Author Topic: My Tektronix 310 "Basket Case" Project  (Read 415 times)

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Offline Smoky

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My Tektronix 310 "Basket Case" Project
« on: September 07, 2019, 12:38:06 am »
I found a Tektronix 310 oscilloscope at a garage sale a few weeks ago. It's in really bad shape and was going to be thrown out.

Even though I'm a beginner in the electronics hobby, I know we're going to bring this thing back to life!

I'm starting with a good cleaning since it's full of cobwebs and over 60 years worth of dirt.

The serial number stamped on the faceplate is 1499, and from what I can see, most of the tubes are dated 1956.

What is very cool is a guy by the name of Elbert replied to my ad on Craigslist yesterday where I was wanting vacuum tubes. He's 86 and a U.S. Signal Corps Veteran. He says that he has a suitcase full of new tubes from the 1950's. From the picture he sent me, I see several tubes that work in this scope! I meet with him tomorrow morning.

Let the fun begin :)

828510-0

828486-1

828492-2

828498-3

828504-4

« Last Edit: September 07, 2019, 06:22:53 pm by Smoky »
 
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Online xrunner

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Re: My Tektronix 310 "Basket Case" Project
« Reply #1 on: September 07, 2019, 12:44:34 am »
Cool deal Smokey, please keep the thread going so we can follow!  :popcorn:
I am a Test Equipment Addict (TEA) - by virtue of this forum signature, I have now faced my addiction
 

Offline Smoky

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Re: My Tektronix 310 "Basket Case" Project
« Reply #2 on: September 07, 2019, 01:38:36 am »
Will do Xrunner!

I'm repairing a Leader LBO-302 oscilloscope in another thread but I'm waiting for parts and a new scanner to share its schematics.

So, in the meantime, I'm prepping this Tektronix 310 for a Winter project :)

I didn't power-on the 310 because I could see bad tubes through the side panels. The tops of some of the tubes are white and two were cracked.

While I was slowly in the process of removing the heavy layer of "mold" from all of the wires, and when I made it to the HV board area, I noticed the same "white" area on a "5642" rectifier tube!



« Last Edit: September 07, 2019, 03:31:02 am by Smoky »
 
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Offline Smoky

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Re: My Tektronix 310 "Basket Case" Project
« Reply #3 on: September 07, 2019, 01:57:32 am »
While I'm moving along the interior of the 310, I'm checking resistors as I go.

Several of the resistors just on the HV board are out of tolerance. Most have silver bands (10%).

Now that little black resistor, that's a 1.5 Meg Ohm 1% type, it still measures 1.495 Meg Ohms on my DMM after all of these years!

What would be the best choice of replacement resistor for the bad Allen Bradley's that I find?

 

Offline Smoky

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Re: My Tektronix 310 "Basket Case" Project
« Reply #4 on: September 07, 2019, 02:39:16 am »
On Wednesday night, I started to snip all of the wire loom wrap to release the tightly-gripped wires.

This allowed me to clean all of the crap easily from the sheathes and bring out all of the colors. I used a small bucket of hot water with dish-washing soap and a little bit of Clorox bleach along with small brushes. Now I can easily trace wires around the chassis.

I removed the piano hinge from the back of the case which made access even better.

I have 1/2 of the scope cleaned very well and you can see in the last picture where that transition is.







« Last Edit: September 07, 2019, 02:44:58 am by Smoky »
 

Offline Smoky

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Re: My Tektronix 310 "Basket Case" Project
« Reply #5 on: September 07, 2019, 03:26:31 am »
I removed the cathode ray tube to gain more access too. It's a Dumont 3WP2.

The heater pins are 1 and 12 and I do get continuity.



« Last Edit: September 07, 2019, 03:33:51 am by Smoky »
 

Online DaJMasta

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Re: My Tektronix 310 "Basket Case" Project
« Reply #6 on: September 07, 2019, 04:28:10 am »
What would be the best choice of replacement resistor for the bad Allen Bradley's that I find?

They're just reasonable power carbon composite resistors, so virtually any comparable resistor will do the job.  I'd probably go for thick film or metal oxide 5%s, maybe avoiding wire wound in case there are parasitic inductance issues... maybe look for the ones that best fit the look you want.

Worth mentioning that it seems like a lot of the brown half watt or 1W Allen Bradley mil spec resistors drift up over time, so a huge number of even the old stock ones won't be their original value, so I'd probably avoid replacing them with direct replacements.
 

Offline Smoky

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Re: My Tektronix 310 "Basket Case" Project
« Reply #7 on: September 07, 2019, 07:13:39 am »
Thank you DaJMasta.

I pulled a couple of resistors to test from around the scope. Here's a 2 watt Allen Bradley 33K testing high.

