Date   

Re: Tektronix 475

Roger Evans
 

The two neons should not light in normal operation. They are to protect the CRT from damage in fault conditions.

If you have no horizontal trace but can move the faint line horizontally then the X amplifier is basically working but the time base is not running. I assume the mode and trigger controls are set correctly.

If the time base is not running you will not generate the unblanking pulse necessary to brighten up the beam in normal operation.

Regards,

Roger


Re: DC503 repair (pwr supply and incorrect display)

um-gs@...
 

Morning ed,
I am located in Berlin, Germany. Would be great to organize something.
Greetings,
Gordian


Re: 7834 Missing Trace

Roger Evans
 

There is information about the 7A12, including manuals on TekWiki at http://w140.com/tekwiki/wiki/7A12. The site has lots of other interesting information if you delve around.

Can you clarify that each channel shows noise on the upper part of the calibrator waveform and on each channel the noise disappears when you select Invert for that channel. The reason for asking this very precisely is that there is very little circuitry which is common to both channels and also affected by the Up/Invert switches. The only suspect I have found so far is the +/-9V supplies generated on board the 7A12 itself (Up/Invert switches between +/-9V to provide current into pin 12 of U225) but measuring these requires removing the side panels so that has to wait until you can get the 7A12 out of the mainframe. In fact the value of the +/-9V supplies is critical in affecting the gain of both channels equally so this could have some impact on the calibration being wrong and also on the warm up drift which is clearly way out of spec. This is just speculation until you can get some access.

The 7A12 is also slightly unusual in having the gain adjustment for each channel on the front panel so it is conceivable that a previous owner simply 'got it wrong' in the same way for each channel.

If we are happy that the noise is being caused inside the 7A12 then there is no need to play around with timebases in the left vertical slot.

Regards,

Roger


Re: Tektronix 475

Simon
 

With the CRT removed, the two neon bulbs between the cathode and first grid still do not light and the potentials are the same on both grid and cathode (-2450V). I am not sure how the beam find works but I thought it re-biased the grid, maybe not. I think I will have to look more carefully at the grid bias circuitry.
Simon


Re: 2465 Fan Collet Thingy

Li Gangyi
 

Done. There is now a pilot hole.

I tried test printing a few pieces. You'd have to orient the part sideways
instead of the usual top down orientation to avoid it splitting, at least
with PLA.

The problem with sideways orientation is the lousy surface finish and
dimensional tolerance on home 3d printers at least. I ran mine thru a lathe
with the part slightly oversized to get it looking good. Seems like a
usable part to me. (I don't own a 2465).

On Sun, Aug 9, 2020, 4:23 AM Martin <@musaeum> wrote:

Hi Li,

would it be possible to add a guidance hole for the insert? Like some 2mm
diameter and 5mm deep...

It seems crucial the hole is drilled in the very middle of the piece for
the fan not to wobble around. Without guidance that seems rather difficult
to obtain.

cheers
Martin





Re: Tektronix 475

Simon
 

I took a photo of the tube (see album)
Simon


Re: 7834 Missing Trace

sdferg7@...
 

Ok, thanks for the tip Harvey. Still having a bit of trouble with it, doesn't seem to want to budge. I'll keep at it. Also I didn't know there was supposed to be a bottom cover, haha. Apparently my scope is missing that.

Shane


Re: Tektronix 475

Simon
 

I went ahead anyway and the HT was OK, it lit up a neon bulb through a 22MΩ resistor.
I can only think that the CRT is bad. I saw that the instrument must have been dropped on its rear end as the plastic case was cracked and the aluminum bowl protecting the CRT socket was dented. There was no damage to the socket, but I surmise that a shock like that might have damaged the CRT. I have taken it out, but cannot see anything obvious and it does not rattle. I am wondering if there is anything else I should check before buying another tube.
Simon


Re: 2465 Fan Collet Thingy

Chuck Harris
 

The slits can be done with a hacksaw blade ground
down to a slightly thinner thickness.

