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Old 1st May 2010, 10:58 am   #41
Sideband
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Default Re: Pye v4

Hi OTT. To measure heater continuity on the EY51, you will have to disconnect one heater wire otherwise you are measuring across the heater winding on the LOPT which will measure very low.


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Old 1st May 2010, 11:01 am   #42
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Default Re: Pye v4

Thanks for the clarification Rich, just nervous about desoldering on such a sensitve area. Will bite the bullet and go for it, I have spare EY51's.

Chris
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Old 1st May 2010, 11:04 am   #43
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Default Re: Pye v4

Just make sure when you resolder that you don't leave any 'spikes' on the solder. Ideally they should be nice, smooth rounded blobs.


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Old 1st May 2010, 11:15 am   #44
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Default Re: Pye v4

Hi Cris,
I've noted your readings from the CRT base. Pin 10 is the first anode (A1) and 135 volts are too low. According to the Mullard data for the MW36-24 the minimum volts for the A1 should be 200. As the cathode voltage (pin 11) is 76 the AI volts should be at least 276.
Your reading for pin 2 is 105 volts which means that the control grid is too positive. It is likely that the cathode voltage is too low, something like 125 volts would be normal under no signal conditions.
Again, according to the Mullard data the CRT grid voltage for cut-off is -33 to -72 volts.
The line output stage is faulty. For starters check the coupling capacitor to pin 2 of the PL81 and also the boost capacitor.

DFWB.
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Old 1st May 2010, 11:21 am   #45
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Default Re: Pye v4

That was horrible not having desoldered an EY51 before I was unsure. Looking at the bottom in, the left top was one leg of the Heater, the top right was where the EHT lead attached ( I thought this was where the other Heater was attached) and the bottom was the other Heater. all basic to you guys but a lesson logged for me.

After all that the continuity is fine.

Thanks David, will check around PL81 as you say.

Now to get the EY51 back GULP!

Last edited by oldticktock; 1st May 2010 at 11:37 am.
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Old 1st May 2010, 12:48 pm   #46
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Default Re: Pye v4

I decided to put a new EY51 in just to be sure and the heater is visible now and I can draw a nice cracking spark from the EHT end of the EY51. Pin 11 on CRT still down but a tad up at 137V.

PL81 Pin2 coupling is that C53 27pF ?

I'm having trouble figuring the boost cap from the schematic is it C57? if it is, it's a hard Hunts Brown plastic affair and is fractured in all directions, 0.05uF. I only found this by rolling it around as it was hiiden beneath.

if not then I still need to find the boost cap, but i think this might need changing at some point
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Old 1st May 2010, 2:21 pm   #47
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Default Re: Pye v4

changed C57, 0.5 (not .05 as I previously typed) looking at the schematic one end of the cap goes to T2 the other ends up on C56 then the CRT

CRT readings now

pin2 85V
pin10 142V

Up on the last readings but not enough, going in the right direction.

Check C56 I guess

Chris

Last edited by oldticktock; 1st May 2010 at 2:31 pm.
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Old 1st May 2010, 2:46 pm   #48
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Default Re: Pye v4

Changed C56 and CRT now reads

pin2 100V
pin10 150v

Hmm now what, 50V adrift from the minimum

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Old 1st May 2010, 3:22 pm   #49
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Default Re: Pye v4

I don't have the circuit but keep working through the capacitors in the line output one by one as those Hunts will all be u/s. Might be an idea to measure the boost voltage.

I have to admit to not having had a go at a 405 set but the fantastic results you are getting has me very tempted to splash out on an aurora.
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Old 1st May 2010, 5:06 pm   #50
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Default Re: Pye v4

Changed a couple of more Hunts in L/O stage C55 and C100

CRT
Pin2 96V
pin10 125V

Hmmm
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Old 1st May 2010, 8:20 pm   #51
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Default Re: Pye v4

CRT
Pin2 110V
pin10 157V although after a while drops to 134V

caps changed so far are C55,C56,C57,C62,C86,C100

line whistle is present

Think I will stop here and pickup tomorrow.

final check on pin11 126V so something is pulling it down
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Old 1st May 2010, 8:36 pm   #52
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Default Re: Pye v4

Hi OTT.
With these voltages you really should have some form of raster! The reduction of of the voltages you are getting when warm sounds like LOPT saturation due to damp ingress.
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Old 1st May 2010, 8:41 pm   #53
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Check the HT and boost rail, could be tired rectifier.
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Old 1st May 2010, 8:57 pm   #54
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Default Re: Pye v4

OTT just does not know when to stop.......

Ahh Ha, moved ION trap back towards plug and I have Line collapse not a lot of brightness but at least the baby is talking to me, a single vertical line.

Line collapse, the opposite of what I had on the TV62, that was frame collapse. So I guess I start looking in the Line Osc circuit, need to address that poor brightness as well

Now I am quiting for tonight a long day but a result nonetheless moderate success, I am for today content

Chris

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Old 1st May 2010, 9:44 pm   #55
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Default Re: Pye v4

Line collapse is rare. It is very unlikely to be the Line Oscillator, as you obviously have got EHT.

Check the line coils on the set and the wiring to the LOPT, and maybe around the width control.

I hope the scanning coils weren't damaged when the set was dropped.

Cheers,

Steve P.
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Old 1st May 2010, 9:46 pm   #56
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Default Re: Pye v4

Hi Chris, if you have line collapse... just a vertical line... then the line oscillator must be running, otherwise you'd have no EHT and no display at all.
It could be that you have a broken connection in the scan coil circuits, not impossible considering you've had to replace the crt: I'd check the scan coil wiring and continuity first.

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Last edited by DangerMan; 1st May 2010 at 9:48 pm. Reason: Beaten to it again...
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Old 1st May 2010, 9:51 pm   #57
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Default Re: Pye v4

Hi.
The scan coils are a well known problem in these sets, check the windings for continuity first before anything else.
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Old 1st May 2010, 10:32 pm   #58
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Default Re: Pye v4

Hi,
just a daft question here, have you put the scan coils back on the right way? I've just looked through your pictures and saw something sticking out of the top of the can with the scan coils in (picture centering control??) that was in the first pictures, but I can't see it on the ones after you changed the tube! maybe it is frame colapse, but with the coils on the wrong way it looks like line collapse?!
just thought I'd mention it, I've done it myself a few times

regards,
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Old 1st May 2010, 10:41 pm   #59
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Default Re: Pye v4

Lloyd I think that's a distinct possibility. Looking at the line it has a wide bright section about 7mm to the left of it there is a band of about 60mm that is like a squashed raster with lines wiggling. I will check my photos and refit tomorrow.

Another development the PL81 orginal started clicking fizzing with lights off it had a blue glow around its waist. I replaced it with a brand new PL81, started to do the same, this is a new development.

p.s.

just checked and well spotted Lloyd the scan coil housing is 90 degrees to the right of where it should be need to rotate and that would mean frame collaspe. I'm such a twonk.

Last edited by oldticktock; 1st May 2010 at 10:46 pm.
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Old 1st May 2010, 11:00 pm   #60
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Default Re: Pye v4

Hi Cris,
To determine which timebase is making the on screen line try adjusting the line and frame hold controls. Adjustment of these controls will result in the line varying slightly. If it is the frame timebase the line will become more flickery when the timebase frequency is lowered. Also the height control could be adjusted.
I agree with Lloyd, it's more likely the scan coils have been turned round 90 degrees.
According to the Pye circuit diagram the CRT A1 (pin10) is connected to the boost supply though a 10Megohm resistor. C106 is the boost capacitor.

DFWB.
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