Function Gen with Tubes - Exact 240 - Now with Manual and Schem - Page 1
Forum section: electronics / repair

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: October 06, 2015, 07:59:28 pm
content: Hi,I recently acquired an Exact 240 from a garage sale. This is a function generator that will output Square, Sine, and Triangle waves up to a whopping 10kHz! This guy has tubes, and a few transistors.I got her to power up, did it slowly with a Variac. She actually works quite well. The sine wave needs a hint more shape tweaking, but I think it can get quite nice.I am posting in the repair forum because (a) it is pretty cool vintage tech, and (b) I am looking for advice regarding the cardboard tube capacitors. I have ordered a schematic from Tucker (who else? Do they own every manual on the planet?)My understanding is that those cardboard caps are just waiting to fail. Advice I have found online suggests gutting the tubes and installing modern electrolytics inside the tubes for aesthetics.Yes, the previous owner worked at McDonnell Douglas aircraft. This unit has a cal note from Aug 1972! I assume it was made in the '60s.UPDATE: Manual here: The date is from 1962:http://meanmutha.com/Exact_240_Function_Generator_Manual_w_Schem.pdf

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: October 06, 2015, 08:00:11 pm
content: A look at the top inside. You can see all the adjustments are clearly marked. Who needs a manual!

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: October 06, 2015, 08:00:38 pm
content: Alternate angle.

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: October 06, 2015, 08:01:46 pm
content: Directly soldered on the front switches.

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: October 06, 2015, 08:02:53 pm
content: The questionable cardboard tube caps, and valve goodness.

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: October 06, 2015, 08:03:57 pm
content: Point to point connections on the "main" board.And a view of the underside.

author: Vgkid
author_rank: Super Contributor
timestamp: October 06, 2015, 08:45:04 pm
content: Very cool, I look forward to updates.

author: OldSchoolTechCorner
author_rank: Frequent Contributor
timestamp: October 06, 2015, 11:31:27 pm
content: Very nice construction, point to point wiring and the time it must have taken to do the wiring harness. Those questionable cardboard tube caps need to be replaced. I made the mistake once and left them in a tube amp, as it tested good and one day shorted and fill the room with smoke.

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: October 06, 2015, 11:53:47 pm
content: Quote from: OldSchoolTechCorner on October 06, 2015, 11:31:27 pmWould your suggestion be to clean out the existing tubes and put electrolytics inside the tubes? How hard is this to do? Do you typically have to melt wax out, or will the pull out?I am waiting on the schematics because at least some of them do not appear to have any markings. I want to make sure I get the right values.

author: vk6zgo
author_rank: Super Contributor
timestamp: October 07, 2015, 12:01:55 am
content: Quote from: FlyingHacker on October 06, 2015, 07:59:28 pmI would guess,a little bit earlier,maybe mid to late '50s.The transistor types will give a good clue as to its vintage.

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: October 07, 2015, 12:03:05 am
content: I am thinking of trying to reseal the fixed up tubes with beeswax. Supposedly this is what most of these capacitors were originally sealed with. I also bet it would be easier to get out that, say, hot snot should someone every need to replace them again in another forty or fifty years.

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: October 07, 2015, 12:09:53 am
content: Quote from: vk6zgo on October 07, 2015, 12:01:55 amI think the only transistors in the unit are the two power transistors you can see in the photos of the cardboard tubes. From the part number it looks like they are germanium. 2n554 and 2n176.

author: vk6zgo
author_rank: Super Contributor
timestamp: October 07, 2015, 12:35:21 am
content: They definitely sound like transistors from the period I referred to,or maybeveryearly 1960s.10 years are a long time,& by the end of the 1960s,transistors were mainly Silicon,& many of the type numbers familiar today were already with us.PNPs were pretty much reserved for special purposes like complimentary symmetry audio amplifiers by then,too.

author: OldSchoolTechCorner
author_rank: Frequent Contributor
timestamp: October 07, 2015, 01:49:10 am
content: Quote from: FlyingHacker on October 06, 2015, 11:53:47 pmYou have to desolder them, sometimes you have to untwist the locking tabs and once capacitor is out, then heat it and remove the cardboard cover, or drill the inside out, then you stuff it with the new capacitor and you can use hot glue is fine.

