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Tektronix 316 / 317

July 1, 2011

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.


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  1. Kirby Hallenbeck permalink

    Hi Richard,

    You have a very nice site. I found the simple green followed by baking with interest, as I have not thought of that one.

    I was given a 317 and got it working when I reconnect a loose deflection connector at the CRT. It was working fine for a while (except) time base was out of cal – about 20% ( sawtooth out was 20v too high). But before I could get into that, I noticed the trace would slowly disappear. Turning up intensity slightly it would come back, only to fade and so on. Then it disappeared hard fail.

    LV ok – in cal limits. HV not ok. Hartley oscillator is running. The HV test point comes up to 800-900v and immediately folds back to 400V. I probed center of intensity control (different tap on HV secondary) – same thing, so 2 secondaries act same –>implicates primary to me. V800 and V814 test strong. Pin 7 V814B -168V (10v too low). What should Pin 1 of V800 measure (Screen)?

    Have touched no calibration adjustments, as I know to find root cause and fix, vs tweak. I am measuring HV test point with VTVM with 1meg probe, other with Fluke. I noticed that unit has 19 llllbumble bees tyoe caps. My experience with these in McIntosh Amps is they are all bad. Similar story here? I have read Cl806 is problematic in HV. I have Sencore 102 cap tester but have not lifted any caps as I read that silver solder is used throughout, so I need to find where I put mine or order some more.

    Another thing I noticed, with lights out I could only see glow on 2 the 3 HV rects in crt anode supply, but viewing angles were difficult. The other 2 HV rects also did not glow, but I am getting voltages ove on those circuits, so I assume the current is to low to glow. The schematic doesn’t identify the filament supply for those tubes, but I see leads on them.

    Any thought on this? Want to restore but also need to check viability of hard to find parts. I see the HV rects and most caps avail. CRT don’t know yet.

    Would you recommend re-cap of all “PTM” type caps in parts list? There are also I’m not sure the acronym, but they are what I referred to as “bumble bees”.

    Any help greatly appreciated.


    • Hi Kirby.

      The crt supply voltage is critical because the sensitivity of the CRT varies with it, thus the calibration too.

      From what you describe, the first component I would replace is the Hartley tank capacitor that is across the primary of the HV transformer. A tester is not going to tell you if a cap will work here though if it fails on the tester, it most assuredly will not work here, so just replace it. I almost always find this necessary. Antique Electronic Supply sell 3kv 10nF ceramics, also 1kv siver micas. I would also replace all the caps in the cathode and grid supplies, again, the 3kv 10nF ceramics are perfect for this, I keep lots of them. These are not suitable for the PDA tripler however, it sounds as though that may be ok.

      You can use non-silver bearing solder just for a one-time joint. Repeated use will deplete the silver plate in the ceramic notch. I think Radio Shack sell silver bearing solder. At one time I used this twisted together with their regular rosin solder, of the same gauge. It worked extremely well, excellent flow and solidification.
      I imagine the rectifiers are OK.

      On the bumble bees. I replace them all. They are always leaky and even if the circuit functions, calibration will not be possible. In the time-base, they will cause slow running and at low speeds, very slow re-set between sweeps leading to flicker due to the hold-off between sweeps being way too long as the circuit has to supply the leakage current as well as the charge current.

      Again, AES sell a good range of 630v film caps, any of them will work and I keep a range of the common Tek values on hand.
      The 317 is a really nice scope, stay with it!
      Thanks for your interest in what I am doing.

      • Kirby Hallenbeck permalink

        Richard, thank you so much for your very detailed response. I truly appreciate it. I will get on with the project following your advice. You have a very nice day sir. Kirby

      • You are very welcome. Thank for your interest and taking the time to take care of one of these superb creations.

      • Kirby Hallenbeck permalink

        The problem turned out to be C823 was so leaky the Sencore LC102 error 07’d ( to leaky to test). It was basically a 1 meg resistor across the final two HV rects, which explains why they were glowing brighter, due to extra load. All the other PTM rects are leaky too but not this bad. I have replace all but the 10KV ones, which are on order. I used a piece of 7/8 inch Andrew Heliax coax to make a temporary capacitor to sub in to verify the diagnosis. It fired right up after that. Thanks for the help getting me started.

  2. Mark permalink

    I have a 316 and 316-S1 (serial number 470). Both appear identical. What is the difference? I cannot find anything about the S1 version or manual for the S1 type. The manual should be the same for both by visual appearance. The 316 is partially restored and the S1 is almost fully restored. I need a few higher wattage resistors and restuff the cans on this one. I have a 310A and 317 I have fully restored by replacing all carbon resistors with metal film/oxide or wirewound and condensers, lubricating the shafts and set screws on the knobs, added resistance to the higher B+ winding (lowering the B+ to the oscillator will not lower the voltage output), added a fan to the 310A (I put in a 3WP11 in this in place of the stock P2. P11 is my preference!), added a 16 ohm NTC from the mains to the pri. and calibrated them. Replacing the carbon resistors does make a difference! Look at the ppm/deg. C drift on carbon and film/oxide types. The drift is almost zero (V and H position knobs hardly used) and resistance is what is called for. Some of the 2W resistors should be 3 or 5W. I have found that Mouser has the high voltage film condensers. The ,0068mfd can be replaced with a ,01mfd. Mouser has them up to 3kV. The electrolytics are high temp. quality ones. The higher voltage ones in the power supply, I use the CDE types that are designed for high ripple, temp and long life. I do add a film or ceramic r-f bypass on the electrolytics. The CDE types I use are 450V because Mouser has 250V and 450V in this series, no 400V. This series has ones below 250V also. I do want to restore my 555 (also P11 screen) and 585A and other Teks. when I can. I look forward to that time.

    • Hi Mark.
      I do not know about the S1 variant and in fact was not aware of it until now!
      On component replacement, I find that few replacements are necessary to get an instrument back into calibration and in particular, the electrolytics are usually fine. Tek never saw the need to bypass them and I have found that even given 50 years of age, a bypass capacitor has never made a measurable difference to the performance of an instrument I have worked on. While PPM levels of drift may be observable with the carbon resistors the design of the circuits is so competent that in most locations any drift does not affect the performance while they used top quality metal film resistors in critical locations. I am not a purist however, my policy is to get an instrument into calibration with minimal component replacement.
      I do have a trigger jitter problem with one of my 547s and your approach may be the answer here. The other one is solid. Even so, the jitter only shows up when sweeping at very high speeds.
      Antique electronics has 10nF/3kV ceramics. The exception to this is the paper oil capacitors. Black Beauties are usually OK but the “bumblebee” types are always leaky.
      As you have found, it is attention to mechanical detail that pays off. This includes treating every tube socket wit deoxit as well as the switches. I also use Craig products fader lube on the pots. It appears to penetrate even the apparently sealed pots.
      Thanks for your interest and taking great care of your scopes. Obviously preservation is not for ever however it is both extremely interesting and fun!
      Richard Sears.

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