Re: 7912AD Fails start-up self-test (perhaps)
Adrian and Chris,
The CPU on the CPU board is labelled 6802, the earlier boards had a 6800 processor. My Artek manual shows the 6800 and 6802 interrupt circuitry separately but doesn't have the 6802 MPU board.
Sorry for the confusion over the digital vs XY outputs. The analogue output is all analogue so you will see the trace bloom at high intensity, while the XY output is thresholded so you just see the edges as Chris says. The other major difference is that the analogue and XY scans are 'rotated' by 90 degrees, the analogue scan is just a TV scan while the XY scan is vertical so that the thresholding logic can detect edges for each horizontal (time) position. It can store several on-off pairs for each X position to cope with reading the graticule position. Since the graticule is just a sequence of spots from the write beam, and it looks perfect to Chris and me, there isn't much wrong in XY mode. Can you input a much simpler waveform, but triggered as Chris says, also use a faster timebase to reduce the effective intensity of the write beam.
Regards,
Roger
The analogue image of the graticule appears rotated. Was that from an earlier sequence and reseating boards and cables has now changed things.
I have used the GPIB interface quite a bit, mimicing the original intention of the 7912! There is a choice of reading the dot pairs or the mean value, also automatic centroiding of the graticule and other niceties. I didn't go as far as measuring the geometric distortion from the graticule and using that to correct signal readouts - that was part of the minicomputer software that went with the 7912s
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I acquired one of these function generators recently, together with a TM504 mainframe. While I have sourced a Manual for the TM504 in the UK, the FG504 is another story. I have had no offers so far. There are two on the 'bay, but the one in the USA is a copy and a bit pricey and the other in Germany is too early for my FG504, I think. The serial # of my FG504 is B042933, so I need the later version. I already have a pdf, but I prefer the original. Does anyone have a decent one to spare?
One good thing about buying literature from the USA is that if it is marked as such on the Customs Declaration, then we in the UK don't pay any Customs charges.
TIA, Colin.
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Re: 7912AD Fails start-up self-test (perhaps)
On Tue, Jul 3, 2018 at 02:29 am, Adrian wrote: /g/TekScopes/album?id=62098
As you can see from the pix, I just got the XY display running and while
the display is odd in that it seems to be 'seeing double' (PSU ripple
somewhere?) it is stable at least. Another thought: the trace output on the X-Y display might also be correct, but as if the intensity is set high so you're seeing the edges of a trace which has bloomed to fill half the screen. Do those two dominant horizontal lines move if you adjust the vertical position? Do they get closer together if you turn the intensity down? That's what I'd expect. Chris
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Re: 7912AD Fails start-up self-test (perhaps)
On Tue, Jul 3, 2018 at 02:29 am, Adrian wrote: Yes, "jumpy mess" about describes what I see too! Stills don't do it
justice really, but you can see images here (ignore the apparent lack of
focus, that's shutter speed combined with my 'three-score years and ten'
hands!):
/g/TekScopes/album?id=62098
As you can see from the pix, I just got the XY display running and while
the display is odd in that it seems to be 'seeing double' (PSU ripple
somewhere?) it is stable at least. The graticule display on the X-Y output looks good to me. Mine's exactly the same. You can reduce the size of the little circles by turning down the graticule intensity a whisker. The scan image processing produces one dot where each bright area of the trace starts, and another where it finishes (sort of like the modulus of the differential of the image), so you tend to see the graticule dots and the trace doubled unless the intensity setting is exactly right. Apparently the GPIB data download looks for the midpoint between the dots to give the position of the trace, but I've never tried that. Off to investigate A38 (already changed one tant) power lines...
I had checked jumpers as I looked at various boards but you are right, I
should go through methodically, with the manual, and make sure I didn't
miss one. The link on A28 is set at 625 lines, changing it to 512 shrank
the image vertically as you would expect but made no other difference. It would probably make the lower readouts drop off the bottom of the screen, if you have a 625-line readout board and plugins that display anything in the lower readout fields. One difference between the manual I have (Artek) and this unit is the
A54 MPU, mine is a single board and there is no A52 MPU memory board
fitted (or location for it that I can see). I've uploaded a pic of that
as well. Interesting. I can't remember what mine looks like! Chris
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Re: 7912AD Fails start-up self-test (perhaps)
Hi Chris & Roger Yes, "jumpy mess" about describes what I see too! Stills don't do it justice really, but you can see images here (ignore the apparent lack of focus, that's shutter speed combined with my 'three-score years and ten' hands!): /g/TekScopes/album?id=62098As you can see from the pix, I just got the XY display running and while the display is odd in that it seems to be 'seeing double' (PSU ripple somewhere?) it is stable at least. Off to investigate A38 (already changed one tant) power lines... I had checked jumpers as I looked at various boards but you are right, I should go through methodically, with the manual, and make sure I didn't miss one. The link on A28 is set at 625 lines, changing it to 512 shrank the image vertically as you would expect but made no other difference. One difference between the manual I have (Artek) and this unit is the A54 MPU, mine is a single board and there is no A52 MPU memory board fitted (or location for it that I can see). I've uploaded a pic of that as well.
