Author Topic: Function Gen with Tubes - Exact 240 - Now with Manual and Schem  (Read 11625 times)

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Offline FlyingHacker

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Re: Function Gen with Tubes - Exact 240 - Now with Manual and Schem
« Reply #50 on: October 21, 2015, 05:41:49 pm »
You could use silicone glue (RTV or equiv.) to glue down the cardboard tubes.
Anyone have better ideas??  8) :)

RTV might be a good plan. Something high temp, as the tubes do get pretty warm.

I got the new caps in; I used a few dabs of hot snot to get the caps to stay in place while I soldered them. After that, the stiff point to point wiring ought to hold them in place even if the hot snot fails. I also changed a couple of resistors. I need to check which other resistors I want to change and then calibrate this guy up.

I think I will test whatever glue I plan on using on a toilet paper tube. That way I can see if it soaks through or causes discoloration. The original tubes are wax coated, which should be even better protection. I think leaving the caps in thick cardboard tubes will definitely shorten their life, but it does look much better than the loose modern caps.

I almost wonder if cyanoacrylate (Super Glue) would work well. The tubes are lightweight. I just want to avoid adhesive creeping out under the edges as much as possible. That is my biggest concern with RTV or hot snot (and coming unglued due to heat with hot snot).
--73
 

Offline AF6LJ

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Re: Function Gen with Tubes - Exact 240 - Now with Manual and Schem
« Reply #51 on: October 21, 2015, 08:31:24 pm »
It is not likely to get over 55C in there unless you live where it gets really hot indoors.
So even Hot Snot would work fine, being wax coated inside may be problematic when it comes to getting anything to stick to the inside of those cardboard tubes.

As for shortening the life of the caps, I kind of don't think it would be that bad, unless you plan on leaving the function generator on 24/7.
Sue AF6LJ
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Offline Cubdriver

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Re: Function Gen with Tubes - Exact 240 - Now with Manual and Schem
« Reply #52 on: October 22, 2015, 02:10:13 am »
A bit late to the party as it sounds like you have things under control and have come up with an alternate method of mounting the replacements, but for softening the tar you could get a pot of water boiling on the stove and immerse the top of the metal can in if for a bit until it softens.  A way to get a grip on the old, dried out roll of foil is to drive a good sized (#8-10 x 2-3" long) wood screw into the center of it about an inch or two (obviously not deeply enough to damage the far end of the can, and then grabbing the protruding part of the screw with a pair of pliers to pull the dead cap out of the can once the tar has softened.

FWIW.

-Pat
If it jams, force it.  If it breaks, you needed a new one anyway...
 

Offline FlyingHacker

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Re: Function Gen with Tubes - Exact 240 - Now with Manual and Schem
« Reply #53 on: October 22, 2015, 07:19:49 am »
Nice idea with the screw, Cubdriver.

I ended up not using the metal cans, but rather just the cardboard tubes. I used hot snot in the end. It worked fairly well. There was one tube in the corner I was not totally pleased with, but it looks pretty darned good. Once you put the mesh case on you would never see the 1/8 inch of glue sticking out from that one. It sounds a little over the top, but I strive to either do things in the best way possible, or the cheapest/fastest way possible. I hate it when things are not perfect if I have opted for the former. I expect thing will not be perfect with the latter.

I calibrated this unit up, really well, actually. At first I had a DC offset issue with the triangle wave output. It was much higher than the other waves, way up above the centerline. I started suspecting a resistor attached to the triangle wave DC offset pot. So I de-soldered one leg. It measured fine so I soldered it back on. Then it worked! I was in the right place, but looking at the wrong thing. I guess it was a bad solder joint.

So I fixed that.

I guess duty cycle meters and frequency counters weren't too popular in 1962. The calibration procedure uses the scope graticules (remember those scopes had no cursors) for timings.

