The opportunity here is an interface for a sound card that handles the input ranging, protection and differential input. Add metering, a usb interface and some method for isolating the outputs and scaling them and you could get very close to an AP's capabilities and it would not be expensive.
There should be a germanium diode across the meter to protect it. Those meters are pretty rugged and there really is very little energy across them. It took HP years to get trigger circuits that worked as well as Tek. But thats all ancient history now. Bad solder joints are essentially unknown in this level of product, unless repaired by someone untrained.
There should be a germanium diode across the meter to protect it. Those meters are pretty rugged and there really is very little energy across them. It took HP years to get trigger circuits that worked as well as Tek. But thats all ancient history now. Bad solder joints are essentially unknown in this level of product, unless repaired by someone untrained.
The solder joints were bad i think due to the heating and flexing of the power supply PCB and possibly from someone plugging and unplugging the cable on the PSU board. it caused the unit to act flaky and ultimately why it was pulled from service. the calibration sticker was only a year old when i got it so i guess they just figured due to age to pull it.
i skimmed over the manual I have for it and didn't see anything that related to the meter pegging. but maybe the manual i have is different as what i have is also a service manual. I had read the operations part previously but skipped a lot of the more service related info. I skimmed over that stuff too last night. but A-OK I wont worry about it anymore. in fact im kind of excited now to clear off the bench today and get it fired up!
i skimmed over the manual I have for it and didn't see anything that related to the meter pegging. but maybe the manual i have is different as what i have is also a service manual. I had read the operations part previously but skipped a lot of the more service related info. I skimmed over that stuff too last night. but A-OK I wont worry about it anymore. in fact im kind of excited now to clear off the bench today and get it fired up!
From reviews and co. propaganda: " ... EMU 0202 USB with PRAXIS, for 96kHz (or even 192kHz) sampling ..."
" ... unit operating at 24bits/192kHz, looped back through the AudPod. The noise floor rises quite a bit above 40kHz, which may limit reasons to use it at the 192kHz rate ..."
" ... offering pristine 24-bit/192kHz recording and playback, direct monitoring, and much more ..."
" E-MU Systems - 0202 USB 2.0 - USB 2.0 Audio Interface "
Looks like a good fit. ... at pro-music equipment stores ~~ around $130 online.
" ... unit operating at 24bits/192kHz, looped back through the AudPod. The noise floor rises quite a bit above 40kHz, which may limit reasons to use it at the 192kHz rate ..."
" ... offering pristine 24-bit/192kHz recording and playback, direct monitoring, and much more ..."
" E-MU Systems - 0202 USB 2.0 - USB 2.0 Audio Interface "
Looks like a good fit. ... at pro-music equipment stores ~~ around $130 online.
Oh boy! Today was going to be switch cleaning day on the 339a. I don't know how you guys did this? The Q-tip method is not working out so well. The wafer tracks are hard to see, and get too, much less clean. Some tracks are concealed, and impossible to even see! I have spend 30 minutes on a single wafer, and don't feel I've done anything. I need a better way. i'm stuck, as all guides i've googled show taking the switch apart first. I'm about to hose it down!
How about a small pad to soak the tracks, then spin the knobs?
A small brush? A tooth brush is too big.
How about a small pad to soak the tracks, then spin the knobs?
A small brush? A tooth brush is too big.
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First: blow ALL of the dust out ... Then I use the old faithful "radio shack" red label squirt can of "TV tuner cleaner", often made by Chemical Rubber Co. ... flood the switches good, paper towel out the excess. ... And I don't use q-tips, but exercise the switches by multiple rotations, full stop to full stop, maybe ten times or more ... power off, of course.. Let it set to "dry out" a bit, then rotate 'em again ... Give it an hour or so, then "smoke test" ..."Seems to make 'em feel jus' fine ..."
Also, whether made by HP, Agelent or repaired at which ever knock off shop, how many cold solder joints there may be ... especially around the switches. As an absolute last resort, you may have to remove, disassemble and repair those old switched. But save that after nothing else works. Analog electronics is where the fun is
If this fails to produce complete results ... See anatech's post below = Good advise.
