HP 5335A non working ENTER key... Other eq. might use the spring loaded buttons  - Page 1
Forum section: electronics / repair

author: Turbon
author_rank: Regular Contributor
timestamp: March 20, 2016, 08:44:08 pm
content: Hi, I cleaned my counter and got the rest of the keys working by jogging the connectors but the enter key doesn't seem to work. Are these shorting types or do they send a pulse some other way?I tried to get the super test running (scale, soft, 99 and enter) but the last push won't get it going...Regards

author: Dr. Frank
author_rank: Super Contributor
timestamp: March 20, 2016, 08:50:53 pm
content: Try to press a bit harder.The keys of 5335A and also 5370A do not work properly after years.They are of normal closing type, afaik.Try to measure with ohmmeter, if it closes correctly. Compare with others.If it does not close, desolder and carefully open it.Can be cleaned.Frank

author: Turbon
author_rank: Regular Contributor
timestamp: March 20, 2016, 08:53:54 pm
content: Thank you Frank. I will open it up againin a few weeks and desolder it.BTW, is the keys the same for the supertest on both 1.0 and 1.1? My counter seem to have 1.0Regards

author: DimitriP
author_rank: Super Contributor
timestamp: March 20, 2016, 10:02:37 pm
content: There are a few differences between the versions mostly having to do with HP-IB.Not enough to worry about.If both trigger LEDs work and the trigger pots are smooth, and you can measure frequency using either channel, you are ahead of the gameAs for the ENTER key you can always swap it with a seldom used key , like VOLTS or EXT ARM ENABLE (unless you are into, that sort of thing)In the meantime, fun thread to read:https://www.eevblog.com/forum/testgear/hp-5335a-timer-counter-anything-i-should-know/

author: Turbon
author_rank: Regular Contributor
timestamp: March 21, 2016, 07:35:47 am
content: Thanks Dimitri.Triggerleds are flashing and pots are smoothChB is only relative to A so I don't find a way to measure frequency with it.Yes, swap keys if I can't clean it. Btw - when desoldering them do I have to break the melted plastic retainer dots?I'll edit this one reluctantly. The red dots is what's holding the button to the PCB. The soldering beneath is for the led under every button. So to get the button removed one needs to melt the dots, do what you need and add some melted plastic to keep the button in place. I used a red wallplug that replaced the dot, doesn't look good but it worksRegards

author: Dr. Frank
author_rank: Super Contributor
timestamp: March 21, 2016, 08:43:30 am
content: Quote from: Turbon on March 21, 2016, 07:35:47 amYou can measure Frequency and Pulse on Ch B.It's in the special menu, function 17 (FREQ B) and 20 (PULSE B). <SCALE>, <SMOOTH>, <1>, <7> and <ENTER> press is needed.Description on page 3-21, 5335A_90021 manual.Or send FN17 or FN20 over GPIB.Switches cannot be changed so easily, because <ENTER> is version w/o LED, whereas VOLT key has LED.Also, if you want to use the MATH functions including numerical inputs, mostly all keys are needed, like EEX on the VOLT key.These old switches often feel as if they are blocked, when pressed, or the spring force is very weak.In the first case, they might also need a harder press to make contact.Frank

author: Turbon
author_rank: Regular Contributor
timestamp: March 21, 2016, 03:15:09 pm
content: Right, I will desolder and clean it as a first action but when desoldering them, do I have to break the melted plastic retainer dots or does the key pop out from the red plastic compartment when desoldered? I wan't to be sure so I don't destroy anything that will be hard to fix. I believe I have tried with all kinds of benign force levels and pushing styles - none of them worked...Regards

author: DimitriP
author_rank: Super Contributor
timestamp: March 21, 2016, 07:48:55 pm
content: Not sure about the retainer dots.Also take a look at this HP key switch fixhttp://www.rbarrios.com/projects/hpswitch/

author: Turbon
author_rank: Regular Contributor
timestamp: March 21, 2016, 08:13:27 pm
content: Thanks for sharing Dimitri. Thats another future project since my instruments have the same sticky buttons syndrome.Regards

author: Dr. Frank
author_rank: Super Contributor
timestamp: March 21, 2016, 09:31:20 pm
content: Yeah,that's exactly this blocked switch syndrome, which I explained.I repaired several switches by replacing these metal springs with small pieces of flex PCB.This error may also lead to non operational switches, in extreme cases.Frank

author: Turbon
author_rank: Regular Contributor
timestamp: March 22, 2016, 04:50:07 am
content: Thanks Frank. Ok, I didn't follow you at first.Flex PCB? What's that? - Found it. Did you use a particular brand, thickness or quality?Regards

author: VK5RC
author_rank: Unknown
timestamp: March 22, 2016, 10:27:11 am
content: I have been watching this topic with interest, I have a few HP machines of that vintage, I have added to to the sticky topic about Classic etc Mechanical etc repairs etchttps://www.eevblog.com/forum/repair/vintageclassic-renovation-techniques/Thanks to all for the very useful clues.Would thin spring steel strip also work? There appears to be some available on flea bay.

