Oscilloscope Poll! How many do you own?

[stj]

Re: Oscilloscope Poll! How many do you own?

there are 2 toasted resistors in the foto for a start - i wouldnt power it up till i trace those to see why they burned.

[eccerr0r]

Re: Oscilloscope Poll! How many do you own?

Chances are, whatever those could have damaged already damaged...

Just curious what circuitry that is. Then again a vast majority of CRO problems are PSU.

[Agent24]

Re: Oscilloscope Poll! How many do you own?

I see two transistors and two wires going to the tube, perhaps one of the deflection outputs?

One or both transistors going shorted might explain the burnt resistors. The blown filter capacitor for that transformer output and supply might explain shorted transistor(s).

[eccerr0r]

Re: Oscilloscope Poll! How many do you own?

Except the transformer usually does not deal with the deflection circuitry directly. Transformer is probably LVPS. Curious to know if we get a dot or line on the screen or not on the afflicted scope. Would tell if the resistors were part of the LVPS or the deflection that's got problems...

[stj]

Re: Oscilloscope Poll! How many do you own?

i wouldnt even plug it in like that.

[eccerr0r]

Re: Oscilloscope Poll! How many do you own?

But seriously, if it was turned off like that, what's the chances it was working just before it was turned off?

Likely the damage has already been done.

[stj]

Re: Oscilloscope Poll! How many do you own?

you can always make things worse - specially if the main caps are fucked.

[Agent24]

Re: Oscilloscope Poll! How many do you own?

You can always cook the transformer from shorted capacitors. Then forget it!

[juliadream]

Re: Oscilloscope Poll! How many do you own?

The resistors are on the +30v and -30V line.. which feeds pretty much everything. They measure 36k in circuit. didn't bother testing them out of circuit.. probably o/c... they should be 33 ohms.. well cooked.. I managed to source the proper manual (if anybody would like a copy fire me a pm with your email) .. I've unhooked the resistors at one end and checked for shorts elsewhere and found nothing to cause much concern.. because the 50V caps are all bad..one has vented completely dead short.. it's partner on the -30V is reading about 12 ohms.. not quite a dead short.. the others are all bulging.. nice (cheap enough to replace anyhow) the blue ones.. the hv 16µ ones are ok.. but will be changed anyway.. made in 1974.. I don't believe in a God.. and if there was one I'd still be replacing them !!

The resistors have done their (probably unintended) job and gone high protecting the rest of the circuitry..

I have EHT and a nice spot on the screen.. no worries there.. CRT good.. EHT circuit good.. will be replacing the 2M2 resistors over on that board too.. if they go off to infinity and beyond they will take out the 16µ 450V caps.. and 22µ at that voltage are quite a price.. forget axials.. (goes pale and starts shaking.... already gone grey)

A few caps and resistors on order now.. once they arrive I will do the work and test the psu.. It's been a while since I had a vintage scope to work on.. it was a pretty budget model back in the day.. all off the shelf parts which are still easily and cheaply available, unlike some of the "premium" brands I could mention..

ps.. If the TX was cooked I would just patch up a basic switch mode psu.. +/-30V.. 220v and 1.4KV.. (maybe from a crt tv flyback winding even) easy.. heaps of scrap plasma psu boards in my parts heap.. and a few crt monitor panels.. but it's a scope.. so new rather than 10 year old recycled caps..

Defo the seller killed it.. he had traces on the screen.. showed me a pic on his phone.. before getting my £5 off me.... because like most people.. no understanding that you open this 40 year old stuff and check it before plugging it in !!

Thanks for your interest.. it's a nice vintage cheap 10MHz (chop) dual trace.. I used one of these back in the day at my first job.. nearly 35 years ago now.. little bit touchy about triggering reliably.. but I want it for audio amps and various lf signal tracing.. hum busting in tube amps.. that kind of stuff.. so 100MHz and up is not much use to me..

[eccerr0r]

Re: Oscilloscope Poll! How many do you own?

I really should try to fix the chop mode of my 20MHz analog scope (sometimes alt mode just isn't what you want), though without schematics it's going to be tough. Then again this isn't a fatal failure - it's just cosmetic for the most part.

But I'm real lazy at trying to debug it since my 300MHz scopes do have schematics available...though they're a ton harder to debug due to complexity. (I think I just rootcaused yet another problem with my DSO...)

