Fixing the MHS-5200A

Just a few simple modifications to the MHS5200A function generator can significantly improve sine wave harmonic distortion and square wave ringing/overshoot. Detailed photos/descriptions of the mods can be found at: www.analogzoo.c...

[@ebrewste]

Great video! Not only did you cover a lot of good material, you weren't a jerk about the original product design mistakes. It makes the video very enjoyable to watch.

[@Analogzoo]

+ebrewste Thanks! I don't design function generators and who knows what constraints they were under, so I'm not one to judge. Besides, it made for a fun project!

[@Robbie1949]

Just bought a new MHS-5225A function generator to service tape decks. I have a HP 3325A but that is on the other bench and I needed something small with the frequency very xtal stable and able to output a seasonable facsimile of a sinewave with amplitude down to 20 mV. I originally had the FY3224 but it's output at 20 mV is not usable. The 5225A generator is now 12 bit instead of 8 and I will do the mods of changing the op amps but I will only use sine waves so not the filter. I am a tech of 40 odd years experience with the RAAF as well as some civilian experience with camcorder micro miniature repair. By the way to our UK people the THS3092 are available from Element 14 (formally Farnell) for $5.20 plus 10% GST Australian and small change in quantities of 10 or more, also free shipping if you spend over $45. In the UK everything seems to be bloody expensive it seems to me, even the Fish & chips.

[@Petex90]

Keep up the good work! That was quite decent MHS-5200A video series :)

[@Analogzoo]

+Petex90 Thank you, will do! :)

[@TychusAlfa]

just... beautiful :D

[@borayurt66]

Good job, great explaining of the job done too. I envy the way you solder/desolder smd parts like putting together lego bricks. You've got one more follower :-)

[@ManuelMcLure]

Thanks for this video! I've got one of these on its way to me and I think I'll do the "lazy" fix (i.e. remove the resistors) at the very least. I like the fact that it seems to have no real effect on the harmonics and is easy and extra-cheap. Perhaps later I'll look at doing the Bessel filter and/or op-amp replacement.

[@rsattahip]

Interesting video, Guess they can't put the Texas Instruments chip in it and still sell it for $63. Interesting video, wish I could understand it better. A function generator at this price is certainly more for learning than serious laboratory use.The current generation of inexpensive Chinese equipment allows hobbyists and students to have reasonably working devices they never could before.

[@PapasDino]

New subscriber here too! Do you find that wearing glasses impacts on your use of the AmScope? I've thought about getting one for a long time but didn't want to have to take my specs on and off to use it for long sessions (read that as old eyes!). 73 - Dino KL0S

[@Analogzoo]

+Dino Papas Thanks! I do sometimes take my glasses off when using the AmScope, but really it's not a problem - I just have to adjust the angle I look into the eyepiece a bit, since the glasses add a little more distance between me and the eyepiece. It's quite a nice piece of equipment to have around for SMD stuff!

[@dwDragon88]

Nice job. Also, that's a great book there. The filters chapter is a go-to reference, even with the easy online calculators available. It's good to know where the numbers come from. Did you think about trying a Butterworth filter? Each type is going to be a trade-off of course, but maybe you can find a slightly better combination of roll-off and phase response.

[@Analogzoo]

+dwDragon88 I'd expect that a Butterworth would certainly split the difference in performance between the elliptic and Bessel filters, and I did almost try a Butterworth, but I was pretty happy with how the Bessel turned out so I got lazy and just left it at that. :) And yes, I do love that book!

[@dwDragon88]

+devttys0 What you have is pretty good, plus a Butterworth or Chebyshev (yikes) would really roll the edges of those square waves at higher frequencies. What you have may well be the best compromise.

[@ohmedarick1]

Thank you Great hands on and theory...

[@EmbSysDev]

Nice work , Sir!!

[@breedj1]

Thanks for figuring out. I'll do the same modifications. I subscribed to your channel as well.