author: Dr. Frank
author_rank: Super Contributor
timestamp: March 22, 2016, 11:07:07 am
content: Quote from: Turbon on March 22, 2016, 04:50:07 amWell, I used what I found in my junk boxes.. from an old digital camera, or some contact stripes, maybe.It had to be thin, flexible, elastic, and easy to cut (with scissors)Otherwise, you would need some special spring - metal - alloy to get a reliable restoring force.All metal parts which I tested simply gave up their elasticity after a few key presses.Frank

author: DimitriP
author_rank: Super Contributor
timestamp: March 22, 2016, 11:18:25 am
content: Cut to size,razor blade (from a disposable razor),feeler gauge,relay contact "arm",measuring tape,are a few "springy strips" that come to mind, if the original strip cannot be bent back into shape.

author: Turbon
author_rank: Regular Contributor
timestamp: March 22, 2016, 11:53:35 am
content: Maybe springs from oldtimers alarmclock. Hmmm. Thanks all. Exploring to do with picturesAs the springs in my keys are all there I will start with pulling one out of the enter key to see if the key can give a close or short - othervise I will need to open it up and clean it. Then I wil try to copy rbarrios method to form the spring so that it naturally finds its bending points.Now there is a business idea in this if someone will pick it up to buy broken pcbs with keys/buttons, refurbish the keys and sell them for a fiver. 26 keys times a fiver is 130$. A broken card with unobtanium components shouldn't cost more than say 30$ to keep the selling interest up (so that people still cares to sell them instead of scrapping them).Regards

author: Turbon
author_rank: Regular Contributor
timestamp: March 22, 2016, 01:55:45 pm
content: Success...Desoldered the enter key and was forced to break the plastic retairment dots to get it off. Cleaned the PCB traces which it is suppose to short. I did bend the spring and it feels OK after the treatment. Fixed all buttons that was reluctant to be pushed in by holding the edge in place and pushing the button - during that compression I took a round nail which I pushed under the spring and worked a slight bend on the spring. No need to get it out of the red plastic container. All buttons clear to go as you can see out of the last picture. Now time will tell if my bends will hold a while or foreverAfter melting the red dots away it was super fragile so I took a red wall plug and hopefully were able to melt it together with the old plastic. Seems to be allright now.Oh yes, there is a led even under the buttons that doesn't have a light pathas you can see in a few pictures.BTW: What do I refresh the rusty springs with in pic 2?Regards

author: Turbon
author_rank: Regular Contributor
timestamp: March 22, 2016, 02:12:39 pm
content: Quote from: Dr. Frank on March 21, 2016, 08:43:30 amTried this Frank but only got everything flashing at 1 Hz...I will read the manual again but I have a slight fear that there is something I need from 1.1...Regards

author: Turbon
author_rank: Regular Contributor
timestamp: March 22, 2016, 02:14:13 pm
content: Quite positive to buy a new fan...Regards

author: Vgkid
author_rank: Super Contributor
timestamp: March 22, 2016, 02:30:04 pm
content: The stock fan is pretty loud.

author: Turbon
author_rank: Regular Contributor
timestamp: March 22, 2016, 02:33:47 pm
content: Quote from: Vgkid on March 22, 2016, 02:30:04 pmNo kidding

author: Turbon
author_rank: Regular Contributor
timestamp: March 22, 2016, 03:00:53 pm
content: Quote from: Turbon on March 22, 2016, 01:55:45 pm

author: xrunner
author_rank: Super Contributor
timestamp: March 22, 2016, 03:29:23 pm
content: I've torn apart my beautiful 5334B to attempt the "sticky" key fix. What I've been doing is taking out the piece of metal and flipping it upside downand also flipping top to bottom. I put a small dot on one end before I remove it so I don't lose the original orientation.What I also decided to do, in order to make the plastic a little more "slickery", is to wet a foam applicator a little bit with Armor All, and touch it to the red plastic right next to the white push-button. If you observe the action of the metal strip, you will see that it slides a little bit against the red plastic there. I believe this makes the switch work even better.So, the buttons work like new. I may not finish it today but I'm going to do every single one and get it over with.Removing and replacing those strips is not an easy thing to do, especially for the switches in the middle of others, so be patient if you decide to attempt it.

