Opened up this Philco, and what the.....??

[maxhifi]

Maybe the old caps shorted and took out the rectifier, so he decided to add some fuses to the new ones?

[old_coot88]

If the bulbs are directly in series with the caps, they would add a huge "ESR" value, diminishing the caps' effectiveness.
'Specially the one coming directly off the rectifier.

[Findm-Keepm]

Originally Posted by old_coot88

If the bulbs are directly in series with the caps, they would add a huge "ESR" value, diminishing the caps' effectiveness.
'Specially the one coming directly off the rectifier.

A #44 bulb has about a tenth of an ohm cold resistance, hardly a huge ESR value. I have a 1940's Coyne manual that details adding current limiting of B supplies with a dial lamp. Exceed the current rating of the bulb, and it blows, and in-between, it limits the current. It saved many a costly power tranny.

You've got an old-timer's following of the Coyne Radio repair manual. I have only a couple of volumes - it was 8 in all.

Cheers,

[old_coot88]

I was guessing they were #47 bulbs. Just tested a couple of #47s. Each shows 7 ohms cold, rising to 10 ohms (due to heating from the VOM's 1.5V battery).

I don't have a #44 to test, but it would probably be around 4.2 ohms cold (due to higher current rating, .25A vs .15A).

Though maybe not "huge" but still a signifigant ESR figure if the bulb's in series with a 10 mf cap. But then you gotta figger in filament heating due to ripple, which will further increase resistance.

In any case, it seems like the more rational place to put a limiter/fuse would be directly in the B+ line coming off the rectifier.
Or two bulbs, one in each leg of the HV winding going to the rectifier plates.
Or, one bulb in the center-tap lead of the HV winding.

Just curious - where did you get the 1/10 ohm figure for the #44 bulb?

[Findm-Keepm]

Originally Posted by old_coot88

I was guessing they were #47 bulbs. Just tested a couple of #47s. Each shows 7 ohms cold, rising to 10 ohms (due to heating from the VOM's 1.5V battery).

I don't have a #44 to test, but it would probably be around 4.2 ohms cold (due to higher current rating, .25A vs .15A).

Though maybe not "huge" but still a signifigant ESR figure if the bulb's in series with a 10 mf cap. But then you gotta figger in filament heating due to ripple, which will further increase resistance.

In any case, it seems like the more rational place to put a limiter/fuse would be directly in the B+ line coming off the rectifier.
Or two bulbs, one in each leg of the HV winding going to the rectifier plates.
Or, one bulb in the center-tap lead of the HV winding.

Just curious - where did you get the 1/10 ohm figure for the #44 bulb?

Chicago miniature lamp catalog, dated 4/63, "measured at 25degrees C with millivolt bridge, to avoid heating effects." My L&N millivolt potentiometer has a setup card telling how to perform cold testing of tube filaments, all done with a few millivolts.

What do you figure for the ESR? 10 @450 is worst case 28 or so ohms......for that vintage......

I wonder why two bulbs, perhaps taps of the B supply, or a straight splitting to reduce the current out each leg through the bulbs?

Looks a lot like my Philco 86 chassis....