This is partly kinda dumb I guess... but do any of you know how to or of a source on how to make a fuse for low current?

I've got an old Gilfillan 25H (no schematic)
but almost the same as model 66AM
http://www.nostalgiaair.org/PagesByModel/596/M0008596.pdf
.... but only 5 tubes not 6.

...which I completely re-capped.
It uses a 6x5 rectifier which seemed to be working for a while playing nicely... though B+ was very high for some crazy reason. (about +300v) but normal is only 230v

The high B+ came to my attention because.., while the radio was playing along very nicely I noticed that the 6v6 output tube's cathode resistor was cooking.. the tube was drawing too much current. The cathode was at 30v not the normal 13v... and the plate voltage was way down.

Then the 15k dropping resistor to the 6sa7 and the 6sk7 grid-2 was also cooking.... and drawing 78ma

I eventually put a 950 ohm 5 watt ceramic resistor on the output of the rectifier leading to the field coil which helped and dropped the B+ down to a more reasonable 250v
While trying to localize the problem of cooking resistors... I started smelling the transformer cooking too... could even hear boiling tar inside popping away like popcorn.

The 6x5 was glowing like a christmas tree too. It tested bad on one plate and marginal on the other.

After the transformer cooled down and I checked the rest of all components... R3 the dropping resistor for the 6sk7 grid2 was the only component of question. The print shows a 10k... but the resistor in the circuit was marked 15k... but it measured only 3k !!
So I put a new 15 k in there.

I have a new 6x5 in now and the B+ seems to be much more correct.

Without the 950 ohm resistor at the cathode the B+ is around 265v and with it in ...the B+ is 215v
The print shows 230v
otherwise now ...Everything else measures correctly now.

There's a note-#3 on one of my other prints that is glued to the back of the model 66AM, about limiting the HV CT to protect the 6x5 for 70ma. But they don't explain how.

I like this idea but more for the sake of saving this dear old transformer.

Anyway... back to the point of my question.
I looked all over my joint here... to try to find a 70 - 100 ma fuse with not much luck.
The actual HV CT current is only drawing 40ma.
The only fuse I found around here that's even close is 1/8 amp or 125ma
So I'm using this on the CT... but I'd like something safer.
I was trying to figure out what I might have around the house that would work as a fuse... but I can't think of anything.
Maybe I could find some fine stranded wire and try using one tiny strand. But how do I know it's current rating.

The only thing I could find was a AWG wire chart showing me that 40 gauge wire can only carry 90ma.. but another AWG chart says 32 guage carries 90ma... and 40guage carries only 14ma.

So I don't know which chart to believe either..

So I was wondering if some home-brew guy like a 1920s experimenter or the Ham manual or something can show you how to make your own fuse in a pinch.

I wonder if there is some acceptable substitute material around the normal shop to use or experiment with.

I could easily use a #47 lamp but that's 150ma.

Do you suppose the 1/8 amp fuse I have in there now on the CT will save the transformer?
.... well at least the HV winding part?

The model 66AM chassis plate says it's 55-watts so if I had fused the input AC ... I guess a 1/2 amp would do?

The ratings on the wire are most likely the maximum recomended current you want to send through the wire. It is not the point at which the wire will fuse. The #47 bulb rating is what it draws at 6.3 volts which is not the point at which it would fuse. the wire often used in fuses is, I think, lead or some other low temperature melting point wire. The fuse you found is the better choice for now. If a short occurs the initial current can be quite high. This is because you are discharging the filter capacitors quickly. Smoking is bad for you and your radio's health.

