Gents, Am working on a AWA 453-P battery portable and so far have replaced nearly all the resistors and caps, only a few micas still to be replaced and one or two resistors.

Which measure reasonably well but will change them anyhow.

Another batch of components has been ordered and will turn up in due course.

Progress has been made the set now receives which it did not beforehand.

However it is generally rather insensitive, measured the d.c resistance all of the coils, all match up pretty well with a chart in the manual except for the primary of the M.W R.F coil which measures 38 ohms instead of 80.

Measured voltages and the 1R5 converter gives some odd readings.

The radio is equipped with a Max or Medium switch for extra sensitivity in bad signal areas.

Have noticed that the screen grid V does not change when the switch is actuated, much the same for the anode V.

As well the grid bias V which should be 0 according to the manual gives a reading of -4.5v.

Using a 33k ohm/Volt multimeter.

There are still some grotty black bitumen encapsulated micas to be changed.

Have measured the mica coupling the control grid to the coil with a multimeter (best I can do) and it is at least not shorted.

Again extra caps are on the way but in the meantime any thoughts on the grid bias readings I have obtained ?

Measured the other valves parameters and apart from low readings on the grid bias of the 3V4 o/p valve they seem to be pretty ok.

Thanks

One must be careful as to where they replace Mica's:Mica's here are fairly reliable & most of us never bother them. I only test them for leakage if I happen to have it out of circuit on one end. Only once have I had to replace all Mica's in an Australian set (Lightning). Any component "Micamold" USA, toss it.

You will read in HMV data that once you have changed components in the RF section, you should re-align it. Once you have changed parts it can throw everything out of whack and the set becomes deaf. A poor antenna and being inside a metal shed also adds to the attenuation.

The first move after you stop changing things & get it going: Align it... then we will see if it's still deaf. Do not feed a mass of signal down its throat, as that will cut in the AGC (where fitted) and you will never peak the coils properly.

What meter did they use (some times on the sheet)? Probably 1000 opv? 33K opv will not load the circuit as much. A DVM will likely give a higher reading again.

I always check resistors as I replace caps, that saves rework & grief later. I also consider it pointless to fault find a set until such time as I have at least got rid of wax paper caps & old electrolytics.

Methodology is important.

E.g. I have a Tasma (1103) on the bench which I did not bother to plug in. the rubber filament wire has failed, more than any other as it is under rated for the current. Five resistors have already been changed out and as I noted elsewhere one had snapped off. One of the non original filter caps is also noted leaking. Three Mica's tested, not changed.

I am waiting parts (ran out) but it would be likely that there would have been ramifications, if turned on from what has been picked up on: Pointless & Dangerous It would not have worked.

Marc

1R5's can have some strange peoblems that only show up under operating conditions.
Have you swapped the 1R5 out for another one yet?
Also the resistance reading on the coil concerns me, unless its somehow switched in parallel with another coil or a low resistance.
Not having a schematic here, I am guessing.
FrankB

Thanks Mark and Frank for the guidance so far, as yet have only replaced one mica, a coupler from one IF stage to the other.
In the R.F amp and Mixer have only replaced the paper caps and resistors.
The micas around the osc and r.f coils are still there.

All other papers and resistors have been changed. A lot of the resistors were well out of whack.

Must admit I'm a bit wary of these micas after a event with a Ferris M94. As has been remarked it depends whether they have a high voltage applied or not.

The set is very insensitive with its frame aerial, only picks up the local radio station which is only a few K's away.

If a length of wire is clipped onto the input matching coil quite a few local stations can be heard.

Although I would have expected better from a 5 valve radio.

The manual does not specify what meter the voltages were measured with, yes modern high Z meters will give higher readings. May be on a wild goose chase.
Have tried another 1R5 with no change.

Have noticed my filament battery is running down so when the blistering 36 C (40 C in the shed) abates will go out and get some fresh ones.

In my limited experience, that antenna is pretty good, so I would guess that the antenna coil or IFT may be enough out of alignment to suppress the sensitivity. Some AWA portables (including my 679-based Hotpoint) have a 3-gang tuning condenser, of which one gang adjusts the loop antenna resonance ahead of the antenna coil. But if alignment is off, the loop antenna tuning won't work. The random wire antenna will deliver higher signal but less selective.

