If Ch3 and Ch4 display the sine wave OK at all vertical positions but Ch1 and Ch2 have similar distortions it could point to a problem with the vertical channel switch hybrid. There are many others he

Jeff, Forgive me if I am reminding you of what you already know. If C811 was one of the very large capacitors in aluminium cans then many of those had three solder lugs with two electrically connected

The noise level displayed on sampling systems is sensitive to the setting of the loop gain for the DC balance amplifier (R231 and R232 on the 7S14). If you change the sampling diode bias voltage then

Jeff, If you want to get on with de-bugging the 7623A then you don't immediately need to remove C811 since it is not doing any harm. You should be able to find some space for a modern replacement (25m

Yes, I can remember 93 ohm coax cables with BNC connectors being thrown out by the hundreds when the Lab went from 3270s to Ethernet connected IBM PCs in the 1980s. I seem to remember that you can mat

Bonjour, I had exactly the same symptoms on Ch1 and Ch2 with Ch3 and Ch4 OK. Fixed by buying a new U400, I think about 50 - 60 Euros about 3 years ago. Best wishes, Roger

Travelling wave deflection CRTs and complete scopes were developed independently in the USA, USSR, UK and France, see the article in IEEE transactions referenced in the TekWiki entry for the 519 (you

I had a similar but less severe problem on an early 7904 (B103172) that was cured by swapping the vertical channel switch on the interface board. Regards, Roger

Leo's suggestion is an excellent idea, while you are doing this unplug both X plate wires and check that you get a sharp spot! Roger

I think that in the excitement of having the 485 working, at least approximately, we all forgot about the basic step of troubleshooting oscilloscopes - check voltage level and ripple on all low voltag

Jose, Those traces look exactly as you would expect for a normal sweep (except for the dotted line during the retrace). Are you sure the 485 is in X-Y mode with Ch1 and Ch2 inputs disconnected? Maybe

Jose, If you look at Schematic <11> Horizontal Amplifier in the manual you will see the connections to the Right hand and Left Hand deflection plates at the extreme right hand side of the diagram The

Jose, I believe you have another scope available. Can you leave the 485 in X-Y mode and measure the two X deflection plates in turn? The important question is what is the approximate frequency of the

Jose, I think there is another clue in your picture. As Jeff says the vertical bar on the left of the display is the beam spot before the sweep starts, but it is not just a narrow vertical line, it se

The most likely explanation is that the two wires from the X amplifier board to the CRT X deflection plates .have been swapped over by mistake. Take care in correcting this, the pins on the CRT do lik

Attilio, If you are buying spare parts it would be wise to get some 5nF (0.005uF) high voltage ceramic capacitors. It will probably be easier to find modern parts rated at 5kV rather than 4kV. Also ha

Attilio, I am writing this on the phone and I can't easily get schematics at the same time - so no part numbers! When you disconnect the diodes that generate the CRT cathode and grid voltages (-2.7kV)

Attilio, You say 'CR468 diode continues to boil', which implies that something is drawing too much current from the -120V supply. Which capacitor did you change? Can you measure the voltage across R46

Fabio, Check through the theory of operation in the manual. The high voltage is generated by the transformer T1199 driven by the power oscillator Q1195, the circuitry is protected by the fuse F814. Th

Ondrej, That sounds like perfectly normal behaviour. If you have a 100nsec display window for the B sweep and a 1kHz repetition rate then the beam is only turned on for 10^-8 sec every 10^-3 sec so on