D. Witt

:This is partly kinda dumb I guess... but do any of you know how to or of a source on how to make a fuse for low current?
:
:I've got an old Gilfillan 25H (no schematic)
:but almost the same as model 66AM
:http://www.nostalgiaair.org/PagesByModel/596/M0008596.pdf
:.... but only 5 tubes not 6.
:
: ...which I completely re-capped.
:It uses a 6x5 rectifier which seemed to be working for a while playing nicely... though B+ was very high for some crazy reason. (about +300v) but normal is only 230v
:
:The high B+ came to my attention because.., while the radio was playing along very nicely I noticed that the 6v6 output tube's cathode resistor was cooking.. the tube was drawing too much current. The cathode was at 30v not the normal 13v... and the plate voltage was way down.
:
:Then the 15k dropping resistor to the 6sa7 and the 6sk7 grid-2 was also cooking.... and drawing 78ma
:
:I eventually put a 950 ohm 5 watt ceramic resistor on the output of the rectifier leading to the field coil which helped and dropped the B+ down to a more reasonable 250v
: While trying to localize the problem of cooking resistors... I started smelling the transformer cooking too... could even hear boiling tar inside popping away like popcorn.
:
:The 6x5 was glowing like a christmas tree too. It tested bad on one plate and marginal on the other.
:
:After the transformer cooled down and I checked the rest of all components... R3 the dropping resistor for the 6sk7 grid2 was the only component of question. The print shows a 10k... but the resistor in the circuit was marked 15k... but it measured only 3k !!
: So I put a new 15 k in there.
:
:I have a new 6x5 in now and the B+ seems to be much more correct.
:
:Without the 950 ohm resistor at the cathode the B+ is around 265v and with it in ...the B+ is 215v
:The print shows 230v
: otherwise now ...Everything else measures correctly now.
:
:There's a note-#3 on one of my other prints that is glued to the back of the model 66AM, about limiting the HV CT to protect the 6x5 for 70ma. But they don't explain how.
:
:I like this idea but more for the sake of saving this dear old transformer.
:
:Anyway... back to the point of my question.
:I looked all over my joint here... to try to find a 70 - 100 ma fuse with not much luck.
:The actual HV CT current is only drawing 40ma.
:The only fuse I found around here that's even close is 1/8 amp or 125ma
:So I'm using this on the CT... but I'd like something safer.
:I was trying to figure out what I might have around the house that would work as a fuse... but I can't think of anything.
:Maybe I could find some fine stranded wire and try using one tiny strand. But how do I know it's current rating.
:
:The only thing I could find was a AWG wire chart showing me that 40 gauge wire can only carry 90ma.. but another AWG chart says 32 guage carries 90ma... and 40guage carries only 14ma.
:
:So I don't know which chart to believe either..
:
:So I was wondering if some home-brew guy like a 1920s experimenter or the Ham manual or something can show you how to make your own fuse in a pinch.
:
:I wonder if there is some acceptable substitute material around the normal shop to use or experiment with.
:
: I could easily use a #47 lamp but that's 150ma.
:
:Do you suppose the 1/8 amp fuse I have in there now on the CT will save the transformer?
:.... well at least the HV winding part?
:
:The model 66AM chassis plate says it's 55-watts so if I had fused the input AC ... I guess a 1/2 amp would do?
:
:

Hi Peter

Is this a test? I would first find the reason your 6V6 has high cathode voltage. This is usually due to leaky coupling cap to pin #5. When the cap is leaky grid #1 starts to go positive causing a tube to draw too much current. Has the radio been recapped?

Has the power transformer been replaced? B+ at cathode of a 6X5 of 300 volts isn't too high but there should be a speaker field or wire wound resistor reducing voltage to radio circuitry. Using a 1K @ 10 watt resistor should drop 300 to around 230 volts.

Also looks like you need to replace the 6X5 and transformer soon if the radio is left on.

Dim suggested a #47 lamp as fuse. This would limit current to around 150 ma. You can buy smaller fuses but they may burn out at turn due to charging filter caps. Might want a slo-blo fuse as used in early TV's.

