Hi I have changed the battery on the GPIB board and thought, stupidly, I would change the battery on the storage board. Now I realise I have lost some settings and need software to reconfigure. Does anybody have access to the 'Flatness test' software for the 271x Series spectrum analysers. Hiding my face with embarrassment and hoping some one can help. Thanks Andy

I've been sorting and organizing my 7K plug-in collection recently, and found my one and only 7A29 acquired long ago, but never used. I thought I'd check it out and look it up, and saw various reports about problems with the attenuator needing lubrication and broken cams due to stress from lack thereof. Sure enough, I saw a piece of cam plastic trapped under the aluminum cover over the shaft section. The worst part is that I may have just broken it myself - I turned it back and forth a couple times and noticed it was very tight, before finding sufficient info about this problem. Maybe it was already broken, or maybe not. I managed to loosen things up enough to get that cover off with the attenuator still in place, and I recovered the cam piece. It looks like just that one piece came off from the front-most cam, so I think it can be glued back together with no missing pieces. The others are intact but show numerous and serious cracks, so will need work too. I'll have to pull the attenuator out and do a rebuild. My plan is to reinforce all the molded cam shanks with wire bands, then fill the cracks and bond everything with epoxy. That part should be OK, but tedious. The real issue and questions are about the lubrication. The online stuff I've seen so far does not really address details, mostly talking about lubing the cam-follower rollers that work the plastic plungers that move the attenuator contacts inside. I'm convinced that the real problem is not so much in the rollers, but the big plastic sections they ride on. These are C-frame type structures likely a glass-filled plastic for rigidity, with square posts passing through the attenuator to tie the opposite sides together. These then work the tiny plastic plungers that operate the opposing contacts. There's significant friction from those square post sections, so I think they should be lubed too. Pressing on the front one (which happens to be loose now, while the other two are compressed - I didn't want to turn the shaft any more and risk further breakage), I can feel the drag and abrasiveness of the post against the passageway through the attenuator housing. Some lube there should help a lot, but the trick is to not contaminate any of the contacts. Anyway, I'll be rebuilding this thing at some point, and plan to lube it all up just the right amount. I'm wondering if there's any kind of official maintenance info or documents from Tek about this, and what others know about or have done on this item. The discussions I've seen so far were on eevblog and right here too, I think, but from quite a while ago, circa 2008. Is there anything newer? Ed

The following photos have been uploaded to the 7A29 attenuator repair ( https://groups.io/g/TekScopes/album?id=297937 ) photo album of the TekScopes@groups.io group. * cam follower slide.JPG ( https://groups.io/g/TekScopes/photofromactivity?id=3835765 ) *By:* ed breya <eb@...> --- The following photos have been uploaded to the 7A29 attenuator repair ( https://groups.io/g/TekScopes/album?id=297937 ) photo album of the TekScopes@groups.io group. * detent wheel cracked.JPG ( https://groups.io/g/TekScopes/photofromactivity?id=3835766 ) *By:* ed breya <eb@...> --- The following photos have been uploaded to the 7A29 attenuator repair ( https://groups.io/g/TekScopes/album?id=297937 ) photo album of the TekScopes@groups.io group. * back bushing cracked.JPG ( https://groups.io/g/TekScopes/photofromactivity?id=3835768 ) *By:* ed breya <eb@...>

The following photos have been uploaded to the 7A29 attenuator repair ( https://groups.io/g/TekScopes/album?id=297937 ) photo album of the TekScopes@groups.io group. * top view.JPG ( https://groups.io/g/TekScopes/photofromactivity?id=3835763 ) *By:* ed breya <eb@...>

The following photos have been uploaded to the 7A29 attenuator repair ( https://groups.io/g/TekScopes/album?id=297937 ) photo album of the TekScopes@groups.io group. * side view.JPG ( https://groups.io/g/TekScopes/photofromactivity?id=3835759 ) *By:* ed breya <eb@...>