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: October 07, 2015, 01:59:04 am
content: Thanks, OldSchoolTechCorner. I found some videos on YouTube using the term "restuff".I will know more when I get the schematic, but most of these caps seem to have three or four leads, rather than two. Not sure how they are set up. Is there sometimes more than one capacitor inside a single tube?Luckily, these tubes all look like they are bolted in with flathead machine screws and nuts. So they should be pretty easy to remove once I desolder them. I will do one at a time and take pictures to make sure I get things right.Thanks.

author: OldSchoolTechCorner
author_rank: Frequent Contributor
timestamp: October 07, 2015, 02:02:15 am
content: Quote from: FlyingHacker on October 07, 2015, 01:59:04 amYou need a schematic as could be more then one capacitor, in those cans.

author: AF6LJ
author_rank: Unknown
timestamp: October 07, 2015, 02:36:40 am
content: Looks to be built in or after 1966 the two transistors in the first batch of pictures have clearly visible date codes.I love it, looks great It would be cool to see the schematic.I am betting the power supply has a series pass tube regulator for the high voltage.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 07, 2015, 02:49:24 am
content: Oooooh, sweetQuite a low frequency range on that, too. Would be a perfect complement to an analog X-Y plotter, perhaps?Those caps are electrolytic, of course; the cardboard sleeve is usually used for insulation because the case is "hot". Sometimes the markings are stamped on them; other times, they're just a blank guard, and you will find the ratings on the metal can inside.Looks like regulated heaters! Those TO-3's are 3A 40V PNP germaniums. Lots of diodes underneath, maybe two regulated pairs or something? Also guessing 6080 and 12B4 for main pass tubes, possibly something like plate-and-screen supplies, or +/- supplies. Bipolar would make sense given the low frequency range (the output certainly cannot be transformer coupled! That 12BY7 must be an output follower or something), and would necessitate the insulated capacitors, or one or two of them at least.My vintage rackmount porn, in trade:http://seventransistorlabs.com/Images/Gaussian_Noise1.jpghttp://seventransistorlabs.com/Images/Gaussian_Noise2.jpghttp://seventransistorlabs.com/Images/Gaussian_Noise3.jpghttp://seventransistorlabs.com/Images/Gaussian_Noise4.jpghttp://seventransistorlabs.com/Images/Gaussian_Noise5.jpghttp://seventransistorlabs.com/Images/Gaussian_Noise6.jpghttp://seventransistorlabs.com/Images/Gaussian_Noise7.jpgI don't have use for it at the moment, but it seems to work. First time I powered it up, the caps got awfully warm. Didn't have a variac at the time...Tim

author: AF6LJ
author_rank: Unknown
timestamp: October 07, 2015, 03:02:30 am
content: Quote from: T3sl4co1l on October 07, 2015, 02:49:24 amWay too much boat anchor goodness in this thread.

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: October 07, 2015, 04:06:14 am
content: Quote from: T3sl4co1l on October 07, 2015, 02:49:24 amIt is pretty low frequency, which is kinda cool. How were you thinking it would tie in with a plotter? I wish I had a plotter... Or maybe I should build one.QuoteI don't know much about tubes to be honest. I'm in my forties, and transistors had pretty much taken over when I was growing up. My dad had a few tube items, but he didn't want me messing with them because they were fragile and high voltage.When you say regulated heaters do mean some sort of heating element for frequency control, like an ovenized oscillator?QuoteThat looks like fun. Love the graphics on the front panel.I don't have a huge use for this Exact 240 either, but it seemed like fun to clean up. Perhaps if I need a real slow oscillator for something, maybe amplitude modulation of some sound waves or something.

