wintermute

OK so I've been a bit slack getting to the second instalment. I actually finished the last coil about three weeks ago and have made the crossovers.

Tip number 1. Wear Gloves!! After the first coil my fingers were killing me. I'd pulled back the skin on my fingertips so hard that it was coming away from under the fingernails. Ouch!!! The gloves I subsequently wore were just normal rubber dish washing gloves. These worked quite well because they allowed me to put tension on the wire (holding the spool) and I no longer got sore fingers

Tip number 2. If you can make the same value with different size formers, choose the one with the lesser turns per layer. My pancake coils were much easier to make than the taller ones.

I think that the reason for tip 2 is that the more turns per layer, the more chance that small kinks in the winding wire will add up to enough to make it hard to get the last turn on for any particular layer. The coils...

Wind my own coils, yeah why not, how hard could it be? Well if you are as much a perfectionist as I can sometimes be, pretty damn hard!!!

I suspect it would actually have been a whole lot easier if I'd not obsessed about getting a low DCR for my coils, and gone with a smaller gauge wire. As it turns out I was (obsessive), and decided to use 1.6mm (~14 AWG) wire.

I originally had thoughts of measuring off the length I needed, clamping one end in a vice and slowly turning the former (in my hands) until I wound it all on, luckily that Idea didn't last very long and I started to think about making a winding jig.

I hit google and saw some pretty fancy jigs, motorised with clutches, speed control, turn counters, that all looked too hard, so I thought about what I actually needed. Georges Transformer winding jig was in the back of my mind too, which gave some inspiration as well

The pictures below are what I came up with. I had...

So I have almost all of the parts (yeah I know) for my YARPS power supply. As part of the order I got myself a prototyping breadboard.

I've knocked up one half of the yarps power supply, ie the positive side, and hooked it up to my old model railroad transformer which has a 15V output.

Parts still to be ordered are the dual secondary 15V transformer and some 50K trim pots. However I had enough to make one side of the dual rail supply.

It didn't smoke, and the CRCRC part of the PS works very nicely Pics attached at the end.

I need to do a further test with BC560c's with different HFE's to see whether this affects the output voltage (my suspicion is that it will). I put a 36K resistor (which I had at hand) in place of the 50K pot and only got 8.6V even though spice said I should get 9.13V with that value resistor so something isn't working as per the sim, the use of a pot certainly seems to be required to get the desired voltage...

It seems I have been doomed to not do any of my DIY projects since my main computers hard drive crashed followed shortly after by my laptops (the laptop has had another crash after that, and the drive is now on the way out again!!)

After having to pull the cables out of my chipamp last week and plug the TV into it (because the MythTV box refused to play a DVD and I can't plug the DV18 DVD player direct to the chipamp because it has no volume control) I decided I had better get off my backside and finish my pre/active crossover. I had to do it again tonight as well (plug the tv into the chipamp), sigh...

This is all because my playmaster had something in the pre die again and is only working on one channel and I just haven't been bothered fixing it. I thought that being inconvenienced might make me more likely to finish the other projects but it has been broken for about 6 months

So on Monday I decided that I should re-install Holm-Impulse...

Well I said no more excuses, and I for the most part started to make some progress. But good old Murphy stepped in and threw a spanner in the works.

The Boot Drive on my main computer decided to die on me, I've got backups of all the important stuff so no big deal other than the inconvenience. I could always use my work laptop... step in Murphy again, it too decided to die... once again have backups but all of a sudden nothing to run LT spice on, bring up my Plans, test data or anything.. I've got a loan one but I'm not going to set it up for a couple of weeks only.

So since my main computer was nearly 8 years old (single core Athlon 2000 which is really only 1667Mhz) I decided an upgrade was in order... This would probably have been a relatively modest machine if it weren't for my recent discovery of LTSpice and the knowledge that it takes a lot of cpu grunt, and that it benefits from multiple cores!!

So What have I been doing? Not working...