Re: Horizontal Display switch shenanigans.

Dave Peterson

So here I am at the bench again getting ready to reassemble the CH1 attenuator input Rs & Cs. I'm going to clean up the connections to the A3 board and would like to remove the Vertical Mode pushbuttons/pushrods to protect them from being damaged by an errant soldering iron.

I don't like my method of pulling these things off. I'm pulling away longitudinally on the pushrod while twisting a screw driver between the pushrod connection to the switch - to open the end enough to release.

The screwdriver keeps marring the pushrod, and any direct lateral prying at the pushrod end puts a lot of force on the switch pushbutton. And as noted earlier, these buttons are pretty fragile as it is.

How do you guys remove these? Is the above pretty much it, and such "damage from repair" part of the process?


Re: Tektronix 7D13 and 7A42 wanted

Dan G

On Sat, Nov 28, 2020 at 11:08 AM, Dave Daniel wrote:

I see the usual exploded parts diagram in the manual, but I don't see
instructions anywhere for removing the PWBs. It looks as if one has to
completely remove the rear panel (-124 in the exploded view) in order to
pull the A8 board out. Is this the case, or am I missing something? Any
pointers would be appreciated.
Hi Dave,

The lower right frame panel (item 104 in the exploded parts diagram) should
have a cutout that permits access to the battery terminals from the PCB solder-side.
Most soldering iron tips that are suitable for use on Tektronix PCBs should be small
enough to fit comfortably through this opening. Given that the opening is centered
right over the battery terminals, I suspect that it was made specifically for the purpose
of enabling battery replacement without the need to disassemble the unit.
(It also makes it possible to quickly check the battery voltage.)

If your unit has this cutout, then all you need to do is remove the right
perforated panel, disconnect the two wire assemblies that run over
the battery, and gently pull out one end of the elastic retaining strap
that holds down the battery. No PCB removal should be needed at all.


Re: (OT) Where to go for 70s IBM hardware? I'm looking for a terminal.


Hi Steve,

thanks for the interesting links.

On Glenns museaum I found one that seems to have exactly the same package dimensions:

I'll have a closer look at the other modules and what is written on their lables. My unit has a datecode 1998 (second pic)... Even then there have still been aircraft around with old equipment that could not be changed. It think it was produced in Gemany, but for a french company. My mind goes to Concorde...

Another interesting source I came across is <>


Re: Fair Radio Sales Lima Ohio

Greg Muir

I’ll try to make this a brief note but it probably won’t happen.

Having spent nearly 35 years of my profession in Colorado I managed to visit many surplus stores around the area. It was a treat to see anything from more recent (I’m talking 60’s) back through WWII equipment. But, alas, one by one these stores slowly disappeared.

Then there were the stores that collected legacy & excess parts & supplies from other local business who deemed the stock no longer necessary. Of note was one superb store in Boulder that had an impressive inventory of all kinds of parts from the local HP factories in Colorado Springs, Loveland, Fort Collins and other areas. In addition they had a equipment consignment area where they would take in test & miscellaneous equipment for sale. The prices were right. A virtual gold mine to visit. But the demise of this resource ended in the sale to a new owner a few years ago, their not being able to pay the rent and the landlord moving everything out into dumpsters.

I learned of “surplus” at a very early age (and I will not allude to what the term “early” is for fear of reminding myself about how old I really am). But it was in a different form. The local air force base in my home town never really dealt with selling off excess property to any extent but, rather, simply sent it over to the local scrap iron yard.

During the summer months I would ride my bike over to the iron yard to see what goodies had been dumped by the base. They were always generous with their offerings to include things like complete radar systems (yes, transmitting equipment, antennas, scopes – the works), actual aircraft trainers (still have boxes of nice P&B relays and instruments pulled from them), test equipment (including HP, Tek, others) and a myriad of other items in very good condition. One day I even encountered a battle tank from the local army reserve complete with twin Cadillac engines. It became parted out rather quickly by the scrap iron yard.

