Author Topic: Sirius631, an introduction.  (Read 726 times)

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Offline sirius631

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Sirius631, an introduction.
« on: 16:08, 18 March 18 »

Hello everyone, and thank you to the admin for accepting my application to join.


My name is David, I'm 50 and I'm a former automotive design engineer. Although I'm pretending to be a writer right now (unpublished teen fiction at 75000 words long) it's not making me any money. One lives in hope.


My computing history starts with our family getting a Camputers Lynx 48. Although I liked that computer, the crappy TV sets that my dad got for us to us it on kept failing, meaning I didn't get much time with it. That company soon went bang, and that prompted my parents to go for something better: our first Amstrad CPC464. Apart from typing in magazine programs, I created a few programs in BASIC that were useful to me. When I was 18, I took on organising an event for my cycle club, and wrote a program that could rank rider by their previous performances, sort them into a starting order and print out address labels, so that they could be posted their start sheets. One sort took all day in BASIC, so I learned some machine code and swapped in some new m/c routines. The sorts ended up taking about ten minutes.


When I went to college, I took the CPC with me, to write my notes and reports on TASWORD, for them to be printed out on an Epson HR5 dot matrix printer. Part of my final project involved the specification and construction of a PC for CAD work. We were given student copies of WordStar for the PC by college, and it became easy to write reports on that and print them out onto the quality printers on campus. After that, I had no need for the CPC, so it went back to my dad.


Dad kidded himself that he was learning about computers when he was only playing games. Still it kept his interest alive when the monitor went bang. Rather than abandoning the CPC, he bough another one second hand, to replace the monitor. . Eventually my dad's interest in the CPC did wain, due to the greater word processor capability of the PCW and later PCs which he acquired. The CPCs went up in the loft, along with the Epson, and the floppy disc drive that I had bought. Thinking that I'd never use my CPC firmware manual again, I sold it off, along with all the technical books I had on the Z80.


When Dad passed away, Mum wanted help to clear all the junk that he'd accumulated. (The garage and loft were packed) I slowly worked my way through it, selling some stuff, donating some other. I finally came across the CPCs the back end of last year. I took them home to see if I could get them to work. Both of them powered up with the monitor, but our original CPC had keys that didn't work.
The main unit of the second one had a broken number 2 key, although you could poke through the hole with something to bring up the character, and the tape drive didn't work.
I took the first unit apart, cleaned the keyboard's PCB with isopropanol, put it back together and retested it. All the keys worked then, and the tape deck worked fine too, both loading and recording. The printer and disc drive interfaces were a different matter. I got a bit more serious, cleaning the edge connector contacts with wet-n-dry paper before wiping with isopropanol. After that, I could print to the old HR5, and run discs without a hitch.
I decided that the second CPC needed a donor unit to replace the broken key, however I didn't appreciate the difference between CPC models, and bought one on eBay with an incompatible keyboard and main PCB. This third CPC had a more serious cassette failure than number two, in that its idler wheel had a split tyre, whereas number 2 just had a broken drive belt. Not fancying the deconstruction work on number 3's cassette, I took its drive belt, put it into number 2's cassette mechanism, and put the whole mechanism, together with electronics, switch and volume control into number 3. I then gave number 3 the full test run with printer and disc drive before posting it for sale on eBay. I also included the original monitor, as I had plans to make a SCART lead.
More adventures to come, but for now, I need a coffee.
« Last Edit: 16:11, 18 March 18 by sirius631 »

Offline sirius631

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Re: Sirius631, an introduction.
« Reply #1 on: 17:53, 18 March 18 »


I've finished my coffee, but I want another one. I think I'd better switch to decaf.