Norm

:This is partly kinda dumb I guess... but do any of you know how to or of a source on how to make a fuse for low current?
:
:I've got an old Gilfillan 25H (no schematic)
:but almost the same as model 66AM
:http://www.nostalgiaair.org/PagesByModel/596/M0008596.pdf
:.... but only 5 tubes not 6.
:
: ...which I completely re-capped.
:It uses a 6x5 rectifier which seemed to be working for a while playing nicely... though B+ was very high for some crazy reason. (about +300v) but normal is only 230v
:
:The high B+ came to my attention because.., while the radio was playing along very nicely I noticed that the 6v6 output tube's cathode resistor was cooking.. the tube was drawing too much current. The cathode was at 30v not the normal 13v... and the plate voltage was way down.
:
:Then the 15k dropping resistor to the 6sa7 and the 6sk7 grid-2 was also cooking.... and drawing 78ma
:
:I eventually put a 950 ohm 5 watt ceramic resistor on the output of the rectifier leading to the field coil which helped and dropped the B+ down to a more reasonable 250v
: While trying to localize the problem of cooking resistors... I started smelling the transformer cooking too... could even hear boiling tar inside popping away like popcorn.
:
:The 6x5 was glowing like a christmas tree too. It tested bad on one plate and marginal on the other.
:
:After the transformer cooled down and I checked the rest of all components... R3 the dropping resistor for the 6sk7 grid2 was the only component of question. The print shows a 10k... but the resistor in the circuit was marked 15k... but it measured only 3k !!
: So I put a new 15 k in there.
:
:I have a new 6x5 in now and the B+ seems to be much more correct.
:
:Without the 950 ohm resistor at the cathode the B+ is around 265v and with it in ...the B+ is 215v
:The print shows 230v
: otherwise now ...Everything else measures correctly now.
:
:There's a note-#3 on one of my other prints that is glued to the back of the model 66AM, about limiting the HV CT to protect the 6x5 for 70ma. But they don't explain how.
:
:I like this idea but more for the sake of saving this dear old transformer.
:
:Anyway... back to the point of my question.
:I looked all over my joint here... to try to find a 70 - 100 ma fuse with not much luck.
:The actual HV CT current is only drawing 40ma.
:The only fuse I found around here that's even close is 1/8 amp or 125ma
:So I'm using this on the CT... but I'd like something safer.
:I was trying to figure out what I might have around the house that would work as a fuse... but I can't think of anything.
:Maybe I could find some fine stranded wire and try using one tiny strand. But how do I know it's current rating.
:
:The only thing I could find was a AWG wire chart showing me that 40 gauge wire can only carry 90ma.. but another AWG chart says 32 guage carries 90ma... and 40guage carries only 14ma.
:
:So I don't know which chart to believe either..
:
:So I was wondering if some home-brew guy like a 1920s experimenter or the Ham manual or something can show you how to make your own fuse in a pinch.
:
:I wonder if there is some acceptable substitute material around the normal shop to use or experiment with.
:
: I could easily use a #47 lamp but that's 150ma.
:
:Do you suppose the 1/8 amp fuse I have in there now on the CT will save the transformer?
:.... well at least the HV winding part?
:
:The model 66AM chassis plate says it's 55-watts so if I had fused the input AC ... I guess a 1/2 amp would do?
:
:

Hey Norm,
Dim did not suggest using a #47 bulb. Mr Pete did. I think Dim's reasoning is don't use regular wire or a bulb as that you don't know at what current the wire or filament will fuse at.

