RCA BX 1D/E power supply schematic

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jslstudio

Well-known member
Joined
Aug 21, 2010
Messages
118
Hello,
Does ANYBODY have a schematic for the RCA BX1D or E power supply? Used to power the RCA BA 11A and a few others.
Have searched high and low for the schematic!
If anybody has a link or schematic would really appreciate!
Thanks!
John
 
CJ said:
check the primativo voltage regulator, wtf?  better have a wire wound pot in there

And also note the small heater elevation voltage circuit, This will raise the heaters by about 18V from a 300V supply.

Cheers

Ian
 
CJ said:
check the primativo voltage regulator, wtf?  better have a wire wound pot in there

Thanks a BUNCH!!!!!!!! Much appreciated!!!!!!!
awesome!
Also has anybody been running higher heater voltages for quieter operation? David Kuka  said service bulletins from Altec and RCA recommended higher heater voltages for quite operation..?

Thanks again!
John
 
jslstudio said:
has anybody been running higher heater voltages for quieter operation? David Kuka  said service bulletins from Altec and RCA recommended higher heater voltages for quite operation..?

That's not something I've ever come across, in fact the opposite is apparently true in many tube microphones.    I've run many 6.3V tube systems on 5.8-6V, with no obvious change in noise.  Input stage tube selection remains vastly more important. 
 
jslstudio said:
Thanks a BUNCH!!!!!!!! Much appreciated!!!!!!!
awesome!
Also has anybody been running higher heater voltages for quieter operation? David Kuka  said service bulletins from Altec and RCA recommended higher heater voltages for quite operation..?

Thanks again!
John

I seem to remember reading in the RCA tubes book that running tubes at elevated heater voltages (up to twice the nominal) can eliminate some sources of noise during production, but the tubes are still expected to be run at the nominal voltage in use.

Cheers

Ian
 
ruffrecords said:
I seem to remember reading in the RCA tubes book that running tubes at elevated heater voltages (up to twice the nominal) can eliminate some sources of noise during production, but the tubes are still expected to be run at the nominal voltage in use.

Cheers

Ian

I stand to be corrected, but I don't think the filaments are being run at higher voltage here. It just looks to me like an elevated DC reference. (Instead of  referencing the center wiper of the humdinger straight to "ground".) The filaments will still be at 6.3V AC, just floating on the DC reference.
 
It can help you out if you have AC noise in the filament circuit. I first noticed this kind of thing on old 60'S Ampeg amps, but they usually took the DC from the cathode side of the output tubes.  The potential divider across the HT as shown here is the way I tend to implement it.
 
tony hunt said:
I stand to be corrected, but I don't think the filaments are being run at higher voltage here. It just looks to me like an elevated DC reference. (Instead of  referencing the center wiper of the humdinger straight to "ground".) The filaments will still be at 6.3V AC, just floating on the DC reference.
 
It can help you out if you have AC noise in the filament circuit. I first noticed this kind of thing on old 60'S Ampeg amps, but they usually took the DC from the cathode side of the output tubes.  The potential divider across the HT as shown here is the way I tend to implement it.

I think we are talking at cross purposes probably due to me using the word elevated in two different contexts.

Elevated heaters usually means raising the dc potential of the heaters as a whole above 0V using a pot divider as you said.

Someone else talked about raising the actual heater voltage above the normal 6.3V because it made the tube noise less. I said that in manufacture they sometimes run the tubes at heater voltages above 6.3V (sometimes up to twice the nominal value) as this gets rid of some noise producing defects - but you should still run the tubes at the normal heater voltage.

Cheers

Ian
 
From an offline conversation, I believe the OP meant biased, not basic voltage raised. 
 
> in manufacture they sometimes run the tubes at heater voltages above 6.3V (sometimes up to twice the nominal value)

In production, heaters are run HOT to activate the cathode. (Break-down oxides to raw metals.) Yes, even double-voltage.

