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Topic: Really universal soldering controller (Read 817580 times) previous topic - next topic

Re: Really universal soldering controller

Reply #2100
[quote author="afedorov"]27k + 4.7k should give 8.3V VCC
30k + 4.7k > 9.1V
I've tried feeding 12V to the original Winstar WEO012864DLPP3N00000 and it almost doubles the power consumption with not that much increase in brightness. So, 9-10V VCC is a good compromise.[/quote]

OK perfect, I will do that.

On the other hand...I bought the wrong resistors, not enough 1.5k ohm 0.1%. I couldn't justify the shipping rates for online suppliers so I had to buy some at a local shop. They only had 5% tolerance. So now I have 5 0.1% ones and the rest 5%.

Does it really matter? I have 25 5% ones so I can measure a few of them and mount the ones closer to 1.5kohm.
Should I mount the few 0.1% ones I have in some particular part of the board?

Re: Really universal soldering controller

Reply #2101
It really matter. Most of 1.5ks are in the diff amp sections and even a small difference will imbalance the amplifier. It's also important that 0.1% are thin film ones and have much less noise. R56 should be close to the nominal value, R55 may be any tolerance, but again, thin film type is highly preferable for both. R4 may be any type and doesn't even have to be 1.5k if you're using LM2675M-3.3.
If you desperate on using what you have, install your 0.1% ones at R52, R54, R57, R62, R65. Then match as best as you can R37, R42  pair. Choose R30, R35 as close to 1.5k as possible.

 

Re: Really universal soldering controller

Reply #2102
[quote author="afedorov"]It really matter. Most of 1.5ks are in the diff amp sections and even a small difference will imbalance the amplifier. It's also important that 0.1% are thin film ones and have much less noise. R55, R56 may be any tolerance, but again, thin film type is highly preferable. R4 may be any type and doesn't even have to be 1.5k if you're using LM2675M-3.3.
If you desperate on using what you have, install your 0.1% ones at R52, R54, R57, R62, R65. Then match as best as you can R37, R42  pair. Choose R30, R35 as close to 1.5k as possible.[/quote]

Thanks afedorov.

On R37 and R42 I have to mount 2k resistors because my Rs1 is 0.004ohm. Luckily I have plenty 2k 0.1% resistors because that's what I bought instead of 1.5k.

On R4 I mounted 1.8k 1% because I have LM2675M-ADJ (and I mounted 3k on R3).

That leaves us with R30, R35, R52, R54, R55, R56, R57, R59, R62 and R65.

I will select R30 and R35 from the 5% resistors to be as close as possible to 1.5kohm .

I will mount my five 0.1% resistors on R52, R54, R57, R62 and R65.

I will mount 5% resistors on R55 and R56.


But I don't know what to put on R59. Should I try the same I did with R30 and R35?

Re: Really universal soldering controller

Reply #2103
[quote author="rsre"]But I don't know what to put on R59. Should I try the same I did with R30 and R35?[/quote]
Whichever 1.5k you put in there, trimpot is anyway worse than it.

Re: Really universal soldering controller

Reply #2104
[quote author="afedorov"][quote author="Doomedahab"]35v on the emitter of q1, no detectable heat at r20[/quote]
So, if you're not getting 12V rail it's Q13 and D15 left only.
And disconnect the front board until you done back board repairing.[/quote]

Hi Afedorov, it's me again. I have re built a new back board from new components. Unfortunately, there is no 12v line on  this one either. I did have 3.3v and -600mv. I tried it on the front board, and now the 3.3v line died also. I really am at a loss. If we keep focusing on Q1 emitter, it is reading 32V. C7 is 3.3V, C8 too. D6 is 12.2V. The only difference between this board and the last is that I now use ftz705 instead of ftz605, which is basically the same part.

Re: Really universal soldering controller

Reply #2105
To add: before the 3.3 v line went out as well, emitter on q1 read 6v.

Re: Really universal soldering controller

Reply #2106
Some pics:

Re: Really universal soldering controller

Reply #2107
Doomedahab, it may be just a reflection, but cathode of D7 looks not soldered properly for me. And L1 lead on the same trace may be as well. I really don't understand how C7 and C8 can be 3.3V while Q1:E is 32V as they are on the same rail. And how can D6:K be 12V. Something's horribly wrong with the board or your measurements/DMM.

Re: Really universal soldering controller

Reply #2108
I reflowed D7 and I now have normal voltages on the 3.3v and the 12v rails. THANK YOU!

Unfortunately though, I do have itermittent Power Lost messages on the screen often followed by a reboot, but sometimes not. Wiggling the cables does not seem to trigger it.

What would be the next obvious thing to check?

Re: Really universal soldering controller

Reply #2109
Some people here had issues with 3V zeners, particularly ZD4. But be extra careful with measurements there since high voltage Vin present nearby.
Take a picture of that front PCB corner with ZD4

Re: Really universal soldering controller

Reply #2110
Here's a close-up

Re: Really universal soldering controller

Reply #2111
Doomedahab, measure the voltage (DC) on the R46 and C61. It should be around 2.4V and 0.8V, respectively.
Also, measure valley voltage on C12 (back board), should be 5V or so.

Re: Really universal soldering controller

Reply #2112
I did the following two things.

1: I re flowed the 10 position header contacts
2: I replaced ZD4 with a minimelf version to rule it out as a possible cause.

Since those changes I have not had a power loss again.

R46=2.1V
C61=0.8V
C12=5V

Re: Really universal soldering controller

Reply #2113
What is the temperature accuracy I can expect? With a JBC 2.4mm chisel 63/37 melts at 188 degrees Celsius on the display. Not too bad. When I measure the tip temperature at that setting with a knock off hakko fg100 it measures 182 degrees Celsius which is pretty much exactly the melting temp of 63/37 solder. So the cheap probe is pretty accurate.

This 5 to 6 degree offset of the unisolder is good enough for me, but the offset grows to 20 degrees at 260 degrees, and 20 degrees at 350 degrees too (the probe measures 330 while the display tells me it's on 350 degrees). This is not very good I would say. Is this what I should expect or are there ways to improve upon this?

Re: Really universal soldering controller

Reply #2114
I assume calibrating to exactly the resistor value should result in a perfect setting at the melting point of 37/63 solder with an average tip size, correct? But if I want to have a little higher temp setting to compensate for the drop in the curve, I could just turn the potentiometer a little?