low battery voltage

[paulw]

As I hadn't check the state of my batteries in the Quickie for awhile, even though everything was sounding great I got out the meter only to find the total output for the four 9v's was only 4.75v :-0

Think I'd better re-charge those later - but can running the heater voltages this low do any damage?  I would have thought when the 3S4's were used in radios the only time the batteries would have been changed would have been when no sound came out, so perhaps not.

Paul

[Paul Joppa]

I'm a little confused. The heater batteries are the 1.5-volt D-cells, and are considered dead if they are down to 1.0 volts. (Duracell says 0.9 volts; they are probably thinking of flashlights.) Similarly, I think the 9-v alkalines are dead when they fall to 6.0 volts, but if it still sounds good there's no reason to worry about them.

A low filament voltage will reduce the protective electron cloud around the filament, allowing it to be damaged by ion bombardment - so-called "cathode poisoning". At the low plate voltages of the Quickie, the ions can't be accelerated to very high velocities, so they can't do so much damage.

Overall, the risk is small and the tubes are cheap - I wouldn't worry too much.

[paulw]

I'm a little confused. The heater batteries are the 1.5-volt D-cells, and are considered dead if they are down to 1.0 volts. (Duracell says 0.9 volts; they are probably thinking of flashlights.) Similarly, I think the 9-v alkalines are dead when they fall to 6.0 volts, but if it still sounds good there's no reason to worry about them.

Yes, I didn't mean the heater 1.5's but the filament 9v batteries - title changed.

Must do checks on the NiMH 9v's more often & it will be interesting to see if there is a jump in 'sound quality' when I put them back freshly charged tonight.

Paul

[cpaul]

To clarify again, the D-cells are the filament power supply (low voltage - 1.5v).  The 9v batteries are NOT filament batteries, but rather plate voltage that carries the signal swing and gain.  They are the "B+" for Quickie.

[paulw]

To clarify again, the D-cells are the filament power supply (low voltage - 1.5v).  The 9v batteries are NOT filament batteries, but rather plate voltage that carries the signal swing and gain.  They are the "B+" for Quickie.

Well just goes to show how easy I get confused - title changed to generic 'battery' whatever their purpose :

[cpaul]

Paul,

No worries about the confusion.  I'm usually confused about this stuff.  Re: the 9v supply, you mentioned that you measured TOTAL output of 4.75v from all 4 9v together (measured at the two center wires per the manual)?  Or did you mean 4.75v each?  In either case, and you say you were still getting good sound?  I'm very interested if either is the case, as I can't see how Quickie could work under such low B+.

Carl

[paulw]

Paul,

No worries about the confusion.  I'm usually confused about this stuff.  Re: the 9v supply, you mentioned that you measured TOTAL output of 4.75v from all 4 9v together (measured at the two center wires per the manual)?  Or did you mean 4.75v each?  In either case, and you say you were still getting good sound?  I'm very interested if either is the case, as I can't see how Quickie could work under such low B+.

Carl

Total for all 4 as measured at the centre wires, individually one of the cells was under 1volt, the 3 others just over.

Paul

[Grainger49]

There seems to be some difference between a filament and a heater.  I think both are heaters but it takes a specific construction, or something, to be a filament.

You are always safe to refer to the heater, or in the case of a direct heated triode (DHT), the heater leads.  Both of the heater leads on the 2A3 tube, a DHT, are attached to the cathode but at opposite ends.  The heater current passes from one end of the cathode to the other heating the cathode directly.

[Doc B.]

Filament is used when talking about a directly heated tube like the 3S4. In this case the "heater" and the cathode are one element in the tube. In an indirectly heated tube like a 12AU7 the term heater is used for the element that would be the filament in a directly heated tube, and the cathode is a separate element that is electrically isolated but gets heated by the radiation of the heater in order to generate an electron cloud like that which comes off the filament in a directly heated tube.

[paulw]

Well popped my back-up set of alkaline PP3's in whilst the NiMH's are charging.  OK I thought it sounded great but I'm going to have to downgrade that to an 'OK' - now it sounds great!!!

Vastly more pace, better at both frequency extremes, bigger soundstage...Hmmm, must check the batteries more often, just goes to show how you get used to the sound if the change is gradual.  The other aspect is perhaps the psychoacoustic impression that follows the decline of the batteries!  As I mostly listen to LP's I been feeling recently that my LP spinner needed a bit of TLC, timing sounded off, so cleaned the belt, pulley, platter drive surface, tried repositioning the motor, check the speed for drift, thought perhaps it was time to consider that PSU upgrade to allow multiple motor's - no, just needed some better batteries in the preamplifier to bring back that magic.

Funny how the brain reacts to stimulation.

Paul