Help! LCD Repair - Repairing a Homedics Digital Bathroom Scale

[jburger]

Hi ladies and gentlemen,

I was wondering if any of you could help me with a repair on an electronic bathroom scale. The brand is Homedics and the model number is SC-476. It is no longer under warranty, so that's not an option, unfortunately.

I tripped and fell walking into the bathroom, right on the scale, causing the LCD display to break. See the pictures attached.

I wanted to know (1) if this scale is repairable first, like a new ribbon cable/LCD kind of thing, and (2) where I can find such a ribbon cable/LCD display online for this scale. The only problem with it is that I can't read the display given the "blob" of ink over the numbers. It is still operational otherwise and feels like a waste to throw out if it can be fixed.

I have done repairs of Nintendo DS lite touch screens back in the day, so I have some experience with this kind of work. But for a bathroom scale? Where do I begin finding the right parts? I doubt the company would supply them or carry them.

Any guidance would be sincerely appreciated. Thanks so much!

Regards,

jburger

 

[KeepItSimpleStupid]

very likely the LCD is custom: The scale is available here: http://www.bedbathandbeyond.com/store/product/homedics-reg-grey-stone-digital-bath-scale/1045537417

What has been done for LCD instrumentation is to use a microcomputer and "read" the digits by their scan code and drive a generic LCD/LED display using that method like this **broken link removed** guy did for the 8050A. I don't think it's practical in your case.

Displays that I have replaced in meters used a Zebra connector. Google it.

 

[jburger]

Hi KISS,

Thank you so much for taking the time to respond. I looked over the link you sent about restoration of a Fluke 8050A multimeter display. That is awesome!

At this time, I'd have to say it is beyond my skill set/scope to do the work listed, as I am unfamiliar with the process and would need someone to show me in person the step by step process. I've always wanted to learn about microelectronics circuit analysis and design to repair old game systems where the LCD/LED screens go bad, etc. Got a Sega Game Gear that needs this service performed, as the screen is black, and it has been sitting in a cold basement for 15 years...but that's for next time...

Anyway, I did have one more important question if you or anyone viewing might have the time and knowledge to answer it, but on a different topic. It is about an air conditioning outdoor Goodman brand heat pump unit/HVAC condenser, model # GSH130301BA. In this outdoor unit is a single pole style contactor, model # CONT1P025024V, installed by the manufacturer (Goodman) that has failed three days ago, and now there is no heat or air in the house.

Hopefully I can ask in this thread, or should I start a new thread? (The closest category I see is automotive, but this isn't an automotive question, but rather home/outdoor electrical.)

My question is this: The single pole contactor has a metal "shunt" running along the left hand side, which is always connected with 120V. On the right side is a single set of contacts that "pulls in" when it gets a 24V signal for cooling or heating from the indoor thermostat. Then the right side sends 120V to the compressor and the rest of the system, but ONLY after first receiving a call for hearing or cooling.

Goodman updated their parts list and now only sells and recommends a double pole contactor for this unit, item # CONT2P025024VS shown in the photos attached. The double pole contactor has two sets of contacts.

From my research, someone on an old forum (in 2003?) said that to approximate the "shunt" side of a one pole contactor--which is always on--on a two pole contactor, one could just run an AWG #6 jumper wire from Line to Load on one leg, effectively making the contactor single pole.

My questions: (1) can you confirm if AWG #6 wire the proper gauge wire to use as a jumper, and what type--solid copper or stranded?; and (2) where on the left side of the 2 pole contactor would I wire it? Do I start at the bottom left lug, tightening both the live 120V black wire and the #6 jumper wire together, and then wire it to one of the top screws? Or do I wire it to one of the upper four groups of terminals with a female spade connector? Or do I wire it around bottom left screw to upper left screw? Or run the wire from one probe on the bottom group of four terminals to one of the probes on top?

In summary, a "Keep it Simple Stupid" () version as per your namesake: what is the correct jumper wiring that would bypass the contacts on the left side? I would really appreciate if you could draw a colored line in MS Paint or a graphics editing program to show where the wires should go if possible. The left side should always be on, and the switch bypassed. I hope what I am asking is clear to understand. Please see pictures attached.

Thank you so much. No one else I've asked seems to know the answer or they want megabucks that I don't have to come out and install the part... AND they want an extra $165 just to come out and "diagnose," which I've basically already done.
Contractors and contactors.....

Cheers!

 

[cowboybob]

A new thread might have been better, but while we're at it...

