Anyone familiar with the Fluke 'CombiScope'?

[EBR]

Hello all,

I am relatively new to the world of electronics so please bear with me. I have recently acquired an older Fluke PM3394B CombiScope which is supposed to be both a digital and analogue scope in one. While in the process of learning how to use it I would like to verify that all aspects work as they should. Everything for the most part seems to be working like the auto adjust, timebase, trigger etc. but the probe switch (or range indicator) for attenuation range seems a bit suspect (it is supposed to set the ampl/div reading by 10x or so the probe manual states). With the probe connected to the calibration terminal, the proper square wave is displayed and when I press and hold the 'range indicator' button, the square wave turns to a line and returns to the prior square wave when the button is released acting like a momentary pushbutton only. In my mind this is not really serving the intended purpose as no setting actually changes. The probe used is a PM9010/292 with the command button (which works)

Another potential issue is when in digital mode, there seems to be some sort of interference? or noise present in the signal. The displayed waveform looks noisy (for the lack of a better word). In analogue mode, the displayed waveform is very clean looking. I really dont know if this is normal or not. Other than these two issues, it seems like a relatively capable scope...

 I would greatly appreciate any advice or expertise anyone hast to offer in the matter. Thanks.

[Jay_Diddy_B]

EBR,

The Fluke/Philips combiscopes were quite handy. You could switch between an analog scope and a DSO with a button push. Tektronix also made some similar scopes. The Tektronix popular Tektronix models were 2230 and 2232.

These were handy for capturing non-repetitive events in the DSO mode.

The downside to these scopes today is the relatively low sampling rates, The Tektronix 2230 was 20 MSps and the Tek 2232 100MSps. The Philips were similar, the very best one was 200 MSps.

The PM3394B is one of the better ones at 200MHz and 200 MSps

There will be some noise in the DSO mode. This a reflection of the ADC converter used in the scope.

It comes down to your application and the price as to whether this is a good scope for you.

Jay_Diddy_B

[free_electron]

The noise in digital mode is normal. these scopes use a CCD (not a CCD as in a camera , but a sequential analog memory called a chrage coupled device , essentially a bucket brigade )
They fill the CCD fast and then digitze it slow using a cheap a/d

are oyu sure the probe you have is for the scope ? it should have a thrid 'ring' that touches the little pin to the left or right of the BNC. that is the command pin. the scope can read the attenuation by measuring a resistor that sits between that pin and ground. when you push the command button that resistance changes and that is how the scope 'sees' what you do.

[grumpydoc]

The noise in digital mode is normal. these scopes use a CCD (not a CCD as in a camera , but a sequential analog memory called a chrage coupled device , essentially a bucket brigade )
They fill the CCD fast and then digitze it slow using a cheap a/d

I don't think that's right. The Tek 2430 had a CCD but the Philips CombiScopes - certainly the 338x and 339x 'scopes had a 200MS/s ADC and didn't use at CCD.

Also I don't think it's fair to say "They fill the CCD fast and then digitze it slow using a cheap a/d" because that implies intentional cost cutting/crappy design - at the time the fastest high ADCs were not all that fast so the CCD approach was a perfectly reasonable approach to getting enough bandwidth. It's not as if these were "low end" 'scopes when they were first sold.

I have a PM3382 which is the 100MHz 2+2 channel member of the family and it's my main 'scope. Perfectly OK in analogue mode and while the digital side is limited it does have its uses.

[EBR]

Thanks for the response,

Based on the replies and further research, it seems like this scope is working just fine. The probes are the correct pm9010 '100mhz'  and pm9020 '200mhz' (which I have recently obtained) with the additional ring for the command feature (which works nicely). The attenuation is automatic; when a probe is connected to the scope, it automatically detects if it is 10:1, 1:1 etc. the second button with the symbol of an inverted 't' (above the command button) I am still not fully certain what it does but while playing around with settings I noticed it changed the timebase when repeatedly pressed but then snaps back to the initial setting. Occasionally it will accept a new setting but I personally think this development is too erratic to to state with certainty that this is what that button is for.

[Retep]

I have got a Fluke PM3384A with exactly the same problem; in analog mode the signals look perfectly clean, while in digital mode the signals look noisy on all 4 channels even when the channels are set to GND. The attenuator has no affect on the noise in digital mode. If I use 'VERT MAGNIFY' it appears to be LSB noise, but somehow this noise appears to be much more visible compared to the older Hameg HM-408 scope I have in digital mode.

When I got the Hameg HM-408 scope is had a similar but worse issue; in digital mode it was all over the place. That turned out to be caused by a SMD capacitor in the power supply that decided to continue its life as a resistor. I haven't really seriously looked at the Fluke scope yet, but I kinda hope it can do at least as well in digital mode as the older, more primitive and lower end Hameg.

(BTW: looking at the service manual of the Fluke it appears that indeed there is no CCD before the ADC).

[egonotto]

Hello,

in digital mode my scope has noise less then 0.3 DIV p-p in 2mV  mode and less 0.2 DIV p-p in 5mV and above by open input. I think this is pretty good.

