270uf reads 318uf

[ffury]

I pulled a 35V 270uf cap from an Inverter board and tested it with a capacitance meter. It reads 318uf. Is that within tolerance. When a cap goes bad does the reading on capacitance go high or low?

[PCBONEZ]

Re: 270uf reads 318uf

If it has an "M" on it the uF tolerance is +/-20%. [That's what most lytics are.]
uF usually goes down when they go bad.
.

[retiredcaps]

Re: 270uf reads 318uf

It reads 318uf. Is that within tolerance. When a cap goes bad does the reading on capacitance go high or low?

Most electrolytic caps are +/- 20% of their stated value.

270 x 1.20 = 324.

For all the bad caps that I have encountered, when caps go bad from a uF perspective, they are significantly lower. For example, a bad 270uF cap might read 35uF.

Caps can also be bad from an ESR perspective. They usually have higher ESR than their specification.

Aaarggh, didn't see PCBONEZ respond when I started to reply and he types faster than I do!

[jetadm123]

Re: 270uf reads 318uf

What brand is the cap? Some caps are pretty much replace on sight because of their poor reliability.

[severach]

Re: 270uf reads 318uf

On some caps the capacitance goes up when the capacitor starts to go bad. I've seen bulging but working caps up to 4x the printed value. This only lasts a short time before the capacitance plummets and the ESR skyrockets.

Brand is important. I've seen many Panasonic caps test a bit more than 10% high. I let them stay. If a bad brand is too high then out it goes.

[japlytic]

Re: 270uf reads 318uf

Electrolytic capacitors over a certain uF rating could be inaccurate for timing applications, unless they are low leakage; even then, tolerance can vary over its lifetime.

[ffury]

Re: 270uf reads 318uf

The caps in question are brand name Nichicon 35V 270uf (m). There are four of them mounted on a CPT 320WA01C Inverter for an Akai LCT3201AD LcdTv. The TV will take 3 minutes and 20 seconds to come on to the splash screen. This brand has a MLT169b power supply notorious for bad caps. I have replaced all the filter radial caps on the power supply and all the larger caps on the mainboard. The TV still has a 3 minute delayed start. I've moved on to checking the Inverter. I feel like this is a cap problem. My Mat Electronics ESR meter isnt the best but does work. I also have a capacitance meter. I'm looking for a bad cap thats bound to fail but just hasnt got there yet.
All comments are welcome.

[PCBONEZ]

Re: 270uf reads 318uf

1 - Nichicon are probably are not original in an Akai.
2 - Inverter doesn't sound like the problem because to does nothing to change the time when a splash screen is displayed or goes away. If back light was slow you would be past the splash screen when screen finally lights up.
3 - The Nichicons aren't a likely suspect plus seem to check good.

Most likely suspect is the caps in MLT169b or the larger ones on the mainboard.
Perhaps some previous recapper used the wrong sized caps and affected timings.
.

[ffury]

Re: 270uf reads 318uf

I am the original owner of the TV purchased new. The Caps are the originals.
Thank you for your comments. All comments are welcomed.

[PCBONEZ]

Re: 270uf reads 318uf

I didn't see a single Japanese cap in the one I did.
On the other hand I didn't look at the inverter that closely.

There are two things going on to see an image in a screen.
One makes the image.
The other lights the back-light so you can see the image.

Slow to get to the splash screen has to do with making the image.
The inverter has to do with the back light only and so isn't where the problem is.
[Hope that makes sense.]

Sounds like maybe something is slow to get up to voltage.
Perhaps a leaky [or partially shorted] or wrong value cap.

Did you use low ESR caps when you recapped the PSU?
The one I did was an MLT168x in a LCT2785TA so not the same but as I recall some of the caps had substantially low ESR.
GP caps aren't going to cut it and 'entry level' low ESR caps might not either.
.

[ffury]

Re: 270uf reads 318uf

Thank you for your input. You have made some very intersting observations. I will have to go back and look at the caps on the power supply and see if they are low ESR. I think you are right about the Inverter being OK.
I need to know more about the T-com board and what it does.

What is a T-Con board??????

[PCBONEZ]

Re: 270uf reads 318uf

T-Controller aka LCD Controller.
I dunno where the T cones from unless it's for TFT.

Converts the standard format video signal from the video processor for display on that specific panel.

Your problem would most likely be before that section.
- Meaning the main board where the various inputs are converted into that video signal in the video processor - or in the power to the main board board.

I say this because I don't see how the t-con could cause a delay.
It just converts in to out, like say a USB to PS2 converter.

All the 'thinking' goes on in the video processor on the main board.
That's where you could have a delay problem.

Your t-con looks like this.
.

[Th3_uN1Qu3]

Re: 270uf reads 318uf

T-Controller aka LCD Controller.
I dunno where the T cones from unless it's for TFT.

AFAIK it stands for Timing Controller.

[PCBONEZ]

Re: 270uf reads 318uf

AFAIK it stands for Timing Controller.

That makes sense.
It sequences the up-down with the right-left to reproduce the image.
.

[pudgi300]

Re: 270uf reads 318uf

Did anyone figure this problem out about the Akai 3:20 delay turning on. I have the same problem.Have changed all p/s caps and about sixty others on the main and channel memory board. Still can't figure it out. Kind of think it is firmware. Looking for file lct3201ad_v16.bin. All voltages are correct. The only one i am not sure of but think is ok is the power_on. It is 3.8v when tv is on and 0v when off. It goes right to 3.8v on turnon. TV in standby and turn it on and 3:20 later the screen comes on. It is right to the second.

[ben7]

Re: 270uf reads 318uf

Did anyone figure this problem out about the Akai 3:20 delay turning on. I have the same problem.Have changed all p/s caps and about sixty others on the main and channel memory board. Still can't figure it out. Kind of think it is firmware. Looking for file lct3201ad_v16.bin. All voltages are correct. The only one i am not sure of but think is ok is the power_on. It is 3.8v when tv is on and 0v when off. It goes right to 3.8v on turnon. TV in standby and turn it on and 3:20 later the screen comes on. It is right to the second.

Do the backlights come on immediately when the TV is turned on, or do they only turn on after the 3:20 delay? Is the audio OK or does it come on also when the image comes on?

[pudgi300]

Re: 270uf reads 318uf

The backlight only comes on after the 3:30 delay. There is no audio because it defaults to TV no signal. This means you have to switch it to a working input. All inputs work when selected. Channel memory board holds scanned channels but main 8202 chip defauls . Like air/cable defaults to air volume defaults to +30 and other setting to factory setup. Would like to have a chip with the v16 firmware but not much luck.

Thanks

[Th3_uN1Qu3]

Re: 270uf reads 318uf

Akai sets are now made by Vestel if i'm correct. Vestel are known for poor QC and weird bugs. I'm fairly sure you have a firmware issue there - the problem is, where to obtain a different one.

[pudgi300]

Re: 270uf reads 318uf

Th3 thanks for the reply. I will continue my search for some firmware and followup if i get any results.

[pudgi300]

Re: 270uf reads 318uf

When i to to menu and punch in 8202 and bring up the firmware screen it says the UI SYSTEM = DEMO Am i stuck in demo mode and how can i get out.

Thanks