Author Topic: HP 1740A Channel B not working and flickering on A  (Read 3407 times)

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Offline PurpleAmaranth

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HP 1740A Channel B not working and flickering on A
« on: May 05, 2021, 05:06:46 am »
I picked up an HP 1740A oscilloscope recently. I replaced the fuse and it now turns on just fine, and somewhat works. However, channel B doesn't work at all (only the flat line on the graticule shows, even when probing the 1V CAL signal). As for channel A, it works except for TIME/DIV larger than .2mSEC, it flickers rapidly even when not proving anything, and the RESET light flickers along with the displayed signal.

I'm pretty new with all this. Any advice on what to check?

Thanks!
 

Online lowimpedance

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Re: HP 1740A Channel B not working and flickering on A
« Reply #1 on: May 05, 2021, 11:26:42 am »
Firstly go over to the thread about restoration of a HP 1741 by forum member 'tekfan' and read that for any tips etc.
Its in the test equipment section, and has been recently resuscitated !. Next download the manual from the link I posted in that thread. That site should have the 1740 but the 1741 is very close for the most part.
 The power supply needs verifying to be operational first. And do be careful working on the live innards as there is dangerous voltages present, know what you're doing.
Actually the very first thing to do is check for loose or oxidized interconnections which could easily be the case with gear this old. Also dry joints are highly likely in the power supply PCB so check for those then measure the supply rails  etc.
 Once the power supply has been cleared of any issues then move to the vertical input stage and check the resisters around the the hybrid for any that have drifted high, this Will cause bias shifts in the DC coupled stages and could easily cause the loss of the input signal getting to the CRT.

« Last Edit: May 05, 2021, 11:28:37 am by lowimpedance »
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Offline PurpleAmaranth

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Re: HP 1740A Channel B not working and flickering on A
« Reply #2 on: May 05, 2021, 08:01:24 pm »
Thanks for the reply! I had already checked the power supply voltages across the capacitors, and all six are very close to the reference values in the book (the scope actually came with the service manual). I just checked them again, and sure enough, they're all good.

What do you mean by the hybrid? I've been checking resistors on the "vertical preamplifier assembly" right near the input, and those seem fine, but I'm not really doing so intelligently just randomly checking values and comparing to the book... Any help with what exactly I should be looking for?

EDIT: I also just noticed that when switching to display B, the vertical position adjustment does not change the flat line position at all (it's above the graticule).
« Last Edit: May 05, 2021, 08:06:44 pm by PurpleAmaranth »
 

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Re: HP 1740A Channel B not working and flickering on A
« Reply #3 on: May 06, 2021, 12:05:05 am »
 The hybrid refers to the custom HP IC module which is A3A1 on the schematic page 8-19 (note ; unobtainium be careful measuring around it when powered, hopefully not already faulty!).
Measure the volts on TP9 and TP10 are they the same with no input signal?.  What voltage is on R36 and R61 wipers (vertical pos. pots). Does each side of those pots volts change when varying the pot position?.
 R64 and R66 100 ohm resistors, measure the volts on the end  that connects to pins 36 and 34 (of A1) wrt 0V are they the same for each channel when selected ?.
Measure the volts applied to pin 20 and then pin 1 of the hybrid amp when each channel is selected. These are the channel enable for A and/or B.
« Last Edit: May 06, 2021, 02:31:19 am by lowimpedance »
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Offline PurpleAmaranth

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Re: HP 1740A Channel B not working and flickering on A
« Reply #4 on: May 06, 2021, 02:31:55 am »
So I'm having some trouble figuring out where R36 and R61 are on the circuit board. I did however measure the rest.
With no input, I get 0V on both TP9 and TP10. With the CAL 1V into channel A, I get 0.045V on TP9, and 0 on TP10; and with the CAL 1V into channel B, I get 0.045V on TP10 and 0 on TP9. Looking at the diagrams, this seems to make sense to me.

Measuring the voltage from R64 and R66, on the ends that connect to pins 36 and 34, I get 11.67V on channel A, and identical on channel B. Presence or lack of input does not change anything. I'm not sure if that makes sense from the diagram, but it's at least reassuring that I'm getting the same on both channels.

I then measured the voltage on pin 20 and pin 1, which appear to be TP5 and TP7 respectively. Presence or lack of input does not change anything. I get 4.863V on TP5 (pin 2) whether channel B or A is selected. However, on TP7, I get 2.801V when channel A is selected, and 4.867V when channel B is selected.