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: October 07, 2015, 04:57:15 am
content: After a little research in tubes I am guessing you mean one of the tubes looks like it has two heaters in it? Or that would be the purpose of the two germanium power transistors... .??

author: vk6zgo
author_rank: Super Contributor
timestamp: October 07, 2015, 05:50:27 am
content: Quote from: AF6LJ on October 07, 2015, 02:36:40 amSo they do!I must admit I didn't go & look at the pix offsite,so couldn't blow it up big enough.When I did I could see them too.They could be replacements----OK,so I'm reaching here!I was going by the general look of the thing,plus the fact they used Germanium transistors.As a specialist device they wouldn't sell that many,so a 1966 one might not look any different to a 1959 one.Back in 1965,my then work had a self -tuning ISB transmitter which used PNPs as part of the motor drive circuit for the autotune,(it was already a few years old).It wass/n (1),& we basically did the "debugging".It kept killing the PNPs.Ultimately,a Supervising Tech & a couple of Senior Techs redesigned the circuit to use Silicon NPNs---no more problems.The EE said "well done" & went on his way!

author: Radio Tech
author_rank: Frequent Contributor
timestamp: October 07, 2015, 09:17:33 am
content: Very nice piece you have there. I would also restuff those caps to keep the original look.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 07, 2015, 09:31:50 am
content: Short intro to tubes:- They're more-or-less low transconductance, low current density, depletion mode N channel FETs. No such thing as P-channel, which makes things difficult from time to time.- Operating voltages are >10x higher than for most SS (solid state) circuits. So 100V supplies are kind of entry level, and 200-300V supplies are most common (with 500+ for power amplifiers and such; the largest ~MW size transmitter tubes are circa 30A and 30kV).- Likewise, currents are lower, like 1-10mA for signal tubes, up to 100mA for outputs. The biggest common tubes are line output / sweep tubes, used for switching the deflection and flyback inductors in TVs; they go up to maybe 1.5A peak.- Triodes are the only amplifying device that has a most nearly constant-voltage output characteristic. All others have the output characteristic (Id vs. Vds, Vg as parameter; Ic vs. Vce, Ib as parameter; Ia vs. Vak, Vgk as parameter) which rises sharply at low voltages, then levels off to a constant current ("linear") region.- In a tetrode or pentode, the screen grid acts as the triode plate (while not drawing 100% of the current), in effect setting what the plate current will be.You can also think of the screen as a second grid, where the current flow is due to the sum voltages on both grids. Difference being the screen is mu times less sensitive.The last weirdness is, the cathode doesn't do jack until you heat it up.So when I say heaters, I mean literal heaters, they make the cathode hot, so it can emit electrons! Archaic, right?!The heater is insulated from the cathode, so it can only be so-and-so voltage away from it; it's possible they have two heater supplies for two sets of heaters, one around 0V and one around -200V or so.Tim

author: vk6zgo
author_rank: Super Contributor
timestamp: October 07, 2015, 10:18:39 am
content: "FETs with a fire in 'em!""it's possible they have two heater supplies for two sets of heaters, one around 0V and one around -200V or so."Possible,but not common.The heater/filament insulation is pretty good,really,& normally there wouldn't be much of a problem.Perhaps if a tube was used in association with the cathode of an Oscilloscope CRT,that may be needed.Some older Vacuum tube rectifiers have "directly heated" cathodes,(as do high power Transmitting tubes).In that case,there is no insulation between "cathode" & "heater" as they are one & the same.Rectifiers with directly heated cathodes are used with a special power transformer heater winding which needs to be capable of operating at the full positive HT Voltage.Most "indirectly heated" tubes operate with heater voltages of 6.3volts-----even the "12volt" series of tubeshave centre taps to allow operation on this voltage.Some tubes for use in series filament chains have higher heater voltages,& tubes used in old portable radios used 1.5 volt directly heated tubes.High power Transmitting tubes usually have filament/heater voltages in the region of 6 to 7.5 volts,atlotsof amps!

author: AF6LJ
author_rank: Unknown
timestamp: October 07, 2015, 01:59:54 pm
content: Quote from: vk6zgo on October 07, 2015, 05:50:27 amVery cool...I am guessing the two TO3 transistors are for regulating the filament voltage for all but the pass tube used in the high voltage regulator. That doesn't need to be regulated and that pass tube will have its own filament winding since the cathode of the pass tube will be at a high potential. As a general rule the filament to cathode breakdown voltage is on the order of 200V.I love this old stuff, it's fun to see how they had to do things back in the day..

