[Milsurplus] Navy RAL Questions

[Kenneth G. Gordon]

On 17 Mar 2018 at 20:02, Joe Connor via Milsurplus wrote:

> 
> Guys, I have a question -- probably the first of many -- on a Navy RAL that I 
> picked up at a swapmeet today. 

Ah. Good on ya.

> When I got it home and took it out of the case, I found that it had been the home 
> to a family of mice who left many calling cards. Quite a mess. I figured there was 
> no way I would ever get this set working again, but I figured what the hell and 
> hooked it up to a good Navy power supply. Damned if it didn't work. Go figure.

Ha ha! It figures! What sort of power supply are you using, Joe?
 
> Here's my question: my filament voltage is low, about 4.8VAC.

Interesting! How and where are you measuring this? At a tube socket, or somewhere else?

> The power supply 
> is putting out more than 6VAC, and I used 16-gauge wire for the filament 
> hook-up. As I look at the schematic, there's not much in the filament chain. 

Correct.

> There's an AC voltmeter (not working at this point), but disconnecting it didn't 
> increase the voltage.

Hmmm....why is the voltmeter not working? Is it really in the circuit?

> I disconnected the two leaky AC bypass caps, and that 
> gave me an added 0.2VAC. The B+ and screen voltages are good. 

Please understand that the B+ should be no more than 180 VDC as I remember it. The 90 V 
regulated is to feed the detector, but, in fact, there are a series of resistors connecting the 
90 V connections back to the B+ input, so that if you don't have the two voltages, you can 
connect one, ranging from 180 VDC down to 90 VDC and everything still works. The main 
reason this was done this way is so that the receiver could be powered from batteries.

> Any ideas? Might dirty tube pins do it? I haven't run into this before; usually 
> filament voltage is the one voltage you can count on to be right. 

Yes.

Have you measured the filament voltage at a tube socket?

> I've attached the link to the manual, and the schematic is on p. 56.
> http://bama.edebris.com/manuals/rca/ral/
> 
> As always, thank you for your guidance.

I'll look at my schematic here and see what I can suggest.

Carry on.

Ken W7EKB

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