Enterprise Forever
:UK => Hardware => Display => Topic started by: emptiness on 2022.April.18. 17:36:23
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I've recapped my Enterprise 64 and replaced the voltage regulators. Today I replaced TR2 and the video output is the best I've ever seen it.
However, it still "wobbles". I've adjusted L2 to get the wobbling as slow as I can. I've tried adjusting C43 but it does not appear to make much difference.
Here's a short YouTube video showing the current video output via SCART.
https://youtu.be/QfPLyI8MAOU (https://youtu.be/QfPLyI8MAOU)
Can anyone suggest what I should try next to get a stable display?
thanks
Dave
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The next step could be to try it with other TVs. It happens that sometimes they don't auto-adjust to the slightly different syncs of the EP.
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Thanks. I'll give that a go. I'm pretty sure I've tried a working EP64 with this TV and it was fine though. I'll check.
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Check the 5V voltages not just at the regulators, check at chips, for example: U24, U25, U33 on +5A, ROM, onboard RAM, Z80 on a +5B
Nick chip use +5A, if it is lower can also result this wobbling effect. Also check +12V, for example on U35 Pin14,15,16.
And do you have a scope? Will be good check the Nick clock.
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Thanks Zozo. I'll try those checks this weekend.
I've had this motherboard hanging around in my box of stuff for ~35 years I'm really hoping I can finally get it to a fully working condition.
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One more hint: If it is built with Philips capacitors then recommended to replace all.
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Replacing the electrolytic capacitors was the first thing I did :)
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Check the 5V voltages not just at the regulators, check at chips, for example: U24, U25, U33 on +5A, ROM, onboard RAM, Z80 on a +5B
Nick chip use +5A, if it is lower can also result this wobbling effect. Also check +12V, for example on U35 Pin14,15,16.
And do you have a scope? Will be good check the Nick clock.
Sorry, for the months delay - a few unforeseen events happened and I got distracted.
These are the voltages I measured between the VCC and GND pins of the following chips:
U24 4.94
U25 4.94
U33 4.93
U35 11.87
RAM 4.92
ROM 4.91
Z80 4.91
NICK 4.92
I'm having trouble with my scope so I haven't managed to get the Nick chip clock yet - still working on that.
In order to help me identify the chips and pinouts on the circuit board I made the following image - I'm attaching here in case someone else might find it useful. The XCF file is the GIMP original with the layers preserved for ease of editing.
[attach=1]
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Finally! The video output on my Enterprise 64 motherboard is now rock steady!
I eventually managed to get a look at the nick clock using an oscilloscope and it wasn't pretty. I installed the "L2" board by Károly Vaczkó and now my video problems have gone.
Next up is wiring up a keyboard and memory expansion.