PC Engine GT recapped question about capacitors

[xybots]

Hi All

I've just recapped my PC Engine GT today, and every cap had leaked. I didn't have a 4.7μF 50V so I used a 4.7μF 35V and it worked like a charm.
I was wondering would I do any damage to my PC Engine GT as I should of replaced it with 4.7μF 50V.

The PC Engine GT is working great but just wanted to make sure if it's OK to use 4.7μF 35V.

thanks

[SephirothTNH]

In general you want to meet or exceed the original voltage rating. The original 50v may have been over specced and you might be fine. You could use a multi meter and check the voltage on that cap. If it's over 35v you would want to change it.

[NightWolve]

Well hello! Wow, I didn't expect to find new posts today AND by two different people in the same topic (still haven't tried relaunching the forum via a newsletter to registered accounts, plus now I have less time to work/fix existing data/content), haha! Thanks for stopping by!

OK, so like Chase said, it's always better to meet or exceed the max breakdown voltage rating of a capacitor (the higher/bigger, the better, just means more money/space), while keeping the capacitance the same. But in this case you went lower from 50V to 35V which I think should be fine, maybe... Even 16 VDC caps are safe for the most part on 5V PCBs, triple or more is preferable than the operating voltage and to handle ripple current/heat.

These motherboards in general operate at 5 VDC after the regulator, more true for portables (the batteries total 9 VDC), and I can't imagine some kind of inversion situation that'd ever lead to that area running near 35 VDC (the backlight lamp at best?)! I vaguely remember having this conversation with Steven Hanley though regarding higher "power inversion," the top PCEFX electrical engineer, so I'm gonna ask him just to be thorough/safe about this.

This is your first post/question EVER after 6 years of registration, so I'll do my best to help out! ; )


UPDATE: Yep, according to TheSteve, there is a power inversion circuit running at 24 Volts and a 22μF cap is involved if he remembers correctly. So still safe with a 35VDC cap!

I was waiting on an answer from Steven Hanley as I vaguely remember him mentioning something about power inversion years ago. He thinks one of the 22μF capacitors is involved with a 24-Volt power inversion circuit (best guess: for the backlight lamp?). So, 35VDC caps are safe. pic.twitter.com/NpzARQvPDY

— Nicolas Λειβαδίτης (@NightWolve75) February 23, 2022

Keep tabs on that tweet as Voultar or leonk may provide further answers/info.

32v I think. It's used on the LCD as bias voltage for contrast and on the TV tuner to power the RF amp stage. GAME GEAR also uses that voltage for the same purposes apparently.

— Leo Oliveira (@leo__oliveira) February 23, 2022

The plot thickens! So it's the CC502 spot, a 4.7μF capacitor to watch out for where up to a 32-Volt power inversion is possible. So your 35V model is barely safe I guess ? More peace of mind if it was 50V, but yeah, there you go, it mattered here!