Just to confuse the issue, in my own experience, which admittedly will be rather subjective, I have found that the loctal equivalent to the 6X4/5, the 7Y4, to be more reliable in operation than either of the two others, as well as having a slightly lower heater current.
What date is the 7Y4 Frank? About 1939-40?
What date is the 7Y4 Frank? About 1939-40?
Hi,
7Y4 1938.
Re: the 6X5;
it seems to have a bad rep due to often shorting out the heater to cathode insulation, which in turn tends to take out the powerxformer.
You'd better protect it with a fuse if you must use that valve.
I have no idea about the 7Y4 but it may well be improved over the 6X4/6X5.
Cheers,
7Y4 1938.
Re: the 6X5;
it seems to have a bad rep due to often shorting out the heater to cathode insulation, which in turn tends to take out the powerxformer.
You'd better protect it with a fuse if you must use that valve.
I have no idea about the 7Y4 but it may well be improved over the 6X4/6X5.
Cheers,
fdegrove said:
Here's the original circuit -->> http://home.swbell.net/acavalli/images/MJ_Power_Supply_2.gif. The 6X4 will be replaced of course by a 6X5GT.
For me to follow your suggestion, do you mean that I use a fuse in between yellow wire of Hammond xformer and pin3 of the 6X5?
or possibly all wires from Hammond going into pins 3 and 4 is connected to a fuse?
Thanks
jayel
--------
on a side note, after doing a search on google for the word "6X5", Audio Note seems to be using them on several of their amps.
HOLD ON...
Hi,
That resistor may be application specific, what it does is slowing down the inrush current on switch-on.
Not a bad thing to have as such.
I looked up the data for 6X4 and 6X5 and only for the 6X4 it says a total effective plate impedance of 525R/plate when a cap input type filter is used at 70mA current draw.
They probably specced this so one can "predict" voltage drop I assume.
Better put one (F-type) in series with each red wire of the xformer and use a fuse ( Slo-Blo type) on the primary side as well, as that would protect the entire circuit.
I'd like a second opinion on that from others since I based this on other peoples' experience, not my own.
Also, the heater to cathode insulation is 400V and shouldn't be exceeded under any circumstances.
Take note that the heater voltage should be as steady as possible...the way the Cavalli cicrcuit is shown there is zero regulation in place for the rectifier so if the powerline voltages soars it may very well be exceeded.
RCA gave a limit of 7.5VAC.
I don't know about the 5852, I'll see what I can find.
Cheers,
Hi,
That resistor may be application specific, what it does is slowing down the inrush current on switch-on.
Not a bad thing to have as such.
I looked up the data for 6X4 and 6X5 and only for the 6X4 it says a total effective plate impedance of 525R/plate when a cap input type filter is used at 70mA current draw.
They probably specced this so one can "predict" voltage drop I assume.
Better put one (F-type) in series with each red wire of the xformer and use a fuse ( Slo-Blo type) on the primary side as well, as that would protect the entire circuit.
I'd like a second opinion on that from others since I based this on other peoples' experience, not my own.
Also, the heater to cathode insulation is 400V and shouldn't be exceeded under any circumstances.
Take note that the heater voltage should be as steady as possible...the way the Cavalli cicrcuit is shown there is zero regulation in place for the rectifier so if the powerline voltages soars it may very well be exceeded.
RCA gave a limit of 7.5VAC.
I don't know about the 5852, I'll see what I can find.
Cheers,
Re: HOLD ON...
would you suggest I use one then?
sorry I meant the 6X5GT. It says 150 ohms per plate.
Is this an ftype fuse? -->> http://www.dse.com.au/cgi-bin/dse.storefront/3eff146f00080e0e273fc0a87f9c0671/Product/View/P7952
150mA F-type for the red wires and 200mA slow-blow for the primary be good enough? The mains here is 240V.
Would it better for me to place the heater of the rectifier after the diode bridge?
Thanks
Jayel
fdegrove said:
would you suggest I use one then?
sorry I meant the 6X5GT. It says 150 ohms per plate.
Is this an ftype fuse? -->> http://www.dse.com.au/cgi-bin/dse.storefront/3eff146f00080e0e273fc0a87f9c0671/Product/View/P7952
150mA F-type for the red wires and 200mA slow-blow for the primary be good enough? The mains here is 240V.
Would it better for me to place the heater of the rectifier after the diode bridge?
Thanks
Jayel
Thank you, Frank...
