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Need Help with oven control board transformer

wuoshi1031

Feb 23, 2017
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I am trying to replace this Basler electric transformer that I got off of my oven control board, it seemed to have burned out when I took it off the board.

I am typically fairly good at finding related information when it comes to google, but for some reason I can't find anything generic equivalent transformer.

Was wondering if anyone has any advise on how to find a replacement transformer (a new relay board runs about ~160), I am hoping to repair my oven under $20...

Baselor transformer.JPG
 

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wuoshi1031

Feb 23, 2017
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Trying to repair my oven relay board. It burned out this weekend, opened it out and found burn/smoke marks on transformer and when tested with volt meter, the transformer has no output. i am still fairly new at this so trying to see if anyone can point me to where I can buy a generic equivalent, i've googled up and down but still not having any luck...

Oven: Kennmore electric range

Baselor transformer.JPG unnamed.jpg
 

73's de Edd

Aug 21, 2015
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Sir wuoshi1031 . . . . . . . .

Can you sniff right at the windings of that power transformer and confirm a strong odor.
I am expecting the primary of tha unit to have an open thermal fuse and it is placed so that it is pressed right up against the core and its windings . . . . its basically hidden internally except for its two slightly larger 2 silver leads that come out to be wired in SERIES with the transformer primary..

If this is the case it could be bypassed for just a few seconds of test time to power up and immediately measure the AC voltage output of the transforemr secondary to see what its output voltagte is.

I am expecting 24 or 20 VAC that then gets rectified and divided down to lower voltages for the systems relays and display.

Check out your unit, as compared to this reference below to see if that units thermal fuse has opened on the transformer primary winding .
Also determine the secondary winding numbers . . .1 . . .2 ? on the other terminals on the other side of the transformer.

TRANSFORMER REFERENCE PHOTO

8qcKl1s.png


73s de Edd
 
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wuoshi1031

Feb 23, 2017
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73s de Edd, thank you.
I've located the thermal fuse and tested it as well. it seems to be working and not open.
I notice burning marks near leg 1 and 2, and the solenoids attached to leg 1 seem to have burned off/thin out.

I have hooked up the transformer to power but nothing is coming out on the other side. The transformer actually looks very similar to the one you posted. I will post picture on the other side shortly when I get home.


Sir wuoshi1031 . . . . . . . .

Can you sniff right at the windings of that power transformer and confirm a strong odor.
I am expecting the primary of tha unit to have an open thermal fuse and it is placed so that it is pressed right up against the core and its windings . . . . its basically hidden internally except for its two slightly larger 2 silver leads that come out to be wired in SERIES with the transformer primary..

If this is the case it could be bypassed for just a few seconds of test time to power up and immediately measure the AC voltage output of the transforemr secondary to see what its output voltagte is.

I am expecting 24 or 20 VAC that then gets rectified and divided down to lower voltages for the systems relays and display.

Check out your unit, as compared to this reference below to see if that units thermal fuse has opened on the transformer primary winding .
Also determine the secondary winding numbers . . .1 . . .2 ? on the other terminals on the other side of the transformer.

TRANSFORMER REFERENCE PHOTO

8qcKl1s.png
 
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73's de Edd

Aug 21, 2015
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Sir wuoshi1031 . . . . . . . .


I have yet to see that backside / foil side of that board.
Your L1 and L2 AC line hot connectors look a bit darkened close to the board proper.
On the foil side of the board, you might find some high current carrying connection that has cratered out and is having some arcing connection developed at the FAN /or/ BAKE /or /BROIL relays.
That could then account for both loss of power due to inconnectivity . . . . . along with the producing
of an odor.

A BLUE markup is made on that area.

Without seeing a full wiring diagran . . . sort of looks like that transformer might be powered up 48 hrs a day.
How about the model number of this oven unit . . .the board is marked Robertshaw . . . but the real manufcturer of 10 other makers versons is probably Whirlpool / FSP corp with Sears / Kenmore as its current sugardaddy.

