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On my 1S1’s heater regulator board, the pass transistor was mounted with the emitter pin touching the heat sink, which shorted collector and emitter and ran the tubes hot.

Dave Wise

OK, not in a movie or advert, but in a Web page on medical ultrasound history. I do ultrasound as my radiology specialty. The early machines I used were "articulated arm" ones. These used an arm with a single crystal transducer on the end. Position sensors (usually simple potentiometers, sometimes shaft angle encoders or differential transformers) in the "joints" of the arm would pick off the transducer position and the operator would "build up" an image in the process of moving the transducer across the patient. Current machines use multielement transducers and borrow beamforming technology from radar folks to reconstruct a 2D image (now 3D and even 4D) in real-time. Anyway, while researching the famous radiologist Dr. Barry Goldberg, I found a Web page that shows two early instruments:



The small image on upper right clearly shows a Tek scope on a cart. It looks to be a 500-series, but the image resolution is too poor to make out much more. The image in the lower center shows a very early (likely prototype) articulated arm scanner. My question is what is that scope? It clearly uses plug-ins and the CRT is rectangular (or has a rectangular mask). The plug-ins are likely custom as is the panel on the scope cart (which looks like a Tek cart). The Fairchild-DuMont scopes had a round CRT, but did take plug-ins. Any ideas? There is a name plate on the scope front, but I cannot read it in the image on the page.

The early machines I used (made by a company called Unirad) looked like these:



The top most large CRT is simply a video monitor. Below it is a flat-face CRT monitor with a camera on it to record the images. In the models we had, that was a Tek monitor. Below that, the next CRT was, I think, a Tek scope or monitor with a fixed sweep rate but two channels. One channel showed you the signal from the transducer - the "A-mode" (amplitude mode) signal and along with it, the second channel showed the curve of the time (depth) gain compensation you had set. I might be wrong about that fixed sweep rate - it may have changed as the depth was changed so the whole time gain compensation and A-mode traces could be displayed. It has been over 40 years since I used one of those machines (thankfully - but if you learned how to use one of those, you got to be really good at generating images - it paid off when newer machines came along). Image storage? A scan converter tube (I think they were made by Hughes).

All our machines now use flat LCD panel displays. Imaging is all digital after the transducer elements so digital images come out of the machine to the LAN (medical imaging uses an image format called DICOM). No more cameras mounted on the machine. Many of them do have small thermal printers so we can print an image of a fetal profile for the parents of the fetus we are scanning. We use a networked color dye sub printer instead. Patients love our images - they are 8 x 10-inch glossy prints and if we can do a 3D image of the fetal face, it is very much appreciated. Yes, we have taken images of the fetal genitals for "reveal parties" though it is not our favorite thing to do (and no, we don't charge for these printed images).

I can't believe nobody makes motors of the right size nowadays? It's
not a magical diode motor is it?

On the calibrator ground thread, someone mentioned finding a miswired ground resistor, original from the factory. I thought it would be interesting to let people list the Tektronix factory assembly errors they have found. I'll start this with my list of two.

I was running thru a collection of AM502s that had various problems. Most of what I was doing was replacing burned out incandescent lamps with LEDs and replacing the dropping resistor. To get reliable service, i also had to Deoxit the front panel switches. While going over one unit I noticed a ground connection had not been soldered. The wire lead was there and the ground lug was there, but there was no solder. IIRC, this was part of the input AC/GND/DC selection circuit. Easily fixed. BTW, I have parts from one AM502 that I couldn't save if anyone needs spares.

We picked up a surplus 475 or 485 that didn't work.at all. Opening it up, it looked clean, but there was clearly some problem with the power supply. When I looked over the board from the solder side, it looked perfect. The top side looked perfect, too, but a small glint of silver sticking out from under a cap caught my eye. This was a radial lead electrolytic, plugged into the board and soldered on the other side. I figured there was a scrap piece of wire caught under it and tried to pull it out, but it wouldn't budge, so I unsoldered the cap from the board. I discovered that this cap had long leads that had been pushed into the holes in the PC board, but one of the leads had caught on the board and didn't pass thru. Instead, most of it, a couple inches, curled up under the cap. It must have been okay for a few years, but eventually wore thru something and shorted, probably to the capacitor case. After straightening the leads and reinstalling the cap, the scope worked just fine.