This is how I'd do it (BTW, AWG #6 wire is total overkill):

Make sure to wrap the bare portion of the UPPER 12g jumper wire, clockwise, around at least 2/3 of the TOP connector screw before tightening. Be careful not to over-tighten (it's fairly easy to strip the hold-down screw). Snug the BOTTOM jumper wire into the lower lug with the other main feed wire.

Arrange the jumper wire as needed to accommodate the other wires in that area.

 

[jburger]

Hi cowboybob,

Much obliged!

Thank you so much for your help, the precautions, and your excellent diagram.

Could you link me to a site that sells the AWG #12 you suggest in insulated solid copper (any color is fine), but maybe only a small amount, like 1 or 2 feet? Everybody looks to sell like a minimum of 50 feet, and there are so many selections of AWG #12 with different insulation materials, temperature ratings, acronyms I am unfamiliar with (e.g., THHN, THWN-2) etc. that is confusing for me.

I just want to make sure I am buying the correct wire. Never bought wire from Home Depot or Lowe's before; perhaps they sell by-the-foot?

Thanks again so much!

Regards,

jburger

 

[jpanhalt]

Don't know where you are, but #12 AWG is quite common in household wiring. Home Depot or any hardware store should have it. You might even find what you need in a trash bin at a construction site -- standard 3-wire household wire has it.

 

[cowboybob]

What jpanhalt said.

Although a local hardware store (Ace, TrueValue) is more likely to sell you a short (1-2 ft) piece.

You should be able to find a dealer who sells single wire lenghts (generally on a spool).

 

[jpanhalt]

Hey, you need to be a beggar like me. I am not above going to HD and asking for scraps. Of course, being an old phart helps. But, I have had great success, particularly if I buy something else like their 55 gallon clear yard bags. BTW, used 55 gallon poly containers (food industry for canola oils and such) for about $10 or so are the best bargain in the US for trash. Just use your scroll saw to cut the top off. Two colors are available. In my area -- blue and white. I prefer white.

 

[KeepItSimpleStupid]

The OP/TS apparently posted more info on another forum: https://www.applianceblog.com/mainf...1BA-Contactor-Capacitor-Replacement-Questions

I'm not comfortable answering this question until, at least, I knew what region of the world the OP/TS resides. In the US, it would be proper to switch both legs of the 208/240, so I have to wonder if that was Goodman's intent with the replacement?

If there is a capacitor associated with the fan motor/compressor (they are usually mult-part), it's probably a "better bet" as the failed component. You can usually examine th contacts with the outdoor disconnect pulled AND you can usually push the relay bar manually to see if there may be something else causing problems.

At 6-10 years, the capacitor(s) [multiple sections in the same case] would warrent replacement.

I think it may be a heat-pump, so there are other possible problems.

My $.02

 

[jburger]

@ jpanhalt - I do that with wood scraps and trim pieces at Home Depot sometimes--get them for free for miscellaneous projects around the house. Great minds think alike, lol! Though I haven't ever seen these poly barrels you mention.

I will look to pick up this wire soon. I am stuck in the house currently with no transportation, so I am thinking/half-joking about dismantling the toaster to get at some #12 wire... with bread crumbs...

@ KISS - Looks like you tracked me down! Great investigative work, detective! You're secretly...... the Batman! Now go find Trump's tax returns...

So I am located in the US, Maryland specifically. And you are correct that this is a heat pump. On that other ApplianceBlog thread you linked, I posted a picture of the rotted/burned contactor pieces on top of the unit. Here it is, too:



The relay bar can't be pushed in, as it has broken off completely.

I think that is the only problem (the contactor rather than the capacitor), but I figured I would also buy a new capacitor while I was at it, and replace that as well, while the unit is apart. The capacitor is a dual run style and has three terminals on the top for the (F)an, (C)ommon, and (H)ermetic. Hermetic is for the compressor, fan goes to the fan motor?, C is Common. I think my old capacitor is still good, but it has weathered a little with the elements, and is worth replacing or at least having a spare nearby for thunderstorms. Interestingly, I tried testing the new capacitor with my multimeter, but the multimeter doesn't have a setting for microfarads, so nothing was being measured... I'll just have to check it with power on, and the disconnect plugged in.

What is the best way to discharge the capacitor currently in the unit? Some people use an insulated screwdriver and run it across the terminals, shorting them out that way, but I have heard about cases where the capacitor can explode by doing so. Yikes! So do I put the multimeter on AC, turn it to 600 Volts, and then just test the leads (Common to Fan, Common to Herm, Common to the cabinet screw/ground) with the power off to bleed them safely instead?

