Jump to content
IGNORED

Retrotink 2X inside 800 - technical questions


Xebec

Recommended Posts

Hey Atari fans -

 

I'm messing around with the idea of putting a Retrotink 2X inside an 800, so an HDMI cable can just come straight out the back of the computer (instead of RF)..  I have two questions:

 

1.  If I 'create' a short S-Video cable by tapping into the monitor output ports (or elsewhere on the board), will that create noticeable additional noise on the video out if I use the regular monitor port with a CRT?   (and when not using the HDMI out) 

 

2.  I see the Retrotink 2X needs a "5V at least 1A" psu - so assuming it needs up to 5W at certain times -- is there any chance an 800 w/Incognito (instead of 3 ancient giant 16KB RAM boards :) ) -- would have enough margin to sustain this on the 5V output?     I plan to measure the retrotink for 'real' output via a USB power meter once I get it..  

 

Thanks.. 

Link to comment
Share on other sites

7 hours ago, Xebec said:

Hey Atari fans -

 

I'm messing around with the idea of putting a Retrotink 2X inside an 800, so an HDMI cable can just come straight out the back of the computer (instead of RF)..  I have two questions:

 

1.  If I 'create' a short S-Video cable by tapping into the monitor output ports (or elsewhere on the board), will that create noticeable additional noise on the video out if I use the regular monitor port with a CRT?   (and when not using the HDMI out) 

 

2.  I see the Retrotink 2X needs a "5V at least 1A" psu - so assuming it needs up to 5W at certain times -- is there any chance an 800 w/Incognito (instead of 3 ancient giant 16KB RAM boards :) ) -- would have enough margin to sustain this on the 5V output?     I plan to measure the retrotink for 'real' output via a USB power meter once I get it..  

 

Thanks.. 

 

Well, a stock (fully-populated 48KB RAM + OS/ROM) A800 consumes about 15.5 - 16.5 watts, on idle. 

 

An 800/Incognito, just booted at SDX with NO .ATRs attached, consumes about 9.8w to 10.4watts, mostly idling at 9.8W.

 

Besides having a capable on-board power-supply, you certainly have plenty of juice / latitude left for bringing that Analog-to-Digital converter / scaler on-board, and feed it directly from the 800's power board. You even have +5v, -5v AND +12v available in ALL of the expansion slots (!)

 

Overall, I strongly recommend using the 30Watts 9v A/C units when feeding the 800, because (on the scope) they appear the cleanest, and are definitely more capable than the 800's stock P/S.

Edited by Faicuai
  • Thanks 1
Link to comment
Share on other sites

5 hours ago, Faicuai said:

 

Well, a stock (fully-populated 48KB RAM + OS/ROM) A800 consumes about 15.5 - 16.5 watts, on idle. 

 

An 800/Incognito, just booted at SDX with NO .ATRs attached, consumes about 9.8w to 10.4watts, mostly idling at 9.8W.

 

Besides having a capable on-board power-supply, you certainly have plenty of juice / latitude left for bringing that Analog-to-Digital converter / scaler on-board, and feed it directly from the 800's power board. You even have +5v, -5v AND +12v available in ALL of the expansion slots (!)

 

Overall, I strongly recommend using the 30Watts 9v A/C units when feeding the 800, because (on the scope) they appear the cleanest, and are definitely more capable than the 800's stock P/S.

Where would I get the 30W 9V A/C unit?  

Link to comment
Share on other sites

8 hours ago, Faicuai said:

Well, a stock (fully-populated 48KB RAM + OS/ROM) A800 consumes about 15.5 - 16.5 watts, on idle. 

 

An 800/Incognito, just booted at SDX with NO .ATRs attached, consumes about 9.8w to 10.4watts, mostly idling at 9.8W.

One issue is I believe most of the power reduction is on the +12V rail due to elimination of the 4116 DRAM chips, on the Incognito modded 800 almost all the power consumption is on the +5V rail and could be near the 1A limit of a typical 7805, though Atari did add a 33 ohm bypass resistor to deliver additional current.

 

If adding an internal component that is supposed to consume 500mA I would suggest adding a second 7805, or replacing the stock one with one rated at 1.5A such as the L7805CV.

Edited by BillC
Link to comment
Share on other sites

1 hour ago, BillC said:

One issue is I believe most of the power reduction is on the +12V rail due to elimination of the 4116 DRAM chips, on the Incognito modded 800 almost all the power consumption is on the +5V rail and could be near the 1A limit of a typical 7805, though Atari did add a 33 ohm bypass resistor to deliver additional current.

 

If adding an internal component that is supposed to consume 500mA I would suggest adding a second 7805, or replacing the stock one with one rated at 1.5A such as the L7805CV.

We'll put this to the test, tomorrow.

 

I will extract Incognito, and fire-up the system (leaving it to 6502, Antic, GTIA, Pokey, PIA and supporting chips consumption).

 

If total wattage exceeds 5 watts, it is clear that the system core 5v-supply is designed for MORE than 1amp @ 5 volts... unless those chips work at something other than 5v.

Edited by Faicuai
Link to comment
Share on other sites

3 minutes ago, Faicuai said:

We'll put this to the test, tomorrow.

 

I will extract Incognito, and fire-up the system (leaving it to 6502, Antic, GTIA, Pokey, PIA and supporting chips consumption).

 

If total wattage exceeds 5 watts, it is clear that the system core 5v-supply is designed for MORE than 1amp @ 5 volts... unless those chips work at something other than 5v.

The 33ohm/2W 7805 bypass resistor supplies an additional 120 to 150mA(depending on unregulated DC supply voltage) on top of what the 7805 delivers. I'm just saying that if there is a potential issue when adding additional internal devices then replacing the typical 7805 with the L7805CV would be a good idea. They aren't expensive, DIGIKEY has the L7805CV priced as low as $0.50 versus $.029 for the 7805, and the L7805CV are available from eBay for as low as 10 for less than $1(with free slow shipping from china).

 

Link to comment
Share on other sites

13 hours ago, BillC said:

The 33ohm/2W 7805 bypass resistor supplies an additional 120 to 150mA(depending on unregulated DC supply voltage) on top of what the 7805 delivers. I'm just saying that if there is a potential issue when adding additional internal devices then replacing the typical 7805 with the L7805CV would be a good idea. They aren't expensive, DIGIKEY has the L7805CV priced as low as $0.50 versus $.029 for the 7805, and the L7805CV are available from eBay for as low as 10 for less than $1(with free slow shipping from china).

 

Ok, so here are the test's results:

 

1. Power Consumption, 800 WITH Incognito, idle: 10.8 Watts

2. Power Consumption, 800 MINUS Incognito, idle: 9.1 Watts

3. External P/S parasitic  consumption / drag: 1.8 Watts

 

Therefore:

 

1. System's net power-consumption (without Incognito) is 7.3 Watts. This is definitely higher than 1.15amp @ 5v.

2. Incognito's net power-consumption (on idle) is 1.7 Watts.

 

I do wonder if there is a design issue, then, with the +5v supply on the 800, per your observations and component-ratings (?)

Link to comment
Share on other sites

7 hours ago, Faicuai said:

1. System's net power-consumption (without Incognito) is 7.3 Watts. This is definitely higher than 1.15amp @ 5v.

How are you measuring power consumption, output of the AC adapter, unregulated DC from the bridge rectifier, other?

1A unregulated DC current into the 7805/33ohm resistor would provide 5W power to the circuitry, but would result in 9 to 10W actual power consumption, the difference is the power dissipated as heat by the 7805 and 33ohm/2W resistor. 

 

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...