Gee Robbert if you had come to the HRSA meet last saturday you would have been happier than a pig in shit with all the valves and lots of freebies.

I might have come if I'd known about it.

Revisited the HMV in post 28, paragraph 5. Type C13D/U63A. Valves: the usual 7-pin ones.

It was sitting in the "to-be-scrapped" pile, and its turn for judgement came today.

The schematic shows a 6M5, but this radio uses a 6AQ5.

I decided on a tune-up of the IF, that went ok until I noticed the IF is meant to be 457.5, so did it again with better results. Tuned also the aerial trimmers. The radio has SW which works.

As mentioned in that previous post, turning up the volume produced early distortion, and a hot 6AQ5, due to the use of the Jaycar transformer. The bias is only 5 volts, which is fine for the 6M5, but not for the 6AQ5, so I replaced the 200 ohm cathode resistor with 560 ohm. I began to notice that some distortion was there at any volume setting, and the radio wasn't as sensitive as I'd like. So, first thing was to replace the speaker transformer with a spare. This fixed the hot 6AQ5 and the high-level distortion, but not at the low level. The next thing was to try replacing the 6AV6, which fixed these remaining issues.

I sat back and tuned through the shortwave band without an antenna, and it picked up a number of stations. I was thinking that I should keep the radio when suddenly it went silent. It took far longer than it should have to find that the speaker had blown, the new speaker transformer had a fault, and the tone control (which is used as the 6AQ5 bias resistor) had gone high - all at once apparently.

The tone control problem was supposed to be 500K but now measured 800k, but still worked as a tone control. I put a 1meg resistor in parallel, giving 475K, close enough. I dug through the speakers and found one that fitted. It was the transformer that had me wasting time, but in the end I did decide it had an obscure fault and put the Jaycar one back in. Back to the hot 6AQ5, oh well.

A final test showed it's working well. I just need to clean up the case without putting more cracks in it than it already has.

I need to buy a new soldering iron. I've had this one for a long time and while it still looks perfect, it no longer gets hot enough to make a reliably good joint. This was the fate of all my previous irons too. So, off to Jaycar sometime I guess.

One major problem with greenified solder other than it growing whiskers is that it melts at a higher temp: Horrible stuff.

6AV6 is a cantankerous piece of work at the best of times, the G1 resistor has an attrition rate similar to the G1 resistors on 6V6 & family, plus it has a tendency to go microphonic.

One always burn tests a set especially if its a commercial fix. A failure, stastistically, will occur within three hours.

The Video Output tube 6CK6 will sub for 6M5 (likely same) the suppressor is IC in 6M5, But is Pin6 on 6CK6 & must be tied to the cathode.

Next radio, sitting in the junk pile, is a refugee from some long-gone console. It's a St James Deluxe, which I presume to be a house brand of David Jones. There's no power cord, no knobs, no speaker transformer and no speaker. Valves: 6AN7, 6N8, 6BD7, 6M5, 6V4. The 6N8 had been replaced by a 6EH7 with the required rewiring of the base. All the caps had been replaced about 20 years ago, except the electros which are original.

So I found a speaker transformer, one of those combo European ones that has the choke and transformer on one former. The pins are separate though, and it caters for 3 different impedances. I simply used the one for maximum turns. The test speaker was joined onto the other side. The power cord isn't entirely missing, it just goes to one of those black double joiner things, where you insert the wires and tighten them with screws. So I found a powercord with bare wires at the end and inserted this into the other side of the joiner.

Powered on and off a few times to initialise the electros. Then turned on, it seemed to work ok on MW but dead on SW. Turning up the volume caused loud squealing. The IF was out by about 10kHz, but without instructions I had to assume the usual of 455kHz. Adjusted the IF to this frequency, and it did seem to be louder. After flicking the bandswitch a few times SW came good. Had a listen around, lots of SW stations out there - it even picked up a few without the external antenna. The SW antenna trimmer didn't make much difference. The MW trimmer did though. Only one thing left to fix - the squealing.

The centre wire from the tone control goes to the speaker plug at the rear, where there's a capacitor to ground. One side of the control goes directly to the 6M5 G1. Obviously radiation from the speaker plug was making its way back. Therefore I moved the cap to the tone control, and the wire (now an earth wire), was routed well away from the output stage. Problem solved.

So, in the end the radio works as well as can be expected with 5 valves. But without a case or anything to put the speaker into, it isn't much use. It's now on the garage floor, but still with the valves in. The speaker and transformer have been removed again.

David Jones' flagship store on Elizabeth Street is across the road from St James Railway Station and around the corner from St James Church, most likely where the brand originated from.

Hi Robbbert,

Re purchasing a soldering iron ...
Second best purchase .... a new Hakko soldering iron ... temp controlled, cleaning 'mesh' with a few extra tips ... so simple now.
Best purchase .... a Hakko desoldering iron ... outrageously expensive, but quite a revelation. I can now desolder 16+ pin IC's and they literally fall out of the PCB ... no more destroying PCB's and components ... I still occasionally have a trace lifted after multiple 'desolders', but rare. In comparison, desolder wick is a nightmare.

