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Old 3rd May 2010, 1:36 pm   #121
FERNSEH
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Default Re: Pye v4

As a quick test to confirm if the CRT is working. Apply a short circuit between pins 2 (G1) and 11 (Cathode) on the CRT socket. This will remove any bias to the tube and the gun will operate at full conduction, therefore there will be max brightness if the ion trap is adjusted correctly.

DFWB.

Last edited by Station X; 3rd May 2010 at 2:40 pm. Reason: Electrode names added.
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Old 3rd May 2010, 1:43 pm   #122
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Default Re: Pye v4

I think the CRT is deceased it was faint when I had the line/band perhaps it died as pin 2 - 11 short produces Zilch! I've tried rotating the ION trap too
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Old 3rd May 2010, 1:51 pm   #123
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Default Re: Pye v4

With regard to the voltage readings round the brightness contol, I would have expected the voltage on the brown lead to be higher ie around 80% of the HT Voltage. The lower voltage on the black lead, which I assume is the wiper or centre tag of the pot, should get much closer to zero volts. It's only getting down to 116V. Are the resistor values correct?
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Old 3rd May 2010, 2:23 pm   #124
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Default Re: Pye v4

I noticed Kevin in the VT2 thread did this "shorting the cathode to the heater has brought some life to the screen" is this another possibe test to do or not
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Old 3rd May 2010, 2:33 pm   #125
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Default Re: Pye v4

I don't know about that, but there is obviously something wrong with the brightness control. With the wiper in the lower position it's connected to chassis, so should read close to 0V, not 116V with respect to chassis. This is a definite fault you can work on. Something you can measure.
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Old 3rd May 2010, 2:39 pm   #126
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Default Re: Pye v4

Hi Chris.

You have just done this shorting the cathode to heater pins of the CRT 2 -11 as in Fernseh post above as well! Do try to move ion trap just to see any life! If not well who knows!

Kevin
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Old 3rd May 2010, 2:40 pm   #127
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Default Re: Pye v4

Just don't know if it's worth continuing, seeing as I tried the short of CRT control grid to cathode an it produced nothing. I tried adjusting the ION trap as well. I've been at this for nearly 3 days now and if the CRT is not going to light up then I'm putting this PYE back to bed and moving on.

Sorry Kevin I was confused I thought pins 1&12 were the heaters, and the test I just did was control grid to cathode.

Confused
Chris
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Old 3rd May 2010, 2:44 pm   #128
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Default Re: Pye v4

Did you apply the short and adjust the ion trap both at the same time?
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Old 3rd May 2010, 2:46 pm   #129
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Default Re: Pye v4

yep, 2 & 11 then tried adjusting, I have an idea where the trap should be from when I captured the beam before but nothing and I've tried 360 rotation
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Old 3rd May 2010, 2:50 pm   #130
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Default Re: Pye v4

Hi Chris

My Mistake there yes Frenseh did as you say short between G1 pin 2 and cathode pin 11! As I say i Did get a raster on screen by shorting cathode to heater!

Kevin
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Old 3rd May 2010, 3:15 pm   #131
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Default Re: Pye v4

Hi kevin, I was worried about your test which is why I never did it, as the cathode currently has 220V and the heater normally only gets 6.3V therefore doing your test I thought would fry it.

I do think this is game over with a failing CRT. I shall have to look out for another.
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Old 3rd May 2010, 3:20 pm   #132
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Default Re: Pye v4

The fault could be:-

Wrong voltages on CRT pins, including perhaps the heater (measure the AC volts between pins 1 and 12.
Low EHT voltage.
Badly adjusted ion trap magnet.
Faulty tube.

I'd eliminate the first three before condemning the tube.
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Old 3rd May 2010, 3:26 pm   #133
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Default Re: Pye v4

Hi Chris.

Yes your cathode does have a lot of voltage there the VT2 has about 130v and like you I'm just new to this TV repair so I'm not sure what is good for one set is therfore OK for another! I bet mind its not the CRT if it tested OK on a tube tester! I kept thinking it was my CRT but mine was giving such good results / readings on my old tube tester! I wonder if you have low EHT!

Kevin.
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Old 3rd May 2010, 3:26 pm   #134
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Default Re: Pye v4

Hmmm had not thought of checking heater thought they were ok but probes on 1 &12 register 1613mV 1.6V !!

confirmed using both DMM and AVO 7, now to find out what's bringing that down.

Thanks for being the voice of reason Graham
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Old 3rd May 2010, 3:35 pm   #135
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Default Re: Pye v4

It could be a partially short circuited tube heater. I'd check the AC voltages on other valve heaters to see if they have a problem too.

Obvious suspects R134, R135, R136 (assuming these three are in circuit), R137, R138 and its parallel thermistor.
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Old 3rd May 2010, 3:43 pm   #136
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Default Re: Pye v4

R134, 135,136 thats the multi-tap resistor that only works on the 220 tapping that im using now, see post #33

R137 check out ok

Random test's on random valves confirms mV on heater chain

Last edited by oldticktock; 3rd May 2010 at 3:54 pm.
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Old 3rd May 2010, 4:17 pm   #137
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Default Re: Pye v4

This must be the source of my problem as mentioned in post #33 only could get the set to fire up on setting 220V

What confused me is the heaters in all the valves are nicely lit, so never suspected an issue and the screen giving the fat line.

After measuring and finding mV on the heater chain, I went back to the R134,5,6 resistor and at most points on that i'm getting mv, also on close inspection the top most wire wound looked open, touched it with a probe and boing! it unravelled.

Now I need to find one of these to replace it, its a 10R/20R/20R
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Old 3rd May 2010, 4:27 pm   #138
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Default Re: Pye v4

Are you sure you are measuring AC? If they are lit then they must be more than mV.

You should at least be able to get it back to displaying the line.
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Old 3rd May 2010, 4:38 pm   #139
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Default Re: Pye v4

This is what i get for sticking my head up a PYE's...... for the last 3 days. Meter was not set correctly V9 the valve before the CRT is 6.3V on heater randomly checked others and heaters fine, but CRT's heaters are reading mV checked and double checked and checked again so back to the suspect CRT.

You all must be sick to the teeth, not another OTT thread rambling on for pages so I shall disappear and stop taking up all your valuable time.

Chris

Last edited by oldticktock; 3rd May 2010 at 4:44 pm.
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Old 3rd May 2010, 4:46 pm   #140
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Default Re: Pye v4

Well that would explain the lack of emissions! Take off the socket and measure the resistance between the socket pins and the resistance of the tube.
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