Our local Physics Dept. is closing down their 50+ year accumulation of spares. Everything is up for grabs. I have gone thru and grabbed what I thought might be of value and that includes two Tek power transformers. These are used, but the man who ran this shop for decades didn't save junk. I don't know what these are for, but if you recognize the part numbers let me know what they fit. Here's what I have: Marked 120100, which I assume means 120.100. Has 19 terminals on a beige phenolic board that has 30 numbered holes. There were four 8-32 long thru bolts that held everything together and probably also mounted the transformer to the chassis. Two of those bolts are missing, but I doubt if that's a problem, since your old transformer would have replacements, or some threaded rod could be used with an extra nut. According to the RPR on TekWiki, this fits a Tek 551. Marked 120.0203.00. Has 11 terminals, with numbers marked on a silver Tek label. It's complete with four 10-32 thru bolts and nuts. There's a "7939" ink-stamped on the core, which might be a 1979 date code. According to the RPR on TekWiki, this fits the Tek 503 & 504, including the rack mount versions. Let me know if you can use one or both of these, or just if you have a better idea of what these came out of. Price is free, but I'll ask for the cost of shipping and a bit for my time to pack and take to the Post Office. Local pickup in Madison, WI would be free and welcome. thanks for reading, -- Jim Adney Madison, WI USA

To get to the chase, my TEK S-4 Sampling Head kills the power supply on my (multiple P^) TEK 7854 mainframes. I seek advice as to where to look next. First, possibly irrelevant, information. I have a TEK 7S12 TDR/Sampler that arrived poorly packaged (crumpled newspaper in a toilet paper box from an eBay seller whom I gave a negative review for his packaging "skill," and sending my a barely-functional mainframe not billed as "parts or repair") installed in a TEK 7854 'scope (my favourite, after my MIT-purchased 465--the 7854 was the first 'scope I used extensively after graduation, and programmed with my HP41C calculator on my first job after college.) Inserted into that 7S12 was a(n) S-4 Sampling Head, along with a(n) S-53 Trigger Recognizer. When I first fired up the kit back then, I found that the 7854 was AFU--garbled readout, odd timing, no stored WFM display, fairly useless, save for parts used to repair the other two, fully-functional, 7854s. Subsequently, plugging the 7S12 into a fuctional, and calibrated 7854, revealed a trace. That was about 20 years ago when it first arrived. Last week I wanted to do a TDR measurement of a ~1GHz test fixture. The 7S12 with S-4 fired up just fine, for about 30 seconds, in a good 7854 mainframe. Then the 7854 power went kablooey: lights out, no trace, no readout, power light on, but clearly no longer at one with the Universe. Further testing, inserting my S-1 Sampling head, resulted in a functional assembly: 7854, 7S12, S-1. Upon a cursory look inside the S-4, I unsoldered one end of C55 the 22uF Tantalum electrolytic cap bypassing +15V via L55 ("14T"), only to find it measured 22uF with about .6ohm ESR. Just unsoldering that cap still kills the 7854 power supply, e.g, 7854 and 7S12 play well together, with out a sampling head. Clearly other component(s) in the S-4 cause the problem. I'll have another look, a good suspect is C45, 3.3uF, also bypassing +15V directly to chassis GND. Has anyone experience with this sampler (or, in general, dying 7854 mainframe power, dependent on plug-in) to suggest which component(s) might be suspect, dying shortly after power-up after all these years? Is there an easy way to measure, directly, the mainframe's power supply busses? I have extenders, fixed and flexible. I'm just starting this troubleshooting exercise. Forgive me for being lazy, seeking advice before I get too far into this project and possibly messing up something that is not currently broken. This is my first query to the group after many years of pleasant, albeit gnurdly, leisure reading. Please forgive any unintentional laps of protocol. I have done a search for S-4 and 7S12, but found nothing useful. Not to say there's nothing useful out there; I just did not find it. Arne Buck

I am having a problem with my Tek 453 scope, SN 001688, Mod 210H made for IBM. The display is very wide vertically and very bright - I have no control of the intensity. The Focus control does work. I used a Fluke 75 DVM for voltage measurements and a Owon VSD2200I PC oscilloscope with a laptop computer for waveform measurements. All the power supply voltages are within tolerance using a Fluke 75 DVM. Unfortunately I do not have a meter capable of reading the negative 1950 cathode voltage. On the Z Axis Amplifier I am able to vary the voltage at TP 1047 from 2.6 volts to 80 volts using Intensity control R1005, however it does not affect the very bright sweep intensity. The negative going gate signal looks normal. On page 38 of the Tektronix manual “Troubleshooting Your Oscilloscope”, paragraph 1 states: Inability to turn off the intensity is often caused by a weak D.C. Restorer diode in the control-grid supply. I assume they are referring to diode D940 in the CRT circuit. I disconnected one lead of one of the 2 diodes in series (PN 152-0408-00) and using a 9 volt battery and my DVM in series with the diodes I measured the forward and reverse voltage. For D940-1 I measured 5.552 volts in the forward direction and 0.039 volts in the reverse direction. For D940-2 I measured 6.230 volts in the forward direction and 0.105 volts in the reverse direction. Are these voltages normal? Speaking of the CRT circuit, where are the vacuum tubes and the majority of the resistors located? Are they behind the CRT circuit chassis and if so must I disconnect anything to access them? Even though the troubleshooting manual states internal CRT grid shorts may not show up with ohmmeter resistance checks, I went ahead and unplugged the socket from the CRT and checked for continuity between pins. Everything checked open. I would very much appreciate any help identifying and solving the source of this problem. Thank you in advance.

