Tektronix 2230 Oscilloscope Repair Part 2: Analog

Hello Frankie! Something I forgot to tell you abpit thst broken knob off Ch-2! Hop you havn’t chucked it out yet! You can glue it back together. I think those knobs are made from ABS, (Acrylonitrile-Butsdiene-Styrine co-polymer)…here in Oz, PSTN telephones were made of this stuff…and it is damn tough and can take a lot of physical abuse. It dissolves in chlorinated solvents, particularly di-chloro-methane, (CH2Cl2) or chloroform, (CHCl3). In your case you only need the TINIEST ammount of such a solvent to use as s glue…I would glue the knob in place on the shaft…(It won’t be glued TO the shaft and you should be able to pull it off complete after the solvent evaporates). just put the broken collar back onto the switch shaft, then fet a hypodermic needle and dip it int a bottle cap with a few mililiteres of choroform in it. Capillary action will draw some chloroform up inside the hollow space inside the needle, (you might need to file or dremel the sharp tip off the needle), then just touch the tip of the needle full of solvent to the rough borken end of the knob collar…quickely, before it evaporates, slide the rest of the knob down the shaft, make sure the phase angle between the two pieces is 0 and push them together firmly…the shaft of the swotch will keep them aligned and stop the ABS “gooping” into the shaft hole st the join. Give it about two hours if you use dichloromethane and four hours if you use chloroform. You can make chloroform fron acetone and sodium hypochlorite but you will need a reflux setup you can then reconfigure to simple distillation. Outher you tubers have done it, so just go and watch them to get all the intricate details, but a 50ml bottle of chloroform on the electronics bench is always useful.

I took a look at the inpu amps on this CRO, I see that a CMOS op-amp, (TLC271, Texas Linesr Cmos) does the low frequency buffering snd the usial j-FET does the high frequency buffering st the input…clever design, I must say! I also see that the signal will reach the input from the BNCs (with the two PI attenuators missing) if yiu set it to leat attenuation…so you can get a signal into it and go along the signsl path with the 54600 whilst you wait for the attenuators to come. The fact you got the cal signal right through to the deflection plates on Ch-1 is GREAT. Try to put a sine ir triangle wave through it, this will show you if any stages are clipping or saturating. Love to see you try Ch-2 and see if U80 is OK!

Just a little history of CRO’s. The very first CRO’s had no Y-Amps, the test signals were simply applied directly to the deflection plates of the tube! This is why all REAL analog CRO’s use an electrostatic tube because its response time is really FAST! So, basically a broadbabd amplifier…”from DC to daylight” grts the signal to the plstes and the tube does the rest. Much later, when FAST ADC’s or samplers were developed, these could replace the tube as the recipients of the broadband signal..digitize it, store it and then read it out slow to be displayed on a SLOW as a wet week electromagnetic tube, sometimes as a TV raster…this is what your 54600 Does. To me, an electromagnetic deflection tube displaying an oscilloscope trace as a raster just dies not have the “charm and mistique” of a FAST, real-time high quality electrostatic tube! did you know that RAELLY old TV’s use electrostatic tubes? You will warm to the charm of the electrostatic tube. I have a HP 54600, but I arely ever use it, simply because I much prefer one of my many lovely electrostatoc tube CRO’s! But, as they say, “you need a CRO to fix a CRO”…and I agree, life would be a lot, lot harder without thet 54600 at your disposal.

Oh, can you do a short follow-up closure/debrief video on the HP power supply. Love to see it all cleaned up ind fully functioning as part of your bench gear!

Nice steps forwards, as you say somebody did a real number on this scope. Great work…..cheers.