On ebay, miss-listed as a manual for a 067-0554-00, this is actually a manual for a 067-0544-00, a calibration plugin for the 647A.

www.ebay.com/i/133659054167

I don't know how useful or common this is, but the price is right: $12.50 w/free shipping.

I'm not presently where I can look at it, but I opened my TM504 a couple of weeks ago while evaluating electrolytics and pass-transistors in my TM for ordering replacements. Fortunately those in the TM504 were OK. I, too, was surprised to see two of the pass-transistors mounted on a rear member. These may have been those for the high-power slot, but I do not remember. It sounds like yours are in the same locations.

Bruce, KG6OJI

Christian,

Dan is most likely right.about relocating transistors that are too hot where they were originally. I have not looked at the schematic or have this device. It makes sense to do this modification when needed. I did a modification of moving the two series pass transistors in my Pioneer SA-9800 to the frame where two holes are to reduce the heat problem of these two transistors.That greatly(!) reduced the temperature of the transistors. I did make sure to use an insulator and good quality compound on each side of the insulator because the collectors are not grounded. This is a known problem in this amp even after fully restoring. I know this Pioneer model is not a scope. The principle is the same no matter what device it is, reduce too much heat by relocating or adding more heatsinking. If your TM504 is working as it should, leave the modification alone. Adding compound to aid in the heat transfer is your decision. The S/N of models would likely be the reason for your transistors being mounted differently than other S/Ns.

Mark

Hi Christian,

This arrangement should be factory-standard. My TM504 is configured the same way,
and Fig. 2 Exploded Parts Diagram (rev B from 1974) shows item 34 (identified as
Q22 and Q30) as being attached to the chassis near the transformer.

I imagine that Tektronix discovered that the bracket used to heat-sink the remaining
four transistors and the two diodes could not quite dissipate enough heat if all six
transistors were attached there at full power.

Is your unit an early serial number? My bracket (item 78) has no provision for mounting
Q22 and Q30 at all.


dan

What is the part number of the fan motor? I have a Siemens fan motor from a Tek 7104, so it may be larger than the one from the 2465. It is about 2.6 cm diameter by 5.6 cm in length. It is soldered to a circuit board about 5 x 5.5 cm. I do not now whether or not this motor is working. I received a 7104 damaged in shipment - the fan assembly was smashed in. Despite this, the scope powered up (I turned the power on very briefly - long enough to see a trace and move it with H & V positioning. I did not want to leave it on for further testing. I gave the scope away to a young fellow who is restoring Tek scopes, but I received the motor from the seller and put it away so I could not find it when I gave away the scope. I found it recently. It has the following part numbers on it:

1AD3001-0A
10-15V-0385 (maybe operating voltage and current, but there is a scratch on the case - if there was an “A” on there, it is obliterated by the scratch).
73040000/03

The motor has a slight axial play in the shaft. The shaft is plain (no gear or flat) projects from the motor face (which is made of a clear plastic) by about 12 mm.

If this is the motor you need, you are welcome to it for the postage to ship it. If not the motor you need, if any other member of this group is welcome to it for postage as well.

Any thoughts on Triflow?

Dave,
Maybe this last picture will answer some of your questions:
? /g/TekScopes/photo/262670/3204540?p=Created,,,50,2,0,0??

Good day,

While working on a troublesome plugin, I had cause to open up my TM504 to check the power transistors (as one does). I am surprised to find that Q22 and Q30 (an NPN from one middle slot, a PNP from another) have been cleanly relocated from the PCB to a location about 6" away, and heat sunk to a chassis member there. Fancy color-striped wire was used, and heat shrink etc: it looks like a pro job. Anybody know what's going on here?

And you're going to ask me if they are the OEM PNs; that will require more disassembly.

Interleaved.

On Fri, Apr 9, 2021 at 04:06 AM, Dave Peterson wrote:

Stephen seems to be in possession of of a true early scope. Stephen, is the A5
board a discrete component or IC version?

If by IC version you mean U440, it’s there.

Does it have a surviving time/div
know without "LOCK KNOBS"?