Judging from the diagrams, those are the A and B on/off inputs into the hybrid. So it looks to me like the hybrid is never getting the signal to turn on channel B. Which is good I guess because it means the problem doesn't look like it's in the hybrid itself. Looks like the problem is somewhere in the circuit shown on 8-23. So thanks a lot for already allowing me to get this far!

I'll try to do some more diagnosing on my own and will update if I manage to find anything. But I'll also keep checking the forum for further advice.
 

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Re: HP 1740A Channel B not working and flickering on A
« Reply #5 on: May 06, 2021, 03:16:50 am »
So I'm having some trouble figuring out where R36 and R61 are on the circuit board. I did however measure the rest.
R36 and 61 are the POT's mounted at the front and are the channel vertical position controls.

With no input, I get 0V on both TP9 and TP10. With the CAL 1V into channel A, I get 0.045V on TP9, and 0 on TP10; and with the CAL 1V into channel B, I get 0.045V on TP10 and 0 on TP9. Looking at the diagrams, this seems to make sense to me.

Measuring the voltage from R64 and R66, on the ends that connect to pins 36 and 34, I get 11.67V on channel A, and identical on channel B. Presence or lack of input does not change anything. I'm not sure if that makes sense from the diagram, but it's at least reassuring that I'm getting the same on both channels.
Those do make sense, if the voltage on each pin (36,34) was different that would indicate DC bias issues further up which would cause problems for the Hybrid, (the 11.67V is not coming from the hybrid), and most likely just flat line traces with any input signal. (specifically R1 to 5 going high value or Q1,3 faulty).
TP9 and 10 seem consistent with the schematic.

I then measured the voltage on pin 20 and pin 1, which appear to be TP5 and TP7 respectively. Presence or lack of input does not change anything. I get 4.863V on TP5 (pin 2) whether channel B or A is selected. However, on TP7, I get 2.801V when channel A is selected, and 4.867V when channel B is selected.

Judging from the diagrams, those are the A and B on/off inputs into the hybrid. So it looks to me like the hybrid is never getting the signal to turn on channel B. Which is good I guess because it means the problem doesn't look like it's in the hybrid itself. Looks like the problem is somewhere in the circuit shown on 8-23. So thanks a lot for already allowing me to get this far!
There are a number of logic IC's between the front panel push buttons and the various select lines so those would be a good place to start looking for correct logic function.
Including shorted diodes around those IC's.
 As for the time base sweep issue thats quite possibly a mechanical issue with that switch assembly and the PCB's that form part of the switch. And that issue generally arises
from the original lubrication with age hardens and then interferes with mechanical and electrical operation. Solution is to completely strip/clean and lubricate then reassemble, making sure to complete exact
alignment for each switch section/PCB. Not a fun job but when done you will likely never have to revisit again  :P. Just make sure you take plenty of pictures of all parts concerned and
mark the shafts/locking colars and switch sections positions before starting.
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Offline PurpleAmaranth

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Re: HP 1740A Channel B not working and flickering on A
« Reply #6 on: May 06, 2021, 03:53:23 am »
Alright, so I've started looking at the logic IC's, and checking the voltages on the NAND gate chip (U3), I get the following:

Display A selected
1) 4.951V
2) 0.078V
3) 4.864V (Output to B)
8 ) 0.134V (Output to A)
9) 4.375V
10) 4.949V

Display B selected
1) 0.886
2) 4.375
3) 4.866V (Output to B)
8 ) 4.868V (Output to A)
9) 4.367
10)0.422V

So to me, all the pins look right except pin 1, as I think it should have about 4.8V when display B is selected, and not 0.886. So I guess the next step is checking the components connected to pin 1. Maybe the diodes (CR18, CR19, CR20)? I'm not too sure where those are though.

 

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Re: HP 1740A Channel B not working and flickering on A
« Reply #7 on: May 06, 2021, 04:53:06 am »
 OK make sure both CHOP and ALT are off (ie buttons are out) and then measure the logic levels on U3 pins 1, 2 and 3 again when selecting either Ch A or B.
Pin 1 should stay at 0V , pin 2 is controlled by U2a and presumably should toggle with channel selection and thus pin 3 should follow.
Channel B display button toggles pin 1 U2a CLR input with +5V or 0V, and thus Channel A toggles the PR input pin 4 the same way when selecting it.