-Chuck Harris

Li Gangyi wrote:

Very quickly drew up a STL for people who wanna try 3D printing the plastic
bit, I believe the original part has a metal stud for the nut to thread
onto, you're gonna have to drill and tap the center for a stud.
Do let me know if you've tested it out and if it works good.

I have access to a small lathe, however I'm not equipped to do slits as of
yet, if there is interest I might get around to adding that capability.


Re: DC503 repair (pwr supply and incorrect display)

Ed (SCSKITS)
 

Gordian:

Where are you located?

I may have the part in a DC503 that I am planning to part out provided it is socketed.
I may also have one DIY replacement left that I made for the MC4335P in the DC502 which is the same part with a higher temperature rating.
My replacement was made using 1 gate SMT devices so it fit in the same space (for the parts in the DC502).

ed


Re: 7834 Missing Trace

Harvey White
 

I remember being able to pull up the plugin towards the top of the scope and then slide it out.  As has been mentioned, you can see and manipulate the remaining latch pieces from the bottom with side/bottom panels removed.

Harvey

On 8/8/2020 8:51 PM, sdferg7@... wrote:
The vertical plugin I believe is a 7A12. I did check both channels and the variable buttons are pushed in. I could use them to temporarily calibrate the scope if I need to use it I suppose. When I put them in inverse mode the trace is no longer fuzzy, it appears sharp as it should. The calibrator discrepancy does remain consistent for each V/div setting and each calibrator output, at least for any given time.

When I put my right timebase in the vertical slot and selected the blank horizontal, unfortunately I did not get a trace or readout.

I'll see if I can make some headway with the missing tabs, I can't see any of the plastic piece left in the hole, they might have broken at the point where the spring attaches to the plastic.

Shane



Re: 465M: No trace, No +5V, No +95V

Harvey White
 

Generally, you look at the inputs to the regulator inputs first, that's the bulk supplies.

Problems there can likely be a bad capacitor or open diodes in the rectifier (this assumes a non-switching style of supply).

Then you look at each of the regulator outputs and work back.  If possible, disconnect the rest of the scope from the power supply (this works if the supplies are linear, as they are likely to be), and then test.

Typically, the most obvious fault is a shorted tantalum capacitor (which are prone to shorting).  This pulls down a supply and causes trouble.

One possibility is to disconnect the high voltage (there may be a fuse to remove), and if the 95 volts is being loaded by the high voltage supply, this will let the +95 come back up.  Check across the current limiting sense resistors for excessive voltage to see if the supply is current limiting due to a short on the output.

On the neon lamps, they are there as protective devices, to limit the voltage across a circuit to the lamp's firing voltage.  I have not seen them normally on, but they can flash on power on startup and turnoff as voltages at that times can vary a lot.

Others will have more focused advice, this is general.

Harvey

On 8/8/2020 9:07 AM, @HHSIII wrote:
Am using an Air Force Service Manual (Operation and Maintenance) that I found on line as my reference. When powered up the +5V TP reads -.742 (basically zero) and the +95 TP reads +5.71V. I thought I had an issue with transistor Q742 ((Figure FO-10, PS and Interface board) and zener diode CR582 (Figure FO-9 CRT and Z Axis). Replaced both of them with no positive results. Still struggling to figure out where to go from here. Any guidance, advice or suggestion will be most appreciated.
Second question; In the power supply area (Figure FO-9 CRT and Z Axis) there are two Glow Lamps DS563 and DX564. What is the purpose of these lamps? They seem to be across pins 4 & 9 of the HV Multiplier. Do they function like a fuse? If so can they be tested like a fuse? Thank you.



Re: 475 With a bowed display. . . .Ideas?

