Discharging capacitors, PSU-testing with dummy loads

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Pacman
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Re: Discharging capacitors, PSU-testing with dummy loads

Post by Pacman » Fri Oct 13, 2017 6:34 am

A quick report as to what happened after recapping the Mega STe PSU...

Using the dummy load resistors I quickly checked for each output rail and they were fine. Approx. the same values as before if I recall correctly, so I attached it to the computer and what do you know, the display output looked a whole lot better! The picture was "stronger" meaning more contrasty, perhaps even a little sharper looking. The white in the monochome display now looks more white (not slightly grayish as before), so I must have done something right by recapping the power supply :D

Time permitting I'll post a "how I did it" here.
Mega STe | MonSTer with dual IDE-CF memory card adapter | STe | SM-144 |NEC Multisync 1990SXi | IDE doubler | ST_ESSC | RSVE | ICD Link II | Link '97 | HD floppy drive/AJAX | HD floppy module | Minolta PCMCIA card-drive | Realtime Clock module | Discovery cartridge | Unitor-2 | Export | Combiner | Steady Eye | Human Touch | Unicorn USB

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Re: Discharging capacitors, PSU-testing with dummy loads

Post by exxos » Fri Oct 13, 2017 8:39 pm

Pacman wrote:
Fri Oct 13, 2017 6:34 am
so I attached it to the computer and what do you know, the display output looked a whole lot better! The picture was "stronger" meaning more contrasty, perhaps even a little sharper looking. The white in the monochome display now looks more white (not slightly grayish as before), so I must have done something right by recapping the power supply :D

Fantastic news :bravo:

Yes it just goes to show that looking after the equipment has its rewards :)
Pacman wrote:
Fri Oct 13, 2017 6:34 am
Time permitting I'll post a "how I did it" here.

That would be good, as nobody yet has done any guides or anything about things, other than what I posted on my website of course which is just the basic information no guides or anything.

Saying that, I did acquire a box load of the MSTE/TT power supplies a few weeks ago, they are all un-tested, but at some point I will test them and add them to my store. I will also do a guide as well, but I probably won't get chance to do this until next year now.
4MB STFM 1.44 FD- VELOCE+ 020 STE - 4MB STE 32MHz - STFM 16MHz - STM - MEGA ST - Falcon 030 CT60 - Atari 2600 - Atari 7800 - Gigafile - SD Floppy Emulator - PeST - HxC - CosmosEx - Ultrasatan - various clutter

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Re: Discharging capacitors, PSU-testing with dummy loads

Post by Pacman » Fri Oct 13, 2017 8:54 pm

Thanks!
Yes indeed, maintaining and looking after these dinosaurs sure has its rewards ...sooner or later!

You've already done several very nice guides, so this will be more of a "practical" guide on how I recapped the PSU, not explaining how it works etc.
I'll try to get it done sometime soon.
Mega STe | MonSTer with dual IDE-CF memory card adapter | STe | SM-144 |NEC Multisync 1990SXi | IDE doubler | ST_ESSC | RSVE | ICD Link II | Link '97 | HD floppy drive/AJAX | HD floppy module | Minolta PCMCIA card-drive | Realtime Clock module | Discovery cartridge | Unitor-2 | Export | Combiner | Steady Eye | Human Touch | Unicorn USB

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Re: Discharging capacitors, PSU-testing with dummy loads

Post by exxos » Fri Oct 13, 2017 9:13 pm

Pacman wrote:
Fri Oct 13, 2017 8:54 pm
You've already done several very nice guides, so this will be more of a "practical" guide on how I recapped the PSU, not explaining how it works etc.
I'll try to get it done sometime soon.
I think it helps anyway for people other than myself to write these guides, at least from a more user's point of view of things. Of course all this electronic stuff I have been doing for around 25 years now. Stripping down something repairing and upgrading I could probably do in my sleep.

Though I also remember back in my younger days, trying to follow guides various electronic kits and things confused the hell out of me. Simply changing a transistor would be a week-long epic. So of course it does always help to have guides written by people who have actually gone through the upgrade steps as the problems and questions are more apparent to users than they are to myself.

I probably miss a lot of details out what I write my guides, but a lot of the time I mostly in a huge hurry trying to do a million things at once, so a lot of things do get greatly summarise which may ultimately confuse some people about some things. I do update my website when I get chance, as I do get emails by some people who get confused over what I have written, so things do get updated and amended over time to make it easier for people in the future :)
4MB STFM 1.44 FD- VELOCE+ 020 STE - 4MB STE 32MHz - STFM 16MHz - STM - MEGA ST - Falcon 030 CT60 - Atari 2600 - Atari 7800 - Gigafile - SD Floppy Emulator - PeST - HxC - CosmosEx - Ultrasatan - various clutter

https://www.exxoshost.co.uk/atari/ All my hardware guides - mods - games - STOS
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Re: Discharging capacitors, PSU-testing with dummy loads

Post by Pacman » Mon Oct 16, 2017 1:44 am

We all have our own perspective on things, and the great thing about these forums is that we can all share what we know. I'm in the midst of writing it now and will link to several of your postings which I think will, in total, give a more complete picture of what it's all about :)

One quick question: regarding the power supply dummy load resistors valued at 10 Ohms and 2.2 Ohms: how many watts are they?
The markings are a bit cryptic:

218-9 10R
202-7 5%M

and:

CGS SBCHE15
2R2 K TD HD
Mega STe | MonSTer with dual IDE-CF memory card adapter | STe | SM-144 |NEC Multisync 1990SXi | IDE doubler | ST_ESSC | RSVE | ICD Link II | Link '97 | HD floppy drive/AJAX | HD floppy module | Minolta PCMCIA card-drive | Realtime Clock module | Discovery cartridge | Unitor-2 | Export | Combiner | Steady Eye | Human Touch | Unicorn USB

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Re: Discharging capacitors, PSU-testing with dummy loads

Post by exxos » Mon Oct 16, 2017 10:06 am

5V 2.2R =
5 / 2.2 = 2.72A x 5V = 11.36W

12V 10R =
12 / 10 = 1.2A x 12V = 14.4W

So I likely used 17 watt resistors.
4MB STFM 1.44 FD- VELOCE+ 020 STE - 4MB STE 32MHz - STFM 16MHz - STM - MEGA ST - Falcon 030 CT60 - Atari 2600 - Atari 7800 - Gigafile - SD Floppy Emulator - PeST - HxC - CosmosEx - Ultrasatan - various clutter

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Re: Discharging capacitors, PSU-testing with dummy loads

Post by Pacman » Mon Oct 16, 2017 11:00 pm

Thanks. I found some suitable ones:

2.2 Ohms/17 W high power resistor (1 pcs) TE connectivity 2.2 Ohms/6.1V/17W/10% SBCHE152R2K
and
10 Ohms/17W high power resistor (1 pcs) TE connectivity 10 Ohms/13V/17W/5% SBCHE1510RJ

.... if they're not buying your dummy load resistor kit.

i'm almost done writing the "how to" guide but one tiny detail slipped my mind. I believe I attached the resistors to the following output pins as shown below, and leaving them there regardless which output rail I was testing. Does it look right?
Mega STe power connector.png
Mega STe power connector.png (14.98 KiB) Viewed 333 times
Mega STe | MonSTer with dual IDE-CF memory card adapter | STe | SM-144 |NEC Multisync 1990SXi | IDE doubler | ST_ESSC | RSVE | ICD Link II | Link '97 | HD floppy drive/AJAX | HD floppy module | Minolta PCMCIA card-drive | Realtime Clock module | Discovery cartridge | Unitor-2 | Export | Combiner | Steady Eye | Human Touch | Unicorn USB

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Re: Discharging capacitors, PSU-testing with dummy loads

Post by exxos » Mon Oct 16, 2017 11:36 pm

Looks right yes. I've not checked the pinnout, so assume you have it correct.
4MB STFM 1.44 FD- VELOCE+ 020 STE - 4MB STE 32MHz - STFM 16MHz - STM - MEGA ST - Falcon 030 CT60 - Atari 2600 - Atari 7800 - Gigafile - SD Floppy Emulator - PeST - HxC - CosmosEx - Ultrasatan - various clutter

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Re: Discharging capacitors, PSU-testing with dummy loads

Post by Pacman » Mon Oct 16, 2017 11:44 pm

Thanks for confirming. The pinout should be correct.
I've just posted the "how to" here. I hope someone finds it useful.
Mega STe | MonSTer with dual IDE-CF memory card adapter | STe | SM-144 |NEC Multisync 1990SXi | IDE doubler | ST_ESSC | RSVE | ICD Link II | Link '97 | HD floppy drive/AJAX | HD floppy module | Minolta PCMCIA card-drive | Realtime Clock module | Discovery cartridge | Unitor-2 | Export | Combiner | Steady Eye | Human Touch | Unicorn USB

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Re: Discharging capacitors, PSU-testing with dummy loads

Post by exxos » Tue Oct 17, 2017 3:29 pm

Pacman wrote:
Mon Oct 16, 2017 11:44 pm
Thanks for confirming. The pinout should be correct.
I've just posted the "how to" here. I hope someone finds it useful.
Fantastic!

:bravo:
4MB STFM 1.44 FD- VELOCE+ 020 STE - 4MB STE 32MHz - STFM 16MHz - STM - MEGA ST - Falcon 030 CT60 - Atari 2600 - Atari 7800 - Gigafile - SD Floppy Emulator - PeST - HxC - CosmosEx - Ultrasatan - various clutter

https://www.exxoshost.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxoshost.co.uk/atari/last/storenew/ - All my hardware mods for sale - Please help support by making a purchase.
http://ataristeven.exxoshost.co.uk/Steem.htm Latest Steem Emulator

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