I love my 64c but...

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JWag
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Re: I love my 64c but...

Post by JWag »

eslapion wrote: A few years back, I converted my 250466 to use a 8500 CPU and 8562 VIC-II to make it leaner. The change of these 2 chips to HMOS technology didn't cause any problems.
Thanks for mentioning this. I have just done the same on a 250407. On this board, the supply to the VIC pin 13 runs through FB12, a ferrite bead. I simply re-routed FB12 from +12V to +5V (to the load side of FB19), and the 8562 works with no problem. I need to put a label on the board as a warning not to ever replace it with a 6567...

I'm slowly turning this board into an optimal C64. Sockets, 8500, 8562, PLAnkton, plus heatsinks on the 6581 and 6526s.


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eslapion
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Re: I love my 64c but...

Post by eslapion »

AFAIK, if you reroute the +12Vdc feed to +5Vdc then there is no risk of any damage if you put the wrong chip. If you put a 6567 on your board now, it just won't work.

The other way around, however, is a whole different story. If you mod a C64c board to support a 6567/6569 and mistakenly plug a 8562/8565 then the HMOS VIC-II will be destroyed by the 12V source. Same goes with setting a C64r for 656X and installing a 856X VIC-II.
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Re: I love my 64c but...

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I'm more worried that without a note I'll forget I did the mod. I can see myself in five years swapping in a mystery 6567 for testing, then panicking when it doesn't work. ;)
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Gyro Gearloose
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Re: I love my 64c but...

Post by Gyro Gearloose »

You can also swap out the linear regulators and replace them with drop-in switchers. Those old linear regulators sure got hot.
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Re: I love my 64c but...

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Gyro Gearloose wrote:You can also swap out the linear regulators and replace them with drop-in switchers. Those old linear regulators sure got hot.
This problem is made considerably less important when switching from a 6567 to a 8562. The HMOS VIC-II doesn't consume any 12Vdc so all that's left as a load on the 7812 regulator is the SID which takes less than 50mA ; it also consumes much less 5Vdc.

On my own board 250466, I felt the significant reduction in thermal dissipation from these 2 regulators made it unnecessary to replace them with switchers.
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Gyro Gearloose
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Re: I love my 64c but...

Post by Gyro Gearloose »

eslapion wrote:
Gyro Gearloose wrote:You can also swap out the linear regulators and replace them with drop-in switchers. Those old linear regulators sure got hot.
This problem is made considerably less important when switching from a 6567 to a 8562. The HMOS VIC-II doesn't consume any 12Vdc so all that's left as a load on the 7812 regulator is the SID which takes less than 50mA ; it also consumes much less 5Vdc.

On my own board 250466, I felt the significant reduction in thermal dissipation from these 2 regulators made it unnecessary to replace them with switchers.
That is good news, I still have old chips in my 64 and 64C, so quite hot in there. I suppose my 128 has cooler-running chips.
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Re: I love my 64c but...

Post by JWag »

I worry a little that switchers would leave a little noise in the special 5V and 12V rails, which might come through in the video and/or audio (one of the main benefits of linear regs is relatively low noise). Do you find this to be the case, Gyro? Or is the on-board filtering sufficient?

Can definitely confirm the reduced heat overall after adding the HMOS CPU and VIC.
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Re: I love my 64c but...

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Good question, I only did it to one 64, and with switchers that are quite old. So even if they worked with zero noise, it's of little use for you since they don't make em anymore.
I didn't measure a thing besides the DC voltage. I did however measure the output of super cheap eBay switchers, it was a mess. But I didn't check on a big monitor to see the result, I was using a 9" CRT with a weak tube.
I guess I'd need to use the FFT function of my scope to look for spurs and tones that squeeze their way into the video, then look at a good monitor to check for effects. I only have a working spectrum analyzer that starts at 10MHz...

A simple LC filter can reduce a spur by 30dB easily. But then you need to add that to the BOM and it's no longer a drop-in solution.
I designed a TO-3 switcher module that just plops in place and it has LC filtering for my 1541. Work quite well. I only made two after which I lost interest.
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Re: I love my 64c but...

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Gyro Gearloose wrote:I didn't measure a thing besides the DC voltage. I did however measure the output of super cheap eBay switchers, it was a mess.
I measured up to 150mV ripple from cheap "feePay" switchers. Good TI PT78STXXX series have about 25mV (5V ones) ripple.
I guess I'd need to use the FFT function of my scope to look for spurs and tones that squeeze their way into the video, then look at a good monitor to check for effects. I only have a working spectrum analyzer that starts at 10MHz...
I thought you had a good scope. I have a Tektronix TDS1002 myself, purchased back in 2003 but nowadays, the best deal in town are Rigol scopes.
I designed a TO-3 switcher module that just plops in place and it has LC filtering for my 1541. Work quite well. I only made two after which I lost interest.
You should offer these on Denial. Lots of people with old VIC-20s would be interested in having a solution to reduce heat in their old machines.

Early VICs with 2-Prong PSUs run very hot.
JWag wrote:Can definitely confirm the reduced heat overall after adding the HMOS CPU and VIC.
If you can find 8521 CIAs or 6526A with code 216A printed on them, these are HMOS CIAs that also consume less power and produce less heat. Replace your CIAs with these.
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Gyro Gearloose
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Re: I love my 64c but...

Post by Gyro Gearloose »

eslapion wrote:I measured up to 150mV ripple from cheap "feePay" switchers.
Do you mean the 50Hz to 120Hz ripple from the rectifier was not rejected? Or can we can talk about switching noise here? I measured something in that range, yes. Not great, usable, with room for improvement, but unbeatable for the price.
eslapion wrote:I thought you had a good scope.
Which one? The vintage Tektronix 547? The 531? The 567? The Rigol DS5102C that's so old it's not even on Rigol's site anymore? Or my Rigol DS1054Z?

I was referring to an actual spectrum analyzer, my 1L20 plugin for the 547.
eslapion wrote: You should offer these on Denial. Lots of people with old VIC-20s would be interested in having a solution to reduce heat in their old machines.
Meh, then they should look harder.

http://www.ezsbc.com/index.php/featured ... /psu7.html

Mine is definitely prettier. I don't think I can compete with the ezsbc offering. I know I don't want a small assembly line in my room. It's shitty enough as it is in here.

So are you saying you finally assembled the module?
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