Showing posts with label repair. Show all posts
Showing posts with label repair. Show all posts

Wednesday, 30 October 2019

MO28UO mouse


This MO28UO is an IBM-branded mouse from early 2000s I suppose. Looking around it may have been sold as Lenovo-branded too. Certainly it would fit the Thinkpad colour theme...

Although I like the slightly old-school weight and speed of the mouse, I noted the wheel is prone to mis-interpret the direction.

I opened the mouse and took some images.


The scroll wheel is not based on an optical coupler, so the wheel doesn't have holes. The axle had accumulated some dirt and hairs, which I removed.

I didn't expect it to matter much in this case.



The wheel part is simply lying on top of the wheel button switch, which might already be a source of some problems.

After cleaning, the wheel might have improved slightly but I suspect the mechanism is simply not that good to begin with, or it has become worn out.

Although a tactile/audible response from the wheel is a good thing, this one's a bit too noisy for my tastes.

So I guess I'll abandon this mouse...



Monday, 11 June 2018

Fixing a Fostex 280



I have had a Fostex 280 (1989) 4-track tape recorder/mixer for about 20 years. I bought it used, around 1998, did some funny stuff with it but then generally forgot about it. At some point I considered it a junk item as the tape recorder had ceased working.

Now I found a 4-track tape with something I'd not heard in 20 years, which gave a motive to look at the device again. Searching the net I was pretty sure the tape recorder belt was faulty, which was also easy to confirm.

Also, I had probably misused the multitracker back in the day, so it might be interesting to record something with a bit better understanding of sound dynamics and a more appropriate cassette type.

The Fostex does 4-track on a C-sized cassette, simply creating four magnetic trails instead of two, using a higher speed than ordinary tapes. The mixer part has 4 main channels with equalization, gain, two AUX buses and various re-routing options. There are also 4 more channels with less options, giving a total of 8.

Channels can be recorded on one track, or stereo-recorded over two tracks at once. Tracks can also be bounced, re-recording for example three tracks onto one, giving more space for new tracks.

The digital control over the 4-tracker is pretty neat, as the tape counter can be set to zero at a convenient point,  and then >>0<< rewinds the tape back to that position. There's also one alternate memorized position that can be used as a loop end position, facilitating loop and auto-record.

Looking at eBay listings, a working Fostex 280, although not super-expensive, is not exactly trash either. Going back the memory lane, I remembered how fun and uncomplicated it was to do a recording without a computer.


Replacing the belt

As I saw the multitracker was not completely lost, becoming motivated again, I then ordered a replacement belt from eBay and received it in two days. Day later, I had it replaced.

When the belt has disintegrated, the tape deck can't really behave at all. As the Fostex is switched on, it will give a horrible creaking sound and an "E" on the display. Furthermore, the tape head may be left awkwardly in a position that makes it difficult to remove or insert the casing cover or even a cassette.

The dreaded "Red E of Death"
These are often indicators of a broken belt and replacing the belt got rid of these problems. Listening to my tape was bit of an anticlimax though, but nice experience in a time travel sort of way.

This video by the Youtuber account "3rd island" shows absolutely everything about the process. Without it I might have wasted time or even broken things. I'll recap the main points below:
  • Remove all faders, unscrew the case cover and then gently pull out the cover.
  • Disconnect cable connectors that might hinder the cover. There's no point in trying to keep the different units connected during repair, if they are in your way. The connectors are quite well color-coded and have logical sizes, but just to be sure you might want to photograph the starting position.
  • Pull out the circuit board with the faders. There's a foil between this and the circuit board below. The foil does not need to be fully removed, just disconnect all the connectors that lead to the tape unit, and make some note of their routes between the capacitors.
The white, red, blue and yellow are for the tape unit.
  • Remove the four screws that keep the tape unit in place. Take note of the ground wire that is also screwed in. Pull out the tape unit.
  • A metal panel needs to be removed before the belt can be inserted. This part is held to the unit with only one mechanical screw. Take care with removing the screw as this holds a couple of other parts in too, mainly the spring. Also, take at least a mental note of how the spring is held in place, before loosening any parts.
  • Now the belt can be positioned around the metal wheel. The other end may be stretched around the small black plastic protrusion next to the plastic wheel, which is the real target for the wheel. Also, make sure the plastic wheel and the metal wheel are clean.
The belt is temporarily stretched over the black plastic stick.
  • Putting the tape unit back together, make sure the spring is in correct position. After the screw is in, the belt can be moved from the temporary position to the actual wheel. As shown in the video, tweezers are good for moving the belt.
  • The ends of the spring need to be re-located, use a combination of a small screwdriver and tweezers to achieve this.
 Left: The hook for the top side of the spring end (not in place). Right: bottom spring end hook (in place)
  • Put it all back together, don't forget the grounded wire under one of the four screws and don't forget any of the connectors.

What makes this fairly simple is that the insides of the Fostex are quite modular and the tape unit is easy to remove.

As I went through the process I soldered back one of the headphone sockets which had come loose. To tell the truth there's a lot of other problems with this multitracker, such as a bit lazy/random rewinding and fast forwarding. Some of the channels have ceased working properly.

I'm wondering if some of these might relate to bad capacitors or similar issues. So, the recording experiments may have to wait for a while. But at least I got my sound out from the 4-track tapes which was enough for now.

Saturday, 24 March 2018

KC901 Family Game



Following a tip-off, I bought this Chinese console from a flea market for 2 euros. It looks vaguely like a Sega Megadrive II but I suspected it was probably a NES clone.

The case is labeled as KC901 Family Game, but I could not find much about it on the internet. I did learn the polarity: tip is minus and the ring is plus. I tried with 9 volts and this appears to be ok. Also, some say the A-V plugs are not really connected so there is only RF. Looking closer at the circuit board this seems to be true, the parts are soldered in but there is no connection!

Left: the TV/power stuff, centre: the CPU/Cartridge, Right: Controllers/inputs
I stripped the cartridge of it's cover, which had come loose anyway, then went in into the console itself. There's a large "clamp" thingy that helps remove a cartridge with a push of a button.
I removed this and all non-essential parts and tried to connect the device to a TV, but got no picture.

Looking inside, I saw that someone had tried to re-solder a few connections and the RF, and the results are even uglier than my own solders. The circuit board surface had become damaged too.

I removed some with a solder pump, cleaned the connections and tried to get the thing running. Eventually I could get a hold of the picture via antenna, and it's a pretty solid image for an RF.

The controller and CPU compartments are quite clean, the power/TV not so much
I also tried whether the internal "video" pin could deliver a signal to the TV video, but although I saw a glimpse of a rolling dark ghost of a screen, this does not seem to be the way to go. If it were so easy, the A-V would probably have been connected.

Guess if there are really 150 games...
For some reason I could only get one controller working. Plug them both in and neither works. There's logic inside the controllers, they are not simply a bundle of switches, so a broken controller or a wrong connection might explain this.

What's a "Comnado"?
But it's enough to see this is a NES clone alright. The 150-in-1 cartridge is even a bigger rip-off than my other 8-bit "Powerstation 64" NES clone, here there are maybe a handful of games with zillion variants with different names.

Possibly the variants have been patched to create some negligible difference, but I could not be bothered to check this. The presence of Duck Hunt and Wild Gunman shows this system has been indeed sold with a light gun, but without one I can't really play them.

The power/ TV crap, showing some of my cable additions
Although I'm not 100% certain the 150-in-1 belongs with the console, I think that's the idea. Can't say if a NES clone like this runs real NES cartridges, and if it does, do they need to be Japanese, European or US? No clue.

Wild Gunman