The calibration procedure does have a very interesting method for setting the duty cycle of the square wave. It really is worth taking a look at (and trying with a circuit or function generator with an adjustable duty cycle). It has you toggle the trigger slope back and forth while making the adjustment. It was spot on according to the duty cycle meter after doing it with the scope method!

It then goes on to have you set the triangle duty cycle by giving you a voltage level to which to set the base of the triangle wave. This was very imprecise. After calibrating once I ended up going back and redoing most of the cal in order to set the duty cycle of the triangle wave correctly using a duty cycle meter.

So in the end, I ended up with a pretty darned accurate, low frequency function gen. It can go down to a very low frequency (one cycle every 1000 seconds I believe). It can only go up to 10kHz, but that is sometimes all you need. It can generate and output SIMULTANEOUS square, triangle, and sine waves, as well as the main output, which does those, but also has an attenuator and a DC offset control.

The thing can also be used to heat the room if it gets too cold in the winter! Those tubes are quite warm. I will post some pics soon.
--73
 

Offline AF6LJ

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Re: Function Gen with Tubes - Exact 240 - Now with Manual and Schem
« Reply #54 on: October 22, 2015, 01:28:24 pm »
In 1962 a frequency counter took up about eighteen inches of vertical rack space and could have over 60 tubes in it. It was easily one of the most expensive instruments in the lab back then. http://www.cs.ubc.ca/~hilpert/e/edte/HP520/

Sue AF6LJ
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Offline TimFox

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Re: Function Gen with Tubes - Exact 240 - Now with Manual and Schem
« Reply #55 on: October 22, 2015, 01:53:41 pm »
Note the magic-eye tube for tuning the heterodyning RF plug-in to extend the range of this unit above 10 MHz.
 

Offline AF6LJ

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Re: Function Gen with Tubes - Exact 240 - Now with Manual and Schem
« Reply #56 on: October 22, 2015, 02:11:42 pm »
Note the magic-eye tube for tuning the heterodyning RF plug-in to extend the range of this unit above 10 MHz.

That was back when Men were Men and real technicians could lift their won weight in test equipment :)
Sue AF6LJ
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Offline Cubdriver

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Re: Function Gen with Tubes - Exact 240 - Now with Manual and Schem
« Reply #57 on: October 22, 2015, 05:51:28 pm »
In 1962 a frequency counter took up about eighteen inches of vertical rack space and could have over 60 tubes in it. It was easily one of the most expensive instruments in the lab back then. http://www.cs.ubc.ca/~hilpert/e/edte/HP520/


That is a cool old beast, and I've been half keeping an eye out on the off chance of getting a chance to snag one (though shipping costs would be horrendous).  I need one like a hole in the head, but then again that can really be said about a lot of the stuff I buy...

-Pat
If it jams, force it.  If it breaks, you needed a new one anyway...
 

Offline AF6LJ

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Re: Function Gen with Tubes - Exact 240 - Now with Manual and Schem
« Reply #58 on: October 22, 2015, 06:25:59 pm »
In 1962 a frequency counter took up about eighteen inches of vertical rack space and could have over 60 tubes in it. It was easily one of the most expensive instruments in the lab back then. http://www.cs.ubc.ca/~hilpert/e/edte/HP520/


That is a cool old beast, and I've been half keeping an eye out on the off chance of getting a chance to snag one (though shipping costs would be horrendous).  I need one like a hole in the head, but then again that can really be said about a lot of the stuff I buy...

-Pat
I think it would be very cool to have a couple a three six foot racks full of old HP and Tektronix gear, It's just fun to run that old stuff.
Sue AF6LJ
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Offline FlyingHacker

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Re: Function Gen with Tubes - Exact 240 - Now with Manual and Schem
« Reply #59 on: October 22, 2015, 07:35:41 pm »
I love that giant counter.

Here are some pics of the Exact. It is nicely in spec. I do need to see if I can get more of the gum to come off.

