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I also need help finding replacement transformer for oven control board-

Discussion in 'Datasheets, Manuals and Component Identification' started by jonj222, Oct 19, 2019.

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  1. jonj222

    jonj222

    9
    1
    Oct 19, 2019
    After hours of googling and asking questions online I finally got my search phrase right and found this site. I accidentally hooked up my used wall oven wrong and blew the transformer. I would like to see if I can undo my wrongs and get the oven working, both to unburden my guilty conscious and learn more electronics along the way. The control board is no longer in production and I have had no help getting the specs on the transformer so I could get a similar one and rig it into the control board. If all this fails no big deal, these 24-inch
    wall oven pop up on Craigslists all the time when folks remodel their kitchen. I will upload the pics. I also have the wiring diagrams that came with the unit. As I look and relook at them I sort of get a Gestalt of how this thing operates.
    thanks

    IMG_20191018_204716201.jpg
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    Last edited by a moderator: Oct 24, 2019
  2. Minder

    Minder

    3,144
    679
    Apr 24, 2015
    It appears that you may have blown what appears to be the thermal fuse on the outside of the transformer winding, It my be worth a check as if it is, it should be easy to fix.
    M.
     
  3. jonj222

    jonj222

    9
    1
    Oct 19, 2019
    Thanks for your replay and help. I pulled the transformer off the control board this am. There was a thermal fuse on the underside of the transformer. The fuse was marked 168C 086 and 240V 1 Amp. There was no continuity across the fuse. I also got the taper off the top side of the transformer where I saw the leaking and discolouration. It appears that came from the tape melting as the primary coil heated up. I can not tell if it also melted some of the windings. I get no continuity when I try to check them- but I am not sure if I am checking them right. I have included some pictures.
    thanks again
    Jonathan

    IMG_20191020_104946582 (1).jpg IMG_20191020_110352020.jpg
     
  4. Minder

    Minder

    3,144
    679
    Apr 24, 2015
    You should be able to locate an equivalent fuse, checking the primary pins will show open with the fuse blown, jumper the fuse and re-check continuity.
    Also if you do identify it and connect 120vac while out of circuit, you may be able to identify the secondary voltage(s), In order to look for a replacement if needed.
    Jumper the fuse to do this.
    M.
     
  5. jonj222

    jonj222

    9
    1
    Oct 19, 2019
    I did jump the fuse and after some fiddling, I DO have continuity. So now to find the thermal fuse. Thanks so much for your help. Would not of gotten this far without you.
    Jonathan
     
    Minder likes this.
  6. jonj222

    jonj222

    9
    1
    Oct 19, 2019
    Well, I am a little premature, probably due to exuberant optimism, that I had it solved. There is NO continuity in the primary winding with the fuse jumped. Under closer inspection I do not see two wires coming out of the primary coil, only one that is mated with hot in. There is a pin for the neutral on the transformer but no wire connected to it. I had powered it up this am as you suggested but I go no outpt voltages to read on the secondary side, which led me back to the primary side being non functional, and a closer inspection of that revealed the above. I am stumped as to where to go from here. thanks
     
  7. Minder

    Minder

    3,144
    679
    Apr 24, 2015
    Presumably there should be a connection to the neutral pin!
    Do you get continuity from one of the fuse terminals to this neutral?
    What is the one 'mated' to the supply pin
    M.
     
  8. jonj222

    jonj222

    9
    1
    Oct 19, 2019
    That is what I would assume - a connection to the neutral- but no I do not see anything. Maybe it burned off with the 120v applied to it?? Rechecking this morning I do not get continuity from either one of the fuse terminals the neutral. The only connection I see is a small braided wire that comes from the primary coil to the supply pin. It is all so small and tight it is hard to take a picture of it. I will attach a picture of how the wiring looks to the pins on the secondary coil to give a sense of it. I have an email out to one of those
    IMG_20191021_193718616.jpg
    control board fix-it shops asking if they would share the secondary coil output specs with me. I tried to make it a sad as story that I could. I am not holding my breath. I meant that the only wire I see exiting the primary coil goes to the line in pin on the control board. above is the image from the secondary coil to the pins.

