[NostalgiaRadioTime]

I picked up one of these tiny consoles that uses a Warwick 5 tube chassis recently and found someone in the past (who tried recapping it) majorly butchered it to the point it's going to require a full schematic tracing to get some sound out of it. There is no audio output at all. To further complicate things, there are two schematics, one for a 510 C and one more generic Model 5-tube chassis that are basically the same, but with a few subtle discrepancies.

http://www.nostalgiaair.org/PagesByMode ... 023105.pdf

http://www.nostalgiaair.org/PagesByMode ... 023102.pdf

Compare the volume control on each. It appears that the potentiometer is R7 on the 510 C chassis, but on the 5-tube chassis schematic, it's R8? On the 510 C chassis R7 is 500K, and on the 5-tube chassis schematic R7 is 250K, which I believe is just a standard resistor and not the potentiometer?

One of the few solder joints that looks original also doesn't correspond with either schematic. Using the tube pin out, it appears that both C4 and R4 should be going to pin 4 on the 6D6? On my set, pin 4 and 5 of the 6D6 are joined together and C4 and R4 are physically going to pin 3 on the tube socket.

[Joe Rossi]

Greg,

Does your chassis have a 6G5 tuning eye? If so, you have the 5/6-tube radio, Riders 9-1. If not, then measure the value of the potentiometer. If it is around 500K, then you have the 510C; if it is around 250K you have the 5/6-tube radio. Both schematics show R4 and C4 connected to pin 4 of the 6D6. IMO that is where they need to be. Pin 3 should be connected to the IF can, as they show in both schematics. Check for other differences and let us know. Warwick also made a model 530 & 551 which have the same tube line-up. Hope that helps!

[NostalgiaRadioTime]

Thanks for that, Joe. No mine has no eye tube.

Well here's an interesting plot twist. I finally got to hear the radio play tonight, but only by changing ALL of the tubes!

Here's what happened. When I got this radio, I searched for mini console Baby Grand, and found a thread about it over on ARF:

Ah ha! I now had the information I needed to find a schematic! It was either the Warwick 5 (or 6) tube chassis schematic, or the model 510C chassis. I printed them out and found that the chassis configuration (tube layout) matched. Bingo!

Upon removing the chassis, I found that the two large tubes were actually broken. Half of the glass was missing. And the other three rattled like maracas. So I removed them, and knowing they all were bad, put them aside and found the correct (or what i THOUGHT were correct) tubes: the 80, 42, 75, 6D6, 6A7.

So that's when I noticed the discrepancy between the volume control layout. I got NO sound whatsoever when I had it wired per the 5 & 6 tube chassis schematic, so I rewired it to the 510C chassis layout. STILL no sound. And voltages were way high. I began to suspect the power transformer was bad so I did some testing. With all of the tubes out, under power I got 2.5 volts across the heater pins on each tube. That made sense why I was getting no sound.

So I started digging around for a different power transformer when the light bulb went on. Could it be that this thing was wired for 2.5 volt tubes? I went back and looked at the tubes I pulled out and found a 2A5, 2A6, 2A7 and a 57. So I found and tested each of those from my tube stash, figured out which corresponded to the 6.3 volt tubes I had installed, replaced each, powered it up and it actually played well!

So here is the tube layout with the 2.5 volt tubes listed in red:

   

And here's the label on the back of the chassis:

   

Now my only concern is that some of the resistor values are different from the Warwick 510C chassis to whatever chassis I have now. Can anyone locate a Warwick schematic with the same chassis layout and 2.5 volt tube configuration?

Upon closer inspection it appears the transformer MAY have been replaced once in the past, as the screws and nuts holding it to the chassis are newer and shiny. So maybe the person who changed it only had a transformer for 2.5 filament voltage and just subbed the tubes on his own. It's a mystery!

[Joe Rossi]

Greg, Glad you solved the mystery. I searched the Mallory-Yaxley database at grillecloth.com. The only radio that had those tubes was a 16-tube radio made by Capeheart. Cheers!