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[MOD] Puhui T-962A Reflow Lötofen (IR+Lüfter)

Lexel

Flashaholic**
12 Dezember 2016
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After using a hotplate in addition to a hot air gun for quite some time I wanted to upgrade to more professional gear
Problem is real professional small reflow ovens cost 2,000€ and up

Chinesse start at about 170€ but come with a lot of issues

I have chosen the T962 Series Model A that is a bit bigger than the 962 for 280€ shipped in EU
I bought this in EU because I doint want to have trouble with customs because its basically nowhere near having the requirements for a CE label

Even if its not the worst you can read on every spot about this oven, in my opinion this is the most severe issue to be fixed first

1. mains earth is a mess on this thing

most parts are not grounded at all, worst case is only the one screw of the socket is grounded rest of the whole case not
- removing paint on the back panel (and yes a lot hot melt glue on this oven, hope the insulation is good)
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- using a proper washer with teeth to follow the safety rules for grounding (even if its a bit rusty dicovered later on PC on that Macro image)
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- Now also a washer on top (a recycled one from some old gear that had seal paint)
and a bridge to gound the other parts both with safety nut not the original crap
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- removing paint on the 2 main housing parts forming the top and bottom
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- crimping connectors with a professional tool
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- will also add here on reassembly 2 “teeth” washers

- rewiring the 2 phase switch actually to switch N and L, was before only one conductor both parallel
so now the switch lights up
and it swithes mains and L+N off (the sockets are here in Germany have not a fixed position for L)
IMG_5692.jpg


- grounding the front drawer as the metal parts do not make proper contact a lot of grease on the mechanical parts
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2. Replace the “stinky” tape

First you can read on all forums and blogs ect. about all those ovens
– you got to remove the masking tape, because it will burn and stink horrible
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- and replacing with Kapton tape
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- Then I read dont forget the hidden tape on the drawer junction
facepalm.gif

replaced with more Kapton tape
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- I did a larger area of the top covered than originally
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3. remove hot melt glue on front window

they simply used hot melt glue to fix the position then applied silicone, but seems they wanted to get production time as minimal as possible so they leave it there and assemble asap
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also one thread was messey
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Mod material
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4. 13.5dBA 40mm case fan

original: SanAce 40
40×15mm, 0.11A, 8,000 RPM, 33dBA, about 15m³/h
The frame mounted to the protection cover inside the case, this also makes some recirculation
T962-A_fan.png


Cooltek Silent Fan 4020

40×20mm, 0.05A, 4,000 RPM, 13.5 dBA, 11.5 m³/h
2.99€ shipped with Amazon prime not 9€ Ebay
I mounted the protection frame outside to eliminate recirculation
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5. Cold junction Mod and new firmware
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6. hot air circulation fan
ordered today one that hopefully can be made fit
I am pretty sure I got to move the middle termocouple hole from the current position, but getting the termocouple mounted on same place as before or mount a smaller fan blade
PS I removed both thermocopuple tubes and placed the fan in the middle of the compartment


First taking off the top cover which was screwed down with 4 scres that were below the amulinum tape, but easy to locate
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And more of the stinky masking tape

hot air oven fan 230V AC motor
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open compartment with the IR tubes exposed, I measured those below the rated power, maybe replace later IR camera test will follow to see if the boards heat up evenly
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fan blade made from aluminum, have simple bent it so it fits below the IR tubes and the compartment top cover
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as the compartment is from thin steel, so I used a 4mm aluminum plate that I found in my used metal box, already marked the drill spots using the old mounting plate
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I used 5 washers to lift the mounted fan motor enough to clear the IR tubes, holding it in place unscrewed fitted,
screwed down it was stuck on the IR tubes but as I had about 2mm distance from fan wheel to the cover
I added one more 1mm thick washer and that was enough to make it spin freely
IMG_5723.jpg


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7. hot air fan switch and manual override of cooling fan and IR tubes

proper holes made for them, but I might buy another switch for the fan so I can manually disable the cooling fan when IR tubes are manually on
will see if the profiles work good enough so no manual heating on the end of the cycle is needed
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wiring switches with heat resistant silicone wire
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drawer was modded with lifted PCBs, simply 3mm screws with fitting washers and threads cut in the PCBs
so the boards are thermally decoupled from the drawer
the bigger one got the 2 original thermal probes attached with SMD hot glue
IMG_5727.jpg