D. Witt

:Hi Peter
:
: Is this a test? I would first find the reason your 6V6 has high cathode voltage. This is usually due to leaky coupling cap to pin #5. When the cap is leaky grid #1 starts to go positive causing a tube to draw too much current. Has the radio been recapped?
:
: Has the power transformer been replaced? B+ at cathode of a 6X5 of 300 volts isn't too high but there should be a speaker field or wire wound resistor reducing voltage to radio circuitry. Using a 1K @ 10 watt resistor should drop 300 to around 230 volts.
:
: Also looks like you need to replace the 6X5 and transformer soon if the radio is left on.
:
: Dim suggested a #47 lamp as fuse. This would limit current to around 150 ma. You can buy smaller fuses but they may burn out at turn due to charging filter caps. Might want a slo-blo fuse as used in early TV's.
:
:Norm
:
:
::This is partly kinda dumb I guess... but do any of you know how to or of a source on how to make a fuse for low current?
::
::I've got an old Gilfillan 25H (no schematic)
::but almost the same as model 66AM
::http://www.nostalgiaair.org/PagesByModel/596/M0008596.pdf
::.... but only 5 tubes not 6.
::
:: ...which I completely re-capped.
::It uses a 6x5 rectifier which seemed to be working for a while playing nicely... though B+ was very high for some crazy reason. (about +300v) but normal is only 230v
::
::The high B+ came to my attention because.., while the radio was playing along very nicely I noticed that the 6v6 output tube's cathode resistor was cooking.. the tube was drawing too much current. The cathode was at 30v not the normal 13v... and the plate voltage was way down.
::
::Then the 15k dropping resistor to the 6sa7 and the 6sk7 grid-2 was also cooking.... and drawing 78ma
::
::I eventually put a 950 ohm 5 watt ceramic resistor on the output of the rectifier leading to the field coil which helped and dropped the B+ down to a more reasonable 250v
:: While trying to localize the problem of cooking resistors... I started smelling the transformer cooking too... could even hear boiling tar inside popping away like popcorn.
::
::The 6x5 was glowing like a christmas tree too. It tested bad on one plate and marginal on the other.
::
::After the transformer cooled down and I checked the rest of all components... R3 the dropping resistor for the 6sk7 grid2 was the only component of question. The print shows a 10k... but the resistor in the circuit was marked 15k... but it measured only 3k !!
:: So I put a new 15 k in there.
::
::I have a new 6x5 in now and the B+ seems to be much more correct.
::
::Without the 950 ohm resistor at the cathode the B+ is around 265v and with it in ...the B+ is 215v
::The print shows 230v
:: otherwise now ...Everything else measures correctly now.
::
::There's a note-#3 on one of my other prints that is glued to the back of the model 66AM, about limiting the HV CT to protect the 6x5 for 70ma. But they don't explain how.
::
::I like this idea but more for the sake of saving this dear old transformer.
::
::Anyway... back to the point of my question.
::I looked all over my joint here... to try to find a 70 - 100 ma fuse with not much luck.
::The actual HV CT current is only drawing 40ma.
::The only fuse I found around here that's even close is 1/8 amp or 125ma
::So I'm using this on the CT... but I'd like something safer.
::I was trying to figure out what I might have around the house that would work as a fuse... but I can't think of anything.
::Maybe I could find some fine stranded wire and try using one tiny strand. But how do I know it's current rating.
::
::The only thing I could find was a AWG wire chart showing me that 40 gauge wire can only carry 90ma.. but another AWG chart says 32 guage carries 90ma... and 40guage carries only 14ma.
::
::So I don't know which chart to believe either..
::
::So I was wondering if some home-brew guy like a 1920s experimenter or the Ham manual or something can show you how to make your own fuse in a pinch.
::
::I wonder if there is some acceptable substitute material around the normal shop to use or experiment with.
::
:: I could easily use a #47 lamp but that's 150ma.
::
::Do you suppose the 1/8 amp fuse I have in there now on the CT will save the transformer?
::.... well at least the HV winding part?
::
::The model 66AM chassis plate says it's 55-watts so if I had fused the input AC ... I guess a 1/2 amp would do?
::
::

:Hey Norm,
:Dim did not suggest using a #47 bulb. Mr Pete did. I think Dim's reasoning is don't use regular wire or a bulb as that you don't know at what current the wire or filament will fuse at.
:
:D. Witt
:
:
::Hi Peter
::
:: Is this a test? I would first find the reason your 6V6 has high cathode voltage. This is usually due to leaky coupling cap to pin #5. When the cap is leaky grid #1 starts to go positive causing a tube to draw too much current. Has the radio been recapped?
::
:: Has the power transformer been replaced? B+ at cathode of a 6X5 of 300 volts isn't too high but there should be a speaker field or wire wound resistor reducing voltage to radio circuitry. Using a 1K @ 10 watt resistor should drop 300 to around 230 volts.
::
:: Also looks like you need to replace the 6X5 and transformer soon if the radio is left on.
::
:: Dim suggested a #47 lamp as fuse. This would limit current to around 150 ma. You can buy smaller fuses but they may burn out at turn due to charging filter caps. Might want a slo-blo fuse as used in early TV's.
::
::Norm
::
::
:::This is partly kinda dumb I guess... but do any of you know how to or of a source on how to make a fuse for low current?
:::
:::I've got an old Gilfillan 25H (no schematic)
:::but almost the same as model 66AM
:::http://www.nostalgiaair.org/PagesByModel/596/M0008596.pdf
:::.... but only 5 tubes not 6.
:::
::: ...which I completely re-capped.
:::It uses a 6x5 rectifier which seemed to be working for a while playing nicely... though B+ was very high for some crazy reason. (about +300v) but normal is only 230v
:::
:::The high B+ came to my attention because.., while the radio was playing along very nicely I noticed that the 6v6 output tube's cathode resistor was cooking.. the tube was drawing too much current. The cathode was at 30v not the normal 13v... and the plate voltage was way down.
:::
:::Then the 15k dropping resistor to the 6sa7 and the 6sk7 grid-2 was also cooking.... and drawing 78ma
:::
:::I eventually put a 950 ohm 5 watt ceramic resistor on the output of the rectifier leading to the field coil which helped and dropped the B+ down to a more reasonable 250v
::: While trying to localize the problem of cooking resistors... I started smelling the transformer cooking too... could even hear boiling tar inside popping away like popcorn.
:::
:::The 6x5 was glowing like a christmas tree too. It tested bad on one plate and marginal on the other.
:::
:::After the transformer cooled down and I checked the rest of all components... R3 the dropping resistor for the 6sk7 grid2 was the only component of question. The print shows a 10k... but the resistor in the circuit was marked 15k... but it measured only 3k !!
::: So I put a new 15 k in there.
:::
:::I have a new 6x5 in now and the B+ seems to be much more correct.
:::
:::Without the 950 ohm resistor at the cathode the B+ is around 265v and with it in ...the B+ is 215v
:::The print shows 230v
::: otherwise now ...Everything else measures correctly now.
:::
:::There's a note-#3 on one of my other prints that is glued to the back of the model 66AM, about limiting the HV CT to protect the 6x5 for 70ma. But they don't explain how.
:::
:::I like this idea but more for the sake of saving this dear old transformer.
:::
:::Anyway... back to the point of my question.
:::I looked all over my joint here... to try to find a 70 - 100 ma fuse with not much luck.
:::The actual HV CT current is only drawing 40ma.
:::The only fuse I found around here that's even close is 1/8 amp or 125ma
:::So I'm using this on the CT... but I'd like something safer.
:::I was trying to figure out what I might have around the house that would work as a fuse... but I can't think of anything.
:::Maybe I could find some fine stranded wire and try using one tiny strand. But how do I know it's current rating.
:::
:::The only thing I could find was a AWG wire chart showing me that 40 gauge wire can only carry 90ma.. but another AWG chart says 32 guage carries 90ma... and 40guage carries only 14ma.
:::
:::So I don't know which chart to believe either..
:::
:::So I was wondering if some home-brew guy like a 1920s experimenter or the Ham manual or something can show you how to make your own fuse in a pinch.
:::
:::I wonder if there is some acceptable substitute material around the normal shop to use or experiment with.
:::
::: I could easily use a #47 lamp but that's 150ma.
:::
:::Do you suppose the 1/8 amp fuse I have in there now on the CT will save the transformer?
:::.... well at least the HV winding part?
:::
:::The model 66AM chassis plate says it's 55-watts so if I had fused the input AC ... I guess a 1/2 amp would do?
:::
:::
Check allelectronics.com for low current fuses. Nick

