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

[vinceroger69]

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

i have got all the parts to carry out this mod but as your having these issues i may leave my unit untouched for now

[dssence]

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

did you mean 1000uf 35v? you put 100uf

Yes sorry 1000uf was just a typo. yes I replaced by 1000uf x 35. I think I'm going to revert all the mod and see if this still happens.

[vinceroger69]

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

did you mean 1000uf 35v? you put 100uf

[dssence]

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

91K goes in parallel with R11 (OVP) not R24 (feedback). 15K is in parallel with R24 (originally 4.42k) which gives 3.414kOhms as a final value for R24.

But yes, I agree, 3k3 is too low. 3k3 for R24 would give an output of 24.94V. Precision is needed here. That is why I decided to add a resistor in parallel, because I did not have the required calculated value.

Thanks for all the help. I finally managed to solve the issue when it didn't turn on. Now it turns on and off without having to discharge the primary electroyltic.
I did by replacing r11 by two resistors of 10k in series giving around 19.8k ohms.
Now here goes the problem, the unit sometimes starts to heat the tips and sometimes doesn't. I can hear PWM triggers sometimes and sometimes it get stuck. Any ideas about this? . I can't understand why something so simple get so complicated for me. Many people did the mod without any issues. I added the zener to the gate on the other board cutting the gate trace fine. Replaced the caps 100uf x 35 and the resistors. Can't happen to understand what could be going on. Waiting for your help.
I thought it could well be the trimmer on the other board, so I played around , but still no noticeable changes.

[Th3_uN1Qu3]

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

91K goes in parallel with R11 (OVP) not R24 (feedback). 15K is in parallel with R24 (originally 4.42k) which gives 3.414kOhms as a final value for R24.

But yes, I agree, 3k3 is too low. 3k3 for R24 would give an output of 24.94V. Precision is needed here. That is why I decided to add a resistor in parallel, because I did not have the required calculated value.

[stj]

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

R24,
russians replaced it with 3k6 for 23v
un1qu3 bridged the original 4.42k with 91k

3k3 is going to give well over 24v

[vinceroger69]

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

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

[dssence]

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

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?

[Th3_uN1Qu3]

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

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]

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

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.

[dssence]

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

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.

[stj]

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

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.

[Th3_uN1Qu3]

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

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]

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

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.

[dssence]

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

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

[vinceroger69]

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

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]

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

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]

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

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]

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

What about this I took it from a russian blog

[dssence]

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

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.