Not getting 11-12V from the boost cirtcuitry

[noromamai]

So I finally got the schottky diodes and finished populating the pcb. It was not automatically switching to 4:3, so I measured the voltage on pin 8 and it is only 7.4V. I double checked all the resistors (R1, R2 and R3), removed them from the pcb as well and the values are all correct. I have also changed R3 to 0 Ohm as well, but the voltage stays at 7.4V. Any suggestions as to what I should check?

[screwbreaker]

R3 have no effect if you are measuring without connecting the SCART to the TV.
You should get around 11V on pin 8.
Try to check the voltage on the feedback pin (pin 3) of the TPS61040DBVR, it should be about 1.3V.

[noromamai]

The feedback pin is not giving anything. Faulty chip? Maybe I took too long using the heatgun and damaged it.

[noromamai]

Replaced it with aonther one and it is exactly the same. When the scart is connected I get around 4.6V on the V(in) and around 4.3V on pin8. FB measures 0, but I have around 1.3V on SW. I don't know enough about this, but maybe I was given the wrong IC which has FB and SW the other way around?

[screwbreaker]

From those readings, seems that the IC is not switching. What you get on pin 8 is the 5V minus the voltage drop on the two diodes.
Is seems strange that you get the wrong IC, where did you got it?
Check the voltage on the enable pin (4) it should be the same of the VCC (pin 5).

[noromamai]

Looks away in shame... cough aliexpress cough. We don't have any company selling electronic parts, shipping from digikey, etc. is quite high for just a few components. Top of the IC says PHOI as it should and does not go away after rubbing it with alcohol. Voltage on the EN pin is the same voltage as VCC. Measuring again while connected and turned on, I now only see around 0.6V on SW. Can I test them by just clipping GND and 5V to VCC + EN and then measure what is on SW and FB?

I will try to populate another pcb and be extra careful about the parts and see what happens

[screwbreaker]

VCC and EN are connected together, do not try to put EN on GND or you short out VCC. EN must be at VCC.
To measure the SW pin you must use an oscilloscope. No way to check it with a multimeter.
Just to be sure, are you measuring it correctly? I mean, don't use the schematic for the pins reference. In the attached picture I marked the FB pin.
Can you post a picture of the PCB?
Give me the link to the Aliexpress seller. I can try to get some and check if they are good.

[noromamai]

I have been using your Mega Drive schematic and TI tech doc of the part, which shows the middle pin to be FB. If the pin you marked is FB, then I did get 1.3V on there, but the last time I measured it was only 0.6V.

This is the link to the AliExpress shop: https://a.aliexpress.com/_EGujjHC

I have already ordered 10pcs again from a different seller as well.

(I have cleaned the pcb several times with IPA after taking this photo)

Any reason why schematics and tech doc pinout is different? (just curious)

[screwbreaker]

That's common in electronic design, pin on the symbol are arranged to make the schematic more readable.
The purpose is to make clear how the circuit work. There is no need to match the same pinout of the real IC. Especially because most of the time the same IC is available in different packages with a different pinout.
In the datasheet you have to watch the pinout page.
The central pin is GND.
So you do have 1.3V on the FB pin. That's odd, because this mean that you must have 11V on the output.
Can you measure again R1 and R2? You can measure them in circuit no need to desolder them. R1 must be around 1.5, 1.6 Mega Ohm, maybe it will take a bit to reach a stable value due to the capacitor. R2 must be around 200K. The measure in circuit can be a bit off but it is ok.

[noromamai]

Measured R1 and R2 in circuit, but values were a bit off with what you indicated, to i desoldered them and measured again and both were correct. After putting everything back again I measured the voltages with the scart connected and not connected. When it is not connected I get 1.3-1.5V on FB. The rest of the voltages are as below.

scart not connected

scart connected

another batch of the TSP61040 should be arriving in a week or so.

[screwbreaker]

I've ordered some too from the link you provided.
But that is really odd. Can you try to replace the inductor?

[noromamai]

Replaced the inductor and am getting the same readings. It was even from a different batch. Only things that have not been replaced yet are the caps.

[screwbreaker]

The measurement you took are really strange. Try to remove C2, just for test.

[noromamai]

Removed C2, voltage measured is the same. About 4.7V as well. I also removed C3 and get the same readings.

[screwbreaker]

C3 is mandatory, the boost converter can't work without. C2 is only for stability and if broken can mess up with R1.

[noromamai]

Working! I am getting 11.2V on pin8 now.

1. thank you for your patience and sorry for wasting your time.
2. learned a lot again
3. I forgot to solder the cap for C0.

I was making another PCB for my Twin Famicom/NeoGeo AES (this one was for the PC-Engine Duo) and went through everything again and then saw C0 needed to be populated, checked on the PCE scartpcb and saw it was empty...

Video is very noisy, wasn't at first, so that's the next puzzle to solve.

And the offer was serious, if you ever visit Amsterdam, drop me a line.