Ubuntu Linux: “Stopped – Unable to add document to print job” Epson ET-4500 printer

Whilst in the middle of printing,  I accidentally touched the turn-off button on the printer & after that, nothing would print and the printer status in the System Settings/Printers for my ET-4500 showed as: “Stopped – Unable to add document to print job”.

I searched the printer menus, but could find nothing to help. It just wasn’t handshaking.

I deleted the printer and re-installed, selecting Network Printer and AppSocket/HP JetDirect. In the host field I typed the fixed IP address 192.168.m.n (m.n being the numbers I assigned in the printer settings). I clicked Forward and selected the test page option.

It worked!

Problem: ASUS ZenPad 3s 10 fails to turn on/won’t start – magic spell

Generally this tablet works very well. Sometimes, for no apparent reason, it fails to turn on with the Power button (the small silver button about a quarter of the way down from the top on the right-hand side).

I keep forgetting how to clear this problem, so I am making a note here. The problem has happened a few times over the years.

I waved my fingers over the device and pronounced the following spell with gravity: Nil Desperandum Carborundrum! Then I held down the Volume-Down button (nearer the top on the RHS) and the Power button together for 5 seconds.

This elicits a sort of boot menu:

Select Boot Mode:

[Press VOLUME_DOWN to select item. Press VOLUME_UP to confirm.]

[Recovery    Node]                                             <<==

[Fastboot      Node]

[Normal        Boot]

Normal Boot sounded good, so I clicked Volume-Down twice to select it and Volume-Up to activate it. I got the ASUS banner & then the PIN screen. I entered the PIN & it booted fine.

Then I shut the tablet down.

Holding down the Power button alone (for about 6 seconds) worked then to start the tablet.

Now I’ve shared this magic spell with you, I have to shoot you.

This reminds me of a wonderful T-shirt from tech support days. On the front it said: It should just work…


Skoda Octavia Bolero radio mute problem/fault – complexity & stuff that doesn’t work

Another distraction from planned projects:

The car radio had decided to lock itself in a muted state. This isn’t much use for a radio! The CD player wouldn’t play any CDs. Turning up the volume made no difference. This mute is not volume fully down; sound is disabled. On the plus side, it had cured the problem of the annoying beep for touch-screen buttons.

What puzzled me is that there is no mute button. I searched the physical buttons. I searched the soft buttons in the screen menus. I searched the steering wheel & column for radio controls. No mute button.

In desperation I tried a reset to factory settings. This wiped all my presets.

Apparently Skoda has been swapping the radios under warranty to fix this fault.

Today my son Kevin M3KGC found a fix on an internet forum: hold the on/off button down for about 10s & the radio switches off & eventually re-boots. The mute symbol has gone & the sound is back… until the next time.

I suppose there is a computer in there controlling things. This looks like a software error. If you are having to search internet forums to find out how to turn the radio sound on, then the radio is too complex. At least this radio has a couple of knobs. Some make do with clicky buttons, clicking round functions in a loop. Damn! Missed it! Click round again. The buttons may have black markings on a black background. I could go on!

The forum discussion is here:


Look for andyvee‘s helpful contribution.

The downside is that the annoying beeps are back.

Honeywell ST9400C central heating programmer fault problem fixed

About 2 years ago we had our central heating boiler replaced and a new Honeywell ST9400C programmer was installed with the new boiler. This worked fine for about a year and then we found that although the radiator circuit came on via the timer, the water heating (to the hot water cylinder) did not. The green LEDs came on for both circuits however. I found I could still press Extra Hour on the h/w side and it would then heat the hot water. It just didn’t want to operate hot water and space heating together.

I was busy with other jobs and did not feel confident about getting a heating engineer in, so I just used the Extra Hour button work-around. I bled the system of air & re-pressurised it; this made no difference. I wondered if some sort of fluidix effect was in play where the water decided to go round one circuit & kept going on that one circuit.

Summer came & the hot-water worked fine on the timer, with no space heating necessary. When that stopped working I checked out the ST9400C. It was 2 years since installation.

I found this is a Atmega 3290V microprocessor based controller. It has two 48V DC relays which provide switching to switch the mains Line out to “OFF” or “ON” outputs (presumably for controlling open/shut on zone valves). One pair of outputs is for the h/w circuit, the other for radiator space heating.

I discovered that when one circuit was on, the relevant relay only received 21V DC, well short of 48V. With both circuits on, there was only 16.5V. Presumably the available power had been reducing over time so that at first there was only enough to trip one relay and then eventually neither relay would switch.

There were two aluminium-can electrolytic capacitors near the diode bridge & I replaced these with capacitors rated 63V. This did not fix the problem. I tested the big blue mains series film-type capacitor. It did not seem to leak, measured with a DVM & it measured 0.1uF on a bridge. I was puzzled. I did not understand the markings on this capacitor so I did some internet research. I discovered the capacitor should be 0.68 uF. So perhaps it was leaking and failing under mains voltage?

I replaced this capacitor with a similar 0.68 uF item, but with a higher voltage rating & re-tested the ST9400C. The voltage to the relays was well up, better than doubled and they switched over fine. So that problem was fixed!

The previous boiler & mechanical clock controller had worked fine for 30 years. That did not contain any capacitors though. The fancy Honeywell controller lasted a year before going faulty. Maybe the capacitor was poor quality?

Older, simpler, AC devices are being replaced with more complex devices which have chips & processors requiring DC supply and so more components. The processors run software.

An aeroplane now is a computer network which happens to fly.

This is all fine if the additional risks of complexity are off-set by sound design & maintenance so that stuff works. The risks may increase with the internet of things. I hope I don’t get to the stage where the car won’t start because the fridge is having a network flame war with the toaster!

Douglas Adams foresaw this sort of situation years ago when the spaceship Heart Of Gold was distracted from defending against a missile attack because Arthur Dent had requested a real cup of tea from the vending machine. He was ahead of his time, that man.