Hayling Island

Hayling Island

Saturday, December 31, 2016

Happy New Year!

Let's hope 2017 is a good one.


So the laptop has died that I use to run LIFUTIL. It started with the diskette drive failing, but quickly became beyond repair when the LCD decided to go dark as well.

I have an older machine in the office, and I found an old diskette drive in the museum box. (that pile of stuff I can't bear to part with). The older machine is a Dell Optiplex 780 desktop, and it has a hole in the front for a diskette drive, so I dug around for a cable, eventually found a power supply cable for it as well, and went inside the Dell.

Couldn't find where to plug the 34-pin cable. Ah, found the site for the cable on the motherboard, but it was not populated in manufacture. Ah.

So, I remember I have yet another machine in the shed - a Lian Li case I bought off eBay with an older motherboard in it. Lian Li cases are lovely - all aluminium, all soft edges that don't cut the fingers and can carry multiple fans, huge power supplies, multiple hard disks and a huge variety of motherboards. Go get it, clean it off, vacuum it out, leave it to warm up and dry out properly before installing diskette drive and applying power.

And nothing happened.

Replaced power supply (temporarily - it doesn't fit, but it does plug in kind of), and something happens. It boots! But, it is booting Windows 7 which won't help with running LIFUTIL, so I create a supposedly bootable Win 98SE CD to put in it. (at this stage I must have done something wrong since the CD didn't turn out to be bootable later)

DVD drive won't eject. It's stuck with an old CD in it. Eventually free it without damaging the drive. The CD, not so much. However, the new CD with Win98 on it won't boot. Hmmm .. however I have the IDE drive from the laptop with Win 98SE already on it .. I could put that on one of those converter things that allow you to plug a laptop drive onto a 40-pin IDE connector. I have one in the museum box. Woo hoo.

Boot machine. It spends an awful lot of time changing its configuration and installing drivers for motherboard chip sets, bridges, IDE controllers .. and then asks me to put the CD in to read something else it needs. Put CD in drive. Wonder why clicking on the continue ... means nothing happens. Click here and there. Nothing. Reboot machine. Nothing. The motherboard has failed.

I go to re-seat the memory DIMM and find one memory chip at a hugely high temperature. I find this with my thumb, which is still stinging. Relegate this beautiful case to the list of Things To Do for the future - buy a new power supply, disks, motherboard, memory and decent display card for a new Office Machine (Hackintosh compatible). Fireball will be relegated to be just the workhorse server she is now, but won't be tampered with by me trying to use it for desktop things any more.

Have now bought another Dell Optiplex GX620 from eBay. It's only 21 quid. Has been tested, has DVD drive, a network port and a diskette drive .. hopefully this will be the last subroutine call before we start working back up the call stack. When it arrives, I will only have to install Windows 98SE, get it on the network, download LIFUTIL and the drivers for the 1G sample/sec scope, create the diskette and off we go.

Friday, December 16, 2016

New board for the HP 16500A

I need a scope to debug the old SM4100 amplifier I have. Noisy on one channel, so it is likely a capacitor has gone a bit south. However, the scope's power supply has failed. It is a bit of a complex thing to fix without a scope. This is an attempt at recursion which I can't support. Physician, heal thyself.

So to satisfy the need for a scope to debug the power supply for the scope, I was lucky enough to find a cheap 1Gs/sec plug in for the HP16500A I have.

And, it arrived from the US! Much excitement from Wifey since she thinks I am buying stuff from the US for Christmas for her.  And I plugged it in - but it is not recognised by the mainframe. That's because the file for the board is not on the boot diskette .. so I need to get the file on to the diskette.

I have the file downloaded from Keysight Technologies (who says there is no such thing as Silicon Heaven?), and I have an old laptop with the LIFUTIL program that writes data in the strange 77-track format that HP needs .. and guess what? The diskette drive in the laptop has ceased to function.

So, I have an amp in need of repair, a dead scope, another scope that needs a software update, and a file to update it with, but now I need to find either a replacement diskette drive for the laptop, or I need to install a diskette drive into one of the desktop machines, fire up Windows 95 or 98 on it, download the files, run LIFUTIL ..

Lots of nested calls here with very few returns. 

Monday, November 14, 2016

Now to repair the SM-4100 I need the scope working..

.. and what happens? I power up the scope (HP 54502A) .. and it shuts down 10 seconds later.

It's a power supply issue. Apparently quite well known on this family of scopes. There are no like-for-like replacements around. Fortunately it does seem to work OK for 10 seconds, so I hope that the PSU going south hasn't killed the motherboard. I have a schematic for the PSU ...

