EDM 044 . Strange behavior RX TX with Uart

PS5 Questions
1

Edm 044 dead.

Replaced SB twice and this anomaly occurs: RX and TX 3.3V. If I connect uart it drops to 1.8V.

Same behavior with both SB

First time I see something like this

2

If you use a CH341A, the voltage output must be adjusted from 5V to 3.3V. The southbridge will stop working if 5V are applied to its 3.3V RX line.

3

Thanks, maybe I explained it poorly.

My CH341A is already modified/set to 3.3V and I’ve been using it for a long time without issues.

The problem only happens on this specific PS5 board:

Before connecting UART, PS5 TX and RX pads measure 3.3V. After soldering TX/RX from the CH341A, both lines drop to around 1.8V.

4

What happens if you only connect GND and the TX(PS5) to the RX(CH341)?
Does the voltage also drop?

It should display at least the measage, after aprox. 6 seconds after the power cord is plugged in the PS5.

OK 00000000:3A
$$ [MANU] UART CMD READY:36
5

same problem. Voltage drops to ~1V if connected. Otherwise 3.3V

I extracted errors from the nor:

80000009

B0088108

C0020303

I don’t know if they are related.

0.000V with bench power supply

6

Measuring voltage and reading the signal at the TX line at the PS5 is technical the same.

So I don’t get my head around why you could measure 3.3V and than with the TX(PS5) wire connected to RX(CH341A) the same line is permanent down to 1V.

The CH341A at its RX(CH341A) is basicly the same like a multimeter at this point: measuring the voltage output from TX(PS5) to ground.

7

Yes, I agree. It sounds crazy to me as well.

This is the first time I’ve seen this kind of behavior. Usually, even with a corrupted BIOS or other faults, there is at least some current draw/activity.

I’ve only seen 0.000A current draw in cases like a hard short on the 12V main rail.

That’s why I’m wondering: is this 3.3V on TX/RX generated directly by the Southbridge, with no intermediate resistors/pull-ups in between?