Philco 'Alabama' - NZ Model

Philco 401 'Alabama' Front

Philco 401 'Alabama'

Philco 401 'Alabama' Rear

I found this in my Dad's things after he passed away and decided to get it working again.  A search of Google only turned up photos of the finished radios - never a circuit diagram - so this I created from scratch by tracing the circuit and drawing it out, then re-drawing it... then re-drawing it again until it looked about right - then I used Eagle Schematic to draw it neatly.  Its possibly not completely right, and I have seen some chassis' that looked different so there are quite probably multiple different sub-models of this radio - but it should be a good starting point if you're working on one.

Philco 401 Alabama circuit schematic diagram

Download the circuit by clicking here

First a little troubleshooting - I checked the output transformer and it was open circuit in the primary winding... this is something I have encountered on a few sets.  I actually unwound this one to see how it looked - and there were about 20 green spots - corroded copper - throughout the layers of windings... it wasn't repairable but I'm thinking I might use my microcontroller skills to make a transformer winder to start repairing them by replacing the primary windings with all-new copper since new transformers are very expensive and I have plenty of old reels of enamelled copper wire... a job for another day.  I also discovered a couple of dry joints - one in particular on one of the IF transformers that honestly looked like it had never been soldered at all and was only working because the wires were wrapped around the contact!  The main dropper resistors on the power supply were also cooked and so these were replaced with higher wattage versions.  I also fitted all new caps where they were electrolytic or wax since those were almost certainly shot (these types of capacitor fail over time and should normally be replaced on a radio that is 50-60 year old or more).  

The actual construction is cheap and nasty in my not-so-humble opinion - The Philco Alabama was manufacturedby Dominion Radio & Electrical Corp Ltd (Dreco) in Auckland between 1956-1961, and the brand went out of favour around this time.  I don't know why that was, but if the construction of this little set is anything to go by then I have my suspicions.  The brand was apparently replaced by Majestic - I have a stereo Majestic set with a similar chassis to that of the radiogram my Dad had when I was a kid - something I spent hours playing records on when I was little (I'll do an article on that when I have time).  In the top pic you can see its what the Philco set is sitting on.

Anyway, I also restuffed the main smoothing cap canister - so it looks factory but has all-new 450v Nippon Chemi-Con electrolytics inside it.  The EZ80 rectifier tube has a maximum smoothing capacitance of 50uF, so I used 47uF caps in place of the 40's and a 22uF in place of the 20.  This maximum smoothing capacitance value (generally found on the datasheet) is important to follow, as too much capacitance can damage the tube (I believe its by taking too much to 'fill' on turn on).

Philco 401 'Alabama' chassis before

Chassis before any work

Philco 401 'Alabama' chassis after done

Chassis after refurbishment

I cleaned everything up - I wish I had a photo of the case from before I cleaned it - it was black in places and full of all kinds of nasty substances - some of which appeared to be from the inside rear end of a rodent or two... A hose out (carefully to retain the serial number label glued inside), then a thorough wipe out, then a clean with some IPA to remove stubborn dirt and finally a polish with industrial hand cleaner (cream-based, not a heavy grit type) has it looking pretty darn good... apart from the missing corner - I may try to rebuilt that at some point, but that will almost certainly mean I need to repaint the cabinet, which I want to avoid.

Anyway, it works well now.  A bit of frequency drift once it warms up - which means retuning it after about 10 minutes - but other than that its going well.