1st scope purchase

[nemo000111]

Hi all.  I've settled on the Rigol DS1074Z for my 1st scope purchase.  The part I'm stuck on is the function generator.  I don't currently have one and don't have a need for it yet.  I haven't priced them out, so I'm not sure if I'm better off not getting it now and getting a stand alone later or not.  This is mostly for lower end hobby stuff and repairs.  Also, doesn't anybody know if the unknown licensed feature is the function gen and you just need to put the connectors and button on?

[linux-works]

save the money and get an external one.

there are so many out there, used, at good prices.  no need to bundle it with the scope.

the scope one is high speed, but limited functionality, overall.

[tom66]

The -S option comes with additional hardware - I believe a daughterboard for the sig-gen.
You would be better served by an external sig-gen.

The DS1074Z is a great scope overall, I personally picked it after carefully weighing between DS2000 and DS1000Z - the extra two channels make up for the slightly poorer performance and a few less features. The intensity graded display works really well, better than expected.

[jdoshier]

Equipment manufacturers are moving towards highly integrated instruments so you're going to see more with scope, DMM, signal gen and spectrum analyzers built in.  It's a good thing if it saves money and you need the features in one unit.

I have DS2000A-S and DS1000Z-S scopes and am not impressed with the signal generators, but mostly from the arbitrary wave function.  DS1000Z firmware 00.02.03.SP5 allows you to load a wave from Rigol's Ultra Station software, but only to source 1.  From there, you can store it locally and load into source 2.  DS2000 firmware 00.02.01.00.03 works similarly, but the newer 00.03.00.00.00 firmware doesn't allow loading an arb waveform at all.  The signal generator section is poorly documented in the programming manual and appears to be a partial implementation of the DG1000Z. Pretty much tells me the waveform generator is not getting the software support it needs.

In general, Rigol has poor software QA and spotty tech support, so I will stay away from the internal sig gen's in the future.  Their standalone generators are pretty solid, though.       

[miguelvp]

External one is the key, AM/FM modulation a must in my book.

I'm myself waiting to get one since my 2nd (or 3rd) hand Tektronix FG-504 40 MHz Function generator gave up the magic smoke

But it will be nice to get one of the new ones with ARB waveforms.

[linux-works]

I'm thinking of getting an fg504.  how did you like yours?  are you going to repair it?  they don't use special parts, do they?

[MarkL]

I'm thinking of getting an fg504.  how did you like yours?  are you going to repair it?  they don't use special parts, do they?

The FG504 uses a few special parts, but the vast majority is standard stuff.  The parts list is in the service manual:

http://bama.edebris.com/manuals/tek/fg504/

In my FG504 over the years, I replaced a tantalum cap (on fire!), a diode, a transistor, and an internal fuse.  When I got it, the main output transistors had to be glued back onto their heatsinks, and all pots needed serious cleaning.  Some of the pots are still a little crunchy, but everything works.

It's all analog and it has lots of knobs so all adjustments are instantly accessible.  A nice a little unit when you want a signal quickly and it doesn't have to be ultra-precise or ultra-stable.

[miguelvp]

I'm thinking of getting an fg504.  how did you like yours?  are you going to repair it?  they don't use special parts, do they?

Long story short, the transistor on the backplane (TM503) decided to give up letting all the voltage through and took out a bunch of stuff including a on board fuse. I found a replacement fuse but decided to attack the PNP first, the problem is that I couldn't the real thing 151-0373-00 which is an MJE2901, So I got a cheap Chinese replacement transistor MJE2955. I did put a temporary fuse 1.5Amp fuse solder to two terminals on the board. I did check the transistors and they were good and while testing the voltage for the +15 that was failing and that took the fuse, it was reading around 15V but  I smelled that particular scent that something was burning up somewhere so I shut it down.

So the repair its on hold until I can find the time to deal with it further. I don't trust those transistors I got, and I can get original replacement parts, I also have the board fuse (GFA 1 1/2 yellow purple) identified so, now I just need time to fix it.

It's a great function gen, even used they cost a pretty penny even now. And for old equipment is not too bulky.

If you find one, the full manual can be obtained from:
http://bama.edebris.com/manuals/tek/fg504/
among other hard to find manuals.
http://bama.edebris.com/manuals/

Edit: MarkL, what enclosure do you have on yours?