Steph L
 

Michael, I'm not all that familiar with using Markers

So Re: "Problem is when I put my marker signal from my marker generator into the unit and set Volts/Div knob for 6-8 division vertical markers then I center the middle marker to align with the center vertical graticule line, as you move away from the center, the markers become more and more "leaned in" in at the top"

I'm assuming the Marker sig gen is fed in via Z axis coming in through P1452 Pin2 (sheet 10). There is a heap of circuitry that follows.
I guess I would be looking (with another cro) for signal folding/distorted on the positive excursions. In particular if signal is too close to +ve rail.

I was wondering what happens when you feed a short duration pulse into Ch1 for display on screen and same height?
Does the pulse behave the same way or is it only when using Markers?

Steph Lancaster
Melbourne (Aust)


Re: 7834 Missing Trace

sdferg7@...
 

The vertical plugin I believe is a 7A12. I did check both channels and the variable buttons are pushed in. I could use them to temporarily calibrate the scope if I need to use it I suppose. When I put them in inverse mode the trace is no longer fuzzy, it appears sharp as it should. The calibrator discrepancy does remain consistent for each V/div setting and each calibrator output, at least for any given time.

When I put my right timebase in the vertical slot and selected the blank horizontal, unfortunately I did not get a trace or readout.

I'll see if I can make some headway with the missing tabs, I can't see any of the plastic piece left in the hole, they might have broken at the point where the spring attaches to the plastic.

Shane


Tek 4654M; No Trace, No +5V, No +95V; Help

Harrison
 

Greetings; I am more of a mechanical guy than electronic guy. That said I am trying to troubleshoot a 465M scope that has no trace, no trace with beam finder, no +5V nor +95V. I was testing for the +95V at the TP on the left side of the A11 Interface board forward of the power supply area and the +5V on the TPs on each side of the A11 board (right side in the rear and left side outboard of the +95V TP.. Unit does power up and CRT illumination is present. I am using a Air Force Service Manual (465M Operation and Maintenance) that I found on line. I have been tracing +5 voltage from the T700 transformer forward. Things seem good before the Q742 transistor. After the transistor I was looking for +4.9V and had -0.121V (basically zero. Q742 is a 2N222 NPN transistor. My thought was to replace it to see if that restored the +5V. My issue with the +95V is I at a loss to determine where the +95V originates. I would really appreciate some "adult supervision and guidance" on both the +5V and the +95V issues and any suggestions, advice and guidance in general. Thank you very much. Stay safe and healthy. Harrison N1FAM


Re: Tek 2430 (Non-A) with Strange Problem

Lawrence Glaister
 

I have had several pieces of gear start to "stink". The cause has been leaking electrolytic caps. These have been from small 100uf/25v to larger power supply caps. One has to look very carefully at the cap for any signs of bulging tops or around the base of the pcb mounted caps for any signs of leakage. The leakage will create havoc with the pcb traces and you may end up have to jumper around damaged PCB traces. The smell could best be described as a bad case of body odour. If you have friends in the lab, everyone will be looking around trying to figure out who forgot to shower a week ago!. Equipment with exhaust fans are very good at filling the room with odour. The problem with using the nose to locate the parts is that it seems after several sniffs to saturate and no longer work as a good detector. This problem affected a lot of equipment from around 2000 including computer motherboards.
Happy hunting!

Lawrence VE7IT
Automation Engineer

On 2020-08-05 4:58 p.m., Harvey White wrote:
Depending on the smell (5$, 10$, 20$.....) it could be the RIFA capacitors on the power input.  Those are known to fail, and especially in 220 volt land.  (NOTE: I had some fail in a 120 volt application, likely same smell).  Nothing will indicate a failure *in* the scope, but you still have a potential problem.
Harvey
On 8/5/2020 6:46 PM, Mike Harmon wrote:
A few days ago, I got a 2430 from my friend at the local electronics emporium.  He said it came up, but smelled bad, so he shut it down. When I got it home, I pulled off the case, turned a fan on the CCDs and fired it up to check the voltage rail test points on the side board.  Every one measured exactly where it was supposed to be.  The Self-Test screen came up for several seconds and then the screen went immediately into a display of the A and B sweep lines.  I was able to move them all around, and when I hooked the probe to the calibrator, I got a nice square wave.