    IMG_20191021_173225506.jpg

    Here is as close a pic as i can get in focus to the primary coil. The twisted wire is the bridge connecting the two pins that used to be connected by the thermal Fuse. there is a tiny wire exiting the coil that is down low in the pic that loops around and is soldered to the pin. ( the other pins are gone b/c before I know how to get the control board opened up - it had two-layers- I tried cutting out the transformer. I then soldered 3 wires to the cut-off pins-down low so I could both test it and connect it back to the control board. The black wire would be the line in and the white the neutral.
     
    Last edited by a moderator: Oct 24, 2019
  9. 73's de Edd

    73's de Edd

    3,214
    1,347
    Aug 21, 2015
    Sir jonj222 . . . . .

    In consulting your units wiring diagram :
    OBSERVE . . .
    At the top we see full 220 VAC coming down as a wire at each side of the schematic and the right Neutral passes down to the right and turns to the left and connects as a WHITE wire to a push on connector N.
    The other sides wire routes down at the left and reverts to turning to the right and connects as a BLACk wire to the L1 push on connector.

    Now stoves are using a full 220VAC, so that wiring shows that the transformer primary is being connected to the L1 and N connections and will be receiving 220VAC AC power on the transformer primary . . . .24 + hrs a day !
    BUT these transformers are wound as a high impedance primary which means many more turns than normal so that the transformer runs cooler in being run at constant power on. The secondary windings are scaled accordingly. Just enough power from the transformer to meet maximum needs is produced.

    That then leads to your comment of . . .
    I accidentally hooked up my used wall oven wrong and blew the transformer.
    In which case, that transformer is permanantly hooked in circuit all of the time and runs on a full 220 on its primary winding, so I don't see how you could get MORE than 220 V into its primary to " blow " it.
    You must have just got some external wires / connectors together for he spread out big blackening deposit . . . . however I don't see any burnt off connectors or melted copper blob deposits.

    However, you did find the opened thermal fuse in the transformer primary.

    Now I don't know if time, heat and age may have caused the winding of the primary to break down and cause a shorted turn(s) or cluster(s) thus creating a constant further heating and current consumption of the primary.
    OR . . . . . if you are lucky a close to the utility pole / line transformer lightning hit in an electrical storm, may have knocked that fuse open. ( But I really would suspect the winding opening up first. )
    Otherwise, its being a thermal rise made of a meltable fuse link that opens its circuit upon exceeding a fixed heat threshold . . . . plus you can see its CLOSE proximity to the winding, for heat sampling.
    (Sometimes you even find these being physically placed deep down within the unit pressing against the core.)
    Since you now have the yellow insulative covering away from the primary half, does the magnet wire windings surface seen to show of any discolorations, as being subjecture of having heated up in the past ? Or any bubbling / wrinkling or discolorations of insulated wraps at their edges, being used on successive winding layers deeper on down , towards the core ?

    Evaluating the transformer . . .

    The transformers other halfs secondry winding, will be a little harder to be able to confirm what its nornal AC voltage outputs are.
    It would be mainly dependent on your initially viewing the different wire colors used and associating the number of separate windings connected to them.

    I somehow feel that I am not seeing ALL of the secondary windings wire terminal stakes coming out, but I do count 4.
    What is of SUPER- UTMOST importance now, is that for the first few seconds of testing that transformer, is that you get AC measurements on those secondary windings.
    Replacing that thermal fuse might get things working all fine again. But if the secondary voltages are unknown, you will never find them with an open primary.
    That info you just DON'T find being available, without having a good working unit for voltage comparisons. ( FAT CHANCE )
    Now there is still the posibility of overheating of the transformer and destroyed insulation letting a few turns short together. That could be the basic transformer fault, as that will cause the transformer to heat up.
    Also, the secondary windings voltages will be a wee bit higher than is normal.

    If my situation to solve . . . . I would be doing this procedure . . .exactly . . . .. . . . .

    I would get 4 (or more) pieces of insulated hook up wire 2-3 feet long to be able to strip ends and tin and then solder to the 4 (or more) terminals of the transformer secondary. Run them out and take the other ends and strip enough insulation away to make a 1/8- - - -1/4 in round twisted eyelet to facilitate meter probing contact area.
    Firmly tape them to a heavy piece of corrugated cardboard with each of them slightly spaced apart. Number each terminal.
    That leaves you with a then slightly remoted, easier access to the measurements of the AC voltages on that transformer .
    They are isolated from your 220VAC on the primary and being a safe " cold" voltage.

    I came to a stop here . . . . . after reading your latest post . . . . and the bad news right there in River City .

