FY6600 Function Generator Power Supply Replacement

Рет қаралды 13,962

5 жыл бұрын

In the first video I discussed the problem of the cheap switch mode power supply in the otherwise very useful Feeltech FY6600 function generator which puts stray voltages in the 100V range on the output terminals. That video suggested a temporary fix to get rid of the worst but not all problems. That video is at
• Home Lab Equipment: Ex...
This video is the promised continuation where I finally replaced the power supply with one that uses ready DC-2-DC converters from eBay and Banggood.
The parts used are:
- Rectifier: KBP307G (any full bridge rectifier for 40V, 1A or more will do)
- Smoothing caps: 2x 2200uF 35V
- Filter caps (in the AC part): all 0.1uF
- for the dual +-12V DC-2-DC converter search eBay for "TPS5430 Positive Negative Dual Switching Power Supply Module"
- for the 5V DC-2-DC converter I used Banggood ID 923600 "Geekcreit 5A XL4005 DC-DC adjustable step down module"
- for the fan controller search eBay for "DC12V 1A Automatic Fan Temperature Control Speed Controller Governor"
- for the LC filter, I used Banggood ID 1029694 (3PCs L-C Power Filter-2A RTF) note this ID is for 3 filters but in the end I used only one. They also sell just one under a different ID
- the fan is an ordinary 40mm 12V fan with two leads which I already had.

Пікірлер: 41

@DaruoshAghajaney 5 жыл бұрын

Thanks for the deep analysis and the efforts you put into making this video. The video on it own, is a very nice explanation of building a simple multi-rail power supply.

@noakeswalker 5 жыл бұрын

A comprehensive final fix to the problem ! You may have got away without the fan controller, just to save some complication and possible e-noise, though more mechanical noise of course..... great to see all the plots for the full story too.

@vidasvv 3 жыл бұрын

Great video ! Function gen, $100, Engineering time $2000.

@ovi_4 5 жыл бұрын

Nice solution to a quite good signal generator. I.ve got one myself and now will try to implement this mod. Tnx.

@simonstuartmurray 2 жыл бұрын

Hi TheHWcave and thanks for these helpful videos. I believe that the power supply in my FY8300 is identical and that it has cooked one or both of the diodes on the output side of the transformer. Following your approach, I've ordered a +/12v converter and a 5v converter to use with a 15.6v mains transformer, rectifier and capacitor that I already have. While I wait out the long, long shipping times on these, I realized that I had a box full of old 100v - 240v AC to 5v and 12v wall plug adapters (switching type) and that I should be able to combine two 12v adapters and one 5v adapter to make up a +/- 12v , 5v supply which should get my FY8300 going again in the interim I'll report back shortly how this all went .... Simon

@TheHWcave 2 жыл бұрын

yes, please report how you are getting on. But I must warn you of using unknown switch-mode power supplies (SMPS), especially cheap ones. Their electrical safety is often very questionable and they are practically guaranteed to leak a lot (comparatively) of mains current into your generator and through the outputs into the circuits that it connects to. With the original SMPS in my FY66000 I measured somewhere around 90VAC on the generator output against earth. If you are planning to use normal SMPS, you are pretty much forced to connect the outer BNCs shells (signal ground) to mains earth to get rid of the stray voltage cause by leaks but then the generator signal will be always mains earth referenced which is something l tried to avoid. You can buy low-leak SMPS (meant for medical applications) where you can live with the tiny remaining leak current but they cost quite a bit more and are harder to find.

@simonstuartmurray 2 жыл бұрын

@@TheHWcave It works just fine. It was simple to set up - just connected the + and - of two 12v SWPS to ground and the - of a 5v SWPS to ground and wired in the 12v+, 12v- and 5v+ to the sig gen board. At least I've got my sig gen back, while I wait for the +/- 12v and 5v converters. I had to ground the sig gen to earth for safety and to get rid of the elevated terminals (my selection of available SWPS varied from 80v to 110v AC to earth, on both + and - sides), so I'm not isolated until my new parts come. Thanks, Simon :-)

@TheHWcave 2 жыл бұрын

@@simonstuartmurray Thanks for the update. I am glad it works for now.