Maven

Thanks for the further comments and there is a three gang tuning capacitor. Looking at the circuit diagram the loop aerial is fed to the first gang via a ferrite adjustable coil with a variable trimmer capacitor.

These I think would be first port of call in a re alignment.

However the loop aerial has been a bit battered by battery changes over the years so shall tiedy it up bit and make things a bit more secure.

Just bought fresh alkaline cells but will wait till the evening, its still 40 C in the which is a bit fearsome for bench work.

I forgot to mention that when I lifted the chassis out of the case it was evident someone had been working on this set.

Solder lugs around the first I.F were sploged and when I tried to align the loop aerial matching ferrite coil and trimmer cap found someone had broken the alignment screw of the capacitor which has long disappeared.

Luckily had a AWA 528M of similar vintage from which another trimmer cap was borrowed from and at least was able to match up the loop aerial.

The set still displayed very poor sensitivity so rustled through my spare valves and started changing all valves one by one.

To my pleasure upon replacing the 1T4 second IF the set burst into life with surprising sensitivity. A number of local county stations heard strongly along with a few Sydney stations coming through faintly on the loop.

Still a bit of tidy up work and have to sort out SW which hopefully will not be to many problems.

Solder wick is still something that can be used in valve sets, to suck up & run off great blobs of solder. Also makes good braid for earthing. "Goot" is one of the better ones.

When aligning the Mechanical's (position) of the dial is first, then IFT's; followed by the oscillator. If the padder is not correct at the low end it will seriously impinge on getting the tracking right.

If the SW has any of 2.5, 5, 10, 12, 15MHz Then you can use them as the reference. WWVH & WWV are standard frequency & time signal transmissions.

Marc

Have a spool of brand Plato solder wick which works well, also a Soder Pult, a handy device if I could find the thing after a recent house move.

After my last post set the disassembled radio up on a bench outside and could hear the 7.00pm 2CH news faintly but readable.

Other Sydney based stations were heard as well, considering I am at Bathurst out in the country this is not bad performance.

Aligned the loop matching tank as mentioned with sig gen set up with a loop of wire and multimeter on the output valve.

2LT Lithgow comes in very clearly and listened to some of the old 60/70s music for quite a while.

Re the Tasma with rotted wiring, I have a Astor mains/battery portable which has such rotted wiring it would be a suicide box if it was plugged in to the mains.

Think it will be a long time before I attempt a complete rewire to get it going.

I think that there were four grades of rubber, ranging from a good waxed type, to what appears to be crap. By the looks of it it may have had something to do with supplies during war, but several manufacturers seem to have used the crap version.

Astor & Tasma are not alone, in being ones I have had to rewire. Most of the damage in the Tasma seems to have been caused by some over zealous Tarzan doing the loop ties up so tight that it has cut into the insulation and by using too low of a guage of wire on the filaments & heaters.

This oversight has heated the wire causing it to go brittle & split: A short was on the way (time bomb). A Brevillle mentioned some time ago, would have suffered damage if it was powered, as the insulation was already lost on the heaters (some idiot had tried to glue some of it)?

Wire guage is clearly something to watch in the Tasma's and when you are rewiring. I have used a thicker solid heater wire and taken some load off the wire, transformer end, by feeding the OP valve separately.

Marc

Something to keep well in mind as these sets are getting older and older.

The 453 is 65 years old, the 528M ? I removed a trimmer from would be about the same vintage and the internals of that were a horror of greatly aged electrolytics, black paper capacitors and dubious rubber wiring.

On a Airzone the insulation of the power lead at the plug was spit of and the bare wire was clearly visible so cut the power lead of as a safety measure.

The Astor mentioned has a jack for a electric jug type plug and one of the wires from the jack going to the transformer has lost its insulation and is bearing up against a sharp edge of the chassis.

Mains being applied to this would have resulted in a live chassis with a real safety hazard.

Yet there are some whom persist in powering up these aged sets and try to carry out "fault finding exercises".