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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Re: What are these Tek parts for?
A quick check with my buddy Google shows that Nielsen is still in business.
The can best tell you where to find the catch, possible provide samples.
The self tapping screw is available at any well stocked hardware store, or your junque box from old equipment that you have scrapped and kept the parts.
The spacer may be a problem if your are not handy with tools and make your own.
Glenn
toggle quoted message
Show quoted text
On 7/2/2018 3:34 PM, David Berlind wrote: wow.. awesome . .thanks for providing that. Yes, would love some photos and
do you know where I can go to get those parts? Or, am I really just subject
to digging around the aftermarket?
On Mon, Jul 2, 2018 at 3:29 PM, Colin Herbert via Groups.Io <
colingherbert@...> wrote:
I have a 7623A with option #8 (the front cover). The catch hooks on the
scope itself also have a thicker metal stand-off under the hook. If you
can't get the proper items, I can take some measurements and photos to
help. The relevant Tek part numbers are:
105-0390-00 Catch, clamping Nielsen
Hardware Corp. Part No. SC-B-83314
213-0119-00 Screw, tapping, 4-24 x 0.375 inch, pan head, steel.
Central Screw Co.
361-0480-00 Spacer, latch
Tektronix
Good Luck, Colin.
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of David
Berlind
Sent: 02 July 2018 16:58
To: [email protected]
Subject: Re: [TekScopes] What are these Tek parts for?
OK. It appears you are correct about the left part. I now realize that my
OS-245 (milspec 7603) is missing the receiving side of the clips to which
the cover attaches. I've added photos to the aforementioned online image
album <>. So, I'd like to find
those clips if someone know where I can get them. Either that, or I'll have
to fabricate them. I bump into these sorts of clips all the time (trying to
think if there something around the house I can harvest them from).
But the other part pictured does not match up to anything I can tell.
On Mon, Jul 2, 2018 at 6:43 AM, Colin Herbert via Groups.Io <
colingherbert@...> wrote:
One of those looks like the front cover for a series-7000 scope (option
#8). It even still has the foam bits for holding probe parts. I've no idea
what the other thing is, but could it be some kind of implosion screen?
Colin.
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of David
Berlind
Sent: 02 July 2018 02:14
To: [email protected]
Subject: [TekScopes] What are these Tek parts for?
Two parts... some sort of cover.. but I don't think it's for anything I
own. Smells like an old Tek scope too! If I have no need for this and
someone else does, I'd be happy to stick it in a box if you cover postage.
--
-----------------------------------------------------------------------
Glenn Little ARRL Technical Specialist QCWA LM 28417
Amateur Callsign: WB4UIV wb4uiv@... AMSAT LM 2178
QTH: Goose Creek, SC USA (EM92xx) USSVI LM NRA LM SBE ARRL TAPR
"It is not the class of license that the Amateur holds but the class
of the Amateur that holds the license"
|
Hi Hankc,
many thanks for this really nice and interesting video.
Alessandro Cattaneo
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Il Luned¨¬ 2 Luglio 2018 7:47, tek_547 <R.Kelbling@...> ha scritto:
Interesting stuff, thanx!!
|
7854 readout does not conform to specification? (7L5 problem)
Hi Everybody,
This one is for 7000 series readout experts, hope you're out there
somewhere. I have a properly working late model 7854 that I'd like to use
with my 7L5 (early serial with old digital board, successfully converted
for use in 7854, will post full instructions on this modification later as
officially these do not exist for the old 7L5). Everything works fine
except the damn level readout that I really, really need because I heavily
use the 7854 averaging and math functions. The problem can be split in two
points:
1. Incorrect level readout in LIN mode - turning the attenuator should
produce the expected 200mV-100mV-50mV-20mV... sequence, but instead 7854
displays 2mV-1mV-5mV-2mV... and so on in circle (zeroes are omitted, units
and first digit are fine).