All items that came through the yard from the AF base were tagged as to the repairability status. Most carried a yellow tag (no problems, just excessed) and the few red tagged items (repairs required) were found to have simple fixes (bad line cords, etc.).

The old man who ran the yard was wise enough to store much of the test equipment in an old Quonset hut located on the property behind a locked door. But he was always welcome to open it up for me since he knew that my browsing would result in a sale. He really ran a hard deal when purchasing items. But since I went to school with his son he would offer a generous “discount.” Base price for anything was $0.10 a pound (yes, 10 cents) but when presented with an item containing any copper (transformers, etc.) the price went up to $0.15 a pound (yes, again – 15 cents).

My home basement was always filled to capacity thanks to a generous weekly allowance of a few dollars. But I had to put up with the nagging from my parents whenever I called them from the scrap iron yard to come over with the car to haul everything home. Not all 10 through 14 year olds in the neighborhood had nice test equipment in their basements in those days.

My last foray to the yard was when I had already been living in Colorado but went home for my summer vacation. On a whim I decided to stop over to the yard to see what they had. To my surprise I found plenty. This was the time when the USAF SAGE system (,
( was being decommissioned and the Air Direction Centers (of which the local AF base had one) were being torn out.

As I approached the yard I couldn’t believe my eyes. There in front of me were the two massive AN/FSQ-7 vacuum tube computers with many of their 50,000+ vacuum tubes either missing or broken (, the radar transmitter equipment, the radar scopes – everything sitting out in the weather. One area of the property contained hundreds of 55 gallon drums containing long lengths of white and orange pipe sticking out of them which turned out to be the remnants of the massive radar antenna (
So it turned out to be a multi-day visit to obtain a few memorabilia from that system. Somewhere in my stuff I still have boxes of the nice Westinghouse panel meters removed from the radar transmitter cabinets).

I miss those days. Now everything is put onto the markets no matter if it is worth anything or not to be purchased at high prices through the bidding process or cutthroat sellers trying to exact every penny from items they don’t even have any idea as to what they are. Aside from that we have to be thankful for hamfests and such where buyers and sellers still can come to reasonable agreements about cost (but the prices still often exceed my past $0.10/pound experience but I have to be very understanding).


Re: Horizontal Display switch shenanigans.

Dave Peterson

This is why I think things 3 and more times over before I proceed. And still I sometimes miss the obvious. Some people call me smart, but I know how often I miss such obviously simple solutions. KISS. Duh.

Yes, I've got you now Raymond: replace the broken pushbutton, not the whole damn switch assembly. No soldering required.

Gads, I get annoyed with myself when I get so block-headed.

Re: Horizontal Display switch shenanigans.

+1 925-334-8641

1 mm sounds close. I thought as much. As for removing it, the best is to use a de-soldering gun since it is a double sided board. Solder wick might work but it will depend on the size of the hole vs. the pin diameter. Can't risk the damage to the plate-through.

Re: Horizontal Display switch shenanigans.


On Sat, Nov 28, 2020 at 06:15 PM, Dave Peterson wrote:

Do you just pull the lead out of the switch with some pliers?
If that relates to my earlier message, I don't understand. If it doesn't and you thought about pulling a switch contact pin out of the body of the switch and out of the PCB: don't, AFAIK, it's an insert-once construction. I'd be interested to know whether it actually is though...
I suggested moving the bar or clip holding the movable stem out of the way, after which the plastic stem (the part that is broken in your assembly) may come out easily. I've done that several times, not sure about this particular model.


