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Boater Sam · 4th May 2018, 8:57 pm

Bought, with real money, another Ekco A385 transistor portable. Produced from September 1959.
I've had a few of these in the past, they have all worked well and just needed cleaning.

The two 6v batteries are bit of a pain as they are no longer widely available but there is plenty of room for a double stack of AAs or even good old HP11s, C types to younger members. Draw is only around 20mA at reasonable volume so they last well.

The first difficulty is getting the set out of its leather zip up case, they are a very close fit and the zip gets in the way. This one has a well worn case, the zip is partially detached.

Once out, it looks not bad, a bit grubby but the case is not cracked, the knobs are on, dials legible. Slow motion tuning spindle works.
Opening the 2 parts of the case reveals a clean interior, no batteries or spill damage but the top moulding seems loose, there is a screw missing from one end of the top chassis plate and the other is loose. Has this been played with? No obvious signs of repairs.
Many nasty Hunts 0.04uf capacitors, several 50uf electrolytics from the same stable
( were they made in a stable, is that why they are so bad? ) and a couple of Plessey red and blacks.
Speaker is good. One knob is cracked on the spindle moulding, superglue and a metal collar fixed that, the other has a small crack across the face.

On with the split power supply and oh dear, a box full of whistles, Medium Wave finds stations but the whistle kills them, they are quiet but selectivity seems good. Long Wave is a bit better, louder, but the whistle either side of the station is horrendous.
Obviously there is bad instability somewhere. The coil and IF transformer cores are sealed, the trimmers likewise seem undisturbed. Switches are noisy, but clean up OK.

Now these radios are a serviceman's nightmare to get access to all the components. The old Fairchild transistors are scattered around 3 sides of the multi piece chassis in no logical order as are the rest of the components with wires traversing to and fro around the piano key switches where more components are buried.
The battery boxes are stapled around a "U" shaped aluminium bar that slots into both sides of the chassis and has to come out for access by flexing it after removing the speaker.

A quick test of the audio stages by disconnecting the capacitor on the volume control shows these stages to be stable and working fine, so its instability in transistors 1 to 4.
Trader sheet 1585 covers this set. Now transistors 1 &2 are on the top near the switch bank, next to #5! Then #3 & #4 are on the side plate. Its unusual as there is a mixer and a separate oscillator transistor.

Ok, so what's causing the instablity? It will be those Hunts plastic caps for sure. The Plesseys will go too. And there are a few Suflex nasties buried in the switch bank. Change C47, C48, C44, C37,C53 ,C13, C24 one at a time. It gets a bit louder, Long Wave is better but the whistle is still there. Beginning to look like a bad one to sort.
I would have liked to change C42 and C34 but they are very difficult to get to and testing the removed capacitors reveals that though the values are elevated, signifying that they are slightly leaky, they should be OK in a transistor set with low voltages.

Thinking cap on, check the remaining electrolytics as they are decouplers and emitter bypasses, they are fine despite being Hunts. Read the instructions (well, circuit diagram) seems a good idea.
Now this reveals that there are components listed that are not fitted! Particularly C51 which is a 0.04uf capacitor decoupling the negative rail to the first 4 transistors. There is a 50uf already on this rail but the sheet says that C51 was also fitted to later sets.
So this is an early one, why did Murphy have to put an extra decoupler on that rail with later production? They did nothing if not necessary, never wasted money.

I fitted one and...........Whistles Gone! Volume back up to what I would expect, loads of stations on Medium Wave, job done.

Problem solved, a quick check on the tuning being in track, reassemble and clean and there is another old set back in working order.

Anyone want a few old Hunts and Plesseys, pre-used?

4th May 2018, 8:57 pm	#1
Boater Sam Banned Join Date: Dec 2013 Location: Middlewich, Cheshire, UK. & Winter in the Philippines. Posts: 3,897	Portable Murphy with attitude repaired. Bought, with real money, another Ekco A385 transistor portable. Produced from September 1959. I've had a few of these in the past, they have all worked well and just needed cleaning. The two 6v batteries are bit of a pain as they are no longer widely available but there is plenty of room for a double stack of AAs or even good old HP11s, C types to younger members. Draw is only around 20mA at reasonable volume so they last well. The first difficulty is getting the set out of its leather zip up case, they are a very close fit and the zip gets in the way. This one has a well worn case, the zip is partially detached. Once out, it looks not bad, a bit grubby but the case is not cracked, the knobs are on, dials legible. Slow motion tuning spindle works. Opening the 2 parts of the case reveals a clean interior, no batteries or spill damage but the top moulding seems loose, there is a screw missing from one end of the top chassis plate and the other is loose. Has this been played with? No obvious signs of repairs. Many nasty Hunts 0.04uf capacitors, several 50uf electrolytics from the same stable ( were they made in a stable, is that why they are so bad? ) and a couple of Plessey red and blacks. Speaker is good. One knob is cracked on the spindle moulding, superglue and a metal collar fixed that, the other has a small crack across the face. On with the split power supply and oh dear, a box full of whistles, Medium Wave finds stations but the whistle kills them, they are quiet but selectivity seems good. Long Wave is a bit better, louder, but the whistle either side of the station is horrendous. Obviously there is bad instability somewhere. The coil and IF transformer cores are sealed, the trimmers likewise seem undisturbed. Switches are noisy, but clean up OK. Now these radios are a serviceman's nightmare to get access to all the components. The old Fairchild transistors are scattered around 3 sides of the multi piece chassis in no logical order as are the rest of the components with wires traversing to and fro around the piano key switches where more components are buried. The battery boxes are stapled around a "U" shaped aluminium bar that slots into both sides of the chassis and has to come out for access by flexing it after removing the speaker. A quick test of the audio stages by disconnecting the capacitor on the volume control shows these stages to be stable and working fine, so its instability in transistors 1 to 4. Trader sheet 1585 covers this set. Now transistors 1 &2 are on the top near the switch bank, next to #5! Then #3 & #4 are on the side plate. Its unusual as there is a mixer and a separate oscillator transistor. Ok, so what's causing the instablity? It will be those Hunts plastic caps for sure. The Plesseys will go too. And there are a few Suflex nasties buried in the switch bank. Change C47, C48, C44, C37,C53 ,C13, C24 one at a time. It gets a bit louder, Long Wave is better but the whistle is still there. Beginning to look like a bad one to sort. I would have liked to change C42 and C34 but they are very difficult to get to and testing the removed capacitors reveals that though the values are elevated, signifying that they are slightly leaky, they should be OK in a transistor set with low voltages. Thinking cap on, check the remaining electrolytics as they are decouplers and emitter bypasses, they are fine despite being Hunts. Read the instructions (well, circuit diagram) seems a good idea. Now this reveals that there are components listed that are not fitted! Particularly C51 which is a 0.04uf capacitor decoupling the negative rail to the first 4 transistors. There is a 50uf already on this rail but the sheet says that C51 was also fitted to later sets. So this is an early one, why did Murphy have to put an extra decoupler on that rail with later production? They did nothing if not necessary, never wasted money. I fitted one and...........Whistles Gone! Volume back up to what I would expect, loads of stations on Medium Wave, job done. Problem solved, a quick check on the tuning being in track, reassemble and clean and there is another old set back in working order. Anyone want a few old Hunts and Plesseys, pre-used?