Pye v4

[Kevin19]

Hi again Chris.

As some one else quite new to trying to restore TV's I know how frustrating this can be and I think again this shows us what John W. Keeps Telling us about how important it is for the likes of us very new and inexperienced with TV repair to get something on screen as soon as possible! Just a though when I was getting just a blank screen on my Pye VT2 I did force a raster up of sorts up on the screen by shorting the cathode pin on the CRT base to one of the heater pins on the CRT base I would assume maybe OK to try this on your set maybe ? I rather missed most of yesterdays posts and have not looked back at them all but did you try the continuity of the scan coils? I did this on the VT2 as I thought they might be duff on that when no raster or anythink would come up?.
Sorry you have had no joy with this one up to now.

Kevin.

[oldticktock]

Originally Posted by Kevin19

John W. Keeps Telling us about how important it is for the likes of us very new and inexperienced with TV repair to get something on screen as soon as possible

Hi Kevin,

That's what really peeved me, I had the screen talking as such, and now the blighters gone blank on me after the EHT went.

I replaced the PL81 and PY81 and EHT restored, line whistle present, just the ominous buzzing, which was present a bit yesterday accompanied by a blue glow on the PL81. The blue glow is now gone, but this buzzing is back, I can seem to afffect it by twidling the horizontal hold but not like yesterday when I could make it go by doing that.

Should have stuck to Bush, when I get the TV22 this is going to be booted into the back of the loft as it's tried my patience.

Chris

[oldticktock]

Can some of the TV guru's comment on my post #85 & #89 is this a possibility? although with the buzzing i'm not sure its relevant anymore.

Chris

[Courtney Louise]

Chris, I am no help to you at all having only ever restored 1 TV22, but I admire your will power and sheer determination, A credit to the hobby and an inspiration to many...

Andi

[PJL]

Originally Posted by PJL

g1 wrt k should be -ve. Adjust brightness to minimum and check g1 which should be 0, it seems too high to me.

It's far from over...you have positive grid current. My guess is the brightness control.

[oldticktock]

My gut was always around the brightness area too, I asked a few questions about this lastnight but not much response.

I changed C59 just now that is connected to chassis one side and to pin9 PY81.

I put the old PL81 back in and it still works put the old PY81 in and no EHT, that confirms the PY81 failed.

With the old PL81 back in the blue glow is dimmly present the buzzing is there but again can be controlled by the Horizontal Hold.

CRT readings
pin2 (control grid) 114V
pin10 (1st anode) 225V

PL81
pin2 (g1) -17V
pin8 (g2) 154V

Boost cap one side 453V 200V the other side

[Station X]

can someone explain, I was measuring voltage around the brightness control

There are 3 connections

one goes off to chassis
one goes off via a black wire to a tag, which goes off to a resistor then a wax cap and onto pin6 of an ECC82. (wiper connection?)
one goes off via a brown wire to a tag then via resistor (R64?) to a 12uf electrolytic. (HT connection?)

Meter neg clipped to chassis
probed brightness tag with black wire, can't remember the exact measurement but was 100+V
probed brightness tag with brown wire and a large crack/spark,made me jump!

why was this, I'm shutting down now after a fruitless day.

There isn't much to the brightness control circuit. It's just a potential divider connected between chassis and the HT rail. The voltage at the wiper is then taken to the CRT. You should be able to check the resistors concerned with a meter on ohms range, but you'll need to lift one end of R64 to prevent shunting. I'm referrng to the circuit in post #72. Check R64, R65 and R66. Replace what looks like C51 (off page) if you haven't done so already.

If all resistors are OK check the voltage from chassis to each of the brightness control tags. The voltage on the wiper should vary with the control's setting as should the pin on the CRT to which R66 is connected.

[PJL]

Originally Posted by oldticktock

With the old PL81 back in the blue glow is dimmly present the buzzing is there but again can be controlled by the Horizontal Hold.

Set the horizontal hold for highest frequency (if you can hear it!) until something is on screen.

[oldticktock]

Took a reading on CRT pin2(control grid) with brightness control at one end of its rotation 61V at the opposite end of it full rotation 142V

also clipped in a 10Uf electrolytic to C51 no change (now removed)

[Station X]

Given that one end of the brightness control is connected to chassis I would have expected the lower voltage to be close to zero. What are the specified values of R64 and R65?

[oldticktock]

R64 6.8K
R65 25K (brightness pot)

[Station X]

OK. Top end of R64 should measure the same as the HT voltage. Bottom end of R64/top end of R65 about 80% of the HT voltage. Bottom end of R65 zero volts.

Wiper voltage should vary between the end voltages of the pot. They won't be exactly the same as some of the pot track wil always be in circuit.

Top and bottom refer to the positions on the circuit diagram.

[oldticktock]

see post #93 when I measured one of the tags on the brightness pot, don't want to do that again.

I will measure around R64 though

top of R64 201V
bottom of R64 1200mV

[PJL]

g2 wrt k should be 250 and g2 is 450 so k should be about 200V so there seems to be a problem there too.

[Station X]

see post #93 when I measured one of the tags on the brightness pot, don't want to do that again.

If you've measured at the wiper with the brightness contol set to the top end of its travel that's exactly the same as measuring to the top tag.

[Station X]

I will measure around R64 though

top of R64 201V
bottom of R64 1200mV

That points to a short circuit across R65. It's inconsistent with your previous readings though. Check everything with a meter on ohms range.

[Station X]

In a previous post you said that the brown wire on the brightness control, which I assume goes to HT via R64, gave a spark when probed and made you jump. This is the same point as the bottom end of R64 which now measures 1.2V. Unless something has changed this cannot be true.

[oldticktock]

Just did the continuity tests on both tags of R65 following circuit all ok

Measured the tags with power on ok now, must have been me last night

[Station X]

So what are the voltage readings now then? Both ends of R64, all three tags on R65 with the wiper on both end stops.

[oldticktock]

see pic