Radio Shack sells fuses that are as small as .25 amperes, which is much higher than what the radio normally draws in the B circuit. However, what the radio draws and what the transformer is capable of putting out are two different things. If you want a fuse that'll protect against even slight increases in current draw (not recommended, as this happens whenever the set is turned on warm--electrolytics), then you want a fuse close to the current draw of the radio. However, if you only want protection against shorts, trust me, a .25 ampere fuse will blow if you short out the B+. A #47 bulb is an excellent idea. It will readily blow if a short occurs in the B section. There are also bulbs sold by www.tubesandmore.com that are rated for .06 amperes (what the radio draws). These, however, will blow every time the radio is turned on warm. I forgot their number, but they're 2.0 volt .06 ampere bulbs. I recommend the #47 bulb.

Also, regarding the transformer and excessive voltage problem, I forgot to suggest earlier that you should check your heater voltages. Are they a bit high, too? You could have a shorted primary in the transformer, which would cause overheating and excessive voltages. A short in the primary will raise secondary voltages, will reduce the primary impedance, causing it to overheat, and the shorted windings will have current induced in them, which will cause even more current draw in the remaining primary, which will make it even hotter, and the shorted windings will heat, themselves.

T.

Thanks Norm:.. lol
No this isn't a test.. I was lost too..

Yes as I indicated I had recapped before noticing the high B+ which I only saw as soon as I started playing the radio after re-capping and noticing the 6v6 resistor getting hot and the 2nd grid dropping resistor sizzling too...

That was when I put in the 950 ohm resistor... but it was after that that I saw the 6x5 was lit up bright.. and tested bad.
So I have replaced the 6x5 and left in the 950 ohm resistor...
So unless it was all casued by some kind of short in the 6x5 ...the only other questionable component that may have contributed to the begining of the problem..was that grid-2 resistor for the 6sk7 that measured as only 3k though it was marked 15k... I've replaced it the with a new 15k now and of course a new 6x5 and now... everything now measures properly or maybe a bit low (b+ now at 205v) because I left in the 950 ohm resistor.
The transformer was not replaced and measured 315-315 AC as the print indicated.