[@twobob]

top job

[@galileo_rs]

I considered buying these a few months ago. Your modifications make it much more usable. Could you test the performance (accuracy) of a frequency counter? Although a frequency counter is something that I rarely need it would be nice to have one that's fairly accurate.

[@Analogzoo]

+Dragan Milivojević To be honest I haven't played with the frequency counter on it at all yet, but that might make a good follow up video!

[@Mr_Meowingtons]

with adding the THS3092 can't we just cut some traces and add a circuit to add the +/-15v? there is a lot of room in that case

[@imjm17]

You've gained a subscriber. Thanks!

[@Analogzoo]

+mchamster Much appreciated!

[@ardhendusekhardas4302]

you got a new subscriber & thanks for the great video ....

[@DoRC]

how does the square wave look at higher frequencies?

[@bloguetronica]

I wonder if that Bessel filter doesn't start to attenuate too soon. How does it behave for the higher frequencies?

[@DeeegerD]

Nice! When my gen arrives I will give it a whirl - last time I worked with surface mount I burned my finger lol.

[@Analogzoo]

+Digger D If I had a penny for every time I burned myself on the soldering iron...well, I suppose I could probably buy myself a coke. :P

[@breedj1]

+Digger D If you work with smd often it might be an idea to buy a cheap hot air gun and some solder paste. Just clean the pads with litze after desoldering with the hot air gun and then apply a little paste. Place the component and use the hot air gun to solder. Works very well.

[@markm1862]

+Digger D hot air gun works best for smd, but unless the nearby components are covered with high heat tape or some cover, the small nearby components sometimes fly off. There is another method I use when I don't have hot air, just put a bunch of solder and make all the pins on each side of chip cover with a large ball of solder, if I am quick, I can heat up both side of the multi-leg chip the same time and can pull out the chip before the solder hardens (sometimes I use 2 solder tips one on each side). then clean up the pads and solder the new chip.

[@DeeegerD]

Never did do the mod as the op amps were too expensive at $17 each (Cdn).

[@winstonsmith478]

What book is that which you show with the bandpass filter design table in it?

[@vincei4252]

If I'm not mistaken the book is RF Circuit Design by Boswick. www.amazon.com/Circuit-Design-Second-Christopher-Bowick/dp/0750685182

[@lsaavedr]

gracias por existir!

[@leejones9827]

In your previous video you recommended not buying the MHS-5200A and instead saving up for a second hand branded model. Do these fixes change your perception at all?

[@Analogzoo]

+Lee Jones With the mods, I think it is much more viable as a useful lab tool. I still don't think that it's good as a primary signal source, as there are still other problems with it (e.g., square wave jitter), and I'm sure there are more, undisclosed issues. If you don't have a good signal source already, my opinion is that it's better to get a used unit from a reputable vendor. With that said, I've already found it useful for basic circuit tests around the lab, especially when I need two phase-locked signal sources (my HP function gen only has one output), so it's still a good bang for the buck!

[@leejones9827]

+devttys0 Basic circuit tests around the lab is all I'm after at present. If my interest in analogue electronics percolates, and a more expensive function generator is required in the future, I'll invest further down the line. For now I think I'll purchase one of these and make the mods (which is a fun project it its own right), keeping the knowledge that it's not perfect in the forefront of my mind. Thanks for your good work and replies.

[@lndeo]

What is Rigol FFT-analiser are you used in this video?

[@nathanhaltman7235]

+devttys0 Nice video. I was curious to know the title of the reference book you used with the filter tables.

[@Analogzoo]

+Nathan Haltman RF Circuit Design by Chris Bowick. Highly recommended! www.amazon.com/RF-Circuit-Design-Second-Edition/dp/0750685182

[@pa3eka]

THS3092DDA THS3092D THS3092 SOP8 Is this the good replacement

[@willwasson8113]

Hello, If you still monitor this page I have a question about the sweep function. Can both channels sweep at the same time? I would like to have a frequency sweep on 1 channel and a voltage sweep on the other one to do filter sweeps. Setting an Oscilloscope into X/Y mode I could draw filter curves if the generator could do this. Of course if you did a video of this it would be great!