Re: Tektronix scope issues


On Sat, Nov 28, 2020 at 07:07 AM, Thomas Dodge wrote:

I also have a Tektronix 7704 which I just powered on. I got it from a friend,
and when it is on, it just shows a beam that is very bright, so I turn it off
so it doesn't burn the CRT. The switches for the Time Base and the Volts per
Division have no effect.
Often, an uncontrollable, very bright CRT image indicates a problem in the DC restorer circuits.
If combined with absence of vertical and horizontal deflection, it most often indicates a problem in the (low-voltage) power supply (LVPS), which may also affect Z-axis behavior, causing a high intensity beam.
Fault finding may not be too difficult but you must protect the CRT - and yourself. Since I have no idea what level of experience yo have, I have to warn you WRT the dangers involved in working on these instruments. No intention to insult you...
With deflection absent, you can't move the beam off-screen to protect the CRT, so at least turn focus to either completely CW or completely CCW. That's probably not enough to protect the CRT (burning), neither will be removing the post-deflection acceleration (PDA) voltage (red wire to front of CRT).
Be very careful with the high voltages present and don't forget that the PDA voltage may take hours (or more) to bleed away - and that the 6.3 Vac filament supply is floating at about - 3 kVdc...
Once you've excluded the LVPS as the cause of your problem (a good chance the problem lies there), it would be very informative to see if there's a negative voltage between cathode and grid of the CRT: The CRT's grid should be at least 50 volts or so negative (averaged DC) with regard to the cathode with intensity turned down all the way. If the voltage is very low, intensity will be max. Measure using a battery-supplied high-impedance (>= 1 MOhm) voltmeter, well-insulated, and placed at least 5 cm away from any conductive areas. Connect first, then power on!

But first you need to protect the CRT's screen from being burnt. To achieve that, you have several options but you need to know what you're doing. Examples in decreasing order of my preference are:
- Temporarily disconnecting the filament supply (6.3 Vac).
- Temporarily removing the CRT. A bit dangerous, not as difficult as it may seem but not attractive until experienced...
- Temporarily stopping the inverter producing filament- and high voltage. This would take away the possibility to (among other things) measure grid-cathode voltage though and therefore in my opinion be the least attractive option.


Re: Horizontal Display switch shenanigans.

Dave Peterson

It was late, my brain wasn't firing on all cylinders. 2mm? Really Dave? They seemed thicker than 1mm, but I just went and measured: 1mm. So there ya go, exactly 1mm.

How have you guys removed this assembly? Solder wick? Heat gun? The board seems a robust big component kind of thing that a heat gun would work on. No surface mount Rs & Cs to float off. I've never actually done a hot air dismount before, so any ideas/suggestions are appreciated.


Re: Horizontal Display switch shenanigans.


I have actually completely disassembled and swapped bits and pieces of switches ( and other mechanical items) when unable to find what I want. the only time I could not effect a repair is when the assembly is molded . and at that although there are times that is even possible depending on how inventive and how much time ya wants to spend. you have very little to loose if it is already broke, take your time being careful is the motto....if it was mechanically assembled it can be re-worked. If man made it....

On 11/27/20 10:01 PM, Dave Peterson via wrote:
While pulling apart this 465 parts scope I tried removing the pushrods from the Horizontal Display switch on the A7 board. Working on the bottom "B DLY'D" pushrod the push button came out of the switch. I thought at first that it must be a simple mechanical assembly thing that I could put back together. When I had the chance to study it I realized that the plastic of the button had broken. I thought I must have done it trying to take the pushrod off, but then I noticed that the internal plastic button narrows to a very small "T" cross section. See the pictures in:

Notice the dirtiness of the cross section at the break. If the button was intact before I tried taking the pushrod off it must have been just by the top of the "T" and taken very little force to break it. I suspect it was already broken actually, and that having the board out of the scope allowed the pushrod to rotate down so that the button could come out of the switch assembly. When held horizontal the notches in the button catch on the ratchet mechanism of the switch, holding it in. When it rotated down it just came out with no force, nor did it make any noise. It just kind of fell out in my hand.

