Bob O Scope Part 3, Deflection Amplifiers 

nice work on this project!

Another fine video, Labguy. I bet you could program the clock on a VCR blindfolded.

Your vid has been very helpful to me in my own O'scope building... I have a (1961-built) GPO No.6B Mark I (similar to the Cossor miniatures) and it uses ECC81 dual triode diff amps. As the GPO designed it a variable resistor where you have C2 acts as the gain control. But bandwidth was only 10 kHz as frequency compensation was undershot. So I put a 500 pF shunt capacitor across this, and discovered there is a "gain" setting that is neither undershot nor overshot. Bandwidth for displaying a clean square wave has increased from 200 kHz. I now have an O'scope that runs from D.C. to over 200 kHz, and which also amplifies X and Y for doing cyclogram work. Superb !! ❤. Thank you !! ❤

One thing that could be improved about temperature stability is adding a regular silicon diode in series with TL431, to compensate Vbe of those current sources, that rises with temperature.

Great video Labguy. I really enjoy these type of in depth videos. Any danger of doing a future deep-dive video about your approach to building state machines like the ones featured in some of your earlier videos ?......Just a suggestion !

do you get a commission if we buy our boards? im following the series and wanna see if i can use your circuit to drive a 7$ 2" Russian surplus scope CRT.

I am thinking of buying a 5BP1 .... I know I will hate myself, either way. I am not going to try to build a serious scope . Possibly a clock or some vector drive curiosity. I built a 'scope back in the late 70s and used HV transformers and valves and all sorts. I plan to cheat using 24 / 2000 volt SMPS and same for the deflection rails. It could become a real time sink ..I would be better of devoting my efforts to getting better at ESP32 and Coding... but but... but ... SOB ...

Oddly enough, something called “Bobovision” already exists. Story time: In late 2000, Jiří Hodač was elected as General Director of Czech TV on a suspiciously short notice. Czech TV staff universally and publicly opposed the decision, suspecting corruption among the electors. They refused to take orders from him and his appointed head of reporting Jana Bobošíková. As a result, most reporters were fired but successfully protested the decision, prevented the new leadership from entering their office and continued to run scheduled programming, only with “STRIKE” plastered below the TV logo. Bobošíková contacted the terrestrial broadcast agency and prevented them from broadcasting news for 80% of the population while the rest continued to receive the channels via satellite, cable or rarely the internet. On Christmas Eve, she appeared as a newsreader in her own hastily produced TV news with an external agency and broadcast it over the terrestrial network instead of the studio’s version. This programming was known under the folk name Bobovize (Bobovision). In retaliation, the studio called for a protest in the following sport session. Later that week, she shut off any remotely news-related program and spread misinformation about the protest’s attendance. In the middle of Christmas holidays, she shut down the terrestrial transmission of both public TV channels for about 24 hours and ordered security to seal the studio building and lock down any toilets. People went to support the studio, lifting portable toilets, food and Christmas cookies through its windows with improvised cranes while watching their broadcast on a TV projector the technicians set up outside. As such, many reporters spent the millenial New Year’s Eve unwashed and sleeping on the floor in donated clothes while working more dedicated than ever before. Bobošíková continued attempting to thwart the protests and replace every meaningful program with ones by her non-professional staff with questionable quality but stepped down a week later when people realized her dishonesty. Later in January, the election result was appealed and laws regulating public TV leadership were updated to prevent this from occuring again. In short: Bobovision was a program by a corrupt TV leader and less than a dozen staff including teenagers whose news stories included “only 4 people and a busker showed up for the protest [which was actually the biggest in the Czech Republic to date, supported by dozens of major public figures]” and “my sister called her town’s PD and the good news is, no accidents happened on their roads today”.