Is this about right, or should I go and stick my head in a bucket of offal?
Do you like offal
Not as such, no...
Wot! Not even liver and onions? Or steak and kidneyt pie?.. 
Marion
Wot! Not even liver and onions? Or steak and kidneyt pie?..
Marion
Definitely not! 
Except Chris has established there's 13V at the collector of VT413. Were W412 to have handed up the dinner pail I wouldn't expect that to be there. Similarly, T401 has been swapped.
Ah, my apologies then. I had missed that T401 was a replacement, and was relying on the voltages quoted about four post back. I thought that they may have indicated a shorted 12V zener, but I must have missed something else further back
No worries, Graham. I have to apologise too, btw: I said there was 13V at the collector of VT413, but there's not of course - there is 13V at PL20/2 which implies that the regulator is doing its job (I forgot to take the collector resistor R425 into account).
My biggest worry is that to all intents and purposes, VT412 appears to be in a state of perfect saturation, yet I don't know of a single transistor that can saturate to 10mV! It really does look like it's breaking down totally (in an avalanche kind of stylee) when it first gets exposed to the rectified mains at start up.
I know you've tested VT412 Chris, but have you changed it?
I wasn't working from the voltages quoted for PL20, I was looking at Chris's notes here -
viewtopic.php?f=5&p=98478#p98445
Had you noted VT413 volts on that list?
I had indeed.
It seems this regulator works by adding the 12V drop across W412 to the Vbe value of VT413, so the top of R425 will settle at (Vz +Vbe), Vc varying with load to maintain the 'regulated' supply. It looks like a particularly odd shunt regulator and no, I don't like it either!
W712 tested good
I have not replaced T401 as mentioned above ( i'm not surprised there is confusion in this thread now) I wouldn't have anything to replace it with
Mike I've not replaced VT412 for the reason you state, it tested good but if you think I should then I will. Only problem is I need to find out what a TE527 equivalent can be installed.
I have not replaced T401 as mentioned above ( i'm not surprised there is confusion in this thread now) I wouldn't have anything to replace it with
Ah, right - it was the other two transformers you did. I'd check, as Graham suggested, that its windings have at least continuity then, in that case.
Mike I've not replaced VT412 for the reason you state, it tested good but if you think I should then I will. Only problem is I need to find out what a TE527 equivalent can be installed.
I think it's breaking down when it first gets hit by the raw rectified mains and stays that way. Of course, that could be a complete load of pony but I'm struggling now.
Anyway, time for this old fool to shower the offal out of what remains of his hair and call it a night....
As suggested removed the line driver transformer T401, 46R across the primary 0R across the secondary. I've no idea what the actual values should be but I somehow don't think the secondary should be zero 
So unless I can find a spare 9000 board or just a spare T401, that would appear to be game over for this set. Guess you can't win them all.
Just ring it like a LOPT. It should be the same.
I'm afraid it's not that easy to escape....
If you mean 0R in the same way as touching your meter probes together, then that is to be expected, It will not be many turns and will probably come out at less than an ohm. A low ohms meter, or using the divide by 100 range on the trusty old AVO, is the best way to take such readings.
Graham.
I did use the AVO, although it is understandable you would think I did not, considering my preference for the Fluke. I did use the AVO on divide by zero and got what looked like Zero OHMS(0R) just as though the probes are together, if there is under an ohm there, it was imperceptible to me.
I just checked this on the Bench meter which is very accurate (checked on a 1% reference) and all I get is 0.1R for the secondary, no surprise all I thought I saw was 0R on the AVO. I did say I had no idea what the values should be for primary/secondary and if you're saying that 0.1R is correct for the secondary then I stand corrected and will enjoy getting back into the game.
Hi Graham,
I already did the ring test this morning, it does ring and does not look dampened, however I could never get it to lock. The ring had a shadow that keeps oscillating up and down. I will try and photo if I can. I only have experience of ringing lopts which I've grown accustomed to spotting good from bad and always get a good lock.
I think the second test of the 9905 sounds like a good backup to confirm.
T401 ring, as I say I've only rung LOPT's compared to them this looks wrong but it may well be ok for this type of TX. As I also mentioned above, the shadow trace oscillates up and down with the first, again something I've not had before. I tried adjusting the trigger and hold off, to no avail.
Anyway to save going off on a tangent I will take the quick route and match to the D|E|R line driver TX
After some chores, back at the coal-face. Tested T401 from the 9905 chassis, it reads the same as the 9000 T401, so not that then.
I don't have either in stock so this will have to now wait until I can source a replacement.
Just found a BD410 which might suffice, 500V, 1A, 20W what do you think?
MJE340 -/300V, 0,5A, 20,8W, >10MHz
Hi Graham,
The Mica insulator was a bit dark but then again I have some NOS dark shaded Mica washers so didn't think anything of it and left it. I will before swapping the transistor try a new insulator just in case. 
The ring test is a good one and it too good for the scope to lock as the ring is sustaining long enough to stop the scope triggering correctly
With the transistor just go for a high HFE and plenty of VCE volts as you already have done.
You have got an insulation tester to check between the collector and the heat sink if you can isolate it from the chassis easily.
Well would you believe it the Mica insulator must have broken down. I put it between two fingers and flexed it, a good one flexes easily, this one shattered. 
Fitted a new and the 9000 sings again (see below)
What I find deeply frustrating is this all started when I was about to start fault finding the mute issue on the PC852. I had the set on to take voltage readings, thats when the tripping started, I spent ages swapping LOPT chopper, testing diodes, and caps only to find it was VT413 the 12V regulator causing the tripping. Whilst that occurred the insulation on VT412 decided to thrown a curve ball into the mix. Talk about giving me the run around. 
So back to the PC852 and the sound issue, I becoming paranoid now about what next is going to stop me in the pursuit of the answer.
Don't get mad at me, but what deeply frustrates me is that you went on the mad spree of changing the LOPT and the Chopper TX at all. I must be a pretty rubbish tutor
Graham.
What sent me down that route was the tripping fault, my inexperience with it and religiously following the 9000 fault finding guide. Nothing to do with your teaching ability, in fact if it were not for you, Mike and John I would have put this TV in the bin by now.
As you say moving along... I'm going to have a coffee then try and get this set sown up this evening, if I can.
Unwanted muting should be a fairly easy fix on the R/C board.
Graham.
John said that right before the two faults presented themselves, sending me on a few days spin in madville!
We've all been caught out with duff insulators at some stage. Some announce their demise by arcing just before other things are destroyed. Others sit there grinning at you waiting for you to waste time changing other things before you finally discover the real culprit....
Look on the bright side Chris. At least you don't have a customer breathing down your neck complaining that their weekend has been totally ruined and the kids have had nothing to do because of lack of TV...
You'll be a Thorn expert after all this.
