Collins 6R

[valco]

Hi

I just recently acquired this Collins 6R, but it comes without a power supply. So i have some questions i hoped some of you where able to answer.

The power supply needs :
6.3 v ac or dc at 1.2 amps
180 to 250 v dc at 20 ma

Could i build a power supply by using these :

https://no.mouser.com/ProductDetail/International-Power/IHB200-012?qs=0xCm9DOQnC7%252BW4SCa00vHA%3D%3D

https://no.mouser.com/ProductDetail/Triad-Magnetics/F-16X?qs=b1anAsPanWzPazOh%2FLHHJg%3D%3D

It needs to go from 230v since i´m in europe

 

[valco]

The backside

 

[mjrippe]

The Power One will be fine for B+, but the Triad only has a 115v primary and you say you need 220v.  This one from Hammond would be good:
https://www.mouser.com/ProductDetail/Hammond-Manufacturing/266JB6?qs=HMhDvBYWqvPX%2FCwaL6nHJA%3D%3D

 

[valco]

The Power One will be fine for B+, but the Triad only has a 115v primary and you say you need 220v.  This one from Hammond would be good:
https://www.mouser.com/ProductDetail/Hammond-Manufacturing/266JB6?qs=HMhDvBYWqvPX%2FCwaL6nHJA%3D%3D

Thank you for you remark about the triad. I overlooked that detail.

The preamp comes wired to 600 ohm impedance , but has options for 150 and 20000 ohm. What would be the best choice to make it acceptable for most mics ? Or should i install a switch ? 20000 ohm should equal high z impedance ?

 

[emrr]

Thank you for you remark about the triad. I overlooked that detail.

The preamp comes wired to 600 ohm impedance , but has options for 150 and 20000 ohm. What would be the best choice to make it acceptable for most mics ? Or should i install a switch ? 20000 ohm should equal high z impedance ?

Those are line amps, it’ll work with a mic but you can’t optimize it unless you replace the gain control with a higher Z.  So use 600. 

 

[valco]

Here´s the schematic

So, if i understand this right: the 25k pot could be replaced with a 100k to make it more efficient? Or does the circuit lack the gain to work properly as a mic preamp ? 

 

[emrr]

Listen to the 25k and see what you think.  100k more optimal on paper, 50k would be better too.  Plenty of gain. 

Consider looking for a 6P instead if you want something for microphones.  6R is excellent additional gain after another preamp. 

 

[valco]

I finished the power supply and have had it running for some time now, but I´ve had some trouble with the led I installed in the power supply. Installed another lamp yesterday and wired it with the 6.3 ac filament supply, but when i measure the filament voltage going into the collins it measures 5.8 volts.

Is this a huge problem or will it work fine ? 

 

[emrr]

Not a problem.  Measure at the PSU and also at the preamp.  If there's much drop, consider larger filament wire. 

 

[valco]

It measured 6,1 v at the power supply and 5.9V at the preamp. So I assume from your comment, EmRR, that it's not a huge problem when it's not too far off from 6,3v?

 

[radardoug]

Its 6% down on what it should be, and 3% down due to wiring. Doug suggested thicker wires, probably a good idea. But its not the end of the world, its a nominal voltage and probably not affecting the circuits performance.