2. 7L5 readout driving circuitry can be slightly modified to fix the
mentioned problem, but although that fixes the display perfectly (and is
fully compatible with other mainframes using "classic" readout boards), it
breaks the ability of the 7854 storage to correctly obtain a scale factor
for acquired waveforms. So to summarize:
- If readout is broken in 2mV-1mV-5mV-2mV... way, 7854 acquire command (at
least) captures the same scale factor (2mV-1mV-5mV-2mV...)
- If readout is fixed to show 200mV-100mV-50mV-20mV..., 7854 acquire
command displays a warning and sets 1 as the default scale factor
I believe the problem is fully on the 7854 side, now for some gritty
technical details if you're still with me. 7L5 uses a non-standard (but
still technically perfectly correct) mode to display readout, using all 10
time slots (TS1-TS10). For example the word "200mV" in LIN mode would be
encoded in the following way:
ROW address: 3221115545
COL address: 0003110012
where digit position denotes a time slot (from left to right TS1-TS10). For
comparison word "-123dBV" in LOG mode would be:
ROW address: 2221115545
COL address: 0062346702
Quick reference to the address table:
Column address 0 in TS1 denotes a SKIP operation, it's obvious that the two
zeroes in 200mV are coded in TS5 and TS6 (non-standard format) as opposed
to standard format that uses TS1 to specify "add one zero" or "add two
zeroes" operational addresses. So if 7L5 does a SKIP in TS1, ROW address
should make no difference (as long as it's in 1-9 range). On mainframes
with classic readout boards (tested on 7633 and 7104) it indeed makes no
difference, but on 7854 it painfully breaks stuff:
- if ROW=2 in TS1, readout correctly displays 200mV-100mV-50mV-20mV... but
storage acquire fails to obtain the scale factor
- if ROW=3 in TS1 (7L5 factory default), readout breaks and displays
2mV-1mV-5mV-2mV... storage acquires the (broken) scale factor
- if ROW=4,5..9 in TS1, readout correctly displays 200mV-100mV-50mV-20mV...
but storage acquire fails to obtain the scale factor
7000/7854 readout specification makes no mention of such nonsense. To add
to the confusion, 7L5 service manual mentions Q2325 (page 2-19) that sets
ROW=3 in TS1 in LIN mode (although TS1 COL=0 which denotes SKIP), but with
no explanation. In LOG mode Q2325 is off and ROW=2.
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...
Best Regards,
Nenad Filipovic
|
Yep Albert,
Indeed, it was your post I was referring to... I wasn't sure though, if there was still a misunderstanding that the +55V was at fault.
I see now what you mean... and indeed, the shorted decoupling capacitor on the +15V supply doesn't explain (at least, not directly) why the +55V was low until then.
If nothing else was burnt, than I suppose that the circuits that are fed from the +55V (I think of Vertical amplifier, which is the main power hog for the +55V), by being improperly biased (due to the absence of the +15V) were maybe drawing too much current from the +55V, causing it to be lowered??? That's just a big question-mark yet to be answered.
The absence of the +15V and improper biasing of all its "customers", who knows for how long, may have led to other things burning as well, which may explain the now low voltage of the -8V.
Or it may simply be another dreaded tantalum capacitor.
Rgrds,
Fabio
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Show quoted text
On Mon, Jul 2, 2018 at 11:52 am, Albert Otten wrote:
Hi Fabio,
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.
[snip]
Fabio
That other member must have been me I think. But I wrote this:
I suppose that since 55.66 V is OK the low reading 46.9 V can only be due to
a too heavy load at the +55V rail.
So what I meant is that since there is no problem *now* with +55V, there was
also no problem *earlier*, and the earlier reading 46.9 V can only be
explained by a (then) to heavy load on the +55V rail. I wondered where that
heavy load could come from but didn't find the answer. And apparently nobody
so far (but I guess nobody is searching for that...).
