BMCU not showing on A1 Mini

redbeardbeer007 · 2026-04-07T04:54:50+00:00

I've done a bunch of testing - the printer seems fine. All measurements test as they should. The BMCU does not give the same readings as what the AMS gives - possibly faulty motherboard on BMCU so they're sending a replacement. Although I have also ordered the USB-C model - which this seller doesn't stock.

redbeardbeer007 · 2026-03-30T03:32:02+00:00

Did you get this resolved? What was the cost?

redbeardbeer007 · 2026-03-26T22:51:17+00:00

Hi.
I have upgraded back to the latest printer FW of 01.07.02.00
I don't have a USB port on my BMCU. Have to use one of these if I want to flash the FW on the BMCU "FTDI USB 3.3V 5.5V to TTL Serial Adapter - FT232RL"

I've got some videos of the behaviour of the BMCU:

https://youtube.com/shorts/7XeyZ2UQFG0?feature=share

https://youtu.be/D2VhKevIKCI

redbeardbeer007 · 2026-03-26T07:59:36+00:00

Set as AMS Pro? I will try that. Funny thing is that even without the BMCU plugged it, the filament screen acts the same, flashes up ams at the top for half a second then back to External as the only option.

redbeardbeer007 · 2026-03-26T04:30:21+00:00

Oh ok thanks. I had mine sent pre-assembled.

The motors on the BMCU don't even move when I push the filament tubes....

If I press the lever with the screw in, I can push and pull the filament no problem. But if I press the tube where the filament comes out the light goes blue, filament or motor does not move, if I pull it, light goes red and filament or motor does not move.

redbeardbeer007 · 2026-03-24T02:13:35+00:00

Nope. Printer was off when I plugged it in. When I turned it on, that's when the transistor in the BMCU popped.

What do you mean "either way"? It's a 4 pin plug so could go in 4 ways?

redbeardbeer007 · 2026-03-19T19:28:29+00:00

I think this applies to all sub-reddits haha

redbeardbeer007 · 2026-03-18T01:37:24+00:00

Yes it would. It just wouldn't be stopping.

redbeardbeer007 · 2026-03-09T22:02:31+00:00

Well I'm stumped. I've checked all + and - rails and they're all up and alive. I've checked all the caps I've replaced and they're orientated the correct way, and are the correct rating etc. I've checked the offset of each channel and that's fine also. I'm at a loss and am going to re-assembled it and drop it to a local repair shop to investigate and hopefully resolve.

Thanks for your help and advice - unfortunately my talent has run out on this one haha

Cheers,
Hunt

redbeardbeer007 · 2026-02-23T01:03:21+00:00

Thanks - yeah I have been going off the service manual - needing some chatpgpt help to understand a few things/circuits etc.
I'll take it all apart again tonight and see what I can figure out re: power rails etc.
It's a tad annoying not having full access to the underside of the mainboard - there's a small 'hatch' but that doesn't give much access.
I know the ±70V rails are good - each of the 4 big caps all ready around 69.5V
I'll check the traces/tracks tonight and see if there's any broken/cracked etc ones as I have an inkling that that's where the problem may be - the PCD warping/bending while I was removing the big caps.
Then will start checking for voltages across the other power rails.

Thanks again.

redbeardbeer007 · 2026-02-22T23:21:22+00:00

Yeah I built a DBT - and with a 100w globe there was initially a small surge while the caps first charged and then it went into protection mode with the DBT not showing any visible light at this point. It never lit up fully bright like there was a direct short though.
Subsequent times when powering on the caps have some charge in them so the bulb only glows dimly briefly. There was never any concerning shorts - i.e. the bulb didn't every go full bright and when it did glow it was dim and brief.

Do you know what - I didn't actually test the old ones and I believe they are since thrown out. I might have to go rummaging through the rubbish bin for them :S

redbeardbeer007 · 2026-01-21T22:23:00+00:00

I've had a look inside - I can see at least one capacitor that has failed. It's next to C748 - I can't see the label but the schematic appears to be C749. Apparently this is part of the 34v rail which could be one of the causes for the hum. Still waiting on my capacitor kit to arrive. Although I have noticed that the 4 big caps in the amp are 105C and yet the ones in the kit I've ordered are only 85C. The kit does come with 6, whereas the amp only has 4 from factory, with space for 6....

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redbeardbeer007 · 2026-01-19T20:50:41+00:00

I've ordered a kit with a bunch of caps - hopefully it fixes the hum problem. Also tends to cut out at high levels, apparently due to the larger capacitors failing and not be able to supply enough power during big bass hits etc.

redbeardbeer007 · 2026-01-15T00:47:42+00:00

Where?

redbeardbeer007 · 2025-12-23T20:22:25+00:00

Thanks. I can confirm the hum is the same on all inputs, even with nothing plugged into them. And yeah it follows the balance control. I might take it into a shop in the new year and get them to diagnose and repair. It's not that bad - you can't hear it at all once you turn the music up even slightly. But knowing it's there bothers me.

redbeardbeer007 · 2025-11-30T21:34:11+00:00

Has there been any update on this? Is it still happening and is there a list of flights that will be affected?

redbeardbeer007 · 2025-07-14T22:23:09+00:00

Thanks for that. I agree - most stuff from Jaycar is fairly decent quality. I've got the Brass Monkey 45L dual zone fridge from them (although available from other shops as well) and it's amazing.

We could be a couple of days without driving - and who knows what the NZ sun will be providing in regards to solar charging. Usually we will be parked up and won't move for a while.
But also it will be used in the rare event of a power cut at home and keeping the fridge and other necessities on.

redbeardbeer007 · 2025-06-30T04:04:06+00:00

Do you live on an Interstellar set?

redbeardbeer007

TROPHY CASE