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On Sun, Jan 5, 2025 at 05:23 PM, John Williams wrote:

If you don’t have one you need one!

I don't think I have one.
I don't think I need one.
Is this a "collector's passion" ... or am I missing something?

--
Roy Thistle

Over the years I have heard that the meter scales on certain HP gear were custom ruled as part of initial calibration, so specific to the individual instrument, but I have no idea of which ones are this way. I don't know if any Tek ones are, but I doubt it. If anyone gets to a point where they need to take a meter apart for repair, it's a good idea to take an accurate picture or flatbed scan of the face just in case, for future reference and use.

Ed

Hi Evan,

Thanks for replying. The CSA803A has a color display. I have put some pictures of the A8 video driver board in the photo album under:
/g/TekScopes/photo/299921/3873248?p=Created%2C%2C%2C20%2C2%2C0%2C0

I realized that my 11403A has the same A8 video driver board. Fortunately, I could make a picture of this diode without removing the board (Pic4 in the album). It is a glass diode with thick wires and a white ring at the kathode and partial identification "H-7".

Kind regards,
Gerard

James: "What is the dog house hole? Is it the slot in the middle of the PSU panel where the HV lead


The HV section has a metal cover (doghouse) with a 3/8" hole where HV U;tpr 21 kV connector exists from HV multiplier.

Adding insulation is useless.

Just be sure the cable and Alden connectrs are clean and ry.

Ozone: even0. 1 PPM is easily penetreating smell

No tube needed.

Jon

Hello Wofgang,

Thanks for the initiative. I would also be interested in two sets of boards. I have 2 7A13's that I would like to repair.

with best regards,

Patrick Vandenberghe
(Belgium)

Hi Barry,

sorry for the confusion regarding the 148-0063-00. I didn't know the part number and just googled the part. From the pictures I found I thought it was just as simple DPDT relay (like 148-0034-00) with an additional internal connection.
As it turns out, this is not the case. It might be possible to build an PCB adapter for this one as well. But as it is only used in the 7A12 and nowhere else it might not be feasible to go through this effort.

Bye,
Wolfgang

When I started working on mine, I found that bits of the meter scale were flaking off; so, I made an accurate photo of it. (I have a fairly good digital macrophotography setup). If the scale gets bad enough to need replacement, I'll edit out the bad parts of the photo
with gimp or photoshop (for Windows users), and print out a new high quality scale with a photo printer.

Would love to have one but it would make all my other Tek stuff look bad even though I've put a lot of effort into spiffing all of them up!

Tracy

Wow - I had spotted my scale is non-linear but had not appreciated that they were individual to the meter.

When you say 'meter' do you mean one scale for that particular range of meters as used in that piece of equipment, or do you mean individual to each meter and/or each piece of equipment?

I too need to re-do mine - the red has almost gone.

Thanks for that and filed away. Here's a link to one I did 30 years ago in Freehand on Mac a running OS 9.2.2, Did the arithmetic and just drew it, in about half a day:



Here's the front panel layout for a Quan-Tech Spot Noise meter



which I've been working on because the stock, linear-reading meters have about 10Db of range and the thing is an endlessly-range-switching pita to run.

In addition to making it log reading, I want to change the spot noise meter itself from a 10Hz-to-100KHz machine to a 3Hz-to-30KHz machine because I do tube audio and want to get a better look at 1/f as tubes tend to run to a 1/f-ish noise spectrum.

Bill in BC, Canada

There are several software programs for generating meter faces, paid or
free. Two are:

This link is now correct:

Googling for meter design software will find other approaches or
comments and comparisons.
John??? KK6IL

There are several software programs for generating meter faces, paid or free. Two are:


<>



Googling for meter design software will find other approaches or comments and comparisons.

John??? KK6IL

I have to redraw the scale for mine, it's faded beyond readability. If those scales weren't individual to the meter the redrawn scale might be of some use to others.

Not happening anytime soon though, still moving and setting up.

Bill in BC, Canada

Tektronix 106 Square Wave Generators for sale on eBay new surplus in Box. Preferred Air Parts have three of these left out of five. I just purchased one. If you don’t have one you need one! I will let you know my experience once it arrives. Sale has nothing to do with me.

Richard, many thanks glad I could help.

Ed, fine mod, I will do the same on my 130 LC. By the way are the meter scales hand calibrated?

Plan à similaire mod for à Tek 191 constant amplitude generator ( 50 kHz..100 Mhz).

Remarkable these 1960s units are still working, mine are in cal.

Jon

One of my 7904s just crapped out with HV arcing inside the PS unit - very loud and obvious. I had just fixed it (it had other problems not HV) back in November, and I'm convinced the failure was due to high humidity damp and cold conditions out in the garage.

If your new unit is quite filthy from what you've seen so far, the inside is probably pretty bad too. If it's working now but making discharge noises, you should open it up and clean the HV section (and the rest too as needed) thoroughly, then look for evidence of arcing or component damage. Chances are it should be good to go after cleaning.

I think that mine unfortunately ended up damaging something. I should have shut it down immediately but I thought it might clear by itself. No such luck. It still showed a messed up display at first, but then went blank - bad idea to let it go.