How do you mean? I don’t see any differences between this scope and my other 465, or my 475A, or my 465B as far as the Time/Div knob(s).

And a simple "A" HORIZ DISPLAY button?

Same as above.

What other notable differences are there on the early pre SN B250K scopes?

The only noticeable difference that I see is that the CRT bezel isn’t held by checkered and captive screws like the others, but with regular non-captive philips screws.


Feel free to ask more questions if you need to.

Dave

On Fri, Apr 9, 2021 at 05:18 PM, Jim Adney wrote:

Unless someone else beats me to it, I think I'll start a thread on discovered
factory assembly errors.

How about a freebie: I once bought a rackmount 7844 (400 MHz double beam) mainframe in unused condition, apart from a few light scratches from the sliding action. Seller didn't know much about its history.
While trying it out, I found the screen info collapsed and the scope produced a loud tick when I touched the horizontal separation knob, at the far top right of the front.
Turned out that the knob controls a pot, soldered into a PCB which is mounted at a distance on a horizontal aluminum chassis plate.
Someone forgot to cut the protruding legs of the pots during manufacture. The endpoints of the pot are connected straight to the 15V supplies....

Raymond

On Fri, Apr 9, 2021 at 05:22 PM, Robert Simpson wrote:

Strange ad. He says 2x 465B, but the picture shows 2x 475 plus something I
don't recognize. Located about 45 min from me..

Difficult to see what's behind the dirt. Even for a 475, $100 would be a lot, especially in the state it could be in. $80 for each wouldn't be a bargain either. The trolley is ok.
There seem to be 2 475's (see the different dots above the CH1 V/div knob and the red label on the crt bezel of one), one 465B and an HP spectrum analyzer that at least partly seems to work. Get the set, including the SA at $250 or $100 more if must be...

Raymond

That's an HP Spectrum Analyzer. I wish I was where I could get that one. Oh well...

Thanks,
Barry - N4BUQ

On Fri, Apr 9, 2021 at 05:06 PM, Dave Peterson wrote:

I'm curious to know how "rare" these early scopes are any more. Tek seems to
have made these early changes fairly quickly, even before the actual SN B250K.
I currently posses a B177K and it seems to mostly be made up of later
components. The A9 is late, and the A5 (vertical amp) seems to be somewhat
later: non-IC discrete components matching the change schematic, but the post
B250K four digit component numbers. It includes components on the earlier
change schematic that aren't present on the later board.

Interesting, Dave. I think you already know more about the 465's history than I, with my more general knowledge.
Please keep us informed.

Raymond

Strange ad. He says 2x 465B, but the picture shows 2x 475 plus something I don't recognize. Located about 45 min from me.. No connection.
Bob

Interleaved


On Fri, Apr 9, 2021 at 04:39 PM, Stephen wrote:

I just think that the fact that it’s serial number 465, which is the same as
the model number, is kinda neat. Other than that, nothing special. It’s just
a serial number... ??♂?

Oh yes, I completely forgot that. Of course it's very special!

I’ll use the Variac when it’ll actually get here. In transit at the
moment. ?
It’s not a very big one, just 5A.

Absolutely big enough for all Tek 'scope work!

Meanwhile, I’m going to power the scope with a 12VAC. That’s all I have
available at this point, along with a 24VAC one, until the Variac gets here.

That is fine, start with 12VAC.

Raymond

On Wed, Apr 7, 2021 at 04:40 AM, cmjones01 wrote:

It turned out that there was actually a manufacturing error. There's
an arrangement of plastic bushes and fibre washers to keep the
calibrator socket's outer from being in contact with the front panel.
In my 127, one of the fibre washers was in the wrong place, so the
bottom of the volts/millivolts divider chain was connected to chassis
ground, and both ends of the 0.25R resistor R898 were also connected
to chassis ground.

Nice catch! ;-)

As fans and long time users of Tek products, I suspect we all tend to assume that all Tek products leave the factory in perfect condition. I certainly used to, but in the past 20 years, I've come across 2 factory assembly errors that surprised me. I was able to fix both, but they came as a shock at the time. Unless someone else beats me to it, I think I'll start a thread on discovered factory assembly errors.