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Sets, Parts and Service Information Wanted (private buyers only, no swaps) If you need help obtaining components, sets or equipment, post a message here. Private buyers only - no traders. No swaps.

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Old 13th Sep 2017, 1:38 pm   #1
Pete_kaye
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Default 6BE6 = EK90 valve.

For a KB toaster, preferably tested in a set as stable.
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Old 13th Sep 2017, 2:20 pm   #2
Boater Sam
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Default Re: 6be6= ek90

That should read EH90 I think as they are equivalent to 6BE6?

I asume that you need one or the other for you KB? Brevity is fine but leaves us guessing!
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Old 13th Sep 2017, 3:02 pm   #3
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Default Re: 6be6= ek90

It used the 6BE6. All the KB sets of that era used American types from Brimar. I have several pulls, but no way of testing them properly.
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Old 13th Sep 2017, 3:56 pm   #4
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Default Re: 6be6= ek90

According to the valve museum 6BE6 eq is an EK90.

http://www.r-type.org/exhib/aaa0011.htm

EH90 eq is 6CS6

http://www.r-type.org/exhib/aaa1272.htm
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Old 15th Sep 2017, 3:12 pm   #5
Pete_kaye
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Default Re: 6be6= ek90

I did research it first and EH90 is not an equivalent! EK90 is.
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Old 15th Sep 2017, 4:02 pm   #6
Boater Sam
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Default Re: 6be6= ek90

Sorry, never heard of an EK90, found the equivalent to be EH90, erroneously, from an old forum thread.
What does the "K" signify in the Mullard code please?
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Old 15th Sep 2017, 4:20 pm   #7
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Default Re: 6be6= ek90

I think K= hexode, H=heptode (or is it the other way round?)
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Old 15th Sep 2017, 4:51 pm   #8
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Default Re: 6be6= ek90

The valve data (Nation Valve Museum) says both types are heptodes, there is a conversion gain reduction figure given for the EK90 for -ve 30 volts on g1 which suggests AGC permitted.

Nothing like that on the EH90 data sheet from the same source.

So I guess the second letter K is a vari mu pentagrid mixer/osc.

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Old 15th Sep 2017, 6:40 pm   #9
dodgy-dxer
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Default Re: 6be6= ek90

6BE6 used in many 70's era amateur sets: Drake, Hammerlund, KW, Yaesu, Eddystone so should be "findable"

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Old 15th Sep 2017, 6:58 pm   #10
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Default Re: 6be6= ek90

It's a standard American domestic radio valve. European radios mostly used a triode-hexode like an ECH81 in the frequency changer position, which is why the EK90 is little known and rare.
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Old 15th Sep 2017, 7:06 pm   #11
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Default Re: 6be6= ek90

ECH81 is a triode heptode, ECH41, ECH42 were triode hexodes, The triode heptode was usually sliding screen voltage, triode hexodes tended to use a more stabilized screen voltage (potential divider or other means) because of the lack of a suppressor grid.

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Old 15th Sep 2017, 10:49 pm   #12
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Default Re: 6be6= ek90

I seem to remember that the local oscillator coil has to have a tap and is in the cathode of the frequency changer. I actually built a set using the EK90 as the frequency changer and the local osc was a bit temperamental, but I was using home made coils so not surprising. I think I borrowed the circuit from a commercial design. Is the pin out the same for the EH and EK90? I think (and it was a long time ago) I tried swapping the valves and it didn't make much difference to the performance. Is the EH90 not described as a TV sync sep or something odd like that. At the time I did a little research, but can't recall it now.
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Old 15th Sep 2017, 11:36 pm   #13
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Default Re: 6be6= ek90

I think the EH90 was designed for TV use, though I can't remember what for now. The EK90 was just the Pro-Electron designation for the 6BE6, much as Rimlock valves had American designations but were never used there. It's certainly a bit odd that American manufacturers use pentagrids exclusively, whereas Europeans used triode-hexodes/heptodes, at least once the BVA rules were relaxed.
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Old 15th Sep 2017, 11:50 pm   #14
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Default Re: 6be6= ek90

Quote:
Originally Posted by paulsherwin View Post
I think the EH90 was designed for TV use, though I can't remember what for now.
Yes indeed, the EH90 was intended for use as a locked oscillator FM discriminator for the intercarrier sound system. It could double as an audio pre-amplifier on 405 lines in dual standard sets.

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Old 16th Sep 2017, 4:01 am   #15
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Default Re: 6be6= ek90

Quote:
Originally Posted by paulsherwin View Post
I think K= hexode, H=heptode (or is it the other way round?)
Other way round -- sort of...

I believe :

H = hexode or heptode designed for a separate local oscillator

K = heptode or octode with a 'phantom cathode' local oscillator section.


In general a 'K' can be used as a frequency changer on its own, an 'H' needs a 'C' (triode) as well.
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Old 16th Sep 2017, 5:05 am   #16
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Default Re: 6be6= ek90

pete I can help with one of these,

Ken
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Old 16th Sep 2017, 10:46 am   #17
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Default Re: 6be6= ek90

Something a Pentagrid converter does that normally would be classed as a problem was to pull the LO on strong stations. This effect could be used to make the set easier to tune and hold the LO on frequency. The radio would also require less effort in the design of the LO section.
A good write up on this web page although there is a caveat about requiring more citations.
https://www.isnare.com/encyclopedia/Pentagrid_converter
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Old 17th Sep 2017, 5:17 am   #18
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Default Re: 6be6= ek90

If you can't find a good 6BE6, let me know. I have a lot of them. Yours for the postage.

"A heptode is a really freaked out frog" Anon.
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Old 17th Sep 2017, 7:09 am   #19
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Default Re: 6be6= ek90

6BE6 is available from the usual valve stockists. Langrex currently have 702 listed! They are also available from various sources on eBay
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Old 17th Sep 2017, 10:06 am   #20
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Default Re: 6be6= ek90

They were the standard American frequency changer after 1950 or so, comparable to the ECH81 in Europe. They are found in practically all radios with AM coverage. They also last well, so there are huge numbers of NOS and pulls around, especially in the US. In Britain KB used them as part of their policy of using Brimar valves.
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