Bakon 950D "Extra Crispy" mod (19->24 Volt)

[stj]

looking at the fet datasheet and the controller schem, you should use a 12v zener - or even a 14v one.
at 5v the gate resistance is twice what it is at 10v.

if your going to clamp the gate pullup at 5v then forget the diode and re-route the pullup from the 24v rail to the 5v rail.

[vinceroger69]

can size on rubycon 3mm bigger, but ripple is lower Ripple Current 2250mA
like you say the panasonic is 2470ma so yes higher
i wonder what the ripple current is on the caps that are in now.

[stj]

probably surprisingly good.
chinese c(r)aps actually often have decent specs, the problem is the unreliable lifespan.
i may have listed the specs in my review.

[Th3_uN1Qu3]

Originally Posted by vinceroger69

in picture 4 where are you measuring the output voltage thanks

Straight onto the output caps. Actually was tricky holding both probes with one hand and the phone with the other.

Originally Posted by stj

looking at the fet datasheet and the controller schem, you should use a 12v zener - or even a 14v one.
at 5v the gate resistance is twice what it is at 10v.

if your going to clamp the gate pullup at 5v then forget the diode and re-route the pullup from the 24v rail to the 5v rail.

I am using the zener in series to drop voltage, not from gate to source where it would be clamping. Hence why cutting a trace. In this case gate drive is very close to the original value of 19 volts (24-5.1 = 18.9).

[dssence]

So I know it's quite an old post but I did the mod with my bakkon 950D, I changed R11 to 22k resistor and R24 to 3.3k , I added the zener diode on the gate of the mosfet. Now here goes the problem, I changed the temp to full throttle around 450C on the display but with a thermoouple on the tip I'm getting max 320C degrees. Then I switch it off.. switch back on and it's not turning on.. what I did realise was if I fully discharge the primary eletrolytic it turns back on. So I think something is going on with the OB2202. I thought it could well be a problem we need the current sense resisor on the primary but I don't thin that's the problem. I'll wait for your advise see what's going on.. it's a pain in the ass to have it working, turn off then back on and it's not turning on unless you discharge the primary electrolytic.

[stj]

russian guys changed the overcurrent sense level - that's probably it.

[dssence]

Originally Posted by stj

russian guys changed the overcurrent sense level - that's probably it.

Yeah that's what I thought. So what do I have missing? need to add 2.3ohms resistor but where? not quite sure.

[dssence]

What about this I took it from a russian blog

[vinceroger69]

Originally Posted by dssence

So I know it's quite an old post but I did the mod with my bakkon 950D, I changed R11 to 22k resistor and R24 to 3.3k , I added the zener diode on the gate of the mosfet. Now here goes the problem, I changed the temp to full throttle around 450C on the display but with a thermoouple on the tip I'm getting max 320C degrees. Then I switch it off.. switch back on and it's not turning on.. what I did realise was if I fully discharge the primary eletrolytic it turns back on. So I think something is going on with the OB2202. I thought it could well be a problem we need the current sense resisor on the primary but I don't thin that's the problem. I'll wait for your advise see what's going on.. it's a pain in the ass to have it working, turn off then back on and it's not turning on unless you discharge the primary electrolytic.

what is the line voltage in your country? as i see this quote on page one of this thread
(No need to change current limiting resistor in primary, maybe with 110V input it is necessary but for European mains voltage, no issue.)

[dssence]

Originally Posted by vinceroger69

what is the line voltage in your country? as i see this quote on page one of this thread
(No need to change current limiting resistor in primary, maybe with 110V input it is necessary but for European mains voltage, no issue.)

Hi it's 220volts here. but still I got this issue, about not turning on. Having to discharge primary electrolyitc 100uf x 400volts to restart.

[vinceroger69]

Originally Posted by dssence

Hi it's 220volts here. but still I got this issue, about not turning on. Having to discharge primary electrolyitc 100uf x 400volts to restart.

Hopefully Th3_uN1Qu3 will see this thread and may have some advice on what to change/resistor value etc.

[dssence]

Originally Posted by vinceroger69

Hopefully Th3_uN1Qu3 will see this thread and may have some advice on what to change/resistor value etc.

Yeah , still waiting for him to reply. thanks anyways for the help

[stj]

looking at my notes from russia, i suspect it's R1 or R14 needs to be messed with.

i have this line "parallel to the current resistor in the primary we add a resistor to 2.7 ohms"
nice & vague, looking at the psu schem i can only imagine they are talking about R1(0.27ohms) which is a shunt for the main switching fet.
by putting 2.7ohms in parallel you reduce the volt-drop the chip will sense.

