Re: 7704A PS - Rapid Tick Mode
Bad tantalum, C3396, on the OUTPUT SIGNALS board. Replaced C3395 and C3396 and all is working again.
Thanks,
Barry - N4BUQ
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Thanks, Jean-Paul, Mark, and Tom,
The relaxation oscillator I was referring to is the one that makes the neon
flash which is comprised of R3019-C3019-DS3019.
I was originally writing the above email when it suddenly occurred to me that
after removing the power supply from the scope, I had not connected the dummy
load so, of course, it was ticking! I connected the dummy load and the PS came
to life normally.
I now need to find out what has gone bad in the scope itself. As has been
suggested, it's likely a shorted tantalum and, if I had my guess, it's probably
one of the ones on the main interface board where the sense line connects. At
least now I know better where to look for the problem.
Thanks to all who replied,
Barry - N4BUQ
When there is an overload, the PS shuts down and tries again a bit later. Each
tick is the sound made by the magnetics as current starts to flow then shuts
off. No master oscillator drives the tick frequency. The whole PS is acting as
a relaxation oscillator in response to the overload.
Most likely you have a shorted tant somewhere, but whatever the cause, just
follow the standard debug tree. There¡¯s a terrific writeup for the 7000 series;
it¡¯s been referenced here a lot.
Good luck!
Tom
Sent from an iThing; please forgive the typos and brevity
On Dec 7, 2024, at 15:38, n4buq <n4buq@...> wrote:
?I powered up one of my 7704As which worked fine the last time I used it several
?months ago. This time it worked for about 30 seconds and stopped with the
?power supply going into a rapid tick mode which I presume the frequency of the
?relaxation oscillator.
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Wanted: Manual for OT502 E/O Converter TM500 Module
Hi,
I just picked up an OT502 E/O Converter TM500 Module in a mainframe of assorted modules, and am looking for a user/service manual for it. There doesn't seem to be much online..
If anyone has a copy, paper or digital, please let me know!
Thanks,
Jared
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Re: 7704A PS - Rapid Tick Mode
Thanks, Jean-Paul, Mark, and Tom,
The relaxation oscillator I was referring to is the one that makes the neon flash which is comprised of R3019-C3019-DS3019.
I was originally writing the above email when it suddenly occurred to me that after removing the power supply from the scope, I had not connected the dummy load so, of course, it was ticking! I connected the dummy load and the PS came to life normally.
I now need to find out what has gone bad in the scope itself. As has been suggested, it's likely a shorted tantalum and, if I had my guess, it's probably one of the ones on the main interface board where the sense line connects. At least now I know better where to look for the problem.
Thanks to all who replied,
Barry - N4BUQ
toggle quoted message
Show quoted text
When there is an overload, the PS shuts down and tries again a bit later. Each
tick is the sound made by the magnetics as current starts to flow then shuts
off. No master oscillator drives the tick frequency. The whole PS is acting as
a relaxation oscillator in response to the overload.
Most likely you have a shorted tant somewhere, but whatever the cause, just
follow the standard debug tree. There¡¯s a terrific writeup for the 7000 series;
it¡¯s been referenced here a lot.
Good luck!
Tom
Sent from an iThing; please forgive the typos and brevity
On Dec 7, 2024, at 15:38, n4buq <n4buq@...> wrote:
?I powered up one of my 7704As which worked fine the last time I used it several
?months ago. This time it worked for about 30 seconds and stopped with the
?power supply going into a rapid tick mode which I presume the frequency of the
?relaxation oscillator.
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Re: 7704A PS - Rapid Tick Mode
Barry,
A few things that could cause the fast ticking are: one/both transistors from the 0067 IC to the driver transformer bad, the 9V zener to the 0067 open, the two 1mfd filters from the small toroid transformer high ESR (some models say ,1mfd), the two electrolytics on the bottom board (1 and 2mfd) bad (I replaced them in mine with 1 and 2,2mfd of 250V or higher film types because the electrolytics were drying out (high ESR)), diodes around the two TO-3 power transistors or series pass transistor bad or the collector shorting to the heasink. Early models of some series did not have damper diodes from C to E while later serial numbered ones did. If yours does not have the dampers, add them. They have to be fast or very fast 600-1000V 1A types. Note where the position is on the inverter control, clean the pot then rotate it. That pot could be dirty. I have heard of the 120V zener in the power supply going bad causing ticking. I have seen one of these bad before which I replaced with a 1,3W type (BZX85B series).
