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 Post subject: Re: Picked up a Tek 465B, need a little direction
PostPosted: Dec Tue 29, 2015 10:54 pm 
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dan3460 wrote:
depending n your answer to Steve, assuming that you do have a valid signal on the inputs. Normally even with no signal the line should move a fraction up or down as you play with volt/div, when doing calibration there are specs for how much movement is allowed. This brings me to believe that there is a cable or connector disconnected between the attenuator board and the vertical amplifier board. You need to open up the scope and look carefully at all the connections on this two boards. Also make sure that the connections to the deflection plates are connected (this are two tiny wire that go from the main board to the neck of the CRT.


Checked all the connections between the boards. Wiggled them, reset them. Wires show no sign of damage, everything is nice and clean. Maybe it was the horizontal positioner that I adjusted and not the vertical when I first turned it on, I just can't remember for sure. The two tiny wires are in place as well. I didn't disassemble anything when it put the new cap in, it was easily accessed.


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 Post subject: Re: Picked up a Tek 465B, need a little direction
PostPosted: Dec Tue 29, 2015 11:14 pm 
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And what was the signal that you applied to the scope when you did Dan's test?

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 Post subject: Re: Picked up a Tek 465B, need a little direction
PostPosted: Dec Tue 29, 2015 11:25 pm 
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stevebyan wrote:
And what was the signal that you applied to the scope when you did Dan's test?


I tried multiple frequencies from my audio generator, probe on calibration loop and a 9V battery. :(


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 Post subject: Re: Picked up a Tek 465B, need a little direction
PostPosted: Dec Tue 29, 2015 11:54 pm 
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It should be 4 wires on the CRT neck, horizontal and vertical plates.

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 Post subject: Re: Picked up a Tek 465B, need a little direction
PostPosted: Dec Wed 30, 2015 12:02 am 
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I just looked on my 465, for the deflection plates are two wires on the side and two wire trough a hole in the main board.

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 Post subject: Re: Picked up a Tek 465B, need a little direction
PostPosted: Dec Wed 30, 2015 12:34 am 
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dan3460 wrote:
I just looked on my 465, for the deflection plates are two wires on the side and two wire trough a hole in the main board.


I checked Dan, all 4 wires are in place. I took some large hi res photos of the boards, they are in the google link below. Maybe a trained eye will see something I do not. :oops:

https://goo.gl/photos/ns4p6kH9Z2VRdDFC8


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 Post subject: Re: Picked up a Tek 465B, need a little direction
PostPosted: Dec Wed 30, 2015 4:10 am 
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Sorry, I run out of ideas. Without another working scope this is going to be very difficult to fix. What we going to need to do is to chace the signal around the scope to see where is being lost.
By looking at the circuit I see that the signals for both channels are controlled by varying the voltage on some diodes. can you do the following: injecting a signal on channel 1 play the vertical mode, press CH1, ADD, CHOP, ALT and CH2 looking at the screen, is there any movement on the line.
The other thing I want to be sure, the line doesn't move at all when switching between all the volt/div positions.

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 Post subject: Re: Picked up a Tek 465B, need a little direction
PostPosted: Dec Wed 30, 2015 4:27 am 
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tbone8 wrote:
Update, I got the new main cap soldered in

Did you jumper all the ground pads when you replaced the filter capacitor, as mentioned by PaulAm in the other recent 465 thread?
viewtopic.php?p=2419038#p2419038

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 Post subject: Re: Picked up a Tek 465B, need a little direction
PostPosted: Dec Wed 30, 2015 5:38 am 
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stevebyan wrote:
tbone8 wrote:
Update, I got the new main cap soldered in

Did you jumper all the ground pads when you replaced the filter capacitor, as mentioned by PaulAm in the other recent 465 thread?
viewtopic.php?p=2419038#p2419038


I did indeed, I used one of Dans boards. :D


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 Post subject: Re: Picked up a Tek 465B, need a little direction
PostPosted: Dec Wed 30, 2015 6:01 am 
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dan3460 wrote:
Sorry, I run out of ideas. Without another working scope this is going to be very difficult to fix. What we going to need to do is to chace the signal around the scope to see where is being lost.
By looking at the circuit I see that the signals for both channels are controlled by varying the voltage on some diodes. can you do the following: injecting a signal on channel 1 play the vertical mode, press CH1, ADD, CHOP, ALT and CH2 looking at the screen, is there any movement on the line.
The other thing I want to be sure, the line doesn't move at all when switching between all the volt/div positions.