With that info maybe we can find a complete interconnect wiring diagram.

If there is continuity of the primary of the transformer and AC power coming in at N and L1 there looks to be two windings on the secondary at the other side of the transformer at A B C D that should then show lowered AC voltagepresence.


FOIL SIDE LAYOUT :

Stove board II.png


73s de Edd.
 
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wuoshi1031

Feb 23, 2017
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Sir wuoshi1031 . . . . . . . .


I have yet to see that backside / foil side of that board.
Your L1 and L2 AC line hot connectors look a bit darkened close to the board proper.
On the foil side of the board, you might find some high current carrying connection that has cratered out and is having some arcing connection developed at the FAN /or/ BAKE /or /BROIL relays.
That could then account for both loss of power due to inconnectivity . . . . . along with the producing
of an odor.

A BLUE markup is made on that area.

Without seeing a full wiring diagran . . . sort of looks like that transformer might be powered up 48 hrs a day.
How about the model number of this oven unit . . .the board is marked Robertshaw . . . but the real manufcturer of 10 other makers versons is probably Whirlpool / FSP corp with Sears / Kenmore as its current sugardaddy.

With that info maybe we can find a complete interconnect wiring diagram.

If there is continuity of the primary of the transformer and AC power coming in at N and L1 there looks to be two windings on the secondary at the other side of the transformer at A B C D that should then show lowered AC voltagepresence.


FOIL SIDE LAYOUT :

View attachment 32219


73s de Edd.

73s de Edd,

please see the foil side picture attached. There is no power on the secondar side, it is supposedly going into the Clock control board, which has no power and does not light up. I've found and uploaded the wiring diagram as well.

This is a Kennmore electric oven made in the 90s
model number should be 629.46776


unnamed (3).jpg s-l1600.jpg View attachment 32249
 

73's de Edd

Aug 21, 2015
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Sir wuoshi1031 . . . . . . . .


Consulting your wiring diagram for the oven portion . . . indeed one 120 V leg of the AC power . . . L1 and N . . . . . is fed to the power transformer .

Pull the crowfoot AC power plug and ohmically test the GREEN arrow path for about 15-20 ohms for the primary of the power transformer from TOP corners L1 and N power input.

If that then confirms, a powering up and reading of the 1-2 3-4 terminals of the secondary should confirm reduced AC voltage there.

AC POWER PATH RELATED TO POWER TRANSFORMER PRIMARY WINDING


tzIxpCc.png


http://i.imgur.com/tzIxpCc.png

73s de Edd

.
 

wuoshi1031

Feb 23, 2017
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Sir wuoshi1031 . . . . . . . .


Consulting your wiring diagram for the oven portion . . . indeed one 120 V leg of the AC power . . . L1 and N . . . . . is fed to the power transformer .

Pull the crowfoot AC power plug and ohmically test the GREEN arrow path for about 15-20 ohms for the primary of the power transformer from TOP corners L1 and N power input.

If that then confirms, a powering up and reading of the 1-2 3-4 terminals of the secondary should confirm reduced AC voltage there.

AC POWER PATH RELATED TO POWER TRANSFORMER PRIMARY WINDING


tzIxpCc.png


http://i.imgur.com/tzIxpCc.png

73s de Edd

.
when i power it up, there is no ac voltage on the secondary side. do you suppose the transformer is bad here or the board?
if the transformer is bad, what is the best way to find a replacement? The relay board along goes for 70-90 dollars.
Is there any alternative where I can replace the transformer along?
 

73's de Edd

Aug 21, 2015
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Sir wuoshi103 . . . . . . . .

Very important . . . .

DId you ever do a no power applied test and confirm that there was ~ 15 - 20 0hms of resistance between the
transformers primary winding , which I drew in on the Post # 9 reference drawing,. and if so, you should also read it again when testing right across the two nearby N and L1 terminals of the PCB..

PLUS . . . . . if you leave one ohmmeter lead at the mentioned L1 terminal and probe to the three blades of the unplugged AC power crowfoot connector, you should read almost zero ohms to ONE of its blades and that 15-20 ohms to another blade.