[EEVblog]

How much is the option? and what can you get for the same price?
Likely better value is to be had with a separate unit, the internal ones you pay a premium for less, and you are buying the convenience.

[miguelvp]

MarkL, or any other FG504 owner.

If you ever have problems with your the +15V and -15V part of the circuitry, here is an LTSpice model I did to track down the problem.

I'm not using all of the real part numbers but I think I labeled all of them right.
And I had to change R1707 on the sim to 8K instead of 7.5K because I couldn't get the right voltage.
I didn't know how to do the adjustable trim pots so I put two resistors centered tap to get the right voltages.

It's probably one of my first LTspice attempts to simulate a real circuit, so I might have goofed.

[MarkL]

Edit: MarkL, what enclosure do you have on yours?

I have mine in a TM503, like yours.

Thanks for the spice model!

[MarkL]

How much is the option? and what can you get for the same price?
Likely better value is to be had with a separate unit, the internal ones you pay a premium for less, and you are buying the convenience.

I paid $650 for mine 20 years ago in used, but like new condition.

I don't think I'd pay much more than $75 for one now; maybe a little more if it was fully guaranteed and cal'd.  And only if I already had the mainframe.

But if mine broke, and the "fix it" challenge failed, I probably wouldn't replace it with another FG504.  I only have it because it keeps being easy to fix and it does come in handy sometimes.  I have other gen options available to me.

I also don't like to admit it's related to my THS condition (test-equipment hoarder syndrome).

[miguelvp]

I think Dave was talking about the OP's Rigol DS1074Z and the -S option.

The DS1074Z-S costs $818, the DS1074Z $585, so you are paying $233 for the -S option that is a limited function gen that offers 2 channels at "at most" 25 MHz source.

The specs for the signal source are:

Code: [Select]

Sample rate:         200 MSa/s
Vertical resolution: 14 bits
Highest Frequency:   25 MHz
Standard Waveform:   Sine, Square, Pulse, Triangle, Noise, DC
Arbitrary Waveform:  Since, Exp.Rise, EXP.Fall, ECG, Gauss, Lorentz, Haversine
Sine                 Frequency Range              0.1 Hz to 25 MHz
                     Flatness                     ±0.5 dB (relative to 1 kHz)
                     Harmonic Distortion          -40 dBc
                     Stray (Non-Harmonic)         -40 dBc
                     Total Harmonic Distortion    1%
                     Signal-to-Noise ration       0 dB
Square/Pulse         Frequency Range              0.1 Hz to 15 MHz
                     Rise/Fall time               <15 ns
                     Overshoot                    <5%
                     Duty Cycle                   10% to 90%
                     Duty Cycle  Resolution       1% to 10 ns (select the greater one)
                     Minimum Pulse Width   20 ns
                     Pulse Width Resolution       10 ns or 5 bits (select the greater one)
                     Jitter                       500 ps
Triangle             Frequency Range              0.1 Hz to 100 kHz
                     Linearity                    1%
                     Symmetry                     0 to 100%
Noise [1]            Bandwidth                    25 MHz

Internal Generated
waveforms            Frequency Range              0.1 Hz to 1 MHz
Arbitrary Waveforms  Frequency Range              0.1 Hz to 10 MHz
                     Waveform Length              2 to 16k pts
Frequency            Accuracy                     100 ppm (lower than 10 kHz)
                                                  50 ppm (greater than 10 kHz)
                     Resolution                   0.1 Hz or 4 bit, select the greater one
Amplitude            Output Range                 20 mVpp to 5 Vpp, High-resistance
                                                  10 mVpp to 2.5 Vpp, 50 ?
                     Resolution                   100 ?V or 3 bit, select the greater one
                     Accuracy                     2% (1 kHz)
DC Offset            Range                        ±2.5 V, High-resistance
                                                  ±1.25 V, 50 ?
                     Resolution                   100 ?V or 3 bit, select the greater one
                     Accuracy                     2% (1 kHz)
Sorry if it doesn't line up hard to align those specs.

So you are getting a signal gen for $233 but can't do amplitude or frequency modulation and even if it can handle ARB waveforms they are limited to 10MHz.

For the price well don't know but I bet you can find some used equipment that will surpass that at the price point, and unless you are crammed for space it's better to get a separate unit.