I spent the afternoon and evening going through the entire preamp board. I think all the voltages in the schematic were close. The one thing that did catch my eye was where there was supposed to be 0v, there was .018v on the front side and like at the black 11 hexagon and at the back at the 17 black hexagon was .030v. I noticed some variable resisters that might need adjustment to get that to zero? I attached my meter to the black 10 hexagon location just out of curiosity and got a range of 18 to 30 milivolts, it constantly fluctuated. When I hooked up my signal driver, the reading didn't seem to go up aside from the bouncing fluctuation. From that same point, I tested resistance and got different resistances for each volt/div setting. Finally, I tested resistance from that point to the bnc connector and it was OL, no continuity. Shouldnt there be a resistance reading fir that?

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 Post subject: Re: Picked up a Tek 465B, need a little direction
PostPosted: Dec Wed 30, 2015 7:02 am 
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tbone8 wrote:
dan3460 wrote:
Sorry, I run out of ideas. Without another working scope this is going to be very difficult to fix. What we going to need to do is to chace the signal around the scope to see where is being lost.
By looking at the circuit I see that the signals for both channels are controlled by varying the voltage on some diodes. can you do the following: injecting a signal on channel 1 play the vertical mode, press CH1, ADD, CHOP, ALT and CH2 looking at the screen, is there any movement on the line.
The other thing I want to be sure, the line doesn't move at all when switching between all the volt/div positions.

Dan's trying to help you, but he can't if you don't try his experiments and answer his questions.

tbone8 wrote:
I spent the afternoon and evening going through the entire preamp board. I think all the voltages in the schematic were close. The one thing that did catch my eye was where there was supposed to be 0v, there was .018v on the front side and like at the black 11 hexagon and at the back at the 17 black hexagon was .030v. I noticed some variable resisters that might need adjustment to get that to zero? I attached my meter to the black 10 hexagon location just out of curiosity and got a range of 18 to 30 milivolts, it constantly fluctuated. When I hooked up my signal driver, the reading didn't seem to go up aside from the bouncing fluctuation. From that same point, I tested resistance and got different resistances for each volt/div setting. Finally, I tested resistance from that point to the bnc connector and it was OL, no continuity. Shouldnt there be a resistance reading fir that?

Don't touch any of the trimmer potentiometers!

What signal did you apply when you "hooked up your signal driver"? (Do you mean you hooked your signal generator to the channel 2 input?)

You say the voltage at test point 10 didn't change when you applied the signal. Your meter was set to DC, correct? If you applied an AC signal, you wouldn't expect any change in DC level.

You say the resistance from test point 10 to the channel 2 input BNC connector is "OL". What is the maximum resistance that your meter can read? Was channel 2 set for DC? If it was set to AC, you would expect an open circuit. What was the attenuator setting for channel 2? If it was set to anything other than 5 mV, one or more of the attenuators was in-circuit.

Connect your audio oscillator to the external trigger input. Set it to output a few volts at a kilohertz or so. Set the timebase for external triggering. Then push the "trigger view" button. What happens to the trace?

Set channel 2 to "gnd". Select ch. 2 input. Connect your battery-powered DMM, set for DC volts, between point 29 and point 30 on the vertical switching logic. (test points TP1319 and TP1519.) Set the channel 2 vertical position control fully counter-clockwise. What is the voltage between those two test-points? Set the channel 2 vertical position control fully clockwise. Now what is the voltage between those two test-points?

If the voltage changes as you rotate the vertical position control, the vertical preamp up to that point is probably functional. Now put your meter between points 35 and 36 on the vertical output amplifier and rotate the vertical position control between the two extremes. What voltages do you measure between those two points, at the two extreme positions of the vertical position control?