[Th3_uN1Qu3]

It should work without messing with the current shunt, mine does no problem. Try 20k for R11. 27k (original) paralelled with 91k gives 20.822k, so 22k is a bit high and could very well be your issue.

As for tip temperature lower than expected, make sure the tip is clean then pick up some solder with it, before placing it onto the thermocouple. Any oxidation acts like a thermal barrier. When you are sure the temperature reading of your thermocouple is correct, use the built-in calibration function (described in the manual). It works very well.

[stj]

Originally Posted by Th3_uN1Qu3

Try 20k for R11. 27k (original) paralelled with 91k gives 20.822k, so 22k is a bit high and could very well be your issue..

your as bad as the russians!
can you translate that into english?

what to put in place of R11??
you previously said put 15k in parallel with the 27k factory part.

[dssence]

Originally Posted by Th3_uN1Qu3

It should work without messing with the current shunt, mine does no problem. Try 20k for R11. 27k (original) paralelled with 91k gives 20.822k, so 22k is a bit high and could very well be your issue.

As for tip temperature lower than expected, make sure the tip is clean then pick up some solder with it, before placing it onto the thermocouple. Any oxidation acts like a thermal barrier. When you are sure the temperature reading of your thermocouple is correct, use the built-in calibration function (described in the manual). It works very well.

So many thanks for helping. I'm going to try instead of 22k , 20k for R11. I remove R11 and replace it by 20K resistor. Have you seen this schematic I found in the russian forum, I was reading about the work of TL431, to see how it adjusts the voltage. But let me know what do you think about this russian schematic, will try with 20K . The weird issue is correct me if I'm wrong, Pin 7 is DEM and sets the trigger for the OVP protection, if it exceeds 3.75 OVP triggers and shuts down but I calculated with 27K and 130K voltage divider and it's within margin. If we take 24 volts and 27k and 130k it gives 3.474 which is fine, if we take 24 volts and 20k and 130k it gives 3.2 which is aso fine. So i'm interested in understanding why I got to manually discharge the primary electrolytic to make it work again. but anyways I'm going to check replacing a 20k on r11.

[dssence]

Originally Posted by stj

your as bad as the russians!
can you translate that into english?

what to put in place of R11??
you previously said put 15k in parallel with the 27k factory part.

If I'm not mistaken and missunderstand he said to replace r11 by 20k resistor.

[Th3_uN1Qu3]

Originally Posted by dssence

If I'm not mistaken and missunderstand he said to replace r11 by 20k resistor.

Yes exactly. R24 (bottom feedback resistor for TL431) is the one that needs to have 15k in parallel added, take another good look at the pictures, stj.

I did not check the Russian schematic. I did the homework on my own in the first place.

The label on the transformer showing the turns ratio helped greatly. Since the OVP is on the primary side, sensing the aux winding, and both circuits are simple resistive dividers, it follows that when adjusting the bottom feedback resistor of the TL431 to bring the voltage up, the OVP level has to be scaled up by the same ratio by lowering the bottom resistor of the OVP divider. It was all grade school math there.

I did not need to go thru extra iterations once I discovered where the OVP circuit is, it worked first go for me with the values that I have posted. Still works great, and no I haven't even bothered to replace the output capacitors yet.

[dssence]

Originally Posted by Th3_uN1Qu3

Yes exactly. R24 (bottom feedback resistor for TL431) is the one that needs to have 15k in parallel added, take another good look at the pictures, stj.

I did not check the Russian schematic. I did the homework on my own in the first place.

The label on the transformer showing the turns ratio helped greatly. Since the OVP is on the primary side, sensing the aux winding, and both circuits are simple resistive dividers, it follows that when adjusting the bottom feedback resistor of the TL431 to bring the voltage up, the OVP level has to be scaled up by the same ratio by lowering the bottom resistor of the OVP divider. It was all grade school math there.

I did not need to go thru extra iterations once I discovered where the OVP circuit is, it worked first go for me with the values that I have posted. Still works great, and no I haven't even bothered to replace the output capacitors yet.

Sounds great you didn't bother changing the output caps. Anyways to see I did understand correctly I should have to replace R11 with 20k and R24 I removed it and replaced by a 3.3k . Correct me if I'm wrong. If changing those value I still go through the issue it doesn't turn on once more. What else would I got missing, could it be a different board revision. or what the heck is wrong?

[vinceroger69]

did you cut the trace when you fitted the zenner diode? you probably have but worth confirming.