Australian Philips 164 Quartet radio low volume.

[Hammer_51]

Hi all. I have a Philips 164 4 valve radio which i have re-capped and changed out of tolerance resistors. Some of the caps are 0.047uF and not the 0.05uF caps required as i have trouble buying them. The filter caps are changes also. All voltages appear to be ok but when tested the volume is low on full volume. I have attached the schematic of someone wants to see it.
can anyone give me any ideas please.
Thanks.
Hammer_51

[Radio Wrangler]

Capacitors of those values are not likely to be in positions important to the alignment of the set, so they are unlikely to cause problems by virtue of the small shift in value.

'Re-capping' is a fashion which seems to have come out of America and is sufficiently prevalent as to get its own new word. It seems to have taken root mostly with less-experienced people. The more experienced folk replace the capacitors in a few positions (where leaky parts could damage far more expensive components) before applying power and only then try the set. If there are components of types known to be risky elsewhere, then these get replaced a few at a time. If an error is made and the set worsens, then the amount of circuitry needing to be double-checked is much smaller.

Usually, the small value capacitors in the RF section are silvered mica types and tend to be very reliable. Replacement of these will also affect alignment and will likely need careful adjustment afterwards. It's usual to leave these alone unless there is a definite problem traced to them.

Sometimes, capacitors and known drifty types of resistors get replaced shotgun style in one go, but to do this, you have to have a lot of confidence in the quality of your soldering etc. It's an awful lot harder to trace a problem than it is to introduce one. Doing the work in small bites and keeping checking levels the playing field somewhat. It isn't cheating

To help you, people are going to need a lot more information. As it sounds like you've already done a lot of work on this set, that means you'll need to be guided through a lot of testing/checking.

People will need to sound you out to assess what level to pitch help at, and also to determine what test equipment you have.

And welcome to the forum.

You started two threads on the same set, and this later one duplicates and extends what was in the earlier one, so I've deleted the earlier one.

David

[marceljack]

Hi Hammer 51
This receiver has no preamplifier between the detection and the power amplifier, so the gain of the audio section is limited.
Did you try replacing the 6M5 (V3) ?

A solution to get more signal at the grid of V3 might be to reduce the value of R6 by putting another resistor in parallel but I see that R6 is included in the pot'meter R7, so maybe it's not possibe...

You should also measure the votage across R13 which produces the negative polarisation of all tubes, maybe it's too negative so you might try to reduce slightly the value of R13.

[PYE 405]

Originally Posted by marceljack

Hi Hammer 51
This receiver has no preamplifier between the detection and the power amplifier, so the gain of the audio section is limited.

So, for a start, the set needs all the RF signal it can get. This means a good outdoor antenna. Try a long wire outside and as high as possible, plus a good ground connection.
This is of course assuming you have not tried this already.

[paulsherwin]

Short superhets seem to have been very popular in Australia, presumably because most people lived in cities and could only receive local stations whatever they used. People out in rural Australia used SW.

Australian designs usually don't have a close European equivalent.

[Gabe001]

It's never going to be a stellar performer, but you could get an idea of the health of the valves by calculating their current draw (voltage drop across anode resistor or OPT using ohm's law). Have you recapped absolutely everything or just the waxies/black tarry ones and electrolytics?

[paulsherwin]

You shouldn't assume that the radio is full of Philips 'black pitch' capacitors as a European radio would be. Aussie manufacturers very much ploughed their own furrow, and foreign owned subsidiaries seem to have had a lot of autonomy.

[joebog1]

WE didnt get the black pitch capacitors here, although I have seen them. We has mostly waxies made in Sydney by UCC ( United Condener Company ) or the worst ever, replace on sight, Ducon capacitors.
As a kid I bought them because they were offered in "grab bags ", and even from brand new they could be leaky which was why they unloaded them. UCC caps should be changed too, but can be checked first as some seem to survive.

Joe

[petervk2mlg]

As has already been said, make sure yuou have a nice long anetnna wire and see if that makes a difference. Have you tried any alignment procedures yet? Better not if you're not sure of how to go about it, but I'd try carefully tweaking C4 the antenna coil trimmer when the set is tuned to a station around 1400 or so. See if that makes an impovement to the gain.

[Edward Huggins]

Originally Posted by paulsherwin

Short superhets seem to have been very popular in Australia, presumably because most people lived in cities and could only receive local stations whatever they used. People out in rural Australia used SW.

Australian designs usually don't have a close European equivalent.

I notice your use of "short superhet". Up to now I had always thought that this meant that the IF valve was reflexed to also act as an AF stage. It might just come from my time with Pye when they made many AM receivers to this type of design.

[paulsherwin]

A short superhet is any superhet design with less than the standard 4+R configuration. Usually the audio preamp is missing, but sometimes there isn't an IF amp. There may or may nor be reflexing present.

Pye made lots of short superhets for the UK market in the 40s and 50s, as you say. They even used them in relatively upmarket sets like radiograms.

[PYE 405]

The 1951 Invicta model 15 "Stationmaster" is a good example of a short superhet. It uses delayed AGC where use of a high value resistor to pull up the AGC towards HT is made, but is held at 0v via conduction of one diode in the EBF80. Only when a signal is strong enough to override this does the AGC come into action.