Fixing A Quite Annoying Tristar PD-8781 Air Fryer Problem
My at least over a year ago bought Tristar PD-8781 Airfryer still worked excellent in frying my meals, late night dinners or my daily snacks. And I only had replaced the defect halogen lightbulb about 8 months ago by a new fitting led light bulb. Which was quite difficult because I only was able to open it just far enough to reach for the lampholder to replace the old glass bulb. That original lightbulb got defect after the case trembled too hard so that it must have broken its lamp spiral filament.
And until now I wasn’t able to find out how to disassemble the airfryer top to reach for all other internal parts or the front panel board. But now I had no other choice because the airfryer since about 6 months ago started to behave erratic in that it started to frequently raise the temperature upto its max 200 degrees Celsius. But after it had already reached that maximum temperature setting it kept trying to raise it even further by constantly beeping when it again tried to raise its temperature as if someone had touched the temperature-up touch selector.
So although it wasn’t pressed it automatically kept on raising the temperature to its max even after I had lowered the temperature again with the temperature lowering touch button on the frontpanel. Which was very annoying and simply had to be fixed.
Next photos show how I finally managed to correctly open the airfryer completely so everything could be examined further. The solution was found in removing the on the top clipped in grey colored square ring. For this I used one of my Sanhooii tools. Using the flat metal ‘spoon’ shown in the previous photo worked great in carefully unclipping the 11 clips on the grey square plastic top ring. And the previous photo on the right of the Sanhooii tools photo showed that top grey square-ish ring. Before this I was only able to remove the bottom half just far enough to reach for the light bulb on the back of the airfryer oven by removing the bottom screws. And I also had to adjust the plastic case on the inside backplate a bit so the Led replacement light bulb could be fitted correctly in the limited lamp holder space because the previous Halogen bulb was smaller. Replacing the Lightbulb with a new Led light worked perfect until this very day and also saves some energy on used power. Following photo shows the label sticker that is attached onto the bottom of this airfryer.
Previous photos showed the top grey ring after it was completely unclipped. And after that grey ring is removed also the black top plate can be removed. By first pressing back in up direction the front 2 clips, and then the 2 clips in the middle. After which the black plate gets further removed without breaking any of the clips. Next photo shows this top plate upside down with all 6 clips. And on next photo on the right the two top screws that here still hold the frontplate in position that hooks into the bottom of the oven.
Above photo shows the oven after the front plate with the selector touch buttons was removed. I placed the 2 top screws back so to make sure what screws are needed where. 2 cables were removed from the front plate connectors. They go to another board inside the oven that powers the relays that switch the Fan, Heater, Motor and also switches the oven by using a triac type BT136. On next photo the 4 white arrows mark the 4 screws that were removed so also the black top shell could be removed. After that the power board was examined that was fastened with only 2 screws.
The board marking was Power-V5. 2-02 2019-12-25. See next photos that also show the type of relays used and the mentioned triac BT136. And after checking all parts and checking the solder side I noticed that it was nicely varnished. Strangely the front touch selector board was not varnished at all on its solder side. But none of the components were out of spec or damaged. The 2 e-caps on the touch button front plate tested fine and were both 220uF 10V. The touch panel board had 2 smd IC’s. One was a 24 pins AIP1624 which was a led driver chip, and the second was a unknown 28 pins smd chip marked TB6203ATF28. The chipmarking TBxxxx here most likely means Touch Button circuit.
Above on the left the EL 817 optocoupler on the power board. Photo on the right the oven with closed door and removed touch button front plate, and removed grey ring and black top plate. Next photos show the touch panel board front side.
All springs are covered with next front plate that is screwed with 4 screws into the back of the dark black transparent frontplate. The front plate that was screwed in place on top with the 2 screws and was clipped onto the bottom of the front of the case.
Next photos also show this touch panel and how this touch panel board looks with the oven powered on. Which is what gives this oven a special touch so to speak!
Above photo showed the solder side of the not varnished touch panel board. In the white glue both white cable connectors look almost hidden. The 8 pins wide connector and the smaller connector next to it are better shown on below photo on the left with the unknown TB6203AF28. And photo on the right shows the AIP1624 Led driver IC.
Above photo shows another close-up on the springs on the touch button panel board.
After I checked all passive components and couldn’t find anything out of the order I assumed that this annoying temp up touch button problem was only caused by the touch panel board. And because this board wasn’t varnished, and it also was placed at the same height as the power board, it only seemed logical to also carefully varnish only the solder side of this board. Which I did. But I first covered the top of both white connectors with some tape so no spray could enter these.
The moment the solder side of the touch board panel was dry enough I re-assembled the airfryer oven and did a few tests by cooking a few snacks. Two mini Pizza’s and a Baguette Hawaii were cooked/fryed. Each took about 10-12 minutes. And the annoying pushing up touch button problem indeed was finally completely gone in the about 30 minutes the 1500 Watt airfryer did his splendid work.
Next last photo shows how the new (yellow) Led looks on the inside of the oven, that now replaces the old original Halogen light. It is originally protected against the oven heat by a special inside transparant cover plate.
I am very glad that my Tristar PD-8187 airfryer is no longer driving me nuts with the erratic pushing up behavior of the temperature-up touch button. Which also beeped everytime that happened.
Again another repair at almost no cost except at the expense of enough spare time to finish the job satisfactory! Unexpectedly this was also another repair that involved using varnish spray to cover and solve a problem. Why I also make sure to always have a spray can or two with clear varnish at hand.
Albert van Bemmelen, Weert, The Netherlands
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david shapira
December 22, 2022 at 2:12 pm
Nice repair
I like to ask way you assume that varnish will solve the problem.
Albert van Bemmelen
December 22, 2022 at 7:48 pm
It was a logical conclusion because the power board was already protected against moisture from the heating oven. And both were at the same height above the fan with heater element. Also because the touch 'buttons' were probably sort of capacitive sensitive sensors. There was not much else that could be enhanced or upgraded because all parts were within spec. And it completely did solve the problem!
Imoudu.O
December 22, 2022 at 3:04 pm
It must have taken more of your time to disassemble this unit.I wonder what that vanish spray did on the board to perfect it.Thanks for sharing and have a nice day.
Albert van Bemmelen
December 22, 2022 at 10:32 pm
Most likely the condensation of the moisture in the hot air now no longer can reach the sensor contacts of the touch board through the with a layer of varnish protected solderside. The touch board frontside with the touchsensor springs of course was left uncoated!
Parasuraman S
December 22, 2022 at 7:24 pm
Vow! Do much complications involved in disassembling! Oh my God! Anyhow, your professionalism solved the problems! Well done!
Mike retz
December 23, 2022 at 9:20 pm
Hey cool article. Need to write a book on taking things apart and all the little tricks you have to figure out. Great article thanks and have. A great holiday️️
Mike retz
December 23, 2022 at 9:21 pm
Hey cool article. Need to write a book on taking things apart and all the little tricks you have to figure out. Great article thanks and have. A great holiday️️
Albert van Bemmelen
December 24, 2022 at 5:12 pm
Thanks Mike, have a great holiday too!
Justice Cele
December 29, 2022 at 4:55 pm
In my language I would have said "Angazi" to the client (meaning I don't know). But in the future i will have to persevere like you did albert, thanks for the article.
Albert van Bemmelen
December 30, 2022 at 11:30 pm
Thanks for your nice comment Justice! I hope that finding those clear varnish spray cans won't be a problem in your country. Because recently the shop in my hometown (Action) no longer had any cans in stock soon after my article was published! I hope that this was only temporary.
Yogesh Panchal
January 8, 2023 at 11:45 pm
Well-done! Albert,