Anyhow. Having determined that buying non-working CPCs was the cheapest way to go, I bought a replacement third unit, which I'm calling 3b. By the eBay photo, it had been kept in damp conditions (mildew on keys) and the cassette's FF key was broken. This photo must have put other people off, for I snapped it up for £12. Although the keys had been cleaned before I picked it up, when I opened it up I found it was in a terrible state, so much so that I popped out the two removable ICs (it was a later generation with the compact PCB) and actually washed the PCB with warm water and a scrubbing brush (yes, it is safe. There was no electricity and the ICs are hermetically sealed).


I put the PCB back in the case, and started to work on the keyboard. I popped all the key caps off and put them to soak in Flash. The metal plate under the keys was matted with hair and dust. Honestly, it looked like a fusion of barber shop floor and cement works. It had even got between the membrane and the back plate. The membrane got a good wash too, although I was gentler with it than I had been with the metal plate. Eventually, everything dried out and I put it back together loosely.


Before I could test anything further, I had to source a new power supply and SCART lead. Even though I've built 5v power pack in the past, I didn't have the components to build one capable of 2 amps. Fortunately, years before I had salvaged the power pack from the Lynx, for use with my electronics experimentation, so I found the right power adaptor plug and soldered that in place.. I had the bits to make a CPC monitor to SCART lead, and found various schematics for the job. My plasma TV is a bit old, so didn't recognise the RGB, so I needed a +5v line into the SCART plug. I can't remember my thinking now, but I didn't want to splice a power lead into the SCART lead, and hit upon another solution, Since I didn't need the centre DIN pin from the Amstrad to carry the composite signal, I de-soldered the two resistors that connected to it, and soldered a wire from a PCB thru hole which carried +5v to the expansion connector to the centre monitor pin.


Time to power up: nothing. I jiggled the plug and switch, and got intermittent flashes of the LED. What I had felt when jiggling things was that the power socket was loose. When washing the board I had seen a mod wire, indicating a repair to a broken +5v PCB track. Unscrewing the PCB again revealed a cold solder joint to the 0v terminal. I whipped out the soldering iron again, made good the 0v connection and screwed the PCB back into place. I tried the power again: nothing, but this time it was absolutely nothing. I had something before, so I suspected the switch, having read how they could be dodgy. This I confirmed with a multimeter. I knew the switch on the left-over cassette unit from 3a was good, so I salvaged that and soldered it in in 3b,


I screwed things back together (rather impetuously, I know) and powered up again,
.
.
.
.
.


.
 ;D
Time for my happy bunny dance.



Now that I had a living 464, it was time for cassette surgery. As
I tried to remove 3b's cassette unit I noticed that the counter reset push had got whacked, and was jammed
in the case. A quick tug broke it off, destroying the counter mechanism. That was no problem, as I had a spare one of those from 3a as well. Swapping the counter and the keys was simplicity in itself, However, when I put it back together, powered it up (happy bunny dance again, just because I felt like it) and tried to load my test cassette, nothing moved.  :'(


I took the cassette right out and checked it over, visually. The symptom was the same as the split idler wheel tyre from 3a, but the tyre on 3b was intact. I tried all the keys, and watched everything move. Aaaah. One cog didn't move into place correctly when the play button was pressed. I tried the play key a number of times, and as I did, a whole load of grot began to drop out of the mechanism. CO2 spray duster time. I took it outside and spray-dusted it as I worked the keys. After a while the grot stopped coming out, which was good because I was losing the will to live.


Back inside, I reassembled the CPC, powered it up and commanded it to RUN".
.
.
.
.
.
 ;D

More to come.
« Last Edit: 18:34, 18 March 18 by sirius631 »

Offline mr_lou

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Re: Sirius631, an introduction.
« Reply #2 on: 19:23, 18 March 18 »
Welcome aboard!

An author, eh?  :)

So when will you start authoring an issue of 8-bit Memoirs?  ;)

Offline Zoe Robinson

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Re: Sirius631, an introduction.
« Reply #3 on: 19:42, 18 March 18 »
Welcome aboard!


