Tube 6AQ5 vs 6AQ5A "Heater Difference"

[Les Dickson]

I’m working in restoring a PYE model 53D and the 6AQ5 tube is not good. I have several 6AQ5A tubes but according the the radiomuseum web site the heaters are different. When I look at the data sheets the only difference I can see is that the newer 6AQ5A has “heater controlled warm-up time.”
Any advice on substituting the 6AQ5A in?

Attachments:

1. 

   6AQ5-schem.png
   

2. 

   6AQ5A-schem.png
   

3. 

   pye-53D-front.jpg
   

1. 6aq5a_rca_data_01_349770.pdf
2. 6aq5_rca_data_01_349763.pdf

[Alistair Thomson]

According to Wikipedia,

https://en.wikipedia.org/wiki/6AQ5

the 6AQ5A is an industrially rated 6AQ5 with the modified heater action as you said, so it will be OK in your radio.

[Les Dickson]

Thanks Alistair, much appreciated. I never thought of checking Wikipedia.

[John Greenland]

Hi Les,
In checking the RCA tube manuals that I have, the 6AQ5 from the 1947 version shows all kinds of caveats with using the 6AQ5 in series heater string configurations. None for parallel.

In the 1960 version of the tube manual, the 6AQ5 is shown as discontinued and replaced by the 6AQ5-A which has been designed with a heater which can easily be used in series configurations.
It seems that this particular tube was a common one in TV’s and seems to be the big reason for its re-designed heater.

Basically the tubes are interchangeable in parallel configurations.
BTW — Fair Radio Sales in Lima, Ohio are showing a listing for 6AQ5 pull outs in a lot of 10 for $10 US.

TTFN
John G.

[Les Dickson]

Thanks for the info John, much appreciated.

[Don Henschel]

I’m surprised the 6AQ5 goes that far back. I’m used to seeing the common 6V6 commonly used even as late as 52 or later and of course if you desire a much louder “shindig” a 6L6. What surprised me is how much higher the voltages and wattage are on that iddy biddy little peanut. No wonder they run so hot in comparison. My Macaroni in my 1950 Mercury has the 6V6 crammed tightly against the vibrator all within a tiny square box with the vibrator lasting years and meanwhile I was working on a radio from a 52 Ford Meteor with a 6AQ5. The wiring within the vibrator was brittle and crisp from the heat as was the sponge.

[Author]

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