Last night's attempted repair did not go well. It's a PYE 19D, made in Europe. European radios generally are quite reliable, but they are a royal pain to work on. If anything breaks it's quite a job to fix it. The schematic exists, but it has no voltages or component values.

Valves: ECH35, EF39, EBC33, EL33, AZ31.

Equivalences:
AZ31 is a 5Y3G with a 4 volt filament.
EL33 common giant-sized output valve
EBC33 is a short 6B6G. It has a red sprayed-on shield.
EF39 is a short 6U7G, also with a red sprayed-on shield.
ECH35 common frequency changer.

The AZ31 had been replaced by a 5Y3GT, which would seem to be a bad idea, however there's 302 volts after warm-up, so the substitution would seem to be ok. The radio has 6 shortwave bands, medium wave and long wave. There's an indicator as to which band is selected.

The problem was low, muffled sound which I never found the cause of. Voltages all ok, all valves replaced, no improvement. Most of the resistors and capacitors need replacement, but with the accessibility problem it isn't going to happen. Other problems were a blown dial light (fixed that), the band indicator was 2 bands out (fixed that), the dial cord slips (it's original, not fixed), and someone had screwed in the only accessible padder all the way in (fixed that). There seems to be multiple dry joints around the IF valve socket, so the sound cuts out, or the heater goes off. It was so difficult to even keep the EF39 working that I substituted a 6U7G (I don't have any spare EF39's, and the EF36 has much less gain). Half of the veneer on the cabinet top fell off, so it doesn't look great either.

At least the dial glass is good, and the power switch works (a common failing on these sets, and it's unobtainium). The speaker transformer is a combo choke as well, on the one former. If it blows, unobtainable as well.

The IF transformers are sealed, so although there's a tiny metal spike, they can't really be adjusted. The ECH35 gets hotter than the output valve.

At this stage I'm undecided as to whether I should persevere, or just scrap it. I'll think about it over the next week.

European radios generally are quite reliable, but they are a royal pain to work on.

I have an aversion to Philips/Mullard radios. Some of the bizarre things that Philips did makes me think that they were trying to make repairs a PITA.

Yeah I hate the ones where the dial assembly was screwed to the wooden case with rusty wood screws but it's not part of the chassis. The dial cord is the only thing that joins them together. Sometimes the cabinet-mounted speaker gets mixed up with them too. Idiotic.

Since there's not many of us left...

How big is the vintage radio/television community these days?
I know there isn't many younger people.
But dabbling in valve and transistor gear is understandably uncommon for my generation as there isn't many people out and about getting people interested.

In this day & age a prophesy of Einstein is becoming more self evident, this being exacerbated by the schools teaching any stupid subject other than the ones we would have called life skills.

Time and again I would get school leavers that were illiterate and therefore had no basic useable skills I could use without giving them the education they should have got. In Victoria we had Technical Schools and High Schools and these trained different career paths. Of course this was highly successful and flew in the face of modern bureaucracy and along with anything else found to work: Has to be destroyed.

Being rural we face the true picture of the oxymoron "Australian Worker". I have said it before; I worked with a labour hire group. It was a bloody nightmare. You would requisition a group of Aussies & then waited to see how many actually fronted & how many you had left at lunch time. You do not have that issue with Asian immigrants and those from the Sub-continent, they have a work ethic.

This is why we are now are net importers of technical people & farm labour.

When it gets to repairs, we have only just got to "right to repair" and that has been a thorn in the side in USA with farm Machinery & its happening here and with automotive. One Farmer pointed out that it was over $1000 USD (one way) to get the tractor back to the dealership, to get it fixed. Parts were not supplied to be fitted by the Farmers.

Here if the plastic car has issues, there are no chips available to fix the problem & they try & hide the fact that they can't fix it.

A lot of modern electronics fall into the same category and too much of it is used to do jobs that could be done mechanically more reliably.

When Einstein said we would create a generation of morons I believe he was right & we now have it. I go to weddings I go eat out , what do I see? A full table of people, benches of people, people driving vehicles, texting invisible friends.

Went to post this earlier, but the site was down.

Spotted another PYE on the floor, this one a model PE-34. The chassis is identical, so I hoped I could borrow the AZ31 from it.

Valve line-up: ECH35, EF22, EBC33, EL33, AZ31, EM34

However... the EL33 had been replaced by a EL3NG, the AZ31 by a 5Y3GT, and the death blow is because I found the EF22 has a crack in the glass. You can guess how many spares I have of such a rare valve. Also, the EM34 was missing. The cabinet is nice though. When powered on, it motorboats. The original speaker has been replaced by a smaller one.

No success with the previous PYE, so I guess both will be scrapped.

