Hi all,
New to the forum, shamelessly asking for help with my first post, please don't hate me! I'm just getting started with electronics, trying to learn more. I just brought my first oscilloscope, a Hitachi v-212 which I won for cheap from eBay, it was listed as untested but it was cheap and figured I could have a go at fixing it, as a bit of a learning experience.
It arrived and I really like it, I'm sure it's only a beginners scope but I have a thing for old school electronics. When it arrived channel one worked perfectly, but channel 2 seemed really compressed, existing entirely within two of the small divisions of the display, exactly as described in this post here:
https://www.eevblog.com/forum/testgear/hitachi-v212-ch2-amplifier-problem/I don't know if it's relevant but even the channel 2 vertical adjust could not move the line out of these two divisions.
I found the service manual here:
https://www.manualslib.com/manual/1171085/Hitachi-V-211.html#product-V-212and concluded that since channel 1 worked fine it must be somewhere before the 'diode gate'. At this point I may have made my first mistake and opened it up to see if i could visually spot anything looking obviously wrong. Most people suggest replacing electrolytic caps but they all look great, suspiciously good in fact, as though they have been previously replaced. The circuitry is spread out over two boards, it seems roughly along the lines of horizontal deflection on one board and vertical on the other. I removed the board with all the input preamp circuits to check for bad solder points on the back and started checking resistor values with a multimeter (stupidly not taking the components off the board first, like I said im a beginner
).
I couldnt find anything so I thought I would put the board back in thinking i would apply a signal and probe voltages along different points along the two preamp circuits and see if i could see any difference (I dont have another scope to observe signals). Unfortunately, and in typical fashion I might add, I seem to have made it worse. I now have no horizontal deflection at all, and when I apply a signal to the previously working channel one the dot doesn't move. (I assumed in the absence of a horizontal sweep I would just get a vertical line, but no). I find the lack of sweep particularly annoying as I did not even touch the board with sweep circuitry on at all. Another curious note is while I can't get any deflection from signals (or external triggers) both the X and Y position adjusts both seem to work (including the previously non working channel 2 adjust). So now I'm really confused, and I'm suspecting there's multiple faults now even though I was careful taking it apart.
So what do you guys think, have I completely wrecked it or do you think it may be salvagable? Any suggestions on where faults may lie?
PS. Sorry for the long post, but I figured the more details the better!