@scarpia519 2 жыл бұрын

The Feel Tech website (September 2021) shows the rear panel of the FY6900 (User Guide, page -11) with a three prong AC connector. Apparently, they have corrected this issue with the method described in this video or something similar.

@TheHWcave 2 жыл бұрын

Yes, its the cheapest way to get rid of those stray output voltages. But on the other hand , I'd rather avoid (well, greatly reduce) them by using a better power supply and keep the outputs floating. I can always earth them with an external wire if I really need to get rid of the last bit of stray voltage against ground. I am pretty happy with the new power supply and did not have to use earthing the outputs for ages

@carlosagorreta5276 5 жыл бұрын

Really good video!

@flemming2jacobsen911 5 жыл бұрын

Since your fan controller end up running the fan slowly, you might be able to replace the fan controller with a 7809 (or whatever variant makes your fan spin appropriately). This ought to remove some PWM noise in your setup.

@chemistorge7873 5 жыл бұрын

Is there any chance of a circuit diagram including the ac part involving the 0.1 uF caps.

@TheHWcave 5 жыл бұрын

These caps are just to reduce HF and switching noise coming in from AC mains and not essential but if you want to add them, each of the 0.1uF caps is in parallel to a diode of the FULL BRIDGE RECTIFIER. Please let me know if that is description enough or you need more info.

@chemistorge7873 5 жыл бұрын

Thank you, that is brilliant.

@erakan6121 5 жыл бұрын

Good video, learned a lot, thank you but I have a question, why didn't you desolder the connector from old PSU and use it in the perfboard?

@TheHWcave 5 жыл бұрын

Yes, that would have been a good solution but for some reason it did not cross my mind.

@VincentFischer 4 жыл бұрын

Isn't the plastic housing only pushed onto 2.5mm pitch pins? I frequently use these JST XH connector housings pushed on the a pinheader on a breadboard. you can get these 100pcs packs for like 2dollar on ali

@williamreyes27125khz Жыл бұрын

Does anyone know why a FY6900 won't power up with 5v from a linear power supply. It will only power up using it's built-in 5v switching supply. There are only 2 wires from the p.s. board.

@TheHWcave Жыл бұрын

Since I don't have on, pure speculation from my side. I have seen tear-downs of the 6900 with just 5V power supply but they have 3 wires, 2x ground, 1x5V. Maybe you need a 2nd ground? Secondly, since the 6900 has to generate all the other higher voltages for the amplifiers by DC2DC converters, I assume the power draw on that 5V may be heavy. The power bank may be able to produce it but it may need some signaling (for power management) and if not, restricts its output to something that's too weak to power the generator.

@williamreyes27125khz Жыл бұрын

@@TheHWcave you may be right about the smps on my FY6900 having some signaling. I disconnected the 5vdc to the mainboard and saw a 0.8v 75ms pulse on the +5v wire.

@triplexdread 4 жыл бұрын

I really enjoyed watching this pal although it's an old clip , but why didn't you just use a T-30B triple output smps from AliExpress? $13 about £10GBP all in

@TheHWcave 4 жыл бұрын

Fair comment but actually the unit comes with a triple SMPS built-in. Its the SMPS that is causing the problems and earth leakage because of Y-capacitors. Any decent replacement SMPS will have the same problem. A unit like this should not use a SMPS or at least it needs a specially designed one that avoids this problem and still not cause EMC problems.

@triplexdread 4 жыл бұрын

@@TheHWcave Agreed. I just meant that instead of all that messing about somehting like the item I posted would have saved a lot of time and expense at the time ;). Cracking clip though mate, I enjoyed watching it :)

@ThinkingBetter 4 жыл бұрын

Seems the newer FY6900 has proper grounding. I ordered one.

