• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

is 6X5 a 6X4 in an octal form?

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diyAudio Senior Member
Joined 2002
Hi,

Well you first mentioned the value 1ohm 10W resistor. Why can't I use 2ohm 5W in parallel?

It was just an imaginary value, if you need, say 10W of dissipation capability and can only get 5W resisistors you can put twice the target Ohmic value in //.

For example, in a give diagram it says 100R 10W but the shop carries nothing heavier than 5W resistors, you can now buy 2 200Ohm/5W resistors and put them in //.

Once paralelled the ressitor you now created will be a 100R/10W.

This is true for all values and wattages as long as you use equal values and wattages.

Hi Tim,

YES. In fact they often use the exact same electrode structures.

Could be but shouldn't be.

Cheers,;)
 
using the original circuit but with a 6X5GT, duncan's tool prompts a message saying "rectifier IFRM os .24A has been exceeded with a value of .25A at time xxxx seconds."

Is that a bad thing?

With your suggestion Frank, this message is not displayed which I guess is a good thing. :)

Changing the capacitors C1 and C2 in the original circuit to 8uF and 10uF respectively removes the prompt. Though this means I have to buy 2 more capacitors. :)
 
diyAudio Senior Member
Joined 2002
Hi,

I guess that a bad thing.

Not necesarilly...I don't trust those proggies anyway.
You may need to increase the response delay or something, someone may be explain what happens, I work the old fashioned way.
Mista calculata, you know...

With your suggestion Frank, this message is not displayed which I guess is a good thing.

It better...;) Which is why I don't trust those in the first place...

Just kidding.;)

Though this means I have to buy 2 more capacitors.

No, you don't...unless you absolutely want to.

Cheers,;)
 
diyAudio Senior Member
Joined 2002
Hi,

care to explain how to use calculator/pen and paper in computer current/voltage for the circuit?

Oh dear, actually no calculator insight..I just know what I'm on about.

I don't want to sound presumptious but this is NOT something you acquire overnight.

After twenty years it just becomes second nature, you look at a circuit and spot the mistakes..where corners have been cut and so on.

I'm sure some other members feel the same way, it doesn't mean anything really just alot of field experience.

As said before, Ohms' law is a darn good place to start.

All the best,;)
 
Hi

According to the data sheet for 6X4 and also for other similar rectifiers it is advised to use a min value of resistance of several 100s ohms in order to limit the peak current when using a cap input filter, the resistance in this case is the transformer winding resistance + eventual serial resistors before the first cap, values for 6X4 is mentioned as 500 ohms typical. If a series resistance like this is used and if the value is high enough the input cap value is not so important as the resistance will limit peak current to a safe value.

See rating chart 3 in this pdf file http://www.mif.pg.gda.pl/homepages/frank/sheets/093/6/6X4.pdf

BTW, according to the RCA tube databook they refer to 6X4 for typical data for the 6x5...

Regards Hans
 
diyAudio Senior Member
Joined 2002
Hi,

BTW, according to the RCA tube databook they refer to 6X4 for typical data for the 6x5...

In historical order we had octals, than novals, than pico 7s as we call them amongst other formats.

So, logically the 6X4 was born out of the 6X5, right?

Which is probably what you meant anyway?

To me, the 6X4 is the 6X5s' little nephew, isn't it?

Cheers,;)
 
Ex-Moderator
Joined 2003
Showing your age...

Some time ago, I was surprised to read that B7G (miniature 7-pin base) pre-dated B9A (9-pin base), and that B7G was quite an early base. To give a feel for this, 5842 used a B9A base in the late 40s. Sadly, I didn't make a note of the reference. Anyway, to me, it seems more logical that 6X5 came after 6X4, but does anyone have concrete proof?
 
Which is probably what you meant anyway?

No, not really just that the RCA databook refer to 6X4 for data of 6X5, (general and maximum ratings). This was just a comment to what you wrote earlier as an answer if 6X5 is an octal version of 6X4.

No, not really. While you can use a 6X5 to replace a 6X4, the inverse procedure could lead to problems in some situations.

However I can imagine that the 6X5 could be a bit stronger then a 6X4 in reality but it is interesting to note that even manufacturers give the same spec for both.

Regards Hans
 
diyAudio Senior Member
Joined 2002
Hi,

Anyway, to me, it seems more logical that 6X5 came after 6X4, but does anyone have concrete proof?

IMHO, the octal types came first.

See "70 Years of Radio Tubes and Valves" by John W. Stokes: octal based valves were introduced in August 1935.

I don't know for certain about the 6X5 but it would come as a surprise to me if the 6X4 preceded it.

Need to dash now but I'll look into it later.

Cheers,;)
 
diyAudio Senior Member
Joined 2002
Hi Hans,

However I can imagine that the 6X5 could be a bit stronger then a 6X4 in reality but it is interesting to note that even manufacturers give the same spec for both.

My datasheets tell me the 6X5 to be a little more sturdy than it's 6X4 nephew which led to my comment saying that a 6X4 can be replaced by a 6X5 without problem but not necessarilly the other way 'round.

Cheers,;)
 
I still think it is worth checking the reservoir cap if you are going to use a 6X5 in place of a 6X4 - checking the specs I have by manufacturer, generally speaking (and I admit it is a generalisation - some manufacturers put of a top limit of 4uf, others 32uf!) the 6X5 requires a lower value cap than a 6X4. Certainly the old valve radios I come across time to time which use 6X5s do not feed them into a reservoir cap of more than 8uf.
 
Hi

You can safely use a cap input filter if the transformer together with the series resistor before the first cap is large enough, that is applicable especially in this case as the application is a preamp as I understand. With a series resistor of more then 500 ohm, say 1kohm the max peak current can never be exceeded even if the input cap is quite large. Max peak current can be simulated using PSUD SW.

In an old tube radio it is quite different as the series resistance in these didnt reach these values and it was therefore adviseable to use low values for the first cap.

Regards Hans
 
Re: Showing your age...

EC8010 said:
Some time ago, I was surprised to read that B7G (miniature 7-pin base) pre-dated B9A (9-pin base), and that B7G was quite an early base. To give a feel for this, 5842 used a B9A base in the late 40s.

Yes. I have the both the 1940 and 1947 editions of the RCA tube manual, and the difference between the two is dramatic. By 1947, you essentially have "modern" tubes and circuits, all because of WWII.
 
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