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Another thought, there is an internal fuse inside the power adapter. The adapter is held together by 4 screws hidden under the corner feet. They pull off exposing the screws. Open and check the fuse and for breaks in the cable near the adapter. The cable can be easy repaired if break is near the adapter end, cut, strip and resolver.
Also, by measurements I took of the demand for current by a PC88 on the 9.5VAC going into the unit was 100mA. That is means that the adapter is 20 times bigger, than running demand and an extreme safe margin. This is why it never gets warm, let alone hot. Hence they rare failure of the internal transformer and strong possibility that other items like fuse or damaged cable are more likely.
When the PC88 was brand new, I needed multiple adapters to test and burn in new PC88 in Cerretos. We had a bunch of 9VAC 100mA adapters in parts deptment for an older unit with the same plug. 100mA is 0.1Amps or 1/20th of the provided by the factory's 2.0 Amp.
These 9VAC at 100mA tiny adapters were used continuously. Yes, they got lightly warm and the 9V cable not as rugged, but they worked. Bottom line and point is than if you used 9VAC 1000mA (1Amp) adapter, it would be still 10 times over run current.
So why were they 9.5Volta at 2000mA?My though was maybe engineering wanted it to work in Japan where they had 100VAC where if your line dropped to 90VAC.
So I place a PC88 on a bench and lowered the line voltage slowly down to 88VAC, while observing the how the internal power supply reacted at several key point for voltage, ripple, noise, etc.
No issues, and the PC88x kept working. So why 9.5V? Why not 9VAC?
Also if you have read this far and follow my tech speak and you ever work on a PC88 that crashes after being on and you find that the 5V digital is the problem, note that both the 7805 regulators, are connected via a diode near the main micro processor. This is so the digital supply can steal a little current from the 5V analog regulator.
The one you see overheat and thermally shut down is not the problem, they work on tandom. I always replace both 7805, one is bad and the other may be damaged, the are a 50 cent part.
On my PC88, I removed this diode that links the two 5 volt regulators and then replace the digital 7805 with a 78T05 which handles more current. This was to reduce digital noise from entering the 5 volt analog bus..
The 78T05 was not available in 1992, hence the linking solution by engineering. It handles up to 1.5A over the 1A of the 7805.
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On Sat, Mar 9, 2019 at 6:26 PM, Roger J<[email protected]> wrote: It will be fine, as internally the 9 or 9.5VAC ends up as three regulated 5VDC supplies.
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On Sat, Mar 9, 2019 at 6:01 PM, [email protected] [KurzList]<[email protected]> wrote:
Group:I have played my PC-88 for around 12 years now and finally burned out mypower adaptor ( Class 2AC Adaptor
Model:PP95-20
Output:AC 9.5V 2.0A)
I recently ordered an adaptor billed as working with the PC-88 but the adaptor is 9V and the one
made for the 88 is actually a 9.5V.
To get to the point: Does anyone know where I can find the correct replacement? i.e., the adaptor named above
Thank you!
Brent Larimore
[email protected]
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