Apologies if this has been answered but I couldn't find in a search: I'm about to restore my first piece of Tek kit. understand the potential issue with the silver deposit ceramic strips and have electronic solder to hand that is 95% Tin, 3.8% Silver and 0.7% Copper. This appears to exceed comfortably the desired silver content, but it will be higher melting point (227 degC) than lead-containing variants. My question is "do I need to buy yet another reel of solder such as Sn62/Pb36/Ag2 which will be 179 degC melting point but lower silver or can I use what I already have?". Another way of asking: provided solder is silver-containing how much does temperature vs. silver content matter? Thnak you.

Hi, everybody. So at some point I will take the plunge into vacuum tube audio, and according to George Lydeck on this group, the Tek 535A is the best scope ever for tube audio work. Now, I figured out that the letter series and 1- series plug-ins, although not all of them, are the ones to plug into this mainframe. I have that stuff on my Test Equipment Wishlist already. OTOH, plugging directly into scope or plug-in inputs (assumed BNC, since I don't really want to go down the rabbit hole of UHF connectors) is probably not going to be productive, so I will need some probes. Type N, SMA, 3.5 mm, BNC, and TNC are quite enough variety in my garage lab, thank you very much. Try as I might, on TekWiki and the Internet at large, I cannot find anything specifically saying which Tek probes are appropriate for a vacuum tube scope such as the 535A. Maybe this is tribal knowledge? AFAIK, I have not used a scope with more than 1 tube, the CRT, (I was born in 1965, approaching 60 years old early in 2025), so the world was mostly solid-state by the time I was old enough to be playing around with scopes. Come to think of it, all 5 of my current scopes have CRTs, and I don't think I've owned one yet with an LCD screen. I'm in the 'tween generation, I guess. Any recommendations for probes for a 535A? Plug-ins also would be a good idea to know for the wishlist. Thanks a bunch! Jim FordLaguna Hills, California, USA

Channel 2 will trigger on Channel 1 and External, but it does not trigger on channel 2. This is what I am working on next!

Greetings from Louisiana! I have 3 465's and I am parting one out. If anyone needs a part let me know. I pulled all the transistors, they are in sockets. I had about 6 transistors that were bad. I was somewhat surprised to find so many bad transistors. Barry

Greetings from Louisiana! Working on a Tektronics SC503 that still has a few issues. I got the power supplies sorted out and I am able to finally see a trace on the CRT. Its bright and beautiful and it looks like the CRT is in great shape. But on to the next issue... The Channel 1 trace is located at the top 1/4 of the crt. The Channel 2 trace is fine! Its a vertical issue, Where should I start looking. The manual doesn't have a trouble shooting section for that... Regards, Barry

Hi John : What a good answer to my question, I hope you don’t mind my response to your personal mail. I did not mention that I have JFETs instead of a matching pair of 12au6s in both horizontal and vertical amps. The other 4 12au6s are still in use, with the heater voltages reduced with a 330 ohm power resistor. The balance problem occurs in both horizontal and vertical amps. Do you think it worthwhile to put the JFETs where the remaining 12au6s are and the valves in place of the JFETs to see if the balance improves? The valves are not matched I don’t think. Thanks again, Jack

Hi everyone, My 575 curve tracer’s DC balance on front panel won’t calibrate properly. I am following the calibration procedures in the manual. The dot won’t center, with the pot range switch at the end of its range. It is within 1 graticule though. Also, changing the vertical or horizontal sensitivity causes the dot to shift around a bit. I noticed the DC pots had been changed from the 10k value for my serial no. to 100k. I got the 10k figure from the parts list in the manual. I am assuming that parts list includes all serial no’s. My serial is a later one, and has the 122C modification. My serial is 012947. The scope makes nice looking curves and works well. Thanks for any help here. Jack

Got a Tek 454A the other day and did a quick test. It turns out that the only way to see a trace on the screen is to hold down the “Beam Finder” switch. As soon as it was released, the trace was gone. When I turned the "Intensity" knob all the way to the max, I can see some blurry shadow-like stuff on the screen. I shot a video to demo the problem: https://youtu.be/7HERqOtBGOo?si=wpvnHFCTCqLt0IzT So far, I have tried the following for troubleshooting: 1. Tried all vertical sensitivities and it didn’t make any changes. Also tried a x10 probe, still nothing. Switched trigger to GND, nothing. Adjusted the “position” knob and I could barely see some slight movement of the shadow - in beam finder mode, it moved the line up and down so the knob works fine. 2. Measured the PSU rails, including the -12V, +12V, and +75V and they were all good. 3. Measured the sawtooth waveform on pin L on the Sweep A board and the waveform looked fine and the Peak-to-Peak voltage was very close to 10V. 4. Cleaned the Beam Finder switch. I’m curious, why in beam finder mode, the waveform and the trace were clearly visible - it’s just that the screen was vertically compresses, which I suppose it normal. That said, everything disappeared as soon as I let go off the momentary switch. I did some research and it seems that the beam finder mode bypasses the intensity control circuitry so does it mean this circuitry is faulty? How can I verify that and troubleshoot? Any thoughts are appreciated!

