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Hi all. Apart from the CEN-U45 is there a readily available replacement? Some people are using TIP 102's with the legs crossed over... Any other suggestions? Thanks in advance. James

Hi all, I've been trying to troubleshoot an amplitude problem on my new 492, which has had multiple other little problems along the way. At this point, I can get a stable display and frequency is OK, but amplitude is 20-30 dBm lower than it should be. Attenuator and first mixer seem good, but I'm missing the 110 MHz output from the 2nd converter (should be -37 dBm or -39 dBm depending on band), measuring with HP 8484A. The front panel 2nd LO output is ~17.6 dBm on the first band, and I measure +9 dBM and -1.5 dBm directly on the 2nd LO cavity oscillator, which all seems in the ballpark (and at least verifies the oscillator is not dead). Could the problem be something as simple as the oscillator being off frequency? My microwave counter has a power supply problem that I'm also trying to fix, and I doubt a 7S11/7T11 combo is precise enough to adjust it. I'm mildly tempted to just try turning the adjustment screw on the cavity oscillator and see if the display responds. Any other ideas? I'm not enthusiastic about opening up the 2072 MHz 2nd converter, but that looks like the only thing in the signal path that would lose the 110 MHz IF on all bands. thanks, Adam

The following photos have been uploaded to the 492 Bias Return ( /g/TekScopes/album?id=301504 ) photo album of the [email protected] group. * IMG_2343.JPG ( /g/TekScopes/photofromactivity?id=3900053 ) * IMG_2344.JPG ( /g/TekScopes/photofromactivity?id=3900054 ) * IMG_2345.JPG ( /g/TekScopes/photofromactivity?id=3900055 ) * IMG_2346.JPG ( /g/TekScopes/photofromactivity?id=3900056 ) * IMG_2347.JPG ( /g/TekScopes/photofromactivity?id=3900057 ) *By:* Adam R. Maxwell <amaxwell@...>

Still chasing a working copy or original of the Diagnostics Tape for the 4041. DaveB, NZ

Recently my Tek 2236 began giving a "Control Button Error" message, occasionally at first and now more regularly. Exercising the buttons does not seem to clear this. I ran the CTM diagnostic and everything passes except reading the 1X/10X CH1 sense ring, always indicating "P0" even when the ring is grounded (I don't know if it ever did sense correctly, as I generally used non-encoding probes anyway). In the diagnostic, it reliably reads the positions of all other switches, in particular indicating the push button positions solidly, no glitches seen in the 1/0 transitions in the diagnostic display. Sometimes with no input I get the "OUCH" message on CH1 volts (even with the input set to ground). Otherwise, all of the CRT display functions appear unaffected. When the CTM is working, everything works in the alphanumeric display, when not, I get the scrolling "Control Button Error" message, nothing works in any button configuration. Anyone have any thoughts on this? I have several Tek scopes, analog, full digital, storage (for a 5L4N) and a 4 channel. However the 2236 is my favorite for general bench work. I miss the built-in frequency counter...

I recently acquired a PG502 from Tek surplus (aka Country Store) and found several setting to be intermittent. Expecting that a good cleaning would be in order, I was astonished to find that cam switch drum appears to be decomposing. It looks dull, powdery and parched like mud flats after a dessert gully washer! In fact, there was a lot of fine debris on the contact board. Cleaning the board and the contacts made no difference because the cam lobes are deteriorating. I have not touched the cam drum with any cleaner or other chemicals. This unit was used in the production test area; perhaps its entire life. It was last cal’d June 2022. Perhaps it is the result of 45 years of continuous up time in a rack. I have never seen a cam drum look like this. Has anyone seen such a thing? (See photo gallery for “Decomposing Cam Switch Drum.”)

Hello everyone, My name is Jack, and I have a 575 that I am trying to understand better, and to calibrate and fix a couple of small things. The present issue is that I can’t get the single family switch on the step generator to do anything. The repetitive position works as it should, but switching to single family makes all curves displayed on repetitive, disappear. I have the instruction manual for the instrument, and the schematics for all the different blocks. I have cleaned the switch contacts, but am at a loss. Any suggestions for me would be greatly appreciated. I have very limited diagnostic capabilities. Very sincerely, Jack

I recently acquired a 7934, and was stepping thru the service manual I downloaded from Tekwiki. Its missing pages 6-22 and 6-23 and every copy I could find was also missing the same pages. Anyone have a copy that would be willing to provide the missing pages? Or better an original manual for sale? Mark W7HPW

Hello everybody, I managed to upgrade my TDS620 to a TDS640 by changing resistors on the acquisition-board. I now have 4 channels active and this is working fine and the scope reports that it is a TDS640. The only thing which is bothering me is a message added in the error-log every time when I start the scope. Error: 242 wrong hardware configuration Acq number of digitizer probe, expect: 2, actual 4 This is not limiting the functionality but is just annoying. Does somebody have some advise how to get rid of this message? Regards, Wamor

Hi all, As I'm exploring GPIB in my environment on multiple instruments, a newbee question - is GPIB essentially hot swappable? Differently put, can I typically just hook it up to an instrument that's running and expect it to smoothly connect? Or is it typically better to connect GPIB while the instrument is off, then turn it on, so it'd scan its "peripherals" during the booting sequence and this would guarantee it's connecting with no issues? I assume there's a rule of thumb, instead of a situation where maybe all instruments may be different and it's hard to tell what's the best approach. I've connected it plenty before, but 95% of the time it's been hooked up to one instrument and so "hot swapping" wasn't a consideration. This is for a TDS754D, reason I'm posting on this board, but I'm looking for some input applicable to any instrument/brand. Thank you, Radu.

