The colour code looks to me like Blue-Red-Black which would be 62 ohms, which is a standard value, but a black tolerance band is not normal.
Unless it's meant to be Blue-Red-Black-Black (620 Ohms) with no tolerance band (20%) which I believe is non-standard.
(A 20% resistor like that should be Blue-Red-Brown with no tolerance band)
When resistors burn the colour bands often change (get darker) although this resistor looks like it's just really dirty, rather than burned.
However, it may really be a 62 Ohm resistor that burnt up and is now 10x higher than it should...
Agent24
I see dead caps
Last Activity: 06-12-2025, 10:07 PM
Joined: 10-04-2007
Location: Hiding inside a plated-through hole
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You should not need to adjust anything significantly, so there is still something wrong, like a problem with the feedback circuitry. Maybe something else is open-circuit.
If you have found broken traces already there may be more. Also more components maybe damaged.
I've found resistors that looked okay but the terminal had rotted off underneath the paint. Ohm them all out.
Yes replace the capacitor you broke. It wouldn't be there for no reason.
Out of interest, what is the other IC that isn't the LM723?Leave a comment:
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+2
That's what I'd try too...Leave a comment:
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Can't you upgrade the silicon to handle the 110v requirements better? That could be an interesting project... maybe a FET with lower Rds(on) and higher current rated rectifiers, etc?Leave a comment:
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Maybe the zener is underrated, try replacing it with a higher wattage one, I guess?Leave a comment:
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I know this is an old thread but how do you determine the windings are shorted when at least one shows good on the ring test?
If any winding is shorted, it should affect all windings and none should have high rings, as far as I know.
Or is there a special case where this can happen? Would be interesting to know!Leave a comment:
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Definitely could be a bad chip then, I've seen where liquid like battery or capacitor electrolyte gets up into an IC and destroys it internally from corrosion etc.
I hope that there is no liquid that's soaked into the PCB substrate and is causing leakage between tracks etc. That is also a possibility depending on the liquid and the duration.Leave a comment:
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Now I re-read the datasheet it doesn't seem like the module has filter capacitors inbuilt.
The application circuit shows the smoothing and filtering circuit as external to the unit.
So, have you checked the filter components in your board?
Best if you can post a photo of the PCB where this module is used.Leave a comment:
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Great to hear!Leave a comment:
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If the original design was set to specifically 4.6v output then there must be a reason for that.
Going higher to 4.74v or even 5v is probably not a good idea. You may damage something or cause incorrect operation.
Either get the correct chip or change the resistors so you get 4.6v from a different chip.Leave a comment:
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If the output voltage is low it maybe has bad capacitors, since it's potted though, you could just tack some extra capacitors on the output and see if it works... very ghetto repair but might work...
(Or you can heat it up and soften the potting compound, remove that, and perhaps repair it properly)Leave a comment:
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You say it was left drenched in a beverage for over a year.
I would suspect there is still residue or corroded connections somewhere.
Run the whole board through an ultrasonic cleaner and hope it starts working...Leave a comment:
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Going by the colour (which seems to be black) I'm guessing an inductor or probably ferrite bead (or maybe an un-labelled resistor).
SMD ceramics are usually white or brown.
A ferrite or resistor will generally only blow up if something else is shorted, thus pulling too much current through it, however.Leave a comment:
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Love the deranged names of these caps. Nobby? LE Pet?
Ironic that the one called KYS was the only one that wasn't dead...Leave a comment:
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Ah, I'm glad then that my ZhongDi hot air and soldering station is an older model and uses a linear power supply.Leave a comment:
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By that reasoning though, the original 27uF caps would never have been +20% either.
So the circuit may well be unstable with something that much higher...Leave a comment:
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Louis Rossmann recommends Branson EC
[url]https://store.rossmanngroup.com/index.php/review/product/list/id/329/[/url]
I've never used it, seems to be a specifically formulated detergent
CapLeaker's suggestion is probably cheaperhttps://Louis Rossmann recommends Br...obably cheaperLouis Rossmann recommends Branson EC
[url]https://store.rossmanngroup.com/index.php/review/product/list/id/329/[/url]Leave a comment:
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Ah, but what if your 33uF capacitor is also +20%.......Leave a comment:
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Interesting project, why the external power supply at all, though? Battery power I can understand but don't these already have a PSU inbuilt?Leave a comment:
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That's are also cleaning fluids specifically formulated for the task.
Not sure IPA is a good idea because you'll get a lot of fumes.Leave a comment:
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