TheAncientOne

Stryd's magic wand: Shazam! new sorted thread. Thanks. Apologies for the meander: I am blessed (or maybe the opposite), with a mnemonic memory, which brings things back on cue. Which sometimes makes me a very boring meandering conversationalist.... Mike

A few people on the P3 forum had similar problems. Seems like OLED/PLED has a shorter lifespan that expected in some cases. I wonder how those MP3 players with fancy displays are doing? I got a nice blue negative LCD 4x20 from RS for £11.70 plus VAT. Not the cheapest, but looks nice enough for my MIDIbox monitor, and should stay running. Mike

NO! The MPSA14 is a darlington transistor, which will have a much higher Vcesat than the 2SC type. Typically 1.5V against 0.5V. It may work, but I think you may have problems with reliability. BC337 seems like a common replacement. Hope this helps Mike

I just work with the things too: it looks as if 2.5" is the future, with power consumption at long last becoming an issue. http://www.seagate.com/www/en-us/products/servers/savvio/savvio_10k.1/ I agree about read times on 5400 RPM drives, but unless you're running some serious rig, why is that such a problem for simple audio? Accesss times are not far off a fast drive, and though they can't match the transfer rate of a SATA 2, the real issues for large files are more in the buffering region. BTW. Have you noticed that despite all the speed increases in SATA, a decent SCSI drive still shifts data a whole lot faster. This might change as NCQ drivers actually begin to work as they should. Been up to my neck in speed tests a few months back, building a very fast rig for a photoshop user, and having carte blanche for the photoshop private swap file drive choice. Seagate 15K Ultra 320 SCSI beat out the Raptor 2 by a good margin, but more interestingly, an Intel SCSI card had way better throughput than an Adaptec. The clincher was slightly used drives/cards at a good price. The Raptor was very very good though, and if we'd had to buy a new SCSI card, I'd have gone Raptor instead. A few thoughts anyway. Another one is that Laptop drives are often more shockproof than desktop, so might make sense for a mobile rackmount, (which is where my head was at with this).

They're using them in blade servers...... Mike

That's about right. It would be an SCR, but I've not seen one that's a small chip. HTH MIke

You need to be careful with this one. There used to be a paper on the Seagate site showing that soft mounting could adversely affect access times. Basically the problem is that when the positioner moves, some if it's energy goes to move the drive casing by torque reaction. If the case moves easily, the positioner misses it's target and has to be corrected, slowing the access time down. You can get round this by a two stage mount, hard, then softer. Seagate have re-done their site recently and I can't find it anymore - perhaps it only affected older drives. I weas trying to reduce the racket from a huge bank of SCSI drives in a video studio. Spindle sync made a major difference, (and made stripe access faster), we then decoupled the cabinets from the floor, which was better still. I didn't like to spend too much time in the area though: the whine set my teeth on edge. If your rackmount is only for audio, what about using laptop drives? They are quieter and cooler, but not quite as fast. Mike edited for ypting rerros.

Some off the top of my head ideas about cooling. If you are going for a passive cooler you need to get the heat outside the case, otherwise all you're doing is preading it around inside the box. The system may take longer to get to thermal equilibrium, but once you're there it is still overheated. The alloy strip idea may work, but attaching it to a heatsink fin on the back panel might be better. Basically you can treat heat like a fluid or current flow. Aluminium has a batter thermal conductivity than most chip packages, but you need to encourage the flow from hot to cold - hence the term heat SINK - the thing that removes the heat to the outside world. Remember that dark matt colours absorb/radiate better, so a black heatsink on the outside will move more heat. Drilling holes in your heatsink may increase surce area, but at the expense of cross section so reducing the flow.... better to add some small fins, a thin 'crinkle' layer on top, or mill something out of a bit of scrap alloy. If you go the fan route, then a few tiny fans may be better than one big one. You're looking at the overall Volume of air they can shift. To cut noise you could run them at a lower speed, or make up a little thermal controller. Cold = no fan, warm = fan run at variable speed, overheat = shut down power supply to SID's but leave the fan running. I had a funny job like this once where I had cool a controller in a moulding machine, (the way the machine had been installed meant that the ambient temperature was over 25C). I used some clear plastic panels, duct tape, a bunch on incense sticks, ("Joss Sticks") and a bright light to mess around with ducting made from plastic card, in order to get the airflow over the processor and A->D cards that were giving trouble. It's still running, though I added a thermal switch because they get lazy and don't change the air filters when they should do. Fancy solutions might involve getting hold of some heat pipe (google it). Some fancy 'modders' PC heatsinks use it. Alloy pad on top of the chip, coupled to heat pipe coupled to radiating fins on the case back or base. For cheap temp mesurement, Maplin do a low cost temp guage with a probe, or you can get calibrated bead thermistors which could be rigged to your test meter with a simple voltage reference. I have a cheap thermocouple meter I repaired from some scrap, and an infra red thing (maplin again), though it cost £30. http://www.maplin.co.uk/Module.aspx?ModuleNo=46033&&source=14&doy=3m5. Maplin have a few others temperature probes, but sadly all around £20. If you can't find one locally, perhaps I could airmail you one. (still haven't done the puzzle thing yet). My favourite quick and dirty solution looks like pulling some air through the case, making sure it goes over the chips that need it. If you can get some temp measurement in, then you can look at the more exotic ideas. Hope this helps. Mike