author: TimFox
author_rank: Super Contributor
timestamp: October 07, 2015, 02:29:42 pm
content: Kepco used to refer to tubes as "NPNs with built-in pilot lights". They kept building highish-voltage stabilized supplies with 8068 (beam-power tubes, essentially high-voltage 6L6s) pass devices until they were discontinued, since they could take far more abuse than an equivalent silicon device in laboratory applications.

author: Cubdriver
author_rank: Unknown
timestamp: October 07, 2015, 05:29:50 pm
content: Those are likely multi-section electrolytics in the cardboard cans. I see some are also mounted on phenolic wafers, too, and from a look at the backside pic it appears that they may be isolated from ground. In case you don't know (and not being a tube guy you may not), the outer can on the multi-section electrolytics is typically connected to the negative side of the cap. In cases where the negative side cannot connect to ground, they're mounted using insulating spacers, and often covered with cardboard tubes (as you have here), or shrink tubing and an insulating cap on the top (as they are on some old HP stuff I have worked on).You'll note that there are symbols near the terminals (a square, circle, triangle, 'D' shape, etc.), and on the side of the cap (may or may not be on the cardboard; if not it should be embossed into the aluminum can under the cardboard) there will be a list of the symbols, along with the associated cap section value - for instance, D 40UF 250V, (square shape) 30UF 350V, (triangle shape) 10UF 400V would be a 3 section cap, common negative, with a 40uF, 250V cap; a 30uF, 350V cap and a 10uF, 400V cap inside, connected to the terminals as indicated. They can have multiple values, and differing voltage ratings all within the same body.It takes some effort, but they can be restuffed with a bit of patience and a few tools. Modern electrolytics are often MUCH smaller physically for a similar value, and one or more of them as needed can be put in the can after the original guts have been removed. As it appears you've discovered from your online searching, there are several methods used to restuff them - some cut the can and epoxy it back together (which may be a good option for you as yours have the cardboard covers which should hide the cut); others undo the crimp at the bottom to remove the guts, then re form it with a tack hammer or the like, I prefer the latter method, though it's time consuming.I've done a few single section ones for an old HP DVM; here are some of the pics of the process:Initial opening of crimp with knife blade:Continuing to open the crimp with a small screwdriver (a small electronics vise is a big help during this process; doing it holding the cap in your hand is just begging to stab yourself, repeatedly!):Once the crimp is fully undone, things can be pulled out:I used a heat gun to soften the tar holding what remained of the dried out cap in the can and then pulled it out; the softened tar can be dug out with a pick if necessary to make room for the new replacement caps:The new cap's leads are formed and soldered to the terminal:The negative lead is brought out and soldered to the mounting ring:And finally the crimp is re formed by gently tapping it back down as you work around the perimeter, using a small hammer. The cap is shown in the vise for the photo because that's where the camera was set up and focused on, but when redoing the crimp the back end is rested on the table to prevent movement from absorbing all the force of the tapping without the metal moving. I actually rest it on the table and nest it against the heavy cast iron base of the vise, and tap at about a 45 degree angle at first to form the metal around the mounting ring and get it tight. The blows are shifted to be more parallel to the face of the cap as the metal folds down. Use very light hammer taps, rotating the cap slightly between each one to evenly re form the metal. Take your time with this step and it will fold back down nicely:The hammered part of the crimp will look a bit buggered up, but it is not visible when the cap is mounted, and I prefer this to cutting the can in a visible place.There are a few more photos of the process at:https://pmanning.smugmug.com/Electronics/Restuffing-can-electrolytics/51169977_mDp2vM#!i=4261375442&k=QLmNcB2At some point when I do another I'll make a better step-by-step sequence, and do it on a multi-section cap rather than the single section one shown here.-Pat

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: October 07, 2015, 05:41:30 pm
content: CubDriver...Thank you very much that is exceedingly helpful!Is the Cub in your name the aircraft Cub? I am a Cessna Driver myself, though I would love a Carbon Cub, or a J-3 for that matter.