I was working on repairing a 670-1376 low voltage regulator that I removed from a 7603. The 130 volt supply had blown transistors and resistors. I replaced the bad parts and I thought all was OK. When I looked at the ripple, I had almost 1 volt of ripple that had a frequency of 4.6 mHz. ALL the voltages had the same ripple. Since I had a spare interface pcb that I had removed from another 7603, I used that to make the connections for feedback since it was easier than trying to troubleshoot the regulator installed in a scope chassis. I kept testing capacitors thinking that that was likely the problem. Then, I replaced the TO-3 pass transistor for the 130 volt since that was a new part. No joy. Still had the 4.6 mHz ripple...even on the ground plane. Took me a while to think the interface board could be the problem. It was a leaky cap on that interface board. What did I learn....the easy way is not always the best way. I can claim old age!

I have a 2467B (s/n > 050000) here that exhibits some small bumps in the CH1 and CH2 traces even with those channels set to GND. They are very tiny bumps that do not change in amplitude even with the VOLTS/DIV on either channel increased or decreased until I get down to 2mv where I notice a very minimal increase in their height. These do not appear on the CH3 and CH4 inputs. They do change in width as the SEC/DIV rate is changed but almost disappear at 200ns and slower. At 100ns, they are fairly close to the beginning of the trace, on the far left. At 20ns, they are approximately in the center of the trace. They are identical in appearance, both amplitude and location on both CH1 and CH2. I'm intrigued that it only affects CH1 and CH2 and affects them identically, so feel like what is common to those two channels but not common to CH3 and CH4 is a clue. Is this a classic sign of caps whose time has come or is there something a little more sinister at work here? Looking for and appreciating the collective wisdom of the group. Chris -- Chris Elmquist NØJCF

Hi folks, My TG501 has lost it's 2ns/1ns output. It's looking like it could be CR500 has gone belly up? I'm getting no harmonic output at L502/C504/C505, just 100MHz out of the 10ns amp (Q484/Q486). Parts says it's 152-0503-00, and my preliminary lookup isn't turning up listings or substitutes. Anyone know where I can source one or equivalent? Thanks, Dave

Also, Beam Find doesn’t work. Because the CRT doesn’t work, I cannot see a precise Fail Code. This is my own 2465B, with the A5 SMD version. Ch1 input was connected to my Agilent 33220A Generator Output and Agilent Frequency Counter, and suddenly the screen went blank. I’m not clear whether the damage is related to the 2 Agilent machines (which are still working fine). Weird if it is, because this equipment has been interconnected for years with no problems. About 10 years ago, I did a full overhaul of the A5, taking care of all the known Electrolyte issues, and replacing caps as per my kit. No leakage was found, and the scope has been fine since. Now, I’ve replaced all the SMD Resistors and Capacitors around the DAC U2101, with no improvement. The only issue I found is that the +1.36V rail (CR2420 Cathode) is 0.31V. I have removed and tested each and every component on that rail to check whether one was pulling down the voltage, but no improvement. I’m wondering if it is supposed to be +1.36V ONLY AFTER the machine boots correctly, and if it doesn’t boot, then that voltage is up in the air. The Manual states to look at the A Trigger “Generator”, and the “Line Trigger Source”. Forgive me, but this terminology has me beat – where in the manual are these areas being referred to? Does anyone have any other ideas? Thanks Menahem