    Now look at the transformer drawing below and see if it is agreeing in the wiring hook up to your transformers wire terminal stakes.
    On one pic I think that I can see a fine copper wire coming from the end of the winding and ruting as I have added in the RED color coded route and wrpping around the D terminal stake. That stake also takes a wrap around from the BLUE lead of the thermal fuse and the fuses other GREEN lead wraps around C stake.
    B stake is unused.
    The all important A stake takes the fine ORANGE coded primary wire that is routed deep down and starts as the beginning of the primary winding. God forbid that you loose sight of that CRITICAL fine wire or at least a visible tip, so that a fine bare wire can be tinned and then the visible tip scraped and tinned and then a solder drop joins the two then they lift up so that an INSULATIVE drop of epoxy can be made to ensurround them, and be spaced away from the core metal..

    upload_2019-10-23_4-44-22.png



    HEY . . . you finally gave a view of 5 terminals being on that secondary, I could not fathom only 4, with my suspicioned needs of that transformer delivery requirements.

    As is being shown here. . . . . .

    upload_2019-10-23_4-44-59.png


    Also, you never gave a pic of the front of the unit but this ***** shows an electroluminescent type display which would need a negative 50-70 v supply and a filament supply of ~3-4 VAC. Then the 6-12 VDC supply needed for the power relays coils and a minor +5 DC basic logic supply. Since you also didn't show the logic board / brains in the center of the unit .

    ***** DISPLAY . . . . .
    https://cdn2apex-control-boards-9tl...ntent/uploads/2019/05/DSC_0002-1-1.jpg?iv=323



    Suspicioned needs of the power transformer . . . . .

    Back to referencing to the bottom half of the top pic of the transformer, where I suspect the VIOLETS to be one sole winding .
    Then the BROWNS will be another separate isolated winding. Then a connection between the end DARK BROWN winding and one of the ends end of the BROWN winding would replicate my other transformer wind shown above.

    Get a BRIGHT light, magnifier lens and then see what you can find of the errant, very fine "orange" . . . start of winding wire.
    ( Finding The OTHER end is a piece of cake.)

    I pause . . . .


    73's de Edd . . . . .


    If a cow laughed HARD , would milk come out her nose ?

    .
     
  10. jonj222

    jonj222

    9
    1
    Oct 19, 2019
    Thanks so much or your input. I have been tied up at work but will respond tomorrow. Let me fess up to my misdeeds. The stove came with 4 wires- red, black, whte, and neutral. l wire the circiut with a 3 wire Romex cable , black, white, and a bare neutral. Both the black and white were hooked to 120 v at the panel - so I could get the needed 240 volts to the oven. What happened next I can not even explain to myself. I hooked the black to black, but instead of white to oven red, I hooked it to white- the oven ground. The control panel lit up and looked fine then 30 secs later I heard a loud pop and the control panel went dead. More late...
     
  11. jonj222

    jonj222

    9
    1
    Oct 19, 2019
    I can not find the wire that connects to the neutral pin of the primary winding. In addition, the primary coil is shorting out to itself- see picture. I am not user how the primary is getting 240 v as it if was working it is only getting 120v in. I also included more pictures of the control board- there are tow half- one has on the display on it. It is stuck in the housing and would take some doing to get it out of the housing. Lastly, I have a picture of the ribbon going to the push button. As you can see it has a voltage rating of 36 v dc. Thanks for all your help but I think the transformer is not salvageable and unless I know the specs have no way to buying another one and rigging it in.
    that is unless you have other idea's. Overall I am not that bummed b/c I learned a lot in this process.







    IMG_20191024_062207300_BURST001.jpg
     
  12. jonj222

    jonj222

    9
    1
    Oct 19, 2019
    The program is not letting me upload the rest of the pics. Will work on it. The only info I have to add it that the switches on the control board that go the oven and broiler - large square blk boxes - are rated 12 v dc 30A 240 VAC
     
  13. davenn

    davenn Moderator

    13,894
    1,969
    Sep 5, 2009

    yeah I noticed
    You are trying to upload ones that are too big
    resize them to ~ 1000 x 700 max and ~ 100kb max and crop them where possible so only to show the item and not lots of pointless desktop :)
     
  14. jonj222

    jonj222

    9
    1
    Oct 19, 2019
    IMG_20191024_060055068_BURST001.jpg IMG_20191024_061740979.jpg IMG_20191024_061936208.jpg IMG_20191024_210135039.jpg
     
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