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Old 2nd May 2010, 6:43 pm   #81
oldticktock
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Default Re: Pye v4

Changed the coupling cap as suggested

I have already changed the boost cap.

PL81
Pin2(g1) -17V
pin8((g2) 150V

The fitting of the French PL81 to mask a on going fault does not bode well.

Last edited by oldticktock; 2nd May 2010 at 6:51 pm.
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Old 2nd May 2010, 7:13 pm   #82
oldticktock
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Default Re: Pye v4

changed the 3.3K resistor between pin8 PL81 & pin9 PY81

PL81
Pin2(g1) -21V
pin8((g2) 160V

CRT
pin2 145V (control grid)
pin10 216V (first anode)

Lost line on screen after EHT lost this afternoon has not returned ( I have EHT back just nothing on screen now)

Last edited by oldticktock; 2nd May 2010 at 7:21 pm.
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Old 2nd May 2010, 7:18 pm   #83
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Default Re: Pye v4

Is the EY51 lit? If not, are all connections to it sound?

Fit new PL81 and PY81. Check your soldering.

Do you have line whistle and does it vary with the Line Hold control?

Cheers,

Steve P.
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Old 2nd May 2010, 7:19 pm   #84
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Default Re: Pye v4

yes to all
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Old 2nd May 2010, 8:40 pm   #85
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Default Re: Pye v4

Has anyone got the pins for MW36-24

With all the readings I have I should have something on screen, I have read that in this scenario It is advisable to connect the negative meter lead to the grid pin of the CRT, and the positive lead to the cathode. With a blank screen the reading should be about 30-40V or more, and it should be possible to adjust the brightness control until the reading falls to something like 10-20V, when the raster should now show on the screen. What I would be reading is the actual bias, and if there is no illumination you can safely take it right down to zero, if that is within range of the brightness control. If there is still no illumination the fault lies elsewhere in the bias circuit.

Last edited by oldticktock; 2nd May 2010 at 8:58 pm.
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Old 2nd May 2010, 8:44 pm   #86
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Default Re: Pye v4

Found this http://www.radiomuseum.org/tubes/tube_mw36-24.html
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Old 2nd May 2010, 8:57 pm   #87
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Default Re: Pye v4

Could the ion trap have been accidentally moved from the optimum position since you last saw the screen lit?
Pete
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Old 2nd May 2010, 9:09 pm   #88
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Measure the volts on the CRT again and don't forget the cathode.
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Old 2nd May 2010, 9:09 pm   #89
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Default Re: Pye v4

The ION trap did get moved but I remembered where it sort of was within reason, and have spent ages positioning it without luck. The previous on screen band was faint and I'm wondering if it might be there but what also might be happening is bias has gone down to chassis or possibly even more negative than that where the screen will go blank.

I think the Pins for the test will be neg lead on pin 2 and pos lead on pin 11 but would like someone to confirm as the sort of day i'm having today I can see me adding to my woes.

Chris
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Old 2nd May 2010, 9:20 pm   #90
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Default Re: Pye v4

I don't know what all the pins are so forgive not providing the full decode.

Pin1 Heater
pin2 139V (control grid)
pin3 not present
pin4 not present
pin5 112V
pin6 112V
pin7 112V
pin8 110V
pin9 not present
pin10 220V (first anode)
pin11 112V (I believe this is the cathode, could be wrong)
Pin12 heater

Last edited by oldticktock; 2nd May 2010 at 9:35 pm.
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Old 2nd May 2010, 10:04 pm   #91
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Default Re: Pye v4

Quote:
Originally Posted by oldticktock View Post
The ION trap did get moved but I remembered where it sort of was within reason, and have spent ages positioning it without luck.
IIRC the proceedure to set one if there is no line marked on the neck is to swing it round the neck first to get a raster and then slide it back and forwards along the neck for maximum brightness repeating as need be.

It will be good practise for when you get started on 70s colour sets and have three of these similar horrible things to swing about to get the convergence right

Dave
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Old 2nd May 2010, 10:34 pm   #92
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Default Re: Pye v4

http://www.shinjo.info/frank/sheets/030/m/MW36-24.pdf. Your voltages are still very wrong possibly because the boost voltage is still low. You have already replaced the PY81. Try measuring either side of C57 (HT and boost).

You could end up damaging the LOPT as the PL81 seems to be drawing too much current. The only surprising thing is you had full width when it was working.

Afraid you need more help than I can offer at this stage.

PS: The caps that could be responsible include C57, C56, C59, C55

Last edited by PJL; 2nd May 2010 at 10:43 pm.
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Old 2nd May 2010, 10:49 pm   #93
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Default Re: Pye v4

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.
one goes off via a brown wire to a tag then via resistor to a 12uf electrolytic

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.

Chris

Last edited by oldticktock; 2nd May 2010 at 10:57 pm.
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Old 2nd May 2010, 10:57 pm   #94
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Default Re: Pye v4

One side of Boost cap reads 496V the other side 203V
I have already changed C57,C56 and C55 but not C59
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Old 2nd May 2010, 11:25 pm   #95
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Default Re: Pye v4

Hi Cris,
Have you changed C108 the A1 volts decoupling capacitor? The high voltage at one end of C106 (496V) tells me that all is well with the line output stage.
As the CRT cathode volts are 112 (pin11) and the A1 volts are 220 (pin10) the actual A1 volts are still low at 108 volts with respect to the cathode.

Might be worthwhile checking R130 (10Megohms) for high value.

DFWB.
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Old 2nd May 2010, 11:38 pm   #96
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Default Re: Pye v4

Hi david any chance you could relate that to trader sheet as I cannot read the pye image
chris
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Old 2nd May 2010, 11:48 pm   #97
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Default Re: Pye v4

That would be C56 I think, change C59 anyway although the boost voltage looks OK.

Check R71. What's the input impedance of your meter?
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Old 2nd May 2010, 11:51 pm   #98
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Default Re: Pye v4

The images of the timebase circuits came from one of the Newnes TV and radio servicing books. I do not have a Trader service sheet for the Pye V4.

C108 is easy to locate. Find the wire which connects pin 10 of the CRT to the chassis wiring. That will lead you to the capacitor 108 and the 10 Megohm resistor.

DFWB.
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Old 3rd May 2010, 12:22 am   #99
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Default Re: Pye v4

That would be C56 I think, change C59 anyway although the boost voltage looks OK.

Check R71. I think it's just the input impedance of your meter causing a low g2 reading. I don't have enough of the circuit or values to help further. 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 also posssible the other crt readings are impacted by the meter impedance or it could be leaky capacitors in g1 or k circuit.
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Old 3rd May 2010, 7:18 am   #100
oldticktock
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Default Re: Pye v4

C56 (C108) already had been changed

Checked R71(R130) and it had gone high (12.8M)

Replaced R71(R130), no change, I have the buzzing sound quite loud and I think it's hard to tell, that it's coming from the LOPT.

CRT
pin2(control grid) 139V
pin10(first anode) 222V

I could be wrong but I think it's game over on this set, could that buzzing be an internal short in the LOPT.

Last edited by oldticktock; 3rd May 2010 at 7:24 am.
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