Beginner scope, old analog vs. digital handheld

[tooki]

FWIW, the original Hameg probes are rebadged Testec, a nice and affordable German prone brand. I like them a lot.

[2N3055]

FWIW, the original Hameg probes are rebadged Testec, a nice and affordable German prone brand. I like them a lot.

Me too. 1+

[Jan Audio]

For what you do take a cheap old one that works good.
No need for those digital scopes.

[0culus]

Thanks, I'll check that out, as for the probes, I got two, one is a 1x-10x of this brand
https://www.globalmediapro.com/dp/A26S45/Pintek-CP-360-Scope-Probe-60MHz-pack-10-pcs/

The other probe says Pomona minipincer and does not have a resistor at all that I can see.

No specific brand recommendations, but I'd recommend getting yourself a pair of fixed 10X probes instead. Those switchable ones are ripe for a mistake down the road that might blow something up.

[Paceguy]

The Hameg you purchased is perfect for audio repairs. If later on you venture into other aspects of electronics requiring more bandwidth, you can always upgrade to something more. In audio repairs there is little danger of blowing your scope.

[Fungus]

The Hameg you purchased is perfect for audio repairs. In audio repairs there is little danger of blowing your scope.

It's the "welders" that worry me...

[DennisCA]

I've repaired old welders yes, usually it has just been a matter of replacing capacitors with new ones. Another thing that can wrong with them might be diodes or thyristors, in the types of welders I have anyway. No modern inverters. I don't really know if an oscilloscope would be of use there or not, but certainly it's a high power application. Fortunately my welders all work fine now... I have been thinking of building a pulse unit for my tig though, that's strictly a 10v affair however.

[Fungus]

The advice of only using fixed 10x probes is good advice. It can save your 'scope when the voltages get real.

[james_s]

No specific brand recommendations, but I'd recommend getting yourself a pair of fixed 10X probes instead. Those switchable ones are ripe for a mistake down the road that might blow something up.

I don't like the switchable aspect either, but the P6100 probes are common and dirt cheap and they're quite reasonably made. I have a set of them on on of my older scopes that I just glued the switches in the 10X position so I wouldn't have to worry about it. I have never once that I recall intentionally used a scope probe in 1X mode.

[DennisCA]

Great idea about the glue, I was having issues finding fixed 10x probes. Mostly 1/10x ones.

[tooki]

Great idea about the glue, I was having issues finding fixed 10x probes. Mostly 1/10x ones.

You’re in Europe so you should have no trouble getting Testec probes at a reasonable price. They have fixed 10x probes.

[DennisCA]

I was fiddling around the scope today, mostly just reading audiosignals from a player. I notice that the channel 1 input was not able to get the same kind of oscillation regardless of settings, it's as it'd diminished compared to the channel two input, I was able to get a much clearer audio signal through the 2nd channel. Is this an indication of something wrong,  Iwould have thought both inputs should be able to show the same values when adjusted the same way.

Channel two


Channel one


edit: I think the probe might also be the cause (I can change the intensity by fiddlign with the wire), need to get new ones I can trust. Probe is in 10x mode all the time.
edit2: Nah I think it's the actual input port, now I am pretty sure there's a loose contact there.

[xrunner]

It doesn't look like you have one or the other input in "VAR" mode which would be uncalibrated and allow one channel to be adjusted in amplitude. I've run across older equipment that has dirty BNC female pins. Try to clean the inside of the BNC pin with a small cleaning tool like a small piece of hard paper or pipe cleaner and alcohol.

[tunk]

... I just glued the switches ...

Or (transparent) heat shrink tube.

[DennisCA]

It doesn't look like you have one or the other input in "VAR" mode which would be uncalibrated and allow one channel to be adjusted in amplitude. I've run across older equipment that has dirty BNC female pins. Try to clean the inside of the BNC pin with a small cleaning tool like a small piece of hard paper or pipe cleaner and alcohol.

None of them where in VAR mode that I could see, and now I am without a probe, the damn connector just came apart in my hands as I removed it. So I'll need two new ones at least.

Looking at testec, but someone said I earlier IS hould matchmy probes to my input, which is 1mΩ 20pf, can't find anything that matches that exactly though, so how important is it? A Testec TT-LF-312 is 10 MΩ, 15.5 pF for instance.

[2N3055]

It doesn't look like you have one or the other input in "VAR" mode which would be uncalibrated and allow one channel to be adjusted in amplitude. I've run across older equipment that has dirty BNC female pins. Try to clean the inside of the BNC pin with a small cleaning tool like a small piece of hard paper or pipe cleaner and alcohol.

None of them where in VAR mode that I could see, and now I am without a probe, the damn connector just came apart in my hands as I removed it. So I'll need two new ones at least.

Looking at testec, but someone said I earlier IS hould matchmy probes to my input, which is 1mΩ 20pf, can't find anything that matches that exactly though, so how important is it? A Testec TT-LF-312 is 10 MΩ, 15.5 pF for instance.

Passive probe have two capacitance specs: capacitance at tip, and capacitance compensation range on the side of the scope connector (in your case 1MOhm 20 pF). The capacitance you are looking for is compensation range one and yes, Testec probes are fine.. They have good range.

