Hayling Island

Hayling Island

Wednesday, August 30, 2017

Have a new (to me) motorcycle ..

And she is lovely .. ZZR1100 1995 (D3).
Unfortunately the former owner forgot to tell me about the issue with starting from anything other than cold. It happened to me once on the way back from Southampton on my first outing, but it was really bad the first time over to the Isle of Wight. I bump-started the dang thing five times in one day!  It just clicks when I press the starter .. so I changed the battery (no improvement), changed the starter solenoid (no improvement) so it's on to the starter motor. Since I really need the bike to get to work - especially on the Isle of Wight, I thought I would buy a new one rather than try to refurbish the older one. So I went to a reputable bike bits supplier, and they duly sent one for a rather large lump of money. Part duly arrives, set aside some time this Bank Holiday weekend to do the swap.

I eventually got down to the bit in the bike - removed petrol tank, disconnected battery, removed lower side panel, removed alternator (eventually! had to go and buy a long allen key to get to the bolts required) and then removed the old starter motor. This at least avoided the guidance in the service manual which says Remove Fuel Tank. Remove Carbs. Remove Engine Oil. Remove Engine.

So, out comes the old starter motor and I go to unbox the shiny new one. And, guess what? It is completely the wrong one. The picture in the advert was the correct one, much like the one closer to the camera below. Unfortunately the one further away in the picture is the one they sent. It has the wrong size, wrong fittings, wrong oil seal size and the wrong pinion. *sigh*. 



So I may end up trying to repair old one instead. I have cleaned it all out (it was a big mess inside), checked the armature which seems to be connected in all the right places, and insulated in all of the (different) right places, and I have a kit of bits coming from the very capable Wemoto to replace the brushes and springy things, and I hope for a good result.

Meanwhile, catching the bus and stealing the car from wifey, who is very understanding.

Friday, May 5, 2017

Moving house ..

The laboratory is upping sticks and moving - just as soon as we sell. This does mean that I have had to suspend electronical things for the time being, to sort out the house. Well, my motorbike has needed some attention too. And I did put a new satellite dish on the wall, since Fireball, the house server has moved out of the office downstairs. I thought I would use it to watch TV in the front lounge, (I have a suitable satellite card for it) but I then found there was no satellite signal. Living on Hayling does mean that the air is saturated with salt water sometimes, and the LNB arm had rusted pretty much all of the way through, and wasn't aiming right any more.

No way to sell a house, is it? You need to project the image of a house being taken care of for the prospective new owners.



New dish on the wall.

Monday, February 27, 2017

Fixed amp!

So with a scope available, I had a good look around the Optonica power amp to find out what was going on. It seems that one channel is spitting out so much noise that the protection circuit is tripping, so the speakers are disconnected. (Stock picture, posting from work lol)



I searched everything around the main power amp IC (tsk tsk .. fancy using an integrated amp in a quality product), and eventually came to the conclusion it was faulty. I'd replaced a few caps around the place, but nothing would explain why one channel was all over the place while the other was quiet.

So, I bought a new one from eBay. I had no confidence at all that it would do the job, but you have to accept the improbable, once you have eliminated all of the other possibilities. And it did.

(Picture from the eBay advert I bid on). 



Monday, February 13, 2017

Fixed Scope!

The power supply issue on the HP 54502A eventually succumbed to my repair type ministrations.

I had found a bunch of capacitors in the ageing power supply that needed replacement. 12 in all, all 2200uf 35v that I bought a bulk of Panasonic replacements for. That, and a test load brought the power supply back to something that worked a bit, for a while.

The thing with SMPS is that they are a nest of feedback loops. Especially early ones like this, using discrete componentry. After having reminded myself of what a UJT oscillator looks like, I found that the feedback for the +5v from secondary to primary was way out of whack.

That took me to a circuit in the secondary that compared the +5v and the -5v rail in a long tailed pair. -5V being generated by a linear regulator from the -12v, itself a linear regulator off a separate secondary.

Trouble is, with all this feedback going on, the secondary outputs all look wrong, so how to find out what was working? The trick in the end turned out to be switch on, run down all of the outputs to see if they start off ok or not. And guess what? The -12v that fed the -5v that was compared to the +5v to drive the feedback to the oscillator never got bigger than -6v.

So I drove the -12v regulator from an external 15v power supply, to see if it worked by itself. Still faulty! Getting warmer .. but it is only a few components. Swapped all the capacitors. No change. Measured resistors (by probing them near the body from the top) no problems. Hmm ...

Then noticed some burning or black stuff on one leg of two resistors - near the big capacitors on the 5v I had replaced. I hadn't noticed that one of the caps had leaked. I removed the resistors, used a Dremel to remove the black stuff and clean up the PCB as much as possible, replaced the resistors ..

Nothing happened. But all of the rails look like they are at the correct voltages?
And then noticed I had removed the connection to the CRT while working on it, and hadn't put it back. Tried again ..

Friday, January 27, 2017

Class B DIY

I thought I would finally get around to building the amps from the bits that I bought a long time ago.

I came across the pages at Elliott Sound Productions a long time ago, and since I am no good at designing analogue electronics beyond an emitter follower or a long-tailed pair, I bought the components. I filed them safely in a box, and forgot about them.

More recently, I thought it would be fun to exercise some layout skills and engage my friends at Itead Studios in creating a small PCB.

So I am sure that Mr Elliott won't mind me showing the results of this small bit of labour. It's his design, just I didn't buy one of his PCBs - I thought it would be fun to try my own. I am going to build five of them, after all - two for the Studio, where the reference monitor is currently running on an ageing Cambridge P60; one as a test amp for the laboratory, and two in bridge mode for a subwoofer project, to drive a Peerless 850140 10 inch driver I bought 17 years ago from Wilmslow Audio. I've been buying little bits and pieces from them for more than 40 years.

Now if only I could lay my hands on the heatsink I put aside for this project when I was young ..



  

The first prototype board. I couldn't find any BC546A in the lab, but I did find some MPSA42. They're high voltage NPN transistors so they will be fine. The pinout is opposite to BC546A so they are in backwards compared to the silk screen. 

PS: I have a handful of the blank boards left over; if anyone would like one or two, please drop me a line via Google, and we can arrange for them to be sent. 



Saturday, January 7, 2017

Making progress again ..

The Dell machine arrived. After much faffing around trying to get Windows 98SE running on it (it's a pig, it can't find all of the device drivers for the network etc), I decided to go for a simpler solution. I found this FreeDOS thing, which at first sight seemed to be ideal.

So, I downloaded FreeDOS onto a bootable CD, booted the machine with that and created a 2GB (cuz that's how big a normal DOS partition could be) partition.

I then installed Linux on the beast, running dual boot so I could get the machine on the network, and copied over the files from the Fireball server on to the DOS partition. (Linux can write FAT file systems, you know).

I then ran FreeDOS up, so I could try to run LIFUTIL - and was shocked to find it works. Now all I had to do was to find a 720K diskette, format it in LIF format, and then put the right driver for the 1GSa/s card on. I went through all the files, and eventually found that the SYSTEM_0.13 file was the correct one (by a process of hex editing the files and looking for the description string), put that on the disk and moved it over to the HP 16500A front drive.

Wow. We have a working scope.