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 Post subject: Re: Picked up a Tek 465B, need a little direction
PostPosted: Dec Wed 30, 2015 1:01 pm 
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tbone, one of the first things that I learned troubleshooting electronics, and I do this as a hobby, is to be systematic. You work on one part of the system at a time, make certain experiments, think about the results, then do more experiments based on those results to arrive at the defective part.
Before measuring or injecting signals everywhere, we need to establish where in the circuit is the fault. Is the attenuator board or the vertical amplifier, the mixer switch or the plate drivers. By making careful observation of what happens with the line when you switch the volt/div or pressing CH1,CH2,ALT,CHP or add, we can TRY to narrow down the offending section. If the line doesn't move at all, slightly up or down and i'm talking possible 0.1 of a division, then I would pursuit a problem at the vertical amp and not the attenuator board. If the line moves just a little, then the problem probably at the attenuator board.

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 Post subject: Re: Picked up a Tek 465B, need a little direction
PostPosted: Dec Thu 31, 2015 5:10 am 
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stevebyan wrote:

What signal did you apply when you "hooked up your signal driver"? (Do you mean you hooked your signal generator to the channel 2 input?)
Yessir

You say the voltage at test point 10 didn't change when you applied the signal. Your meter was set to DC, correct? If you applied an AC signal, you wouldn't expect any change in DC level.
Yessir, set to DC

You say the resistance from test point 10 to the channel 2 input BNC connector is "OL". What is the maximum resistance that your meter can read? Was channel 2 set for DC? If it was set to AC, you would expect an open circuit. What was the attenuator setting for channel 2? If it was set to anything other than 5 mV, one or more of the attenuators was in-circuit.
Max resistance is 40 MOhms. I don't recall if channel 2 was set to DC, attenuator was set to 5mV.

Connect your audio oscillator to the external trigger input. Set it to output a few volts at a kilohertz or so. Set the timebase for external triggering. Then push the "trigger view" button. What happens to the trace?
Absolutely nothing happens to the trace, doesn't move or flicker, nada.


Set channel 2 to "gnd". Select ch. 2 input. Connect your battery-powered DMM, set for DC volts, between point 29 and point 30 on the vertical switching logic. (test points TP1319 and TP1519.) Set the channel 2 vertical position control fully counter-clockwise. What is the voltage between those two test-points? Set the channel 2 vertical position control fully clockwise. Now what is the voltage between those two test-points?
Voltage between TP1319 and TP1519 was CCW -1.287VDC to CW 1.355VDC

If the voltage changes as you rotate the vertical position control, the vertical preamp up to that point is probably functional. Now put your meter between points 35 and 36 on the vertical output amplifier and rotate the vertical position control between the two extremes. What voltages do you measure between those two points, at the two extreme positions of the vertical position control?
Voltage between 35 and 36 was CCW -.654VDC to CW .654VDC

I am hoping this will tell us something... :oops:


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 Post subject: Re: Picked up a Tek 465B, need a little direction
PostPosted: Dec Thu 31, 2015 5:17 am 
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dan3460 wrote:
tbone, one of the first things that I learned troubleshooting electronics, and I do this as a hobby, is to be systematic. You work on one part of the system at a time, make certain experiments, think about the results, then do more experiments based on those results to arrive at the defective part.
Before measuring or injecting signals everywhere, we need to establish where in the circuit is the fault. Is the attenuator board or the vertical amplifier, the mixer switch or the plate drivers. By making careful observation of what happens with the line when you switch the volt/div or pressing CH1,CH2,ALT,CHP or add, we can TRY to narrow down the offending section. If the line doesn't move at all, slightly up or down and i'm talking possible 0.1 of a division, then I would pursuit a problem at the vertical amp and not the attenuator board. If the line moves just a little, then the problem probably at the attenuator board.


I apologize Dan, didn't mean to jump around. When I press CH1,CH2,ALT,CHP and run through all the V/div settings, nothing happens to the line. Doesn't fade, flicker, jump or anything. Just a nice straight clearly defined line.