On 7/3/2018 9:38 AM, cmjones01 wrote: Mine showed similar symptoms. The readout was clear, but the 'analogue' image was just a flickery, jumpy mess. The problem turned out to be a shorted tant (surprise) on the -15V rail on the A38 scan output board
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Re: 7912AD Fails start-up self-test (perhaps)
On Tue, Jul 3, 2018 at 12:12 am, Roger Evans wrote: There is a jumper on the A28 board for 525/625 operation of the composite
video but it should affect the 7000 plugin readout (CPU generated) and the
read gun scanning consistently. There are multiple jumpers for normal or fast
scan and these need to be consistent. Pages 4-9 onwards of service manual 2
give all the jumper settings. If the 7912AD is a 525-line model and you set the jumper on the A28 board for 625 lines, the readout gets repeated at the bottom of the TV display because the readout board's counters aren't set up to deal with the extra lines. There exists a modified readout board (I've got one here as a spare) which has a load of extra logic bodged on to it dead-bug style to handle the readout properly in 625 line mode. If my memory is correct the digital display
does not show the readout from the plugins. You mean the X-Y output or the 'digital' video output? I think the latter does show the readout, but the X-Y output certainly doesn't. Chris
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Re: 7912AD Fails start-up self-test (perhaps)
On Mon, Jul 2, 2018 at 11:32 am, Adrian wrote: Then came the light bulb moment (so to speak) there are lamps, not LEDs
in them thar switches, you don't suppose....? (embarrassed cough) oh
yes, the filaments of the 'TV' and 'Local' lamps both open circuit
although the others were fine. Changed them out, reassembled the panel
and ALL the lights now worked in the expected sequence! Great! Even if we don't quite know why, that's still progress. So on to step 2. I fired up the 634 video monitor and yup a burning
smell and yup another blue tant gone! Do they really hate me that much??
However after fixing that I now see a raster and the readouts from the
plugins - 7A29 and 7B90P - which is some progress.? Advancing the
Graticule and Main intensities produces screen activity but very much
rolling and out of sync in X & Y (although the readout displays are rock
solid) so I guess I now need to read different bits of manual but any
pointers will be very welcome! Mine showed similar symptoms. The readout was clear, but the 'analogue' image was just a flickery, jumpy mess. The problem turned out to be a shorted tant (surprise) on the -15V rail on the A38 scan output board which was preventing the read scan of the target working properly. The result was that the video was showing a highly magnified image of the centre line of the target. You can infer whether a lot of things are working by playing with the intensity controls. With the timebase free-running or in AUTO mode (otherwise nothing, not even the graticule, gets written on to the target) try turning up the graticule intensity. Does the screen brighten? Try also turning up the trace intensity. Near the top of its range the 'reduce intensity' LED should come on. Before that the trace should bloom dramatically. Leave the intensity set to a level below which the 'reduce intensity' LED lights and try twiddling the vertical position through its range. You may find there's a position at which the trace passes through whatever read scan is going on, and the video output goes all white. It helps a lot to visualise the write scan and read scan when trying to reason about what you're seeing. It's normal for the video output to be a bit flickery when the timebase is auto-triggering. Because the graticule only gets written when the timebase triggers, and the timebase's auto-trigger is not synchronised with the video output, there's a constant tussle between the two timings. Give the timebase a trigger signal and it all gets much better. Dare I turn on the 624 X-Y display and look at the digital images?
