I've tried all the suggestions offered in this thread https://vintage-radio.com.au/default.asp?f=2&th=716, but the Philips Radioplayer 179 still fails to select the audio properly. The tuning scale tracks properly, voltages seem to be correct. Repeated alignments have not corrected the problem.

I'd be interested if anyone can suggest what components or procedures should be checked to correct the problem recorded in this video of a reception test (MW only).

The video should play in any browser once it downloads - and there are no ads or nasties in it.

https://vimeo.com/195378026

Maven

OK, Have had a look at the video.
It would seem that something is "taking off" , techs term for something that has got into oscillation.
Could be in any stage of the radio and the way to isolate the problem would be to go backwards from the audio stage.
Could be the IF or detector stage taking off. An open circuit cap or a wiring error.
Possibly a shielding problem.
Is the radio dead quiet when the first RF valve is removed?. Then the IF valve.
With volume turned up.
JJ

Hi Maven,

I would start at the beginning .... firstly, determine if the noise is via the antenna ..... or interference feeding into the radio from within your room etc ...... or is it being generated within the radio itself.

There are several ways to do this ..... for example, by trying the same antenna on different radios in the same location (or no antenna) .... should answer the first question. Can you relocate the radio to a different location eg to a different room or outside your house/shed etc to answer the second question. If 'no change' and 'no change' .... then the noise is being generated within the radio.

Then ..... assuming you have a Signal Generator and a Scope .... I would inject an appropriate signal into each stage of the radio to determine roughly which circuits are the problem. There are too many possibilities at the moment.

Cheers,
Ian

Do the necessary valves have thier shielding and is it connected to earth?

That does not sound like its internal, but we still have to prove that. That is the sort of noise I would expect from an NBN box, Computer, or even a switchmode power supply and a bank of LED lights run from a switch-mode PSU (Got one of them & it does that). I have had a FAX get into a 175kHz IF.

Try shorting out the antenna either with a 0.01cap or a lump of wire & see if it disappears? Shut off anything with a switch mode power supply & see if it shuts up? Even a Compact Flouro causes RFI, the regulators have totally lost the plot with RFI.

Marc

I would try to eliminate the question of local interference hash first.

In the other thread you say "cheap little radios in the same location don't pick up any significant distortion", however have you tried any other vintage sets in the same mains socket and location?

Another quick test is to try the set in another house -- maybe that of a relative or friend not living nearby.

Hi Maven, as soon as I heard the recording and noted the heterodyne beat whistles and background chirping as you tuned into stations I would say the other guys are correct. You have an adjacent transmitter drowning your set with RFI. In my workshop I have to turn OFF both my power invertor AND my security video recorder if I want to use my long wire aerial for AM reception. I can use any loopstick radio with no problems it is only the long wire radios that have a problem. Welcome to the brave new world.
The best way of finding out where the transmitter is, turn the !#$%%^ things off! This problem caught me by surprise as up until a year ago I had no valve radios and my workshop was all about industrial electronics. As soon as I started to play with long wire sets I had all that weird interference that in the old days would have a truck load of PMG and Radio inspectors on the case. Now they have just given up, Every piece of equipment has a switchmode supply or processor chirping away and the AM band is pretty useless. With your loopstick radios just tune off station and you will probably hear the chrping and warbles in the background with the volume turned up.

If you cant resolve the issue just take a transistor radio, power it from a non switchmode plug pack, plug the earpiece wires into your phono input, adjust your audio levels, the TX radio is now your tuner the Philips supplies the HiFi and have a nice day


Your only question to answer is if the "transmitter" in inside the set or outside it.


Inside means an instability by a bad bypass or bad valve shield.
Scoping the various signal points will reveal that.


Outside means some !#$%%^^&& piece of gear, Invertor, Power pack, Surveylance VCR, NBN box, Modem, Computor or God Knows What. Just turn them off one by one and see which one brings silence!

Cheers Fred.

Well, after all that and with thanks to many and varied advice - the problem has resolved itself. Reception is now strong and clean on most stations except the weakest, with just a minor background hash and not much between stations.

It resolved after I had moved the set to another location for testing and back again to the workshop, so I think the problem all along may have been a mechanical short that was cutting the antenna signal or compromising the tuning circuits in the RF section. Nothing wrong in audio section. Any suggestions on places to look for such a short? I won't poke around any more while it is working as well as ever.

In IF alignment, the Service Sheet instructs to do IF2 first, then IF1. Adjusting the secondary of IF2 does not appear to have any audible effect. Is that normal?

Maven

Hi Maven,

Any radios that I leave alone with a known fault always come back to bite me when I'm 'showing off' my latest handiwork to some-one ....

I would gently tap around the 'problem area' with an old knitting needle trying to re-create the problem .... coils, valve bases, solder joints, selection switches etc, and/or re-solder all joints, turn all knobs etc .... mechanical or intermittent faults are the most frustrating and difficult faults to find .... do you have a Scope?? ...... I would probe and record voltages and waveforms around the problem area .... do the same when the noise re-appears.

Re IF - alignment should be done backwards .... so with 2 IF stages, yes, IF2 first, then IF1, then repeat process ... 2 slugs in each IF stage (usually). I would expect a decrease in volume when IF2 is way off 'tune'.

Sorry to harp on about a Scope ... but alignment is much easier with Signal Gen and Scope .... Father Xmas is a good excuse for a great investment ....

Tinkera: feel free to harp away - we are approaching the season for heavenly choirs to let fly ;) .

Yes, I do have a scope (Philips/Fluke 30k digital) but am not expert in its use. Don't have a signal generator but wondering about acquiring one. Santa Claus unlikely to be sympathetic to such a request, but other means might be found.

I have previously prodded around pretty thoroughly for loose joints. Prime suspect now would be valve bases. A couple of valves could be a bit loose in their sockets. The chassis sits on a shelf uncovered, so possible dust or other socket invaders. I'll clean and tighten all valve sockets and pins - it might be a weak contact rather than a short.

Maven

Could also be a microphonic/faulty valve.
Have you tried gently taping them with the back of a screwdriver while the set is on.
JJ

Hi well after all that it looks like the set in intermittent UNSTABLE.
Great!

The instability will most likely be in the front end of the set around V1 and V2.
Looking at some Philips chassis I see they are very technical in construction relying on metal parts like partition shield plates for stability.
It would only need one coil shield can or a partition plate not to make ground for the front end to "take off" and give you exactly what you have.
Some shield plates are only grounded by the hex self tappers not solder wires, tighten all screws and bolts!.
The coil cans may be not bolted down but held by stupid little clips and once more not well grounded, check all clips and bend!.
All it takes is a little corrosion over the years and you have not a shield but an ungrounded lump of metal acting as a transmitting antenna!

Another problem I have seen with Philips sets is the deterioration of the wavechange wafer material buckling and falling apart, where the contacts then do not make good connection. You would only need a bad connection say in the grid lead to V1 from the switch to send the set bonkers. Try wiggeling the switch if the set goes bad.

A good clue to the tehnical bent of Philips design is to look at the circuit and take note of things like "neutralising condenser C35 is is formed by the capacity between the stator lug and the adjacent stator contact" gee thanks fellas how obvious!!

If it goes wonky again quickly try twisting all the cans and metal bits in desperation and tap things using a pencil with a rubber grommet on it as a "hammer" and try to make it go bad and narrow down the area of concern.

All of the valves are internal shielded types so the set probably does not have external shields but if they do CHECK for contact to chassis!


We all love a good mystery!

Cheers, Fred.