| Electronics > Repair |
| Fixing Rohde & Schwarz FSIG (FSEA, FSIQ...) Ascom power supply |
| << < (8/9) > >> |
| Harry_22:
Hi Andi555! I corrected the drawing. The similar SMD capacitor on the bottom left has 0.15uF. Use the one suggested by Jarek. Could you make a photo of unsoldered soft start resistor to find a replacement. |
| Andi555:
Hi Harry, thats the charge resistor on the primary side of PFC. No visual burn marks, but "open". |
| Harry_22:
This is Vitrohm fusable resistor. https://www.vitrohm.com/content/files/vitrohm-ktf-wirewound-fusible-resistor-datasheet.pdf You can use the following A5MC https://www.uchihashi.co.jp/en/fuse/a5mc/ |
| Andi555:
These special resistors seem to be very hard to buy from a "normal" supplier for low quantities. Its a bit risky to replace it with a regular 5W ceramic power resistor and rely on the mains fuse... |
| Harry_22:
Don't be afraid to install a 5W resistor without a fuse. Your resistor was burned out abnormally. Its jumper didn't unsolder during long heating as it was intended, but the coil instantly burned out due to a short circuit. This is because it has thermal protection against breakage of the IGBT transistor. In this case, it turns out to be connected in series with the PS and a lot of power begins to be released on it. Below you can see the diagram of this unit from another R&S serial power supply. There a resistor without protection is used. It burns out when the PFC key is broken. For fun I disassembled both resistors. You can find fused resistor on Aliexpress. It is original. |
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