To my complete surprise, the PYE 19D is now working. I had given up on it, and put the chassis back in the case, and was attaching the speaker leads (they plug into the back), when I spotted a screw next to the name plate (the label which shows the model number and valve placement). On an impulse I tried tightening this screw, and found it was just a bit loose. After putting the knobs back on I turned the radio on, and - it worked !!

The case is horrible though, I will probably put the chassis into the case for the above-mentioned PE-34.

Next radio is a wooden Radiola with some shortwave bands. The model number is unknown. There was a note spelling out all the problems with it. One end of the cabinet is covered with this sticky gooey substance, something akin to honey or amber, which has destroyed the veneer. The power cord is also affected. Given the multitude of issues, it went straight to the scrap pile.

After that, there's a HMV which might have once lived in a console, but someone constructed a small wooden case for it. No idea of the model number, but it has 3 SW bands, MW and Gram. Valves are 6AN7, 6N8, 6N8, 6M5, 6V4. The speaker is mounted on a single nail at the back without the benefit of a baffle. The homebrew case is a real shocker, eww. When originally received, the short wave barely worked, and I found a manufacturing error - the shortwave aerial coil had been wired backwards. After this was fixed it worked really well. It's undergoing burn-in now, and it is working perfectly. A pity about the case though. If anyone knows the model number, please let me know.

Now I'm looking at yet another PYE, model 9-MSW, this one is made here, and has the usual valves: 6AN7, 6BH5, 6BD7, 6M5, 6V4. The problem is the valves light up but otherwise completely dead. Unfortunately I couldn't find a schematic online where I don't have to sign up, so I'll have to do without.

The PYE 9-MSW didn't take long to condemn. I first established that the audio was working, then I found the plate voltage on the 6BH5 was zero. It turned out that the Philips-style tiny 2nd IF transformer was completely open circuit on both sides. I had to cut it out of the set, then removed the can to find a single block of resin encasing all the internals. There was no way to look for a broken wire. Only thing to do was throw it in the bin. Radio went to the scrap pile. The cabinet was good, and the the back cardboard was intact too. Oh well.

Last radio for the night, a cheap plastic Radiola (I think it said 566MA, rather hard to read). Valves: 6X4, 6AQ5, 6AV6, 6BA6, 6BE6. It worked, but if you turned the volume up full the sound would choke up and almost disappear. It has a volume knob on one side, and a combined power/tone on the other side. The dial is like a 11-99 dial. As you know the knobs on those plastic sets break very easily, and this was no exception. The volume knob came off ok, but the tone knob snapped off. The remains wouldn't let me get the case off, so I had to use a screwdriver to lever out the bits. The components were all originals, so it seems I never opened it before. The voltages in the audio section seemed ok, but I decided to replace all the components around the 6AV6 triode anyway. After that the problem was gone. Success at last.

Today's work was on 4 almost identical radios. Valve lineup: 5Y3, 6V6GT, 6AU6, 6AR7GT, 6A8G.

1. Radiola 527MA, brown case with a small hole in the top, 2 knobs missing. The yellow grill was melted. No sound, just faint crackles. Found that the 500k resistor to 6AU6 G2 measured 900k, and the bypass cap at that point was cracked in half. Replaced, radio works

2. Hotpoint V55ME, brown case, 2 knobs missing, melted grill same as the previous radio. Bad sound. Same capacitor was shorted, Replaced it, another working radio.

3. Hotpoint V55ME, brown case, all knobs missing, no back. Smelled bad after a while. When opened, found a wire sitting on a hot resistor. As it heated up, the insulation on the wire started to smoulder. Moved wire. Then after a while I noticed the 6V6 grid was red hot, but the sound was working. What could it be? There was a kind of faint rushing noise, and I noticed that moving my hand around would alter this noise, or even get rid of it. The audio stage was clearly oscillating. On this radio the line from the volume control passes close to the capacitor that joins the output stage to the tone control, and there was leakage through the air. Moving the components further away from each other solved the issue. So far 3 out of 3 successes.

4. Radiola 528MA, white case, all knobs missing. Kept cutting out. Once I downloaded the schematic (which has both the 527MA and 528MA), I realised this is a MW/SW radio, which meant the bandswitch was probably faulty, which proved to be so. The bad part is hidden under components and wires, so I couldn't do anything. This model has a X61M instead of the 6A8G, this is because the 6A8G is a poor performer on SW. I got the SW to work for a little while, and proved that the 6A8G works on SW but is much less sensitive than the X61. In fact this radio already had a 6A8G in it. The X61 is not very common, but it can be replaced by a ECH35, which works even better. Once I got the radio back in its case, the bandswitch cut out almost completely, making the radio useless.