Good gracious, both 6X4 and 6X5 are older than I expected!
Mullard habitually gave charts showing minimum required series resistance from HT transformer centre-tap to each anode (to limit ripple current). RCA don't seem to (in my data sheets). Perhaps that is what the 150 Ohms refers to?
Good gracious, both 6X4 and 6X5 are older than I expected!
Mullard habitually gave charts showing minimum required series resistance from HT transformer centre-tap to each anode (to limit ripple current). RCA don't seem to (in my data sheets). Perhaps that is what the 150 Ohms refers to?
Hi,
I would and here's upshot: if I were to put the resistors in I'd dare to leave the fuses out on the secundary of the xformer as well.
My guestimate is that the 6X5 may suffer from overvoltage and current at switch on eventually killed it after a while, especially when the rectifier is pushed already.
Yes, I know but do you happen to know the company that publish that datasheet?
Not that this part is important to what you want to do, just me being curious to find out what it's about.
F-type are the fast-blow ones indeed.
If you're speccing for fuses you need to know the current draw of the entire circuit for the Slo-Blo fuse and the local current draw for the Fast-Blow ones.
Overspec them and they'll be useless, underspec them and they'll blow whenever they feel like it.
If the Hammond Xformer has some margin on current it will try to regulate the mains input and since the heater windings have a step down ratio with respect to mains you'll quite likely be fine.
So, unless you know the mains to vary beyond +/- 5% alot I'd leave it there.
To be on the safe side you can monitor voltages with a DVM for a week or so, that would tell you what's happening inside.
If however you decide one day to put it behind the bridge, make sure the bridge can handle the extra current demand and check the heater voltages again.
Cheers,
I would and here's upshot: if I were to put the resistors in I'd dare to leave the fuses out on the secundary of the xformer as well.
My guestimate is that the 6X5 may suffer from overvoltage and current at switch on eventually killed it after a while, especially when the rectifier is pushed already.
Yes, I know but do you happen to know the company that publish that datasheet?
Not that this part is important to what you want to do, just me being curious to find out what it's about.
F-type are the fast-blow ones indeed.
If you're speccing for fuses you need to know the current draw of the entire circuit for the Slo-Blo fuse and the local current draw for the Fast-Blow ones.
Overspec them and they'll be useless, underspec them and they'll blow whenever they feel like it.
If the Hammond Xformer has some margin on current it will try to regulate the mains input and since the heater windings have a step down ratio with respect to mains you'll quite likely be fine.
So, unless you know the mains to vary beyond +/- 5% alot I'd leave it there.
To be on the safe side you can monitor voltages with a DVM for a week or so, that would tell you what's happening inside.
If however you decide one day to put it behind the bridge, make sure the bridge can handle the extra current demand and check the heater voltages again.
Cheers,
Hi,
Very unfortunate, indeed.
I suppose I can count myself lucky that so far it's never, ever happened to me.
Actually, come to think of it, I hardly suffered any valve failure at all during the passed 25 years...seems it always happened to the other guy.
Knocking on wood, hard...ouch!
Cheers,
Very unfortunate, indeed.
I suppose I can count myself lucky that so far it's never, ever happened to me.
Actually, come to think of it, I hardly suffered any valve failure at all during the passed 25 years...seems it always happened to the other guy.
Knocking on wood, hard...ouch!
Cheers,
fdegrove said:Hi,
I would and here's upshot: if I were to put the resistors in I'd dare to leave the fuses out on the secundary of the xformer as well.
My guestimate is that the 6X5 may suffer from overvoltage and current at switch on eventually killed it after a while, especially when the rectifier is pushed already.[/qoute]
Well I think the resistor after the rectifier will limit current surge.
[qoute]Yes, I know but do you happen to know the company that publish that datasheet?
Not that this part is important to what you want to do, just me being curious to find out what it's about.[/qoute]
Well the 6X5GT is GE and the only datasheet I know for the 5852 is from Bendix. There are other datasheets for the 6X5 family but they are not in english. Both datasheets came from Frank's.
[qoute]
F-type are the fast-blow ones indeed.
If you're speccing for fuses you need to know the current draw of the entire circuit for the Slo-Blo fuse and the local current draw for the Fast-Blow ones.
Overspec them and they'll be useless, underspec them and they'll blow whenever they feel like it.
plate secondary is 225-0-255 65mA. Based on a computation I read:
((225+255) * .065) / 240 = 121mA
The mains here is 240V.
