Megadrive 1 power regulators

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Lardo Boffin
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Megadrive 1 power regulators

Postby Lardo Boffin » Thu Oct 12, 2017 9:43 am

Hi all

I have decided to recap my early Megadrive in a bid to reduce the vertical lines on the screen (‘jail bars’) as this is the first bit of advice offered on the web.
Aside from finding around 30 electrolytic capacitors and a Z80(!) and have found a couple of 7805 regs connected to a heatsink:-

DDBE933B-D10D-40DB-8320-0A3C7A3AB549.jpeg


Is there a modern version of these I can use and get rid of the heat sink?

Thanks

Lardo
BBC model B 32k issue 4, 16k sideways RAM, Watford 12 ROM board, Retroclinic Datacentre + HDD, matchbox co-proc, Viglen twin 40/80 5.25" discs, acorn cassette
BBC model B 32k issue 7, turboMMC, Opus Challenger 3 512k, Pi 3 coproc, Acorn 6502 coproc

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1024MAK
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Re: Megadrive 1 power regulators

Postby 1024MAK » Thu Oct 12, 2017 10:06 am

I think you know the answer... [-X

Either use a RECOM or a TRACO type like in the links below, they can be used to replace 7805 voltage regulators in most applications :wink: .

Prices on these DC/DC converters/regulators often change, so also check the prices of other suppliers ;)

Here are some part numbers and links:-
Recom R-785.0-1.0
https://www.rapidonline.com/recom-r-785-0-1-0-1a-sgl-out-converter-84-2573
http://uk.farnell.com/recom-power/r-785-0-1-0/converter-dc-to-dc-1-5v-to-5-5v/dp/1793143

Traco Power TSR 1-2450
https://www.rapidonline.com/tracopower-tsr-1-2450-single-output-dc-dc-converter-1w-51-7072
http://uk.farnell.com/tracopower/tsr-1-2450/converter-dc-dc-5v-1a-sip/dp/1696320

Oh, and even the Wikipedia page says it has a Z80 in it!

Mark
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vanpeebles
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Re: Megadrive 1 power regulators

Postby vanpeebles » Thu Oct 12, 2017 10:52 am

I'm a Megadrive fanboy, and the Z80 does the sound :)

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Lardo Boffin
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Re: Megadrive 1 power regulators

Postby Lardo Boffin » Thu Oct 12, 2017 11:01 am

1024MAK wrote:I think you know the answer... [-X

Mark


Thanks. I have tried to get out of the habit of assuming... I generally seem to get it wrong! :oops:

I did think I had read somewhere about the Z80 but then assumed I had imagined it. Sleep deprivation does weird things to the brain. :?
BBC model B 32k issue 4, 16k sideways RAM, Watford 12 ROM board, Retroclinic Datacentre + HDD, matchbox co-proc, Viglen twin 40/80 5.25" discs, acorn cassette
BBC model B 32k issue 7, turboMMC, Opus Challenger 3 512k, Pi 3 coproc, Acorn 6502 coproc

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1024MAK
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Re: Megadrive 1 power regulators

Postby 1024MAK » Thu Oct 12, 2017 11:42 am

Lardo Boffin wrote:
1024MAK wrote:I think you know the answer... [-X

Mark


Thanks. I have tried to get out of the habit of assuming... I generally seem to get it wrong! :oops:

I did think I had read somewhere about the Z80 but then assumed I had imagined it. Sleep deprivation does weird things to the brain. :?

Just check that the existing 7805 regulator outputs are NOT connected together (directly or via low value resistors). As there are various ways that series type voltage regulator(s) can be used with additional components to produce a higher current (or higher voltage) regulated supply...

Mark
For a "Complete BBC Games Archive" visit www.bbcmicro.co.uk NOW!
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danielj
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Re: Megadrive 1 power regulators

Postby danielj » Thu Oct 12, 2017 12:05 pm

The Z80 also allows it to play master system games :) - the powerbase converter was just a straight through more or less:

https://www.youtube.com/watch?v=HIVNTeWKRvw

d.

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Lardo Boffin
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Re: Megadrive 1 power regulators

Postby Lardo Boffin » Thu Oct 12, 2017 8:55 pm

Having (finally) removed the heat sink...

No obvious linkage from above:-
0C76AB10-740F-4EAC-9837-99CCFAD18553.jpeg



But from underneath? I can see they have common paths joined by capactitors but not sure if that counts?

3DFB2011-DD85-4F84-9DDF-53B3AB25AB80.jpeg
BBC model B 32k issue 4, 16k sideways RAM, Watford 12 ROM board, Retroclinic Datacentre + HDD, matchbox co-proc, Viglen twin 40/80 5.25" discs, acorn cassette
BBC model B 32k issue 7, turboMMC, Opus Challenger 3 512k, Pi 3 coproc, Acorn 6502 coproc

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1024MAK
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Re: Megadrive 1 power regulators

Postby 1024MAK » Thu Oct 12, 2017 11:00 pm

It's not really a surprise that the input terminals are linked, or that the 0V/common/ground terminals are linked.

If you use a multimeter on resistance, test between the output terminals, one lead on each output leg. If the result is more than say 500 ohms, they are not linked :wink:

Mark
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BeebWiki‬ - for answers to many questions...

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vanpeebles
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Re: Megadrive 1 power regulators

Postby vanpeebles » Mon Oct 16, 2017 7:59 am

While it is in bits, you might as well wire up a 50/60hz switch and a region switch too :)

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trixster
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Re: Megadrive 1 power regulators

Postby trixster » Mon Oct 16, 2017 8:06 pm

That's a good idea. Have you ever heard PAL Sonic and then immediately listened to NTSC Sonic straight afterwards?!? :mrgreen:
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Lardo Boffin
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Re: Megadrive 1 power regulators

Postby Lardo Boffin » Mon Oct 16, 2017 8:35 pm

vanpeebles wrote:While it is in bits, you might as well wire up a 50/60hz switch and a region switch too :)

Interesting idea. Are there any recommended web links on how to do this? A quick look up suggests loads and narrowing it down could take a while...
BBC model B 32k issue 4, 16k sideways RAM, Watford 12 ROM board, Retroclinic Datacentre + HDD, matchbox co-proc, Viglen twin 40/80 5.25" discs, acorn cassette
BBC model B 32k issue 7, turboMMC, Opus Challenger 3 512k, Pi 3 coproc, Acorn 6502 coproc

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vanpeebles
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Re: Megadrive 1 power regulators

Postby vanpeebles » Tue Oct 17, 2017 7:12 am

I'm not too sure, both of mine where already done when I got them, they have metal toggle switches on the back :)

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vanpeebles
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Re: Megadrive 1 power regulators

Postby vanpeebles » Tue Oct 17, 2017 7:14 am

https://mdpal60.net/wiki/megadrive/regionmod/start that seems a good one for the region mod.


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