It sounds like you're going to fit right in here. :)

Offline CPC_Fan

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Re: Sirius631, an introduction.
« Reply #4 on: 13:16, 19 March 18 »
Hi and welcome to the forum David. Glad to hear that you are slowly but surely making progress with your 464's. Keep up the good work and please keep the updates coming. They are a very enjoyable read.

Offline Skunkfish

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Re: Sirius631, an introduction.
« Reply #5 on: 13:35, 19 March 18 »
Welcome David, eagerly awaiting the next chapter of your CPC adventures!

Offline sirius631

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Re: Sirius631, an introduction.
« Reply #6 on: 13:46, 19 March 18 »

I had number 4 sitting upstairs, awaiting testing, but I don't want to mod that in the same way as I've mod'ed 3b. I'll wait until I have the bits to make a powered CPC to SCART lead, so that I'll have something I can sell on as fully tested, if it's as good as I think. I'm thinking a CPC to VGA lead could be possible, which would be handy since I've got a spare 4:3 ratio VGA monitor. I've seen a SCART to VGA lead, which required some electronics, so I'm wondering if I can run the CPC into the VGA and skip the SCART bit. Considering that the point behind the CPC monitor was to stop it taking up the family telly, I think it's worth considering.


I would already have number 5, but one purchase never arrived from eBay. Having read the seller's feedback I get the feeling that he never posted it. Her was a major flake anyway, in my books. I got a refund this morning, but that's poor consolation. I don't think I'll get a bargain like that again soon.


Anyway, I'm picking a new number 5 up tonight. The seller put a £25 buy it now price up, so I thought I'll have that. The description made it sound like it was seriously dead, as in a dead custom chip kind of way, but further communication with the seller makes me think that it's just a monitor power issue. I'll have the monitor too, but I'll need more skills to fix that without frying myself.
« Last Edit: 13:49, 19 March 18 by sirius631 »

Offline tjohnson

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Re: Sirius631, an introduction.
« Reply #7 on: 15:38, 19 March 18 »
I'm thinking a CPC to VGA lead could be possible, which would be handy since I've got a spare 4:3 ratio VGA monitor. I've seen a SCART to VGA lead, which required some electronics, so I'm wondering if I can run the CPC into the VGA and skip the SCART bit.

Hi David, Sounds like you are having lost of fun saving broken CPCs.   On the VGA cable I think the issue you'll run into is finding a monitor that can run the 15hz signal, alot or the majority can't so you'll end up out of range on most monitors as this was more common on televisions.  Early VGA, with 9 pin connectors mostly, may accept the signal from what I understand.

Offline sirius631

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Re: Sirius631, an introduction.
« Reply #8 on: 12:27, 20 March 18 »

I was right, number 5 is deader than a dead thing. On the plus side, it came with 2.5A +5v power pack and a SCART lead that works without the added power feed (I'll open that up and see how they did it). A second plus, with having the power pack and SCART I've been able to test number 4. It powers up and operates fine, except for the counter reset push being missing.


The plan now is to give number 4 a full test with printer and disc drive, and clean the edge connectors if needs be. I'll source a new counter before selling it.


Number 5 I'll use as a sacrificial unit to rebuild number 2, but not before popping the custom chip into number two, to see if that is dead. If I'm right, number 5 is the earliest machine I have, as it's a type 'A' motherboard with no heatsink for the custom chip. The memories are also soldered in, if I remember the eBay photo correctly. I'll be opening it up anyway, so I'll find the truth on that later.
« Last Edit: 12:30, 20 March 18 by sirius631 »

Offline keith56

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Re: Sirius631, an introduction.
« Reply #9 on: 12:32, 20 March 18 »
Welcome to the forum! Hope you're enjoying all those CPC's

I have my CPC connected to a regular vga monitor with one of these arcade converters


https://www.amazon.co.uk/Mcbazel-Arcade-Converter-Monitor-Projector/dp/B078ZDTLBJ/ref=sr_1_1?ie=UTF8&qid=1521541863&sr=8-1&keywords=vga+arcade

May be worth a look!
Chibi Akuma(s) Comedy-Horror 8-bit Bullet Hell shooter for CPC - http://www.chibiakumas.com
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Offline sirius631

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Re: Sirius631, an introduction.
« Reply #10 on: 20:37, 20 March 18 »


May be worth a look!


