RCA BC-6B Console Project

[MidnightArrakis]

@MidnightArrakis To keep clutter down, below here are two quotes from my previous power supply posts. (Click “view attachment”) It’ll be double this schematic, but instead of having two transformers I’ll have two 5R4GY’s feeding off of one toroidal transformer which is this Antek AS-4T360 AS-4T360 - 400VA 360V Transformer
And each 5R4GY will have it’s own 5V filament supply from this Antek AS-0505 toroidal which provides two supplies: AS-0505 - 50VA 5V Transformer
Each toroidal will get covered in 1/8” thick steel.

[here are two quotes from my previous power supply posts] -- I apologize as coming across as being repetitive, but so many of these threads go through vast amounts of updates of which not all of them are always posted or sometimes even mentioned!!! So, I need to ask again just to make sure that whatever is the most recent update is known. THANKS!!!

[It’ll be double this schematic] -- GOT IT!!!

[It’ll be double this schematic] -- Will you still be using the 24V output? Like for console relays, bulbs and the like? And, is the "Hum Adjust" still being used?

[It’ll be double this schematic] -- There is a handwritten note at the top of the schematic stating -- 7-Watt --. What does this reference to? And, are all of the resistors 1/2-Watt, except those called-out as being 1-Watt? Detailed schematics are always way more useful, ya know???

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[MidnightArrakis]

FYI:

https://www.tubesandmore.com/products/capacitor-ce-mfg-525-v-404040-f

https://www.studioelectronics.biz/sunshop/index.php?l=product_detail&p=1577

https://www.amazon.com/Cermant-Elec...ds=40uf+capacitor&qid=1706862589&sr=8-48&th=1

https://reverb.com/item/27737475-capacitor-ce-40-40-40-40uf-525vdc-electrolytic-pc-mount

https://www.caryelectronic.com/home...-axial-electrolytic-capacitor-audio-amps.html

https://www.justradios.com/cart.html

At least these are a start!!! Which one do you like?


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[MidnightArrakis]

BEST VALUE:

https://www.aliexpress.us/item/2251832534469687.html?gatewayAdapt=glo2usa4itemAdapt
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[MidnightArrakis]

[i need lead wires] -- And.....speaking of "wires" and with connecting your power-supply schematic to, I am assuming the RCA BC-6B console.....how are you planning on connecting these two items together? Are you planning on, A) Bringing in a multi-wire cable-harness from the console and connecting directly to the various points of the power-supply circuitry? Or, B) Bringing up a cable-assembly with a multi-pin connector and simply connecting the cable-assembly to a mating connector on the power-supply enclosure? If so, what type of multi-pin connector? MOLEX??? Amphenol??? Phoenix Contact??? JST??? TE Connectivity??? What???

And, since there will be two separate rectifier circuits, I am also assuming that there will be two separate multi-wire power-supply connector assemblies and cables???

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[MidnightArrakis]

Very interesting, inspiring, i almost forgot about the party you guys have here

[Very interesting, inspiring, i almost forgot about the party you guys have here] -- It looks like I must have ripped a smelly fart or I must have told a really bad joke because it seems as though that I am the only one here having any "fun" at this party!!! HELLO??? BEULLER? BEULLER???..... (with "Twist & Shout" by The Beatles playing in the background)!!!

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[My3gger]

OP might be calculating costs and time needed for labor intensive project like this. We already have simpler EZ tube mixer, replacing amps with RCAs should not be hard.

 

[systemtruck]

Have a bunch of related parts and devices on the way already, including a regulated high voltage supply/system so that I can start testing tube circuits without building the custom (unregulated) supply first. Taking a pause on custom power component conclusions for now. Did order the Hammond 518-0920 though. Am assuming it is enough space for heat dissipation, and will drill holes for venting. One thing I’ll need to decide is whether or not the rails will all be created in external supply or in the main unit. Advantage of them being created in main unit are… Simple high voltage cable from supply, as opposed to like 10 rail leads/wires. Caps all in main unit, probably best to have them local to circuits? Lots of open space in power supply.

 

[Xida]

I am currently restoring a BC 5A! This is a very good thread.

If you want to group buy anything or fab some PCBs…

 

[beatnik]

Do these have the same circuit in the program amp ? (single ended 6V6 with feedback from the output transformer tertiary)

It would be great to know the specs of that output transformer (RCA p/n 46098)

 

[systemtruck]

I’m getting back to this project and am settling on the mixer bus details….

RCA has a feature that I’d like to eliminate, which is the option to use the console in “mono” mode. In this situation, both mixer preamps are sent to a common line via 18K resistors and this common line feeds both PGRM amps.
I’ve interpolated the RCA BC-6A schematic into a more clear arrangement here below. This is shown in mono mode, and the 3-part switch changes it to dual (aka stereo)

I am not that great at evaluating the gain of tube circuits still, or adjusting gain for them without messing up bias. So I wanted to get some advice here.

Using an online calculator i calculated each tube stage gain as is.
I could be wrong, but if we’re to convert this mixer setup into a typical stereo mixer, and not use this “mono” mode common bus and gain loss accordingly, wouldn’t it be desirable for signal/noise ratio to kill the extra gain in the PGRM amps and also kill the voltage divider before the PGRM amps? I believe this voltage divider was put in place during dual mode in order to keep the gain the same (down a bunch) as mono bus mode. And then, the PGRM amp has extra make-up gain that isn’t really necessary if there isn’t any gain loss from a bus/divider before it….

If all of this is true, how much gain would make sense to lose in the PGRM design, and what values would be good?

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