Wikipedia:Reference desk/Archives/Miscellaneous/2014 August 21

= August 21 =

Repair oscilloscope
The TRACE SEP control on my oscilloscope is dead. Can someone point it out on the circuit diagram? The oscilloscope is 100MHz dual-beam with delayed trigger and otherwise works fine. Here you can download the circuit (click "Descargar Meguro MO-1255.rar"). It comes as a .rar file which contains .pdf files. Here are pictures of the oscilloscope. 84.209.89.214 (talk) 23:29, 21 August 2014 (UTC)
 * The TRACE SEP pot is at the lower right of the "Vertical final amp" diagram. The resolution of the scan isn't very good, but I think its value is shown as 5K.  When you say "it's dead", what do you mean?  If turning it doesn't do anything, I'd first suspect that the knob has come loose on the spindle.  Remove the cap from the knob, and tighten the collet using a (large) screwdriver.  Otherwise, it should be fairly simple to find a replacement. Tevildo (talk) 08:02, 22 August 2014 (UTC)
 * Thank you, I've got it. The knob and spindle are mechanically sound. When I set up a delayed internally triggered scan, the B-scan part of the A-scan brightens as expected but TRACE SEP fails to separate the scans vertically. The only reaction to full rotation of TRACE SEP is a tiny vertical shift (by about a trace thickness) of all the traces together. Otherwise it's dead. 84.209.89.214 (talk) 12:07, 22 August 2014 (UTC)
 * No problem. I would guess, in that case, that the +15V wire has come off the pot, so that turning it only changes the total load on the -8V rail rather than the bias voltage on Q313. Check that the wires are still connected (give them a little pull if they're covered with some sleeving) - if they are, the pot itself may be faulty, so it's time to get the DVM out.  I naturally assume you know how to work safely on mains-powered equipment... Tevildo (talk) 17:21, 22 August 2014 (UTC)


 * (I'm sorry, I don't know anything about fixing oscilloscopes. But I wanted to point out that your linked video is without a doubt the most sentimental technology video I've ever seen. People might want to take a look, even if they can't help answer the question. I will also assume that you are the creator of the video, and wish you success in your endeavor to restore your faithful companion :) SemanticMantis (talk) 20:27, 22 August 2014 (UTC)
 * For scope porn, one can't beat the Tektronix 453. Not as atmospheric a video as the previous post, admittedly. Tevildo (talk) 20:50, 22 August 2014 (UTC)
 * The video poster "VintageTechnik" is not me and just happens to have the same oscilloscope model as mine and earnt a scathing comment from "MrCuddlyable3" here. Meguro no longer make the MO-1255 oscilloscope which resembled the Tektronix 453A and 465B models. I have a DVM but anticipate using the scope to probe itself when I get the case off. 84.209.89.214 (talk) 22:47, 22 August 2014 (UTC)