Interesting, but the big question is why is  Chibi is in hiragana under your icon and yet it's in katakana in your footer?  ;D

Offline sirius631

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Re: Sirius631, an introduction.
« Reply #11 on: 21:23, 20 March 18 »

I'm wrong about number 5 being the older machine. There is evidence of the heat sink having been in place at one time (heat sink compound over socket), and the keyboard/main board combination is the second gen. Anyway, it's not the custom chip nor the processor at fault; they both worked fine when plugged into number 2 machine. I've got many 4164 dynamic RAM chips about, so I might de-solder those in number 5 and see if new RAM helps. It's a pity the ROM is soldered in, as that would have been an easy borrow from number 2.


I've got all of number 5's keys off and soaking in a jug with bicarb. The Flash hardly touched the grime on the blue enter keys. The plan is rebuild number 2 with the spare parts taken from number 5. Unfortunately I'll still be short of a counter for number 4.


I'm wondering if the excess heat paste on the custom chip socket of number 5 is causing a loss of connection. There may be no adequate way to clean it out of the socket contacts.

Offline Vyper68

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Re: Sirius631, an introduction.
« Reply #12 on: 00:45, 21 March 18 »
Welcome aboard,
I have not been here very long myself but everyone is very friendly and will always help with any problems you come across. Interesting you had a Camputers Lynx, i used to have a 96KB Lynx back in the 80's but it was stolen when our first house was burgled a long time ago. I did quite like it and it's quirky nature was a bit endearing but there was next to no software for it and the games were all mediocre. They go for ridiculous money on eBay these days as well.

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Offline keith56

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Re: Sirius631, an introduction.
« Reply #13 on: 00:46, 21 March 18 »
Interesting, but the big question is why is  Chibi is in hiragana under your icon and yet it's in katakana in your footer?  ;D
Search engine optimization! My website ranks differently depending on how you search for the name in japanese!
Chibi Akuma(s) Comedy-Horror 8-bit Bullet Hell shooter for CPC - http://www.chibiakumas.com
「チビ悪魔」可笑しいゴシックSTG: http://www.chibiakuma.com
Learn Z80 Assembly programming for CPC,Speccy,MSX + More with my Text+Videos Tutorials:http://www.chibiakumas.com/z80/

Offline sirius631

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Re: Sirius631, an introduction.
« Reply #14 on: 20:59, 22 March 18 »

Having fully refitted number 2, I gave it a full test today and it passed on everything. Now there is nothing left to do but put it on eBay and let it help pay to rescue more neglected orphans.


I hadn't looked at number 5's monitor until today. By the seller's description was in a non-functional state, with not even +5v out. However, I got a multimeter on the job and found that it was indeed giving a health +5v, so I plugged it into number 2, and lo and behold, it gave a beautiful full colour output. I had sold my original monitor along with 3a, but I think I'll hang onto this one for a while, until I can modify the SCART lead that came with number 5 to be a powered lead. I've heard horror stories of unpowered leads causing ULAs to overheat. Also, it gives a shadowed effect to the test on the welcome screen. I don't have that problem with 3b, but it would be best if I can un-mod it and use a standard cable.
« Last Edit: 21:09, 22 March 18 by sirius631 »

Offline sirius631

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Re: Sirius631, an introduction.
« Reply #15 on: 20:38, 27 March 18 »

The monitor from number 5 isn't as healthy is I'd hoped. It's hit or miss whether I get power out of it, so I'm using the power pack that I got with number 5 whilst still using the monitor for display. Some time I'll get to investigate further, but monitors are not my focus.