Albert
|
Re: What are these Tek parts for?
wow.. awesome . .thanks for providing that. Yes, would love some photos and do you know where I can go to get those parts? Or, am I really just subject to digging around the aftermarket? On Mon, Jul 2, 2018 at 3:29 PM, Colin Herbert via Groups.Io < colingherbert@...> wrote: I have a 7623A with option #8 (the front cover). The catch hooks on the
scope itself also have a thicker metal stand-off under the hook. If you
can't get the proper items, I can take some measurements and photos to
help. The relevant Tek part numbers are:
105-0390-00 Catch, clamping Nielsen
Hardware Corp. Part No. SC-B-83314
213-0119-00 Screw, tapping, 4-24 x 0.375 inch, pan head, steel.
Central Screw Co.
361-0480-00 Spacer, latch
Tektronix
Good Luck, Colin.
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of David
Berlind
Sent: 02 July 2018 16:58
To: [email protected]
Subject: Re: [TekScopes] What are these Tek parts for?
OK. It appears you are correct about the left part. I now realize that my
OS-245 (milspec 7603) is missing the receiving side of the clips to which
the cover attaches. I've added photos to the aforementioned online image
album <>. So, I'd like to find
those clips if someone know where I can get them. Either that, or I'll have
to fabricate them. I bump into these sorts of clips all the time (trying to
think if there something around the house I can harvest them from).
But the other part pictured does not match up to anything I can tell.
On Mon, Jul 2, 2018 at 6:43 AM, Colin Herbert via Groups.Io <
colingherbert@...> wrote:
One of those looks like the front cover for a series-7000 scope (option
#8). It even still has the foam bits for holding probe parts. I've no idea
what the other thing is, but could it be some kind of implosion screen?
Colin.
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of David
Berlind
Sent: 02 July 2018 02:14
To: [email protected]
Subject: [TekScopes] What are these Tek parts for?
Two parts... some sort of cover.. but I don't think it's for anything I
own. Smells like an old Tek scope too! If I have no need for this and
someone else does, I'd be happy to stick it in a box if you cover postage.
|
Re: What are these Tek parts for?
I have a 7623A with option #8 (the front cover). The catch hooks on the scope itself also have a thicker metal stand-off under the hook. If you can't get the proper items, I can take some measurements and photos to help. The relevant Tek part numbers are:
105-0390-00 Catch, clamping Nielsen Hardware Corp. Part No. SC-B-83314
213-0119-00 Screw, tapping, 4-24 x 0.375 inch, pan head, steel. Central Screw Co.
361-0480-00 Spacer, latch Tektronix
Good Luck, Colin.
toggle quoted message
Show quoted text
-----Original Message----- From: [email protected] [mailto: [email protected]] On Behalf Of David Berlind Sent: 02 July 2018 16:58 To: [email protected]Subject: Re: [TekScopes] What are these Tek parts for? OK. It appears you are correct about the left part. I now realize that my OS-245 (milspec 7603) is missing the receiving side of the clips to which the cover attaches. I've added photos to the aforementioned online image album <>. So, I'd like to find those clips if someone know where I can get them. Either that, or I'll have to fabricate them. I bump into these sorts of clips all the time (trying to think if there something around the house I can harvest them from). But the other part pictured does not match up to anything I can tell. On Mon, Jul 2, 2018 at 6:43 AM, Colin Herbert via Groups.Io < colingherbert@...> wrote: One of those looks like the front cover for a series-7000 scope (option
#8). It even still has the foam bits for holding probe parts. I've no idea
what the other thing is, but could it be some kind of implosion screen?
Colin.
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of David
Berlind
Sent: 02 July 2018 02:14
To: [email protected]
Subject: [TekScopes] What are these Tek parts for?
Two parts... some sort of cover.. but I don't think it's for anything I
own. Smells like an old Tek scope too! If I have no need for this and
someone else does, I'd be happy to stick it in a box if you cover postage.
|
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.
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Show quoted text
-----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
|
Hi Fabio,
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.
[snip]
Fabio
That other member must have been me I think. But I wrote this:
I suppose that since 55.66 V is OK the low reading 46.9 V can only be due to a too heavy load at the +55V rail.
