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What are these Parts Inside this Old Compaq Presario CDS 520


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#1 Lxno78

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Posted 14 July 2015 - 05:08 PM

I stumbled upon a post from another forum of a user dismantling an Old Compaq Presario CDS 520 to turn it into a case for his new computer. The user posted some images of the inside of the computer and I was interested in knowing about what some of these internal parts are and how they function.

 

Image 1

 

One thing I noticed was the computer appears to have two boards (and what looks like another tiny one in the back). It had me wondering, is it actually two motherboards? How does something rather old coordinate between the two if it is? Maybe the right side is just a power supply Unit?

 

Image 2

 

That large grey object to the left. In image 1 you can see that it hooks up to the old CRT monitor. The grey thing wouldn't be housing cathode tubes would it?

 

Image 3

and

Image 4

 

The large yellow and black object. I'm wondering if that's a transformer or something?

 

My knowledge in this area is minimal, but I found this pretty interesting, especially comparing the internals of an old computer to that of new computers we see today.


Edited by Lxno78, 14 July 2015 - 05:21 PM.


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#2 gigawert

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Posted 14 July 2015 - 06:08 PM

1. I only see one motherboard, the other side is just parts separate from the mobo.

 

2. It looks like an internal display port thing where you plug in VGA cables, DVI, HDMI, etc.

 

3/4. I'm not sure...


John 3:16

 "God loved the world so much that He gave His uniquely-sired Son, with the result that anyone who believes in Him would never perish but have eternal life."


#3 Chris Cosgrove

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Posted 14 July 2015 - 06:09 PM

Fascinating - I haven't looked inside something like this for years !

 

Your image (1) shows, in the centre, the base of the CRT and the convergence coils and, to the left, with the red cable going into it the line output transformer - that's the gray thing referenced in your image (2). The purpose of the LOPT was to generate several kV - in big TV sets it could reach 20kV - which drew the electrons to the screen.

 

It does NOT house cathode tubes, commonly CRTs. There is only one of these and it is the glass thing that starts at the screen you looked at and reaches back to its end inside that silver grey box with the five orange-ish squares on its top surface. This box houses the circuitry that controlled the electron gun(s) that created the picture. If this is single colour there will be only one electron gun, if it is a colour monitor there will be three.

 

The orange and black thing is the mains transformer, either 110V or 240V, and the components inside the ventilated shroud look like the smoothing capacitors. It almost certainly had a bridge rectified system and these needed substantial (and expensive) capacitors. It is no wonder that switch-mode power supplies took over !

 

A word of warning - if you decide to try and get this working again be very careful. This type of circuitry generates seriously dangerous voltages.

 

As for how it was all connected up, including the data flows, you would need to get your hands on the documentation. The photos are not sufficiently clear to make out such details along with the component identities.

 

Chris Cosgrove



#4 YeahBleeping

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Posted 14 July 2015 - 06:34 PM

Chris obviously knows more about this than I do but after some googling for pictures and what not I would say he is spot on.  The power board circuits on the Right... the CRT circuits on the LEFT and although I cannot see the back in YOUR pictures the Mainboard or motherboard would be housed underneath with the connectors to memory/ 3 1/2 " floppy and the CD Rom drive.  And the back connectors would be:

 

KB   || MOUSE || .. ?? Some kind of external monitor interface maybe?   || Printer LPT port ||     Com Port (Rs232)    || Mic In ||  Headphones || Right Speaker || Left Speaker || Modem (RJ11) Probably 300 or 9600 baud


Edited by YeahBleeping, 14 July 2015 - 06:36 PM.


#5 Lxno78

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Posted 14 July 2015 - 06:45 PM

Thanks all for the information (especially thank you Chris Cosgrove), I was really curious about this. I find it all really fascinating! My friend was looking at this too and wondering about it, I think he will be pretty interested to here this information.

 

Newer computers are cool, but all have a sort-of homogeneous look when it comes to internals, older computers I'm assuming were more varied, which makes it interesting. 

 

P.S.