Much of this happens on the pump, so the stray gas released is swept-out. You really don't want to cook the tube once sucked and sealed, it can go gassy.

I have never heard of high heater voltage to reduce audio noise. Low voltages are often used. When tubes are worked far below their ability (0.5mA in a 2mA tube) it does no harm to go a little low, like 5.5V.
 
remember this?                   

"Rejuvinating CRT's

The following artical is largely as it appeared in the book "TV Data Publications" in 1966. The voltages involved are potentially lethal and hence the procedures used should only be attempted by people with suitable experience of such voltages.

During the life of a cathode ray tube, the cathode emission will fall gradually. Eventually this slow deterioration will reach a point where it begins to have an adverse effect upon the brightness of the picture. Providing no other defect has developed within the tube, it can probably be rejuvenated when it reaches this stage by one of two methods.

The first is perhaps the simplest method and is the one most likely to give the best results. It is to increase the heater voltage by about 15%. This may well extend the life of the tube by several months, whereupon a further small increase to, say 25% may be tried. Generally, these increases in heater voltage will provide a very worthwhile extension in the tube life, and only in a few isolated cases will the heater wire fuse due to the overload. C.R.T. "booster" heater transformers are commercially available, their function being to increase heater voltage in this way. They may be temporarily plugged in between the receiver circuits and the tube base.

The other method of rejuvenating tubes is the procedure which is usually termed "reactivation". This involves temporarily overrunning the heater whilst, at the same time, a positive potential is applied to the tube electrodes. The result of this procedure is that a new supply of emitting oxides are formed on the surface of the cathode, and the tube should then be good for a further period of use under its normal working conditions.

A simple reactivator could consist of a heater transformer which is capable of providing a voltage which is about 30% in excess of the working heater voltage of the tube. The positive potential for the electrodes is obtained from a separate power supply, or directly from the a.c. mains via a suitable rectifier and potentiometer. This voltage is fed to the tube electrodes via a current limiting resistor and milliammeter, the complete circuit being shown below:-

Diagram for a CRT Rejuvinator [4K]

These supplies are fed to the tube which is undergoing treatment, and if the procedure is going to be successful the emission will be initially very low, but will rise gradually until it reaches a peak as shown on the meter. The time required for this part of the operation may be anywhere between a few minutes and an hour or so, but once the peak has been reached, the reactivator should be disconnected and the tube heater run at its normal voltage for at least half-an-hour with no voltage on the electrodes. After this, the tube may be returned to its normal operating conditions and, if the exercise has been successful, a good picture will be obtained.

The procedure outlined is not that dissimilar to that used during the production of cathode/CRT at the factory. If you want all the heavy details, then refer to the artical "The Materials and Shapes of Vacuum Tube Heaters" elsewhere on this site.

It will be appreciated that success cannot always be expected in repairing tubes which have poor emission, but as the tube is useless when it reaches this stage, there is everything to be gained in making an attempt at prolonging its life."
 

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I find tubes pretty amazing still to this day..with all of the little filaments and wires...And heat/cold cycles...still pretty darn amazing they last as long as they do!!!!!!!

 
CJ said:
remember this?                   

"Rejuvinating CRT's


The first is perhaps the simplest method and is the one most likely to give the best results. It is to increase the heater voltage by about 15%. This may well extend the life of the tube by several months, whereupon a further small increase to, say 25% may be tried. Generally, these increases in heater voltage will provide a very worthwhile extension in the tube life, and only in a few isolated cases will the heater wire fuse due to the overload. C.R.T. "booster" heater transformers are commercially available, their function being to increase heater voltage in this way. They may be temporarily plugged in between the receiver circuits and the tube base.

I certainly do remember.

It is not a complete collection, but these three covered most situations. These boost filament voltage, and the big one is isolated, possibly for working around a cathode to filament short, but that never came up.

Male to female connectors inline for the picture tube, boost the filament voltage, all other pins connected straight through.  Brighter tube. For a while. Dates back to our TV repair shop days in lower Pangaea.

Gene
 

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