8. unhappy with heating up, not enough power, hot air circulatuion unusable

I measured the heating power with 800-900W depending on filament temperature

not enough especially when the hot air circulation is on the board temperature raise is way too slow to follow the reflow profile

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here I had the hot air fan only on during the soak phase the lamps on at 100% barely getting the temperature stable
then I switched it on at peak temperature and cool down

I ordered now 6 1300W tubes 10 inches long
having the tubes connected as pairs in series I get 1950W
this should be sufficient and the 10A electronic relais should handle that with no problem
P=1300W*6/4



also 12 of those holder which schould fit the compartment, I may have to add a few mm to make the tubes fit the spring loaded contacts properly


also the cool down is a bit slow I think about removing the back side slots and replace that with a steel fan protection for less resistance for the air flow
FOPVT7WHFWSV3E4.LARGE.jpg


the used fan is an EBM Pabst 4656N with 230V 19W 160m³, nothing to change there to improve much in the same size

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I had a look in my fan box and having on hand 120mm a 19 (same model) and 20W 230V one
as well as a 150mm 39W with 405m³
I guess I go for the big one mounted outside, just need to order a fitting fanprotection

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cutting hole just with hand cutters at it in the middle of night here, tomorrow I will get the jigsaw
the metal quality is very bad sometime the steel simply broke when bending it outside to cut next part

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also the feet need to be replaced as they smear black stuff when moved without lifting completely

bite out all the old fan slots
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Used a saw to remove as close to the new smaller marking then a Multitool to grind the rst away
also drilled holes for new fan
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taped the inside insulation to prevent air from blowing inside it, now all air should go into the PCB compartment
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threads cut
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FAN!
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9. installing new heating tubes, I have chosen replaceable with holders, so if one blows its easy to replace

- first I searched for some 6-10mm thich aluminum plate, as the 10 inch tubes with the 30mm holders are 6mm to short and I need some spring pressure
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- sawing the piece in half and adding threads
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- removing old tubes and hey they really got Kapton tape in their factory but dont use it where the cheap masking tape is used
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- Of course after I put it together I realized I sawed and added holes for tube mountings of one side all mirrored
facepalm.gif

so I had to rotate all holdery by 180° of course 12 new holes and threads
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and I am an idiot didnt thing about the wires, of course the top part closes leaving only a circle where old tubes were

- so now taking that thing completely apart and drilling holes througn where the holders are and for electrical safety I used a cone drill bit to remove all sharp edges
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- now also the oppotrunity to completely seal off that fans air tunnel so the air moved through the chamber not inside the top housing
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- I decided for more safety and electrical wiring to use this time not 230V for the heater wired to the front manual switch
so I looked up how the heaters Triac control voltage is wired on the board
it is coming from the MCU then goes 2 times through an inverter which switches ground
as I do not plan to blow that inverter I simply added a diode with 1kOhm between its output and my manual switched ground
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- 2kW tubes are different type more like conventional red light tubes but driven at 115/230V 2 in series
now the compartment got a nice red glow during heating where the original heat elements were barely visible
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  • Danke
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Lexel

Flashaholic**
12 Dezember 2016
1.261
1.199
113
Halle (Saale)
Final summary:

– Hot air oven out of the Box

electrical safety is absolutely noneexistent whole case was not grounded, just one screw
facepalm.gif

stinky tape which will smell horible if not removed
sucks for my understanding what I expect from a good product
gets leaded stuff done with enough heat
but can cook or leave stuff unmolten

– new Firmware and cold junction compensation

better, but the real board temperature is way off what is measured from the sensos between the IR tubes
option to calibrate the temperature probes
still measuring air temperature on a IR oven is total wrong aproach

– Probes moved to some dummy boards

while the temperature looked good measuring the air temperature now the truth is measured, pretty disappointing
IMG_5740.jpg


– hot air circulation fails

now it shows its waekness, 800-900W heating power is not enough not even the claimed 1500W
does not work anywhere close the heating profile when hot air is on

tried to have hot air fan on from beginning, but heat up was slow so turned it off
hot air fan on during soak and peak temperature on, manually heated longer than in profile overriding heat tubes
IMG_5728.jpg


– IR tubes replaced with 2kW tubes, bigger fan and taped the fans airflow airtight

now its working like expected, air circulation during whole reflow
I can run the hot air fan all the time
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Ich hab auch ein Crowdfunding dazu gemacht, so dass die Treiberpreise konstant bleiben
https://www.gofundme.com/reflow-oven-for-blf-drivers
 
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