Update on buttons: the guy gave me bad data, they are in fact made by Arcolectric, http://www.arcolectric.co.uk/0916.html. They have leads fitted, the terminals heat shrink insulated, and about 16" (540mm) of 2 core cable spiral wrapped down to an odd two pin plug. Snip off the plug, unwrap the spirap and half the job is done. Offer stands. Mike

Yes, well crowbars are designed to save the expensive electronics, at the cost of a power supply that has gone wrong anyway. A typical 5V rail crowbar will fire at 5.6V. If you look around the 5V output, you may find an SCR, (usually in the same style of package as a voltage reg), wired across from 5V to gound. That would be the crowbar SCR. If you increase the fuse or link it out, then you will likely lose the switching transistor, or the input rectifier diodes. Some switchmodes have a thermistor, (looks like a big disc ceramic cap usually), in series with the live, this is to limit the startup inrush current. A short may blow this, and they are hard to get as spares. If you've replaced parts, and are wary about starting it up again, the series mains bulb trick, (mentioned in the link I gave), is an old fashioned technique that can save you money in power transistors. If you hvae trouble circuit tracing, try putting the PCB, copper side down, on a scanner and doing a big print, you can then 'ghost' in the parts and you are part way there. Best of luck, and again: careful! Mike

SPDT = Single Pole Double Throw SPNO = Single Pole Normally Open SPST = Single Pole Single Throw - Normally Open. Mike

Is this a mains powered switcher? If so be very careful - they have lethal voltages on the board, and can stay charged long after switch off. Major word of advice: make up a dummy test load before any other work - say a BIG 10 Ohm resistor, that way you won't risk frying any of your PIC's or SID's if it all goes wrong. Some switchmodes won't work without a load, by the way. Some have an over voltage crowbar circuit, design to short the output should the voltage go too high, just check you haven't got one set below 9 volts. I have a lot of experience working with things like this, starting with television repairs as a student. Even so, I think twice about working on one, and will only do so if there is no other option. There are some very good guidlines here http://www.eio.com/repairfaq/sam/smpsfaq.htm Once again: be careful. Mike

Done the trick as a tachometer for medium speed. At low speed the stepper produces virtually no output, so the thing 'stalls'. Good use for an old stepper? A polyphase generator for an LED/Supercap torch. Use the recified outputs to charge a supercap, then a little low power switcher to drive the LED. Never buy another battery! There was an article on how to do this in EPE ocober 2000, (though the design is only in a back issue, not on line). I resumed interst in this last month when I saw MTE was using old hard disc brushless motors as bearings for his jog wheels. I thought the same, but the output fails at low speed, sadly, and becomes unreliable. Still punting around the idea of using a field in the coil and detecting the flux change, a bit like a modern motor drive inverter does to sense load, but that would get very complex. Still a nice thought though. Mike

The control surface should be no problem - it's single sided. Just use a decent iron and one of those plunger type solder suckers. If you are right handed, it's best to hold the iron in your left hand, let the solder get well melted then suck it off with the remover in your right hand. If you find that the solder doesn't take up the heat easily, using a small dab of fresh solder makes it easier. You can often 'wiggle' the desoldered pin with a pair of needle nose pliers to make sure it's loose. The double sided board is another problem: more for experts. I have salvaged motherboard 'jungle' chips the way I'll describe, for a vital repair, but it is a nasty job, and has health risks. If you want to get into this, my recommendation is for a heat gun and practise on a few old motherboards first. Trick is to get the solder on the back 'runny' with the heat gun at close range, than give the board a sharp knock, and watch for the shower of chips. Do it over a protected surface! A heatproof glove, (welders or hot handlers Kevlar) is a good idea. Plenty of ventilation too, the fumes from the hot PCB material are not good. Hope this helps Mike

I have a batch of panel mount single pole push buttons, a high quality part made by Rendar(now part of Schurter). They are black, with a chrome fixing nut. They cost me 50p each. If you are interested, drop me a memo, and I'll take a picture, or if you are in the UK/Europe, send you a sample. They have a small wiring 2 core wiring lloom attached - they were parts (unused) for some British Telecom system. Hope this is of use Mike

