[dominicbeesley]

Thanks Steve P

It certainly is - just not sure why it is so intermittent and fussy - it has come to life briefly a few times. I've been listening to the whistle and it sounds pretty close I was listening carefully and it didn't sound to change when the picture died.

I've already changed the V10 (LOP) grid coupler before I started and boost cap afterwards...still not much change

PJL,

I've been using a valve voltmeter as well for the high impedance measurements and boost (before the 10M resistor - which I've swapped) is only 260V.

I've just got a Pye manual from Jonz Valve Pages (he very kindly scanned it last night) this has a lot more info about the line stage and what to expect voltage wise so will have a poke round with a scope later.

For a while I thought that it was grid current and a gassy valve but when it came to life yesterday for the last time there was a half decent raster...well there was lines - about twice as thick as they should be and spaced out but the tube looked like it wasn't entirely dead.

Here's a few measurements:


I made a few measurements last night before I went to bed...

Numbers in brackets are those quoted in Trader sheet - all taken with Valve voltmeter
V12[A] 177V {198}

V10[S] 163 {153}
V10[K] 6 {4.8}
V10[G] -13.5

V9a[A] 83.7 {110}
V9a[K] 3.8 {3.6}

V9b[A] 132 {85}
V9b[S] 115 {96}


Tonight I think I'll try grounding the line flywheel discriminator output and messing with line hold to get a reasonable frequency and see if that helps any.

Scope through the line stage and try and get boost voltage up to 400+V - I'm still not sure what it should be!

Measure all resistors in line circuit and check the scope points in the V4 technical manual.

It seems the other thread has damped everyone's enthusiasm for thinking about V4s! I should have bought that Fergy instead...Thanks for any help or advice!

Thanks

Dom