You can see I am confirming this precision with my Nixie tube HP 5512A, which was one of the early transistorized frequency counters from the '60s. I am not sure as to the specific year. I will do a teardown on it some day, but it is now a little bastardized, as I did not re-stuff the old caps, but merely soldered in new ones to the wires. Works great. Just not authentic looking inside, and required some, err... electrical tape due to some T soldering (which were original) and a bad install of a piece of shrinkwrap. The counter officially goes to 300kHz, but it is perfectly accurate to just over 600kHz as compared to more modern counters.
--73
 

Offline FlyingHacker

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Re: Function Gen with Tubes - Exact 240 - Now with Manual and Schem
« Reply #60 on: October 22, 2015, 07:36:26 pm »
More
--73
 

Offline AF6LJ

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Re: Function Gen with Tubes - Exact 240 - Now with Manual and Schem
« Reply #61 on: October 22, 2015, 08:05:37 pm »
Looks Good, :)   :-+ :-+
 
Sue AF6LJ
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Offline Cubdriver

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Re: Function Gen with Tubes - Exact 240 - Now with Manual and Schem
« Reply #62 on: October 22, 2015, 08:14:51 pm »
Dammit, now you've given me something ELSE that I don't need but want.   |O   :-DD  I see the HP5512A listed in both my 1965 and 1969 catalogs, but it's gone by 1972 (I don't have catalogs for '70 or '71).  In both catalogs, it lists for $1050 - a healthy chunk of change back then!

Sharp looking little frequency counter.

-Pat
If it jams, force it.  If it breaks, you needed a new one anyway...
 

Offline AF6LJ

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Re: Function Gen with Tubes - Exact 240 - Now with Manual and Schem
« Reply #63 on: October 22, 2015, 08:20:47 pm »
Dammit, now you've given me something ELSE that I don't need but want.   |O   :-DD  I see the HP5512A listed in both my 1965 and 1969 catalogs, but it's gone by 1972 (I don't have catalogs for '70 or '71).  In both catalogs, it lists for $1050 - a healthy chunk of change back then!

Sharp looking little frequency counter.

-Pat

You could buy a car for that back then.
 :popcorn:
Sue AF6LJ
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Offline Cubdriver

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Re: Function Gen with Tubes - Exact 240 - Now with Manual and Schem
« Reply #64 on: October 22, 2015, 08:25:18 pm »
I know - that's always been my gauge of relative cost.  The '69 Catalina I got from my aunt when I was in HS cost about $2900 new, IIRC.  The house I live in was about $19k back in 1962.  Realizing this makes you stop and think just how much this stuff actually cost back then.

-Pat
If it jams, force it.  If it breaks, you needed a new one anyway...
 

Offline AF6LJ

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Re: Function Gen with Tubes - Exact 240 - Now with Manual and Schem
« Reply #65 on: October 22, 2015, 08:27:33 pm »
I know - that's always been my gauge of relative cost.  The '69 Catalina I got from my aunt when I was in HS cost about $2900 new, IIRC.  The house I live in was about $19k back in 1962.  Realizing this makes you stop and think just how much this stuff actually cost back then.

-Pat

Indeed; if you were making six bucks an hour back then that was good money, bread was twenty one cents and gas.... out here twenty two cents per gallon.
Sue AF6LJ
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Offline FlyingHacker

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Re: Function Gen with Tubes - Exact 240 - Now with Manual and Schem
« Reply #66 on: October 23, 2015, 01:56:00 am »
Wow, those things were not cheap. I guess a scope was as much or more, though, right? The reason the calibration procedure would not specify a cointer, but rather a scope would be that everybody would have to have a scope, even if it was expensive, but few would have the counter, I suppose?

Yes, that 5512A was bought off ePray on a whim for $30. I wish it was higher frequency, but it is a very nice design both inside and out. It makes a perfect companion to this Exact 240, given the frequency. The HP has a cool mode where you can see it count the frequency with every gate. So it ramps up from zero to the frequency over the gate time. Then you can vary the delay before the next gate. It's kinda fun to watch.