Use the component overlay grid reference to find component locations, see image adjacent to page 8-18.
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Offline PurpleAmaranth

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Re: HP 1740A Channel B not working and flickering on A
« Reply #8 on: May 06, 2021, 05:25:46 am »
I had made sure in the previous reply that ALT and CHOP were off, but I just checked the U3 voltages again just in case and I'm getting all the same voltage values. Pin 1 is never 0V, which to me makes sense, as both inputs need to be high for the NAND gate to output a high. Pin 2 however does toggle as you said.

I just checked U2, and pin 1 is 0V when channel B is selected, and about 5V when channel A is selected (pin 5 has identical behaviour), and the opposite is true for pin 4, which is exactly as you said.

I did make an interesting discovery though. I've attached a picture of some diodes. The second from the bottom is CR19. The right half of it has lost its orange colour. Is that possibly a sign of failure? It is the only diode that looks like that. If so, is there a way to check it, or do I just replace it? Resistance across it is 1.675 kOhms one way and 3.253kOhms the other way. If that's not relevant, what else should I check? The problem does look like it's between U2 and U3.

I really wish I'd known the overlay existed before... it would've saved lots of time of checking each connection individually for continuity with the multimeter.



 

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Re: HP 1740A Channel B not working and flickering on A
« Reply #9 on: May 06, 2021, 06:30:46 am »
I had made sure in the previous reply that ALT and CHOP were off, but I just checked the U3 voltages again just in case and I'm getting all the same voltage values. Pin 1 is never 0V, which to me makes sense, as both inputs need to be high for the NAND gate to output a high. Pin 2 however does toggle as you said.
Using diagram 6 on page  8-18 pin 1 U3 has two connections, firstly via a 10k pull up to 5V and then out to the front panel push switches (ignoring CR19 just for the moment), so following the line that goes to the ALT switch which is shown in the OFF position thus the line continues up to the CHOP switch which on the diagram is shown as ON so imagine turning that switch OFF and then follow the connection, it will go to the momentary TRIG VIEW which shows the connection to be at ground (logic 0). Now with that condition CR19 cathode will be also pulled down and the anode should be at 0.6V. Which should then make U1a pin 1, U4a pin2 and U3c pin 10 also 0.6V  (logic 0). Assuming they are not schottkey
Your front panel switches might need a clean !.
 As for testing the diodes, I assume you are using a DMM ? ! it should have a diode symbol on it indicating a diode test mode that can forward bias the diode junction giving a result showing the approx. forward voltage drop directly and is a much better way to test diodes and BJT's for quick go/no go.

both inputs need to be high for the NAND gate to output a high.
Are you sure your not thinking of an AND function !!.
« Last Edit: May 06, 2021, 07:00:10 am by lowimpedance »
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Offline PurpleAmaranth

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Re: HP 1740A Channel B not working and flickering on A
« Reply #10 on: May 06, 2021, 10:54:34 pm »
Thanks for the reply and all the help so far! And sure enough, I confused NAND and AND gates. I measured everything you just talked about, but I'm not getting the same values. With Display B selected, I get 0.8V on the CR19 cathode (and 0.4V on the anode), 5V on U1 pin 1, 0.4V on U4 pin 2, and 5V on U3 pin 10. And with Display A selected, I get 5V on both terminals of CR19, 5V on U1 pin 1, 5V on U4 pin 2, and 5V on U3 pin 10.

Pressing CHOP makes two lines show up on the screen, as does pressing ALT (also, only one of CHOP, display A, display B, and ALT can be selected at a time). This would seem to indicate to me that the switches work, but I could of course be wrong.

With the DMM, I tested CR19, and I get 0.238V one way, and 0.566V the other way. Testing CR20, I get 0.570V one way, and 1.115V the other way.
And just to compare, I also tested CR12 and CR17, and I get 0.250V one way, and 0.244V the other way. On CR25, 0.525V one way and 0.742V the other way. All these diodes are of the same model (1901-0040), so I was hoping that testing more than one would show what normal bias voltages were, but that doesn't appear to be the case. I'm guessing that must be normal, I don't remember what we learned about diodes in school very well. At least, it looks like none of them are shorted out are open-circuit, although I'm not sure how well they are working.

Do you still think it's a switch issue or is there something else I should test?

I know I'm repeating myself but thanks again so much for the help!
 

