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3rd Aug 2009, 4:11 pm | #81 |
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Re: Ekco T161
The U801 has an 80 volt 0.2 heater, as against the 6.3 volt 0.6amp heater for the 6X5.
The 6X5 is a double diode HT rectifier rated at 210 mA. The U801 is a quad diode rated at 300mA . So there is quite a difference between them, also the pinout is different of course. Sometimes the second set of diodes performed entirely different functions, so if absent, could be another problem to solve ! I would recommend using the original type valve. As to reliability in service, the 6X5 was excellent when used as an HT rectifier in radios, but the demands on the valve were low of course. The U801 was stressed more in use of course, but I still think they were reliable, lasting several years under hard working conditions. So I would say it is almost impossible to directly compare their reliability. Now say PL81 or PY81 they were for ever being changed ! |
3rd Aug 2009, 4:15 pm | #82 | |
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Re: Ekco T161
Quote:
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3rd Aug 2009, 4:45 pm | #83 |
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Re: Ekco T161
This pages notes that the 6X5 is also rated for high voltage pulse duty:
http://www.r-type.org/exhib/aad0070.htm Maybe it goes like this, a possible case of make do and mend.... U801 fails, no spare available, so repairman uses silcon diode for HT and 6X5G for efficiency diode. |
3rd Aug 2009, 4:46 pm | #84 |
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Re: Ekco T161
That what I'm intending to find out this evening. The heater is correctly wired up....
But it appears on the site details that the 6x5 isn't high enough for the LOPT
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3rd Aug 2009, 5:00 pm | #85 |
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Re: Ekco T161
If by "correctly wired up" you mean it's part of a series heater chain, then a 6X5 won't work as it has a 6.3V heater compared to 80V for the U801.
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3rd Aug 2009, 5:09 pm | #86 | |
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Re: Ekco T161
Quote:
The two transformers are 6.3v each. I'm guessing one failed to work or somehow and another was installed. The only use out of those transformers is for the 6x5GT Valve heater. So they will have to be removed.
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3rd Aug 2009, 5:13 pm | #87 |
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Re: Ekco T161
The 6x5 valve pin 3 and 5 are connected to the mains dropper and 8 is connected to C74
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3rd Aug 2009, 5:16 pm | #88 |
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Re: Ekco T161
R113 and R114 is missing
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3rd Aug 2009, 5:33 pm | #89 |
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Re: Ekco T161
Where do pins 2 and 7 (the heater pins) go to. Are they connected in series with the heater chain or to a transformer?
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3rd Aug 2009, 5:40 pm | #90 |
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Re: Ekco T161
If our assumptions are correct about using a 6X5 as a bodge replacement are correct I wonder what was done about the excess 80V in the 0.2A heater chain. That would be a chunky resistor (400R, 16W) which would be hard to hide. Unless they really bodged it and heavily overran the other heaters.
R113, R114 are not very critical. There should be a surge limiter in series with the silicon HT rectifier. 100R should be OK but if they were bodging that heavily it may have been omitted. This would give rather high HT and stress various other parts but it would still work. |
3rd Aug 2009, 5:41 pm | #91 |
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Re: Ekco T161
To the Transformer on the top of the chassis.
See photo. [IMG]http://farm4.static.***********/3498/3784925759_a730f9a7df_o.jpg[/IMG] [IMG]http://farm4.static.***********/3582/3784925873_efccdc7c1a_o.jpg[/IMG] Forgive me for the quality, my camera just died on me. Re: Rewiring the V9 to the LOPT, which part of the LOPT?
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3rd Aug 2009, 5:47 pm | #92 |
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Re: Ekco T161
Well, the phantom bodger has certainly been visiting. Seems like a very long winded way to get round finding a U801. Could have used a common boost diode such as U191 or even a PY81. Heater wired in series with V16 though that would have thrown the 0.1A heater chain a bit. PZ30 might have been another choice.
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3rd Aug 2009, 5:49 pm | #93 |
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Re: Ekco T161
Ok i don't know if I mentioned this before but v17 20L1 is replaced with CV491
And V12 10f1 is replaced with CV138..
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3rd Aug 2009, 5:54 pm | #94 | |
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Re: Ekco T161
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3rd Aug 2009, 6:11 pm | #95 |
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Re: Ekco T161
CV491 is electrically fairly similar to 20F1 but the base is different.
10F1 and CV138 (effectively an EF91) are pretty close too but bases are different and heater requirements are different too (100m and 300mA). Do yourself a favour and download TDSL personal edition. It's a huge valve resource. It's where many of us go to find out about valves and equivalents. http://tdsl.duncanamps.com/ As for using a PZ30 I'm sure we could work out a way to get it to work but getting the heater chain currents right will be tricky. The phantom bodger has been pretty serious with this set. You've found a tough one to tackle for your first TV. There's going to be bodgery all over the place. |
3rd Aug 2009, 6:33 pm | #96 |
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Re: Ekco T161
Well I've ordered a u801 valve from Mark Hindes Site (thanks to David)
I'll leave the other two valves alone until I get this U801, (I just want to be certain the CRT is working) I feel like handing the set over to an expert..
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3rd Aug 2009, 6:34 pm | #97 |
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Re: Ekco T161
And Colin..
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3rd Aug 2009, 6:45 pm | #98 |
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Re: Ekco T161
CORRECTION: 3 and 5 are connected to LOPT
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3rd Aug 2009, 6:55 pm | #99 |
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Re: Ekco T161
Can i ask, is the Mains dropper part of the heater chain?
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3rd Aug 2009, 6:56 pm | #100 |
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Re: Ekco T161
I think i can do this one alone now
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