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I have a question. I stumbled upon these ms9 29 chassis.
If I did the mod on them, being they have vga built in for 24khz.....theoretically with the 31khz mod, would I then be able to get 31khz out of the vga cable?? 🤔
If so, this would be amazing in a Blast. Keeping the crisp 15khz of an ms9 but with the 31khz capability 😁
 

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May I know wich voltage is supplied to g1 pin with sharpnes mod? -22Vdc? I think I should have more voltage at least -60Vdc. I have modded an ms9-29su (hitachi tube) the results are not impressive but I got -22Vdc only on G1 pin.
 
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I measured around -60V.

Maybe there are different flybacks?
 
I do Not know what is wrong but clearly the mod is not working.
 

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Did you check continuity around the G1 pin and the trace you needed to cut?
After a tip from @nem , I removed the G1 cable from this spot and soldered on a wire directly to the solder point so I did not need to cut any traces.

Desolder the connector. Remove the G1 cable from the housing. Solder connector back. Solder on the G1 cable (with som extra wire) to the other point. No cut mode :)
G1.png
 
He's getting some voltage, so I doubt it's a connection issue.
 
This thing is the weirdest, yes the g1 pin traces are cut, the fly back is the same as any other ms9 unit and it Is in working order but I got only -22Vdc on G1 pin... The chassis without mod is just working but now I have just a lower brightness level with no variation in sharpness.
 
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Where did you buy your mod parts from? Did you buy the kit offered here or did you piece together the parts yourself?

Have you fully recapped your chassis just to rule that out?

Check your B+ voltage?
 
If you have a scope, see what the flyback pin is outputting. That should be pretty conclusive.
 
In this specific case it was necessary to change the R517 2.2k resistor with a 1.2ohm one to obtain -58v on the G1 circuit. Even if you completely remove r517 you won't go any further. The flyback works very well but evidently provides less voltage than expected on that particular pin.
 
For anyone that's done the 31khz mod, did you change the s correction caps or leave them alone? Based on Mike's write up I can't tell if the upsides are worth the downsides.

For reference for the 31khz mod: tried to swap s-caps (c519 with C531 and vice-versa ; original caps found on the chassis) on another chassis (MS9-29NDR23W) = black screen / protection mode. (B+ dropping)
I tried it to have a (very ?) low capacitance for the 31khz mode… but it’s too low.

So reverted back to values advised by HastuneMike.
Did you use the stock caps or the 0.68uF and 0.47uF ones on Mikes site, or some other values?
 
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