They say the "one plus" pole contactors are prized by the manufacturers for cost savings. From my research, I think the "always on" shunt side in a one plus pole helps power something called a crankcase heater, and it also keeps things hot/running/always on, as there is a chance that liquid freon/refrigerant could otherwise slog through the compressor in the cooler months. Not sure on the accuracy on that. Another guy I bought parts from said that "Goodman does not require the shunt side to be on all the time. With the double pole contactor, the shunt side would only be on when the contactor is energized and this is OK with Goodman either way." Maybe it's so Goodman can sell more units after consumers screw up their compressors with the new 2 pole contactors...

If you have the chance to look over it, might you or anyone else know about question #5 I asked on ApplianceBlog? Specifically, there are two loose yellow wires in my heat pump. I don't think they go to anything essential to run the unit, as they were clipped and tucked away. I think they might be clipped pressure switches of some kind.

Many thanks all around for all your help once again!

 

[KeepItSimpleStupid]

Your making me "work".

The minimum AWG feed is 12 AWG, BUT it depends on the "wire length" or 2x the "trip length", from the unit to the breaker box. IF the wiring was "recent", it would have a yellow outer jacket. To size the wire, you need < 3% drop in voltage and can't exceed 80% of the design capacity of the wire at FLA (Full Load Amps). Those burnt ends means something bad.

You really need an outside disconnect if you don't have one. The connection to the unit would be using Sealtite flexible conduit. An AC install kit would generally have all of that,
Don;t forget "drip legs". Those Romex connectors should not be used outdoors.

if you want, you can make your AC person really happy, by putting in a disconnect with a 120 V convienience outlet, It's a separate circuit, but it gives the guy a place to plug in his vacuum pump. e.g. **broken link removed**

There was a note about loose yellow wires on the schematic. I'm afraid your going to have to take a picture of "the other end" of the yellow wires.

What is the best way to discharge the capacitor currently in the unit? Some people use an insulated screwdriver and run it across the terminals, shorting them out that way, but I have heard about cases where the capacitor can explode by doing so. Yikes! So do I put the multimeter on AC, turn it to 600 Volts, and then just test the leads (Common to Fan, Common to Herm, Common to the cabinet screw/ground) with the power off to bleed them safely instead?

Not really a good practice. You can size a resistor for the full voltage power wise AND make R such that 5*R*C is a reasonable number of seconds. e.g. around 30s. So, hold for that amount of time.
e.g. 5 * R * 10e-6 >= 30 s; 10e-6 is 10 uF. use the bigger capacitance.

Play with the numbers. 1e6*10e-6*5 = 50 seconds. So about 98% of the voltage is discharged in 50 s
10 uF and 1 M resistor.

Or just measure the voltage across it before disconnecting.

 

[jpanhalt]

I find the "plastic barrels" on Craigslist -- sometimes called rain barrels. You want food grade, as they are easy to clean. In Cleveland area, don't pay more than $20 (shown below). That is at a dealer. Individuals will sell for less. His wholesale acquisition price is about $3.

Poly barrels I have seen all have a sealed top, but that cuts easily with a coarse blade in a scroll saw. The rims are quite thick and the saw tends to guide itself around the inner surface, which give a fairly smooth opening..

 

[GromTag]

Are those images of YOUR H/P? in the other forum? If so then I've seen a potentially bad wiring method I've encountered before, unless the wires have been altered by gauge and still go to their correct connections.

The H/P fan blowers N/C (normally closed) relay appears to have the 24V AC wire connected to the relay terminal and the 240V to the defrost boards 24V input! Or what appears to be so. The lower wire looks to be the 24Volt AC by the fan relay, Potter & Brumfield relay !

 

[GromTag]

Images, images speak louder than words as they bring us the words needed!

Thank you.

And also the thermostat looks to be damaged, then that is the HOT 240 volt wire going to the defrost board....

The images I refer to is the wiring at the heat pump. A scale photo of the whole board area as so to attempt and see where the wires are going.

 

[GromTag]

And flip the breaker to the H/P OFF, as this could be a fire hazard! as the 240V AC is cycling through the 24V side of the step down transformer is in fact that really is the 240 volt wire at the defrost board!

And the wires at the thermostat would be live higher than 24V AC!

That unit would have its own breaker at the main terminal near the households external meter in the case beneath the globe, should equate to 30 AMP or if was set up to handle more by installation it may be a double 30 AMP.

That breaker should be located there, and also deactivate the internal Furnace breakers to fully shut down the system in the breaker box indoors.

 

[GromTag]

If I could only see that defrost boards model number on the top to try and find some documentation of wiring diagram, the furnace is different, limiters and sequencers with the furnace blower relay and the step down transformer.