As for the main number 5 unit, I've soldered in a new socket for the ULA and new 4164 DRAM. I noticed that the DRAM in it were very slow speed 25/26ns as opposed to 15ns, also they were mixed so they must have been subject of replacement at some time. I'll have to replace the ceramic caps as well, as they got a little scorched when removing the DRAM.


I had suspected the 7400 inverter in the chrystal circuit, but have discounted that by use of the frequency function on my multimeter. The generated 16MHz is spot on, as is the 4Mhz from the ULA to the Z80. I'm actually a bit confused on this point, as I had read somewhere that the Amstrad clock signal was actually de-rated to 3.something MHz. I know you can tune chrystals by the use of capacitors, but I'll have to find the reference again to be sure.


Number 4 has been full cleaned and is back together. The cassette deck hadn't worked in play/record mode, and I was going to swap in the deck from number 5, but I found that someone had put the contacts of one of the bare switches on the wrong side of an actuating bar, which meant that the contacts never made contact. I even repaired the cassette pause key on it, even though I can't think of a logical use for such a thing on a computer that controls the play and record functions via a relay. Personally, I would have deleted it in a cost-down exercise.


I have number 6 on the way. It was advertised on a "Buy it Now" at £17-something, so I jumped at it. It was listed as being without the ability to power on, so I'm guessing a dirty switch again, just like 3b when it came to me. I also have my eye on number 7, but that will be for after Easter.


Number 2 sells tonight. It is sat, already parcelled up, waiting to go. I keen to see what I get for it.

Offline sirius631

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Re: Sirius631, an introduction.
« Reply #16 on: 09:38, 04 April 18 »

I received number 6 yesterday, so I plugged it into the monitor and fired it up. It works fine, even loading from cassette. There is a small amount of physical damage to the case, the edge connectors are dirty, preventing the disc from operating, and I think the bits for the pause key are rattling around inside.


Plan for today: open up number 6 and see if I can repair the pause key, clean its edge connectors and swap the upper case with that from number 5.


My test routine is a little stalled at the moment, as the original power pack on my Epson HR5 has died. I would have tried to repair it but it's been fully encapsulated in gunk. I obviously wasn't having a good day that day as the multi-volt SMPS I found to replace the HR5s had a capacitor go up in smoke as I plugged it in. I don't have any 400v rated caps to hand, and Maplin didn't stock them (which is part of why they are going out of business), so I'll have to order that from Farnell. I have other capacitor issues on other non-CPC projects, so I can see myself being busy.

Offline Gryzor

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Re: Sirius631, an introduction.
« Reply #17 on: 20:57, 06 April 18 »
A big welcome from me, @sirius631 , and thanks for sharing your adventures :)

Offline sirius631

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Re: Sirius631, an introduction.
« Reply #18 on: 11:41, 07 April 18 »

I was right about the pause key on number 6. All the bits were floating around in the case. So, after a bit of fiddling around with the small bits, the pause on number 6 works fine. However, it failed to power up when I put it back together and found that the switch had lost continuity. I tried it a few times, jiggling it a bit as I did, but no dice. I de-soldered it and opened it up, expecting to find dirty contacts, but no, the contacts were clean, but they were awash with a greasy fluid. WTF? Even though I tried to soak it up, the contacts must have still been contaminated, so I ended up soldering the switch from number 5 into place, as I knew that to be good.


On the number 5 front, I've had a look over the board with a high power magnifier, but I cannot see any corroded or broken tracks. I don't want to think that it's a chip or other component failure, as my fault finding skilled would be over-taxed at that. I have already eliminated the CPU and custom chip as the problem, and I've replaced the RAM. I so do not want to de-solder any more chips. I think I'll replace the only electrolytic capacitor on the board, because that's a good idea anyway, before settling down with a circuit diagram and my continuity tester.