Jump to content
remowilliams

1200XL / Traco 7805 replacements

Recommended Posts

I installed Traco to my 1200XL and my 1050s. All units now run dead cold.

 

The final result was satisfying, but I had two problems.

 

1. They don't really fit into the footprint of a TO-220 package as their datasheet claims. Getting them to fit without interfering with the original heatsinks was a bit of a pain. Be very careful when bending the legs to get them to fit; they are tiny and fragile. Too tiny and too fragile for a power delivery component in my opinion. On one of my TSR 1-24120 for the 1050, after only a bit of bending, the legs broke off the pcb internally, up in the soft silicone potting. I had to unpot it and solder new legs onto it under a frigging microscope. It was a real pain, and the non-ROHS solder I had to use then posed an additional challenge in keeping them from unsoldering themselves again when I went to solder the unit down to the mainboard afterwards. Do not allow any stress on them to pass up into the potting and only bend once. I was more careful with the rest, but it still felt like a delicate situation. Also, make sure the cases sit flush on the mainboard for support and stability. You really don't want them suspended on those crappy legs. OH yeah, and I had to grind out a relief at the corner of the heatsink where the screw goes through the PCB to the bottom case. 🙄

 

2. On the 1200XL, I *thought* I detected a very faint, SUPER faint, herringbone pattern barely visible on certain darker screen colors. I was definitely overscrutinizing it and it may have been there already. Still, I counted the switching frequency (500khz) against the dotclock to see if it was theoretically possible, and realized it should be visible at 33 beats per horizontal raster, which is about what I *thought* I saw looked like. The thing is, when I laid my mainboard out on my bench, got the shielding off, and hooked it up again, I couldn't find any herringbone at all. Nevertheless, I added a pair of my lowest ESR capacitors I had on hand across the original 22uf axials on the 5v outputs just in case. Zero issues. I was prepared to add capacitors anyways.

 

With the above two things in mind, you may decide it might be too much of a hassle given the cost of the Traco parts.

 

(I'm one of those sociopaths who tries to keep the shielding intact, and the RF modulator installed. I have U1MB and supervideo XL 2.1 hidden under there.)

 

 

 

 

traco.png

Edited by rmzalbar
  • Like 3
  • Thanks 1

Share this post


Link to post
Share on other sites
9 hours ago, rmzalbar said:

Do not allow any stress on them to pass up into the potting and only bend once. I was more careful with the rest, but it still felt like a delicate situation. Also, make sure the cases sit flush on the mainboard for support and stability. You really don't want them suspended on those crappy legs.

 

Agreed, I was very careful bending the legs where required for fear of breakage.  I measured, did an initial 90 degree bend and then held them in place for the secondary bends.

 

  • Like 1

Share this post


Link to post
Share on other sites
On 6/10/2018 at 10:42 PM, Level42 said:

......not with 7805's.....I've never seen one die "aggressively"....only "peacefully" (which means the output got LOWER than the specced voltage instead of higher).

As far as my knowledge goes....the problem with c64 PSU (and probably atari's) is that the output voltage gets higher and higher...bricking your system.

Can you explain why?

Share this post


Link to post
Share on other sites
On 9/21/2020 at 7:08 AM, rmzalbar said:

(I'm one of those sociopaths who tries to keep the shielding intact, and the RF modulator installed. I have U1MB and supervideo XL 2.1 hidden under there.)

 

Beautiful.

 

Another as-it-should-be, shields-and-parts psychopath lover, here!

 

I wonder what a poke 710,2 and poke 710,4 reveal on-screen... Any structured or random noise-pattern will be seen there, immediately.

 

💪💪👍 

Edited by Faicuai
  • Like 1

Share this post


Link to post
Share on other sites
On 9/21/2020 at 7:08 AM, rmzalbar said:

I installed Traco to my 1200XL and my 1050s. All units now run dead cold.

 

The final result was satisfying, but I had two problems.

 

1. They don't really fit into the footprint of a TO-220 package as their datasheet claims. Getting them to fit without interfering with the original heatsinks was a bit of a pain. Be very careful when bending the legs to get them to fit; they are tiny and fragile. Too tiny and too fragile for a power delivery component in my opinion. On one of my TSR 1-24120 for the 1050, after only a bit of bending, the legs broke off the pcb internally, up in the soft silicone potting. I had to unpot it and solder new legs onto it under a frigging microscope. It was a real pain, and the non-ROHS solder I had to use then posed an additional challenge in keeping them from unsoldering themselves again when I went to solder the unit down to the mainboard afterwards. Do not allow any stress on them to pass up into the potting and only bend once. I was more careful with the rest, but it still felt like a delicate situation. Also, make sure the cases sit flush on the mainboard for support and stability. You really don't want them suspended on those crappy legs. OH yeah, and I had to grind out a relief at the corner of the heatsink where the screw goes through the PCB to the bottom case. 🙄

 

 

 

traco.png

Do you even need to mount the Traco to the heat sink?

Share this post


Link to post
Share on other sites
11 hours ago, kheller2 said:

Do you even need to mount the Traco to the heat sink?

No. In the photo, the Traco is not attached to the heatsink. I left the heatsink there for the benefit of the rectifier.

Share this post


Link to post
Share on other sites
On 2/3/2021 at 12:06 PM, Faicuai said:

Another as-it-should-be, shields-and-parts psychopath lover, here!

 

I wonder what a poke 710,2 and poke 710,4 reveal on-screen... Any structured or random noise-pattern will be seen there, immediately.

 

💪💪👍 

I do have my limits: I will leave the cardboard shield out of a breadbin C64 so those hot chips will live longer; however, I always at least replace the bottom shield since these old PCBs lack even a ground fill.

 

I'll try those pokes next time I have the 1200XL up on the desk. I can definitely confirm the faint herringbone is not my imagination, though I don't notice it unless it crosses my mind and I look for it. I finally ordered a DS1054Z today after having been without a scope for several months (I was only borrowing one, I never owned one.) So pretty soon I'll get down and dirty with some ceramic capacitors and see what I can do about it.

Edited by rmzalbar

Share this post


Link to post
Share on other sites
2 hours ago, rmzalbar said:

I finally ordered a DS1054Z today after having been without a scope for several months (I was only borrowing one, I never owned one.) So pretty soon I'll get down and dirty with some ceramic capacitors and see what I can do about it.

 

Great! Please let us know your results. I have a few TSR 1-2450's and would like to put one in a UAV-D 1200XL. Wondering if the UAV-D would isolate the video signal enough from the TSR noise/interference.

 

Share this post


Link to post
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.

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...