Posted By
DeadTED
on 2019-05-20
23:09:37
|  C116 current draw - updated c116 portable build
Hey guys, I am trying to create a portable c116 with 64k upgrade.
anyone know how much current a c116 draws with a cart installed?
Also anyway to reduce the amount of current the c116 uses?
I will also have a built in sd2eic so any specs on current draw for the would also be handy.
Finally if anyone has any suggestions on how to improve the internal power consumption and heat generate that would be appreciated.
Am thinking of creating an hinged screen with built in battery that attaches to the c116 without damaging it.
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Posted By
MCes
on 2019-04-06
17:50:04
 | Re: C116 current draw
Have a look at page 6... (ok, it's a PLUS4, but...)
ftp://www.zimmers.net/pub/cbm/schematics/computers/plus4/Plus_4_Technical_Docs.pdf
C16 DRAM need less than 100mA (total).
I suggest to cut out R10 (20 Ohm 5W) and replace the 7805 with a 5V dc-dc converter (more than 90% power efficiency), replace ROM with C-mos eprom, replace 7406 with 6x 2N7000.....
What else?
Yes: replace D-Ram with 16K (or 64k) of S-Ram (cutting out also 2x74LS257 )
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Posted By
MCes
on 2019-04-06
18:01:19
| Re: C116 current draw
Remember to trim the DC-DC converter to obtain on chips supply pins the value of 4.75V because less Vcc become less power and 4.75V is the chips lowest nominal voltage supply: 5V+/- 5%
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Posted By
DeadTED
on 2019-04-06
18:03:28
| Re: C116 current draw
!!! Ok thank you. I may do some before and after measurements 
Are the 74ls257 not required if I do the 64k?
I may try all these mods on my spare c16 first ....
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Posted By
MCes
on 2019-04-06
18:12:24
| Re: C116 current draw
2x 74LS257 are used to multiplexed the address to drive the Dram, if you replace d-ram with a static ram the multiplex (2x 74LS257) become useless...
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Posted By
MMS
on 2019-04-07
06:13:24
 | Re: C116 current draw
It is told, that the modern EEPROMs draw less current than the original ROMs. I did not measure myself.
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Posted By
DeadTED
on 2019-04-07
08:31:03
| Re: C116 current draw
@MCes do you know of a circuit to do the sram hack. also any suggested part numbers for the 5v dc converter?
@MMS yes I will change the the ROMs to CMOS equivalents.
Seems I can save at least 500ma by getting rid of the rf modulator, swapping out the roms for CMOS and the ram for SRAM.
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Posted By
MCes
on 2019-04-07
10:54:26
| Re: C116 current draw
may be this
https://www.ebay.it/itm/Mini-DC-DC-4V-12-24V-To-5V-3A-Adjustable-Step-Down-Power-Module-Buck-Converter/232457573754?hash=item361f8d157a:g:oM0AAOSwcUFZmtg-
or
https://www.ebay.it/itm/LM2596-2596S-3A-DC-Spannungsregler-Wandler-Buck-Converter-Step-Down-Module-s/173408540246?hash=item285ff45656:g:nZgAAOSwjodaPc~g
Ram has selected by "CAS" signal, but static one need a little circuit that during Write cycle end it befotre bus changing
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Posted By
MCes
on 2019-04-07
10:55:12
| Re: C116 current draw
Ram is selected by "CAS" signal, static ram need a little circuit that stop the Write procedure before a bus changing
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Posted By
MMS
on 2019-04-08
11:17:28
| Re: C116 current draw
500mA is a lot, keeping in mind all goes through that regulator, and extra heat generated within that small housing.
Ps actually the modulators were one of the most expensive part of these machines. I had to hack my Zx spectrum too to get rid of that noise generator and get a much cleaner CVBS signal from the Speccy mobo. Same here...
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Posted By
DeadTED
on 2019-04-09
08:49:14
| Re: C116 current draw
Ok so here is where I am at.
1. I scavaneged a very slim lithium tablet battery 4v @ 5000ma that fits inside the c116 case under the motherboard! The battery is very thin
2. I will replace the internal big white resistor with a dc-Dc step up converter and add a lithium USB charging circuit for the battery.
3. I will install both calc plus and script plus inside but I need help with a simple circuit that decides the roms otherwise I will stack the two roms and put a hard switch
4. Will be contacting a plastic Moulding place to make me a c116 friendly hinged lcd case that clips onto the c116 somehow without damaging the case...
5. Replace all roms with cmos equivalents
6. Cannot do the Sram conversion as I do not have the skill
7. May add a user port or an esp8266 wifi based serial port
8. Remove Rf modulator to save space and power
9. Add sd2eic internal module
Anyone have suggestions for a 7 or 9 inch power efficient lcd screen?
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Posted By
MCes
on 2019-04-09
10:54:37
| Re: C116 current draw
Rf modulator also provide to mix luminance and crominance components in cvbs video out, so no modulator no video output......
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Posted By
MMS
on 2019-04-09
15:25:09
| Re: C116 current draw
or only Svideo (the two signals separately available on video out).
All of my TVs have Svideo input at the side connector panel (but all of them are Philips made )
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Posted By
DeadTED
on 2019-04-09
18:25:58
| Re: C116 current draw
@MMS since I will be mounting an lcd screen S-video should be fine
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Posted By
MCes
on 2019-04-10
02:56:00
| Re: C116 current draw
@MMS
TED Y/C video outputs are not filtered and are high impedance, inside the modulator there are the filters and the analog buffers, so it isn't possible to eliminate it, but maybe that it's possible replace it with a little board that do only what it's needed...
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Posted By
DeadTED
on 2019-04-10
08:23:03
| Re: C116 current draw
I think this might do the job.
https://www.google.com.au/amp/s/amazingdiy.wordpress.com/2013/02/08/c64-s-video-mod/amp/
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Posted By
MMS
on 2019-04-10
17:10:17
| Re: C116 current draw
@MCes
Thank you the info, I was not aware. I checked the schematic, correct. So it works differently than the Spectrum I hacked (it translates the standard CVBS signal into an RF).
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Posted By
DeadTED
on 2019-04-14
06:18:47
| Re: C116 current draw
Hello @MCes. One question, when I remove the white 5w resistor and 7805 to replace with a DC-DC unit which I now have, do I need to put a jumper wire across where the the 5w resistor used to be or can I just ignore it?
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Posted By
MCes
on 2019-04-14
07:19:40
| Re: C116 current draw
The 5W resistor has to be removed and it's pins has to be left opened:
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Posted By
DeadTED
on 2019-05-20
23:15:30
| Re: C116 current draw - updated c116 portable build
Hi all, I have now successfully completed, power circuit upgrade to get rid of the 7805 and white resistor.
Also internally mounted and sd2iec and upgraded to 64k.
All mods are simple and work great.
Next step is to install and internal battery and related charging circuit, small enough to fit but big enough to give me 2-3 hours of gaming time.
I am investigation possible lcd options with custom mount.
What would be really cool is to figure out how to turn a smart phone into a wireless game pad !
Anyone know how I can post a photo of the mods?
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Posted By
gerliczer
on 2019-05-21
02:18:42
| Re: C116 current draw - updated c116 portable build
DeadTED wrote: Anyone know how I can post a photo of the mods?
Log in. Click the link of the topic which you wish to make a comment on. Click the Reply to This Topic link at the bottom of the page. Scroll to the very top if you browser moves the message field up to the top of you browsing window. Read the instructions under the Post Your Message title, or the instructions opened in a new page by clicking the Forum Help link. Pick your choice. Follow the instructions.
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