Chris Elmquist <chrise@...> added the photo album 2467B "speed bump" noise ( https://groups.io/g/TekScopes/album?id=297874 ) : demonstrating noise on 2467B CH1 and CH2 when those inputs are set to GND. Also showing no noise on CH3 and CH4 at the same time. --- The following photos have been uploaded to the 2467B "speed bump" noise ( https://groups.io/g/TekScopes/album?id=297874 ) photo album of the TekScopes@groups.io group. * IMG_2620.jpg ( https://groups.io/g/TekScopes/photofromactivity?id=3834655 ) * IMG_2619.jpg ( https://groups.io/g/TekScopes/photofromactivity?id=3834656 ) * IMG_2618.jpg ( https://groups.io/g/TekScopes/photofromactivity?id=3834657 ) * IMG_2617.jpg ( https://groups.io/g/TekScopes/photofromactivity?id=3834658 ) * IMG_2616.jpg ( https://groups.io/g/TekScopes/photofromactivity?id=3834659 ) * IMG_2615.jpg ( https://groups.io/g/TekScopes/photofromactivity?id=3834660 ) *By:* Chris Elmquist <chrise@...>

I have a 7B92 that I've been trying to repair (finally found a broken solder joint to Q922, located under the board, thus fixing the delayed trigger). I also think U660 is intermittent, so have a replacement on the way. However, the trace starts about 1.5 divisions to the right of the leftmost graticule if the Position pot is centered, and I have to crank it to the 10 o'clock position to get the trace to start at the left edge. Timebase knob is pushed in. Is this normal for a 7B92? - R523 is set correctly, per the manual - The mainframe horizontal amplifier is centered - A 7B85 doesn't exhibit this problem, so I think it's the 7B92 I just discovered that the trace starts to the left of graticule in 2ns and faster sweep. Looking at the timing switch schematic, S240B/39 connects the Position pot to emitter of Q424 in the 2ns/div position, but I'm not sure what it's doing; something with the delayed time/division. thanks, Adam

Is the new memory board (RAM & ROM) compatible with the old 7854 version? Thanks Regards Miguel

I am new to the forum and my trusted Tek 2465A just failed me. On startup it gives an error code that says Test 05 Fail 24. I can clear the code but then the scope fails to trigger and when I change voltage scales on any and all of the channels the horizontal line will jump way off screen. I can bring it back to the center by adjusting the vertical but if I change scales it is off the screen again or nearly so. Any hope for my scope? Where should I begin? Thanks in advance for reading... and helping me figure it out I hope. John w. N7ZMG

With the bandwidth issue on the 7633 resolved, I'm ready to look into the other issue with the scope: readout issue. When I turn up the readout intensity, I see '<down arrow>0' in all six readout positions (three along the top and three along the bottom). Pressing the IDENTIFY button for any of the channels moves the trace up 1/2 division (if present), but does not change the readout at all. Changing the timebase to any position also does not have any effect. What I have done so far includes: 1. A complete calibration not including the last two sections (readout and storage). This includes checking the power supply DC and ripple voltages which are all good. 2. Re-seated ICs and connectors on the readout board. Given what I'm seeing, I suspect a problem with the control (logic) circuitry which is concerning because there are a lot of custom Tek ICs in there. Absent any specific suggestions here, I'll start by verifying voltages and waveforms on the board against the schematic for anything unexpected. I have a working 7623A which appears to have an identical readout board in it, so I can swap out socketed parts fairly easily if needed. - Bill

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: https://groups.io/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.

Looking for recommendations for a ESR tester, what would this group advise? Mark

I picked up a nice looking 7L5 with L3 input module and opt 25 (tracking generator) recently. It is cosmetically almost like new, and clean, but I can't get a signal display so far. It all seems operational, with all the usual stuff controlled and displayed, including a base line, but no noise floor or evidence of input signals. I suspect a loss of the desired output signal to the display somewhere in the chain. I don't think it's toward the front end since there's virtually no noise floor evident. The baseline clipper has no effect either. I'm just starting to poke around in it today, and wondering if there are any experiences with such a problem and advice where to look first. This is a big, complicated unit, with difficult access to the guts, so I'm hoping to not need a lot of taking apart, at least for the diagnosis. I'm starting with visual inspection of the little I can see, then will do checks of any available signals, especially the TG output. If that's present and right, then that should confirm full and proper operation of the whole works, then only that display signal needs to be found. I have another 7L5 from about five years ago, that was and still is a basket case - mechanical damage and such, that I couldn't readily fix, and set aside. It could be a spare parts carcass if necessary. I've tried swapping its L3 into this one with no effect. Anyway, has anyone seen this kind of trouble before? Ed