author: Turbon
author_rank: Regular Contributor
timestamp: March 22, 2016, 03:35:18 pm
content: Yes - good thinking xrunner! When the keys gets hard to push they want to bend the wrong way! Turning them around will as you describe give them freedom to work as they "want" too.Good tip!As I see it - this have an solution. I'll be hunting silent fans now and the optionsRegards

author: Dr. Frank
author_rank: Super Contributor
timestamp: March 22, 2016, 03:55:12 pm
content: Quote from: Turbon on March 22, 2016, 02:12:39 pmThese functions are probably already available in the early versions, as it is also contained in the -90005 manual, p.3-42.Strange thing, here's the description:Frank

author: Turbon
author_rank: Regular Contributor
timestamp: March 22, 2016, 04:02:30 pm
content: I'm glad to annunce Frank that it is working as you described - now - for some reason. Well, probably still some oxides left here and there but I feel this will be good. To salubrate I ordered an Trimble GPSDO to keep it on track and a WTB for all the options from scrap machinesRegards

author: Dr. Frank
author_rank: Super Contributor
timestamp: March 22, 2016, 05:06:23 pm
content: Hooray!!Great job done.Have fun, it's really a nice unit, genuine HP-feeling, especially with the options installedFrank

author: DimitriP
author_rank: Super Contributor
timestamp: March 22, 2016, 06:34:22 pm
content: QuoteYpu could brush them and then use a rust converter chemical or...or....Dunk them in white vinegar (might take a couple of hours or overnight).Give them a light coat of machine oil.ReinsertUseEnjoy.

author: VK5RC
author_rank: Unknown
timestamp: March 23, 2016, 06:42:36 am
content: Re rust inhibition, i have had a lot of success with an Inox Lanolin oil after a light wire brushing, others have used a 'gun' oil, with success.

author: Turbon
author_rank: Regular Contributor
timestamp: March 23, 2016, 09:47:30 am
content: Thanks for the tips. I will try with vinegar first.Regards

author: xrunner
author_rank: Super Contributor
timestamp: February 11, 2017, 01:21:10 pm
content: Quote from: xrunner on March 22, 2016, 03:29:23 pmI'm baaaaaack ...Since the "fix" I performed almost a year ago - the sticky issue has re-appeared on many of the keys over time. Although they still switch OK, I do not like the stickiness. I am not convinced that there is nothing left to do, so I'm going to pull the unit and dis-assemble again to try to find a permanent solution. Right now I'm thinking it has to do with the dryness of the surfaces the metal strip is pushing and rubbing against. I'll give it my best shot. Stay tuned.

author: ManateeMafia
author_rank: Frequent Contributor
timestamp: February 11, 2017, 04:38:35 pm
content: My keypad was pretty bad. I believe I used some DeOxit on the keypad and the difference was huge. I cannot remember if it was the gold DeOxit but if it is gold plated, then that's what I used. You can try it on a single switch if you have some available.

author: xrunner
author_rank: Super Contributor
timestamp: February 11, 2017, 05:26:48 pm
content: Quote from: ManateeMafia on February 11, 2017, 04:38:35 pmWhat I think now is causing the sticking is how the little piece of metal they use as a "spring" is rubbing against the plastic of the key - the part of the plastic that makes a channel for the metal spring to flex against. I'm going to Home Depot to get a type of lubricant that I have in mind that is plastic safe. I'm going to try an experiment, and if I'm right it will make a big difference in the problem.We shall see ...

author: Lorenzo_1
author_rank: Regular Contributor
timestamp: February 12, 2017, 12:56:07 am
content: I had problems with these leaf springs falling out of place on a 3325A - some were lost. Not the best design. They proved easy to repair using spring steel from an automotive feeler gauge as suggested by others here. Just select the closest match thickness gauge (maybe ~0.005" from memory), cut it to size using regular scissors, and make small kink at one end to match the original using pliers. Getting them in place is a little tricky for the harder to get at keys but I found that a pair of curved very fine tweezers I happened to have (see pic) and a fine screw driver were enough to do the job. I've had no trouble with them since.

author: xrunner
author_rank: Super Contributor
timestamp: February 12, 2017, 03:51:40 am
content: Quote from: Lorenzo_1 on February 12, 2017, 12:56:07 amYea that's a good idea. You know it's interesting, that when you remove the springs the switch still acts to spring back when pushed, because of the way the plastic switch is made. Maybe an idea is to just forget the steel springs altogether?But, I tried an experiment and it seemed to help quite a bit. It's late now but tomorrow I'll show what I did to every single switch in the thing, something new ...

author: xrunner
author_rank: Super Contributor
timestamp: February 12, 2017, 01:13:17 pm
content: I obtained some silicone grease which is plastic-safe, and applied a very small amount to an area under the steel springs where they rub against the plastic, as shown in the pic. This seems to help quite a bit. Might be something to try for some of you.But as I said, the key with the spring removed actually does return to the off position because it has a spring effect anyway. Hmmm ...