[eccerr0r]

Re: Oscilloscope Poll! How many do you own?

HAHAHA... Not sure if people saw this yet but I just ran across it.

https://www.youtube.com/watch?v=o4YyI6_y6kw - Emulation

https://www.youtube.com/watch?v=lCIZxaAt4Wg - Tektronix Analog

https://www.youtube.com/watch?v=nYfTPVsnH14 - Rigol DSO

Funny!

Tested it on my Tektronix scopes - XY sample rate on my DSO is insufficient, but the analog shows it just fine. Funny how compression shows up as fuzziness...

(Now I want to see this working on my Eico vacuum tube oscilloscope )

[stj]

Re: Oscilloscope Poll! How many do you own?

is that crap the best you can do?

https://www.youtube.com/watch?v=lVdWxKZVYC0
kill your scope!!

[eccerr0r]

Re: Oscilloscope Poll! How many do you own?

The first sample already killed my DSO

Actually something doesn't sound right. It should be able to do 2M samples/sec/channel. Theoretically only 44.1KSa/sec should be sufficient!!!??! 2MSa/sec should be enough. However the (custom 1980s) waveform processor probably does not like plotting dots on the screen and removing the old dots fast...

[stj]

Re: Oscilloscope Poll! How many do you own?

what, a demo did?

[eccerr0r]

Re: Oscilloscope Poll! How many do you own?

No, figuratively. The scope wouldn't do it.

[diif]

Re: Oscilloscope Poll! How many do you own?

I've fancied getting a scope for a while, what do you think to this one ?
http://www.ebay.co.uk/itm/PHILIPS-PM...:qRkAAOSwjXRXZ

[eccerr0r]

Re: Oscilloscope Poll! How many do you own?

One of the probes is undercompensated

Honestly I think it all depends on what you want to do with it

I think most analog scopes are on par with each other. The distinguishing factors other than their -3db bandwidth

- XY mode, so you can watch Beams of Light or Oscillofun (or do something useful like using it like a monitor that stj does; I'm not quite so sure Lissajous figures have use anymore when you have 2 Y-channels)
- Trigger capabilities/external trigger
- Size/display size and Weight
- number of inputs. I think 2-Y channels is sufficient, plus external trigger.
- If it doesn't come with probes, make sure you get probes.

Bells and whistles:
- Z axis input, so with X and Y, you can do raster images too.
- Frequency counters and multimeters built-in. Note these are run in parallel and not computed from the waveform.
- Cursors to measure certain parts of the waveform.
- Graticule backlight and graticule embedded in CRT to prevent parallax errors.
- Dual timebase and/or Waveform Zoom
- Storage capability (yes, there are some analog scopes that have storage with a special CRT)
- and more...

Unfortunately I don't know too much about Philips, I've never used their scopes but I'm sure it's fine. A quick look says it can at least play YouScope (so it has XY input) and also has dual timebase.

I don't know if it was coincidence but I suspect most scopes are similar: my Vu-Data and Tektronix scopes are eerily similar to each other in terms of controls. Not exactly the same but have many of the same features. The Vu-Data is lacking many features of course, but has the basics.

Recently I came across a Hitachi V525 but I already have my 2 scopes (and then some) and wasn't willing to fork over $100 USD. This 50MHz scope also has XY mode alas does not have dual timebase. It does have cursor system. Unfortunately cursor systems necessarily means CPU control...

[stj]

Re: Oscilloscope Poll! How many do you own?

that seems like a lot of money for 50MHz
there was a 250MHz HP with 32chanel logic analyser the other day went for about 120

[diif]

Re: Oscilloscope Poll! How many do you own?

Thanks eccerr0r, I was thinking it might help in my fixing of laptops and other stuff.
I also like buying tools.
Maybe i'd be better of saving my money for a digital scope like a Rigol ?
Are probes universal ? It says it comes with a 1x probe.

I read that HP scopes are a little complicated to use stj and f**k knows what i'd use a logic analyzer for ?

[stj]

Re: Oscilloscope Poll! How many do you own?

probes have a maximum frequency, and often have a switchable voltage divider in them to divide by 10

over 100MHz and they get a bit expensive.
otherwise.
http://www.ebay.co.uk/itm/161843950142