Ferguson C51N (ICC8) Frame Fault Help Needed

[Maarten]

CL09 blowing up suggests the same cause may have blown up the IC as well. I didn't figure it out yet but that seems the first place to start searching for the fault.

Did you replace CL09 and measure the voltage across it?

[IKC2E51R8]

CL09 was replaced as its part of the Frame Kit

[Maarten]

Ah of course. What voltage does it have across it? I think you can safely take measurements without the field output IC.

[Philips210]

Any chance of seeing the relevant part of the circuit diagram please?

Regards,
Symon

[IKC2E51R8]

I've since discovered that the Line Driver transistor is shorted which I've read can happen when the field IC fails, I'll have to go through my pile of boards for a suitable replacement, it's a BSR51. TL17 is its position.

Back to the Field IC, I've tested it and I think the current one (STV) is OK however i think that during repair work of a nearby pad I think two of its pins may have been bridged causing the field not to work, i think the Line Driver died from the first TDA replacement that blew up. I'm going to clean up the area and inspect all the pads for a good connection and then once iIlocate a new line driver transistor i'll test it again.

Would anyone know off the top of their head what a suitable replacement would be for the line driver transistor (BSR51) I've a scrap IKC2 board with a BSR50, would that work?

Here's the field diagram.

[williamsunique]

BSR50 and BSR51 are different. One is npn the other is pnp. They are also Darlington transistors and measure differently to other transistors.

Paul

[IKC2E51R8]

Originally Posted by williamsunique

BSR50 and BSR51 are different. One is npn the other is pnp. They are also Darlington transistors and measure differently to other transistors.

Paul

Looking up data sheets for both, it says they're both NPN? different Voltage rating on them but both NPN

[Maarten]

Possible red herring alert. If the EHT comes up for a moment, TL17 is not likely to be defective. How did you conclude it to be defective? Keep in mind it's a Darlington. Also, I see no reason whatsoever it would be affected by a vertical fault.

That said, the only difference between BSR50 and 51 is that the former has a lower max voltage. It might be fine in this application, but don't replace it if it isn't defective.

[Philips210]

Thanks for the circuit.

I recall many years ago with the old TDA1170S field IC that it could be instantly destroyed if the feedback path in the deflection circuit became open such as an o/c or dry jointed electrolytic cap. I am not sure if this could apply with the TDA8178FS. I'd certainly carefully check all electrolytics and diodes in the field stage as well as crusty solder joints.

I've found a couple of TDA8178FS chips, one a pull and the other unused if you get stuck finding a replacement.

Regards,
Symon

[G6ONEDave]

If the original driver is a BSR51, then I would replace with the same or possibly a BSR52, as that is similar spec at higher voltage. I would never use a lower voltage rated device as a replacement.

Dave

[williamsunique]

Originally Posted by williamsunique

BSR50 and BSR51 are different. One is npn the other is pnp. They are also Darlington transistors and measure differently to other transistors.

Paul

Ah yes both NPN.

Paul

[IKC2E51R8]

This chassis is literally impossible to work with, I've checked everything again, i reworked any damaged pads, I replaced RP62 again, The IC seems to be fine and still the set on power on has the EHT come up for a second, chips once then completely dead, no secondary voltages at all.

[Red to black]

The ICC7/8 wasn't too bad a chassis to work on, it had a few quirks but was far more normal than the ICC4 and 5 even the IKC2, the ICC9 and IDC2 chassis were far more difficult to get your head around!

The ICC7/8 frame chip was unusual in that it didn't use a diode/capacitor flyback generator voltage doubler but instead used a separate 65Volt supply(pin 3) to initiate frame flyback action, this could lead to problems if the normal field supply (24Volts) and the 65Volt flyback supply became shorted together either via the chip itself, or via one of the isolation diodes DF16,17 and 18 within the frame circuit.

I haven't had time yet to go through the circuit itself as work (paid) has got in the way still

Ps. the ICC8 differs from the ICC7 mainly in software plus the addition of 16:9 switching and also updated small signal stages mainly in the auto greyscale parts

[Red to black]

Ps2 one of the main causes of line driver transistor failures (if that is still the case?) on this chassis and the ICC7 was dry joints on the scan coil connections on the back of the small yoke pcb with Philips tubes

[Red to black]

Ps3 I think it also had S-video in software via the scart and front connection by default rather than the hidden manual physical switch by the scart socket on the ICC7
It was basically an update of the ICC7, the Psu, time base and basic chassis was the same rather than a totally a new chassis

[IKC2E51R8]

The line driver is OK, i reworked some dry joints in the PSU section and now it's at least coming on but still has field collapse but the line is slightly wavy to the left most side of the screen.

I think there may be something else in the field circuit causing the collapse but I'm not sure what, there's no shorts on the field IC and the connections all look to be OK in the area.

[IKC2E51R8]

Getting voltages is difficult, I can measure in standby but if i try to turn on it sometimes comes on and sometimes trips.

HT at Pin 3 of LOPTX 118.8v

Field IC
Pin 1: 2.6v
Pin 2: 20.2v
Pin 3: 20.1v
Pin 4: GND
Pin 5: 20.1
Pin 6: 20.2v
Pin 7: 19.8v

ON
Field IC
Pin 1: 3.3v
Pin 2: 25.2v
Pin 3. 67v
Pin 4. GND
Pin 5: 25.4v Anytime i try to measure Pin 5 (Output) The set trips immediately - I managed to see that 25v just before as it tripped.
Pin 6: 25.2v
Pin:7 24.8v

Can anyone more experienced deduce what might be happening based on these voltages?

[Red to black]

iI it is a wavy line then that suggests an open circuit field yoke/scan coil, I am not sure who else with more experience you are going to get.

[Red to black]

You might want to look at the Line output flyback caps as well as these can increase the LOPT derived supplies significantly and cause major problems too as per cL09 venting its top.

[Red to black]

Until you get a scope mate you are pissing in the wind, this will be the last help you get from me until you start fault finding properly, I haven't the time to do this for you