/g/TekScopes/album?id=301414

I'm trying to repair a very stubborn TDS-520 fails on testing the proc and acquisition boards. Major capacitor leakage inside the unit. After a thorough clean and recap the unit this fails on both boards. Further research showed a track under a resistor that was broken. I repaired the broken track but it still isn't working correctly. I found out there's a debug port: J40 (board edge connector). Information in the internet about this debug port is fragmented and far from complete. I'm trying to get this sorted out to a complete solution. One post on the Tek-forum speaks about connecting an Option 13 (serial/parallel comm board) to this debug port. Separate option 13 boards are hard to find and otherwise quite expensive. It basically is nothing more than a pcb with a MC68681 Dual UART, some logic and 2 d-sub connectors. Is there any schematic around of the Option 13 board? Or any other circuit that interfaces between the scope and the serial port of a pc? Thanks.

Radu Bogdan Dicher <vondicher@...> added the photo album Tektronix TDS754D - acquisition board issues ( /g/TekScopes/album?id=301426 )

Hi all, I recently acquired a TDS794D and am having an issue with Channel 2 and a slight issue on Channel 1. It was originally failing the boot self-test with a "ERROR: diagnostic test failure, dsyRastModeV0Walk, raster fail @ 1,1 read: 8, expect: f" error which I assume is probably a video RAM or other video error, but I had a spare Processor board from a TDS754D with other faults that I swapped in and flashed the TDS794D firmware on, all working ok now. Next is Channel 2 and Channel 1. I am getting spurious signals on these channels, Channel 2 in all settings, and Channel 1 in only one setting. Linked image is Channel 2 with no signal input. If I connect a signal, the signal is shown with these spikes overlaid. https://i.imgur.com/a2qOjXJ.png I'm hoping this is a RAM issue as I have a bunch of RAM chips I have pulled from scrap acquisition boards. Has anyone seen this fault before and knows the likely fix? Thanks! Jared

Hello all, after quite a few years of absence from this group and from my trusty 7000-series equipment, I am back. The reason is quite obvious. I have a special measurement job which needs my 7A13. As expected, after almost 10 years of sitting around my 7A13 has quite a few issues, but this is a story on its own. As the subject already tells all the relays within the 7A13 have gone bad. Some seemed to work fine, but on closer inspection every relay has its own problems. Mostly contact resistance of the relays is highly unstable. Sometime you can get the relay down to 100mOhm, sometimes the same contact has up to 10 Ohm. Of course, I tried all the recommended reviving techniques like repeated switching at high frequency under load, etc. but nothing really helped. I remember that I replaced 2 of the relays already 10 years ago by a self-made free-floating solution to fit a new relay into the old socket. This was quite tedious and I don't want to repeat the same thing again. Leave alone the fact that this free-floating solution might not be capable of providing the right HF and Isolation performance. By searching for a better solution in this group I saw the solution of Tom Ford back in 2019. (/g/TekScopes/album?id=91736) Unfortunately, he didn't provide any design data and he seems to be offline since then. Therefore, I went to action and designed my own little adapter PCB. And I will also try to document my work as good as possible, to give anyone else enough information to do this on his own. Related pictures can be found here and maybe on my GibHub. /g/TekScopes/album?id=299851 My first Idea was to replace the internals of the original TEK relays with a modern relay with the original TEK Housing still in place. Therefore, the PCB had to be so small to fit inside the original housing and connect to the relay and the header pins. In addition to the relay there also should be a small bridge rectifier to get rid of the polarity issue most modern relays have (most modern relays are polarized) and optional a little SMD LED to see if the relay is activated. As the space within the relay is really tiny, I came up with the idea of using a 2layer Flex PCB which would be bent and hold the relay, a bridge rectifier and an LED + resistor. This concept (concept 1) looked really good but I had quite a few problems: 1. Crosstalk between channels and isolation between open contacts was not that good because of relatively long tracks in the flat flex running in parallel. 2. Flux residue between the flat flex and the header caused leakage which cause "enormous" leakage currents. Not the required +/-0.2nA more the +/-15nA or even more. 3. Due to the tight space within the relay the bending radius of the flat flex was quite tight and only in the range of 1-1.5mm. This caused on some trials problems with broken tracks. All in all, the ideas sounded great but the realization was not the great at all. For my next concept (concept2) I reverted back to the idea of Tom Ford and created my own little adapter PCB for both needed relay types used in the 7A13. At the moment this is an unproven design as the relays are still on back order and I'm waiting for the distributor to dispatch my order. For the relay I did a longer market study to find the best fitting relay. In the end I decided to use the AXICOM IM06TS which is really tiny and still provides relatively good switching and HF performance. The footprint of the relay is a little issue as the row spacing between the pins is only 5.08mm. This makes the pads slightly interfere with the through hole pads of the socket header. To still accommodate the socket header and the relay on the same PCB without interfering I decided that the pins of the relay need to be bent outwards a little (~.7mm per side). This is not a really nice solution but I assume it will work fine. If the socket header would have been available in a SMT version the use of a SMT relay would have made everything a lot easier. I presume Tom Ford used the BAS3007 as bridge rectifier. Unfortunately, th

