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gunblade

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alright fella's, thought i would try using one of the chinese made MSU1FUS11 on a ms2931 chassis- I managed to grab 10 of these before they sold out
so all working except horizontal size pretty massive, thought i would check hv using a hv probe and meter
This flyback is giving around 18kv whereas the original gives about 28kv, even boosting the hv adjust will only give a max of 24kv on the newer chinese built

I am not going to use these flybacks, they look pretty unsafe to me
 

gunblade

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i don't know if it or not but it certainly is not matched to the original electronically, low hv can affect the way the x-ray protection works etc
 

8bitforlife

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iv seen some people get these to work are they modifying the chassis so hori isnt so wide?
 

Hatsune Mike

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Generally HV protect is to prevent HV being too high, not too low, I think. I would expect the only consequence to be a slightly dimmer image and it being too wide.
 

stj

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the HV is related to tube size - bigger screen needs higher HV.
picture over-width is an indication that the chassis was intended for a different inductance of scancoil/yoke on the tube.

having a wide pic and 15-20KV HV sounds like your using a chassis indended for a 20" monitor.
 

gunblade

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yes although its a ms2931 on a 29" crt, all ok with original flyback (27kv)but new chinese flybacks only produce 18kv with adjustment max to 24kv via the pot on the chassis
 

kuze

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There may be a variance from flyback to flyback on these Chinese replacements too, did you happen to try more than one of them?
 

gunblade

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only tried one source as yet, another sent to me that someone bought from the spanish seller on ebay arrived faulty with the g2 circuit not connected to the screen pot and therefore screen volts goes max
 

gunblade

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for the members that have replaced the nanao ms2931 flybacks have any of you tried increasing the hv pot to help with the picture size issues yet
I replaced a flyback on one at the weekend and increased the hv pot to pretty near max and the picture improved significantly but I can't prove it 100% as I do not have an original tube/yoke combo
I am sending out the chassis to the cab owner this week

in other news I have spoken with a company that are willing to remake the flybacks from a working original, only problem is this virus has shut down their manufacturing and I have no idea when they will be up and running again
 

yardley

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Sharp Image replaced mine and adjusted said pot. The picture fills the screen with no problems.
 

ArcadeClubTech

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Hi, I ordered one of these flybacks recently. The High voltage was down at 18Kv. I turned it up but only managed to make it 22Kv. The heater voltage was low so I swapped the 3.3 ohm resistor to a 1 ohm and the picture was acceptible.
Gunblade, regarding the company who will remake it...Can we be any assistance financially or otherwise? Maybe a bunch of us could help to stump up the inital outlay?
 

gunblade

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since this virus the company have not replied to any of my emails so i have no idea whats happening
 

SnakeGrunger

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I'm guessing the same issue happens on the Windy2 Toshiba PB-7534 chassis ?
 

gunblade

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I'm guessing the same issue happens on the Windy2 Toshiba PB-7534 chassis ?
if that is the chassis with the flyback with two focus pots then yes but not sure if it does the same damage, you will hear the flyback click and then picture size changes but i have only had around 10 of these chassis and only one had a failing flyback
 

ArcadeClubTech

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Been repairing a few of these lately. One fault I had was EHT was too high causing it to go into shutdown. U701 regulates the EHT by monitoring pin 11 of the flyback. D705 was faulty stopping anything getting back to U701 so it kept pushing the EHT up until shut down.
 

Hatsune Mike

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How quickly did all that happen? I have a 2931 that just immediately goes into shutdown. I swapped flybacks but there was no change, so I bet my flyback is actually okay. I'll check if D705 is there, and see if it's simply a case of bad feedback breaking regulation (unless you are talking about the Toshiba chassis, which may have principally similar regulation but completely different parts and names).
 

stj

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i dont know this chassis, but usually there is a series of zener diodes feeding back from the transformer - if one goes bad you can get shutdowns.
 
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