I set the HP in count mode, and the exact to 0.001 Hz... I gave up at a count of 3  :palm:  so slow! One cycle every 16 2/3 minutes...

--73
 

Offline Cubdriver

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Re: Function Gen with Tubes - Exact 240 - Now with Manual and Schem
« Reply #67 on: October 23, 2015, 02:42:02 am »
That makes sense to me - a scope has a wider application than a counter, and so it would, I'd expect, be more likely that an organization would have a scope than a counter.

And yeah, cheap is something that it doesn't seem HP equipment ever was.  But then again, several of us here have numerous pieces of it that are close to or have passed the half century mark and are still operational with little or no maintenance, so, as with so much in life, you get what you pay for.  It's amazing to me to be able to get this stuff (which, while it is technically obsolete, is still perfectly functional) for literally pennies on the dollar compared to its original cost.  Add to that the fact that the manuals have detailed schematics and troubleshooting information, and life is good other than the occasional irreplaceable part.  And even for many of the irreplaceable parts substitutes can be found or workarounds otherwise devised.

-Pat
If it jams, force it.  If it breaks, you needed a new one anyway...
 

Offline FlyingHacker

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Re: Function Gen with Tubes - Exact 240 - Now with Manual and Schem
« Reply #68 on: October 23, 2015, 05:00:45 am »
Totally. I got back into electronics as a hobby less than a year ago. So I have been building up a bench. I have opted for old, professional level equipment. It is much easier to fix, and I learn something when I do.

I would much rather have knobs and buttons on my bench than a touch screen. I do too much with high end computers in my work (Visual Effects). I want something a little more tangible.
--73
 

Offline FlyingHacker

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Re: Function Gen with Tubes - Exact 240 - Now with Manual and Schem
« Reply #69 on: October 23, 2015, 05:02:27 am »
Speaking of HP (which I now call Haytch-Pee after hearing Dave say it so many times) I assume you have seen this cool guy:

http://www.kennethkuhn.com/hpmuseum/index.htm
--73
 

Offline Cubdriver

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Re: Function Gen with Tubes - Exact 240 - Now with Manual and Schem
« Reply #70 on: October 23, 2015, 05:58:17 am »
Yep.   :)  He has quite the collection of ship holding devices there.  That website is definitely a valuable resource, and prompted me to start searching out and buying copies of the HP catalogs from down through the years.  I now have about 16 or 17 of them from 1963 on, and they're very useful when poking about on eBuy to determine what the various options are, what accessories might be needed, etc.

On top of that it's just cool to thumb through them to see what was available when, and for how much.  For instance, the 5245L counter was introduced in 1963, and that year cost $3250, and went extinct some time between 1979 and 1982. (It's in the '79 catalog for $5k, and no longer in the '82 catalog.  I don't yet have '80 and '81 in my collection.)  It's pretty impressive that an instrument introduced in the early 60s was still available at least 16 years later - no doubt for companies that had it written into test procedures and would have found buying a new one for $5k preferable to re-writing and requalifying the procedure with some new device.

And of course, like the equipment shown inside, the catalogs are things to behold, too - hardcover books of (typically) 500-600 + pages, with plenty of illustrations, specs, prices, etc.  Enjoyable geek reading material.

-Pat
If it jams, force it.  If it breaks, you needed a new one anyway...
 

Offline AF6LJ

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Re: Function Gen with Tubes - Exact 240 - Now with Manual and Schem
« Reply #71 on: October 23, 2015, 10:09:38 pm »
Speaking of HP (which I now call Haytch-Pee after hearing Dave say it so many times) I assume you have seen this cool guy:

http://www.kennethkuhn.com/hpmuseum/index.htm
Way Nice Collection. I love HP Iron.
Sue AF6LJ
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Offline crispy_tofu

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Re: Function Gen with Tubes - Exact 240 - Now with Manual and Schem
« Reply #72 on: October 24, 2015, 12:56:15 am »
Beautiful piece of kit.  :popcorn:
 


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