Checking hv

[timmy]

Checking hv on color sets is done with brightness down but for b&w sets does the same rule apply with brightness down as well for b&w sets.

[Yamamaya42]

Not so, as it says in every SAMS for color sets I have seen, check HV with brightness set at “normal level”, which to me seems logical that it would apply to BW sets for the same reason as color, as there has to be sufficient HV to keep a stable pic at a normal viewing level W/O dropping off when turned up from no brightness.

[timmy]

I’m working on this pilot tv with the d5-100 crt it works nice to see a fresh b&w picture but I’m trying to figure out how to get the screen to open up alittle more top and bottom the pot is maxed to open the screen already maybe a cap or resistor in the right place may do it but I’m open to suggestion.

[Yamamaya42]

Originally Posted by timmy

I’m working on this pilot tv with the d5-100 crt it works nice to see a fresh b&w picture but I’m trying to figure out how to get the screen to open up alittle more top and bottom the pot is maxed to open the screen already maybe a cap or resistor in the right place may do it but I’m open to suggestion.

Well, you are putting a CRT in a TV that it was not exactly made for, so there will be some changes to be made, I'm not sure if I am looking at the right schematic, pilot_tv37_sams_62-16, but if it's right, you say that “the pot is maxed to open” (R4) vertical size, if this is the case, then all you need do perhaps is raise the value of R58 to 1.1 or 1.2 meg or so, just see how it goes, or, if by chance, you have the pot at the other extreme, then lower it to 900-800k.

[Electronic M]

If you have more brightness then you need you may also be able to get more deflection by slightly lowering HV.

[timmy]

Originally Posted by Yamamaya42

Well, you are putting a CRT in a TV that it was not exactly made for, so there will be some changes to be made, I'm not sure if I am looking at the right schematic, pilot_tv37_sams_62-16, but if it's right, you say that “the pot is maxed to open” (R4) vertical size, if this is the case, then all you need do perhaps is raise the value of R58 to 1.1 or 1.2 meg or so, just see how it goes, or, if by chance, you have the pot at the other extreme, then lower it to 900-800k.

Yes it is 62-16 sams I’ll look into that

[timmy]

Originally Posted by Electronic M

If you have more brightness then you need you may also be able to get more deflection by slightly lowering HV.

It has plenty of brightness but lowering don’t really increase deflection

[timmy]

It’s a small crt so not much I need to fill top and bottom

[timmy]

Well it turns out that vert size is at little over half because I stop turning it when it stopped opening the screen so I don’t know if this complicates this or just try the resistors.

[Yamamaya42]

If it was my set, I'd try the slightly different resistor value mentioned, if it does not work, or causes a drastic undesirable effect, you can always put the original value back and try something else.

[timmy]

Originally Posted by Yamamaya42

If it was my set, I'd try the slightly different resistor value mentioned, if it does not work, or causes a drastic undesirable effect, you can always put the original value back and try something else.

Ok well I tried all different resistors and with little success not enough to leave a different resistor in seems odd a 3 inch has full screen because original but the small crt I would have thought it wouldn’t be this difficult to get it to fill in being it’s smaller

[timmy]

The picture has the letter box appearance like most cable boxes put out including mine but I ruled out that this is the best I can get with this cable box. It’s so close it’s frustrating

[Yamamaya42]

Well then, it's a step in the right direction.

What this will most likely take is someone who has intimate knowledge of this given set and vertical circuitry and how it may be better modified to the CRT you are trying to use.
Cause as it seems as for the vertical section, it's not quite working as well as the CRT that the chassis was designed to use.

This may be a result of load values, resistive and or capacitive, and is being seen more pronounced in vertical due to the lower frequency than the horizontal.
This is almost on the engineering level, and won't be easy, but I'm sure someone out there knows these things well and can offer some guidance.

[timmy]

Well it would have to be heavily modified to work this crt which I would rather not do even though it’s a b&w tube and can no longer get the 3kp4 and I doubt anyone ever tried using this d5-100 crt so I thought this tube would have been a good b&w replacement.

[Yamamaya42]

It seems that there are substantial differences between the two that would need to be addressed before it would work well it looks like.

https://tubedata.wernull.com/sheets/168/3/3KP1.pdf
http://www.r-type.org/pdfs/d5-100gh.pdf

Namely in the deflecting plates capacitive loads.
3KP1 seem to be around 8-11 pf, and d5-100 is much lower, .09-3pf? Hard to tell, not in English.
Also the deflecting plates voltages a a bit different, this is no doubt the source of the problem.