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 Post subject: Re: Picked up a Tek 465B, need a little direction
PostPosted: Dec Thu 31, 2015 1:58 pm 
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tbone8 wrote:
I am hoping this will tell us something... :oops:

Setting the attenuator to 5 mV should provide a direct path through the attenuator. But without knowing if the mode was set to DC, we can't draw any conclusions from the resistance measurement.

The trigger view test tells us that the problem is in or after the vertical mode switching circuitry. (Without even opening the covers :-) )

The first differential measurement tells us that the vertical positioning is working going into the delay line, which also means that the vertical mode switching circuitry is more or less working.

The second differential measurement tells us that the vertical positioning is working at the far end of the delay line. Thus your problem is isolated to somewhere in the vertical output amplifier.

There are two variants of the vertical output amplifier circuit in the Tek 465B. Is your serial number above or below B030000?

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Last edited by stevebyan on Dec Thu 31, 2015 2:17 pm, edited 1 time in total.

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 Post subject: Re: Picked up a Tek 465B, need a little direction
PostPosted: Dec Thu 31, 2015 2:15 pm 
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Regardless of the serial number, the waveform points are at similar points in the circuit. So you can continue troubleshooting by measuring DC between 37 and 38, 39 and 40, and 41 and 42 at both extremes of the vertical positioning control.

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 Post subject: Re: Picked up a Tek 465B, need a little direction
PostPosted: Dec Thu 31, 2015 2:54 pm 
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No problem tbone. Follow Steve's procedure and get back to us.
The vertical switching is after the attenuator and vertical amp. Because the switching there different paths and loads to the plate drivers, so I will concentrate on a problem after the switching circuit.

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 Post subject: Re: Picked up a Tek 465B, need a little direction
PostPosted: Dec Thu 31, 2015 8:02 pm 
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stevebyan wrote:
Regardless of the serial number, the waveform points are at similar points in the circuit. So you can continue troubleshooting by measuring DC between 37 and 38, 39 and 40, and 41 and 42 at both extremes of the vertical positioning control.


Ok, I think I have it figured out.
37 to 38: .013VDC, no change with knob
39 to 40 -.004VDC, no change with knob
41 to 42 .881VDC, no change with knob

Would that mean the chip 155-0078-10 vertical amplifier microcircuit is bad?


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 Post subject: Re: Picked up a Tek 465B, need a little direction
PostPosted: Dec Thu 31, 2015 9:18 pm 
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tbone8 wrote:
Ok, I think I have it figured out.
37 to 38: .013VDC, no change with knob
39 to 40 -.004VDC, no change with knob
41 to 42 .881VDC, no change with knob

Would that mean the chip 155-0078-10 vertical amplifier microcircuit is bad?

What serial number range is your instrument?

Assuming it is below B030000, it could be the bias circuitry for U2210, U2210 itself, the level shifting zeners after U2210, or some fault in U2260 that loads down U2210's outputs.

Measure all the DC voltages indicated on the schematic around U2210 and the input to U2260 and report any results that differ from the schematic annotation. Also check pins 4 and 10 of U2210 for the -8 volt power supply.

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 Post subject: Re: Picked up a Tek 465B, need a little direction
PostPosted: Dec Thu 31, 2015 9:27 pm 
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stevebyan wrote:
tbone8 wrote:
Ok, I think I have it figured out.
37 to 38: .013VDC, no change with knob
39 to 40 -.004VDC, no change with knob
41 to 42 .881VDC, no change with knob

Would that mean the chip 155-0078-10 vertical amplifier microcircuit is bad?

What serial number range is your instrument?

Assuming it is below B030000, it could be the bias circuitry for U2210, U2210 itself, the level shifting zeners after U2210, or some fault in U2260 that loads down U2210's outputs.

Measure all the DC voltages indicated on the schematic around U2210 and the input to U2260 and report any results that differ from the schematic annotation. Also check pins 4 and 10 of U2210 for the -8 volt power supply.


Mine is the newer above B030000


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