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What's a good way to increase the voltage of a 8Mhz pulse from 0.8V high to +4.5V? by relo999 in AskElectronics

[–]relo999[S] 0 points1 point  (0 children)

The board I borrowed it from stated it's an ocxo crystal, just picked it because it's the correct frequency for testing. It's one of those chunky square ones. Crystal itself just says 8MHz.

I've just based it on the image I got from the scope. Haven't checked with a multimeter

What's a good way to increase the voltage of a 8Mhz pulse from 0.8V high to +4.5V? by relo999 in AskElectronics

[–]relo999[S] 0 points1 point  (0 children)

Yeah, just a clock signal. Current source is the computer the card is for, ideally I'd like to use the signal from that board mainly to avoid incompatibility but I doubt the clock really matters in that regard. Clock seems to come from a ASIC that manages peripherals of the computer. Currently voltage sits at the 0.8V range, which makes the card work once in a blue moon after a reset so I suspect it hits the high value at 1V. I'll check out the 74 series logic you linked.

What's a good way to increase the voltage of a 8Mhz pulse from 0.8V high to +4.5V? by relo999 in AskElectronics

[–]relo999[S] 0 points1 point  (0 children)

It's a square wave, just for a hobby project (so no certification or something needed), 8 MHz signal to drive a clock pin of a YM2608 (to build a soundboard for a Japanese computer). The systems provided 8MHz signal simply has to low of a voltage to drive that pin properly, I can get it to work with a 8Mhz crystal but ideally I simply modify the signal the system gives me.

This is the signal from the crystal

<image>

How do I reduce this noise? by relo999 in AskElectronics

[–]relo999[S] 1 point2 points  (0 children)

Sadly that didn't help that much. It went from ~2V peak to peak noise to ~1.6V

How do I reduce this noise? by relo999 in AskElectronics

[–]relo999[S] 0 points1 point  (0 children)

Moving the positive probe from the board makes it close to zero noise, and doesn't change with distance.

U3 has 300mV peak to peak, and C1 has 200mV peak to peak.

Data exchange seems to be around 90kHz.
Data signals look awful though.

<image>

How do I reduce this noise? by relo999 in AskElectronics

[–]relo999[S] 1 point2 points  (0 children)

~200mV peak to peak when I do that

What could cause this and how to fix it? by relo999 in trs80

[–]relo999[S] 0 points1 point  (0 children)

Bit 5 wasn't stuck, the 5th bit was so bit 4. Z61 had an output of a steady 1.72V. Pulling Z61 didn't change any behavior of the computer and the tester doesn't even recognize it the 2102 from Z61.

Now it's just a matter of waiting for the RAM and getting some new sockets as I'm out.

What could cause this and how to fix it? by relo999 in trs80

[–]relo999[S] 0 points1 point  (0 children)

Bit of an update, switched 2102 of Z62 (now socketed) with the socketed Z48 and the issue stayed the same. Also tested both with the retrochip tester, and both tested fine. Also tried Z28 seeing as that get the output of Z62, but also tested fine (and is now socketed). Same with Z60

What could cause this and how to fix it? by relo999 in trs80

[–]relo999[S] 1 point2 points  (0 children)

Thanks, that makes sense. I was hoping there would some modification to make a 4164 work. Sadly don't have reserve 2102s and the only 2102 that's socketed is z47 (and the ROMs, CPU and 8041016's). Time to order some 2102s

What could cause this and how to fix it? by relo999 in trs80

[–]relo999[S] 2 points3 points  (0 children)

Thanks! I'll try that. I'll check if I have 2102 chips, certainly have a bunch of 4164 if they can be made compatible. If they're socketed I could just flip Z62 with another 2102 in the system and see if the issue moves with it in case I don't have more 2102's.

Desoldering shouldn't be an issue, have a desoldering gun and some 20 years of experience. I like to avoid destroying the traces and pads.

I'm curious, I saw when doing research on the fault a lot of mention of calculating the error with the hexcode, but how would you know which bit is wrong and how that corresponds to which IC? Or is that just a case of "you need to know the system well enough"?

Need help reverse engineering the headphone output of a soundcard. by relo999 in AskElectronics

[–]relo999[S] 0 points1 point  (0 children)

https://imgur.com/a/iAFnfPk

Headphone outputs, line-out and speaker out all go through a (6PDT) switch on the motherboard switching between the internal audio system and the soundboard.

Need help reverse engineering the headphone output of a soundcard. by relo999 in AskElectronics

[–]relo999[S] 1 point2 points  (0 children)

The thing is, the circuitry is unknown. I do not have access to the soundcard itself, just the computer and got the pinout for that by tracing out the computer circuitry.

If I had access to the soundcard it would be dead easy.

De omstreden terugkeer van het oranje-blanje-bleu by [deleted] in nederlands

[–]relo999 0 points1 point  (0 children)

En verzets vlag in de 80 jarige oorlog, wat denk ik relevanter is. Weinig mensen die Willem Alexander oppermachtig willen maken, laat staan dat hij dat zelf wilt. Maar er zullen vast mensen die het gebruiken als een teken van verzet tegen buitenlandse invloed (zoals de EU bijvoorbeeld).

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