Hello all, I have upgraded my TDS620 scope to display 4 (=>TDS640) by reconfiguring the acquisition board resistors. The scope is reporting to be a TDS640 and the channels are visible and working. Only in the log-file the scope is reporting that the number of channels is incorrect every time at startup. I’ve learned on this forum that the firmware for the TDS640 differs from the TDS620 firmware but that version-numbers is the same. Could someone maybe supply me with the TDS640 firmware? Regards, Wamor

Dang. I forgot to write that I also added the missing page 3-1 to the May 1986 revision. DaveD KC0WJN -- This email has been checked for viruses by Avast antivirus software. www.avast.com

I bought a no error codes on startup S/N B057443. Inspection of A5 showed no leaking of the SMD eCaps, but the Dallas DS1225Y was 1991 vintage by date code. I bought a new Dallas DS1225AB-200+ from Mouser. Desoldered the old SRAM with a Hakko 472D uneventfully, placed a TE Connectivity 1-2199299-2 28P DIP SKT 600 CL LADDER socket and soldered it in place without drama. Good looking solder joints. I was able to read the 1991 DS1225Y with the GQ-4x4 programmer and saved the data to a .bin file. I wrote and verified the .bin file to the 2023 “new” DS1225AB-200+ SRAM. Placed it carefully and correctly into the sock, and now have the 04 Fail error. Same thing with the old 1991 SRAM. I read the old and new SRAM data sets after trying startup, both sets of data were significantly changed. Bad solder joints? I ohm-checked the SRAM socket pins to the A5 board connections, listed below. The lowest resistance I found was a few .02Ω, most common was about .2Ω and the highest was .53Ω. Seems higher than I’d like in general. Normal? Tek 2465B Late A5 U2460 Pin Connections U2460 Pin Descriptor Component Pin 1 U2250 15 2 BA12 U2160 3 3 BA7 " 4 4 BA6 " 5 5 BA5 " 6 6 BA4 " 7 7 BA3 " 8 8 BA2 " 9 9 BA1 " 10 10 BA0 " 11 11 BD0 J4241 29 12 BD1 " 27 13 BD2 " 25 14 - " - 15 BD3 " 23 16 BD4 " 28 17 BD5 " 24 18 BD6 " 22 19 BD7 " 20 20 U2250 11 21 BA10 U2160 24 22 " 25 23 BA11 " 27 24 BA9 " 28 25 BA8 " 29 26 U2250 19 27 J512 23 I’m at a loss what to do going forward. Any help would be appreciated. Thanks, Ron AF5IV

Hello, my names Andy AKA Diabolical Artificer. I build valve amps & interested in vintage tech as well as using a 545B daily as my main scope. I also have a 585A & currently trying to get a 547 working. I'm on a few forums as well as having a small Youtube channel where I post my doings. I've been working on a 547 ser # 100091 for the last few weeks. after testing/re-forming all the big PSU caps I powered it up. After sorting some silly mistakes I'd made I checked all the PSU rails - all were in spec. However after the scope had been powered up for a few hours the EHT tfmr was found to suffer from the usual insulation breakdown. I replaced the EHT tfmr & replaced the valve diodes for silicon diodes. I have a trace but it's not the full width of the CRT, it's "stuck" on the LHS. Suspected hor amp. I've done a lot of checking on the horizontal amp. I took DC voltage readings - noted a V reading on the OP of V584B cathode - +3.95v (should be 325v ish) I checked all the transistors (I'll call em Q's for short) in the scope as well as the diodes. I also checked the valves - all ok. Found some dead Q's - Q543 & Q554, replaced with 2N1893 & 2N4890. also found some dead diodes - D561 & a diode in TB B multi vibrator circuit. I used what I had, not the right Tek parts. So, TB B is working, TB A not, I have limited X trace length also limited Y adjustment & no intensity adj. At the moment I'm concentrating on the X & Y OP circuitry then I'll move onto getting the TB's sorted. Any ideas where to look re X limited trace length? Regards, Andy.

I am looking for the VMT control software (and/or any other software) for the vintage 1996-1999 VM-700T NTSC/PAL video test set. Since this unit has been made "obsolete" by the sunset of the old analog TV transmission protocols, they are no longer supported by whomever took over the Tek video division. My unit has the audio option enabled, among others, and it would be nice to be able to more easily build some automated functions for it. Also are there any CLIP files available anywhere since this unit falls into the "board level exchange" era of servicing.