Question on the PSU Redd.47 with the regulators oa2.

Greetings to all.

I assembled the HT power supply for Redd.47 according to the original scheme with oa2 regulator.

I have one question.
What will happen if this HT power supply is switched on without load, can oa2 fail (I mean physical damage, tube  explosion, etc.) ? :

It can be switched on without load, they are comparable to zeners in this regard. Many OA2s are noisy, you could easily compare them with zeners if it is new build.

Greetings to all.

I do not want to switch to zeners and use the oa2 controls.
Everything works well, but I do not understand one thing.

At the moment of switching on, while the tubes did not heat up, on oa2 comes 384v.
From this, the oa2 is immediately lit (brighter than usual) and the regulated is 296v. occurs virtually without load. Perhaps they work in a critical mode.
Then, when the tubes warm up (15-30sec.), Everything is normalized.

I'm still afraid that at the moment of switching on, while the tubes did not heat up, oa2 could fail (explode, etc.).
  
Perhaps it is worth making a separate HV switch (after the diode bridge) or can everything be left as it is and nothing to fear?

Oa2 data sheet might help.

I am curious if original had ss diodes

Unfortunately Oa2 data sheet can not help me. There it is not said whether it is possible to include Oa2 without load (while the loading tubes are cold).

And about the rectifier ss or tube:

In the beginning, I had a rectifier on a 6X4 tube.
Everything worked well, but I have a small case and it was very hot for him.

In the technical description REDD.47 it is written -

- "" H.T. is fed in at between 380 and 400 volts direct from the small reservoir condense: of an external rectifier unit. An additional reservoir condenser is incorporated in the amplifier. Thus when several amplifiers are connected to a common rectifier unit, the total reservoir capacitance increases roughly in proportion to the load current. Provided that the rectifier and transformer internal resistance are small, this results in much improved regulation of the power supply, and the voltage remains approximately constant, indepen ent of load.""

In the original circuit REDD.47 - the capacity of the first filter-capacitor is 80u.
Given that there are quite a lot of REDD.47 amps in the console, when they are turned on at the same time, a rather large capacity is obtained.

I did not hear about the rectifier tube, after which it is possible to use capacitors of such a large capacitance.

I think it is quite logical to assume that the original rectifier was - SS.

My version of the HV power supply, filter resistors - 510 Ohm (instead of 1K) - for my transformer.
Now I have put a separate switch after the diode bridge, I'm still afraid to immediately apply voltage to the Oa2.
And if you use filter resistors, as in the original scheme - 1K., Then the transformer should produce an even higher spinning that would "set" Oa2 on fire.
And when you turn on without load, will it be even more dangerous?

Although maybe I'm wrong and it's possible to do without a separate B + switch.

- This is my question.

Philips datasheet indicates max ignition voltage in complete darkness as 225 for a single regulator so 450vdc stacked...and shows max current shunted as  75 mA max. So you should be good in that regard.
Also notes too high parallel cap can cause oscillation.

If I understood correctly, then 225v (x2 450v) is allowed for "ignition" in total darkness.

But if Oa2 is not in total darkness and starting current is 0mA, (until EF86 and E88CC warm up).
What time can the Oa2 withstand such a critical voltage (225v x2-450v) without damage and destruction?

If I am reading it correctly, max ignition voltage means the highest voltage  necessary to get the regulator to turn on and begin regulating.


Since a higher voltage of safe  operation is not listed, I'd assume it is much much higher.
Max current is a parameter that is specified and describes the power dissipation limit of the device

Well, yes, the maximum ignition voltage is indicated, and what is the minimum load at this voltage can be - it is not written.

As I wrote earlier, I certainly tried to include everything at once, without the delay of filing HV.
Oa2 immediately "lit" and HV was 296V, as expected. But the glow of Oa2 was slightly brighter than usual.

After 15-30 seconds, when the EF86 and E88CC were warmed up - the glow was normalized and became less bright, as it should be in the normal mode.

But at the same time, the voltage from the very beginning to the normal mode was fixed at 296V.
I'm afraid and while I deliver the HV with a delay, until the EF86 and E88CC warm up.


Maybe the original REDD.47 was given HV with a delay, or maybe not.
Unfortunately, I could not find this information.

There is no minimum load-- the load is in parallel

Sorry, I can not understand the meaning of your message for my situation, which I described.
Those. is it possible or not in the original scheme REDD.47 - to turn on the heating of the lamps and HV simultaneously, without prejudice to Oa2?

vmanj said:

Sorry, I can not understand the meaning of your message for my situation, which I described.
Those. is it possible or not in the original scheme REDD.47 - to turn on the heating of the lamps and HV simultaneously, without prejudice to Oa2?

Click to expand...

Yes it is. The original REDD47 was designed to be hot plugged. This means you could pull one out of a working system with power applied and then insert another module in the same slot. So the new one had heater and raw HT applied simultaneously.

Cheers

Ian

But in the technical description to REDD.47 it is written:
----------------------------------------------------------------------
WARNING:-
The reservoir condenser in the amplifier is normally 80 uF and there is a further 44 uF plus the neon tubes closely associated.

On no account should an amplifier be plugged in to a live rack. Switch off the mains and wait for half-a-minute, otherwise the amplifier fuse will blow and there will be a grave danger of sputtering the gold plating on the McMurdo plug and socket.

Similarly, switch off and wait for half-a-minute before removing an amplifier, for the above reasons and because of the danger of shock. (Time
constant CR = 124 x . 470 = 58 seconds).
--------------------------------------------------

Also, I somewhere before read that to replace the REDD.47 during the studio session, it was necessary to stop the session and turn off the power of the entire console REDD.51.

I guess this was most likely possible in REDD.37 with V72 amplifiers, which had a power supply inside.

I am grateful to everyone who participates in the discussion of my question!
But still my question remains in force.

My understanding is that voltage regulator tubes are usually designed with a load in the form of a resistor down stream of the tube, otherwise they could conduct a nearly unlimited amount of current.
Look for those resistors, to answer your question about "working without load".

Thank you, but could you simplify this task for me?

Are these resistors 510R, 220K or 470K (according to the scheme) or did you mean something different?