Looks to be PC (spider web)DBM130? I see it on the QR code.

All I could find of an adequate image of that defrost board with a short search..

C - Neutral
Y - 24V AC Cooling mode run from thermostat
O - 24V AC reversing valve connection, to only operate in cooling mode
O - 24V AC other reversing valve connection, a relay coil solenoid device with no polarity. Reversing valve is a 2 wire solenoid.
W2 - Heating mode, auxiliary heating tends to be tied into this if equipped.
R - Boards 24V AC power input.
R- Red wire to the 2 wire defrost bi-metal sensor.
DFT - red wire return from the 2 wire defrost sensor.

: EDITED : The H/P fan relay extends from the main relay,
Wire path connections, Breaker, main H/P relay, fan relay (Potter&Brumfield), onto blower fan. The capacitor has its own wire to the blower fan if memory serves correctly.

If that large wire again does determine to be 240V AC, then the reversing valve and the orange wire to the thermostat back lashed through the yellow wire, and shorted out. The unit may have extensive damage to the reversing valve if the voltage made transition through the connections.

However if that wire is not the 240V wire, then the other things such as the display on the thermostat and the yellow wires burnt and the incomplete circuit to the main H/P relay contacts that resulted in arcing the contact into destruction. No proper phase.

I have honestly forgot the phrase used to describe this event.

 

[GromTag]

Caught myself. that's the scale LCD damaged, not the thermostat, regardless, check the thermostat for damage! just to be sure.

 

[GromTag]

Closer review update.

Update : I've been going over the images on the other site and noticed that the H/V blower fan wire looks to being used for the reversing valve connected at the main relay (contactor) neutral side, and the other orange lead connected to the yellow lead, thermostats on terminal when in cooling mode only.

Their all bundled together with that lock tie making it an 50/50 thought process if that wire does link the 24V to 24V, or jump the 230V to the 24V AC side, I have done this before, the H/P would start up and run until it charcoaled a 1 Mega Ohm carbon resistor and fried the plating off of the Merrcury tilt within the glass tubes, night time, lights got up and walked off, and the home owners were quite the.... interesting group. Could have sworn that I saw an discovery channel crew hiding in the bushes no too far away...

And the defrost boards designated wire is being used for the blower fan, that wire is under rated for that use. A wire swap would be advised on that. I will append an image showing the two wires.

So that H/P is set up to only run in cooling mode?

Well, gaining on the way that it is wired, I'm going to make some assumptions if I may,

1. Is it only operational in cooling mode?

2. would the thermostat happen to be an older 2 wire only model?

3. Given the if indicators of the wire is leading from the contactor to the defrost boards O lead then to the reversing valve would be culprit to cause the contactor to burn up like that.
How? Well the reversing valve is either on or off, meaning in heat mode it is off, in cool mode it is on all the time during cooling mode, unusual yes but here is why, cheapness of design.

The Freon charge up when the pump is running is indicated on the H/P itself on that chart giving the ratings of the unit. (high pressure acceptance)

The line to the household becomes pressurised and a small valve that links a typical 4 smaller tubes to the larger line to the inner rail assembly acts as the high side/low side difference, in heating mode if the outside H/P were to operate with the reversing valve off, then the pressure would be on the opposite side of that valve (this is a basis of the function on the rails indoors above the furnace)

When the system has ran for a period in either mode and line pressure has risen, heating or cooling, then the reversing valve state suddenly changed, the pressure dump on the valve is monstrous to the valves operation resulting in a ball peen hammers strike equivalence of force to the valve itself resulting in damage give time, est typical 3-5 years avg for these to begin to show this issue, waiting for a minimum of at least 40 minutes for assurance that the line has depressurized to a safer lower level before switching modes would help extend the valves life for at least 8+ years. Leaving the mode alone per example in cooling mode and it's getting cold weather, adjust the thermostat to high temp range (floored) and then time, then after time elapses change to heating mode, the same goes for heating to cooling as well.

Your H/P tho is wired in a bad way, the reversing valve is switched on with the contactor by the same yellow lead wire and then when the H/P shuts down by the thermostat so does the reversing valve each time resulting in high pressure dumps against the valve.

With a faulty reversing valve, in cooling mode, the valve can begin to block the pumps Freon flow and result in a freeze up at the dryer rail and at the indoor rail causing the pump to produce a locked rotor effect that would explain the damage to the contactor and the neutral return for the up to 240 volt side or 230 rather, (I have all ways have jumped to 240 volt when explaining) thus the burning of the white wire, as for the yellow wires being burnt, the contactor became that hot!