author: Cubdriver
author_rank: Unknown
timestamp: October 07, 2015, 05:47:50 pm
content: Quote from: FlyingHacker on October 07, 2015, 05:41:30 pmYes, it is, though unfortunately I haven't been driving one in far too long. I need to get current and airborne again one of these years...-Pat

author: SeanB
author_rank: Super Contributor
timestamp: October 07, 2015, 06:10:34 pm
content: I would also suggest changing out the carbon composition resitors, you can see some 47k 1W carbon composition resistors in there, where there has been a replacement of one, going from a 10% carbon composition unit to a 5% carbon film one. The composition resistors will by now have drifted, mostly high, and any value over 22k will be high by some amount, some might even be over double the printed value or even close to open circuit. Any carbon composition over 1M should be checked for resistance, simplest is in circuit with no power, and see if the measured resistance is equal to or lower than the band value, as it always will go high, so higher than the print is on the way out.

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: October 07, 2015, 07:29:25 pm
content: Quote from: SeanB on October 07, 2015, 06:10:34 pmI am assuming they should be replaced with new carbon composition resistors, right? I know different types of resistors have different failure modes.

author: TimFox
author_rank: Super Contributor
timestamp: October 07, 2015, 08:06:32 pm
content: Some people think that 1960's pop music was better than later music, therefore it must have been the carbon composition resistors. The only failure-mode difference that I am aware of is that a good A-B carbon comp resistor could take a larger transient than a carbon film, due to the larger thermal mass.I would replace the 10% carbons with 5% or better metal films of the same wattage. These are readily available from Mouser and DigiKey in different brands. Note that real mil-spec metal films (e.g., RN65) have real mil-spec power ratings that are lower than the power rating on A-B carbons of the same physical size.For example, these are $0.12 each in singles, and there are many more to be found.http://www.mouser.com/ProductDetail/Vishay-BC-Components/SFR16S0001002JA500/?qs=sGAEpiMZZMtG0KNrPCHnjeX%2fDW687SXcfUuTu%252bLQn3c%3d

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: October 07, 2015, 09:33:55 pm
content: TimFox,Thanks for the info. I am no expert on resistors. I know some vintage Tek experts suggested I stick with carbon composition when replacing some that were in the startup surge protection (Inrush) of the power supply on a Tek scope. I thought they said it was because carbon film can fail shorted vs. carbon composition failing open.I doubt this is an issue here (if I even understand the issue at all).

author: AF6LJ
author_rank: Unknown
timestamp: October 07, 2015, 10:53:04 pm
content: Quote from: TimFox on October 07, 2015, 08:06:32 pmGood advice, as a general rule I only replace the ones that are out of tolerance and leave the rest, no need for all that extra work.

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: October 07, 2015, 11:01:30 pm
content: Quote from: AF6LJ on October 07, 2015, 10:53:04 pmWhen I get the documentation I will measure the resistors to see if they are within spec. I will add them to my Mouser order for the caps.Thanks.

author: AF6LJ
author_rank: Unknown
timestamp: October 07, 2015, 11:41:40 pm
content: Quote from: FlyingHacker on October 07, 2015, 11:01:30 pmGood deal;The carbon resistors tend to drift high especially if they have to dissipate a little power.They also will draw moisture from the air which will lower their value slightly, not enough to cause them to drift out of spec...

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: October 12, 2015, 07:13:43 pm
content: Hi again.For those who are interest here is the manual for this unit (with schematic).http://meanmutha.com/Exact_240_Function_Generator_Manual_w_Schem.pdfNote the date is 1962 !I see the capacitors are rated for very high voltage (500V for some). These are harder to find. But I think something like this might work for C1 and C3:http://www.mouser.com/ProductDetail/Nichicon/LGN2H820MELZ35/?qs=sGAEpiMZZMsh%252b1woXyUXj4wVC1amv8ifvA1oLceiKgo%3dThe drawback is that they have snap-in short leads. So I would have to solder extensions on. I would probably have to solder some kind of extension on any in order to hook them up to the old leads.C2A&B, C4A&B, and C5A&B (which I assume are cans with two caps each) would be:http://www.mouser.com/Search/ProductDetail.aspx?R=UVZ2W220MHDvirtualkey64700000virtualkey647-UVZ2W220MHDC9 would be:http://www.mouser.com/ProductDetail/United-Chemi-Con/EKYA250ELL222MK25S/?qs=sGAEpiMZZMvwFf0viD3Y3dL55az7zhnmKi9Mm3rr%252bMkzd%252b7%2fxwhouw%3d%3dI would appreciate any feedback on these choices. Thanks.