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Hi John,
I seldom disagree with you, but I fear the advice you have posted is made without an understanding of the potential problems. If you get any fluid into a trimmer capacitor - you've messed up the meter until it can be repaired and re-calibrated. Once fluid seeps inside a trimmer capacitor, it ain't coming out with alcohol or even pixie dust. The control is now toast, but what is much worse is that the new capacitance will change with temperature.
Another point that was made earlier is that cleaning fluid may change the dielectric properties and / or leakage in the switch wafers. I was always taught to apply the minimal amount of cleaner required to the surfaces that needed treatment. Careful light rubbing would dislodge larger amounts of oxides and oxidized lubricant. The cleaning should be followed with a non-residue type cleaning wash, directed away from any other controls, or shield other controls with plastic held securely in place. A light amount of lubricating / cleaner on top of the contacts when you are done is acceptable. Just not so much that it travels!
Hi TubeMack,
For another applicator suggestion, I guess you could try a foam tip. The problem is that you need a very small amount of "fluff" or foam so that it doesn't get involved with the contact fingers in the switch. If it does, rotate the switch carefully the other way. You can easily pick any fluff out with tweezers, just don't try to really pull it out if some gets caught. My contacts started black and came out a "bronzy" colour. Perhaps there isn't enough light where you are working? So far I have successfully finished three HP 339A units without any problem, and countless other devices over the years. Notice that I never said it was easy or fun. Patience and care along with good light will get you there. It's possible you need to practice technique with something else first?
Caig De-Oxide comes in a pump can with no aerosol. You can pump some out and use an eye dropper or a needle applicator for more precise control. Or, take a solder poker and bend a tight loop or hook in the end. This will hold small amounts of fluid. I think that will give you the control you are looking for. I normally use this method for adding lubricant to control shafts and the large variable capacitors. On occasion I've had to apply cleaning solution this way, and it does work.
The GC De-Ox-Id (#10-1902) comes in a 2 oz bottle. They also supply this exact same stuff in a spray can. This should be available from the larger electronics supply houses if they carry General Cement (GC) products.
-Chris
Hi Zero Cool,
Your unit was "struck by technician" (or a wanna-be) for sure! This is not normal for an HP or Agilent product. They are extremely picky about how repairs are made. In fact, if you look at any "Bench Briefs" or other HP publications from the 50s or 60s, you will see that even way back then (when John was young ), HP was instructing everyone how to do proper repairs and solder joints. From someone I learned a lot from, his requirement was that no one should know you've been there. In other words, your work should be indistinguishable from a factory job. Since this person was Austrian, I was forced to learn these things to perfection (or close to it). For a young fella, it wasn't too much fun either! Years later, I now understand where he was coming from and consider myself to be lucky to have been taught as well as I was.
End comment on that, HP / Agilent does not tolerate poor workmanship in new products or repaired products. That extends from cleaning switches to soldering.
I seldom disagree with you, but I fear the advice you have posted is made without an understanding of the potential problems. If you get any fluid into a trimmer capacitor - you've messed up the meter until it can be repaired and re-calibrated. Once fluid seeps inside a trimmer capacitor, it ain't coming out with alcohol or even pixie dust. The control is now toast, but what is much worse is that the new capacitance will change with temperature.
Another point that was made earlier is that cleaning fluid may change the dielectric properties and / or leakage in the switch wafers. I was always taught to apply the minimal amount of cleaner required to the surfaces that needed treatment. Careful light rubbing would dislodge larger amounts of oxides and oxidized lubricant. The cleaning should be followed with a non-residue type cleaning wash, directed away from any other controls, or shield other controls with plastic held securely in place. A light amount of lubricating / cleaner on top of the contacts when you are done is acceptable. Just not so much that it travels!
Hi TubeMack,
For another applicator suggestion, I guess you could try a foam tip. The problem is that you need a very small amount of "fluff" or foam so that it doesn't get involved with the contact fingers in the switch. If it does, rotate the switch carefully the other way. You can easily pick any fluff out with tweezers, just don't try to really pull it out if some gets caught. My contacts started black and came out a "bronzy" colour. Perhaps there isn't enough light where you are working? So far I have successfully finished three HP 339A units without any problem, and countless other devices over the years. Notice that I never said it was easy or fun. Patience and care along with good light will get you there. It's possible you need to practice technique with something else first?
