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I was thinking more along the lines of the hood shown
on Mr. Carlson's 565 in this video:

That is probably the 016-0053-00 round hood for 5" round CRT scopes.

Does something similar exist for 7000 series mainframes?

There is a three sided folding one 016-0260-00, and a full light shield that you put your face against
016-0154-00

But you can look all this stuff up yourself by downloading the complete set of Tek catalogues.

Craig

No variac, I'm using normal line voltage (230 V).

Max

Not that specific component failures on mine will address your issue, but about 17 years ago I replaced these shorted components. (Not all in the same incident)
CR1534 killed beam
C581 - 22uF killed 9v subsystem
C2011 - 15uF killed everything as I remember.

There are myriad little isolated power subsystems in this scope and they all have to work. I would check every single CAP node impedance on pages 14, 15 & 17 with caps larger than 0.5uF as a starting point. Many are isolated with inductors, so DC and AC measurements are in order. If your inverter won’t start or continue after starting, it’s a high probability there is a shorted CAP or diode.

Good luck and keep us posted.
KJO

Yeah, that's the one shown in the old thread. I was thinking more along the lines of the hood shown on Mr. Carlson's 565 in this video:

Does something similar exist for 7000 series mainframes?

Sean

1038-N10 Switches

The switches on the N10 are a huge problem because the footprint and shaft do not match anything else.
I was able to buy one box of replacement switches from Gigatronics (they inherited the line from Wavetek)
several years ago, but I do not know if any spares still remain there.? only a contact to the service
department will reveal that. I do have a bunch of the black buttons left from the switches if any
use to anyone to try and make a replacement, and one switch to serve as a model.

I think the only fix is to make a tiny adaptor board to fit a more common tact switch to the wide 2 pin
format, and try and find a switch shaft that can mate to the X-cross-section inside the buttons. It's
possible that glue is the only answer to button attachment, which makes the whole process much
clumsier to carry out.

best regards,
walter

--
Walter Shawlee 2
Sphere Research Corp. 3394 Sunnyside Rd.
West Kelowna, BC, V1Z 2V4 CANADA
Phone: +1 (250-769-1834 -:-
+We're all in one boat, no matter how it looks to you. (WS2)
+All you need is love. (John Lennon)
+But, that doesn't mean other things don't come in handy. (WS2)
+Nature is trying very hard to make us succeed, but nature does not depend on us.
We are not the only experiment. (R. Buckminster Fuller)

Thanks for the several cautions and suggestions. I did look for shorted caps as I had several tantalums go previously - but I replaced them all a couple of years ago and it had been running fine. Didn't find any obvious problems. Also pulled all the permissible combs one by one and scoped all the rails - only the -5V showed a short and it was still present after I disconnected all the peripheral -5V connections (there aren't many IIRC). I ran out of time after finding the non-inverting input on U1624 was going haywire (spiking from ca +4v to -1.2V) at exactly the same time the -5V rail showed a short - this with U3 in/HV operating. Replacing U1624 made no difference. I have a screenshot of that trace but can't work out at present how to attach a photo to this reply. I think the next step will be to check rail resistances to ground - not sure now whether I did this step thoroughly as I followed the service manual. Though I did do extensive component checking after replacing U1624 without turning up any obvious answer. Thanks again for the advice. Will report back when I get to it again.

I've found theDennis' documents you mentioned on how to build a complete dummy supply load for the 7104/7854 SMPS.
I will buy the necessary resistors... :-/

BUT the document only mentions the connections to be made (using the dummy load) towards P82.
IMHO the connections to P83 that performs the voltage sensing should also be wired in an appropriate manner.
Otherwise the low voltage regulator (board A22, schematic 16) cannot work!

Hi Max,
I checked that P83 can be left disconnected, like in many previous versions of power supplies. At the LV board there are resistors R76, R96 and R132 for this between the sense lines and the voltage output lines.

Are you using a variac? I have seen strange things when I cranked up the variac untile the spms starts. Later on I applied normal line voltage immediately.

Albert

Had similar problems years ago and the problem was those little tants going short. Rather hazy on the details now, but I remember how infuriating those power supply interlocking systems were. With supplies disconnected and unplugged and unpowered, be sure there are no shorts or low resistance paths to ground from all of the rails. (Beating the obvious though).
I vaguely remember once replacing a TO92 bjt somewhere causing power supply problems. I’ll dig out my service manual to see if I made a note.

I don’t know how Tek did service, but even with the manual, I don’t recall a means to bypass supply sequencing.

KJO

I have one of these. I got it off eBay and it seems no-one else was interested, as I got it for the
starting
price of 99 pence (UK). They seem to be very rare items and bears a part-number 016-0154-00. I have
not been able to trace this part-number.... I should probably say that I am in London, UK.

Colin.

Listed in the 1970 catalogue (and probably others). USD 7.00

Apparently not only fits the 7000 series but also the 601, 602 and 528

Craig

Hi Lorenzo,
don't disable the protection, it could damage your supply. Maybe you should disconnect the -5V regulator from its load and use a lab power-supply to provide the -5V to the loaad. Set the current limit on your supply to 1 - 2A. Something will get hot...

--
Best regards,

Fred S.

If you really have a short circuit from -5V to ground (eg a failed tantalum capacitor) you don't need to power up the scope, it should be obvious with a resistance measurement. Schematic <17> shows the power distribution between boards and you can isolate boards by pulling the multi-way 'combs' that are used for interconnection.

To be sure that your diagnosis of a -5V fault is correct, and assuming that you have another double beam scope available you can look at the low voltage power rails in pairs as the power comes on and check that each is heading for its intended value before the protection cuts in.