Best Regards
egonotto

[Retep]

Personally I would find 0.3 DIV of noise a bit too much. On my Fluke Combiscope I see about 0.1 DIV of noise regardless of the attenuator setting. I can live with it for most uses, but it is a bit too much to see if the signal is clean or not.

On the Hameg scope HM-408 I also have there is hardly any visible difference between analog and digital mode; if you look closely you could see steps in digital mode, and occasionally a sample that on LSB higher than surrounding samples.

I was considering to sell the Hameg scope, but at this point I'm in doubt. The Fluke Combiscope has significantly better specs and features, and last but not least 4 instead of 2 channels (the main reason why bought it), but I don't like the fan noise, the use of buttons where most scopes use knobs, the menu system and it rather sluggish response when you rotate the knobs. I find the Hameg more pleasant to use, even though its user interface has a few annoying quirks of its own.

[kripton2035]

but the probe switch (or range indicator) for attenuation range seems a bit suspect (it is supposed to set the ampl/div reading by 10x or so the probe manual states). With the probe connected to the calibration terminal, the proper square wave is displayed and when I press and hold the 'range indicator' button, the square wave turns to a line and returns to the prior square wave when the button is released acting like a momentary pushbutton only. In my mind this is not really serving the intended purpose as no setting actually changes. The probe used is a PM9010/292 with the command button (which works)

 I would greatly appreciate any advice or expertise anyone hast to offer in the matter. Thanks.

Hi,
press the "utility" button, then choose "probe"
then on the second button you can choose the probe's button action :
either autoset, or setup or quick measure
check between these to suit what you want to do with the probe button.
hope this helps.

[ddavidebor]

I've one of this scope and is broken.

When i turn it on it beeps continuously and nothing happens. Only the grid retroillumination and a led is on.

All the power line are ok...

[Retep]

In case you don't already have it; you can find the service manual here:
http://elektrotanya.com/?q=showresult&what=pm3384a&kategoria=&kat2=all

[ChrisG]

Hi and hello, there are here and there still Philips PM3384's on the 2nd hand websites. I've now bumped into one for 275€. As we're in 2017 and more cheap DSO's are becoming available I would assume that this is not a steal and it would need to be carefully checked and verified. Any feedback from you guys on yes/no buying such a combi-scope?

[kripton2035]

if you're doing analog stuff, and in the high range of the bandwith, the combiscope is better
if you want to do digital stuff, a ds1054z hacked to 100MHz will surely be better than the combiscope.

[grumpydoc]

Upfront I'll admit to quite liking these 'scopes.

A good condition, fully working, PM3384 is definitely worth 275€, however you really want the PM3394B.

However as you should be able to pick up an entry level Rigol for 300-400€ I am not sure that I would recommend the Phillips as a first 'scope.

A Rigol DS1052E smaller, lighter, less power hungry, has a higher sample rate, way deeper sample memories and can be hacked for higher bandwidth (if you don't mind loosing the warranty).

If you do go for the Phillips make sure it passes its autocal - if it does it will still pretty much be in spec and they are nice 'scopes to use.

[HighVoltage]

For me, I do not only like these scopes, I love them! And on my high voltage bench I only use these scopes as PM3394B models with all options.

If it is just a PM3384 I would stay away, they are too old by now and had a few hardware problems. (Original Fluke View Software will not work)

If it is a PM3384A, (First major revision), may be, what options are installed? (Original Fluke View Software will sometimes work, very flaky)

If it is a PM3384B, that passes all test procedures, go for it.
- best even having extra memory and
- math option installed
On this one, the original Fluke View Software will not work perfectly
Make sure when the scope is warmed up, that the trace has no offset from the ground reference in ANALOG and DIGITAL mode.
After at least 10 min warmup run a self calibration with the CAL push button and check the trace again to be on the ground reference in both modes.

[macboy]

Thanks for the response,

Based on the replies and further research, it seems like this scope is working just fine. The probes are the correct pm9010 '100mhz'  and pm9020 '200mhz' (which I have recently obtained) with the additional ring for the command feature (which works nicely). The attenuation is automatic; when a probe is connected to the scope, it automatically detects if it is 10:1, 1:1 etc. the second button with the symbol of an inverted 't' (above the command button) I am still not fully certain what it does but while playing around with settings I noticed it changed the timebase when repeatedly pressed but then snaps back to the initial setting. Occasionally it will accept a new setting but I personally think this development is too erratic to to state with certainty that this is what that button is for.

I think that is a ground button. When making DC coupled measurements in particular, it lets you see the ground reference. Also when doing low level AC measurements, it can let you see the amount of noise picked up by the probe (as opposed to noise in your signal).

[HighVoltage]

I think that is a ground button. When making DC coupled measurements in particular, it lets you see the ground reference. Also when doing low level AC measurements, it can let you see the amount of noise picked up by the probe (as opposed to noise in your signal).

I forgot to answer that.
yes, macboy is right, the first switch is a ground button.
The second switch (command) can be programmed under:
[UTILITIES]
[PROBE]
See picture ...

[ChrisG]

Thank you all for the feedback. As I'm already the happy and proud owner of a DS1054Z hacked to 100Mhz I'll not add more clutter to my desk space.