3rd May 2010, 4:47 pm | #141 |
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Re: Pye v4
Hi Cris,
Is the CRT heater lit? Can you get a good spark at the cathode end of the EY51? Confirm that by the earthed screwdriver test. Spark should be about 10 to 12 mm long. That equates to about 10KV. DFWB. |
3rd May 2010, 4:48 pm | #142 |
Nonode
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Re: Pye v4
Hi
long rambling threads like this are interesting!! I have a few idea's.. turn off the set, unplug the crt and power its heater from a bench psu see how much current it draws. this should show up any shorts or partial shorts on its heater (hopefully it'll be fine!) also, is there any heater chain decoupling caps anywhere? if one goes short then one or more of the heater chain will not light. regards, Lloyd. |
3rd May 2010, 4:53 pm | #143 |
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Re: Pye v4
Hi David,
Yes CRT heater lit Yes healthy 12cm Yellow spark from EY51 cathode end |
3rd May 2010, 4:54 pm | #144 | |
Heptode
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Re: Pye v4
Quote:
Plus you're a real inspiration mate! Just a thought though, as the tube's been replaced, is the grounding connection to the aquadag coating sound? Greg
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3rd May 2010, 4:58 pm | #145 |
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Re: Pye v4
Hi Lloyd,
Thanks for the ideas, I do not have a bench power supply. All the valves heaters are lit nicely the two ecc82's are dimmer than the rest but i put that down to ecc82 characteristics as it would be a bit of a coincidence. There are lots of TCC and Hunts looking sorry for themselves but I have avoided changing them as I'm trying to follow John W's advice and If I start changing them at random then He's quite likely to throw some object at me from down south Hi Greg, Yes the grounding via two copper springs are making good contact with the aquadag. Chris |
3rd May 2010, 4:58 pm | #146 |
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Re: Pye v4
Hi Lloyd,
There could be a possibility that the CRT has a partial shorted heater, a common fault with Mullard tubes which is fact what the Teletronic tube is. Even under that condition 3 volts should be apparant across pins 1 and 12. A 6.3 volt heater transformer could be considered. The CRT heater would then be taken out of the heater chain. DFWB. |
3rd May 2010, 5:03 pm | #147 |
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Re: Pye v4
Hi Chris,
to follow from post 142, if you are worried about a partial heater short there is a much easier way of checking. Simply measure the voltage across the crt heater when the set has warmed up and all the heaters are fully lit. It should be 6.3v (AC) for a normal mullard tube. If it is significantly less than this there is likely to be a partial short, in which case the reading is likely to be more like a half of the correct value. Pete Doh! Beaten to it again ! Last edited by DangerMan; 3rd May 2010 at 5:04 pm. Reason: pipped with the post |
3rd May 2010, 5:04 pm | #148 |
Nonode
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Re: Pye v4
hmm... I would expect there to be some voltage there too, my style 70 had a shorted heater and I had to run its tube off a seperate transformer.
regards, Lloyd. |
3rd May 2010, 5:10 pm | #149 |
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Re: Pye v4
CRT
pin2 121V pin5 117V pin11 210V |
3rd May 2010, 5:11 pm | #150 | |
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Re: Pye v4
Quote:
Checked the brightness control circuit. It's a very simple affair consisting of a 25K pot and a 6.8K resistor to the HT line. So the voltage swing will be zero to about 140 volts. A cathode follower supplies video to the CRT cathode. The V4 was full of good stuff. Keep faith with the set. DFWB. |
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3rd May 2010, 5:17 pm | #151 |
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Re: Pye v4
Hi David I will try the Trap again but I have played with that baby for ages. See post #120 re brightness it never gets to 0.
Me and this PYE are seriously falling out |
3rd May 2010, 5:18 pm | #152 |
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Re: Pye v4
It is unlikely that millivolts on the heater would have given you a line even. I'd look very closely at the supply and measure the heater resistance and h-k insulation before condemning the tube.
Dave . |
3rd May 2010, 5:30 pm | #153 |
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Re: Pye v4
Hi Cris,
Are your component references from a Trader service sheet? I think they differ from the original Pye service manuals. For example, in the Pye service manual the circuit reference for the brightness control is R41. DFWB. |
3rd May 2010, 5:32 pm | #154 |
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Re: Pye v4
Heater resistance is 1.2R
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3rd May 2010, 5:33 pm | #155 |
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Re: Pye v4
Hi David yes i'm working from trader R65 is 25k pot R64 6.8k
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3rd May 2010, 5:34 pm | #156 |
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Re: Pye v4
We should check the CRT heater volts. If it is lit then it is not mV's. Try measuring again pin 1 to pin 12 with the meter on AC volts.
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3rd May 2010, 5:38 pm | #157 |
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Re: Pye v4
for all those that want to follow you can download the trader sheet I've uploaded it
http://www.oldticktocks.co.uk/v4.pdf |
3rd May 2010, 5:46 pm | #158 |
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Re: Pye v4
Hi Cris,
I'll print out your service sheets. Now we have common reference codes. DFWB. |
3rd May 2010, 5:50 pm | #159 |
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Re: Pye v4
Oh dear. I've just put a meter across a known good tube heater MW-Summit and got 3.3 Ohms so yours might well be shorting. At 1.2 Ohm though I'd expect 2V or so.
What tube is it? Some have different heaters. Dave |
3rd May 2010, 5:56 pm | #160 |
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Re: Pye v4
Mw36-24
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