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Hello again Have a working Tek SA 492, SN B05 1984 , 2500 hrs. to check power supply for RIFA caps, lytic and tants, the. PSU remove procedure in manual is vague on the location of connectors before you pull it. Any tips or diagrams ? caps to replace or change ? Your thoughts and advice appreciated Many thanks Jon

I have a 455 with a defective HV Multiplier (part of U550). The TEKTRONIX specification calls for a 1 1/2 times multiplier with a "3M Series Resistance". I have built a 1 1/2 times multiplier (that is pretty simple), but am unsure of how to properly get that 3M of series resistance? If this is a simple matter of soldering a suitable sized resistor into the Anode lead? What watt rating for the resistor? I have a 3M Ohm carbon composite resistor, but it is only 1/2 watt. I'm afraid this resistor is too small to do the job. I suppose I just do not completely understand the principals involved? How to get the right answer is the bigger question? -- Michael Lynch Dardanelle, Arkansas

I need to restore my Tek 130LC meter scale - the red has unsurprisingly 95% disappeared. I've crafted the artwork, and boy did that take some time as each of the five scales is cunningly non-linear and no two appear the same! It's now about print and apply, but apply to what? I'd rather keep the original aluminium-backed scale safe as I may have a way to restore it without removing/affecting the existing visible print. What I do have to hand is plenty of suitably thin brass sheet. I'd need to buy aluminium in. Am I correct that brass is equally suitable, will have an equal impact on meter calibration/accuracy, but might possibly confer slightly more damping? However, having spent SO long producing the exact artwork, would be shame to undo that with the wrong material! I just don't have the practical experience here, so would value your thoughts. Thanks.

Hello! Sometimes ago i obtained a TDS640A Acq. board. I found on w140.com Wiki, what TDS544A uses the same Proc. board as TDS644A. And bought it too. Today i have a TDS544A Proc. which working with TDS540A Acq., but when i try to connect TDS640A Acq, processor doesn't see it and give me an error. I think, i need to flash TDS640A firmware to my Proc. board. It right? Second question: I bought a PCII/IA GRIB board to make field adjustments later. This ISA board runs on PIII with Win98SE. I thought I could flash the oscilloscope using this board, but I read that the macbook can only work normally in Win7/10. Does anyone know about Win98/DOS Tek flasher? Thanks, Peter

Peter Keller just provided me with a revision to the 4th paragraph of my original explanation for why the brightness of a well-used CRT first brightens then dims before finally brightening again as the intensity control is increased (known as "Double Peaking"). Here is the updated explanation. ----------- Under ordinary circumstances a cloud of electrons boil away from the surface of the cathode as a result of the heater heating it to incandescence in a vacuum. This is sometimes called the Edison Effect because he noticed it first in light bulb filaments. It is more correctly called Thermionic Emission. This cloud forms around the cathode and is known as the space charge region. The cathode is intentionally coated with a material that lowers the work function. The work function determines how much energy will be required for an electron to leave the surface of the cathode and join the cloud of electrons surrounding the cathode. A low work function means more emission. In ordinary circumstances the space charge region is the source of the electron beam, not the cathode. The cathode is "filling" the space charge region with electrons that will be attracted to a positively charged surface and ultimately focused along the way into a tight beam. As the cathode ages the chemical coating used to lower the work function wears out. The space charge cloud can no longer provide enough electrons to form a bright beam. After depletion of the space cloud, the current is being drawn from the damaged center area of the cathode coating which decreases available current. Further increasing the intensity control (lowering the negative grid bias) begins to draw current from the undamaged periphery of the cathode and increases beam current again but with a resulting larger spot size. ----------- Dennis Tillman W7pF -----Original Message----- Sent: Saturday, February 23, 2019 9:28 AM Subject: RE: [TekScopes] Mechanism of CRT Double Peaking Hi Fabio, Your explanation is plausible except for one more bit of vacuum tube physics that has to be taken into account: Under ordinary circumstances a cloud of electrons boil away from the surface of the cathode as a result of the heater heating it to incandescence in a vacuum. This is sometimes called the Edison Effect because he noticed it first in light bulb filaments. It is more correctly called Thermionic Emission. This cloud forms around the cathode and is known as the space charge region. The cathode is intentionally coated with a material that lowers the work function. The work function determines how much energy will be required for an electron to leave the surface of the cathode and join the cloud of electrons surrounding the cathode. A low work function means more emission. In ordinary circumstances the space charge region is the source of the electron beam, not the cathode. The cathode is "filling" the space charge region with electrons that will be attracted to a positively charged surface and ultimately focused along the way into a tight beam. As the cathode ages the chemical coating used to lower the work function wears out. The space charge cloud can no longer provide enough electrons to form a bright beam. The user turns the brightness up to compensate. This increases the positive voltage attracting the electrons. Eventually the user increases this positive voltage to the point where the space charge region is completely depleted and electrons are being stripped directly off the cathode increasing the brightness temporarily. This is not good. There is a way to extend the life of the cathode in a CRT as most people who worked in a TV repair store are familiar with it. I recall it as "rejuvenation". It is a simple process. If you increase the voltage going to the heater this will heat the cathode to a very high temperature which will burn off the weakly emitting surface of the cathode exposing fresh chemical coating from underneath. There is the risk of burning out the filament that must be considered when you do this. There is another variation of this which boosted the filament voltage on

