Author Topic: Latest on ebay  (Read 341439 times)

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Offline tjohnson

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Re: Latest on ebay
« Reply #2825 on: 16:54, 29 August 18 »
Wow very expensive postage to uk

Hm, don't remember seeing one of these before!

Sent from my E5823 using Tapatalk


Offline Gryzor

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Re: Latest on ebay
« Reply #2826 on: 16:55, 29 August 18 »
Oh wow, €17 for Greece, too!

Offline dionisisg

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Re: Latest on ebay
« Reply #2827 on: 23:04, 29 August 18 »
And i just found this "refurbished" unit


https://www.ebay.ie/itm/Amstrad-cpc-6128-lecteur-de-disquette/283113180406?hash=item41eadc4cf6:g:uPcAAOSwLMJbXXhx


50euros + 25 euros shipping seem like a lot of money though, with just 11.5 euros more (86,50 total ), someone could get a complete unit and have an extra mainboard for spares


https://www.ebay.co.uk/itm/Amstrad-cpc-6128/273427429320?epid=2156233283&hash=item3fa98b77c8:g:MfkAAOSw~LtbgrMA


edit
correct me if i'm wrong about this, wasn't the Sam Coupe "compatible" with CPCs and Spectrums?, if yes this may potentially work (with a lot of energy drinks and sleepless nights). I am just posting this because i think i read a thread for an CPC ethernet card.


https://www.ebay.co.uk/itm/Trinity-Ethernet-Interface-for-the-SAM-Coupe-Ethernet-SDHC-Mass-Storage/113179479911?hash=item1a5a05cf67:g:4oIAAOSw-jhT-PGq
« Last Edit: 02:22, 30 August 18 by dionisisg »

Offline GUNHED

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Re: Latest on ebay
« Reply #2828 on: 23:34, 29 August 18 »

Hm, don't remember seeing one of these before!


Yeah, right, but I didn't know exactly.
http://futureos.de --> Get the revolutionary FutureOS (Recent update: 2019.08.07)
http://futureos.cpc-live.com/files/LambdaSpeak_RSX_by_TFM.zip --> Get the RSX-ROM for LambdaSpeak :-) (Updated: 2019.08.14)

Offline Bryce

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Re: Latest on ebay
« Reply #2829 on: 14:24, 03 September 18 »
Just spotted this on ebay: https://www.ebay.de/itm/Schneider-Amstrad-CPC-464-PC-Netzteil-Adapter/153162453360

I can't stress how dangerous it would be to use this on a CPC. All fine as long as everything is working ok, but even the smallest of failures would completely torch your CPC beyond repair.

And when you've finished frying your 464, why not try destroying your 6128 aswell: https://www.ebay.de/itm/Schneider-Amstrad-CPC-464-664-6128-PC-Netzteil-Adapter/153162453333

Is the seller a member here?


Bryce.
« Last Edit: 14:32, 03 September 18 by Bryce »

Offline Gryzor

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Re: Latest on ebay
« Reply #2830 on: 14:41, 03 September 18 »
Very useful public service announcement, thanks.


Can you explain a bit more? Why would this solution fry everything at the smallet of failures?

Offline MikeSDK

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Re: Latest on ebay
« Reply #2831 on: 15:04, 03 September 18 »
I would imagine that a PC power supply can crank up the amperage quite severely if one of the regulators inside fails.. which means poofed CPC

Offline Bryce

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Re: Latest on ebay
« Reply #2832 on: 15:06, 03 September 18 »
PC PSUs can supply up to 24A and peaks above 30A on the 5V rail. The traces on the CPC PCB can handle up to about 4A at most. If any part fails to a short/low resistance on the CPC PCB or even an accidental short, the PC PSU will pump all it can through those traces and they will  literally instantly turn to vapour. So the very common "RAM failure with one IC getting warm" is no longer an easy fix, it becomes a non-repairable situation.

Bryce.

@MikeSDK: Correct, except there are no regulators inside a CPC.

Offline MikeSDK

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Re: Latest on ebay
« Reply #2833 on: 15:14, 03 September 18 »
I know, I meant the regulators in the PC PSU :)

Offline Bryce

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Re: Latest on ebay
« Reply #2834 on: 15:30, 03 September 18 »
I know, I meant the regulators in the PC PSU :)

PC PSUs are all Switched Mode Power Supplies, so they don't really have regulators either, just a controller IC with feedback from the output. Which makes them even more scary for the poor CPC.


Bryce.

LambdaMikel

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Re: Latest on ebay
« Reply #2835 on: 00:25, 04 September 18 »
PC PSUs can supply up to 24A and peaks above 30A on the 5V rail. The traces on the CPC PCB can handle up to about 4A at most. If any part fails to a short/low resistance on the CPC PCB or even an accidental short, the PC PSU will pump all it can through those traces and they will  literally instantly turn to vapour. So the very common "RAM failure with one IC getting warm" is no longer an easy fix, it becomes a non-repairable situation.

Bryce.

@MikeSDK: Correct, except there are no regulators inside a CPC.
I have heard that argument a couple of times from you by now, Bryce, and I would like to understand it a bit better. Whereas I would certainly not hook up a PC PSU to the CPC, I know that this is a valid option for Amiga's, for example.