If you did replace the contactor, then you would might observe the H/P in operation (Too cold weather all ready to observe this) would begin to produce ice on the dryer lines then the pump would eventually freeze resulting in yet another contactor replacement.

Also, it the H/P runs whilst in heating mode, (not sure of the wiring indoors at the furnace) then that would need to be stopped, because the H/P would be cooling whilst the furnace would be heating. If so disconnect the yellow wire to the outside H/P and the white wire from the furnace on the 24V AC side. this would disconnect the signal wires to the defrost board but not cut the power, that's either the red wire or what appears to be the teal wire.

Image below.

 

[GromTag]

Clarification on the images, the larger wire meant for the H/P blower fan. It is being currently used for the reversing valve and the smaller wire for the fan. They need to be swapped, either of the red dot wires that would reach would work for the defrost boards O connector to the contactors chosen neutral side. Then the fan wire from the topside contactors opposite from the Mains side connector to the relay on the defrost board.

 

[jburger]

Everyone, thanks for all your great help. I want for you to know it is super, super appreciated. I managed to get the outdoor unit running! I put in a new contactor and a new capacitor about three hours ago and have been diagramming from my notes in the time since to post in this thread.

@ cowboybob - I decided to go out and buy a one plus pole contactor after all with the metal shunt, so it is an exact part match without having to do the jumper wire. I have the two pole contactor also bought and will keep it and your wiring diagram with the #12 AWG notes printed out and handy in case I ever need to use it. Thanks again for your help and great diagram.

@ jpanhalt - If I ever see those blue and white food barrels when out and about, I will think of you!

@ KISS - There is an outside disconnect already installed, but it doesn't have those cool 120V convenience outlets. The resistor formula makes me wax nostalgic to my math school days (not! ). I don't have a large size resistor handy, but I was watching a troubleshooting video where the tech said there is one in the multimeter itself that should discharge things. Anyway, the long and short of it is that I lived.

@ GromTag - Thanks for all your excellent help. Your technical explanations are super appreciated, even if I don't understand all the mechanical specs about how heat pumps and the internals work. It may take me a few years to fully understand this stuff, seeing as how I am not at all experienced with HVAC and electrical engineering. Basically, I just know that this color wire should go here, that color wire should go there kind of stuff. But this is great education and I've probably read over your posts 50 times by now.

Here are answers to your questions:

1. Is it only operational in cooling mode?

No, it is both for cooling and for heating.

2. would the thermostat happen to be an older 2 wire only model?

It is a newer Honeywell programmable thermostat with a green LCD display and several colored wires when you pull it off the wall.

I found the wiring diagram for the outdoor unit on the inside of the panel cover (doh! can’t believe I missed it before). I scanned it and attached it here. Even though the job is completed (for now…), hopefully, the documentation and diagrams will be useful for others looking this up for some DIY help and advice. Goodman's factory wiring diagram from the inside of the service panel is below:



I finished late at night (it's now past midnight here), so I posted a 3 image composite of the capacitor, the contactor, and defrost board. (I know, I could've waited until morning to take a full scale shot, but didn't want to keep you waiting.) Note where I've circled in green "lower right box" and "circle hole" for the next diagram. Here is the composite image:




I also saw a YouTube video for the defrost board which also helped, located here:

It’s my understanding that all the terminals going horizontally across the defrost board (C, Y, O, O, W2, R, R, and DFT) are 24V low voltage, except for the two Potter and Brumfield's (black box relay’s) two terminals (DF1 and DF2), which both take 120V black wires.

I took a look at all the wires and where they go, and diagrammed them. I think the two questionable wires you pointed out are actually wired fine after all, but please correct me if I'm wrong. To check the wiring, I removed only the service panel, and didn't disassemble the whole outdoor unit further, so I will refer to two places on the diagram again as the "circle hole," which is the bundle of cords on the bottom left, and the "lower right box," which is the portion on the lower right that has a bunch of wires spliced together with wire nuts. DF1 goes to T2 on the contactor (120V). The second O wire goes to the "circle hole" in the bottom left.

Here is my drawing of the wire diagram as it is currently wired, with notes on the two wires you pointed out:



For the two loose yellow wires, I put electrical wire caps on them. Still not sure where exactly they are supposed to go to, but I think they may have been clipped by the service technician who installed the unit years ago. They don't look burnt, and were tucked away, so I guess they are not needed.

I wire stripped the burnt white 120V feed wire and also stripped the black 120V feed wire for a fresh copper connection going into the bottom L2 and L1 terminals. The white one was badly pitted.

Fingers crossed this holds up! Thanks again for saving my butt!