I'm on my last 7K repair project, another 7904. This one has been a PITA with a failure inside the power supply. I had gotten it down to suspecting something in the HV supply, and set it aside a while ago. I decided to try a new diagnostic method I've been thinking about, but had to at least partly complete another project first. I finally got it far enough along to be usable. It's an experiment driver power amplifier that's ultimately for the lock-in analyzer department. I have two other amplifiers for this purpose, with special characteristics, but not enough power for my plans on the 7904. This third one gets into the 100W and up range, so can easily do what I want. All of these are basically audio power amplifiers modified for the purpose. The two smaller ones (10 and 30 Wrms) have galvanically isolated ins and outs to avoid low frequency ground loops, and built-in ballast resistors and clamping for protection against any type of load. I had to forgo the isolation on this big one, so it's a little trickier to use. I happened to have this nice medium power stereo amplifier made for driving lots of paralleled speaker load down to 2 ohms. It's specified for 60 Wrms per channel, but can do way more with higher distortion allowed. I modified it with output clamping and big ballast resistance (2, 5, 10, 20, or 50 ohms) selected by hooking up to the appropriate speaker terminals. It also has signal monitoring for the amplifier output voltage and current, and load voltage, on BNCs. The plan was to just drive it with a function generator, but since I had a crappy little junker ICL8038-based generator available, I removed and modified its board to build inside the amplifier, so it could stand alone too. This is only using one channel. I can picture adding both together with ballast if they can track well enough at high frequencies, but the total possible power can't be dissipated in the box anyway. I would have to repackage it all into a real test equipment chassis with enough volume and fan cooling just to use the one channel to full capability. So it's not quite ready for prime time, but yesterday I finally got it together enough to take a shot at the 7904 PS. I could have rigged this all up easily in simpler form at any point, but I resisted that to keep the impetus on getting this thing mostly built. Really it's just a sufficient audio power amp with some series ballast resistance to be hooked up to a secondary winding on the SMPS, while monitoring the voltages and currents to figure out what's going on. The amplifier has plenty of juice to reach over 80 Vpp at 25 kHz with quite a few watts of load, but only about 40 Vpp is needed for this, so in any testing like this, it's important to closely monitor and control the output level. Anyway, the 7904 PS was already opened up to expose the high voltage section. I first disconnected the primary winding of the main transformer for safety, and to avoid complications from it trying to start up during experiments. This prevents the big line to raw DC filter caps from charging up through the clamp diodes, which is hazardous. I hooked the amplifier up to the winding that makes the raw supplies for the +/-15V regulators, with 5 ohms of ballast, so it would drive either half of the winding with respect to ground (if it was isolated like my other amps, it could be end to end instead). I set up one of my modified (oil-filled and 500 meg input R) P6015s plugged into the Alden connector, and the scope set up to look at everything as needed. I used the internal 8038 generator set to 25 kHz, monitored with a counter. Then I turned on the amplifier output switch and adjusted the volume control for about 40 Vpp output. It took me less time to figure out what was wrong than it did to set up the test. The current was way too high, when it should have needed only enough to magnetize the core and charge up all the DC outputs of the whole supply. When it's unhooked and taken apart this far, there should be virtually no real power load after the caps are up. I already knew that the low voltage supp

I’m restoring a Tek 130 LC and will need to replace the above. On one side the plastic piece (210-047) has broken which won’t be hard to replace with similar or a 3D print, but on the other the captive stop (105-009) has been lost and all parts replaced with nasty bodges. My question is: before spending lots of time milling/printing custom parts, does anyone have either sources or recommendations? Thank you.

Hi all, After my TDS8000 eBay bargain turned out to be a nicely working unit, I’m now looking for the expensive part, a Tektronix 80E04 sampling head. I know those modules are for sale on sites like eBay, where they for 3K, 4K or even higher, if you filter out the broken ones.. But what do you guys consider a fair price for such a device? If anyone has one for sale; please please let me know !

I have DSA602A scopes at home and enjoy using them. The flexibility of various channel voltage and frequency options is very useful along with their waveform definition entry, averaging/persistence acquisition options And extensive measurement and statistics capability within the scope. Collectively the DSA602s and plugins form a very capable general use scope including both real time and effective time sampling, depending upon what is being measured. At work, I use mostly TEK 5 Series MSO scopes with advanced ISO-Vu and differential probes. Even with these advanced recent TEK 5 Series scopes, I find that usually I transfer acquisition data to lab laptop and use TEK analysis software, python, excel or Matlab to analyze deep memory fast sampling rate data records. So, one significant difference is the extreme deep memory available with TEK 5 Series for longer acquisition time at very high sampling rates, far beyond what is possible with the DSA602 scopes. Still, one could argue even today that given the difference in price per performance and feature set, the DSA602a scope still holds significant "value" as a general use scope if the size and weight is tolerable, park it on a cart and wheel the cart where needed. At work, I also keep the TEK 5 Series on cart and do the same thing, so not terribly different. The DSA602a offers inexpensive 1GHz channel bandwidth with 11A71 and 11A72 plugins, at work budgets dictated mostly 200MHz bandwidth TEK 5 Series scopes, a practical difference in price vs performance. With modern TEK 5 Series, most measurements require using external differential probes for each channel and high performance differential probes are quite expensive and add significant total system cost. At home, I use 11A33 plugins and have 150MHz bandwidth with dual high impedance (up to 1Gohm) inputs to nearly achieve the same thing for pennies on the dollar for many types of signal monitoring. Beyond that, for DSA602a general purpose use the 11A32, 11A34 and 11A52 plugins provide more options geared toward specific testing needs and the three plugins slots can support plugins of mixed type. The DSA602 is still useful today for most general purpose use. Advanced applications (ie double pulse testing on cutting edge GaN or SiC FET designs) probably warrants a modern scope, though even the DSA602 supports integration and energy calculations so with enough effort it might be possible to get results.

