After some repairs to the leather case and a general cleanup of the plastic case I was preparing to re install the circuit board in this set. The radio is working well and nothing seems to be getting hot. As part of a final inspection I tested the current draw. The radio was being powered from my home made bench supply. This consists of an old PC power supply connected to a panel on my workbench that I had modified to provide the usual output voltages and also has a buck boost dc variable power supply for other voltages up to about 40v dc. It has been really useful so far. When I run the radio from the variable supply (4.5v 200ma current limited) it shows a current draw of 150 milliamps. This seems really high to me. I am unsure of how accurate the metering is in that small variable supply . The spec sheet says output ripple(vpp) is typically 150mv. And current accuracy is +or- 0.5% + 3 word (whatever + 3 word means?). Suspicious of the variable supply current reading I hooked up my digital multimeter in series with the power inlet and it read 75 milliamps. The funny thing is the variable supply now read 72 milliamps with the multimeter in circuit. So I am left with not knowing how much power this radio is drawing. And I am confused as to why the power supply now reads half what it did without the multimeter in circuit.
Even if 75ma is correct I think this is still too much current draw. Is this right? And if so how would I go about finding the problem?

Current draw seems far too high.
Would expect with volume at minimum to be less than 20mA.
With volume flat out maybe peaks of 60mA.
Your switch mode supplies may not be producing pure DC filtered.
Effecting accurate measurement, with modern digital meters.
Use some batteries, with say a 10 ohm resistor in series and apply ohms law.
Half a volt across the resistor should represent 50 mA.
JJ

Thanks Johnny. I just completed a few tests with the 10 ohm resistor as you suggested. It seems my multimeter is the problem. Using the multimeter in series with a 1.5 volt battery and a 10 ohm resistor I get 75ma of current draw instead of 150ma. When I use my power supply with the same voltage and resistor I get 142ma. The multimeter seems to be indicating approx half the current draw that it should be.
At least I have now established that the power supply meter is in the ball park for accuracy. Which leads me to my next question. What is causing the radios' excessive current draw and how do I go about finding the problem? Any suggestions would be most welcome.

Probably, a leaky transistor or incorrect biasing.
Suspect driver or output pair.
Disconnect them and note current draw, guessing radio part will draw around 10mA.
I tend to find suitable replacement transistors from wrecked units.
JJ

That makes sense. This set was in a pretty bad way from corrosion. I have replaced quite a lot of components. I replaced the output transistors with silicon BC548's. The old ones were germanium so to get the new ones to turn on I changed the base resistor from 1.5k down to 180ohm. This seemed to give about the right base to emitter bias and the set worked quite well after that. I think I need to re visit how I go about getting the correct base to emitter voltage drop. In any case first off I will do as you suggest and at least try to isolate the high current draw to the output stage. Thanks for the help so far.

Spot on Johnny. When I took the voltage off of the output transistors the current draw dropped to about 10ma. After some experimenting with the base resistor I found that with a 270 ohm in place the set worked properly and the current draw with no station tuned was steady 25mv. I also found a less than good solder joint which I fixed as well. This could have had some effect. The base to emitter is now 0.6 volts and reception is clear and loud. So this one is all but done. Just waiting for the replacement speaker and it can go back together. Thanks again to everyone that gave me guidance along the way. I now have an old transistor radio that has cost me more than twice what it is worth but the experience gained is priceless. I have already started looking for another one.

The germanium output transistors will be PNP so you will need BC557s!! (or the 35 volt version, BC558)
It's amazing the BC548s worked at all!

To set the bias, consider wiring in a temporary 10k pot to replace the two existing components. Adjust it so that on no signal the current draw just starts to rise, then back it off.

Disconnect and measure the pot and you will have your bias resistor values.

Ian the output transistors were actually NPN. The schematic shows them as NPN and I double checked them after removal. Brad has put a link to the schematic on page 1 just below the pics. I do remember you cautioning me earlier on about this issue so I was focused on checking. Thanks for the tip about the variable pot for bias resistance measurement. I will have a play with that while I wait for the replacement speaker. I may be able to optimise the bias resistor even more using your method.

NPN germaniums exist of course but they are not common,

I would have expected a radio like this to use cheap jelly-bean PNP germaniums, there is absolutely no reason not to given full transformer coupling.

A great learning exercise. Well done!