Caig De-Oxide comes in a pump can with no aerosol. You can pump some out and use an eye dropper or a needle applicator for more precise control. Or, take a solder poker and bend a tight loop or hook in the end. This will hold small amounts of fluid. I think that will give you the control you are looking for. I normally use this method for adding lubricant to control shafts and the large variable capacitors. On occasion I've had to apply cleaning solution this way, and it does work.
The GC De-Ox-Id (#10-1902) comes in a 2 oz bottle. They also supply this exact same stuff in a spray can. This should be available from the larger electronics supply houses if they carry General Cement (GC) products.
-Chris
Hi Zero Cool,
Your unit was "struck by technician" (or a wanna-be) for sure! This is not normal for an HP or Agilent product. They are extremely picky about how repairs are made. In fact, if you look at any "Bench Briefs" or other HP publications from the 50s or 60s, you will see that even way back then (when John was young
), HP was instructing everyone how to do proper repairs and solder joints. From someone I learned a lot from, his requirement was that no one should know you've been there. In other words, your work should be indistinguishable from a factory job. Since this person was Austrian, I was forced to learn these things to perfection (or close to it). For a young fella, it wasn't too much fun either! Years later, I now understand where he was coming from and consider myself to be lucky to have been taught as well as I was.End comment on that, HP / Agilent does not tolerate poor workmanship in new products or repaired products. That extends from cleaning switches to soldering.
Hi FastEddy,
That's an excellent way to destroy things, and the damage may not appear for years (if you're lucky).
Cleaning switches is not something that there are short cuts like the one you just proposed. This is my biggest gripe with TV repair techs - always looking for a short, quick way to finish a job. Never mind if problems are created.
You should take your servicing a little more seriously I think.
-Chris
Good lord man!! Don't do that!
That's an excellent way to destroy things, and the damage may not appear for years (if you're lucky).
Cleaning switches is not something that there are short cuts like the one you just proposed. This is my biggest gripe with TV repair techs - always looking for a short, quick way to finish a job. Never mind if problems are created.
Not with HO or Agilent. I doubt Tektronix suffers from this type of thing either. No Fluke meter I have serviced had bad connections, so it does matter who made the product after all. There are no end to bad solder connections in some brands of consumer electronics, but I doubt in Military equipment.
Just did that with an older analog preamplifier. It wasn't fun.
Well, for me it's more a satisfaction thing. Fun is designing something that works well, or solving a problem.
You should take your servicing a little more seriously I think.
-Chris
Anatech, looking at the tracks, none look black, as they are still bronze/ dusty. There is a problem though, as it's apparent there making bad connections.
BTW, here's what Caig has to say on the matter:
WARNING: Alcohol / ethanol are conductive
Are we even sure the wafers are phenolic? How could HP still be using this in the early 80's with the known issues?
I still say some must be sprayed as they are hidden from view??
BTW, here's what Caig has to say on the matter:
WARNING: Alcohol / ethanol are conductive
Are we even sure the wafers are phenolic? How could HP still be using this in the early 80's with the known issues?
I still say some must be sprayed as they are hidden from view??
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Hi TubeMack,
-Chris
While it's in it's liquid state. After it evaporates, you only have to worry about what it was carrying.
Well, to be sure, why not look types of switches up at various manufacturers. Phenolic is actually not bad for terminal strips and switch supporting wafers. It only got a bad rap with the cheapo PCB material that was available in the 70s. I don't know if you can still get it. Still, I have things I made with Phenolic PCB that still exist in good condition today, which makes these things about 33 years old now at the very least.
Sorry, but you lost me there. There are no issues beyond normal aging. HP gear has a well earned reputation for lasting, and staying in tolerance for many years.
I don't know, I managed to do these without resorting to any spray at all. It's not easy, and you may have to become creative. Try bending your cleaning stick and think outside the box. Just do not spray anything in there!
-Chris
"Sorry, but you lost me there. There are no issues beyond normal aging. HP gear has a well earned reputation for lasting, and staying in tolerance for many years."
Isn't this what we have been talking about? The issue of soaked porus wafers, making switch cleaning even harder. Fiberglass would have solved this issue. Didn't HP account for future switch cleaning?
Isn't this what we have been talking about? The issue of soaked porus wafers, making switch cleaning even harder. Fiberglass would have solved this issue. Didn't HP account for future switch cleaning?
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