Probably, but I'm checking ohms on the power rails first this time! Give it a try. Remember that you'll only get X-Y output when you press the 'DIGITAL' button and the timebase has triggered. The X-Y output will show the trace frozen. It will only update with a new trace on each press of the 'DIGITAL' button. The setting of the intensity control that gives good results in digital mode is likely to be somewhat different from the optimum setting in TV mode. Chris
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Re: 7912AD Fails start-up self-test (perhaps)
Adrian,
There is a jumper on the A28 board for 525/625 operation of the composite video but it should affect the 7000 plugin readout (CPU generated) and the read gun scanning consistently. There are multiple jumpers for normal or fast scan and these need to be consistent. Pages 4-9 onwards of service manual 2 give all the jumper settings. If my memory is correct the digital display does not show the readout from the plugins.
Regards,
Roger
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I brought home today a 11403A.
But when I got it home the "MENUS" -> Waveforms button had vanished.
I can salvage buttons off the stack of 11401 and 11402s that are going in
the scrap pile so no problem there.
but does anybody know if there's a procedure is there a lip behind the
button where maybe the bezel has to come off ?
All the years of using 11k scopes this is never happened to me.
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Hi Fabio, Thanks for your comments. The film cap seemed like it was zdded
as a repair attempt and wasn't particularly large. Maybe 7 mm square and
clearly marked 47 mf. Like a small blue chicle. I have lots of similar
sized caps for use as tone caps but of less capacitance. They are usually
of higher voltage ratings. I believe this one was 63v. Ill check to see if
i tossed it.
The - 8v is the only rail that is still low. Ill do some further testing
tomorrow hopefully. We can get some pretty close lightning strikes during
our monsoon season and that can cut into my bench time. My wife is in the
states for a month also and it takes allot for me to also keep up with what
she does for us too. I did take time to watch Brazil ice Mexico today.
We're used to it by now. At least now I know someone from Brazil to
congratulate on a good game. Good luck on the next games.
I'll report my findings and will certainly have questions, but it seems the
logical next step is to clean out the trash in the -8v rail.
Thx, Russ
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On Monday, July 2, 2018, Fabio Trevisan <fabio.tr3visan@...> wrote: Hello Russ,
Glad to hear that the +15V PS woke up, and by consequence, the +5V and
also, somewhat, the -8V (although this one is clearly on the lack).
I have two comments...
1. I got confused by some post of another member, after yours #149308,
still providing suggestions for the low +55V condition... as if it would
still be on the low side.
This takes me to conclude that it's not very clear to everybody there's
nothing wrong anymore, either with the +55V, or with the +15V.
Maybe you can elucidate a little on that to avoid further misunderstanding.
I`m also somewhat puzzled by the description of the capacitor you found
guilty at the C1549 position.
There couldn't be a mylar capacitor there... first because a 47uF mylar
capacitor would be humongous and wouldn't even fit in that space... second
because it would be very unlikely to fail under such low voltage... The
least voltage I've ever seen a film capacitor was something like 63V.
Well, me puzzled or not... it seems you grabbed the bulls by the horn.
Cheers for that.
2. Regarding the -8V power supply... I'm afraid that, while you were so
lucky on the +15V side, to find the shorted culprit in the very first
attempt, you may not be so lucky this time... First because it's not a
"dead short"... it can be just something drawing too much current (such as
another decoupling capacitor), or maybe the -8V power supply is at fault.
Anyway, when you find a wrong power supply rail, there's not much
troubleshooting advice than to hunt down the power sucker... it can be
anything connected to that particular rail.
Sometimes you're lucky and that supply is distributed through connectors
and cables... and in such case, you can rule-out possible culprits by just
lifting the pin on the connector, narrowing down the number of places to
look for possible culprits.
The -8V power supply looks rather unintuitive, because they chose to make
it a "positive supply", and hook the "regulated" positive output to ground,
while taking the negative output from the "unregulated" output of the
rectifier and bulk capacitor.
But other than that, it is and it works exactly the same as the +15V
supply, and the troubleshooting is also the same, just transposing the
measurements to the corresponding components.
Kindest Rgrds,
Fabio
P.S. Sorry for your fellow folks there in MEX. Today was our lucky day
(I`m Brazilian).
On Fri, Jun 29, 2018 at 10:57 am, musicamex wrote:
One step closer! C1549 looked like it might have been replaced with a
mylar
cap. As soon as I unsoldered one side and turned on the scope, the fan came
on! So i replaced it with a 47mf 25 v electrolytic and now had a bit of a
trace but way off vertical axis. Good call Albert!