I recently acquired a second TDS-380 that was "working" - meaning with an signal at the output it displayed a trace on the screen. But the 'scope displays an offset with no input signal. With no input to either channel, Channel 1 measures a mean voltage of about -1.95 volts on the 2 volt scale, and Channel 2 a mean voltage of about -2.55 volts on the 2 volt scale. These measurements vary with the vertical scale setting. I ran through the calibration procedure, and then measured the 5 volt calibration signal. For sweep rates of 25 uSec per division and slower (not fit to screen mode) the amplitude measures about 5 volts. When I increase the sweep speed to 10 uSec per division the displayed waveform and measured amplitude almost doubles. I have replaced U402, the acquisition RAM, as that has been found a problem elsewhere, including my other TDS-380 which had similar problems that were corrected by replacing that RAM. No change for this 'scope. I have the manual with schematics and layouts, but there is no circuit description in the manual. Is there a circuit description available somewhere? This would certainly be helpful in trying to isolate the problem to a block. on the Root Sheet - block diagram. I don't believe there are any surface mount electrolytics on the mainboard. On the other hand, I have software to communicate with the 'scope over the RS232 port, and discovered eleven open traces on that board that required jumpers before the computer would communicate with the 'scope. Any assistance will be appreciated. Gary Appel

I got this piece new-in-the-box a last year and I've finally powered it up & checking it out. Even the battery seems ok. It must be time for me to start digging through the history of the group and this scope. First need to see if it can talk to my computer. Ron

Hi all, I have a very unstable 7A15A Plugin ... for example, signal varies in amplitude on some Volts/Div settings, but not others, incorrect Readout (incorrect numbers, missing symbols), signal changes when touching the Volts/Div knob. As the Plugin is quite dirty inside, I am in the process of removing the Readout/Attenuator pcb's and Cam switch as a Unit to clean the switches properly. I have removed everything except the BNC. I am unable to get a decent grip of the BNC nut without damaging other components ... C100 and the Attenuator shield mount are blocking sockets or tube spanners. What do you recommend as the best approach??? This is my first attempt at pulling apart one of these Plugins. Advice appreciated. -- Cheers, Ian, Melbourne, Australia

Just in case people are not viewing the FS/WTB Group, I still have 468/465/465B for sale (in the UK only) on that group and am open to offers. Check that Group site for full info. Regards Nigel

Has anyone managed to calibrate a 2465B without using the Tek specific test gear (PG506, TG501)? I have an HP8112A pulse generator and an HP33120 function generator, can they be used instead? - Keith

I've looked over the 2465B manual but I can't for the life of me find where it describes setting the word recognizer pattern. I can set the trigger to trigger on the word recognizer match and I can change the radix but I don't see where to actually set the pattern that is matched. If anyone knows ... please let me know!

Hi All. On my 2465A the scale factors are readable and seem to be accurate but they are nearly off the bottom of the screen. I have to look at an angle to read them. Is there an adjustment that is necessary to bring them back into view? Or do I just need to learn to stand on my tip toes! Everything else seems to fine with the scope... but this is pretty annoying. Thanks in advance for any advice. John w. N7ZMG

When we closed our Electronics shop at the University, I bought a pallet full of stuff. In that, there was a small parts cabinet with drawers of components. About half appear to be Tektronix, many in Tek bags, others that look like Tek part numbers. Anyway to tell what these belong to? Many parts I will never use but could be of value to people here keeping old Tek gear running. I can generate a list. Just curious if there is any cross reference of part numbers. I find the list of Parts categories, e.g. 151-0000-00 Transistors (1xxx=FETs) 152-0000-00 Diodes 153-0000-00 Selected diodes 153-0500-00 Selected transistors

Hi Gurus> I have a badly behaving analogue RGBHV video signal. Whilst VSync pulses repeat steadily every 49.99 Hz, HSync is all over the place Both H & V pulses are negative going from 5v to 1v). I have developed an HSync substitute, which mimics the 4.7us HSync pulses and starts on the tail end of each VSync pulse (210us). These are 271 lines to a frame, thus 271 HSync pulses per frame. Unfortunately because only the front end of the HSync train of 271 pulses is tethered to the VSync pulse the last video line is not necessarily complete before the HSync pulse starts. The attached display knows its got an incoming signal but cannot display it because the frame/line rate is not stable. I have several ideas on how to solve it, but to do so I need to see the last line of the frame, before the VSync pulse starts. I can use a 7854 or 7844 or 7904 and have the usual timebases to work with them. So either I need to trigger on the 270th HSync pulse or extend the display to show all 271 lines at a display rate of 500ps per sec and trigger on any HSync pulse. HSync counting is in binary. I realise I can extract the relevant HSync pulse, but to do so I will have to make up new PCBs, AND that will only get me the one pulse out. Anyone got any ideas ?