[@Analogzoo]

+Will Wasson Hmmm, I'm not sure if you can do that via the front panel controls or not, but I'm sure you could do it via the serial port interface.

[@willwasson8113]

Thanks! I've looked at the documents for the serial interface that was posted on the web and I see only single start and stop registers. Maybe they link both channels :-) BTW thank you for posting how to upgrade this unit. I going to buy one and order the parts for the upgrade from Digikey at the same time.

[@Analogzoo]

+Will Wasson Yeah, you'd have to write a program/script to manually update the frequency and amplitude. Since all the commands are ASCII sent over serial though, that shouldn't be too bad to implement.

[@a.asperga2036]

do you have other link? link is dead

[@markm1862]

Can you please make a video on how to use a function generator with oscilloscope to troubleshoot a pcb with chips (motherboard or any other)?

[@Analogzoo]

+Mark M Do you have something specific in mind? Or just general cases where a generator & 'scope are useful for troubleshooting?

[@markm1862]

+devttys0 nothing specific, I was thinking more on how to set up a scope with function generator to troubleshoot a broken tv/any powersupply/sound amplifier/inverter/telephone etc. What oscilloscope X probe, attenuator to use not to burn up the scope. Also on the mhs5200a repair link picture & video you showed ch1 repair only, if you can add a picture with both channel repair it would be helpful. I don't understand 'under ch2 filter picture' what you mean by 'lazy mod' when you just repaired the ch1 only?

[@Analogzoo]

+Mark M Well the reason I ask is that a scope and function generator aren't always the right tools for troubleshooting! A good example of when they are useful is the MHS5200, where I isolated different amplifiers in the signal chain, injected a test input signal from my known good Agilent function generator and looked at the output with the scope. But for other parts of the circuit a spectrum analyzer, logic analyzer, or multimeter would have been more appropriate, depending on what needs troubleshooting. If you want more info on using scopes in general (and not blowing them up!), I'd start by watching the excellent videos by @w2aew and @eevblog (I don't think I can explain it better than them!); here's a few to get you going: kzbin.info/www/bejne/iYmXeXqEjKeYa68, kzbin.info/www/bejne/rpKofaR3pJmeobM, kzbin.info/www/bejne/bouufqWwiayrgrM The MHA5200 channel 1 and channel 2 mods are identical, so I only showed channel 1 in the video, but I modified both channels. The filters for each channel are highlighted in the pictures on my blog. The "lazy mod" I refer to in the pictures is to just remove the top 3 capacitors in each filter, instead of replacing the filter entirely; those three capacitors are highlighted in the unmodified channel 2 picture, and the unmodified channel 1 filter would look identical.

[@markm1862]

+devttys0 cool, thank you :)

[@nplanel]

All good, Fixing :) is always better than just saying this is not good ! My 2 cents : Even if your video talk about it (briefly), I think you should talk more deeply about filter performance between the elliptic and Bessel filter, (phase, noise margin, orders, ...) and others like Butterworth Basically testing via S-parameter, why phase shift is important (square = sum sin, ...), harmonic, ... You could show/use QUCS; Pretty good Spice and more simulator, and much better than the LTSpice interface And of course opensource :) qucs.sourceforge.net/download.html 1st Read (even briefly) the excelent Get Started : qucs.sourceforge.net/docs/tutorial/getstarted.pdf Thanks for the videos

[@Analogzoo]

+np I agree, but I didn't want to get too deep into filter design, since that probably deserves a video by itself. I haven't used QUCS before, I'll have to check it out! I have used the Experimental Methods in RF Design software for filter design before, and quite liked it.

[@lndeo]

cooool! in Russian U don't find any like this review

[@cheapmod]

Worder how malaysian people just looking for tutorial pakai hijab n modified y15 till the day of their death.

[@azzym8794]

IT was nearly useless. Your "better" op amp did not do zilch.