The voltages now are112.5, 55.66, 15.1, 4.9 and -6.4
I see that the vertical axis is associated with the -8 rail and read the
troubleshooting for vertical axis anomalies but before I go further I thought
I check for advice here first.
Thanks in advance, Russ
--
Good judgement comes from experience; experience comes from bad judgement.
99 times out of 10 a blown fuse is not due to a bad fuse.....
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Just to let ya'all I posted the DC508 on Ebay with pictures it does power on and read outs are perfect like i said it looks to be new not used or used very little.
Jim
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Re: TDS5xx Recap was TDS5xx upgrades/mods
On 2018-07-02 9:04 PM, Miles Paulson wrote: Got the scope, and upon inspection it does in fact need a recap. Fortunately, I don¡¯t see much carnage. I know for the 24x5 series there is much debate on what series Nichicon or Panasonic caps to use. Is there a preferred cap series to use in these series of scopes? I plan to make a Mouser purchase soon, and want to try to get everything in one swoop.
So I suppose I'd better check out the guts of my TDS460A... --Toby
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Re: TDS5xx Recap was TDS5xx upgrades/mods
Got the scope, and upon inspection it does in fact need a recap. Fortunately, I don¡¯t see much carnage. I know for the 24x5 series there is much debate on what series Nichicon or Panasonic caps to use. Is there a preferred cap series to use in these series of scopes? I plan to make a Mouser purchase soon, and want to try to get everything in one swoop.
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-----Original Message----- From: [email protected] < [email protected]> On Behalf Of Miles Paulson Sent: Monday, July 02, 2018 11:57 AM To: [email protected]Subject: Re: [TekScopes] TDS5xx upgrades/mods Thanks for the info! About what I expected though. It seems like the letter scopes are much more popular, probably because of their hackability. I still think I got a good deal on this scope (Paid less than $200 shipped), all it appears to really need is a recapping. I have read about the horror stories about damaged passives and traces, so I hope this one isn¡¯t very bad off. It is supposed to be delivered today, so I will be able to get a better idea later today. -----Original Message----- From: [email protected] < [email protected]> On Behalf Of zenith5106 Sent: Saturday, June 30, 2018 3:36 PM To: [email protected]Subject: Re: [TekScopes] TDS5xx upgrades/mods On Sat, Jun 30, 2018 at 12:37 pm, Miles Paulson wrote:
I just purchased a TDS520 non letter scope. I am still waiting for it
to be delivered, and I will need to recap it as it has a few errors.
But, I have been looking without much success for any upgrades or mods
for the non letter scopes. I have been wondering if it is possible to
upgrade the 520 to a 540 without much fuss. Also, I am wondering if
it's possible to add a VGA out like the letter scopes?
Thanks
TDS520 and TDS540 share most of the hardware so it can be done but probably with more fuss than you want. Since the Acq boards are totally different you will need such a board from a TDS540, TDS540A or TDS544A. You must also be able to load TDS540 firmware and then perform a complete Adjustments procedure which takes hours and require calibration instruments like a DC calibrator and a leveled 500 MHz signal generator. Adding a couple of BNC connectors on the rear panel has to done if you want it to be like a TDS540. As far as I remember there is no VGA connector on the CPU/Display board. /H?kan
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Re: Transistor Full Documentary
No kidding, CWRU offered you a job?? That's my alma mater; I got my BSEE there in 1988.
Moved out to Southern California 30 years ago this September.?
Small world!
Jim
Sent from my Verizon, Samsung Galaxy smartphone
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-------- Original message --------From: Jeff Urban <JURB6006@...> Date: 7/2/18 3:45 PM (GMT-08:00) To: [email protected] Subject: Re: [TekScopes] Transistor Full Documentary Sorry, I only scanned it because I can't sit through something that long. I mean not only mentally, but physically. But, the transistor is one thing that the US does get credit for, period. That and the first fully compatible color TV system. I could go down in the basement and watch it where I have a much better place to sit, but if I am going to spend an hour down there I am going to do something, From what I saw of it, that video should be presented in engineering classes, first year. Give them a connection to the past and realize that everything was not invented in their lifetime. Not all at once, in a half hour class, give them 15 minutes at a time, then have a discussion about it. I was offered $ 35 an hour to teach basic electronics at Case Western Reserve U in Cleveland. I gave it some thought, and while i think it could turn out good, all the other stuff, developing a curriculum, and then tests, and if too may students get a certain question wrong them I must adapt, figure that I failed to teach that part. It would be a job that I took home all the time and I valued my spare time. But yes, I would have had that in there, but first I would have one about vacuum tubes. Actually I would like a transcript of a video like that. I don't really need the visuals. Glad you posted it, I might watch it in spurts, downstairs. In my uncomfortable chair that? is good for my back. Thanks.
