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-   -   is 6X5 a 6X4 in an octal form? (http://www.diyaudio.com/forums/tubes-valves/16808-6x5-6x4-octal-form.html)

jarthel 22nd June 2003 12:52 PM

is 6X5 a 6X4 in an octal form?
 
as title. Thank you.

Jayel

fdegrove 22nd June 2003 01:19 PM

Hi,

No, not really.

While you can use a 6X5 to replace a 6X4, the inverse procedure could lead to problems in some situations.

Cheers,;)

jarthel 22nd June 2003 01:32 PM

well the circuit calls for a 6X4, so using a 6X5 will be alright. right?

thanks

jayel

fdegrove 22nd June 2003 01:40 PM

Hi,

Yes, it will.

Happy building,;)

bournville 22nd June 2003 01:55 PM

Well, if you are going to use a 6X5 in place of a 6X4, although both valves can handle the same HT current and voltage, you should check the reservoir capacitor. A 6X4 can have up to 40uf, but a 6X5 can only have 8uf, so adapt the circuit if necessary.

If you do have to change the reservoir cap, then the HT voltage under load may change slightly also. I would recommend not to exceed the 6X5's max reservoir rating. In the past the 6X5 was widely used over here as rectifiers in '40s and '50s valve radios, and I've come across several over the years in which the rectifier failed, in one case shorting out the mains transformer and causing a fire inside the set, and the one thing in common with these sets is that someone at some time had replaced the reservoir cap with one of a much higher value!

jarthel 22nd June 2003 02:16 PM

I'm not exactly going to use 6X5 but a 6X5GT. I looked into the datasheets I downloaded from Frank's. I can't find any mentioned
of 40uF for the 6X4.

I found a spec called "Capacitor input filter". It mentioned 20uf for the 6X4 and 4uf for the 6X5GT.

I really don't understand much how reservoir capacitor works so
if you could help me modified this circuit (http://home.swbell.net/acavalli/imag...r_Supply_2.gif) to suit a 6X5GT, I would be most grateful.

Thanks

jayel

fdegrove 22nd June 2003 02:32 PM

Hi Alex,

This is the PSU for a 6DJ8 preamp right?

Anyway, you can use an LC filter instead of the CLC filter you now show.

Suppress the first 100 uF cap... you can put it behind the self if you like...
The 470K R you can put across the last cap where it will serve as a bleeder.

The 100 Ohm resistor can be removed as well, the circuit will have a slow start as it is already.

The 2K2 resistor inbetween the two filter caps may need revision according to the B+ you get.

BTW, are you out the woods yet with the 6DJ8 preamp yet?
I notice you will be using three of them...

Which brings me to the heater supply, if left as shown now you'll be feed the 6.3 V heaters with roughly 8 VDC which way too much.
The "optional" resistor will be required and will need to go up in value to bring the voltage down.
Keep in mind to use one of appropriate wattage for it's going to dissipate close to 10W.

Cheers, ;)

bournville 22nd June 2003 03:09 PM

Jayal,

I can understand the confusion over reservoir caps - it is not helped by different manufacturers giving different specifications. I have the specs for several thousand valves by different manufacturers, and, for example, Mullard quote 16uf for the reservoir cap of a 6X5GT whilst Tungsram quote 4uf, Cossor quote 8uf and Brimar 32uf! Mullard quote 16uf for a 6X5, but Brimar quote 40uf!

To play it safe it might be wise to veer towards the lower values in your power supply. In the old valve sets I mentioned which used a 6X5(GT) a 8uf was common for a reservoir cap and 16uf for the smoothing cap after a choke.

jarthel 22nd June 2003 03:26 PM

Quote:

Originally posted by bournville
Jayal,

I can understand the confusion over reservoir caps - it is not helped by different manufacturers giving different specifications. I have the specs for several thousand valves by different manufacturers, and, for example, Mullard quote 16uf for the reservoir cap of a 6X5GT whilst Tungsram quote 4uf, Cossor quote 8uf and Brimar 32uf! Mullard quote 16uf for a 6X5, but Brimar quote 40uf!

To play it safe it might be wise to veer towards the lower values in your power supply. In the old valve sets I mentioned which used a 6X5(GT) a 8uf was common for a reservoir cap and 16uf for the smoothing cap after a choke.

To be honest I have no concept of reservoir caps. :(

In the circuit I posted, is there any change I need to make to accomodate an 6X5GT?

Thanks

jayel

jarthel 22nd June 2003 03:31 PM

Quote:

Originally posted by fdegrove

Which brings me to the heater supply, if left as shown now you'll be feed the 6.3 V heaters with roughly 8 VDC which way too much.
The "optional" resistor will be required and will need to go up in value to bring the voltage down.
Keep in mind to use one of appropriate wattage for it's going to dissipate close to 10W.

well duncan PS simulator gives a value that ranges from 3.5 to 7.3V. But I'll definitely check voltage first with VOM. :)

Regarding the 10W resistor. Well the max I can find locally is a 5W ceramic resistor. good enough?

Thank you

jayel


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