(SOLVED) Anthem MRX310 display issue - Page 1
Forum section: electronics / repair

author: rfengg
author_rank: Regular Contributor
timestamp: April 17, 2025, 08:58:00 pm
content: Hi all,Having display issues with my Anthem MRX310.Does anyone have a service manual or schematic for this receiver? The display sometimes is completely blank and sometimes shows gibberish. Any pointers on what the issue could be?thanks

author: MathWizard
author_rank: Super Contributor
timestamp: April 29, 2025, 06:12:01 am
content: Do you have an oscilloscope ? IDK these stereo's, but I wonder if the data getting sent to it has a problem, or if the display driver voltages have a problem. Is the display a VFD type ? Did you take any pictures?There's not usually much external circuitry around any of these screens, most of the work is done with microcontrollers, and/or special VFD or LCD driver IC's.

author: rfengg
author_rank: Regular Contributor
timestamp: May 04, 2025, 04:25:31 pm
content: @MathWizard Sorry for the delay in replying.....was away from home for a few days.Have attached pics of the VFD and the whole front panel display. The VFD is supposedly a CIG33-1612N but I could not find a data sheet for this.Yesterday did some more troubleshooting and from a schematic for an Arcam receiver which uses the same CIG33-1612N, it looks like the voltages for the filament, logic 5V and cathode are present and correct. The CIG33-1612N houses an on glass chip as it uses a SPI interface but I changed out the whole display from a friend's receiver and the problem still remains.So your intuition that the data might not be getting to the VFD could be correct. Next week I plan to get hold of a scope and check if there is any activity on the DATA, CLK , CHIP SELECT and RESET lines. I am not very familiar with the SPI interface so any guidance on this would be most appreciated.

author: MathWizard
author_rank: Super Contributor
timestamp: May 05, 2025, 05:01:18 pm
content: Chances are the VFD is fine then.1 of the voltages, I think the filament, should have some AC on it. For example I made a VFD driver, and I think it was DC centered around -15V, but had an 5VAC part that went up/down, so overall it went between -20V and -10V. But even if that was stuck, and not changing, you should still see something, if the DC level is enough.Have you tried applying any voltages ? The AC part is more for keeping the the coating from burning away. But you can briefly apply, fairly low DC voltages, and see which segments light up. I can't remember all the details, but most of these VFD work the same.https://www.g7smy.co.uk/2016/04/hacking-a-vacuum-fluorescent-display/Here's a picture of the SPI between a DVD player MCU, and a VFD driver IC. This was taken with a cheap logic analyzer. If you are lucky, all the correct data might still be getting sent from somewhere, like a main MCU, and only some extra driver IC is broken. The main thing you don't want to lose, is the MCU/IC with the software/data on it, that takes programming.Depending on the parts used, there might not be 2-way communication, so there would only be the chip select, clock, and MOSI.https://www.analog.com/en/resources/analog-dialogue/articles/introduction-to-spi-interface.html

author: rfengg
author_rank: Regular Contributor
timestamp: May 05, 2025, 07:52:40 pm
content: "Have you tried applying any voltages ? The AC part is more for keeping the the coating from burning away. But you can briefly apply, fairly low DC voltages, and see which segments light up. I can't remember all the details, but most of these VFD work the same."I don't think I can do this, as the VFD has an onboard chip with a SPI interface.Am going to get a scope to see if the DATA, CLK , CHIP SELECT and RESET lines have any activity on these lines; if not work backward to see from these lines are driven from.I hope these are not interfaced directly to the MCU which may be a PIC or some other processor.

author: rfengg
author_rank: Regular Contributor
timestamp: May 20, 2025, 03:32:11 pm
content: Scoping the signals did the trick.......unfortunately the trace feeding the DATA line to the VFD on the main board was broken......bridging the trace with a fine wire, and the display is BACK!!!!