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Vintage Tek Museum - sacn of microfiche?
How's that effort going? I'm particularly interested to get a scan of the
RPR, and also Wizards Workshop
Dave
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Re: 7854 readout does not conform to specification? (7L5 problem)
H?kan,
Do you have scans of the Wizards Workshop articles. They sound like an incredibly useful reference.
Dave
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-----Original Message----- From: [email protected] [mailto: [email protected]] On Behalf Of zenith5106 Sent: 02 July 2018 23:02 To: [email protected]Subject: Re: [TekScopes] 7854 readout does not conform to specification? (7L5 problem) This problem was addressed In a WW (Wizards Workshop) article from 2-85 which
said it was fixed by Mod 50646. It is only a change of one resistor value in the 7L5:
Change R2340 on the Vertical Board (A200A2) from 150k to 49.9k.
/H?kan
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Re: Looking for Rare Trace Rot/Trace Sep Pot for 556
Does either pot work ? I suspect the separation might be one of their fancy play pots, it moves one pot so much and then the other after like 7 degrees or so of rotation. The trace rotation can usually be subbed anywhere, it should rarely need adjustment. Most of the need for it is because of tolerances in the CRT, not the Earth's magnetic field. if it was the Earth's magnetic field you would see the trace move if you had a speaker next to it, the poles of the Earth are very weak.
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Re: Transistor Full Documentary
Sorry, I only scanned it because I can't sit through something that long. I mean not only mentally, but physically.
But, the transistor is one thing that the US does get credit for, period. That and the first fully compatible color TV system.
I could go down in the basement and watch it where I have a much better place to sit, but if I am going to spend an hour down there I am going to do something,
From what I saw of it, that video should be presented in engineering classes, first year. Give them a connection to the past and realize that everything was not invented in their lifetime. Not all at once, in a half hour class, give them 15 minutes at a time, then have a discussion about it.
I was offered $ 35 an hour to teach basic electronics at Case Western Reserve U in Cleveland. I gave it some thought, and while i think it could turn out good, all the other stuff, developing a curriculum, and then tests, and if too may students get a certain question wrong them I must adapt, figure that I failed to teach that part. It would be a job that I took home all the time and I valued my spare time.
But yes, I would have had that in there, but first I would have one about vacuum tubes.
Actually I would like a transcript of a video like that. I don't really need the visuals.
Glad you posted it, I might watch it in spurts, downstairs. In my uncomfortable chair that is good for my back. Thanks.
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Re: 7854 readout does not conform to specification? (7L5 problem)
On Mon, Jul 2, 2018 at 01:03 pm, Nenad Filipovic wrote:
I wonder if all 7L5s (including ones with new digital boards) suffer from
this problem in 7854. I already lost weeks trying to fix this and I'm quite
disappointed. Conversion to make 7854 capture 7L5 spectrums was piece of
cake, but this "tiny" readout bug is a nightmare if you make a lot of
average level measurements.
If anybody has any hints or extra documentation on 7854 readout, I'd
appreciate any help...
This problem was addressed In a WW (Wizards Workshop) article from 2-85 which said it was fixed by Mod 50646. It is only a change of one resistor value in the 7L5: Change R2340 on the Vertical Board (A200A2) from 150k to 49.9k. /H?kan
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Parting out 465 (not B) and a 464
You may have read my previous thread on attempting to repair these, but that is not to be. I've decided to part these out. Probably too heavy/expensive to ship complete (for what you want to pay for them).
465 SN B175976: Was working until I somehow killed the CRT HV circuit, so I believe the other boards work fine. I think the CRT tube and the feet are already claimed (not 100% sure).
464 SN B2000087: Never worked in my hands. I bought it from a guy who said it was stored for more than 10 years. Same problem- no trace, not dot, probably a CRT HV problem as well. Internally, this is the cleanest scope I've ever seen. No feet.
If you are interested in any parts from these please contact me in PM or email (stuff@...), NOT on this forum. Make a reasonable offer. If international, don't forget shipping overseas is expensive and time consuming!
Keith Ostertag
New Albany, IN 47150
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David C. Partridge
Jeff Urban
zenith5106