So what I meant is that since there is no problem *now* with +55V, there was also no problem *earlier*, and the earlier reading 46.9 V can only be explained by a (then) to heavy load on the +55V rail. I wondered where that heavy load could come from but didn't find the answer. And apparently nobody so far (but I guess nobody is searching for that...). Albert
|
Re: 7912AD Fails start-up self-test (perhaps)
Hi folks and thanks to all for the input, the video was really reassuring as the LED activity matched what I'm seeing. It also might tie in with the service guide description of what's going on in firmware during the power-up sequence where "one of the first things to happen is the Main and Graticule intensity levels are cleared (two flashes?) then writes the value at the address (one more flash?)"
So reassured the processor was doing something at least I started thinking what else could stop the buttons lighting up?
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! I haven't traced the connections yet but either the processor is reading back that the lamps are good - unlikely that we have aerospace type BIT in this box? - or taking things apart and putting them back got the other button-lights going somehow? Very odd but set that aside (for now, but I know it's going to nag at me in the still dark watches of the night).
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!
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!
I'll keep you posted and thanks again,
Adrian
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On 7/2/2018 12:01 PM, cmjones01 wrote: I've just made a couple of short movies of my 7912AD waking from its slumber. The lights change as you describe and the 'reduce intensity' LED does flash in the pattern you mention.
|
Two more plugins. An early 3S6 and a reasonable S/N 3T6.
The issue with early S/Ns issues with external control.
Pictures have been added to the album
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Show quoted text
On Sun, Jul 1, 2018, 8:06 PM Pete Lancashire <xyzzypdx@...> wrote: Here's some photos of the 568 & 3T6 I got from a local Surplus Store.
They're pretty crappy photos the Sun is going down but somebody wanted to
see them.
I wish I still had my mod sheets of all the different S3100 mods and mods
to the 568 3T6/3S6 we did for the S3200 family.
I guess just more things to figure out.
Plug-in wise it's starting to look like getting a clean 3S6 might be an
issue.
On Sun, Jul 1, 2018, 1:51 PM Pete Lancashire <xyzzypdx@...> wrote:
It's going to be a big project I hope to be able to complete at least parts
of it so that whoever may take it on after me will not have a hard time
finishing it ?
Very few people know the history of ATE Tektronix was decades ahead of
everybody else. And also made a bundle of money in the process.
Unfortunately almost everybody involved got no recognition.
On Sun, Jul 1, 2018, 11:09 AM Miguel Work <harrimansat@...> wrote:
Amazing, please photos!!!
-----Mensaje original-----
De: [email protected] [mailto:[email protected]] En nombre de Pete
Lancashire
Enviado el: domingo, 1 de julio de 2018 18:00
Para: [email protected]
Asunto: [TekScopes] s3100 restoration
I acquired a very clean 568 & 3T6 yesterday. Pictures by end of day.
Registered S3100.org
Put offers on 2 x sampling head extenders and were accepted.
Need / looking for
- Plugin paddle boards, or one I can use to get boars made
- Board extenders for the inside boards in the 3T6
- P/N for the interconnect cables and cables
- A-3A heads and accessories.
- R241 & cards, etc.
- S3110 rack. there must be on in the Beaverton/Portland area, Even the
name plate would be nice.
- Test drawer, dut holder etc
- Integration manual (interconnect) not needed but would be nice to
have, does give p/n's for all cables.
Next week will be picking up at least one mouse poop covered R230 and
at
least two R568s for parts.
|
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).
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Show quoted text
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
|
Re: What are these Tek parts for?
OK. It appears you are correct about the left part. I now realize that my
OS-245 (milspec 7603) .... But the other part pictured does not match up to anything I can tell. Could it be the front of a chart recorder like these? Tom Bryan
|
Re: What are these Tek parts for?
