Dead Rigol DSA815-TG  - Page 1
Forum section: electronics / repair

author: c.musa
author_rank: Newbie
timestamp: April 25, 2025, 05:31:17 pm
content: Previously posted on its specific thread (seehttps://www.eevblog.com/forum/testgear/spectrum-analyzer-rigol-dsa815/msg5888958/#msg5888958), hoping to get some kind of help:I have bought a Rigol DSA815-TG for parts just for the cheap price.The guy who gave me listed it in the following conditions: after an attempt to upgrade firmware, does not start anymore, hardware is ok.In detail this happens:The power button flashes on mains connection, if pressed, stays lit and let the internal fan to run.No other button lights up, same behavior as second part of the video in msghttps://www.eevblog.com/forum/testgear/spectrum-analyzer-rigol-dsa815/msg4703486/#msg4703486Black screenIt does not show up on usb devices listIt does not show up on Ethernet10 MHZ OUT is presentBoard number DSA815_V02.05Things tried/checked:Voltages from the mains supply seems right, even if slightly different fromhttps://www.eevblog.com/forum/testgear/spectrum-analyzer-rigol-dsa815/?action=dlattach;attach=1723628;imageBattery checks at 3.08V, both when turned on or offVoltages around the boards test points are ok, except for:TP1103 marked +3.3V USB near the Cypress (Infineon) USB MCU measures 0.76V (see photo)TP1207 marked +10V near the screen connector measures 7.2V (see photo)U1105 seems have been under a poor solder job, maybe the previous owner tried the bridge btw pins 7 and 8, now easily fixedSaid that, I doubt that was only after "a firmware update attempt that failed". I have also tried the firmware update keeping the PRESET button pressed, without success (it is described in the firware update installation instructions).If I supply 3.3V (@100mA limit) on the +3.3V USB point, the instrument shows up on the USB as : Unknown USB Device (Device Descriptor Request Failed). Removing thesupply, the Test point now measures 1.4V.This supplies actually comes from U1109, an SOT-23 marked X1LV, (a transistor switch probably, seeing the 01C=10k resistor near it) that receives correctly the 3.3V rail.Other testpoints in the area marked respectively SDA, SCL are at 300mV before applying 3.3V externally and 1.4 after; RESET is always at 3.3V.TP1104 marked 12MHz is dead at 0v on the oscilloscope.I tried also to supply +10V@100ma at TP1207 described earlier, but nothing shows on the screen.Any advice on what can be happened and/or how to proceed?Personal notes on the troubleshooting/teardown process:Keep blue marked screws on the aluminium cover separated, they are longer than the others.Some test points marked on the silkscreen apparently seems placed randomly, but you can find the testpoints on the opposite side of the board.

author: fzabkar
author_rank: Super Contributor
timestamp: April 25, 2025, 09:07:17 pm
content: The Actel IC seems to be controlling the Base/Gate of U1109 (PNP BJT or P-ch MOSFET?). Perhaps this IC should be the focus of your attention?

author: Zenith
author_rank: Frequent Contributor
timestamp: April 26, 2025, 01:41:49 pm
content: If it really is just a failed firmware upgrade:There may be a factory reset or rescue USB, ask the Rigol agent.There may be a UART, so you can see what happens at boot time, (if anything), and that may report a problem, which would help narrow things down.There's a Dave Jones teardown video on Youtube which may be useful.