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Re: HP 1740A Channel B not working and flickering on A
« Reply #11 on: May 07, 2021, 12:45:14 am »
5V on U1 pin 1, 0.4V on U4 pin 2, and 5V on U3 pin 10. And with Display A selected, I get 5V on both terminals of CR19, 5V on U1 pin 1, 5V on U4 pin 2, and 5V on U3 pin 10.
Oops I meant  U1 pin 2.

Looks like the CHOP and ALT functions are been correctly enabled , except the B channel vertical !.

With the power off using your DMM low ohms range can you measure the resistance from U3 pin 1 to 0V and confirm its connected.

Measuring the diodes in cct (no power !!) using the DMM diode function may give odd readings depending on the other component connections but usually you would get a reading when forward biasing and open (no reading) the reverse. Seems to be not the case here though.

Ok I opened up my 1740 so hopefully we can compare actual hardware to be sure. Now I have discovered that my initial assumption of the TRIG view was incorrect so ignore that part including having CR19 pulled low as a consequence sorry about the red herring.

Starting again!....

Now I have measured U3a pin1 to be at 5V for all selections of display A or B and either CHOP or ALT (excepting the possibility of pulse wave forms that I cannot see on my DMM !, most likely in CHOP etc).
And U3 pin 2 toggles low when selecting Ch A and high when selecting Ch B, and of course pin 3 follows pin 2. Thus selecting B channel in the hybrid amp.

U1a pin 1 stays at 5V for either Ch A or B but U1 pin 2 toggles low for Ch B and high for A.
CR20 has 5V either side for either Ch A or B. CR19 anode is 0.3V for Ch B selected and 5V for A.
What happens again on your scope ?

Is A versus B OFF in the Horizontal button area ?.
is R108 and R97 10K ?.

So why does pin 1 go low on your scope for Ch B... !!....hmm
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Offline PurpleAmaranth

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Re: HP 1740A Channel B not working and flickering on A
« Reply #12 on: May 07, 2021, 01:45:35 am »
Alright, so I made a bunch of measurements!

Resistance from U3 pin 1 to 0V: 6.50kΩ
U3 pin 1: 5V with Display A selected, 0.9V with Display B selected, 2.9V with ALT, 1.1V with CHOP
U3 pin 2: 0.1V with Display A selected, 4.4V with Display B selected, 2.2V with ALT, 2V with CHOP
U3 pin 3: 4.9V with Display A selected, 4.9V with Display B selected, 4.9V with ALT, 4.8V with CHOP

U1 pin 1: 5V with Display A selected, 5V with Display B selected, 5V with ALT, 0V with CHOP
U1 pin 2: 5V with Display A selected, 0.4V with Display B selected, 2.7V with ALT, 0.9V with CHOP

CR20 anode: 5V with Display A selected, 0.9V with Display B selected, 2.9V with ALT, 1.1V with CHOP
CR20 cathode: 4.9V with Display A selected, 4.9V with Display B selected, 4.9V with ALT, 4.9V with CHOP

CR19 anode: 5V with Display A selected, 0.4V with Display B selected, 2.7V with ALT, 0.9V with CHOP
CR19 cathode: 5V with Display A selected, 0.9V with Display B selected, 2.9V with ALT, 1.1V with CHOP

A vs B is OFF. Only MAIN is ON.

R108: 6.23kΩ one way, 6.40kΩ the other way
R97: 6.33 kΩ, 5.73kΩ the other way

Could these wrong resistor values be causing the problems? Also, out of curiosity, are those fluctuations in resistance values reading one way vs the other way normal? I know that theoretically they should be the exact same, but of course, that's only theory... And about the diodes, which show a reading in both directions, does that mean they're Zener diodes? We never actually touched a circuit board in school, just books! So it's pretty cool seeing these principles in action.
 

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Re: HP 1740A Channel B not working and flickering on A
« Reply #13 on: May 07, 2021, 03:56:30 am »
 The diodes are not zeners, would use a different schematic symbol. I'm sure you could find a nice symbol chart somewhere on line.
The wrong resistor values do hint at something is not right in this area and my best guess at this point would be that CR19 has gone 'leaky',
replace with a 1n4148 or 1n914 etc generic type small signal diode will do. Do measurements again after replacement.

Also get yourself a copy of the HP part number cross reference PDF, most handy finding actual part numbers for the HP coded parts!.

search up....,

Transistor - Diode Cross Reference - H.P. Part Numbers to ...

