ICE3B0365J Troubleshooting (W200 Sub)

[SFB]

Hello all.

I am currently trying to troubleshoot and repair a W200 Sub as a personal project/learning and it seems to have gone a bit beyond my circuit knowledge having exhausted most of the obvious testing (attached images blue=tested, yellow=replaced). A repair had been attempted by a family member prior and some of the tracers damaged so I had to repair them first.
The board is a 104-A05426B00V-E and is an ICE3B0365J chip, and after finding the chip datasheet have gotten the following readings;

1.SoftS - Unreadable (fluctuating)
2.FB - 473mV
3.CS - 0
4.Drain - 330V
5.Drain - 330V
6.n.c. - 110mV (fuctuating)
7.VCC - 15V (fluctuating)
8.GND - 0

I vaguely understand what each pin is for, but I'm not sure what values I should be expecting in order to trace where any extra voltage is being lost, or being gained. I am assuming the Feedback voltage is too low so it is cycling restart, but I might be misunderstanding the datasheet. The transformer secondary is not receiving any voltage at all which I assume is due to the VCC not being stable.

Any insight into this would be very much appreciated.

[stj]

Re: ICE3B0365J Troubleshooting (W200 Sub)

did you replace the small cap in the lower right corner near the chip?

[SFB]

Re: ICE3B0365J Troubleshooting (W200 Sub)

Yeah, I replaced the 15v electrolytic but the old one tested fine.

[SFB]

Re: ICE3B0365J Troubleshooting (W200 Sub)

Bump

[CapLeaker]

Re: ICE3B0365J Troubleshooting (W200 Sub)

Figure out why your VCC is fluctuating. VCC should be almost rock solid and have very little fluctuations. Maybe heat sections of the board up with wifeys hair dryer to 40-50C and see what’s happening.

[CapLeaker]

Re: ICE3B0365J Troubleshooting (W200 Sub)

Look at this: https://www.youtube.com/watch?v=Ym1dvujBtns
Looks very similar to your PSU?

[SFB]

Re: ICE3B0365J Troubleshooting (W200 Sub)

The reason for the VCC fluctuating is the thing I'm not sure about. I have swapped all the caps and diodes in that area but the power isn't even getting to them as the secondary side of the transformer is dead, though the transformer itself is fine. I can only assume it is something to do with the feedback voltage (though I have no idea what value it is supposed to read) or the IC itself needs replacing. The fluctuating SoftS is to be expected due to its relation the the VCC, and the CS is dead because the secondary on the transformer is dead with it not starting up. There is a surge of power on startup as read it on the earth rail, but then it dissipates.

Yeah, it's the same board in the Tannoy and those caps and diodes were the first things checked and swapped out anyway. Seems the issue is deeper than simple checks but I am at a bit of a loss, hence posting here.

[SFB]

Re: ICE3B0365J Troubleshooting (W200 Sub)

How would heating the board show anything?

[CapLeaker]

Re: ICE3B0365J Troubleshooting (W200 Sub)

Does lower the ESR on high ESR capacitors. So if it would be a bad startup cap, the unit would work after heating. Opposite effect you get with cooling on caps.

Is the secondary power rail shorted? You should see some resistance as it has 2 load resistors installed.

[SFB]

Re: ICE3B0365J Troubleshooting (W200 Sub)

Ah okay, that makes sense. I have an ESR meter and freeze spray on the way too.

It isn't shorted, but with you mentioning that I did take readings on the transformers a while back (blue is to ground)

[CapLeaker]

Re: ICE3B0365J Troubleshooting (W200 Sub)

Seems like someone had a go with it already and ripped a bunch of pads and a trace out where the stby circuitry is.

Fist off in a PSU there are two grounds. Primary GND is always measured on the negative side on the primary bulk capacitor. Any voltage measurements done in the primary section, that's where your negative probe goes.
The secondary GND is separated from the primary GND. Any voltage measurements done in the secondary goes to the secondary rail capacitor GND.

You got to figure out is it not turning on, because the stby voltage isn't there, or there is something wrong with PSon and it doesn't allow the main power rail to power up.

For your entertainment I squiggled for shits and giggles something together on the fast.

Another thing I noticed is there is a large vertical red resistor in the primary with some brown goo on the bottom? Remove that brown goo and check that resistor. When measurements in circuit doesn't make sense, take it out and remeasure the part out of circuit. Did you check if the mosfets aren't shorted?

Maybe explain exactly what's happening with the psu when you turn it on. Be careful with the heat sinks in the primary, they can be live!!!

[geoff69]

Re: ICE3B0365J Troubleshooting (W200 Sub)

Common faults on these boards - sounds like you've checked some of the caps.

