Keyboard Shortcuts
ctrl + shift + ? :
Show all keyboard shortcuts
ctrl + g :
Navigate to a group
ctrl + shift + f :
Find
ctrl + / :
Quick actions
esc to dismiss
Likes
- TekScopes
- Messages
Search
|
Tektronix 155-0065 needed!
Hi!
I have problems with the vertical output of my 7904 and was suggested to swap U745 (155-0065) on the vertical output board since I also have a 7844 which uses the same IC. This solved the problem and I now need to find a 155-0065 so I can have both scopes running again. Anyone have this part available? All the best, Henric from Sweden www.facebook.com/hermanssonamplification |
|
Re: Help! I bricked a perfectly functioning 2467B!
On Wed, Apr 10, 2024 at 07:17 PM, Mark Litwack wrote:
...... If you want to upload your cal data to the forum files area I can preload the program with itMark, I hand-wrote the cal data from my scope. I have it saved on my computer in a pdf format. Will that work? If it won't, I can make a text file if that will be easier for you to copy and paste. Let me know. Thank you for your help! Don |
|
Re: Help! I bricked a perfectly functioning 2467B!
Hi Don,
toggle quoted message
Show quoted text
That was fast! I'm glad to hear they worked without a hitch. My W27C512 chips are still winding their way through the USPS. After they (hopefully) pass the same in-scope test in my 2445A, I will be able to finish the code I started years ago to do the cal data copy. I didn't have the 2445A back then, so I won't be flying blind this time. If you want to upload your cal data to the forum files area I can preload the program with it to save a little time and maybe less typing errors. In the final version, I was thinking I would just provide a data block filled in with data that represents the cal data address, e.g., 00 00, 00 01, 00 02, ... 00 FE, 00 FF (512 bytes total). People can use a hex editor to edit the program binary and input their cal data into that block. Having the data initially set to the cal data address would help people keep track of and/or verify the address as they are inputting their cal data. And of course I'll provide the source for those who want it. I recently bought a Xgecu T56 to replace an old GALEP-4. The GALEP-4 was nice, but unfortunately needs a parallel port which is becoming increasingly rare. -mark On Tue, Apr 9, 2024 at 06:40 PM, Don wrote:
Mark, |
|
For Sale RTM-506 with plugin's
Have had a change of direction am going to keep the 466 and finish the repairs. Still need to off load the extra stuff though. Here is the list.
RTM-506 w/2 manuals. $150.00 for the bunch plus S&H and or local pickup. DM-501 w/2 DM-501A manuals SG-503 early SN#068393 w/manual some damage to front panel and knobs. PG-501 no manual I need for the PG-506 late the red lens cover and the top var knobs. Also want to sell the extra 4xx scopes that I won't use or fix. 1-466, 1-475 w/DM-44, 475 w/DM-44, no extra manuals for them. Jim O A |
|
Re: 7B87 max acquisition speed in single-shot
Hello Max.
I guess, the clock of the 7B87 is not the sample clock of the ADC. As I understood, it is the delay or pre-trigger clock for trigger events. The 7854 also aquires data when used with a 7B85 despite generating an error message. Pre-trigger is not available with 7B85, but the aquired data seems to be correct. You need the Waveform Calculator keyboard or a GPIB connection to change the record length. I did some experiments with single shot: 512 points —> max. 500 microseconds / div 256 points —> max. 200 microseconds / div 128 points —> max. 100 microseconds / div This would equal a sample rate of about 100 kHz (10 microseconds per point) using internal 10 MHz clock. Maybe: You have to apply an external clock for maximum sampling rate of 500 kHz. Regards, Gerrit |
|
Re: trigger problem with 7B70
Adam has one newer, one older revision of the plugin where supply of R176 changed from -50V to -15V and resistor was updated accordingly. Colors show measurement between those two units.
toggle quoted message
Show quoted text
Ozan On Wed, Apr 10, 2024 at 02:58 PM, Mark Vincent wrote:
|
|
Re: trigger problem with 7B70
Adam,
Your voltages at TP78 sounds way off! There is no way a 10 ohm 1/4W resistor would last with 65V across it! Is it possible you typed in the wrong voltage at that test point? The 49,9V would be correct. I am suspect of the 4300 ohm resistor. In mine, I put in a 2W (15mm body length). I wonder about the two 200 ohm resistors, R173 and R179. If carbon, check by removing a transistor at one end of each then measure the resistance. I have seen these resistors out of tolerance. Also see what C178 is rated at. If a 50V type, replace with a higher voltage type. I have seen the rated voltage of a condenser be the same as the voltage across it in other Tek. gear. Check R175, R177, R181 and R182. The voltages being off make me suspect one or more of the resistors needs to be replaced. Mark |
|
Re: trigger problem with 7B70
Hi Adam,
toggle quoted message
Show quoted text
The voltage difference between schematic values and what you measure could be because of how your meter reacts to average value. Which equipment do you use for measuring DC voltages? You could check with an oscilloscope since 400mV delta in average value is large enough to see on an oscilloscope. I have more comments and will follow up with a direct message but I wanted to send a quick note: base voltages of Q181/Q182 shows an issue. This voltage is generated by a resistor divider (R181. R182, value of R182 is 3.3k, not 3.3ohm as schematic shows) and only connection is to the bases. With no signal are the bases of bad one still 0.4V lower than good/schematic voltages? If that is the case Q181/Q182 may be faulty. If at DC voltages look good without signal, then clamp diodes CR181/CR182 may not be doing their job and letting Q181/Q182 saturate. Ozan On Tue, Apr 9, 2024 at 11:45 PM, Adam R. Maxwell wrote:
On Apr 9, 2024, at 14:31 , Ozan via groups.io <ozan_g@...>wrote:supplies inside the plug-in (or mainframe) to be off. Most likely -15V or -50V |
|
Re: Need advice
Hi;
I have forwarded your email to Dave and Steve, see if either responds. Ken On Wed, Apr 10, 2024 at 9:23?AM giorgio@... <giorgio@...> wrote: Hello again, |
|
Re: trigger problem with 7B70
On Apr 9, 2024, at 14:31 , Ozan via groups.io <ozan_g@...> wrote:That sounds logical, but all the LV supplies are within spec. I do get ~1.8V at emitter of Q170 if I disconnect the EXT trigger input. I can't make sense out of that 400-500mV difference. If supplies are good:I've taken measurements and annotated the schematic (low serial version), which includes a better waveform from my hardcopy manual. The waveform at base of Q170/Q171 is the same as the schematic in both plugins, Red annotations are the bad plugin, green are the good plugin. Both under the same input conditions, same settings, and same mainframe slot. thanks, Adam |
|
Re: Tek 26G1 Rate / Ramp Generator plug-in ??