There are some obvious weak points, which I have checked. What I really need to do is to break the feedback loop and fire up an external PSU to see where the issue is. Of course I would need a scope.

However, I have found in the schematic, hiding away, a crowbar circuit. It's a small bit of gizmodery on the voltage regulator board that has a thyristor in the middle; thyristors have the characteristic that once switched on, they only switch off again when the current through them drops to near zero. This one is wired so that the +5v and the +15v are shorted to ground if any of the output voltages exceed some threshold. The shutdown behaviour must be the crowbar doing its job .. so now I have the PSU disconnected from the scope, a dummy load of half a dozen 0.33 ohm resistors in series on the +5v; I am going to disconnect the thyristor, and see which of its inputs is causing it to switch (and it seems to be watching all of the rails in one way or another; +3.5v, +5.15v, +12v, -5.2v, -12v ... ) 
Disconnected the crowbar. It's no better, so it is not the crowbar doing it. Next theory is that it is a capacitor on the secondary side which is absorbing lots of current. Firing up the supply, and touching all of the capacitors - can't find a hot one. Not sure where to go without a scope ..

Saturday, October 29, 2016

Sharp Optonica SM-4100 Schematic

I have one! Found the old paper copy from a very long time ago, and for the benefit of those out there in InternetLand, I have posted a copy of it in jpg format.

Go to this link for the big version --> SM-4100 Schematic

Sunday, October 16, 2016

Repaired my biiig Plasma TV

I was gutted when my lovely plasma TV decided to die. It was only the video inputs that went - I could still get some things on the screen like the volume control. So, on the offchance, I went on that auction site again and looked for a new digital board for it.

Well, I was surprised to find a TH42PZ70BA digital board for 13 quid.

After removing what seemed like a million screws, I got down to the point where I could actually see the board I was trying to replace ..

I was even more shocked when the replacement worked - all back to normal again! 

This is probably the last time in my life I will ever repair a TV, I just thought. I grew up with mono TVs and new colour TVs with their tube output push-pull output stages (Philips G6), LOPTs and triplers and CRTs with rimbands, convergence with 22 pots to adjust and a ton of X-rays shooting out. I used to help repair TVs (and amps, receivers, tuners etc) for pin money as a student. TVs were most challenging since the focus voltage was a few thousand volts, and the EHT was 25KV. Quite scary to work on the things, and the dust would collect on the high voltage components. I used that as an indication on the neck hardware which pins to avoid touching (all of them).

Interestingly enough I had to apply a vacuum cleaner to this Plasma before I could repair it, as it was just coated in dust. 

These days, I do repair the odd LCD but they are very uninteresting. Occasionally it's a power supply capacitor that has let go. Sometimes that takes a switching transistor with it. Most other faults though, including the mechanical stuff - broken screens, broken connectors - I am sorry, but it's easier, faster and cheaper to go buy a new one. It rankles a bit, and offends my sense of wanting to repair rather than replace, and my care for the environment. When did manufacturers give up on designing things for repair? Well, if the plasma is anything to go by, about ten years ago.

Monday, August 22, 2016

Virgin Media delivers ...

(I have no affiliation with etc etc .. only commercial interest is if you are thinking of switching, let me recommend you and I will get a discount off my next bill) ..

After a bit of to-and-fro with Virgin Media, and a few days of suffering dropouts every couple of hours, I have a new Superhub 3 installed and the latest broadband package - at 20 quid a month less than I was paying .. 

I ran Speedtest ..

Saturday, July 30, 2016

.. And in the meantime I thought it a good idea to buy a little runaround ..

So I am working on the big girl. I have it in mind to do a bob/rat/chop on her .. she is mechanically very sound (probably needs the clutch sorting out along with the brakes needing a rebuild, new air filter, oil filter, new tyres, seized fuel tap, seized choke, seized throttle cables, switchgear needs sorting out, new sprockets and chain, rusty frame needs sorting out and the seat needs recovering and repadding. Front headlight is rusted out on the rim, and the front mudguard is cracked. The battery is long dead. The front handlebar bar ends are rusted out to where I am not sure it will be possible to get new grips on her).

My vision statement for her is something like this ..
 She is a bit of a pig at the moment though, lots of bolts shearing and so on. I did get the exhaust off, but one stud snapped, so I will have to borrow / buy EasyOffs to get the stud out. I like the wrapped look as the picture above .. the wrap comes from China, and is not too expensive.  I like the idea of a matt or satin black frame where it needs repainting, satin black wheels and spokes, whitewall tyres, creamy white paint job on bobbed mudguards and tank, with an airbrushed orange edging. WS2812B LED strings around to pick out the lines of the bike at night - default colour orange again, but hey! what would be the point of WS2812 without a microcontroller doing some fancy lighting patterns.