Obviously, there are other brands just as good ... but the lesson to me was clear ... good tools.

Looked at 2 radios today.

1. Philips mantel radio with 5 valves and a clock. Knobs melted, cover missing from the clock, clock knobs missing, dial missing. Model number not known, but the valves are the usual 9-pin ones: 6AN7, 6BH5, 6BD7, 6M5, 6V4. The electronics needed nothing done, as the radio works fine. The clock works too, except for the alarm. The on/off to the radio had been jumpered over, so the radio is on all the time. So the only work done was for hardware - new knobs for the clock, and moved around the ones on the radio to get it looking somewhat better. Gave it a clean and polish.

2. The Radiola 528MA from post 24, radio 4. Swapped out the remaining wax caps, replaced the 6A8 50k grid resistor. Forgot to put back a cap leading to SW not working until I eventually remembered about it. The main problem was after it was turned on, the local osc wouldn't oscillate until sometime later. Or, sometimes while listening on SW, it would just fade away. Flicking back to MW might fix it. I couldn't really see anything else wrong, so swapped out the 6A8 for another one. It started up straight away. Found some knobs, and gave the case a clean and polish (Jif then Mr Sheen). I used to use car polish but when I tried this time, I found that the contents had dried up -> to the bin. Hopefully the valve was the problem and that the radio keeps working.

Revisited the Radiola B17 mentioned in Post #31. I don't know if it really is a B17 - that's what it says on the back, but searching only returned a transistor model. So, no schematic.

Valves: The usual 5-valve 7-pin lineup. Inbuilt ferrite antenna. Volume, tone, tuning. One knob missing - I found something that fitted, although it looks totally different.

A terrible bit of design work - the incoming power cord lies right on top of the 2 hot resistors in the power supply. I wonder how many of them went up in flames.

The bias on the 6AQ5 was quite low, the backbias resistor being marked 150 ohms. Measuring it produced random values, so I replaced it with a 470 ohm - this produced a bias of about 12 volts, and gave an extra 22 volts of HT. This bias is exclusively for the 6AQ5 - the AGC has its own arrangements. Did a IFT alignment, which produced a worthwhile increase in sensitivity and volume. The shaft for the tuning knob was at an angle, so I carefully adjusted the screws that hold it in until it was straight.

Last thing to do was to replace the wax caps. The 2 high voltage ones were done, but I'm out of low-voltage caps, so the 5 of them will have to wait until I can visit Jaycar. The radio is residing on the bench in the meantime.

As mentioned in the original post, the homemade wooden cabinet is terrible, and had gone mouldy. I gave it a cleanup, although it's still pretty awful.

Mould often has to be bleached out.

The back bias resistor is based on the total loading (in most cases) of the tubes, all of which ground back to the CT via it. When things are as they should be, the voltage across it CT to chassis (Chassis positive) is normally the grid bias of the output tube.

Quite often the first filter cap is not floated & it ends up being shorted out.

Didn't I see a photo of you in the ABC news the other day? Something to do with mobile phone reception.

Highly probable they did ask for photos that was via ABC Gippsland.

Never saw the article. What's Mobile reception? Have not had much of that since day one of it.

I decided to have another look at the PYE PE-34, because I managed to locate a spare EF22 to replace the one that broke. Also, the valve socket is held in by screws, so if the EF22 doesn't work I can replace the socket and use a EF39 or 6U7G.

So, first problem is there's no info on the net about this radio, even radiomuseum has nothing. The thought is that it's similar to some other PYE model, but I'm not going to depend on that.

So, does anyone have a schematic and maybe other info on this model?

In the meantime I'll get it out of the case and see if I can figure out what's causing the motorboating - the thing was working 10-15 years ago so it shouldn't be too much, I'd imagine.

After that I'll see if I have a working EM34 and install it.

I figured out that the noise could be stopped by disconnecting the little cap that feeds the AGC diode. After that we now had a rather loud hum. This was more mundane - a UCC filter electro was open circuit. I tried a few used ones I had on the bench, the first caused clouds of smoke, because it was totally short circuit, even though it looked almost brand new. The next one worked, getting rid of all the hum, so in it went.

Now we had silence. I turned the bandswitch and found out which of the 8 bands was for MW. Twiddling the tuning dial produced stations, so now it's working. But, the AGC cap is still disconnected, although the radio seems ok without it. Need to investigate more.

This radio has been attacked sometime in the past - the tone control (a convoluted switched arrangement) is entirely missing. The volume control had been replaced with a metric one, and the volume can't be turned right down - at minimum there's still plenty of sound. The control also has a power switch but it does nothing - the power is always on.

And lastly the wrong size speaker is in the radio - the correct speaker went into another radio years ago. I need to see if there's a proper-size spare.

Lessons hopefully learnt. Electrolytic caps abandoned and NOS will loose polarity (form).

It has gotten to the point here that I will not use one unless its been put on one of the the reformers to assess its condition & re-polarise it. Its not only power ones, all of them in tube radios that will loose form, it's all of them; albeit newer are better for leakage & not loosing form.

It is important to check leakage on Non Polarised caps : Electrolyitics are meant to leak but there is a limit.

Marc