VOGONS


First post, by lowlytech

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Well the restore on the CTX 1451ES hit a bit of a snag when after a full recap and changing the flyback I have no HV voltage at the anode cap. The light on the front of the monitor goes from orange to green when I power up a connected PC, so it seems like everything is working with exception of HV. Testing the anode with a HV meter, the moment the monitor is turned on the meter bounces to around 10K volts, but immediately drops back down to zero.

The original flyback was a SAMPO FEA247 and when I inquired @ Tedss they told me this would be a suitable substitute

https://www.tedss.com/2023000572

Can anyone that knows flybacks confirm this replacement should have worked? The pins all lined up on the PCB, and everything seemed like a perfect fit physically with the same type and number of wires to connect to the neckboard.

My hunch feeling is to tear the CTX back down and put the original flyback back in just to test as it was working, it just had seen better days due to the C bracket being rusted in half and the sealant was all caking away. Just wanted to check if this does fix the HV issue what should I use, or should I even worry about sealing the top and bottoms of the original flyback?

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Thanks..

Reply 1 of 6, by pentiumspeed

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Get the compatible wire clamp transferred to original (serves no magnetic function except to keep ferrite core halves together), if you can take apart flyback transformer due to crumbling glue, I use clear RTV silicone with success to prevent vibrating noise and I used same to secure any kinds of ferrite cores even tiny beads on the component leads so they don't sing. Remember to scrape away and remove "formerly yellow glue used to secure components that turned brown or black" as they become conductive!

Or layers of varnish with partial drying in between works well too, slow curing epoxy thinned some works as well (done that to fix a PC power supply as I don't want anything loose to potentially vibrate. I had to dip CRT deflection yokes in marine varnish to fix the noise as well. Takes 3 session dips with partial drying in between. Would speed up if had a drying oven. 😀

This clear RTV worked so well on TVs I repair as they had lot of ferrite beads singing so I fixed them when they are serviced for repairs.

Cheers,

Great Northern aka Canada.

Reply 2 of 6, by Tiido

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There monitor is going into protection mode, I'm not sure from what though. Since HV is appearing during the brief startup then it is not likely the problem is in the transformer but who knows. It could be that the new capacitors have much lower ESR than the old ones (even when new) and the PSU section sees it as a short and goes into protection or perhaps one is inserted backwards (I have had such an effect from that).

T-04YBSC, a new YMF71x based sound card & Official VOGONS thread about it
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Reply 3 of 6, by lowlytech

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Thanks for the info on the RTV silicone pentiumspeed. Will give that a shot if I end up putting the original FB back in.

Tiido, you could very well be right. I know when I order capacitors I always get the lowest ESR I can possibly get. This monitor was filled to the brim with Teapo caps (about 50+) and while only one had a puffed top, none of them had an outright failure, but they were all over the place with their values when I tested them.

Is there a particular voltage I need to check? I do have neck glow, but don't know the main voltage the protection circuit expects (B+??) if that is what is causing the issue as I would rather leave the new FB installed if that more than likely isn't the issue. I will also go through and check polarity on the caps just to rule that out as well.

Reply 4 of 6, by Tiido

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If you don't get normal B+ (not sure how much it may be, in most of my monitors it is between 70...110V) then there's definitely something seen as a short by the protection circuit (probably the capacitor ESR related). If B+ is there then that transformer must be incompatible in some way...

T-04YBSC, a new YMF71x based sound card & Official VOGONS thread about it
Newly made 4MB 60ns 30pin SIMMs ~
mida sa loed ? nagunii aru ei saa 😜

Reply 5 of 6, by lowlytech

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I finally got a chance to solder in the original flyback on this monitor and it does produce a picture now. So the replacement flyback must not be 100 percent compatible I would assume.

Reply 6 of 6, by Tiido

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If things work with original transformer the replacement is indeed not compatible in some way. I wonder if it simply is wrong type or has tolerance that falls outside of what your board accepts.

T-04YBSC, a new YMF71x based sound card & Official VOGONS thread about it
Newly made 4MB 60ns 30pin SIMMs ~
mida sa loed ? nagunii aru ei saa 😜