Multimeter YFE YF-3503 with burn out resistors R20, R21 and R22. Know values?

[BalPD]

Hello everybody,

This is my first post, but enjoying the forum for a long time. Hope all goes well.

I've bought a broken DMM YFE YF-3503 in a second hand market planning to repair it. I knew it was broken. The LCD shows digits but not measures.
After I opened it I saw some PCB traces burned out in the rotative knob and also 3 resistors burned out R20, R21, R22 near A/DC converter pin 1 (check photo).
After checking the other components I found out that npn C1959 transistor (next to VR1) was also defective. I also changed the A/DC converter ES5106 (similar to a ICL7106).
My last step is to fix the three burn out resistors. I can't see their values, only part of them. I know that R20 and R21 are 1% resistors (R22 5%) and that R20 digits start with 9 (white) and R21 with 4 (yellow) and 0 (black). R21 goes connected to VR1 (200ohms) so it must be 400ohms or near that.

Could it be possible you have the same multimeter and check their real values? I would appreciate it a lot

Thanks in advance.

balpd

[retiredcaps]

Some of the lower cost meter designs just follow the application datasheet examples for values.  See

pdf.datasheetcatalog.com/datasheet/CyrustekCo/mXrvszy.pdf

[BalPD]

Thanks for reply retiredcaps,

I've seen the ES5106 datasheet and ICL7106 also, and I found information about how it works but no about values.
I've also seen "based on ICL7106" schematics in Google Images and some of them are a bit similar but with different values.
I guess that resistor values are critical for correct performance as two of them are 1% tolerance.

Thanks

balpd

[Juanfrank7001]

Excuse my bad english.  Looking for information on this multimeter, I found your publication.  And I have that multimeter, and I'll send you a photo of the resistors.  I also ask for help.  I want to know how the multimeter selector contacts are going, the last photo helps.

[BalPD]

Hello JuanFrank!,

Thanks very much for the photo with the resistors. It's very useful for me.

Sorry but I can't help you with the selector contacts. In my multimeter they have disappeared (blown) because the
former owner used the wrong scale. Some of the PCB tracks in the selector have also disappeared.

Good luck

Thanks

balpd

[m k]

Mine is eating batteries like a mad multimeter.

[BalPD]

Thank you very much m k! You are very kind! Now I can follow the tracks.

Please Could you take a photo of the selector wheel springs position? it would be very useful for JuanFrank and me.

Thanks in advance.

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balpd

[m k]

Missing two are just like present four in the earlier picture.
The supporting plastic is in the middle.

There are 12 rings and 6 contacts.
You can match missing ones to rings without contacts.

[BalPD]

Many thanks m k you've saved my day and my YFE-3503 multimeter! With all this info I can surely rebuild the multimeter.

Hauska tavata

Kiitos

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balpd