Also, I would fully agree to the "torching" point of view if the PSU were a *constant current* supply that would alsways try to push the current through the circuit / CPC, no matter what, but even a simple PC PSU does not do that, right? The minimal load is 0.3 Amps at 5 V for a standard PC ATX PSU.

In general, I learned that higher amps / current capable PSUs are in general not a problem, because the circuit basically determines the load or how much water = current flows through it, not the PSU (unless it is a constant current PSU, but that's not the case here)... in case of a short circuit, the PSU would probably deliver the max current for a short time before it shuts down, and probably torch the CPC, but a short circuit situation that doesn't happen easily in the CPC, or does it? Just curious - how many examples of toarched CPCs have you repaired from people using inapropriate PSUs?

Just to be clear - I am not questioning your judgment or word of advice / warning here, but it seems that there is disagreement if once googles for discussions on the Web on that topic.

Can you please elaborate a bit on this?

Also, if components fail, I always thought they burn out and have infinte resistance, in what situation does a component fail and have lower resistance?

https://electronics.stackexchange.com/questions/34745/choosing-power-supply-how-to-get-the-voltage-and-current-ratings/34746#34746

Quote from there:
"in that sense, unlike with voltage, the current rating of a power supply must be at least what the device wants but there is no harm in it being higher.  A 9 volt 5 amp supply is a superset of a 9 volt 2 amp supply, for example."

PS I am not the Ebay seller  ;)
« Last Edit: 00:41, 04 September 18 by LambdaMikel »

Offline Bryce

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Re: Latest on ebay
« Reply #2836 on: 10:04, 04 September 18 »
Ok, I'll try to explain it better:

You are correct in saying that a PSU only supplies what the circuit requires. This goes back to ohms law: V(Volts)= I(Current) x R(Resistance) or I=V/R. The resistance of a normally working circuit varies of course as things switch on and off. The voltage needs to be constant, ie: PSUs are designed to keep the voltage at a certain level, but vary the current as the circuit requires. However, a PC PSU is designed to deliver up to possibly 30A. The PSU doesn't know what's connected or how many amps the circuit needs, so the PSU doesn't shutdown just because the CPC is suddenly pulling 25A from it.

What happens is a bit like how a light bulb works. In a short circuit situation, the PCB trace that was made for 4A will first act as a dead short (less a few small resistances at any connection points) and the PC PSU will try to deliver all it can. However, the trace then gets very hot very quickly and its resistance rises. This can cause a situation where the short is now "only" pulling maybe 20A, so the PC PSU will have recovered and happily push out 20A. This trace on the PCB will be extremely hot and whatever part failed too. At 20A the current will jump between signals inside an IC and try to find new paths to GND as it looks for the path of least resistance. This can cause failures all over the PCB.
If you test most PSUs you'll find they generally don't shut down if too many amps are being pulled, instead the voltage will drop, so pulling 5A from a 5V 2A PSU doesn't shut it down, the voltage just drops from 5V to maybe 3V, but as soon as you go back to pulling 2A the voltage rises back to 5V (as long as you don't wait too long).


I have only ever fixed one CPC due to this, but I have fixed many other devices that suffered a similar faith and I've fixed many CPCs that had 12V connected to them which has similar results.

As for component failures, any failed component that's getting hot is because it has failed partially or fully closed, not open circuit. The heat (Watts) is due to increased current P(Watts)=I(Current) x V(Voltage). NP and PN junctions in diodes, transistors and ICs can fail in either state.

If the ebay cable included a 3A inline fuse it would be fine, but it doesn't.


Bryce.

If you want to test this for yourself, try shorting a PC PSU with a length of 10A wire and see what happens. But don't hold it in your hand or do the experiment near anything flamable!

Edit: I should add, that most PC PSUs don't have a fuse on the output, only on the primary side. PC motherboards usually have their own polyfuses on the PCB, something a CPC doesn't have.
For your viewing pleasure, this is usually what you end up with when a circuit shorts and there was nothing there to limit the current:
« Last Edit: 10:32, 04 September 18 by Bryce »

Offline Gryzor

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Re: Latest on ebay
« Reply #2837 on: 18:15, 04 September 18 »
Boy, I was reading that and thinking it would make for a great animated video with some dramatic music and a serious voiceover :D
« Last Edit: 11:08, 05 September 18 by Gryzor »

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Re: Latest on ebay
« Reply #2838 on: 18:50, 04 September 18 »

Thanks for the explanation, I understand and agree with all of that, but I am still wondering how likely (if any) short circuit situations arise in the CPC in the first place. Sure, supplying 12 V is an entirely different story.

In a short circuit situation, the PCB trace that was made for 4A will first act as a dead short (less a few small resistances at any connection points) and the PC PSU will try to deliver all it can.
...
As for component failures, any failed component that's getting hot is because it has failed partially or fully closed, not open circuit. The heat (Watts) is due to increased current P(Watts)=I(Current) x V(Voltage). NP and PN junctions in diodes, transistors and ICs can fail in either state.