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Re: HP 1740A Channel B not working and flickering on A
« Reply #14 on: May 07, 2021, 04:04:37 am »
Just a thought, try lifting the anode leg of CR19 first and see if you can enable Ch B (don't bother with CHOP or ALT).

I assume you have an iron!. What brand of DMM are you using ?. Basic LAB tools etc

Also as a side note when I powered up my old 1740 I noticed the buttons and particularly the timebase switches needed quite a bit of 'exercising' to work of some contact oxidation after sitting for many years collecting dust  :P.
So yes all your switches will need some cleaning /lube if you intend to use this CRO regularly.
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Offline PurpleAmaranth

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Re: HP 1740A Channel B not working and flickering on A
« Reply #15 on: May 07, 2021, 04:17:28 am »
Ah true, I'd forgotten about the special Zener symbol. I'll try lifting the anode leg of CR19 and possibly replacing it tomorrow. I do have an iron. DMM brand is MAXIMUM, it's Canadian, probably doesn't exist elsewhere. I found the cross reference PDF yesterday but I'll make sure to save it. I am wondering though, how would CR19 being leaky lead to wrong resistor values?
 

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Re: HP 1740A Channel B not working and flickering on A
« Reply #16 on: May 07, 2021, 04:38:05 am »
R97 and 108 would have a leakage path to each other on that connection side and the other terminals are common to the 5V rail etc. effectively creating a sort of parallel connection but a bit more complex that a straight short.
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Re: HP 1740A Channel B not working and flickering on A
« Reply #17 on: May 09, 2021, 05:52:11 pm »
Finally got around to replacing CR19, and it works! Both channels now work, which is great! Thanks for all the help with that. Now the other issue was the flickering when I set Time/Div to anything greater than .2 ms, every lower Time/Div setting works. Do you have any idea what that could be?

And a probably dumb question: the scope came with two probes, but only one of them came with the "grabber" on it, the other one just has the pointy end. Is it possible to buyouts the grabber, are they a standard size?
 

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Re: HP 1740A Channel B not working and flickering on A
« Reply #18 on: May 09, 2021, 11:44:15 pm »
Finally got around to replacing CR19, and it works! Both channels now work, which is great! Thanks for all the help with that. Now the other issue was the flickering when I set Time/Div to anything greater than .2 ms, every lower Time/Div setting works. Do you have any idea what that could be?
As I noted earlier the problem is quite likely to be mechanical as the whole time base switch arrangement in these series scopes are not the best design mechanically speaking. The grease/lube ages rather poorly (Don't we all ! :P) and basically gums up and prevents good contact operation. You will be well served to strip down the rotary switches/PCB's and clean and re lubricate with suitable contact lube, (many choices here so search the forum for opinions aplenty  :P). Just remember to document everything before starting to make sure it all goes back with correct alignment/axial position etc.
 Next would be use contact cleaner on the push button switches and exercise them at the same time, (Only apply enough spray into the switch to do the job).

And a probably dumb question: the scope came with two probes, but only one of them came with the "grabber" on it, the other one just has the pointy end. Is it possible to buyouts the grabber, are they a standard size?
Assuming they are the original HP probes your best bet would be second/third hand on ebay etc, other wise buy a new 100Mhz probe with similar capacitance so it will properly compensate on the 1740.
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Offline PurpleAmaranth

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Re: HP 1740A Channel B not working and flickering on A
« Reply #19 on: May 11, 2021, 02:26:30 am »
Alright, so I took the whole Time/Div switch assembly apart today, which as you said, was not a particularly fun job. I sprayed the contacts down a couple times with Deoxit, made sure it all looked good, put it back together, and... it still flickers when Time/Div is greater than .2 ms. Also, when I turn it even more, it looks like the trace is "sweeping" on the screen from left to right. This happens on both channels. Any other ideas as to what to try next?
 

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Re: HP 1740A Channel B not working and flickering on A
« Reply #20 on: May 11, 2021, 05:14:43 am »
 When you say "flickers" , do you mean intensity over a scan (trace movement from L to R) ?. Would be easier to give suggestions if you were able to post a quick video even a few pictures.
Does carefully flexing the PCB's associated with the time base make any difference to the trace as well as switching the time base selection push buttons ?.
Also the alignment of the time base switch sections is critical to correct operation, just gentle side ways movement without actually changing time base speed on my 1740 is enough to upset the sweep particularly on the slower settings.
 