Ed

I agree - no line filter is needed. I'd say also that no extra trim plate is needed either unless the metalwork has been messed up. I changed my 130s to IEC recently by filing out the hole periphery with a 3/8" D or so round file just enough clear the chamfer and rounded corner features of the IEC connector. The original hole shows a bit, but I don't mind since it's on the back. Here's what it looks like:

/g/TekScopes/photo/296248/3803157?p=Created%2C%2C%2C20%2C2%2C0%2C0

Ed

James,

The neon, DB1219, should stay lit for a bit of time after turning the unit off. By going off fast, that sure sounds like your main filters are bad. In these in my 7000 series, I used Nichicon LGR 1200mfd 250V to restuff the cans. I also replaced the 150,000 ohm 1W with 100,000 ohm 5W, mounted off the board a bit to allow for more air flow around it, to bleed the B+ faster. With the new guts, the neon takes 30 seconds to stop flashing after turning it off. Check the B+ across the cans or across the 150,000 ohm 1W resistor. It should be 310V nominal. If about 280V or lower, the cans are going/are bad. In mine, I put in a CL60 or 70 off the mains to reduce the inrush current further. Being 50 years old, it would be best to recap the piece. Higher value electrolytics will work - especially on the 50V supplies (raise from 8,2/10mfd to several times the amount of capacitance and use 100V like Nichicon UHE). The originals are likely 60-70V. For the 17V supplies, use 35V. For the 15V lines, 25V. For the low value caps, 1, 2,2mfd for example, I used film types. I did raise the wattage of some resistors in the scopes.

I wonder if you still have the oily grime in areas that are a resistance path causing the crackling sound. The boards and other areas can be cleaned with ammonia or some detergent like Dawn, rinsed with warm water then left to dry for a while. A fan blowing on the pieces and/or over a heat register from a floor vent overnight. The dry heat that long will dry enough.

There could be a gap where the ultor lead goes in the glass at the front of the crt. If so, RTV works to seal that.

Mark

Hi Gerard,

Does the CSA803A have a color display or is it BW? Could you give a
refdes for the parts in question or link to a photo somewhere so I can
find their location?

PS: I would suggest the service manual but that thing is near useless.

-Evan

On Sun, Jan 5, 2025 at 9:19?AM gjm45janssen via groups.io
<g.j.m.janssen@...> wrote:

Dear all,

The screen of my CSA803A developed a problem. It showes flyback lines, low intensity and I could not get it calibrated properly. The size of the picture, focus and convergence are o.k..
After removing the CRT driver board A8 (671-1027-01), it turned out that a (zener?) diode is completely burned and also a 100uF/50V elco did not look healthy. This diode is immediately below the metal box shielding the flyback transformer and alongside what seems to be a very big tantalum elco.
Any help in finding the type of this diode is very much appreciated!

Kind regards, Gerard

The neon functioning is acting normal for operation of the PSU. The service manual calls it out as a "safe handling" indicator IE don’t handle the supply while it is still flashing. The supply has bleeder resisters for the larger caps so it sounds like they are functioning. That is what is helping with the quick drain off.

In my case I tested the caps out side of the supply with an SMU so I am 100% sure the fault is internal to the 980uF 200VDC though yours are not indicating like mine did one was reading higher then expected capacitance 1086uF with a climbing ESR 0.06 retest to 0.56

How do the spark gaps look? There are some glass tubes that looks like small fuses but are designed to arc over if they need to. If any are carboned up or dirty that will lower their arc over voltage.

If we are sure it is not the HV section then I would look for an arcing component. I have seen tants die that way when they cracked open some times you can even see the static. Or some for of contaminants.

If you have a fast enough meter are any of the power rails jumping around in time with the crackle?

If it is true arcing then an AM radio will be sensitive as a detector as well. Louder = closer

Absolute worst-case would-be breakdown in the transformer.

Zen

Hi all and thanks for the replies and help. I'm pretty sure it's in the PSU but I will reconnect it all (again), fire it up, and try the trick with the microphone in a plastic tube. Trouble is, I'm 90% certain it comes from inside the PSU and when I had the scope turned on in a darkened room I couldn't see any corona. My sense of smell isn't the best but I detected no ozone. But I will try again and report back.

I did quite thoroughly clean the HV lead and the connector originally, and cleaned the cap multiplier lead when I had the PSU apart. They were totally blackened with this oily grime, as were all the wiring looms. I imagined that this could lead to arcing and other unwanted stuff, so it seemed a good way to start. It's quite astonishing that the thing worked at all!

What is the dog house hole? Is it the slot in the middle of the PSU panel where the HV lead and other wiring comes out? Once I have that confirmed I might try getting another plastic tube and seeing if I can sniff ozone through that?

Re bumping the HV lead, yes, I have tried it. No change, sad to report.

Currently waiting on a supply of tantalums and other bits to replace those present on the other boards, also a tool for inserting the connectors into new molex connector plugs before the connectors totally fall apart (the blue ones are already partially absent, I'm concerned for shorts).