Those really aren't my pictures (you can find the original thread here from 2007, if you scroll down you will see the links to the images). But I will relate, my first home computer was the Compaq Presario CDS 520, I still have it and last time I checked it still ran. Although that was a few years ago.

 

EDIT:

I brought it out and turned it on. I got it to boot up into MS-DOS, I'm guessing the hard drive didn't hold up to well (It's supposed to have Windows 3.1 with Tabworks shell). However, I do have a Compaq quick restore disk.

 

EDIT 2: 

It worked. I have it running and using Windows 3.1 Tabworks.


Edited by Lxno78, 14 July 2015 - 10:46 PM.


#6 YeahBleeping

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Posted 14 July 2015 - 07:05 PM

My dad still has our Old IBM PCjr with its 4.77 Mhz 64kb of Memory ... on a Cartridge and Basic on a cartridge 300 baud modem on a sidecar .. I spent many many many hours .. playing Zork .. Suspended and Kings Quest and Wizardry 1 & 2 on that sucker. :guitar:



#7 gigawert

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Posted 14 July 2015 - 07:34 PM

My dad still has our Old IBM PCjr with its 4.77 Mhz 64kb of Memory ... on a Cartridge and Basic on a cartridge 300 baud modem on a sidecar .. I spent many many many hours .. playing Zork .. Suspended and Kings Quest and Wizardry 1 & 2 on that sucker. :guitar:

:hysterical:


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#8 Chris Cosgrove

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Posted 15 July 2015 - 06:58 PM

Talk about a trip down memory lane !  Windows 3.1 with DOS 5 or 6.20 and a 16 bit OS - way to go !  Can i come round to your house, I still have a copy of the original version of Doom ?

 

One tip. These things generated a fair amount of heat and do not have forced ventilation like modern computers. Make sure the ventilation slots are kept clear. And as I said above, if you do need to go inside it be very careful of high voltages particularly where that red wire connects to the CRT. Glass CRTs like that could hold very high voltage charges for up to weeks after they were disconnected from the mains.

 

Enjoy playing with it.

 

Chris Cosgrove



#9 PhotoAce

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Posted 20 July 2015 - 04:22 AM

The first computers I worked on had a modified version of Dos 3, that allowed us to use 720K 3.5" floppies, instead of 360K 5". These were Sanyo 550s.

 

We went on to 286 based machines, with MGA and EGA video cards fitted. The EGA card had an adapter board, to allow us to run 3 monochrome composite video monitors. We used the computer to run a point of sale solution for service stations, with up to 3 points of sale, and a back office (the MGA screen.) 


Edited by PhotoAce, 20 July 2015 - 04:25 AM.


#10 mjd420nova

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Posted 20 July 2015 - 10:04 PM

I have yet to understand the design logic (or lack thereof) that put a high voltage flyback and CRT tube inside the same case as the computer logic boards.  Recipe for failure.

I cut my teeth on a four bit processor and machine logic programming.  If you live near a state college, contact them and they may like you to donate the unit to a museum.



#11 Chris Cosgrove

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Posted 24 July 2015 - 08:08 PM

@mjd420nova #10

 

It was the technology of the time, the layout and casing is essentially similar to that of a portable TV of the era. Also while LOPTs failed from time to time I never knew one that failed by arcing dangerous voltages into the rest of the circuitry. Noise interference was potentially a problem since the LOPT and its control circuitry ran at about 15kHz but this was generally fairly well smoothed out. I never had experience with computers of this type but it certainly wasn't a problem on TVs using essentially the same system.

 

Chris Cosgrove



#12 mjd420nova

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Posted 25 July 2015 - 11:50 AM

You may have noticed that most flyback units are mounted in a cage and the susceptible parts were enclosed in a metal shield.  IBM mounted their logic circuits in a metal tray below theCRT display circuits but it wasn't so much the potential for arcing but the huge charge the components had to endure on exposed surfaces.



#13 Chris Cosgrove

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Posted 25 July 2015 - 05:52 PM

My bad - I hadn't noticed where the logic circuitry was.

 

Chris Cosgrove






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