 The delayed time base is not selected etc I assume , so just the main only.
« Last Edit: May 11, 2021, 05:16:26 am by lowimpedance »
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Offline PurpleAmaranth

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Re: HP 1740A Channel B not working and flickering on A
« Reply #21 on: May 11, 2021, 05:46:40 am »
Here's a video of the issue:

I tried rotating the knob very slowly from one setting to the next, but that doesn't change the flickering. Pressing on any button doesn't seem to change anything either. However, pushing/flexing the top of the rear timebase PCB  (Assembly A8) towards the rear of the scope does stop the flickering up to 2mSEC. When I increase it past 2mSEC, it still flickers, but the more I flex the PCB, the better it gets, although I'm afraid of flexing too much and breaking it...

Does that mean the the contacts aren't 'making contact' properly? If so, is that even fixable?

Thanks!
 

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Re: HP 1740A Channel B not working and flickering on A
« Reply #22 on: May 12, 2021, 01:44:18 am »
 What actual setup of the timebase switches and buttons are being used (pictures!, could be handy). The brightness of the screen seems rather excessive, is that just the effect of the videoing ? or is the intensity far to high !?.  It very much reminds me of the storage version of the 1740, the HP 1741 !. We are taking about a 1740 ?   :D.
 So PCB assembly A8 seems to have an effect. Maybe the collar needs moving up a little to give a bit more compression of the switch contacts. Also check the connector XA7 for dry joints or poor contacts, this also means checking the main PCB all the timebase PCB's plug into.
I still suspect a mechanical issue rather than electronic failure given the effect of A8 which is not very well fixed in place and just kinda hangs there  :P.

These types of issues can be hard to diagnose without the hardware in front of you though, so my best guess is concentrate around the A8 PCB and interface connector.
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Offline PurpleAmaranth

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Re: HP 1740A Channel B not working and flickering on A
« Reply #23 on: May 12, 2021, 04:00:00 am »
I've attached a picture of the front, hopefully that helps. It's a 1740 for sure, and brightness is much less than it looks like in the video!

I tried moving the collars really tightly to the switch plates, but that didn't change anything. I also tried pressing the two plastic switch plates together as hard as I could with my hands, trying to apply uniform pressure all around, but that didn't change the flickering either. I therefore assume it's likely not the switch contacts? Might of course be wrong though.

I checked for continuity from each the 10 connector solder points on A7 to each of those on A8, and I get continuity for each of them. I looked at the solder joints I could see and they look fine to me, but I can't see the bottom 3 on A7 as they're too low. To look at them, I'd have to take out A7, which looks tedious to do... It sounds odd that it'd be the connector because it works on Time/Div lower than .5 mSec/Div. But at the same time, since flexing the PCB improves it, it has to be the connector or the switch contacts right?

One other thing, which I don't particularly care about but I figure I should mention just in case it's related: Occasionally, and seemingly randomly the green background will "turn off" and only the trace stays on. Sometimes it comes back on its own, sometimes I have to turn it off/shake it around a bit, and sometimes I just have to let it rest. Not a big deal since the trace is still there though.

Do you think I should take out A7 to inspect the solder joints? Is there any other way to check them or anything else to check first?

Thanks!

EDIT: I noticed that the red RESET light also flashes when the screen flashes, if that helps
« Last Edit: May 12, 2021, 04:03:47 am by PurpleAmaranth »
 

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Re: HP 1740A Channel B not working and flickering on A
« Reply #24 on: May 12, 2021, 04:32:55 am »
Make sure the delayed timebase switch is in the off position, outer dark brown ring, ie full clockwise so there's no bright up trace on the main sweep.
I noticed that the blue screen filter is missing which can also explain why the video looks too bright.
As annoying as it will be A7 might have to be removed just to be sure. However a good cleaning of all the interface connectors with deoxit would be the first step.
On my 1740 I have just found the connector on A11, (just behind A8), to be dodgy as a slight lateral movement will cause the sweep to collapse to the right hand side last 1/4 of the screen!.
So check all assemblies connections before moving onto the PCB's, scanning all over for any suspicious joints or corroded component legs etc.
Be mindful when working on the scope powered up for any shock hazards.

As for the bright green screen ,that is related to the scale illumination which is probably a noisy pot or issue in that cct. (your picture shows the control set approx. half way).
to get rid off that for the moment turn the scale illumination fully CCW.

Add some photos of the time base PCB assemblies installed in the scope and of the switches etc. Might be able to spot something else.
The odd multimeter or 2 or 3 or 4...or........can't remember !.
 


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