OK. It appears you are correct about the left part. I now realize that my OS-245 (milspec 7603) is missing the receiving side of the clips to which the cover attaches. I've added photos to the aforementioned online image album <>. So, I'd like to find those clips if someone know where I can get them. Either that, or I'll have to fabricate them. I bump into these sorts of clips all the time (trying to think if there something around the house I can harvest them from). But the other part pictured does not match up to anything I can tell. On Mon, Jul 2, 2018 at 6:43 AM, Colin Herbert via Groups.Io < colingherbert@...> wrote: One of those looks like the front cover for a series-7000 scope (option
#8). It even still has the foam bits for holding probe parts. I've no idea
what the other thing is, but could it be some kind of implosion screen?
Colin.
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of David
Berlind
Sent: 02 July 2018 02:14
To: [email protected]
Subject: [TekScopes] What are these Tek parts for?
Two parts... some sort of cover.. but I don't think it's for anything I
own. Smells like an old Tek scope too! If I have no need for this and
someone else does, I'd be happy to stick it in a box if you cover postage.
|
Re: 7912AD Fails start-up self-test (perhaps)
On Sun, Jul 1, 2018 at 02:46 pm, Adrian wrote: So as of a few hours ago I became the proud owner of a 7912AD with a matched
pair of 624 & 634 monitors. Congratulations and welcome to the club. I believe I should see the 'Remote' and 'Digital' lights come on for two
seconds followed by the 'TV' and 'Local' lights coming on but all I see is two
brief flashes of the 'Reduce Intensity' LED, a short pause, a third flash then
nothing.
My question is: Does the self-test actually flash that LED (it is not
mentioned in the manual as far as I can see) or does the fact that it comes on
at all mean that the system is sensing a high intensity somehow and aborting I've just made a couple of short movies of my 7912AD waking from its slumber. The lights change as you describe and the 'reduce intensity' LED does flash in the pattern you mention. First a view of the whole thing (sorry about the horrid little LCD monitor, but it's all that will fit on the bench): Then a closeup of the buttons and lights: In my experience failure to start up has most usually been caused by missing/incorrect power supply rails. There's a circuit which monitors most of them and holds the 6800 CPU in reset until they're right. Bringing a wire out from the 6800's reset pin and watching what happens to it might be interesting. If the self-test is failing for other reasons (RAM or ROM test error) then that gets shown on the TV's readout. The last time my 7912AD stopped working, it was because there was a poor contact on a harmonica connector on the PSU regulator board which fed -2V to the power distribution board. That was enough to stop play. Chris
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Re: 7912AD Fails start-up self-test (perhaps)
Adrian,
The 'reduce intensity' light can be triggered either by current in the write gun measured via the A1 electrode (diagram <7>, A40 board, signal is labelled 'Protect Enable' and drives 'reduce Intensity' via U114 on diagram <12>) or by the CPU via U830 on diagram <13>. In fixing my 7912AD I was fooled by the Reduce Intensity light making me think there was write current when in fact the 10kV anode voltage to the write gun had failed.
The symptoms you describe suggest that the 6800 MPU is not working properly and if the DC level of +5.1V is correct then check also for ripple. The installation of the many plugin boards into the backplanes makes for difficult testing at the board level without extenders (I have never seen any advertised). I would be tempted to solder in a few flying leads so that you can check CPU clock and busses (and reset) and work from there.
There is a handy trick to check if the read gun and video circuitry are OK - it can be found under the calibration section of the manual. Reverse the current through the focussing coil of the read gun and you should get a bright ring around the edge of the display. This is independent of anything written to the target.
Regards,
Roger
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Re: What are these Tek parts for?
One of those looks like the front cover for a series-7000 scope (option #8). It even still has the foam bits for holding probe parts. I've no idea what the other thing is, but could it be some kind of implosion screen?
Colin.
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-----Original Message----- From: [email protected] [mailto: [email protected]] On Behalf Of David Berlind Sent: 02 July 2018 02:14 To: [email protected]Subject: [TekScopes] What are these Tek parts for? Two parts... some sort of cover.. but I don't think it's for anything I own. Smells like an old Tek scope too! If I have no need for this and someone else does, I'd be happy to stick it in a box if you cover postage.
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Jeff Urban
zenith5106
Fabio Trevisan