heh I have a question again. 
I was doing some reading on Frank's website and I found some inconsistencies with the heater requirements of the 6DJ8 family (including 6922 and 7308).
Well I plan to tube roll but 6DJ8 and 6922 have different heater current ratings. 6DJ8 has a current rating of 365mA as you mentioned. 6922 has a current rating of 300mA. 7308 has a 335m
A current rating.
Should I spec the fuse based on the 6DJ8 or 6922 or 7308?
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Let's say the total current requirement for the whole circuit is:
2.349A = 54mA (for the amp) + 1.2A (for 5852) + 3x 365mA (for 6DJ8).
should I get a 2A slow-blow or 2.5 slow-blow?
Thanks again.
I was doing some reading on Frank's website and I found some inconsistencies with the heater requirements of the 6DJ8 family (including 6922 and 7308).Well I plan to tube roll but 6DJ8 and 6922 have different heater current ratings. 6DJ8 has a current rating of 365mA as you mentioned. 6922 has a current rating of 300mA. 7308 has a 335m
A current rating.
Should I spec the fuse based on the 6DJ8 or 6922 or 7308?
--------------
Let's say the total current requirement for the whole circuit is:
2.349A = 54mA (for the amp) + 1.2A (for 5852) + 3x 365mA (for 6DJ8).
should I get a 2A slow-blow or 2.5 slow-blow?
Thanks again.
Hi,
At 2.35A you better go for a 2.5A fuse.
In an ideal world one would have to change the fuse according to what tube is used to be on the safe side.
BTW, there are also the Russian 6N1P-EB/6H1P-EV at 600 mA heater current that you may want to try.
They'll all work provided the heater winding of the powerxformer is up to it, in the case of the 6N1P : 3*600 mA + 1.2 A = 3A
The slo-blo fuse will act on a fault condition such as a short.
Eventually it will melt on overcurrent as well, it will just take a little longer.
Hope this helps,
P.S. For the 6DJ8/ECC88 heater current varies from 300mA to 365mA depending on the brand.
At 2.35A you better go for a 2.5A fuse.
In an ideal world one would have to change the fuse according to what tube is used to be on the safe side.
BTW, there are also the Russian 6N1P-EB/6H1P-EV at 600 mA heater current that you may want to try.
They'll all work provided the heater winding of the powerxformer is up to it, in the case of the 6N1P : 3*600 mA + 1.2 A = 3A
The slo-blo fuse will act on a fault condition such as a short.
Eventually it will melt on overcurrent as well, it will just take a little longer.
Hope this helps,
P.S. For the 6DJ8/ECC88 heater current varies from 300mA to 365mA depending on the brand.
Hi,
That would be correct if the 2.5A were consumed at 240VAC which they aren't.
I forgot about that completely but the fuse, when put on the primary side needs to be derated.
Luckily for us the powerconsumption seen by the powermeter is transformed back by our power transformer ratios.
So, if we assume our heater supply runs at 6.3 V and consume 2.5 A it will consume: V*I= 6.3*2.5 = 15.75 W.
You need to do the same for the rest of the circuit and than we need to find out what it looks like seen from the primary side.
It's been ages since I've done that kind of thing but I'll see if I can dig it up somehow.
Cheers,
That would be correct if the 2.5A were consumed at 240VAC which they aren't.
I forgot about that completely but the fuse, when put on the primary side needs to be derated.
Luckily for us the powerconsumption seen by the powermeter is transformed back by our power transformer ratios.
So, if we assume our heater supply runs at 6.3 V and consume 2.5 A it will consume: V*I= 6.3*2.5 = 15.75 W.
You need to do the same for the rest of the circuit and than we need to find out what it looks like seen from the primary side.
It's been ages since I've done that kind of thing but I'll see if I can dig it up somehow.
Cheers,
Hi,
Using the above as an example:
Current (Amps) = Power (Watts)/Voltage (volts)
I = 15.75 W / 240V
I = 0.06666 A
Allowing some margin for inrush current at switch on, a 0.1 A slo-blo should do the trick IMHO.
So all that's left to do is calculate the total powerconsumption of the preamp, convert that back into amperes, allow some margin ( I've read upto 167%, don't know if this is correct) and off you go.
Hope this helps,
Using the above as an example:
Current (Amps) = Power (Watts)/Voltage (volts)
I = 15.75 W / 240V
I = 0.06666 A
Allowing some margin for inrush current at switch on, a 0.1 A slo-blo should do the trick IMHO.
So all that's left to do is calculate the total powerconsumption of the preamp, convert that back into amperes, allow some margin ( I've read upto 167%, don't know if this is correct) and off you go.
Hope this helps,
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