Since I wasn't familiar with the 2430, I went to the other side of the shack to pull up the user guide on the computer.  A few minutes later, I went back to the scope.  The 3 GPIB status LEDs were still lit, but there was nothing on the screen at all.  The fan was also throwing out a LOT of "scorched PCB" smell (hot phenolic).  I shut the scope down and waited a couple of hours, then tried powering it up again. Absolutely nothing on the screen.  The longer I had it powered up the stronger the scorched smell got, so I shut it down.

I spent half of last night removing the boards from the scope and carefully inspecting them for any signs of overheating.  Nothing.  No scorched spots on the boards, no visibly overheated components, no discoloration anywhere.  This morning, I put everything back together and fired it back up with the fan on the CCDs.  Every single voltage test point on the side board showed exactly on spec.  By the time the scope was on long enough to make the measurements, it was really starting to stink again, so I shut it down.

At this point, I am stumped!  I have the complete (original) 070-4917-00 (1-1/2") manual and I'm reasonably experienced at trouble shooting, but I'm sort of at an impasse.  I would have thought that anything that caused that much of a stink ought to show some physical signs of overheating somewhere, but to this point, I haven't been able to find any.

Anyone out there who has experience with a 2430?  Do these symptoms sound familiar to anyone?  The NVRAM battery measures 3.07V, but I wouldn't think that a bad battery would cause the whole screen to go blank (?).

I know the smell was there before I fooled with the scope, because the guy at the store mentioned it, but the scope did work the first time I had it powered up (for a few minutes anyway).

Your sage advice and suggestions are most welcome!
73,
Mike Harmon, WB0LDJ
mharmon at att dot net




Tektronix AWG7052 repair

kevin@...
 

Hello

Have an AWG7052 with the error below,

Analog State

Channel 1 FAIL (C200110001)
Channel 2 FAIL (C200200015)

It seems that the internal loop back signal is not being detected correctly. This is a standard test that is run anytime the unit is to be used for signal output. Also, on power up there was an alert displayed stating that the calibration factors were not in memory. This could possibly be a defective memory backup battery.

Looking for recommendations for an individual or company that may be able to repair


Re: Message to satbeginner and Saroj Pradhan re: Tektronix 2230

btorgerson@...
 

Hello,
I personally own a Tek 2235A so I like lurking and reading about these specific scopes.

-Brandon


465M: No trace, No +5V, No +95V

Harrison
 

Am using an Air Force Service Manual (Operation and Maintenance) that I found on line as my reference. When powered up the +5V TP reads -.742 (basically zero) and the +95 TP reads +5.71V. I thought I had an issue with transistor Q742 ((Figure FO-10, PS and Interface board) and zener diode CR582 (Figure FO-9 CRT and Z Axis). Replaced both of them with no positive results. Still struggling to figure out where to go from here. Any guidance, advice or suggestion will be most appreciated.
Second question; In the power supply area (Figure FO-9 CRT and Z Axis) there are two Glow Lamps DS563 and DX564. What is the purpose of these lamps? They seem to be across pins 4 & 9 of the HV Multiplier. Do they function like a fuse? If so can they be tested like a fuse? Thank you.


Tektronix 475

Simon
 

I have a Tektronix 475 oscilloscope with no display. All voltages test correctly including the -2450V supply. On pressing the beam finder I see a very faint vertical stripe which can be moved from side to side by the horizontal deflection knob. I suspect a fault in the high voltage multiplier. I am wondering if there is a way of testing it without extensive disassembly. I was thinking of sticking a hypodermic needle through the HT insulation and connecting it to a neon bulb through a large resistor. Is this dangerous or is there an easier way?
Many thanks
Simon