Filament secondary is 6.3V 2.5A. Based on a computation I read:
(6.3 * 2.5) / 240 = 65mA
So assuming the computations are correct, primaries need a 200mA f-type fuse and secondaries need a 121 mA slow blow?
[qoute]
If the Hammond Xformer has some margin on current it will try to regulate the mains input and since the heater windings have a step down ratio with respect to mains you'll quite likely be fine.
So, unless you know the mains to vary beyond +/- 5% alot I'd leave it there.
To be on the safe side you can monitor voltages with a DVM for a week or so, that would tell you what's happening inside.
If however you decide one day to put it behind the bridge, make sure the bridge can handle the extra current demand and check the heater voltages again. [/qoute]
Well the filament secondary is rated at 2.5A.
so .6A (from the 6X5) + (3 * .3) (from the 6DJ8) = 1.5A.
And the diodes to be used for the bridge is rated at 200V 4A.
Thanks
Jayel
Hi,
In order to put things into perspective again:
Exactly, which is why I suggest you forget about putting fuses in the secondaries, they're not exactly sonics boosters as you may know.
EC8010 already clarified the matter in previous post above.
Bendix is a special case manufacturer without peers but supply of any of their produce is very limited to say the least...just for info.
Assuming we won't use any fuses on the secundaries, all you need to do is calculate the total powerdraw in amps for the complete box and for the appropriate slo-blo fuse on the primary side.
Just spec the fuse as slo-blo 240VAC/x A when ordering.
I usually spec slightly higher, say 5% or so, to allow some margin.
The rest we can safely discard.
Cheers,
In order to put things into perspective again:
Exactly, which is why I suggest you forget about putting fuses in the secondaries, they're not exactly sonics boosters as you may know.
EC8010 already clarified the matter in previous post above.
Bendix is a special case manufacturer without peers but supply of any of their produce is very limited to say the least...just for info.
Assuming we won't use any fuses on the secundaries, all you need to do is calculate the total powerdraw in amps for the complete box and for the appropriate slo-blo fuse on the primary side.
Just spec the fuse as slo-blo 240VAC/x A when ordering.
I usually spec slightly higher, say 5% or so, to allow some margin.
The rest we can safely discard.
Cheers,
Hi,
Never put a fast-blow type on the primary side, it will pop instantly at turn on.
I have no way of knowing the correct value, I don't think you posted the entire circuit.
You need to add up all current draw correctly, allow some small margin and that's about it.
Uh..no, I meant fuses in general in the sense that they're a necessity not necessarilly a sonic blessing, rather to the contrary.
Cheers,
Never put a fast-blow type on the primary side, it will pop instantly at turn on.
I have no way of knowing the correct value, I don't think you posted the entire circuit.
You need to add up all current draw correctly, allow some small margin and that's about it.
Uh..no, I meant fuses in general in the sense that they're a necessity not necessarilly a sonic blessing, rather to the contrary.
Cheers,
I think I've been qouting the wrong message.
cavalli circuit as it is with a 6X5 instead of a 6X4.
I don't need to be concern with current surge as the first resistor which is a 100ohm will prevent overload of current. right?
Or do you mean the 150ohm (impedance/plate) resistor before the rectifier on both plates?
--------------------------------
as for current calculation
Here are the schematics for the power supply and amp
amp (1 channel) - http://home.swbell.net/acavalli/images/MJ_Headphone_Amp.gif
power supply - http://home.swbell.net/acavalli/images/MJ_Power_Supply_2.gif
The xformer use is a 369GX (can accomodate 240VAC mains). Specs are 225-0-225 65mA for plate and 6.3V 2.5A for filament.
-------------
Thank you for the help and patience.
Jayel
cavalli circuit as it is with a 6X5 instead of a 6X4.
I don't need to be concern with current surge as the first resistor which is a 100ohm will prevent overload of current. right?
Or do you mean the 150ohm (impedance/plate) resistor before the rectifier on both plates?
--------------------------------
as for current calculation
Here are the schematics for the power supply and amp
amp (1 channel) - http://home.swbell.net/acavalli/images/MJ_Headphone_Amp.gif
power supply - http://home.swbell.net/acavalli/images/MJ_Power_Supply_2.gif
The xformer use is a 369GX (can accomodate 240VAC mains). Specs are 225-0-225 65mA for plate and 6.3V 2.5A for filament.
-------------
Thank you for the help and patience.
Jayel
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