You don't need anything better than Testec TT-LF-312 (for 1X/10X probe)
https://www.reichelt.com/hr/en/modular-probe-15-150-mhz-x1-x10-testec-lf-312-p32416.html?&trstct=pos_0&nbc=1
https://www.reichelt.com/hr/en/double-set-of-15-150mhz-modular-probes-testec-lf-312-2-p32420.html?&trstct=pos_1&nbc=1

OR
Testec TT-LF-212 (for 10X probe only) 
https://www.reichelt.com/hr/en/modular-probe-150-mhz-x10-testec-lf-212-p32415.html?&trstct=pos_0&nbc=1

Also maybe:

https://www.reichelt.com/hr/en/set-of-2-probe-tips-tastspitzen-p32435.html?&trstct=pos_0&nbc=1

https://www.reichelt.com/hr/en/spring-hook-for-probes-federhaken-p7644.html?&trstct=pos_1&nbc=1

these get damaged and displaced so few spares are not bad to have.

P.S. also look at https://www.batterfly.com/shop/en?route=product/search&search=TESTEC they have good choice and prices.

best,

[james_s]

Try using the built in probe compensation calibrator, at least I assume it has one. Connect both probes to that and set both channels the same, you should see the same square wave on both. You could also get a cheap function generator and use that to play around, you'll probably want one of those anyway for working with audio circuits.

[Wallace Gasiewicz]

I agree with the other comments about 1X 10X probes. I really do not like the 1X 10X probes,they can cause problems if you unintentionally have them set at 1X, Sometimes the switch can go wonky also. In general they do not work as well as unswitched probes, maybe stray capacitance?

I spent years with inadequate probes that did not match the scopes I was using. In retrospect, that was stupid.  At the really cheap prices that are common today there is little reason not to get the correct probes. Usually good to get probes that are rated higher than your scope. since your scope is 40 MHz this should not be a problem. You do have a calibrator connector just under the screen for calibrating your new probes. Should be nice square wave.The BNC connector part of the probe should have an adjustment (really just an adjustable cap) that is used to make the wave square. This is what "matches" the capacitance of the probe with the input capacitance of the scope.

About max freq....in analog scopes this is usually the frequency where the trace is 80% of what is should be. The scope can go higher, sometimes much higher, but the amplitude of the trace will not be accurate. Sometimes there is a "hole" in the freq range just above the Max where the scope has low response then maybe the scope gets back on track with even higher freq.

That is a real nice scope. Much more than a "beginner" scope.
Don't clean the surface with any solvents, could erase the lettering, use soap if necessary

[james_s]

Don't clean the surface with any solvents, could erase the lettering, use soap if necessary

I learned that the hard way with a Tek 2215 that was filthy. I washed the knobs in warm soapy water and they cleaned up beautifully, all the grime came right off, as did all of the printing on the transparent portion. 

This scope doesn't appear to have anything like that though, just a screen printed vinyl overlay, those are pretty durable as long as you don't use any harsh solvents. I often use Windex or Oil Eater to clean off stubborn grunge but this one already looks clean.

[0culus]

Don't clean the surface with any solvents, could erase the lettering, use soap if necessary

I learned that the hard way with a Tek 2215 that was filthy. I washed the knobs in warm soapy water and they cleaned up beautifully, all the grime came right off, as did all of the printing on the transparent portion. 

This scope doesn't appear to have anything like that though, just a screen printed vinyl overlay, those are pretty durable as long as you don't use any harsh solvents. I often use Windex or Oil Eater to clean off stubborn grunge but this one already looks clean.

Ever had to deal with super duper permanent marker? I am in the middle of repairing a Tek Type 575 that someone wrote on (probably an auctioneer; fortunately on one of the side panels) with one of those ultra super duper permanent Sharpies. The only thing that would touch it was acetone. Took off some paint too, but not all of it, and it looks a damn sight better than the huge ugly handwriting. 

[james_s]

I've had reasonable luck removing permanent marker using that magic eraser melamine foam stuff. Sometimes it helps to moisten it with rubbing alcohol.

[DennisCA]

Hello again, today my new probes arrived so I could test the scope. I used the 1khz signal generated by the scope itself. And it does seem there is something wrong with channel 1.

This is channel 2, I tuned both probes capacitance on channel two:


Channel 1, not able to get anywhere near even with 20mv on the volts/div knob


On channel 1 I am not able to tune the capacitance to get flat square wave either. Signal seems both weaker and wrong. I am suspecting, well hoping that it's a bad connection to the BNC connector on front.

I suppose the next step is to open it up and have a look near the ch.1 connector....

[TimFox]

Ch 1 response looks exactly like a broken connection to the input circuitry, with only a small capacitance between the signal and the high-Z (1 megohm) input.  If that BNC is a PCB-mount right-angle BNC, excess leverage against it in the past may have broken the solder joint between the "hot" pin and the PCB.

[james_s]

I was going to say that looks like the input is very loosely AC coupled, but I see Tim said what is effectively exactly the same thing. It looks like the channel is mostly working just fine, but the path is broken somewhere near the input and capacitively coupling.

[nfmax]

Check the AC/DC switch contacts - that signal could be capacitatively coupled through a layer of dirt