Dynaco St-70 Running On a 83 Murcury Vapor Recitifer!!

[JohnT123]

I used to have a Stark tube tester with an 83. It never glowed blue in use. Perhaps there has to be a certain voltage/temperature before the ionization really kicks in.

 

[zackthedog]

It was used and powered just like any other rectifier they had, that's why the conversion to the 5AR4 is so simple.

Isn't that what the standby switch was for?

 

[JohnT123]

You make a good point. The standby was designed to allow the filaments to heat up before applying high voltage.

 

[Steve O]

I have a bunch of Amperite delay tubes in the stash. Anyone have a schematic for a power supply using this scheme?

A “power supply” using an amperite thermal delay is awfully general. Attached is a conceptual schematic that uses an amperite delay to drive a relay such that amperite contact ratings are not a factor and momentary power outages reinitiate the the timing cycle. This is essentially the same circuit used in the Kepco regulated DC supply to protect its MV rectifiers. As with any general circuit of this nature, you have to determine it’s suitability to your application and modify as necessary.

 

[analog addict]

Thanks!

 

[Dandy]

Isn't that what the standby switch was for?

But does it do this for the rectifier tube? I thought it only switched off the DC for the rest of the circuit.

 

[JohnT123]

The stby sw cuts the B+ after the rectifier. As soon as the power is on, the filaments and bias supply (where applicable) are energized. This includes the rectifier. The DC coming out of the power supply is interrupted so it can't get to the plates of the other tubes.

The 83 mv tube has nothing to do with the development of the stby sw. It's just a coincidence. In fact, in guitar amps the rectifier is asked to start doing its thing as soon as the power is turned on.

 

[PakProtector]

The blue glow is at least proportional to current. The 866's in my 6CB5 amps make one heck of a flash when the relay closes and they have to charge up a sizeable cap that is the LC filter.
cheers,
Douglas

 

[zackthedog]

You make a good point. The standby was designed to allow the filaments to heat up before applying high voltage.

Interesting that they have a tiny cap before the standby swith, followed by 40uF (!). Perhaps the .05uF cap helped the 83 handle the 40uF?

The stby sw cuts the B+ after the rectifier. As soon as the power is on, the filaments and bias supply (where applicable) are energized. This includes the rectifier. The DC coming out of the power supply is interrupted so it can't get to the plates of the other tubes.

The 83 mv tube has nothing to do with the development of the stby sw. It's just a coincidence. In fact, in guitar amps the rectifier is asked to start doing its thing as soon as the power is turned on.

Yes, I know standby switches are common in guitar amps. But in this case it seems it would protect the 83 as well. You can always bang on a 5U4 but 83's tend to behave badly without a little warm-up, don't you think?

In my "Sound Practices (magazine)" days of zany experimenting, the 83 was thought to be the bee's knees, but you still had to coddle it a bit, IIRC.

 

[s-petersen]

The filaments on the 5Y3GT and 83 tubes on my Hickok 800 are lit as soon as the unit is plugged in, and the 800's switch is in the off position. The other funny thing is the 800 manual does not state anything about a waiting period prior to testing, I can only assume the reason is due to the filaments being on upon plug in, and also the amount of setup time for testing tubes.

Also, the blue glow never illuminates from the Hickok's 83 tube when in use. I've tested a 83 tube on this tester and the blue glow illuminates, but the Hickok's 83 doesn't glow. Swapped tubes and the results remain the same, strange...

When I received my TV7 the rectifier glowed brightly (and the transformer hummed) when the test button was pressed, because there was a short in between the socket saver and the 9 pin socket, once repaired, the tube barely glows during testing