On Mon, 25 Jun 2012, Fred Cisin wrote: Another variant I heard a few years ago: Give a man a fish and he'll eat for a day. Teach a man to fish and he's all, "Bitch, where's my fish?!" :) g. -- Proud owner of F-15C 80-0007 http://www.f15sim.com - The only one of its kind. http://www.diy-cockpits.org/coll - Go Collimated or Go Home. Some people collect things for a hobby. Geeks collect hobbies. ScarletDME - The red hot Data Management Environment A Multi-Value database for the masses, not the classes. http://www.scarletdme.org - Get it _today_! Buying desktop hardware and installing a server OS doesn't make a server-class system any more than sitting in a puddle makes you a duck. [Cipher in a.s.r]

Fred Cisin wrote: Give a man a gun and he can rob a bank. Give a man a bank and he can rob the world.

At 05:46 PM 6/25/2012, you wrote: Outside of a dog, a book is man's best friend. Inside of a dog, it's too dark to read. -Groucho Marx. 867 . [Philosophy]VOCATUS ATQUE NON VOCATUS DEUS ADERIT (Bidden or not bidden, God is present.) --Carl Jung, carved over his front door (and on his tombstone.) NEW: a50mhzham at gmail.com ? N9QQB (amateur radio) "HEY YOU" (loud shouting) ? Second Tops (Set Dancing) ? FIND ME ON FACEBOOK 43? 7' 17.2" N by 88? 6' 28.9" W ? Elevation 815' ? Grid Square EN53wc LAN/Telecom Analyst ? Open-source Dude ? Musician ? Registered Linux User 385531

The second being shorter than the first :-) -tony

I think at some time you may well come across issues with dead capacitors and you may need to diagnose capacitors. I know you can get ESR (effective Series Resistance?) Meters but I wondered how good these were and if any one had any experience of using them. -- Dave Wade G4UGM Illegitimi Non Carborundum

MAybe... My expeireicne is that while capaciors do fail (more so in recent-ish consumer-grade stuff than in the sort of classic computers I noramlyl work on), the 'witch hunt' against elecrrolytic capacitors is unjustified. I tend to divide test equioemnt into 'genral-purpose' and 'specialised'. A multimeter is the former, you will use it for many jobs on just about everythign you fix. An ESR meter is the latetr. It is very useful for fidnign a particualr type of defective component, but it's not something you use all the time. The OP is starting out, so I (and I think others) are suggesting he starts with the gernal-purpose instruemtns mad learns to use those. Then he will have a good idea as to what ESR means, why it's important, and how it coould be measured. It's possible to measure ESR with a sine wave signal generator and a ;cope (You apply a known AC signal to the capcitor under test, look at the currnet thrpough it (voltage drop across a small resistor in series), then resolve the impedance of the cpacitor into in-phase (due to ESR) and quadrature (due to the capacitive reactance) somponents. It gets boring fast, which is why there are ESR meters. Of coruse a good measuring bridge will do it too, which is how I normally measuee ESR.It's slow, but I am not being paid by the hour... There certainly used to be kits for ESR meters available. One of those would be aquite a sensible project. Unliek most test gear you don't need a very ccurate readign for ESR, so calibrating such a meter is not too difficult. -tony

On Jun 28, 2012, at 9:28 PM, Mouse wrote: You're correct in your understanding of ESR; it's basically a measure of how much the cap deviates from an ideal cap. Most ESR meters are designed to measure with short pulses so they don't charge the cap overly much (which is why it's hard to do with a multimeter), and they're usually designed to work in-circuit. Wikipedia's page on ESR meters is a decent writeup. - Dave

Now, I am not a C64 person at all, so these are goign to be genral comments. There are basically 2 ways of determining if a compoennt is bad. One is to remove it from the machine and to test it in your own circuit. The otehr is to see how the machine is mishehaving and to see if the signals coming from a partocualr component are right fgiven what's going into it. Of course in complex circuits the signals goin in might well depend on those coming out (think of a microprocssor, what it does depends on the instructions being fed to it on the data bus),. so it's not always easy. Now, IIRC the 'PLA' is a programmed 82S100 or simular. You can get a data sheet for the unprogrammed part which will tell you the pinuts. It will also tell you waht it conssits of : There are 16 inputs. The programming produces 48 internal signals which are the logical AND of any combination of those 16 inputs and their inverses. For exampe the first term might be I0.I4.I7/.I9 . A second part of the programming defines each of the 8 outputs from the chip as the logical OR of any/all of those48 internal signals. And finally you cna progam it so that each output is either normal or inverted. I believe the C64 PLA programming is available somewhere. So from that you can work out what the states of all 8 outputs should be for each combination of the 16 inputs. That gives the first way to check it. You apply eah combination of inputs in turn and check the outputs. Or more practically you use a computer to do it. The easier way is to test it i nthe C64. You start by seeign if any of the outputs are ever chaning state. If not, i would suspect the IC is bad. Not certain, but certainly a good posibility. If you are getting the otuput changing, I'd us a logic analyer. Trigger on one such output and see what the inputs are doing. Are they right? Or trigger the LA on a combination of inputs that should cause an output to go active. Does that combination ever occru (is the LA being triggered)? If so, is the output changing correctly? As for actualyl replacign the IC, it's a 28 pin DIL device. If you are lucky, it's in a socekt. You then just flip it out with a small screwdriver under each end of the IC, and put a replacement in. Actually being a Commordore, I'd remove the old socket at fit a nice turned-pin one. The problem chould be bad socket contacts. If it's soldered driectly to tyhe board you have 2 options really. One is to carefully desolder all 28 pins with the iron and socler sucker. Then when each pin is free (use a small screwdriver or pliers to wiggle the pin around on both sides of the PCB to break any remaing sodler bond), you pul lthe IC out. Then fit a socket, so it's easier next time. The second option is that if you _know_ the IC is dead, you cut the pins off near the body of the IC (you need some fine end or side cutters for this, which are not cheap!). Then remove the body of the IC and desodler and remove each pin separately. Clean out the holeson the board (melt the solder with an iron o nthe solder side, use the solder sucker on the component side), then fit the socket, etc. AS I hope you've gatehrerd by now, your question, while certainly valid and on-topic, doesn't have a simple answer. There is no magic box that will tell you what to replace. You will end up learning a lot of analogue and digital electronics, and practicing soldering, etc. I don;t think _anyone_ can learn this sort of stuff in a few days. I don;t want to put you off, and I'll certianly help if I can (as will others here), but I am jsut lettign you know what you are gettign into. Yes, I agree. Now, as I said, I am not a C64 person, so I am not going to be the one to help with specifics. But I can tell you how I respond to repair questions on machines I do know about. I do provided directed help. of the form 'check the signal at this point, is it ever changing state'. But I also make sure I explain _why_ you woudl check that signal, what it means, and so on. So I would not simply say 'Look, all you need are the data sheets on all the chips, a book on electronics, and you can figure it out for yourself'. Equlaly I will not say 'Check the signal at pin 3 of U19' 'OK, it's always high'. 'Right, change U27 (74LS02)'. It'll be in the middle, of the form 'Is the processor being held i nthe reset state. We can check that by looking at the signal on pin 6 of U5. Is that high, low, or what?' And so on... -tony