The 5 output caps and three diodes of the smaller transformer. Caps can look fine physically but still be crapped out.

The large 5w 51ohm resistor.

[SFB]

Re: ICE3B0365J Troubleshooting (W200 Sub)

Seems like someone had a go with it already and ripped a bunch of pads and a trace out where the stby circuitry is.

Yeah, as I mentioned in my OP it is a family memebers sub and he tried the initial fixes himself via a couple of threads on AV after it had completely died (he said that prior to this he would have to switch it on and off a couple of times before it fired up) While trying to repair a combination of too much heat and being a bit aggressive damaged the pads and tracers so first thing I did was repair them - I didn't have any magnet wire so used component legs for now, and used a microscope with pictures to make sure I got the connections right. (I have attached a photo of the undamaged area I found online.)

The original problem was the 51ohm/5V resistor had crumbled and there were signs of corrosion in that area so he replaced that, and after that didn't work replaced the main 3 caps and 3 diodes in the start up by default as they appear to be the usual problem. When that again didn't work he gave it to me to have a look at as knows I have an interest and trying to learn more.

First off in a PSU there are two grounds. Primary GND is always measured on the negative side on the primary bulk capacitor. Any voltage measurements done in the primary section, that’s where your negative probe goes.
The secondary GND is separated from the primary GND. Any voltage measurements done in the secondary goes to the secondary rail capacitor GND.

Yes, I have been doing this.

You got to figure out is it not turning on, because the stby voltage isn’t there, or there is something wrong with PSon and it doesn’t allow the main power rail to power up.

For your entertainment I squiggled for shits and giggles something together on the fast.

From the things you marked, the only ones I haven't tested are the inductor, the feedback opto, and the load resistors (which I assume you have to test out of circuit with being parallel to caps?)

Another thing I noticed is there is a large vertical red resistor in the primary with some brown goo on the bottom? Remove that brown goo and check that resistor. When measurements in circuit doesn’t make sense, take it out and remeasure the part out of circuit. Did you check if the mosfets aren’t shorted?

That was the original replaced resistor and I have checked it since I have had the board. I did check both the mosfets and the diode near the inductor and all are fine.

Maybe explain exactly what’s happening with the psu when you turn it on. Be careful with the heat sinks in the primary, they can be live!!!

Originally we were just getting a blinking LED, but that is constant now, but no audio to speaker. There appears to be an initial surge on the primary up to the primary of the main transformer but then just drains off. The standby circuit just remains dead. Is there anything I should be looking at in particular?
And yeah, they are live.

Common faults on these boards - sounds like you've checked some of the caps.

The 5 output caps and three diodes of the smaller transformer. Caps can look fine physically but still be crapped out.

The large 5w 51ohm resistor.

Yes, they have all been replaced besides the 2 smaller caps near the standby pins, but they checked fine with a multimeter.

[SFB]

Re: ICE3B0365J Troubleshooting (W200 Sub)

*update*

After checking a few components out-of-circuit yesterday and doing a few continuity checks this morning, I just reconnected everything and now getting the expected voltages across the 4 pin (+7/-7, 3V) and 54V, the LED is staying on, but had no sound until I swapped the speaker connectors around and now it is all working fine.
What could have caused the change as I am absolutely baffled?

[SFB]

Re: ICE3B0365J Troubleshooting (W200 Sub)

***** it!!
It died again. No sound, LED staying red and blinking.
Better than being totally dead like it was before I guess.

[CapLeaker]

Re: ICE3B0365J Troubleshooting (W200 Sub)

Seems like a cold or broken solder joint or trace. Since it did started to work on some point. Could be also a broken wire on a transformer leg. Start pushing on things with a plastic tool. Maybe reflow the amp ic with the Million legs.

[SFB]

Re: ICE3B0365J Troubleshooting (W200 Sub)

I have already checked the small transformer for the standby circuit, but not the big one.
I will take some measurements again and see if anything has changed, then have a prod around.
Is the amp IC the one on the vertical board with 16 legs?

[CapLeaker]

Re: ICE3B0365J Troubleshooting (W200 Sub)

sorry... was thinking about a different amp.

In any case... its got to be something stupid as you got it to work.

[SFB]

Re: ICE3B0365J Troubleshooting (W200 Sub)

Yeah, it's frustrating as it died while my uncle was here to pick it up - I was showing him the issue with mine and out the corner of our eye saw the light start blinking. ESR turned up today and on a quick check caps seem fine, but got plans today so will have a proper look this evening or tomorrow.

[geoff69]

Re: ICE3B0365J Troubleshooting (W200 Sub)

How you getting on with this?

I'm tackling the same board and just waiting on caps to arrive