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 Post subject: Picked up a Tek 465B, need a little direction
PostPosted: Dec Wed 23, 2015 3:43 am 
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Howdy, newbie to the forum. Little background, I am an enthusiast about all kinds of stuff, lately electronics. Started with finding a couple vintage receivers to refurb then on to the test equipment. A local kid just sold me a 465B cheap that the crt won't come on. I figured, I am slowly getting better at troubleshooting stuff so I would give it a shot. Anyways, I downloaded the service manual, followed the troubleshooting flow chart which is awesome. The results of are:
low voltage power supply
+55V----- 41.20V
+15V----- 11.31V
+5V------- 4.55V
-8V------- -6.24V
+110V---- 97.6V
High voltage supply
-2450----- -338.4V
The flow chart then said to check the unregulated 55V, it read 53.47V on the center lug of the three, the outer two were .003V I assume that isn't the lug I want to measure? Line volt switch is correct at 115V, it then says to check caps C4429 and C4439. Looks like C4429 was replaced at some time, it has initials on the top. From what I have read, these caps are not available but a guy can re-stuff them?
So, I just need a little direction and make sure I have done all the checks I need to. Unit is just a little dusty, complete, and looks relatively taken care of. Thanks in advance!

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 Post subject: Re: Picked up a Tek 465B, need a little direction
PostPosted: Dec Wed 23, 2015 5:20 am 
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I tested the C4429 and C4439, C4439 tests good and the C4429 tests bad. Ironically, its the same one that was replaced, I think back in 2003 according to the writing inside the case. So, will that one cap throw all the low voltages out of whack? The high voltage reading is so low also, will this effect that as well?


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 Post subject: Re: Picked up a Tek 465B, need a little direction
PostPosted: Dec Wed 23, 2015 5:41 am 
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The 55V supply is used as a reference, so if it's off none of the others will be right.

For a very nice repair on the caps, look at the 465 thread.

You also need to check the ripple on the supplies. If you don't have another scope, you can use an ac voltmeter. It should be in the few millivolt range on the 55 and under regulated supplies. Sometimes the bridge rectifiers go bad, but the caps generally fail open.

You may have a problem with the HV supply, but fix the LV supplies first.


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 Post subject: Re: Picked up a Tek 465B, need a little direction
PostPosted: Dec Wed 23, 2015 6:42 am 
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Don't forget: Look the ripple on all the P.S.This oscilloscope model has a big trouble with ripple.


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 Post subject: Re: Picked up a Tek 465B, need a little direction
PostPosted: Dec Wed 23, 2015 4:00 pm 
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Look at this post, this is my 465 that I'm working on.
http://www.antiqueradios.com/forums/viewtopic.php?f=8&t=288722

If you want a couple of the PBCs, send PM with your address. This makes for a neat and easier installation.

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 Post subject: Re: Picked up a Tek 465B, need a little direction
PostPosted: Dec Thu 24, 2015 7:39 am 
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Got the cap out. Man, that was a royal pain! Thanks to dan3460 for helping me out. Looking forward to seeing how the voltages test out with the new cap. Old one was completely gone, tested about 3 nf!

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 Post subject: Re: Picked up a Tek 465B, need a little direction
PostPosted: Dec Tue 29, 2015 3:45 am 
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Update, I got the new main cap soldered in, we have a trace! I was able to use the vertical positioning knob to center the trace on the screen adjusted the rotation, all was fine. I rechecked the voltages and all were well within specs. I confidently put the cover back on then fired it up again to run a signal through it. Cant' adjust the vertical position of the trace now and get any vertical with test probe or signal generator :( . The bottom pic is with the depressed beam finder, is there just supposed to be a single dot on the screen? I just want to be sure so I can follow the flow chart that "trace is off center horizontally"? Rechecked all the voltages, all good. The only one I can't check at the moment is the high voltage one. Again thanks to Dan for all his help!

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 Post subject: Re: Picked up a Tek 465B, need a little direction
PostPosted: Dec Tue 29, 2015 4:25 am 
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The scope looks very clean, I like it.
Lets go back to basics. All voltages tested ok, right?
Then, if you put a signal on channel 1 you still get a flat trace? could you show a picture of this setup.
Here is when you need a working scope. You have to trace the signal from the input BNC into the guts of the scope and see where is fading.
Maybe someone else have an idea.

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 Post subject: Re: Picked up a Tek 465B, need a little direction
PostPosted: Dec Tue 29, 2015 4:51 am 
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dan3460 wrote:
The scope looks very clean, I like it.
Lets go back to basics. All voltages tested ok, right?
Then, if you put a signal on channel 1 you still get a flat trace? could you show a picture of this setup.
Here is when you need a working scope. You have to trace the signal from the input BNC into the guts of the scope and see where is fading.
Maybe someone else have an idea.


It was very clean, practically spotless inside, paid $50 for it. I hooked a 9v battery up and no vertical movement of the line. With the signal generator, the line flickers, just not registering up. I thought I had it beat with the new cap, so disheartening and even worse, I have to ask for more help which I hate doing. On the plus side, I am really learning a lot... :)

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 Post subject: Re: Picked up a Tek 465B, need a little direction
PostPosted: Dec Tue 29, 2015 9:39 am 
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Did a couple other tests, the calibration loop is approx 215mV (it fluctuates) when it should be 400mV. I shorted TP4177 and TP4170 and got the correct 300mv test voltage on the nose. There was a test point measurement of the preamp board I did. TP1519 and TP1319 with a 20mV signal. Supposed to be 400mV, I measured with a DMM and I got 80-650mv and I accidentally turned the vertical position knobs and far to the left or far to the right, the mV increased, at top center was the lowest. I have no idea why turning that knob would make the mV reading change so much, maybe its diagnostically important?

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 Post subject: Re: Picked up a Tek 465B, need a little direction
PostPosted: Dec Tue 29, 2015 2:04 pm 
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I would leave the calibration loop for later, I don't remember exactly I thing is a completely separate circuit.
Ok, let's do this: with the signal on channel 1, move the coupling to AC and turn the volts/div to each position. Note any changes on the line, up down, wiggle for a second, anything. Move the coupling to DC, do the same thing, note any changes. Put the signal on channel 2 and do the same thing as above.
Report back.

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 Post subject: Re: Picked up a Tek 465B, need a little direction
PostPosted: Dec Tue 29, 2015 4:13 pm 
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dan3460 wrote:
I would leave the calibration loop for later, I don't remember exactly I thing is a completely separate circuit.
Ok, let's do this: with the signal on channel 1, move the coupling to AC and turn the volts/div to each position. Note any changes on the line, up down, wiggle for a second, anything. Move the coupling to DC, do the same thing, note any changes. Put the signal on channel 2 and do the same thing as above.
Report back.

And use a low voltage AC signal, not DC from a 9 volt battery. The voltage from the calibrator loop should do, if it is working at all.

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 Post subject: Re: Picked up a Tek 465B, need a little direction
PostPosted: Dec Tue 29, 2015 4:33 pm 
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tbone8 wrote:
Update, I got the new main cap soldered in, we have a trace! I was able to use the vertical positioning knob to center the trace on the screen adjusted the rotation, all was fine. I rechecked the voltages and all were well within specs. I confidently put the cover back on then fired it up again to run a signal through it. Cant' adjust the vertical position of the trace now and get any vertical with test probe or signal generator :( . The bottom pic is with the depressed beam finder, is there just supposed to be a single dot on the screen? I just want to be sure so I can follow the flow chart that "trace is off center horizontally"?

No, the beam finder doesn't reduce the trace to a dot. It just reduces the gain on the horizontal and vertical amplifiers. It is behaving normally. Your trace is NOT "off center horizontally".

Does the vertical positioning work on channel 2?

Since it was working with the cover off, I'd suspect some mechanical problem like a pinched or disconnected wire, or a screw with the wrong length shorting something out, etc. Take the cover back off and give everything a careful visual inspection. Being unable to adjust the trace is symptomatic of a disconnect between the vertical preamp and the vertical output amplifier. The bandwidth limit switch can be a trouble spot in the older 465's, I don't know about the 465B. Try exercising the bandwidth limit switch a few dozen times to clean the contacts.

Before probing around inside, you should start by following the procedure in this troubleshooting guide from Tektronix:
http://www.sphere.bc.ca/test/tek-parts/ ... scopes.pdf

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 Post subject: Re: Picked up a Tek 465B, need a little direction
PostPosted: Dec Tue 29, 2015 4:40 pm 
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I don't think it was working with the cover off, he only got an horizontal line.
Certainty could be a disconnected cable, or de-soldered connection, but we need to pinpoint where is the problem, hence my proposed tests.

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 Post subject: Re: Picked up a Tek 465B, need a little direction
PostPosted: Dec Tue 29, 2015 4:56 pm 
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dan3460 wrote:
I don't think it was working with the cover off, he only got an horizontal line.
Certainty could be a disconnected cable, or de-soldered connection, but we need to pinpoint where is the problem, hence my proposed tests.

He did say he was able to move tehe trace with the vertical positioning control before he put the cover back on.

But yes, start with the basic tests you've described.

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 Post subject: Re: Picked up a Tek 465B, need a little direction
PostPosted: Dec Tue 29, 2015 7:24 pm 
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You could be right maybe I misread him, if true more than certainty would be a disconnected or unplugged cable.

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 Post subject: Re: Picked up a Tek 465B, need a little direction
PostPosted: Dec Tue 29, 2015 7:26 pm 
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Ok, Channel 1&2, coupling in each position, volts/div doesn't move the line even a tiny bit vertically :( . Vertical positioning does not work for either channel. I exercised the bandwidth limit switch, she got a good workout. I did download the the troubleshooting guide. It is somewhat helpful though I kind of get lost in the terminology. I am pretty sure the vertical positioner worked before I put it back together. I was so excited that the screen powered up I really wasn't paying too much attention. I really do appreciate everyone trying to help get my scope functioning. I do realize walking through a hobby enthusiast like myself can be a hair pulling experience. I went from buying my first tractor years ago to now I can completely overhaul almost every component. I promise your efforts will not be in vain and hope to one day contribute to the forum. :)


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 Post subject: Re: Picked up a Tek 465B, need a little direction
PostPosted: Dec Tue 29, 2015 7:30 pm 
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tbone8 wrote:
Ok, Channel 1&2, coupling in each position, volts/div doesn't move the line even a tiny bit vertically :(

what did you provide as an input signal?

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 Post subject: Re: Picked up a Tek 465B, need a little direction
PostPosted: Dec Tue 29, 2015 7:51 pm 
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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.

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 Post subject: Re: Picked up a Tek 465B, need a little direction
PostPosted: Dec Tue 29, 2015 9:27 pm 
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Quote:
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.


Although I have yet to see this on any of the scopes I've worked on, I'm amazed at how often this shows up. Also make sure the other ends of the wires are still attached to the PCB.

When you replaced the cap, how much did you take apart?


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