Another thing could be a ribbon connector being disconnected enough to not make contact while looking like it is fully seated.
The highly likely problem already mentioned is shorted condenser(s). If yours still has the original filters for the 50V supplies, they are suspect. Those should be 100V (UHE is a good replacement). I will assume you noticed the fast ticking even with no plug-ins installed.
The B+ should be 305-310V with new/healthy filters.
Mark
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Re: 7704A PS - Rapid Tick Mode
When there is an overload, the PS shuts down and tries again a bit later. Each tick is the sound made by the magnetics as current starts to flow then shuts off. No master oscillator drives the tick frequency. The whole PS is acting as a relaxation oscillator in response to the overload.
Most likely you have a shorted tant somewhere, but whatever the cause, just follow the standard debug tree. There¡¯s a terrific writeup for the 7000 series; it¡¯s been referenced here a lot.
Good luck!
Tom
Sent from an iThing; please forgive the typos and brevity
toggle quoted message
Show quoted text
On Dec 7, 2024, at 15:38, n4buq <n4buq@...> wrote:
?I powered up one of my 7704As which worked fine the last time I used it several months ago. This time it worked for about 30 seconds and stopped with the power supply going into a rapid tick mode which I presume the frequency of the relaxation oscillator.
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Re: 7704A PS - Rapid Tick Mode
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7704A PS - Rapid Tick Mode
I powered up one of my 7704As which worked fine the last time I used it several months ago. This time it worked for about 30 seconds and stopped with the power supply going into a rapid tick mode which I presume the frequency of the relaxation oscillator.
I opened it up and using an autotransformer to slowly take the voltage up, I observed DS3019 flashing in time with the ticks. At first, the ticking is much slower but as I increase the input voltage, the ticks get faster and are fastest at full input voltage. I checked across CR3015 and the voltage is getting up to what I remember as a normal level (don't remember what I measured but since that circuit develops peak-to-peak the line voltage value, it should be around 350vdc which I think is close).
I know what "normal" tick mode sounds like but this seems to be something that's occurring before the startup circuits are at work causing the the "normal" ticks. Is it likely that the inverter is never getting to the point of trying to start? If so, then I presume the inverter controller chip isn't working or, at least, isn't seeing what it needs to work. Is that a reasonable assumption?
Thanks,
Barry - N4BUQ
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I ground a slight taper on the top of the posts with a tapered Dremel grinding wheel. I vacuumed the cavity and then blew it out at low pressure with an air hose. I remember the HVPS it came out very hard. I really had to pull on it.
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On 7 Dec 2024 11:45 am, Roy Thistle wrote: How did you 'grind" the 'posts' ... with a Dremel? There are dozens of Dremel tool accessories, and other manufacturers have made accessories which can be used with a Dremel tool. I own 25 grinding accessories for my Dremel tool, mostly aluminum oxide or silicon carbide. -- Dale H. Cook, GR/HP/Tek Collector, Roanoke/Lynchburg, VA
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On Fri, Dec 6, 2024 at 07:00 AM, Robert Lookingbill wrote:
I ended up grinding a slight taper on the top of the posts.
I may.... or others may... have to remove the HV assembly... and hopefully put it back. If you get a chance... If it came out... why wouldn't it go back? How did you 'grind" the 'posts' ... with a Dremel?... why not a file?... and where did all the swarf go? -- Roy Thistle
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Re: 1780R Dallas chip replacement
*Mouser and others sell adapter boards, or you can buy blanks on Ebay and add the header pins.* *Many mergers have caused new brand names on these parts.* On Thu, Dec 5, 2024 at 8:35?PM Mark Vincent via groups.io <orangeglowaudio= [email protected]> wrote: I have a 1780R I want the Dallas chip(s) replaced with new chips like ones
that can be done on a 2465B (fram/Ramtron/etc.). I do not have a reader or
capacity to make the surface mount chip and board with pins to plug in the
original socket. Who here will do this? I can send the chip/board(s) to be
replaced. Thanks.
Mark
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Re: Tek MSO4104 remote measurements via USB or GPIB
It's OK I've got this sorted now. I looked through another Tektronix programming manual for a different scope and it describes the OPC operation much better. It's all working fine now :)
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Tek MSO4104 remote measurements via USB or GPIB
Hi
I'm currently trying to make some remote measurements (via USB) on a pair of repetitive waveforms using a Tek MSO4104. They occur about once a second and I want to measure the time interval between them (CH1 to CH3). This is easy to do manually and then read the data off the screen, but I want to do it many thousands of times during an extended test and log the results and I don't want to miss any events. So I need to do this via USB or GPIB. I'm currently using USB and I can control the scope remotely just fine over USB for most commands.
