go over everything and check for bad solder, broken traces, bridged solder, backwards cap, ect. man made issues are always so much harder to track down then normal failures.
 
Thanks Paul- that's when I've been doing.
Lifting legs, testing components, ringing out traces. Loving my Hakko, which makes it easy.

I am leaning toward he damaged the new FBT-
There is some white dried goop on it- perhaps it got damaged internally.
 
WannaTheater said:
Thanks Paul- that's when I've been doing.
Lifting legs, testing components, ringing out traces. Loving my Hakko, which makes it easy.

I am leaning toward he damaged the new FBT-
There is some white dried goop on it- perhaps it got damaged internally.
Click to expand...

I would doubt that this damaged the flyback. The white goop could just be dried epoxy from the manufacturer. But you might want to make sure that the flyback was installed properly, specifically was the focus tower installed right since you usually have to use the old one on non OEM flybacks. I am surprised your HOT is still good though, you may want to check it again. And you are checking the fuses in between tests, right? There are 2.
 
I did originally remove the flyback to clean up the soldering work. There was lifting on 1 pad, and even though it rang out correctly, I still added a jumper wire.
- The FOCUS leads were already connected to the control plate and look correct
- I needed to solder the SCREEN leads onto the control plate posts. I assumed (hopefully correctly) that the polarity of the SCREEN wires when connecting to the posts did not matter. (I didn't have a photo to compare, just the schematic- And the schematic doesn't show the control panel and leads). The connection seems OK, since when I turn up SCREEN all the way, it will go into HV shutdown.

Fuses are good and have yet to pop (always tested out of circuit).

The HOT tested good out of circuit with a meter (set to Diode). Not shorted, as I had expected. And two pairs had the typical expected diode voltage readings.

On another note, I just finished rebuilding the audio board- Replaced all caps, two transistors, and a couple resistors that were cooked. Audio now works, and sounds good. This also helped me verify that the power circuit on the main chassis is OK.... as is the game board :)
 
Last edited:
I measured from R466 to ground. Based on the schematic, I assumed it would be showing something, but it was showing nothing (on AC volts, DC volts, or Hz). So I start thinking maybe the sync generator/separator chip is held in blanking, etc.

Before I turned it on again, I measured from B to E on the HOT, and they were both connected to ground. This makes sense, as the schematic shows them connected through an inductor/coil while in circuit. But when I powered the game on, I notice is that the CASE of the HOT is at 108DVC- Is this to be expected?
 
i would continue to make sure ALL your traces are connected to their pads.

same with looking for any solder bridges.

i would not think crack in the PCB since you get a brief flash of the image when turned off.

it sounds like a resistor is out of spec somewhere maybe.

with all the botched work on this chassis by the previous owner it could be hard to track this issue down.

good luck on your hunt.

let me know if you throw in the towel.

Peace
Buffett
 
Spent a bunch of time inspecting, lifting legs to verify components, continuity testing, etc. Was about to give up when I found R479 to be puffed up. When I removed it fully, it basically crumbled.

Will be ordering some parts today to replace.
 
Replaced R479 (big shout out to Paul400 for hooking me up with some resistors)
I had high hopes, but no change. From what I can tell, something is keeping the sync separator IC from oscillating the horizontal sync. HOT collector stuck at 130VDC.
 
In taking a step back, here are some things I have noticed.
1) unless my meter is bad, my input voltage (plug in cabinet) is at 109VAC, not 100VAC. This is without the monitor even being plugged in.
2) my collector voltage on the HOT is 139VDC, not 130VDC like all the troubleshooting docs say

Is this OK?
 
Thanks Buffett, for confirming.

I think I may have found the issue- C472, which was replaced with the cap kit, is not ringing out correctly. It also happens to be connected to R479, which was cooked. Will update once it is replaced.
 
Well, I thought I had this nailed down. I replaced C472, which was testing as OPEN.
This cap ties the primary of the FBT to ground (pin 11). Alas, no change. When powered on, I can hear high voltage is going to the CRT, but it sounds weak.... (not the heavy static crackle when working monitors power up, if that makes any sense)

The only change now is that when SCREEN is cranked all the way up, it does not go into HV shutdown. B+ remains stable at 108.4.

At this point I am wondering if the FBT is the issue.
 
most Sanyo's will not have a "strong" startup/crackle.

if you have HV i do not think your fly is bad yet.

Peace
Buffett
 
Removed D451 to see if this was indeed a HV shutdown issue. Now I can hear the frequency of the HOT. But still no picture.

Reinstalled D451. Now monitor immediately goes into HV shutdown (can hear click, and B+ is 139ish). And now there is no neck glow.
 
Finally solved. Huge shout out to Paul400 for identifying the issue. I was able to stop by his house earlier today with monitor in hand (he fortunately doesn't live that far away)

From an earlier post in this thread:
- I needed to solder the SCREEN leads onto the control plate posts. I assumed (hopefully correctly) that the polarity of the SCREEN wires when connecting to the posts did not matter. (I didn't have a photo to compare, just the schematic- And the schematic doesn't show the control panel and leads). The connection seems OK, since when I turn up SCREEN all the way, it will go into HV shutdown.

My assumption:
I assumed the SCREEN dial is a pot... a variable resistor.... with two leads.... no polarity.
I even rang it out with my meter.... it acted just like a normal variable resistor...
In both directions. Ohms went up in one direction, and down in the other. It worked the same way with meter leads reversed.

THIS WAS AN INCORRECT ASSUMPTION. Polarity matters on the SCREEN pot. Paul swapped the red and the black, and the thing fired right up. Some degaussing, and adjustments, and this is just about ready to roll.

(I still need to put the HV protection zener diode back in, but hoping everything in the protection circuit is OK... if not, it should much easier to identify with a working monitor.)

Thanks everyone for all the replies. And thanks again Paul400, for fixing in about 5 minutes what I have been trying to fix for many many many hours.
 
HV protection circuit back in place and no issues. Monitor is looking great-
Time to start the cabinet restoration!
 
You must log in or register to reply here.

Similar threads

conrad
Scrolling on a Sanyo 20EZ
Replies
5
Views
289
conrad
conrad
Sanyo 20EZ help - DKong
2
Replies
37
Views
1K
Fenneys
kentmurphy
Sanyo 20EZ - Broken Ring Tabs
Replies
2
Views
127
kentmurphy
kentmurphy
kentmurphy
Sanyo 20EZ - What's inside the yoke?
Replies
2
Views
126
rittwage
CakeLancelot
Post-capkit Sanyo 20EZ width issue
Replies
6
Views
280
CharlieG
CharlieG
Back
Top Bottom