Some high end test gear uses switchmode, the answer here is a far more complex switchmode, on one hand, or pre-regulate with a switcher, then drop the last few volts across a LDO linear regulator. On the audio side, the noise is not the only factor. The output impedence of the supply has an effect too, which is why some of those Hi-Fi amps have huge toroids and massive banks of capacitors. Power supplies have response time issues too, which is why some of the analogue boys still use LM723 regulators - they stay stable under all sorts of conditions, and don't let nasties like soft synching of oscillators by power supply coupling happen, (there is a well known mod against this for the PAIA 'Fatman' synth). I might hazard that a perfectly good sequencer could use a switchmode, because there is no audio in or out: I have a small good quality switchmode from a backup tape drive that I intend to try in mine. In a multi-SID system, it might be possible to run the PIC's and control surface off a 5V switchmode, and have seperately regulated supplies for the SID's. Another thought about power is to use a seperate supply for the LEDs and backlight, say using an LM317, so that a front panel dimmer pot could be fitted, (and not use the one on the Core board). One thought as well. One failure mode for a switchmode involves it going'off the clock' before blowing the fuse. Fitting a couple of hefty 5.6V zeners across the 5V rail might save your IC's given such a fault, or build a SCR 'crowbar' circuit to protect the valuable chips by blowing the power fuse in the event of an overload. Mike

Was that on the Introspetiv list? I thought I posted about prices from Rapid, and 'BobsBitsBox', on ebay. In short, there weren't anywhere near enough takers on the transistors, and Rapid's prices fro the TL072's is good enough on the number you need for the 9090, without a bulk buy - next quantity would have needed 15 people, for a significant number. If that's it, drop me a memo, and I'll send you the details of my shopping adventures. If it's the 3030, from Oakley, then I will be doing an order for the THAT stuff, if enought people were interested in stuff from that range I'll order in the UK, ortherwise Mouser, can Fedex one over cheaper that the UK importers will do, (basically their min order is 2 plus carriage, and over £6 each at that!). Oh, and I think I found out that the Panasonic exotic op amps are in fact a second source one from Nat Semi. Mike

Great samples! I especially like the very take on 'House of the Rising Sun', (well it sounds like that to me!). Best wishes Mike

My evolution MK-7 mini keyboard does the same, it plugs into the PC joystick/midi port. I think it uses the joystick power common on the soundblaster input plug. As a thought, I've just worked up a design for a stand alone box for it - so it will work as a midi keyboard without being plugged into the PC. Is it worth putting on this on line ? Mike

Not quite: the counter is reset on trigger, and runs until the Q12 output of the counter goes high, which means it cranks out 4K (4096) 8 bit samples, then stops. We could use a 27256, or 27512, and get 8 or 16 x 4K drum samples, or we could use a longer counter, and get say 8 x 8K samples from a 27512. If we went for bigger EPROMS we could increase pro-rata. It might make more sense to use flash ROMs too, they can be pulled out of old motherboards for free and don't need UV erasing. I would simply put some pull up resistors and switches to ground on the remaining unused address lines, allowing binary selection, or use one of those neat binary encoded rotaries or, for a small number wire up a rotary switch to suit. Looking at the resistors in the original converter, we have: 4 x 301 K in parallel = 75.25K 2 x 301 K in parallel = 150.5K 1 x 301K = 301K 2 x 301K in series = 602K 1 x 1M2 = 1200K 2 x 1M2 in series = 2400K 1 x 4M7 = 4700K 2 x 4M7 in series = 9400K Which looks like straight binary to me. Initially, let's try a binary R/2R ladder, then we can upgrade that to a uLaw once we've got a standard device worked out. That's a cool idea. Perhaps a 'bounce' control could be added, if need be, for those that crave those 'synare' effects. @Jaicen I was just going to use 16 resistors, as in the MIDIbox AOUT LC, or the AVRsynth, and get a slightly better binary than the original, which is rather messy. A log law device is just a different bunch of resistors, but might give a better dynamic range. You're right about the dirty/grainy sound. Sounds a lot less sterile. Mike

Don't build it just yet a while. The D->A converter in the design is pretty horrible, and could be better replaced by and R/2R ladder design as in the MIDIbox AOUT LC. I'm definitely going to have a try at that, as well as the simple mod of using more modern (bigger),EPROM, and adding some selector switches to allow different sound in each drum. One thought I've had that one of our more mathematical members might be able to help with: If we did go for a multiple resistor style D->A, then it might be better to work up a logarithmic data model for the samples. This would give better dynamics from 8 bit samples, and could be made as a 'post processor' program taking output from, (say), Audacity. Simplay make your sample loops in audacity, and then process them into the required raw format for the EPROM. Mike

You need a better power supply. It's coming out of regulation, or tripping the current limiter in the regulator. Mike

Not had enough time for a try out yet. Will post details once I get some. Mike

Classic Lateral Thinking Lyle - wonderful! Mike

You've got one vote here: For me, a score proceeds left to right, so the time axis should be horizontal and the pitch axis vertical. This makes graphical sense to me too, and gets closer to a human vision slot as well, not quite golden section at 4:3 but that was good enough for old style TV, Mike