Hi,
So I used a bunch of these modules when I ran a neurophysiology research lab. The 26G1 was one of a family of modules used for making timing pulses to control stimuli. There was also a very good differential amplifier. The mainframe was unique. It had a pull-out drawer where you would insert purpose made jumpers to send signals from one module to another. In this way every researcher would have their jumper board and when they ran an experiment they would insert their custom-configured board into the mainframe and set up all the module interactions. The modules do not directly plug into a standard Tek mainframe, although they look like they should. It was very fine physiology lab gear in the day! =Randy= |
|
Re: Help! I bricked a perfectly functioning 2467B!
On Sat, Apr 6, 2024 at 01:24 PM, Mark Litwack wrote:
Mark, I have received the EPROM programmer and a couple of the Winbond W27C512 chips (both from Amazon). I was able to confirm that the programmer (an XGecu T48) was able to successfully write to the Winbond chips. I loaded the version 10 firmware (that I got from the files section here) on to the Winbond chips and upon installing in the scope in place of the original EPROM chips, the scope appeared to function as it did with the original firmware chips (which in my scope are version 09). So, I think we can proceed with the experiment to see if we can load my saved cal data to the scope's NVRAM. Let me know when you are ready to proceed. Don |
|
Replacing NVRAM in a TDS680C scope
I run from any digital scope, I don't want to deal with the drama of finding parts and softwares. HOWEVER- there is a (transgender) gal on YouTube who is quite amazing in her abilities to restore almost anything. Go to Youtube, enter a search for "Glasslinger". You can easily find her replacing the NVRAM in a TDS680C. Her abilities with an incredible variety of equipment are amazing.
? Bruce Gentry, KA2IVY |
|
Re: trigger problem with 7B70
Hi Adam,
My comments are below: On Tue, Apr 9, 2024 at 08:22 AM, Adam R. Maxwell wrote: With 1kHz/1Vpp sine applied to EXT and conditions specified in the manual:All the waveforms show phase inversion at sine wave peaks, usually it happens when BJT transistor base is driven beyond forward biasing B-C junction. I don't see this effect in the expected waveforms, although the plot at that point is very fuzzy. If you look at earlier nodes you will probably see the same inversion, and the plots look better. Good Q170E/Q171E: -1.35/-1.34V to chassis groundThese voltages are about ~ 400mV-500mV higher than the schematic values. Although we expect some difference 400mV+ is too much in my opinion. I did a back of the envelope calculation and I also come up with closer to schematic voltages. When you consider common mode rejection of Q150/Q160 it needs a large error in the emitters of Q150/Q156 to create a 400-500mV error in emitter voltages of Q170/Q171. Since both plug-ins show the same DC operating point my guess is one of the supplies inside the plug-in (or mainframe) to be off. Most likely -15V or -50V is off as it is one of the difference in the plug-ins. If supplies are good: If you start measuring base/emitter/collector voltages going towards input you would find where it deviates from schematic values. Both plug-is may have the same issue but a power supply problem at the mainframe is more likely. One design may be more tolerant than the other (-15V/-50V difference). I think you mentioned mainframe is a new acquisition too. Ozan |
|
Re: TDS744A tick tick tick when power on (and something smelling)
Hello,
Update and hope for some help... It may be that Q540 indeed is broken (Q510 likely isn't - its bias just shorts the BC junction), but it will not really cause any current draw. Running the A32 board separately only drew some 40 mA on 75 V line. I doubt this loads the high voltage supply too much. So, when not finding any shorted caps on any board, next step was to supply A30 board with the 5.1 V and 25 V it is expecting (A32 video board disconnected). Here comes the problem. The 5.1 V line only draws some 40 mA max, but already at 12 V on the 25 V line, it draws 800 mA. Anode voltage is then approximately 8 kV so everything appears to be working, but how much current is really needed and what is the final voltage of the anode where regulations starts? Hope it isn't anything near 15 kV - my lab supply can only provide a bit above 1 A. I checked running the supply with my HV probe disconnected and got similar levels of current so I don't think I'm loading the supply in any bad way. Does anybody know what current to expect for the 25 V line? Anode voltage? Given that nothing appears to be truly shorted, I guess there is a risk of breakdown in the HV supply itself once it reaches high enough voltage - common failure? Way back I fixed a 475 that had this problem. That supply was actually available from Mouser (IIRC). Probably not that fortunate here - although this should be a fairly regular CRT - no need for fast sweeps etc? Any suggestions or comments are very welcome. As of now I'm halting a bit since I don't want to blow anything up... Regards, Staffan |
Jean-Paul
to navigate to use esc to dismiss