Then, as a DOUBLE test, move the ohmmeter wire to the N PCB connector and use the other ohmmeter probe to test to the three blades of the power crowfoot connector again and expect a like confirmation, but with the zero and 15-20 ohm readings of the blades being reversed.
If you never read that transformers primary resistance presence, either it is open or you erred in the reading of the almost zero resistance of the transformer winding areas internal thermal fuse.

RE-REFERENCING :
http://i.imgur.com/tzIxpCc.png

If you never find that 15-20 ohm primary winding, refer to my Post 3 drawing where the RED referencing lines ends actually end at the points where the primary wires are wound around and soldered onto those specific larger gauge wire terminals.
Do a direct ohms probe at them as a final confirmation..


73s de Edd
 
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wuoshi1031

Feb 23, 2017
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73s de Edd,

i
Sir wuoshi103 . . . . . . . .

Very important . . . .

DId you ever do a no power applied test and confirm that there was ~ 15 - 20 0hms of resistance between the
transformers primary winding , which I drew in on the Post # 9 reference drawing,. and if so, you should also read it again when testing right across the two nearby N and L1 terminals of the PCB..

PLUS . . . . . if you leave one ohmmeter lead at the mentioned L1 terminal and probe to the three blades of the unplugged AC power crowfoot connector, you should read almost zero ohms to ONE of its blades and that 15-20 ohms to another blade.

Then, as a DOUBLE test, move the ohmmeter wire to the N PCB connector and use the other ohmmeter probe to test to the three blades of the power crowfoot connector again and expect a like confirmation, but with the zero and 15-20 ohm readings of the blades being reversed.
If you never read that transformers primary resistance presence, either it is open or you erred in the reading of the almost zero resistance of the transformer winding areas internal thermal fuse.

RE-REFERENCING :
http://i.imgur.com/tzIxpCc.png

If you never find that 15-20 ohm primary winding, refer to my Post 3 drawing where the RED referencing lines ends actually end at the points where the primary wires are wound around and soldered onto those specific larger gauge wire terminals.
Do a direct ohms probe at them as a final confirmation..


73s de Edd

sir 73s de Edd,

so I initially did the testing with the transformer unsoldered from the pcb board and just testing the Crowfoot leg hooked to L1 (crowfoot leg1) against the N leg (crowfoot leg3), the reading I got was 1 or infinite.

After reading your post, i soldered the transformer back to the pcb and tested all the connection you mentioned. please see below What does this mean?

Thank you so much for your help, I am very new at electronic repair and something that I picked up as a hobby, really appreciate your patience and spend the time helping me troubleshoot.

L1 to N leg shows infinite ohm
N to primary crowfoot connector of transformer
1= 1
2=1
3=0.3
5=0.3
6=0.3
7==1

L1 to primary crowfoot connector
1=0.03
2=1
3=1
5=1
6=1
7=1
 
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73's de Edd

Aug 21, 2015
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Sir wuoshi103 . . . . . . . .

That testing that you just did confirmed that all is well from the AC crows foot, right up to the L1 and N connector that are right beside the Power Transformer.
Now you just need to concentrate on the few inches between the L1 and N blade connector and the Transformer.
Until that 15-20 ohms show up, we have no transformer primary.
Refer again to the close up of the transformer just below.

8qcKl1s.png


The L1 connector blade travels directly over to the #1 terminal of the transformer
That has AC power into ONE end of the transformers primary winding.

The N connector blade travels directly over to the #3 terminal of the transformer
and that goes inside and into one end lead of the one shot internal thermal fuse, with the other lead of the fuse routed to the #6 terminal of the transformer.
There is a foil jumper which connects term #6 over to terminal #5 and that #5 is the
connection point of the OTHER wire of the primary of the transformer.
Ohmming out from term 3 to 6 should reveal a very low/shorted reading, if the thermal fuse is GOOD.
NOW ohmming out from terminal #1 to #5 should reveal the 15-20 ohms of the transformer primary.

