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Old 11-13-2020, 10:59 AM   #21
stj
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Default Re: Dead Oven Control Board, Possibly Transformer?

search ali for 169' thermal fuses - if your too specific the seach falls over
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Old 11-13-2020, 11:46 AM   #22
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Default Re: Dead Oven Control Board, Possibly Transformer?

Here is a link that has 150*c

https://a.aliexpress.com/_mtc5gC5
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These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

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Old 11-21-2020, 11:46 AM   #23
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Default Re: Dead Oven Control Board, Possibly Transformer?

So neither of the manufacturers have responded. Applianceboardrepair.com responded, but were of no help, only sending me links to irrelevant search results on mouser. Their last response was that they did not have a transformer, but if I sent the board in they would "patch it" for me. Not sure what they would "patch" it with considering the useless search results they sent me. Oh well.

Anyway, I couldn't find an exact match for the fuse and didn't want to wait on AliExpress, so I ended up buying some 2.5A 126C fuses from Amazon for $10. I figured the amp rating was more important than the temp limit. Fingers crossed.
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Old 11-21-2020, 11:52 AM   #24
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Default Re: Dead Oven Control Board, Possibly Transformer?

I hope you got fast acting fuse not time delay fuses they are very different

The amp rating is more important but also weather or not it is fast acting or a time delay type of fuse

Last edited by sam_sam_sam; 11-21-2020 at 11:55 AM..
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Old 11-21-2020, 01:25 PM   #25
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Default Re: Dead Oven Control Board, Possibly Transformer?

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Originally Posted by sam_sam_sam View Post
I hope you got fast acting fuse not time delay fuses they are very different

The amp rating is more important but also weather or not it is fast acting or a time delay type of fuse
It doesn't say either

https://smile.amazon.com/gp/product/...?ie=UTF8&psc=1
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Old 11-21-2020, 02:47 PM   #26
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Default Re: Dead Oven Control Board, Possibly Transformer?

I drew a partial schematic and it all makes much more sense.

This Frigidaire Oven Controller 318010700 oven control board transformer is a custom part, because the vacuum fluorescent display needs that additional winding - the filament winding.

I would say estimate it is around 14VAC center-tapped as the board uses less common 9VDC relays. OP measures 18VAC but at no (relay) load, and 4VAC with the VFD connected?
In a pinch I would use an off the shelf 14VCT transformer and a second (extra) transformer 6.3V and add two resistors to get the filament voltage down to what it should be.

It's great the transformer survived. I read another forum that this is a common failure mode - any power line surge causes these oven boards to collapse and then cook the transformer. I'm still puzzled about what causes the transformer to overheat. There is an additional primary fuse F1 so I would expect that have protected the transformer but the design fails here F1 should only be around 1/2A max. it must be way over that.

I would say if you can't get a replacement thermal fuse, it is acceptable to add a (proper) normal fuse on the transformer's primary for F1. I use around 1/4A to 1/2A slow blow.

Last edited by redwire; 11-21-2020 at 02:49 PM..
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Old 11-21-2020, 04:02 PM   #27
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Default Re: Dead Oven Control Board, Possibly Transformer?

Quote:
Originally Posted by Bobby78 View Post
I did not realize that you were buying thermo fuses that will work it just will not let the transformer to get as hot before it cuts out the power to the transformer which is probably a good thing
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Old 11-21-2020, 04:21 PM   #28
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Default Re: Dead Oven Control Board, Possibly Transformer?

dont forget those fuses can easily be damaged when soldering .
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Old 11-22-2020, 07:57 AM   #29
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Default Re: Dead Oven Control Board, Possibly Transformer?

Quote:
Originally Posted by redwire View Post
I drew a partial schematic and it all makes much more sense.

This Frigidaire Oven Controller 318010700 oven control board transformer is a custom part, because the vacuum fluorescent display needs that additional winding - the filament winding.

I would say estimate it is around 14VAC center-tapped as the board uses less common 9VDC relays. OP measures 18VAC but at no (relay) load, and 4VAC with the VFD connected?
In a pinch I would use an off the shelf 14VCT transformer and a second (extra) transformer 6.3V and add two resistors to get the filament voltage down to what it should be.

It's great the transformer survived. I read another forum that this is a common failure mode - any power line surge causes these oven boards to collapse and then cook the transformer. I'm still puzzled about what causes the transformer to overheat. There is an additional primary fuse F1 so I would expect that have protected the transformer but the design fails here F1 should only be around 1/2A max. it must be way over that.

I would say if you can't get a replacement thermal fuse, it is acceptable to add a (proper) normal fuse on the transformer's primary for F1. I use around 1/4A to 1/2A slow blow.
Nice, thanks for the analysis. If I continue to have issues with the thermal fuse, I will consider replacing F1 with a 0.25-0.5A slow-blow fuse and see if that spares the thermal fuse. Hopefully I won't have to rig up a two transformer system.
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