Kel 84

[Ali Tait]

Anyone have the specs of the output trannies please?

[John Caswell]

Hi Ali,
Well I have had a look at the original article and as usual no info on the txs apart from saying the U/L taps are at 12%w which is quite low as generally 40-43% was reckoned as the best compromise.
I think the only way to find this out is to measure a tx to get some answers.
It is not difficult to do IF you have the tx. Proceed as follows.
With bare tx inject 10Vac into secondary and measure the across the primary anode to anode = say 200Vac.
Therefore turns ratio is 20:1.
So impedance ratio is turns ratio squared = 400:1.
That being the case for an 8R impedance secondary the primary will be 8 x 400 = 3200R a-a.
Obviously if it is an U/L type the you can measure the taps to calculate accordingly.
I don't have the details here in the office, but tomorrow I will look at what Mullard/GEC recommended and post it here. It will be a pretty close match I guess

John

[Ali Tait]

Thanks John, no worries, was just on the off chance someone had the specs.

[John Caswell]

Hi Ali et al,
Mullard recommend 3 variations on a theme:
Low loading - Pentode connection = 6K a-a
Normal loading Pentode connection = 8K a-a
Distributed loading = U/L 6K6 a-a with 20% taps OR
Distributed loading = U/L 8K a-a with 43%taps

Hope this helps

John

[Richard]

Hi Ali, John, all,

I have 8K 12.5% pencilled on my copy of the KEL84 supplement so will have found it from somewhere reliable.

Perhaps it was given in the HFW adverts circa 2001 when they used to sell the TXs separately. I don't have any old copies of the mag now to check though.

[John Caswell]

Hi Richard,
Well that's a result I will pencil it on my copy also.

Ta

John

[Ali Tait]

It is indeed, many thanks chaps.

[colin.hepburn]

Hi all
I may be able the check as I have Hi Fi World Mags in the loft from 1989/2001 or there about
Which I am thinking of dumping soon after scanning some articles
So I can check the Adds if you wish