So you are saying that aging ICs can have lower resistance and hence can act as short circuits at some point?

LambdaMikel

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Re: Latest on ebay
« Reply #2839 on: 19:08, 04 September 18 »
How about a monster like this:


https://www.amazon.com/PHEVOS-Universal-Switching-Raspberry-Computer/dp/B074YHN8D1/ref=sr_1_3?ie=UTF8&qid=1536077196&sr=8-3&keywords=power+supply+5v

(or the smaller ones from the same line, eg the 5 A one)

This says it has:


- Protection: Shortage Protection, Overload Protection, Over-voltage Protection:115%-135%,Action output cut-off Reset:Auto Reset or fuse. .

That's not good enough either?

Offline VincentGR

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Re: Latest on ebay
« Reply #2840 on: 20:42, 04 September 18 »
Boy, I was reading that and thinking it would make for a great animated video with some dramatic movie and a serious voiceover :D


Yeah, imagine that narrated by Ahoy.

LambdaMikel

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Re: Latest on ebay
« Reply #2841 on: 21:40, 04 September 18 »

Yeah, imagine that narrated by Ahoy.


Roland Ahoy?!  :P ;D :laugh:

Offline Bryce

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Re: Latest on ebay
« Reply #2842 on: 10:01, 05 September 18 »
Thanks for the explanation, I understand and agree with all of that, but I am still wondering how likely (if any) short circuit situations arise in the CPC in the first place. Sure, supplying 12 V is an entirely different story.

So you are saying that aging ICs can have lower resistance and hence can act as short circuits at some point?

Very likely. Almost every CPC I fixed this year failed to a partial short. Like I said, if a failed chip is getting hot, CRTC, RAM, Logic, whatever, then it failed towards a short, not open circuit. Why they actually failed is hard to say. Some things just give up after a while, especially RAM. When this happens with a reasonable PSU, the CPC will try to pull more current, but the PSU can't supply it and the voltage drops below 4.75V and you end up with a black screen or a garbage screen etc. If it is connected to a PSU that can deliver 30A, then it just keeps supplying more until things start melting or go bang.


Bryce.

Offline Gryzor

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Re: Latest on ebay
« Reply #2843 on: 11:09, 05 September 18 »
Very likely. Almost every CPC I fixed this year failed to a partial short. Like I said, if a failed chip is getting hot, CRTC, RAM, Logic, whatever, then it failed towards a short, not open circuit. Why they actually failed is hard to say. Some things just give up after a while, especially RAM. When this happens with a reasonable PSU, the CPC will try to pull more current, but the PSU can't supply it and the voltage drops below 4.75V and you end up with a black screen or a garbage screen etc. If it is connected to a PSU that can deliver 30A, then it just keeps supplying more until things start melting or go bang.


Bryce.



Queue "behind the scenes" documentary epilogue.

Offline Dabz

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Re: Latest on ebay
« Reply #2844 on: 12:55, 08 October 18 »
https://www.ebay.co.uk/itm/123412489581


Unfortunately, mine! :(


Dont seem to have time to use it, nor have the room to plonk it anywhere, so with a heavy heart, I've put all my Amstrad goodies up for grabs.

I did have tons more disks, but for the life of me, I cannot find them, lol, I shoved them away when I got a floppy drive emulator, but there nowhere to be seen, and at todays prices, they were probably worth a billion quid! :/ Grrrrrrr

Dabz
« Last Edit: 12:59, 08 October 18 by Dabz »

Offline Bryce

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Re: Latest on ebay
« Reply #2845 on: 13:18, 08 October 18 »
https://www.ebay.co.uk/itm/123412489581


Unfortunately, mine! :(


Dont seem to have time to use it, nor have the room to plonk it anywhere, so with a heavy heart, I've put all my Amstrad goodies up for grabs.

I did have tons more disks, but for the life of me, I cannot find them, lol, I shoved them away when I got a floppy drive emulator, but there nowhere to be seen, and at todays prices, they were probably worth a billion quid! :/ Grrrrrrr

Dabz
And you don't want foreigners to get their hands on it? Hence you'll only sell to UK buyers?

Bryce.

Offline Dabz

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Re: Latest on ebay
« Reply #2846 on: 13:22, 08 October 18 »
Well, I never thought a foreigner would jump on a boat/plane/cross the channel on a train to collect in person, its a big auld heap of gear! :D


But if someone wishes too, then let me know, I'll take it down, pay me via PayPal and come and get it!  8)


Dabz
« Last Edit: 13:34, 08 October 18 by Dabz »

Offline Bryce

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Re: Latest on ebay
« Reply #2847 on: 13:24, 08 October 18 »
Eh, it doesn't say collection only.

Bryce.

Offline Dabz

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Re: Latest on ebay
« Reply #2848 on: 13:31, 08 October 18 »
Eh, it doesn't say collection only.

Bryce.


It should do, it does here (Attached and highlighted), as well as I've put it in the description


Dabz

Offline Bryce

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Re: Latest on ebay
« Reply #2849 on: 13:39, 08 October 18 »
Interesting. That's not what foreigners see:

Bryce.