Tektronix 316 / 317
This Tektronix 316 was donated by Kenneth Kuhn (see Hewlett Packard Museum in the links). It was given to him around 2005, he specialises in HP equipment and seeing that I would give it a good home, sent it here! It is a 10MHz scope and is all that the Heathkit IO-14 is not, a true lab scope. The 316 was introduced (I think) in 1958, one year after I was born and with a pretty hot specification:
Sweep speeds are 2 S/div to 40 nS/div, with a trigger range of DC to 15 MHz.
The vertical range is DC to 10 MHz with a risetime of 35 nS. Sensitivity is 10 mv/div to 50 v/div.
It is very old and the inside was coated with a film of greasy grime, presumably because the air filter was removed years ago. I was able to return it to operation and calibration fairly quickly. It had the usual leaky HV caps and dead electrolytics plus a few exhausted valves. The most important thing with these scopes is to get all the supply voltages in tolerance first. Apart from dried out electrolytic capacitors, the other capacitors that will often need to be replaced are the ac bypass capacitors on the voltage feedback networks.
One thing that may cause some puzzlement; very often triggered scopes will sweep at the high speeds but not at the slow. This is usually due to a leaky hold-off cap, preventing the sweep gate from re-setting. Sometimes, the sweep will work at slow speeds but re-sets slowly resulting in very slow repetition at the slow speeds that is hard to view. In this case, the slow range would not run, in the case of the HP 150A, it simply re-set so slowly as to be unusable. In both cases, replacing the slow range hold-off cap cured the issue.
It has a nice side deflection contact CRT, the first 3″ CRT of this type I have encountered. This is presumably to get the 10MHz bandwidth and can be compared with the 310 which uses a 3WP1 and manages 4MHz. It displays very nicely. The acceleration is 1.85kv, surprisingly adequate for 10MHz; the 317 has the same performance specification with a superb 9kv PDA CRT to obtain good high speed brightness in high ambient light conditions (look further down this post to see it). It cost $800 vs $750 for the 316, at the time (1958) I imagine being $50 less was very attractive for many customers.
Being more enthusiastic than patient, I got it working in the grimy state, then washed it using my usual formula of undiluted Simple Green applied with a soft paint brush followed with distilled water to rinse it. This one would fit in my oven so it spend the night at 170°F.
As always with Tek scopes, restoring it to calibration is a matter of following the directions (whoda thunk it). Here it is. Note, I had the brightness turned up for the picture which does not do justice to the sharpness of the display.
While sorting out the triggering, I came across an aberration in the manual. The unit I have is serial number 568 while the manual I have used to be with serial number 1247. The trigger schematic specifies 6DJ8s while the scope is fitted with 6U8s. The aberration is that the schematic states 6DJ8s while the parts list specifies 6U8s. Here is the schematic with my corrections:
Here are the inside views. I have not yet developed a way of gutting and re-stuffing electrolytic capacitors that satisfies me hence the blue Mallory in the middle. The fan is not yet re-installed.
The Tektronix 317 was fitted with a superb 3″ PDA CRT, (part number 154-0346-00) shown below. As with the 316, the tube sports side deflection pins however it also has a helical PDA anode, the acceleration voltage is 9kv. This version of the 316 scope was intended for environments having high ambient light levels however, I imagine that if a unit was used regularly for examining the fast events it is capable of displaying, the 317 version would have been superior.
Here is a picture showing a top view of the 316 on top of the 317, you can see the high voltage supply transformer and rectifier for the PDA CRT, which is identical with that used in the 500 series scopes. Also visible is the PDA connector cap. This instrument arrived in excellent condition other than having received a hard knock to the corner of the display, enough to bend one of the #8 screws that hold the bezel in place. Fortunately, the tube is in perfect condition still. The only work necessary to get it working properly (other than the usual calibration) was to replace the high voltage oscillator tank capacitor, this is quite normal.
Here is the CRT side of both scopes, again the 316 is on top. The CRT control board for the 317 is located under the CRT. Note the difference in the length of the CRTs, that of the 317 being longer, presumably to maintain deflection sensitivity since both models have the same design and performance specification.
Below are both scopes displaying a 1MHz square wave from the fast rise output of a Tek 106 generator. The display of the 316 is extremely good, amongst the best I have seen. Having said this, the photography does not do justice to the 317, in actuality it is sharper than the 316 (quite a feat) and has much brightness in hand, truly an excellent display and yet, the 316 is so good that I cannot really see what would have justified choosing the 317 over the 316.
Here is another shot with a green filter fitted to the 317 the huge difference manifests photographically but not so much in actuality. The 317 is so sharp that I found using a magnifying glass actually revealed more of the delay line ripple detail! The intensity of the 316 is as high as it will go without defocusing, the 317 has a lot in hand. So, there is the difference. I really like these scopes, of all of them I think they are the best, for whatever that is worth.