author: AF6LJ
author_rank: Unknown
timestamp: October 12, 2015, 07:47:11 pm
content: Looks like good choices to me.

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: October 12, 2015, 07:49:03 pm
content: Quote from: AF6LJ on October 12, 2015, 07:47:11 pmThanks for the sanity check. I am going to measure the resistors.

author: Vgkid
author_rank: Super Contributor
timestamp: October 12, 2015, 09:06:20 pm
content: When space is not an issue, I have put several caps in series to reach the desired voltage/capicitance.

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: October 12, 2015, 10:25:55 pm
content: Quote from: Vgkid on October 12, 2015, 09:06:20 pmGood point. Not as important for the capacitance in this case, but, though it makes sense, I would not have thought to do that for voltage. I think I have read that in many cases this is not a good idea, though. What happens if one fails? Does the other then fail as well? Would slightly different ESRs cause the two different caps to carry different voltages?BTW, this is an honest question. I am a hobbyist, and I don't know gobs about the subject

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: October 12, 2015, 10:28:24 pm
content: So I went through and measured pretty much all the resistors in circuit. A few were a tiny bit out of spec, like 11% high. It was mainly the lower values, the 10 ohms and 100 ohms that had the issues. Though a couple 1.5Mohm ones were a hint too high as well.I think I am only going to replace the ones that are out of spec. I would rather keep the thing more authentic, and abide by the "if it ain't broke" rule.So I am going to add these to my Mouser order and get this guy fixed up.

author: AF6LJ
author_rank: Unknown
timestamp: October 12, 2015, 10:59:50 pm
content: Quote from: FlyingHacker on October 12, 2015, 10:25:55 pmWhen properly selected they don't fail, and when they do they usually open circuit.Back in the days when transmitting tubes ruled it was common pratice to connect electrolytics in series to get the higher voltage. Equalizing resistors are used to halp compensate for differences in leakage current.This is how you get 50 MF at 3.6KV390MF @ 450V X 8

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: October 12, 2015, 11:13:12 pm
content: Interesting... The resistors are a good idea. Thanks.

author: AF6LJ
author_rank: Unknown
timestamp: October 12, 2015, 11:18:36 pm
content: Quote from: FlyingHacker on October 12, 2015, 11:13:12 pmWhen you series connect caps you need them, generally speaking the equalizing resistors should be of a value to equal 5 to 10 times the leakage current of the caps.General rule of thumb anything in the neighborhood 100K ohms is good for voltages in the 600V to 4KV range.You do need to be careful of one thing;The resistors must be rated to hold off the voltage they are going to be subjected to. Those resistors are rated for 800V.You are really better off if you don't have to do this.When I rebuilt that power supply I used good caps (Panasonic) that had a reasonablely high ripple current rating since they were used in a voltage doubler.

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: October 14, 2015, 01:13:39 am
content: I placed my parts order at Mouser. I got all the caps I listed above, which were all the proper voltage rating. For those playing along I also made sure my resistors had a high enough voltage rating. Many do not. I just got them all for 700V. They were not particularly expensive, and I wasn't buying too many of them (only bought 100 if the price break was decent enough).Looking forward to recapping the recap....

author: AF6LJ
author_rank: Unknown
timestamp: October 14, 2015, 01:31:17 am
content: Quote from: FlyingHacker on October 14, 2015, 01:13:39 amGood deal, That is going to be a fine generator when you get finished.