The back of the plastic internal button when complete has two channels that hold the metal spring contacts, which slide between the switch posts. I don't know if that's clear in the pictures or not. The point being, if this back piece with the contacts breaks off it ends up inevitably in the back of the switch. In the depressed position. I never turned this scope on - it wouldn't have worked with C1419 shorted anyway. I also didn't capture the back of the switch in any pictures nor notice if the button was visible from the back. They are when in the depressed position. So it's kind of lucky that I found this. If I'd tried the scope it would probably would be stuck in B DLY'D, or something worse with B DLY'D selected and whichever of the other buttons in the HORIZ DISPLAY group would be depressed. It's a pretty devious failure mode, and I have to wonder how common it is, given the fragility of that cross section.

Anyone else with experience with this kind of pushbutton failure?

But wait, there's more!

After finding this broken switch I looked it up by the Tektronix part number from the service manual I have - Fig 2 Circuit Boards, item 124: 260-1423-00, "SWITCH, pushbutton--HORIZ DISPLAY". I found a NOS listing from a company called "Talon Electronics LLC". I ordered it, but was surprised to find on my order after a day some notes from someone in the shipping department which read "cut pin", and submitted a refund for me. But then also shipped it anyway noting "might work in his application". Aw! How nice of them!

So the part came the other day. I unpacked it and compared to my A7/switch. Look at the last two pictures in the above album. Sure enough there's a "cut" pin, but note there's also a cut pin on the existing B DLY'D switch. But look closer: the new part has the wrong pin cut! The new switch in the picture is "on its back". It would be flipped over putting the cut pin at the front side of the board, not the back! Ahg! At least I got a refund. How the heck did this NOS part get in the system in the first place!? Bo-bo in the manufacturing process? Someone had too much to drink the night before and cut a whole batch of switches with the wrong leg cut?

So now what? I'm thinking what I'll do is cut the rearward pin of the new B DLY'd switch, and then cut the existing switch forward pin leaving it soldered into the board. Then when I mount the new switch I'll solder the new switch cut pin to the existing post from the old switch? Maybe place a piece of lead along the post and solder that?

Any other ideas or suggestions for this? I do see another one on eBay, but used. So no assurance that it's in good working order.

But what a convoluted situation! I wanted to share the failure of the switch. It seems like a hidden failure that someone might benefit from the experience. I'd also love to hear any ideas for "fixing" the new switch. Or should I just buy the used one on eBay?


Re: Horizontal Display switch shenanigans.

Dave Peterson

Thanks Raymond. I was wondering about that.

Do you just pull the lead out of the switch with some pliers? I imagine one needs to be careful about the switch position, or the switch contacts re-inserting? I figured I'd give this a try when I have the old one out. Not try it on the new on.

Parts are arriving, so busy on many fronts!

Re: Fair Radio Sales Lima Ohio


Surplus, of course, has been the best place to get stuff for repairs, ... but further, to leap ahead for invent.

University research labs on small budgets, high school students just getting started, and small companies all able to take advantage
of Obso, over-run, or cancelled project debris. No matter where, from Boston/MIT, Harvard; Eli Hefferon & sons, or the many in New Hampshire, and many more down the coast to Florida, due to the Cape; Dayton forever(lets hope), the many in the midwestern states and the huge surplus warehouses in silicon valley & up the coast to Boeing surplus sales, and beyond (Hello Walter !).

One could spend a lifetime wandering through them and most assured able to find treasures of yesteryear, "... ah ha, that's how they did it".
fortunes were spent on the design, engineering and construction of a part, let alone systems, materials and processes that wandered off to surplus floors, and then to the high temperature kilns or landfills of history. We do not even know what we have lost, and the old timers who knew that something of value still remained.

It is a hard day indeed when that source dries up...
While barely detailed in "The Hackers", least the surplus "concept" was mentioned.
There are details of technological history in the remnants that might never be comprehended.

Curiously, Surplus junk yards are often a short-stop in movies such as the various Star Trek's( even in Discovery, etc.), Star Wars, & so on...

May they ever be there for us & those that follow, for the future.