@TheHWcave 4 жыл бұрын

Hi ThinkingBetter, That's good to know. Would you mind telling if those stray voltage problems are indeed gone with the FY6900 once you have it?

@ThinkingBetter 4 жыл бұрын

@@TheHWcave I just received this FY6900. No manual...but it's ok. I'm happy to see a 3 wire power connector. I connected it to my Siglent SDS 1202X-E oscilloscope (also grounded) with no BNC probe ground connector interconnected and a square wave signal. I was a bit surprised to see that running the ground through the AC cables is near as low noise as running the ground through the probe wire. Does this help?

@ThinkingBetter 4 жыл бұрын

Just tried to measure the resistance between the BNC ground on my FY6900 and my Siglent SDS1202X-E. It's 0.0 Ohms...so they both run mains ground to their BNC ground. In terms of actual noise floor, I'll check that later. I paid only US$107 for this 60MHz model in Amazon.

@TheHWcave 4 жыл бұрын

Well, if it is zero ohms, it seems they did put the ground in after all. Another way to test would be to connect nothing to the outputs and just touch the BNC ground with one lead of your multimeter set to AC-V while holding the other one in your hand, or touching something earthed. In my original FY6600 I could see around 100VAC that way. Do hunt for an online manual. This thing is so powerful and has so many functions, you'd be lost without it.

@ThinkingBetter 4 жыл бұрын

TheHWcave I find some noise around 150mV with a 43.6kHz detected clock in it, when measuring mains ground to the generator running DC out. But nobody should rely on mains ground between instruments.

@8ProductionRoad 4 жыл бұрын

Just by a more expensive proper device!

@UKSimon4170 4 жыл бұрын

Not everyone can afford expensive gear.

@audiumline4615 2 жыл бұрын

Brasil 👀🖒

@rsattahip 5 жыл бұрын

You're lucky you got rid of that power supply before it got rid of you. Should have been a safety cap.

@researchandbuild1751 4 жыл бұрын

Ugh damnit . Figures this generator is not worth the trouble

@TheHWcave 4 жыл бұрын

Actually the generator is great. It has amazing capabilities: 2 independent generators, one can modulate the other (AM, FM ..), a frequency counter as well and editable wave forms, burst mode, sweep ... Its only problem is the cheap power supply. I admit that my solution is a bit OTT. If I had to do this again, I would put a linear (!) DC supply (with proper isolation transformer) in a separate box and just feed the +-12V and +5V. It would save a lot of trouble with space and cooling problems and in a separate box you don't need to worry about heat sinks so the power supply can be really simple (3 regulator chips and a few smoothing caps)

@researchandbuild1751 4 жыл бұрын

@@TheHWcave im planning on at least doing the grounding mod

@johnadams9558 5 жыл бұрын

Before rebuilding the whole thing try plugging the USB into a grounded computer. Problem solved.

@TheHWcave 5 жыл бұрын

Your suggestion is similar to connecting the metal part of any of the BNC connectors to ground. While that gets rid of the stray voltage, it is at the cost of referencing the signal to ground. If you do this I recommend you take extra care how you connect the signal into your test setup which may have a different ground.

@johnadams9558 5 жыл бұрын

@@TheHWcave since I'm a noob with all this, can you recommend some sources explaining your point? Thx

@TheHWcave 5 жыл бұрын

Well, connecting a ground-referenced signal generator is a similar case to connecting an oscilloscope to your circuit. Dave Jones from the EEVblog explains the problem of having a ground lead from your measuring device in your circuit in his video #279 quite nicely. kzfaq.info/get/bejne/rsd1f9Ry1JrPm4U.html I know this isn't an oscilloscope but the problem. in principle, is the same. In most cases you will probably have no problem if your circuit to test is running from batteries or a proper isolated power supply. But if not, then you need to watch out. I'd rather not worry about that and hence I want the signal generator to be floating and NOT referenced to ground unless I do that explicitly myself.