I own tube amplifiers from Cary Audio and they use a lot of the Vishay Dale CMF style of metal film resistors (RN65D) in 1/2 watts. I like them, but I'm finding a lot of 2 watt Allen Bradleys going bad, so I'm still looking.




« Last Edit: September 07, 2019, 07:15:22 am by Smoky »
 

Offline Smoky

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Re: My Tektronix 310 "Basket Case" Project
« Reply #8 on: September 07, 2019, 11:01:18 am »
I was just sent the 310 schematics dated 1957 that match this scope  :clap:

Block Diagram  830181-0

CRT  830175-1

Heater & LV Power  830187-2

Calibrator  830193-3

Preamplifier  830199-4
« Last Edit: September 09, 2019, 01:36:05 am by Smoky »
 

Offline bd139

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Re: My Tektronix 310 "Basket Case" Project
« Reply #9 on: September 07, 2019, 11:17:02 am »
Thanks for writing this up so far. Good to see someone taking care of such a nice instrument  :-+

As for the carbon comp resistors, they always go high. Haven't found any vendor that isn't vulnerable to that...



I usually replace carbon comp with the blue TE connectivity metal oxide resistors.
 

Offline Smoky

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Re: My Tektronix 310 "Basket Case" Project
« Reply #10 on: September 07, 2019, 11:33:48 am »
...and the rest of the schematics  :-+

Horizontal Amplifier  830205-0

Vertical Amplifier  830211-1

Sweep Generator  830217-2

Sweep Trigger  830223-3

Sweep Timing Switch  830229-4


What is so nice is that the schematics also identify the wire color in the LV and CRT circuit!
« Last Edit: September 09, 2019, 01:13:55 am by Smoky »
 

Offline duak

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Re: My Tektronix 310 "Basket Case" Project
« Reply #11 on: September 07, 2019, 04:13:49 pm »
If you replace the resistors with metal film types, make sure their voltage rating is not exceeded.  eg., a 1M0 1/2 W RN65 would dissipate 1/2 W with 707 V across it, but it has a maximum voltage rating of 350 V.  This is most likely with the parts in the EHT and around the CRT.

Looks like it's cleaning up well.  Interesting project - hope there's no show stoppers.  I don't think there's anything too biodegradable (ie. self-destructing) like in some modern equipment.
 

Offline Smoky

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Re: My Tektronix 310 "Basket Case" Project
« Reply #12 on: September 07, 2019, 05:47:41 pm »
Thank you Duak!

 I found this chart that converts Allen Bradley resistors to Vishay resistors.

 It has the voltage information in each column so it's easy to see if that rating is equal or greater.

 I believe that the Allen Bradley EB (1/2w), GB (1w), and HB (2w) series resistors are in the Tektronix 310.




...and here are the new tubes I picked up this morning at Elbert's place, a $1.50 each.

He had so many tubes to look through my eye started to cross :)



And the new 5462 "half-wave" vacuum rectifiers under $2 each too:




My plan is also to bypass the Selenium rectifiers with silicon rectifiers. I have these 1000VDC Silicon bridge rectifiers from a previous project and I plan to use them. I'll probably fabricate an aluminum heat shield/protective cap/cover for them too. Maybe even mount some of the old rectifier parts to keep the look original. Here is a picture of the Selenium rectifiers in the 310 and the new rectifiers:



« Last Edit: September 19, 2019, 02:52:56 am by Smoky »
 
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Offline Smoky

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Re: My Tektronix 310 "Basket Case" Project
« Reply #13 on: September 13, 2019, 11:35:21 pm »
This weekend I'm going to spend a little time to put together a parts order for Digi-Key and Mouser.

For example, here is C722, a 3Kv .0068uf film capacitor from the HV circuit board in the CRT circuit, being tested on the Sencore Z Meter  :o



As for the ceramic disk capacitors, C730 is a .01uf that measured 1100pf. In the service manual, the tolerance is "GMV" and not a percentage. What is "guaranteed minimum value" and does the capacitance test results indicate a problem?






...and why not a sample of some of the plastic tubular .01uf caps (C612, C613, C639, and C671). All from the LV power supply circuit and reading 5 times higher!



Here's the Big Kahuna, C315. The 0.1uf cap on the UHF input jack of the preamplifier. 5.43uf!



This scope will get the finest parts available :)

*Parts are starting to come in. The only resistors I had a hard time finding new on Digi-Key, Mouser, or Newark are R721 on the HV board, R722 on the Intensity pot, and R742 on the Focus pot. These are 2 Watt 5.6 Meg Ohms and a 3.9 Meg Ohm. I'd like to thank Kb4dmf on Ebay. He sent me NOS Ohmite and AB resistors better than 1% tolerance:





And I found this interesting, a radioactive symbol on one of the new tubes and its box!

« Last Edit: Yesterday at 08:54:02 pm by Smoky »
 
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