Hi all, This is my first message on this group. I have a strange problem with my recently bought Tek 2235, which was in apparent very good condition with a sharp, bright trace (which made me feel safe re. the CRT's condition), and it passed the performance check procedure of the service manual with flying colours. But when I started actually using it, I noticed that, after a variable running time ranging from a minute to several hours, the whole surface of the screen starts glowing rather uniformly, and the glow can become so intense that it gets almost as bright as the trace itself - at which point I turn the 'scope off in case it could get damaged. I had never seen that behaviour before, nor have I seen it described in the manuals or on the internet. I can add that the supply voltages are spot on, that the deflection and brightness control voltages appear to be correct as well - and, more importantly, they don't show glitches, remain constant in time, and remain the same with or without the glow. The 'scope did not have the 050-2242-03 power supply update advised by Tektronix so I made it, also changed the supply capacitors for good measure (needlessly, they were perfect), and added a fan as in the 2236, just in case the problem was temperature-related. That did not made the problem worse, but did not improve it either. I tried to locate possible cold solder joints and PCB contamination, but could not find anything. I noticed that the glow appears much sooner if the 'scope has only been left off for a short time before turning it on again, and much later if it has been allowed to rest for a day. That made me think that the cause might be a static charge building up while the CRT is powered, and needing time to dissipate when it is unpowered, but I haven't found any evidence of this. I have created an album with photos of the problem: /g/TekScopes/album?id=297784. Has anyone seen this sort of thing before? I really, really hope that there is a solution! Many thanks in advance for any idea you may have.

The following items have been added to the Files area of the [email protected] group. * /070-6860-00.Tektronix.2465B-Operators.Manual.pdf ( /g/TekScopes/files/070-6860-00.Tektronix.2465B-Operators.Manual.pdf ) *By:* vk2bea <vk2bea@...> *Description:* 070-68860-00 2465B / 2455B / 2445B Oscilloscope - Operators manual (high quality scan with navigation links)

Hi, I could not find any explanation about how to set this semi-fixed front panel control on the 7633. Manuals say: ? FAST LEVEL CENTER adjustment is provided to separately adjust the fast mesh voltage for the desired tracking of the STORAGE LEVEL, on the two meshes. ? FAST LEVEL CENTER-Adjusts the voltage level of the FAST target relative to the viewing target and, therefore, the tracking of the STORAGE LEVEL for the two targets. But it is not clear to me how must I adjust it, besides some empirical attempts. Does someone know more?

Although not 100% accurate schematics for the TDS400 series have been posted to the files section of this group as well as TekWiki. They were scanned from "C" and "D" size engineering drawings and then converted mostly to "A" legal size. These were late pre-production drawings and did not contain the power supply (not Tek made). I did not have access to final engineering drawings. No manual was ever published by Tektronix for the TDS400 series which contained schematics or parts layout drawings or pictures. Being the first all digital oscilloscope which relied extensively on microprocessor control, it was new territory. The next series, TDS500, had manuals which were similar to past Tek manuals complete with schematics, theory of operation, and pictures. I have no background in manual writing or compiling, just a technical background working at Tektronix for about 30 years. I was able to obtain the drawings from one of the engineers who designed the TDS series, now passed on. I tried to post on TekWiki but was not savvy enough to figure out the posting process. I had sent a couple of the trigger related schematics to Tim Wright who was having triggering issues with his TDS420 in hopes it would help him find his problem. I then posted all my jpg files to the cloud and informed Tim that they were available for him to use. Kurt Rosenfeld at TekWiki has also been informed of the existence of the schematics. Both Tim and Kurt have assembled my jpg images into a single pdf file. I thank them both for doing something that I had been unable to do which resulted in my work to be available to those who may need it. The TekWiki availability is here: https://w140.com/tekwiki/wiki/TDS420 - or: https://w140.com/tekwiki/wiki/TDS460 The schematics are available in the Group files section here: /g/TekScopes/files/Tektronix%20TDS420_460%20Schematics.pdf Best regards, Ferrous Steinka

Having does the necessary restoration on my T130L-C, I am now running through the calibrations. I have an issue with the 0-3 and 0-10pF calibrations. The controls, R100 and R99 respectively., have the 'range' but it's clear that the points at which they were set have become 'burnt in' for want of a better description. At those very points where it is almost correct the control loses its authority and idle goes full scale. A spot of cleaner I figured. But no... On inspection, they both seem, uniquely amongst the rest of the pots, to be wax-sealed or similar. I'm assuming in pursuit of stability, but sadly now working against that at 50+ years on! Anyone come across this issue, and therefore recommended resolution? Before I extricate then and attempt to clean.

I know this is a long shot, but doesn't hurt to ask. I want a P11 phosphor tube for my 570/575. I know the pitfalls of them vs regular green P1/P2/P31 phosphor for day to day use, but I still want one. Can trade a working P1 tube from my 575 if you wanted a green one in exchange (slight burn in, at the bottom lower left corner where the dot must have remained idle for some time). Located in Rochester, NY.