Anritsu MT8801B repair - Page 1
Forum section: electronics / repair

author: JoeyDeng
author_rank: Regular Contributor
timestamp: February 20, 2025, 04:20:43 pm
content: I got this instrument from an old friend. He sold it at a really low price (about $100). It's really dang heavy.After I got home, I found that its screen was completely broken, and the acidic liquid from the screen had badly etched the PCB of the front control panel. I cleaned it up, and luckily, it was still able to power on!A few days later, I got a new screen, and the first big problem arose—how to remove the front panel. 😅 I tried many ways, but all failed. Finally, I discovered that the set screws of the RF connector were hidden under the plastic sheet of the panel. What a disgusting design...After removing the screws of the RF connector, the panel became much looser than before. I carefully checked the entire panel and finally found that the DUT interface also had two screws. After removing them, I was able to take off the panel and replace the screen.After replacing the screen, I powered it on—and the display showed some text! Hooray! But after taking a closer look, I realized the screen had been damaged during delivery... Holy danggg! (Now I have to wait another three days for a new screen.)However, on this damaged screen, I could see an error warning: **"SRAM battery empty."** I removed the motherboard's shielding, and the design amazed me—it had a beautiful standalone card design! The SRAM battery was located on the first board. After replacing the SRAM battery, the machine still wouldn't boot up normally. After some research, I found that I needed to hold the *Preset* button while powering on to reset the data in SRAM. After doing so, it booted up normally.Now, I just need to wait a couple of days for the new screen to arrive and either repair the high-voltage generator for the backlight or convert it to an LED backlight.

author: JoeyDeng
author_rank: Regular Contributor
timestamp: February 20, 2025, 04:27:06 pm
content: Images to follow.

author: JoeyDeng
author_rank: Regular Contributor
timestamp: February 20, 2025, 04:44:37 pm
content: I couldn’t wait to fire up the signal generator, but the output was completely off. I took apart the signal generator board and noticed it was rattling—something had come loose… I dismantled the board, which had a bunch of shielded RF boxes. I opened them one by one and didn’t find any issues until I got to the largest box at the back. When I opened that one, I discovered a black piece had fallen out—it looked like some kind of magnetic shield (I’m not too sure about it, so feel free to correct me if I’m wrong). After retrieving it and soldering the broken trace on the RF circuit that it had damaged, everything worked perfectly. Awesome!!!Bonus: After I first assembled the whole instrument, I noticed there was an extra screw—I ended up installing that screw at the very end.

author: JoeyDeng
author_rank: Regular Contributor
timestamp: February 23, 2025, 02:49:34 pm
content: Hey everyone, yesterday I got the new screen I ordered and successfully fixed up my mt8801b. I spent ages searching for this screen on eBay—it wasn’t too expensive, just had some burn-in issues—so I ended up snagging one from a Chinese friend on Chinese eBay for about $20. When I received it, I was super excited because, unlike the last one, it had no scratches at all. I couldn’t wait to hook it up, but… this screen seems to have some lines on it. I tried pressing on the metal case over the screen, and the lines disappeared. I initially thought of asking my friend to get another one from a different seller, but with such a great price, I decided to fix it myself.First, I disassembled the screen and replaced the high-voltage tube with a COB LED strip for the backlight. Then I tackled the issue with the patterned display. I unscrewed the screws on the front, removed the metal casing, and found three PCB boards inside. I went through and checked every resistor and capacitor but didn’t spot any issues. Finally, I discovered that the FPC connector had a poor contact. After soldering it, everything worked perfectly 😁😁. It was just awesome! Once I put everything back together, I tested the spectrum with my LibreVNA, and it looked absolutely perfect.

author: JoeyDeng
author_rank: Regular Contributor
timestamp: February 23, 2025, 02:54:48 pm
content: This panel was also damaged—the 12V supply was completely fried 😰, but I fixed it by jumper-wiring it.