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| Rigol MSO5000 Power Supply |
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| Protegimus:
--- Quote from: BRZ.tech on September 23, 2023, 07:57:15 pm ---... I also verified that a 10nF/J/400V polyester capacitor was added, in parallel with CS5, which is the +5VDC voltage output. My suggestion is to add a 10nF/J/400V capacitor in parallel with the CS1 capacitor... You can keep the 10nF/J/400V capacitor, in parallel with CS5, without any problems. (see the photo). --- End quote --- Quick note to say that CS2, CS3, CS4 and CS5 are all on the +5V rail. Taking the suggestion from earlier in the thread I've ordered KEMET C0805C104J1REC7210 Multilayer Ceramic Capacitors MLCC - 100V 0.1uF X7R 0805 5% X7R SMD capacitors to bypass these just as Rigol have done with CS9, CS12, CS15 and CS21 but not yet had the scope open again to fit them. CS1 is actually between the anode/cathode on one side of DS1 the JH SRF2060C Schottky barrier rectifier diode (DS2 & DS6 also have the same 26R1 resistor and cap, to damp switching noise?). Attached image has the additional components marked up. |
| BRZ.tech:
Hi, Dear @Protegimus You are right about the CS1 capacitor. See in my post #31 the marking I made in the position in the image I sent. Note that the CS2 (electrolytic) capacitor was without the silkscreen, and you added it to your message, in message #35. Correct. Therefore, my suggestion is to place the 10nF/J/400V capacitor in parallel with CS2 (electrolytic), on the solder side. This will maintain the logic of your brilliant article. Here in my country I managed to buy TDK 10nF/J/400V and also 630V polyester capacitors. But PANASONIC brand electrolytic capacitors are not available here, and to import them, the legal taxes and shipping are astronomical and unfeasible. I won't change them for now. I also intend to place an extra 12VDC cooler, to blow the heat generated from inside the case to the outside, over the SMPS heatsink, to help with the internal ventilation of my MSO5000. I will put between the Voltages (+7V and -7V), which will give a total between them of 14VDC. And insert there (3x 1N4007 diodes) in series with (+7V), to give a drop of 3 x 0.7 = 2.1VDC. To maintain the Cooler voltage specification at 12VDC. In my country, temperature and humidity variations are very high, and on days with temperatures above 30 degrees Celsius, the inside of my MSO5000 heats up too much. I have already placed the new cooler outside the case, with an external 12VDC source, and the results are good, the internal temperature drops a lot. Without the new fan, sometimes the CH2, CH2, CH4 channel inputs are activated randomly, without the external cooler. I hope to soon complete the entire procedure and list the results here. I haven't opened my MSO5000 yet. It is now out of Factory Warranty. I have already defined what to do to install the polyester capacitors, and how to attach the new Cooler. I am very grateful for your commitment. |
| ballsystemlord:
In hopes of getting a lower noise floor, I wanted to try and upgrade my scope's PSU as well. No one seems to have mentioned that Rigol conformally coated the backside of the PSU's PCB. I'm not sure why they did only one side of one PCB. Anyway, I'm not sure what I'll do here. My guess is that they had problems with arcing from mains (Yikes) or maybe some sort of coupling to the metal case which is grounded. Hey, they saved money by using CapXons, so there's no way they would have gone spend happy on a conformal coating without a reason. I'm not sure what I'll do at this point in time. It might be just as well to roll a linear PSU and test that. PS: It's not obvious from other people's photographs, but the TO-220 packages do not have any part numbers on them. It's not that they were rubbed off, the part numbers are just plain missing. They're probably a really low end Chinesium type. |
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