Greetings for Louisiana! I have an SC503 that has an issue with the -12V Power Supply. When I started troubleshooting the PS I came across a bad transistor, Q8052, plus several tantalums. At that time the voltage was about -3 volts. After I changed the transistor the voltage jumped to -33.4 volts. I course this helped identify 2 other weak tantalums. I have put sockets for all the transistors in the -12V Supply having checked each transistor using my Atlas DCA Pro. I believe I have also checked all of the diodes and all of the resistors. The voltages of Q6041 is as follows E=0.703, B=-1.273, C=0.01. the schematic shows that E=+0.62 B=0.0 and Collector=-10.3Volts. Is there anyone in the group that can offer suggestions? Thanks! Barry

Hi, I am playing around with the DSA 602A and I am rather confused by histograms. I could create them, but I cannot imagine a way to make them useful (the manual does not say what they are for). Surely this is a limit of my limited knowledge... would someone help me ? Thanks Gianni

HI all, I have an older 7904 (SN < B260000) that I've been happily using, but decided to check Z-axis calibration. Step 4k is where I've hit a wall, so basically right out of the gate. Voltage on TP 1778 to chassis ground is supposed to be 123 ± 3 VDC, and it's 128 V. Unfortunately, R1757 does not change the reading at all. DC voltages on the supply are good, and I have +50 on R1757 as expected (and voltage on the other other side of it varies smoothly). I checked transistors and diodes in the focus amplifier (Q1765, Q1769, Q1757, Q1755, CR1768, CR1764, CR1754) with a DMM diode check, and none of them are shorted. R1762 (75K) measures 12K in-circuit, but I'm skeptical that means anything. Anyone else seen this, or have ideas on what to look for? thanks, Adam

Hello all, Have a 7904A, low SN, 1982, stored for decades. Usual cleaning of switches, contrlols, the CRT, bright and in focus. But all surfaces, PCB, PS, HV, CRT are coated with dust. Suggest I vacuum with brush nozzle, finish with compressed air? Which is better? Am Wary of Air, Vacuum ESD, damage, So, should use Metal nozzles , earthed? Many thanks, Have an absolutely fantastic day Jon

Hi, I recently picked up the hobby of ( trying to ) repairing old test equipment and got a TDS540. I have been trying to get it to boot up but it is stuck with a flashrom checksum error. It seems somehow the firmware got compromised. All caps have been replaced and the boards ( A10, A11, display ) look good with no apparent visual damage. NVRAM has been replaced with a preprogrammed version from kellyjo_13 / ebay. After reading to multiple posts on different forums I guess I am more confused than before... My questions are : Where can I download a working firmware version for my TDS540 ? How to update the FW ( in Windows ? , DOS ? ) Which ( if any ) GPIB to USB converter would work or do I need an old 488.2 card ? The boot message looks as follows : Enabling Bus Control register. Value = 0x67 IMR 1 Register test passed. Misc. Register test passed. Timer Interrupt test (Auto-Vector) passed. NVRam DSACK test passed. NVRam Write protected. Flashrom DSACK and JumpCode test passed. Invalid Flashrom Header checksum = 0x3efc, should be 0xfefb Flashrom Checksum test failed. Cannot transfer control to Flashrom. Transferring control to the SDM (monitor). Any help is very much appreciated. Hans

Hello, I have a TDS754D. Works fine but I’m having trouble getting some simple screenshots out. I used the hardcopy function, export as .bmp mono color and export to floppy. For some reasons it will sometimes work, sometimes the image is corrupted or just unreadable. See here: https://imgur.com/a/hy1iFwE Any idea why this is happening? I’m reading the files using a USB floppy drive and a Windows 10 laptop if that helps.

Can anyone identify these parts I find in my 575 curve tracer. Is this a mod that tek made? The dc balance doesn’t adjust properly, and the dc adjust pots appear to have been replaced with much higher resistances. This is in vertical and horizontal amplifiers. Can I check the heater voltages of the remaining 12au6s in the string by identifying the cathode pins and measuring the voltage across them? Please help me with these questions Sincerely, Jack

Hi! Can someone please copy file C:\TekScope\calibration\calSPCConst.dat from DPO7254-DPO7354? And send it to me by email. (And console.txt, diag.txt from C:\TekScope\calibration\ )