So, it's going to take a little longer to sort out the old girl than I hoped. I might make some good progress in August - anyway, it gives a window of time where I am not driving a car, and I am now working across a few of the NHS Trusts in the South. The car parking is outrageous at hospitals, and it is no better for visiting staff. It's not much better for permanent staff - they might let you park in the park and ride for a fee (!). I'm also over on the other Island quite a bit, so I thought it would be a good idea to get a little runny around kind of bike in the meantime. She was cheap, so there are some bits to tidy up. The grips need replacing, the sprockets and chain were well beyond sell-by date, the rubbers on the pegs are worn. But she starts first time, which is one of the the major requirements of a commuter bike. 

I've got some new grips on order from China, and very pleased with the gold chain and replacement sprockets. 

Might have to replace those shocks and springs sometime - they look a little shabby. But then I am in danger of spending more time and money on the little runaround that keeps me on the road, when I should be spending money on the big girl.

Tuesday, May 3, 2016

Fooze that bike!

I've decided that this is the year to get my bike back on the road. It's in a bit of a sorry state, but nothing that a few tens of hours with sandpaper, primer and paint won't sort out. I need a bit of a something to get my teeth into that isn't just electronics.

The bike used to look like this when it was new 16 years ago:

I hope to to something a bit different with it, and get it on the road again this year. It would be fun to get over to the Island on it! and I should be spending a couple of days a week there this year for the project I am working on at St Mary's.

.. and we are live with Asterisk!

I solved the issue with the analogue phone lines by getting rid of them. For the princely sum of 5.95 per month, Sipgate offer a trunking service, which means you can get your Virgin Media provided phone number transferred to them, and they will forward all calls to that number back to your own Asterisk system.

I've not done anything too complex so far, but it all works. If someone calls, then the VoIP phones (the Cisco ones) ring - first the main ones, then if they aren't answered the ones in the office and craft room get added on, and then if they are not answered, the mobiles ring!

If the call drops through to voicemail, the message is sent via an email attachment to us, so we can pick it up on our mobiles wherever we are as well.

Now Virgin Media charged me 17.95 a month for the privilege of a phone line. Since I don't need that any more, I wonder what their reaction will be when I ask that I have that money taken off my bill?  (Please note this only works if your current provider doesn't use the phone line to provide your broadband. Obvious when you think about it!)

All bets taken. Mine is that I might get a discount of a fiver after months of haggling.

*** Wrong again. After haggling, VM tell me that it is actually more expensive to change package to stop paying the line rental than it is to keep it. We need a bit more OFCOM legislation I feel. 

Monday, March 7, 2016

Asterisk and stuff

One of the other fascinations I have is with telephone systems. I have a Cisco 7940, and a 7970 in the house, and I have a Sipgate account for VoIP. It was working fine with one phone, but then I thought I wanted both phones working. SIP is a strange protocol, and is hugely flexible so you can spend happy hours playing with all kinds of things to get it going. The phones are different as well; Cisco rely on having a TFTP server in the network for the phone to boot from, which contains most of the phone configuration. Each phone has a SIP<macaddress>.cnf file in the tftpboot directory that it looks for, to bring up the phone. I had some happy times with Wireshark to find out what was going wrong. Having fixed the 7940, the 7970 uses a similar approach, but a completely different format for the configuration file - now in XML! The phones also have their own web services built in ..

So having the phones working individually, I needed something so I can use them both. There is a lovely bit of Open Source software - Asterisk - that can run on Linux to provide a local PBX solution. So, downloaded that, and it now functions to manage calls coming in and going out on the SIP line.

I then installed Zoiper on all of the mobiles and tablets in the house, and that works well - so I can now call Trish from the office to her mobile, without the call going out over the air - and therefore is free. So far so good.

What I want to do next is to receive incoming calls on the house phone, and send them out to the SIP phones. So, how to solve this?

I did the usual, searched with Google and decided from a ten minute bit of research that the SPA-3000 device, available for pennies from eBay would be a good bet. Ah. Now the real fun begins.

I found the manual online, and there is a very comprehensive Asterisk book for download. I am still struggling though - this is a key part of the home phone strategy, so I can use the existing analogue handsets over DECT to ring them (assuming the phone call is from someone I like - telemarketers will get a very long message advising them that we don't accept unsolicited marketing blah blah on the phone). I will post more as I find out more, but this is a nightmare so far. There are literally hundreds of settings for the SPA-3000.

I may have to sell the little darling and buy a better interface.