Roger

I have one of these. I got it off eBay and it seems no-one else was interested, as I got it for the starting price of 99 pence (UK). They seem to be very rare items and bears a part-number 016-0154-00. I have not been able to trace this part-number.... I should probably say that I am in London, UK.

Colin.

Hi Albert,

You're probably right, I didn't analyze the feedback/offset circuit in fine
detail. My conclusion about the offset was mostly based on what I observed
while probing around the head.
My 7S12 suffered from poor contacts issue (mostly due to IC sockets), there
is always a possibility that something like that interfered during tests.
Anyway, I will try the equivalent test on my S-4 (remove Q55) that you
carried out on your S-2. It would be worthwhile to reach a proper
conclusion on this circuitry. However I will be able to try this only after
the 1st of May holiday, will report back.

Best Regards, Nenad

I have posted in eevblog also thanks a lot for the inputs

Hi Ed,

Did you try switching off digital storage? If there is a fault in it (and
it's quite a complex circuit), it would interrupt the signal path. My unit
was such a case (was working only with DS off).
When you switch DS off, internal MUXes route the detector output directly
to the vertical amplifier (buffer). This path is much easier to diagnose,
I'd try that first. Also check the Video Out plug on the front panel.

Best Regards, Nenad

I found this old thread (/g/TekScopes/message/152935?p=,,,20,0,0,0::Created,,crt+hood+,20,2,0,28557610) that showed the "batman" style viewing hood. While I can see the utility of this hood for looking at fast pulses on non mcp crts, did they ever make just a simple shade for the 7000 series that fits over the crt bezel to just keep room lights off? I've seen these (round) on 5xx series 'scopes. Can't seem to find a mention of such a thing in manuals.

Thanks,

Sean

Hello,

I have a 1038-D14 and 1038-N10 combination, with 3 matching powersensors.

Also have the operating and service manual for the D14A and N10 (already scanned), please indicate how to transfer these files to you.

The major problem I have is the bad pushbutton switches on the N10, which prevent me from operating the units. I already unsoldered the switches, but I am still not able to control the N10 / D14 combination from the GPIB interface. Seems I would have to use the switches to put the N10 to remote contol mode.

Any help on these problems is welcome.

Regards, 73,

Hans, pa2hbn

Whilst looking through my test equipment inventory a bit of trivia came to mind regarding a unit that I had acquired back in the late 90s off of surplus. It is still tucked away in storage and I had almost forgotten about it over the years.

The unit is a Dumont/Fairchild 766 oscilloscope with a 76-02 dual-trace and 74-03 time base plug-in. What was interesting that I found when I first opened it after receiving it was that the large panel immediately behind the CRT (a sub panel ahead of the actual rear panel that contains the power transformer, power transistors, capacitors and such that are mounted on the panel) was sprayed with a thick coating of either black paint or some other heavy substance that coves the entire panel including all of the components mounted to it. Aside from the paint job what I did find rather unique about this particular instrument was that it contains no pots for horizontal or vertical positioning of the trace but, instead, has a joystick on the panel for positioning.

From the way the paint is applied it is obvious that it was a factory job being professionally applied prior to assembly of the scope. The edges of the panel are masked and there would be no way to spray the coating on the panel from the way it is installed in the instrument.

I later learned that this scope was manufactured in the 1960s around the time Tektronix had filed a lawsuit against Dumont for a direct copy of the circuitry in one of their products. I never did find any evidence as to the outcome of the suit. I am wondering if this model oscilloscope was the victim of the Tek-Dumont/Fairchild battle and that a quick cover-up was made to circumvent any further penalties for the company in their product in a last-minute move. I can see no other reason to apply a heavy coating of paint or whatever to the innards of the scope.

Tonight I did a little Googling and found that Fairchild/Dumont later came out with the model 766H “Signal Analyzer” - no longer titled “oscilloscope” which was still the very same oscilloscope with the same plug-ins that this unit in my possession has. This also raises a question as to why they did such a thing to the very same instrument.

Greg

O.K Albert,
. I've found theDennis' documents you mentioned on how to build a complete dummy supply load for the 7104/7854 SMPS.
I will buy the necessary resistors... :-/

BUT the document only mentions the connections to be made (using the dummy load) towards P82.
IMHO the connections to P83 that performs the voltage sensing should also be wired in an appropriate manner.
Otherwise the low voltage regulator (board A22, schematic 16) cannot work!

Thanks G?ran for your suggestion regarding diode checking.
I only checked them using my analog VOM Supertester ICE 680R in ohmic mode and no defects was revealed.
I will try to measure them using the oscilloscope and differential probe.

Max Mazza (from near Venice, Italy)

My Tek485 has been sidelined for some months with a power supply issue - the inverter keeps cycling on/off. I've fixed similar issues a few times but this one has me foxed. Balance node shows a short on the -5V line (present intermittently in the past, now permanent) that I strongly suspect is caused by something in the cathode regulator circuit. Lots of component checking on the LV and HV regulation circuitry failed to turn up any obvious problem. Removing pin U3 hasn't helped so seems it's an LV problem. Other supplies come up normally. However, I've found it quite difficult working with the transient signals I get with just 30ms of start-up before the balance node circuit recycles - all the action happens in the first 10ms or so after startup. Wondering if there is any way of disabling/bypassing any part of the protection circuitry to allow easier tracking of what's shorting the -5V supply without risking damage to other parts. I suspect the answer is no but thought I'd seek some expert advice in case I'm doing this the hard way and there's a work-around. Haven't managed to find anything online.