Hi All,
I have two Powerbook 160s where nothing seemed to be coming on to the screen. I have recapped the screen and invertor board with like for likes.
Both of them are now working, but I'm getting the kind of interference I would expect of a failing/failed screen.
I've documented as much as I can on this thread over at 68kmla ([url]https://68kmla.org/bb/index.php?threads/powerbook-160-bleached-no-contrast-screen.40029/[/url]).
I'm out of ideas and do with some help diagnosing.
I have:
- Checked with ESR...
Spode
Member
Last Activity: 02-06-2022, 01:48 PM
Joined: 12-19-2010
Location:
-
Apple PowerBook 160 interference/ghosting
-
Re: Replaced Caps and made things worse...
Tried replacing C8 and some other 680uf caps nearby but with no change.
I think removing the caps from their extensions might help - but there is just no room on the PCB!
I'm at the stage of thinking, can I find a generic 24V PSU to whip in there. I know the pinouts for the connections, so it shouldn't be too hard to wire together. -
Re: Replaced Caps and made things worse...
Hi rherber1 - thanks for your response.
Yeah, it's a Baier LCD - 26" I think though.
If I went around changing every single cap - it would cost a fortune. I've already got a perfectly good TV - I just want to learn more and I like repairing things, so blindly replacing everything doesn't really fulfil that!
I think an ESR meter would be a good idea (would this one do the task? [url]http://www.maplin.co.uk/atlas-esr-equivalent-series-resistance-meter-43095[/url])
Part of the problem...Leave a comment:
-
Re: Is this noise power cycle, or shorting?
I just plugged it all back in, and it made odd clicking noises, which sped up and eventually just became a hum - and it powered on as it was before I started working on it.
Worked for 5-10 minutes and then eventually the same issue occurred.
So now I'm pretty sure that I haven't made the issue worse - so the startup issue is probably related to a bad cap somewhere. So which area should I start replacing first? What is the most likely culprit?Leave a comment:
-
Re: Is this noise power cycle, or shorting?
The black-gold cap was put in by me, to replace a swollen green one. Didn't make a difference though.
I think you're right mbates14 - it could well be a mistake I've made, but I've looked and looked and can't see anything
Before I started soldering, using a straw one of the red caps was making a noise. Now, the clicking is coming almost entirely from that same red cap. Could the cap have gone - or is it just an indication of something further down the line?Leave a comment:
-
Re: Is this noise power cycle, or shorting?
That's understandable - there wasn't a way for me to attach an MP3 though!
Here it is on SoundCloud:
[url]http://soundcloud.com/spode-1/recording-20110210-184854[/url]
Here are a few more pictures, from the SLR too to see if these help. Will check the standby voltages later. I found 1.2, 3.3, 5 and 24 when it was up and running.Re: Is this noise power cycle, or sh...an MP3 though!...Leave a comment:
-
Re: Is this noise power cycle, or shorting?
1) Medion 20099-S 32"
2) Did you listen to the MP3 I attached? I was wondering about the start-up cap, but it was working fine before I decided to re-solder the joints - so that didn't make sense?
3) Attached something a little better. I really should dust off my SLR for these things......Leave a comment:
-
Is this noise power cycle, or shorting?
Hi Guys,
Trying to fix another TV (now have a small pile of them that I'm struggling with).
The unit was turning on, and after a short amount of time, the backlights would stay on but the signal to the unit would just stop and then slowly fade away off screen (logic board issue?).
I found a swollen cap in the PSU which I replaced - on the 24V side of things. Made no difference.
The PSU was making a bit of noise in the top right, which using a straw I found to be one of the large red ceramic capacitors. I decided that perhaps the power... -
Re: Replaced Caps and made things worse...
Right, I've managed to isolate the noisy component - a transformer labelled "BCK-19-0294".
I'm struggling a little on how to test this properly. On the back, I can see 5 pins on one side and 4 on the other - it appears to be a pair in and a pair out.
Resistance from left to right with my DMM set to 2000k, trying various combinations is around 1200-1500. Comparatively, the same technique on other transformers shows very little resistance.
Would I be correct in thinking that this transformer...Leave a comment:
-
Re: Replaced Caps and made things worse...
Well I can hear the noise is coming from the inverter side of the board. So I guess I could try and replace them all on that side of the board as a start. I need to try the drinking straw method, if I can find one.
Hoping to find some time today to have a fiddle and see what I come up with....Leave a comment:
-
Re: Replaced Caps and made things worse...
No, I've not replaced 100% all of them. There's a few small ones around. But I can't help but think that the noise I'm hearing is part of the problem - or at least, a clue as to what is going on.
I attached them to wires because there is a solid heatsink over the top of where the caps should be - it's pretty tricky to get in there, and this way I could be certain I had a decent joint. I didn't think it would cause an issue?
Behemot - sounds like I need to a) learn how to test components and b) test some components...Leave a comment:
-
Re: Replaced Caps and made things worse...
Sorry to bump - but I'm at a loss as to what to try next! I'm trying to learn this methodology here - rather than just a one off fix...Leave a comment:
-
Re: Replaced Caps and made things worse...
I've now resoldered every transformer and toroid coil on the board.
I measured voltages across the 400v cap (300V) and the 35V caps (25V).
I found points on the PSU that should give out 12V and 24V. I get 11V and 26V respectively, even under load, which seem a little off tolerance - no?
I switch on the power, I hear a whine/squeal and after a few seconds I hear the audio on noise, and see the inverters switch on for a second.
I found the on/off pins for the inverter and wired...Leave a comment:
-
Re: Replaced Caps and made things worse...
I have replaced that cap - I don't think it would be dry. The noise appears to be coming from the side of the board that powers the inverters - potentially the transformer or MOSFET. I will take a drinking straw to it later.Leave a comment:
-
Re: Replaced Caps and made things worse...
Okay - my low ESR caps arrived today. I soldered them in and it made no difference.
There is still a noticeable high pitched squeel coming from the PSU that concerns me.
Is it possible that the main 450V cap is gone too? I can't see any swelling on it.Leave a comment:
-
Re: VW42LHDTV10A sound but, no picture
Even without the inverters working - you should still be able to see a picture on the screen using a flash light. If there is nothing, it's a sign that there is a problem further down the line, and doesn't rule out that the inverter could be damaged too.Leave a comment:
-
Re: How not to build a PC
I'm sure I remember a particular memory manufacturer stress testing their memory in an oven at extreme temperatures before shipping them out, to make sure that the overclocking was stable.
And no, a Prescott CPU never deserves sympathy
Leave a comment:
-
Re: 7300GS Loose Resistors - Help!
I've had resistors fall of cards before with no ill effect.
A striped wallpaper is usually indicative of bad memory on the board. Whether that is caused by the resisters being out of place is another question
Leave a comment:
-
Running Quad Output Inverter in Parallel for One output?
I have a TV that uses 2 higher power lamps using a slave/master unit that has stopped working. I have some sacrificial inverters from a TV that uses multiple lamps per inverter.
Could I wire 4 outputs from one inverter to power a single lamp with the power it requires, or would this cause issues with the IC chip? -
Re: Replaced Caps and made things worse...
I found a few things I wanted in the end (a heat gun, some more flux) and ended up spending £30 :P
I'll check RS next time. I was pretty tied and relying on Google Shopping for results, I'll admit....Leave a comment:
No activity results to display
Leave a comment: