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Old 3rd Aug 2009, 4:11 pm   #81
anthonys radios
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Default 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 !
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Old 3rd Aug 2009, 4:15 pm   #82
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Default Re: Ekco T161

Quote:
I would recommend using the original type valve.
I would agree, so long as the set hasn't been modified to take a diferent valve. The wiring to the base needs to be checked against the circuit and if necessary rewired to original condition.
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Old 3rd Aug 2009, 4:45 pm   #83
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Default 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.
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Old 3rd Aug 2009, 4:46 pm   #84
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Default 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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Old 3rd Aug 2009, 5:00 pm   #85
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Default 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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Old 3rd Aug 2009, 5:09 pm   #86
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Default Re: Ekco T161

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Originally Posted by Station X View Post
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.
Aha! It's begining to make sense!

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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Old 3rd Aug 2009, 5:13 pm   #87
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Default 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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Old 3rd Aug 2009, 5:16 pm   #88
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Default Re: Ekco T161

R113 and R114 is missing
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Old 3rd Aug 2009, 5:33 pm   #89
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Default 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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Old 3rd Aug 2009, 5:40 pm   #90
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Default 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.
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Old 3rd Aug 2009, 5:41 pm   #91
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Default 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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Old 3rd Aug 2009, 5:47 pm   #92
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Default 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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Old 3rd Aug 2009, 5:49 pm   #93
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Default 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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Old 3rd Aug 2009, 5:54 pm   #94
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Default Re: Ekco T161

Quote:
Originally Posted by ppppenguin View Post
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.
Now that what i was going to ask.. I have a PZ30 sitting in my TS88.. will it be a big job to rewire...?
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Old 3rd Aug 2009, 6:11 pm   #95
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Default 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.
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Old 3rd Aug 2009, 6:33 pm   #96
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Default 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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Old 3rd Aug 2009, 6:34 pm   #97
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Default Re: Ekco T161

Quote:
Originally Posted by idlerbiker View Post
Well I've ordered a u801 valve from Mark Hindes Site (thanks to David)
And Colin..
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Old 3rd Aug 2009, 6:45 pm   #98
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Default Re: Ekco T161

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Originally Posted by idlerbiker View Post
The 6x5 valve pin 3 and 5 are connected to the mains dropper and 8 is connected to C74
CORRECTION: 3 and 5 are connected to LOPT
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Old 3rd Aug 2009, 6:55 pm   #99
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Default Re: Ekco T161

Can i ask, is the Mains dropper part of the heater chain?
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Old 3rd Aug 2009, 6:56 pm   #100
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Default Re: Ekco T161

I think i can do this one alone now
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