It's just a fuse...Yes it took a lot of time.....The main reason for this was not having a good working monitor to compare things and test the board in a known working set-up. Thanks to the fact that I reworked Thwocker's 6100 I did finally have that possibility.
Anyway....I'm sure you guys are holding on to your chairs with sweat on your foreheads to learn what was wrong with it but a master never gives away his secrets.................
O well, WTF:
To refresh memories: first this deflection board produced a picture with missing picture on the far right of the screen. Later there was no picture at all IIRC.
The first thing I noticed was that the already installed LV2000 was one big mess. There was a time when LV2000s were sold as a kit and when you looked at this one it is very clear why they stopped selling them as kits
it was done by someone who didn't have the faintest idea about soldering/assembling PCBs.
Luckily Jeff Hendrix saw the posting on KLOV forum and contacted me and offered a FREE new replacement for it. IMHO that was totally awesome because someone clearly screwed up that LV2000 which was not his fault, nor was I or Béla the original buyer. This clearly shows the opinion that Jeff has about customer service, which is a 1000% contrast with what I have experienced with a seller of a competing similar product....
Anyway, I removed the old LV2000 and it was a totall loss, so I ditched it and installed the new mini version.
Installed the board in Thwocker's monitor and I got no picture at all, the spot killer came on.
So I turned up the brightness on the flyback and got a nice vertical stripe, so clearly there was no x deflection.
Removed the board and went looking for the problem. Gotta say I did all the basic stuff already so I knew caps, transistors and diodes were all ok. Checked resistors, all OK, also re soldered all the connectors so....what was left that could be the problem......
I noticed that this board had some corrosion on some parts and the fuse holders and fuses looked not great. So I measured the fuses on the soldering side and sure enough, they were all OK except for the one that is inline with the x deflection coil. That one showed a resistance, it was a bit varying but somewhere between 8 and 20 ohms. That's not a lot resistance, but it is way too much for a fuse and fuse holder.
Even so....if this fuse would have been in a power line, it wouldn't have mattered much (although it might be visible still). But since this fuse is in series with the deflection yoke, to be exact, the X coil. It DID make a huge difference.
A deflection coil has a resistance of just a few ohms usually for vector monitors so an extra resistance like this will completely shut down the deflection on that axis.
It was mostly the fuse clamps causing the resistance, but the fuse itself showed corrosion too so I decided to replace them and on both axis.
Since we are in Europe and since we prefer the smaller sized fuses here (and since I have a nice set of these fuses for my work anyway
) I decided to put in two "Euro sized" fuse holders that I once bought from RS. They include nice plastic see-through caps and the holders fit exactly in the same holes as the original US sized one's.
Installed the board back and presto, brilliant picture !
There, you go, "It's just a fuse", who would have guessed and yet another thing learned !
I put it through my usual test routine of tapping with the back of a screwdriver on the PCB all over the board to see if there are still any bad solderings or other bad contacts but it stayed rock solid.
The only thing that is a bit weird is that the spot killer LED lights up a little bit in the "pattern" of the vector being drawn. Not sure if that's normal, but the picture is absolutely perfect.
I'll do an endurance test soon and then this baby can FINALLY go back to Hungary !
