To fix or buy a new scope?

[adrianblack]

Hey guys -- I need some advice. I'm a beginner hobbyist and currently own a BK Precision 1479B Scope. (30mhz dual channel analog) I bought it off Ebay about 10 years ago and when I got it, it worked flawlessly. A few years after getting it, it went into storage (in a closet) because of space constraints of where I was living. I've since moved to a big place and setup all my test gear on a workbench, but it seems the old switches are now rather dirty and things are quite touchy. It's hard to get the B channel working at all without a lot of fiddling with the controls and the A channel is also flaky now. What's frustrating is while working it may just stop working and it's hard to know if it's my circuit or the scope that is acting up. Tapping on the controls scope knobs or turning them back and forth can get things working again

The sweep time and volts/cm controls are the main culprits, but I think some of the toggles are also now dirty.... The previous owner was a a smoker too (as it really smelled like smoke when I got it) which probably didn't help.

So advice on what I should do. Should I just replace this old unit or should I try to clean it up? I have the Instruction manual and schematic for it, but reading through them there is nothing about cleaning - -just some calibration stuff.

And will other old analog scopes have the same issue? Or are brands like Tektronics much more robust? Or go digital? I'm just a hobbyist and it's more just for playing around than anything....

Thanks!

[DavidDLC]

I will try to fix it, and if I liked the fix I will keep it.

Usually when somebody asks if they have to fix or to buy a new one, more likely they are willing to buy a new one, we all love new toys !!!

David.

[adrianblack]

LOL, it's true. I was just looking on Ebay and Craigslist to see what's available....

I've just never had good luck at cleaning contact switches before -- but I suppose what harm can I do. I can't make the thing worse than it is now, since it's barely working now.

Hmm .. USB Oscilloscope -- I wonder if that could work. I do have a PC setup in my workbench too. The logic analyser could be useful for Arduino projects.
 

[Monkeh]

Get some contact cleaner and blast the hell out of everything. You really can't make things worse, and it's bound to just be some oxidisation.

[vk6zgo]

LOL, it's true. I was just looking on Ebay and Craigslist to see what's available....

I've just never had good luck at cleaning contact switches before -- but I suppose what harm can I do. I can't make the thing worse than it is now, since it's barely working now.

Hmm .. USB Oscilloscope -- I wonder if that could work. I do have a PC setup in my workbench too. The logic analyser could be useful for Arduino projects.

USB Oscilloscopes are pretty much a waste of  bench & hard drive space--I think you will be disappointed .
Fix your analog,& maybe get a USB logic analyser only.
OR spend the big bucks on a Rigol or similar.

[adrianblack]

You guys have any recommendations on the contact cleaner? I will give that a try.

I ended up Splurging on a Rigol DS1052E anyway. Only $314 shipped from Rigol North America even though it doesn't seem to be moddable anymore.  If I can get the old BK working well again I'll keep both for those times when the analog scope is more useful. I have lots of space on my new bench thankfully. :-)

I was going to try this stuff:

Hosa D5S-6 Deoxit Contact Cleaner 5% Spray
http://www.amazon.com/Hosa-D5S-6-Deoxit-Contact-Cleaner/dp/B00006LVEU/ref=zg_bs_173243_8

[alm]

The various Caig products get good reviews on the TekScopes list.

[nanofrog]

The various Caig products get good reviews on the TekScopes list.

+1 on DeoxIT products from my experience.

[adrianblack]

+1 on DeoxIT products from my experience.

Awesome -- I ordered a can from Amazon -- should be here in a day or two. Hope it's not too toxic as they will run me out of town (Portland, Oregon) for using bad stuff. LOL!

I got my hands on the service manual for the old BK 1479B as well so hopefully the old girl can continue to live on. I have no idea how old it is but the service manual says the 1479B is the 4th iteration of the chassis and the main change from the 1474, 1479 and 1479A to the 1479B is it went to a square CRT!!

[w2aew]

You can often get a good approximation of date by reading the date codes on the semiconductor/IC packages.

[adrianblack]

I opened it up last night to check things out -- there are literally a handful of ICs in there. About 6. They are all just regular 74LS00, I think a 555 and maybe an op-amp. :-) I'll take a look to see if I can get some info back from their year/week codes. :-)

[adrianblack]

Well, the contact cleaner worked a treat and the old BK is working flawlessly again... In fact, better than when I got it. There is absolutely no noise on any of the switches or knobs, which really shocks me.

Now, question about it -- running the same waveform through both my new Rigol (now 100Mhz) and the old BK shows some slight ripple on the BK. Do you guys think this is in the waveform (but not seen on the Rigol due to 8bit sampling) or is it some artifact of the analog scope? I had the BK running nearly as fast as it can go (5X mag was selected) ... just curious really. (See picture below)

I have put it back together, gave the front face a good cleaning and rearranged my bench to have both the Rigol and the BK.

One more question too -- I could not figure out how old the BK was. I have the user manual, service manual and scrutinized the unit -- and could not find a date anywhere. Even the ICs were not marked with any kind of date code. (All 5 of them) Anyone know about this scope?


Love it!









--Adrian

[vk6zgo]

If you "zoom in" to the same spot where you saw the ripple,you should be able to see it on the Rigol,if is really there.
You can't do this,or its equivalent, with the B&K,because you don't have a delayed timebase.

Have you tried looking at the B&K trace with the same time/cm setting,& no input.
If the ripple is caused by the 'scope itself,you should see it.

Looking at the tube label,I would guess mid 1980s to mid 1990s.
The older labels were different,& would be showing some signs of age,but your label is still "new-looking,which is characteristic of the labels of that era.

[retiredcaps]

One more question too -- I could not figure out how old the BK was. I have the user manual, service manual and scrutinized the unit -- and could not find a date anywhere. Even the ICs were not marked with any kind of date code.

Any date codes on the caps?  I know modern electrolytic capacitors have something like 0633 to denote 2006 week 33.

[Rerouter]

the horizontal magnifier on the 10-40Mhz older scopes usually has a few warnings about loss of calibration and such, however being how the ripple is only on the negative, its very likely something from your source, or connecting cables, if it was mains hum or HV chopper EMI, you would see it on the entire waveform, 

[w2aew]

Also, try reversing the order of connection - put the Rigol on the "tee" and the terminated end at the B&K - then see if the ripple is still there or if it moved to the Rigol (transmission line reflection?).  It is certainly possible however that the old B&K's vertical preamp has got some linearity and group delay issues that can lead to such ripple.

[saturation]

There is an interesting history behind the contact cleaner used in Dexoit, its stretches back to the 1950s and has quite a bit of intrigue. 

As we all need a superb contact cleaner and Deoxit or Cramolin remain one of the few recommended by metrology labs to maintain top notch equipment; its interesting what relationship existed between the US brand and the original one developed in Germany.

http://www.siber-sonic.com/electronics/caig.html

https://www.buerklin.com/default.asp?event=ShowArtikel%2812L1000%29&l=e#ArtNr_12L1000


Although the Caig site is fairly kitchy, IMHO, it is fairly 'open' and you can obtain quite a bit of technical material on their products; the MSDS shows what's in it, to the best possible without trying to decipher the secret ingredients.

The various Caig products get good reviews on the TekScopes list.

+1 on DeoxIT products from my experience.

[adrianblack]

Wow. That is pretty cool reading. I once used some crappy Radio Shack cleaner which was useless. I was so surprised that this stuff worked so well.

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