Re: Horizontal Display switch shenanigans.


On Sat, Nov 28, 2020 at 07:01 AM, Dave Peterson wrote:

Any other ideas or suggestions for this?
With these "radio button" sets, it's often possible to just replace one stem, without much disassembly nor removal of the set. You'd need to move the interlocking-bar and spring out of the way first though.


Re: Fair Radio Sales Lima Ohio

saipan59 (Pete)

On Fri, Nov 27, 2020 at 09:12 PM, ken chalfant wrote:

I live in Colorado Springs, Colorado. There has been a “surplus”
electronics store here for 34 years
Hi Ken,
I'm here in C.S. also, and shopped at OEM many times since the 80's. I worked at DEC, as did Dick's "employee/partner" Robert.
I'm curious what you plan to do with all the semiconductors you bought?


Re: Tektronix 7D13 and 7A42 wanted

Dave Daniel

I've just started to remove the battery from my 7A42.

I see the usual exploded parts diagram in the manual, but I don't see instructions anywhere for removing the PWBs. It looks as if one has to completely remove the rear panel (-124 in the exploded view) in order to pull the A8 board out. Is this the case, or am I missing something? Any pointers would be appreciated.



On 11/18/2020 11:58 PM, Dennis Tillman W7pF wrote:
Hi Ed and Dan,
I'll toss the battery and remove the jumper in mine also.

-----Original Message-----
From: [] On Behalf Of Ed Breya via
Sent: Wednesday, November 18, 2020 7:14 PM
Subject: Re: [TekScopes] Tektronix 7D13 and 7A42 wanted

Hi Dennis,

I didn't realize earlier your question "What did you use for a battery?" was to me. There is no battery. For something like this, it's simple enough to set up as needed, for occasional use. Having it remember is a nice convenience, but not worth the trouble and leakage risk. All I did was check it out after enough burn-in, and I removed the BE jumper as Dan suggested. It's running right now for one last time before mothballing.


This email has been checked for viruses by Avast antivirus software.

Re: (OT) Where to go for 70s IBM hardware? I'm looking for a terminal.


To me, they look like modules from an air data computer. Before the digital
ones, they had modules like this. There were modules that had a
bellows-type assembly for the airspeed (pitot tube) input as well as the
servos and resolvers to compute values for the cockpit gauges. Do an image
search for “F4 Air data computer”. The MOD could either be “modifications”
or “Ministry of Defense”. I suspect “modifications” as the tags often look
like the one on that module cover.

Better yet, go to Glenn’s Computer Museum ( and click on
the “Old Military” section (note: lots of photos - takes a while to open).

There’s an amazing amount of stuff in his museum besides computing stuff.

He’s another potential source for older IBM equipment. He might be open to
swapping stuff as well.

Steve H.

and look at the “Old Military

On Sat, Nov 28, 2020 at 04:26 Martin <> wrote:

Interesting... talking about electro-mechanical computer, I inherited some
modules I wonder if anybody can shed some light on them.

See the pictures (
Lots of resolvers and syncros inside. Looks very much aeronautic... maybe
something european, Tornado?


5 photos uploaded #photo-notice Notification <noreply@...>

Re: (OT) Where to go for 70s IBM hardware? I'm looking for a terminal.


Interesting... talking about electro-mechanical computer, I inherited some modules I wonder if anybody can shed some light on them.

See the pictures (
Lots of resolvers and syncros inside. Looks very much aeronautic... maybe something european, Tornado?


Re: Horizontal Display switch shenanigans.

Dave Peterson

I don't have it out of the board yet, but I could measure the new one. They're thick - like 2mm? I'd have to measure, and I'm shutting down for the day. Thanks for the offer. I'll look at it tomorrow.

Re: Horizontal Display switch shenanigans.

+1 925-334-8641

Now that you have it out of the board, what is the size of the pin? Like I said, I can send a couple of them in the mail.

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