However, I'm struggling to get this measurement process to work properly when doing it remotely. This initially appeared to be a simple task, but I can't work out how to ask the scope to make a measurement at the relevant time and to then report it back to my PC via USB. I assume I have to use the *OPC or BUSY or *WAI commands and let the PC wait for the scope to spit out the measurement data. I've set a suitably long timeout.
I've tried normal trigger mode and single shot. Has anyone done this kind of thing before? I assume I either have to poll the event status register or find some way of getting the scope to time everything and then spit out the result via USB.
Thanks in advance for any replies :)
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I know this is an old discussion, but hopefully it is still active. I finally found the problem to be diode D940 in the high voltage power supply was open. I replaced it with a 2CL2FL diode and the scope works fine. I had a lot of trouble getting the high voltage assembly back on the four mounting posts in the chassis. I ended up grinding a slight taper on the top of the posts. I want to thank everyone for their help, especially Mark Vincent and John Sykes.
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Re: 7L13 full-screen amplitude troubleshooting
Forgot to mention that the output of the 1st mixer seems reasonable as far
as I can tell. I saw three frequencies at the output of the first mixer:
- -43 dBm @ 2.14178 GHz
- -40.8 dBm @ 2.1579 GHz
- -45.3 dBm @ 2.1678 GHz
The first and third changes in amplitude and frequency if I adjust the
input signal. The 2nd one doesn't.
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Re: 7L13 full-screen amplitude troubleshooting
After acquiring a TinySA Ultra which allows me to generate and analyze
signals at higher frequencies than I've been able to, I decided to put my
7L13 back on the bench.
To recap, with the 7L13 set for a reference level of -30 dBm and no
attenuation at the input, a -30 dBm signal should produce a full screen
deflection (for the frequency of the input signal). There are a few places
in the manual that denote what the level should be at specific places in
the circuit to achieve this.
For a -30 dBm input, after going through the first two mixers, the 105 MHz
IF should be at -45 dBm. What I measure is approx -90 dBm @ 106.102 MHz. If
I insert my own -45 dBm signal at this point (via W80 into J80), I do
indeed get full screen deflection so it seems that the issue lies
somewhere around the 2nd mixer. Possible suspects are therefore
- A10: 2.2 GHz LP and BP filters
- A11: 2nd Mixer
- A20: 2nd LO, directional coupler, band filter
- A40: x22 multiplier, 2.183 GHz BP filter
- A41: Mixer for 2nd LO phase lock
Reference CKT:
How do I go about testing these modules?
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vintageTEK museum 2025 calendar
The vintageTEK museum has completed their 2025 calendar and is offering it for sale at the museum, on eBay, and on the Lulu bookstore. The museum is a 501C3 non-profit educational museum whose mission is to encourage the next generation of engineer and scientist through preserving the history of Tektronix, those that created the legacy, and by supporting STEM in the local community. We do not charge for the museum or our STEM efforts and operate 100% through volunteers, donations, and by sales of items such as the calendar.
This year's calendar commemorates the 60th anniversary of the Tektronix 1965 calendar. The pictures and descriptions for each month are from the 1965 publication. The pictures are of hand paintings by Portland artist Paget Loomis for the 1965 calendar. Each month has notable historic dates indicated while the front and back covers feature the vintageTEK museum. There are links and sample pages at
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1780R Dallas chip replacement
I have a 1780R I want the Dallas chip(s) replaced with new chips like ones that can be done on a 2465B (fram/Ramtron/etc.). I do not have a reader or capacity to make the surface mount chip and board with pins to plug in the original socket. Who here will do this? I can send the chip/board(s) to be replaced. Thanks.
Mark
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Ed, I agree. I have been working on this SC502 for quite some time. This was the issue when I put It aside a year ago.
Thanks for the comment.
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I have the service manual and have restored 2 of these SC502s. I have everything I need to work on these except the experience.
I appreciate the idea of a vertical amp issue as that was not obvious to me. Tomorrow I will look at that circuit!
Thank you!
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Jared Cabot
Jean-Paul
Dale H. Cook
Michael A. Terrell