IF not . . . heat up ye olde soldering iron and concentrate on heating up the wire terminals where my RED lines mark ups end at #1 and #5 and pushing the melting solder into the cavity with the stiff solder . . . . let warm up for an extra 5 seconds for reflow bonding.
Hoping to get an internal solder blob as large as the one seen on terminal 6.

I will wait until you find out if that last solder warm up and reflow reconnected a degraded / poor wire to wire solder connection, if not, there is one final attempt / procedure.

73s de Edd

 
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wuoshi1031

Feb 23, 2017
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Sir wuoshi103 . . . . . . . .

That testing that you just did confirmed that all is well from the AC crows foot, right up to the L1 and N connector that are right beside the Power Transformer.
Now you just need to concentrate on the few inches between the L1 and N blade connector and the Transformer.
Until that 15-20 ohms show up, we have no transformer primary.
Refer again to the close up of the transformer just below.

8qcKl1s.png


The L1 connector blade travels directly over to the #1 terminal of the transformer
That has AC power into ONE end of the transformers primary winding.

The N connector blade travels directly over to the #3 terminal of the transformer
and that goes inside and into one end lead of the one shot internal thermal fuse, with the other lead of the fuse routed to the #6 terminal of the transformer.
There is a foil jumper which connects term #6 over to terminal #5 and that #5 is the
connection point of the OTHER wire of the primary of the transformer.
Ohmming out from term 3 to 6 should reveal a very low/shorted reading, if the thermal fuse is GOOD.
NOW ohmming out from terminal #1 to #5 should reveal the 15-20 ohms of the transformer primary.

IF not . . . heat up ye olde soldering iron and concentrate on heating up the wire terminals where my RED lines mark ups end at #1 and #5 and pushing the melting solder into the cavity with the stiff solder . . . . let warm up for an extra 5 seconds for reflow bonding.
Hoping to get an internal solder blob as large as the one seen on terminal 6.

I will wait until you find out if that last solder warm up and reflow reconnected a degraded / poor wire to wire solder connection, if not, there is one final attempt / procedure.

73s de Edd
Sir 73s de Edd,

Thank you! you are right on the dot. it was the primary leg 1, the winding originally attached to it had came loose or broke/burned off (likely due to overheat, my mom must have accidentally left the oven on when she visited me two weeks ago, no wonder my house felt so warm that week).

I used a blob of solder to make a connection to the primary leg 1 to the winding. After i've done that I could measure 0.16 ohn between N and L1 and primary leg 1 and leg5. Plug everything back in and turn on the power. the clock is back up and oven is working again.

I'll run through a few bake sessions to make everything is functioning properly but thank so much for walking me through all the steps, it was very very helpful.
 

RCA918

Mar 1, 2017
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Sir 73s de Edd,

Thank you! you are right on the dot. it was the primary leg 1, the winding originally attached to it had came loose or broke/burned off (likely due to overheat, my mom must have accidentally left the oven on when she visited me two weeks ago, no wonder my house felt so warm that week).

I used a blob of solder to make a connection to the primary leg 1 to the winding. After i've done that I could measure 0.16 ohn between N and L1 and primary leg 1 and leg5. Plug everything back in and turn on the power. the clock is back up and oven is working again.

I'll run through a few bake sessions to make everything is functioning properly but thank so much for walking me through all the steps, it was very very helpful.

Hi I am having same issue with my Sharp Microwave R8380 control unit pcb mounted transformer. I have pictures if can help the exact type i need to replace. I got this link to the schematic but its too blurry to read out https://www.manualslib.com/manual/1054910/Sharp-R-8380.html?page=39#manual
The only detail I have at the back of the oven is 240V 50 Hz 1.6 kW, Input current 6.7A, Output Power 650 W, Frequency 2450 MHz, Convection Heater 1.5kW.

Hope some one can direct which transformer to replace with.

Thanks
 

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