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: October 20, 2015, 09:45:51 pm
content: Wow! Actually restuffing the metal cans is a massive pain. Since this unit has cardboard tubes, and no metal cans exposed I am thinking about just putting the new caps in the cardboard, rather than trying to restuff all the metal cans.I don't have a heat gun, and it seems we no longer have a hair dryer either. I got into the can, but I couldn't get the inside plastic cap off without heat (or fear of breaking it). On the first one I did I managed to pull the contacts off the tabs that go into the black plastic inside cap.Any reason not to do it this way? It will look the same. I will have to glue the cardboard to the phenolic wafers somehow. Not sure what the best glue to use would be. If I fill them with hot melt it would work, but that would seem to ruin the tubes if I needed them later.

author: AF6LJ
author_rank: Unknown
timestamp: October 20, 2015, 11:51:15 pm
content: You could use silicone glue (RTV or equiv.) to glue down the cardboard tubes.Anyone have better ideas??

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: October 21, 2015, 05:41:49 pm
content: Quote from: AF6LJ on October 20, 2015, 11:51:15 pmRTV 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).

author: AF6LJ
author_rank: Unknown
timestamp: October 21, 2015, 08:31:24 pm
content: 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.

author: Cubdriver
author_rank: Unknown
timestamp: October 22, 2015, 02:10:13 am
content: 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

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: October 22, 2015, 07:19:49 am
content: 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.

author: AF6LJ
author_rank: Unknown
timestamp: October 22, 2015, 01:28:24 pm
content: 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/

author: TimFox
author_rank: Super Contributor
timestamp: October 22, 2015, 01:53:41 pm
content: Note the magic-eye tube for tuning the heterodyning RF plug-in to extend the range of this unit above 10 MHz.

author: AF6LJ
author_rank: Unknown
timestamp: October 22, 2015, 02:11:42 pm
content: Quote from: TimFox on October 22, 2015, 01:53:41 pmThat was back when Men were Men and real technicians could lift their won weight in test equipment

author: Cubdriver
author_rank: Unknown
timestamp: October 22, 2015, 05:51:28 pm
content: Quote from: AF6LJ on October 22, 2015, 01:28:24 pmThat 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

author: AF6LJ
author_rank: Unknown
timestamp: October 22, 2015, 06:25:59 pm
content: Quote from: Cubdriver on October 22, 2015, 05:51:28 pmI 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.

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: October 22, 2015, 07:35:41 pm
content: 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.

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: October 22, 2015, 07:36:26 pm
content: More

author: AF6LJ
author_rank: Unknown
timestamp: October 22, 2015, 08:05:37 pm
content: Looks Good,

author: Cubdriver
author_rank: Unknown
timestamp: October 22, 2015, 08:14:51 pm
content: Dammit, now you've given me something ELSE that I don't need but want.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

author: AF6LJ
author_rank: Unknown
timestamp: October 22, 2015, 08:20:47 pm
content: Quote from: Cubdriver on October 22, 2015, 08:14:51 pmYou could buy a car for that back then.

author: Cubdriver
author_rank: Unknown
timestamp: October 22, 2015, 08:25:18 pm
content: 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

author: AF6LJ
author_rank: Unknown
timestamp: October 22, 2015, 08:27:33 pm
content: Quote from: Cubdriver on October 22, 2015, 08:25:18 pmIndeed; 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.

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: October 23, 2015, 01:56:00 am
content: 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 3so slow! One cycle every 16 2/3 minutes...

author: Cubdriver
author_rank: Unknown
timestamp: October 23, 2015, 02:42:02 am
content: 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

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: October 23, 2015, 05:00:45 am
content: 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.

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: October 23, 2015, 05:02:27 am
content: 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

author: Cubdriver
author_rank: Unknown
timestamp: October 23, 2015, 05:58:17 am
content: 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

author: AF6LJ
author_rank: Unknown
timestamp: October 23, 2015, 10:09:38 pm
content: Quote from: FlyingHacker on October 23, 2015, 05:02:27 amWay Nice Collection. I love HP Iron.

author: crispy_tofu
author_rank: Super Contributor
timestamp: October 24, 2015, 12:56:15 am
content: Beautiful piece of kit.