So, 3 successes, 1 failure.

By the way, the schematic has the top view of the 527MA and 528MA swapped around, so don't get caught out. Another strange thing is they say the 6AU6 anode should have 20 volts while G2 has 70 volts. None of my radios has anything like that, but the stage works anyway.

One bad design mistake, is that the high voltage capacitors were rated at 400 volts, but the rectifier can actually exceed this before the valves warm up. Replace them with 630 volt caps.

I think it was in Silicon Chip where the VR column once had some comparisons on radios which had a common cabinet across the Australian and European markets but different chassis for each market. This ran over several months and the consensus was that the EU sets were probably technically superior but a serviceman's nightmare whilst the AU versions were a typical Australian five-valve design which simply worked well, brought in distant stations and stayed working for longer because there were fewer parts to break down. Philips and Mullard models featured heavily in these articles.

The old Ducon's had a working voltage & a surge voltage on them. Modern caps rarely do. I think Mouser does.

However, with a #80 / 5Y3 and any filament rectifier similar & Silicon diodes feeding heater tubes; You start with B+ virtually open circuit and the surge resulting from virtually no current draw is virtually EMF and can get to close to twice EMF. Therefore every thing exposed to B+ must be able to withstand that voltage.

Be careful as to what you throw out.

You may be able to find the HMV on Kevin Chants site & Arthur Courtney made a list of every thing he could find and its valve line up.

6AN7 & 6M5 were common in HMV That will not be R53A as it went 6AN7 6N8 6N8 6N8 #807 but a line of 6N8's was common.

The most common short in 6GW8 & 6X5 and others is heater to cathode. And on overload or open circuit grid, its the plate that starts to show embarrassment & go red or blue.

#24 was often used as the rectifier for #50's grid for "C" bias: Grid tied to plate. Heater on its own winding.

Marc

Another strange thing is they say the 6AU6 anode should have 20 volts while G2 has 70 volts. None of my radios has anything like that, but the stage works anyway

I suspect it is a result of the meter you are using and this is a subject close to my heart.

The voltage table given with the circuit specified a 1000 ohm per volt meter and if you use a VTVM or a high input resistance digital meter, it will read much higher, as the meter loading is much less. The designer used a 1000 OPV meter when compiling the table, so this must be accounted for if using anything else.

Harold

Today's installment of this thrilling series...

1. Radiola 467MA - yet another of the 6BV7 clones (6BE6, 6AU6, 6BV7, 6X4), very insensitive. Fortunately the reason was obvious as soon as I opened it. What I had thought was the antenna wire was the earth wire, and the antenna wire was missing. So I ran a yellow wire from the little clip on the ferrite rod, through the hole in the back. Didn't even need the soldering iron. Once that was done it roared into life. The case is perfect, all original knobs present, a lovely radio.

2. Hotpoint P55ME. Case has holes in it at the top, and the hot output valve had melted another hole at the rear. The power plug had to be replaced as the rubber shroud had gone rotten. I couldn't remember what else was supposed to be wrong with it, but looking underneath showed 2 black caps that had cracked up, one was leaking fluid. Replaced both, radio working fine. Pity about the case.

3. STC A5150, the usual STC lineup (12AH8, 6BA6, 6AV6, 6CH6, 6X4). Case is the usual cheap crappy plastic one that breaks up after a while. It's a clock radio, the clock had broken and burnt out, had been disconnected. There's not much left of the case. Although the radio works, decided not to do anything with it. Had to replace the power plug on this one, again the rubber shroud had rotted.

4. HMV 65-54, it's a common radio, like a brick with "Super 5" on the front (6AN7, 6BA6, 6AV6, 6M5, 6X4). Distorted output when the antenna is connected up. The AGC caps had turned into resistors, replacing them restored the voltages, but still somewhat distorted. Not really sure what to look at next. The 6M5 bias is about 5.5 volts, which seems ok according to the datasheet. One thing I did notice is the external antenna wire doesn't do much, putting the hand on the ferrite gives much more volume. Found that the external wire goes through a filter. Bypassing this gives a massive jump in sensitivity.

5. HMV, not marked on chassis, but the paper insert applies to C13D and U63A. Presume one has SW and one doesn't. This one does, so I gave the bandswitch a spray and it seemed to be ok after that. The bias on the 6AQ5 was only 5v instead of 12.5v but decided not to change anything. The speaker transformer had been replaced by a Jaycar hack, which probably explains the bad distortion when the volume is turned up. The case was literally held together with duct tape, and is pretty scratched up. Anyway, not going to do anything more with it. It's working to its capabilities.

Hi Robbbert,

I'm intrigued ... lost count of how many 'Misc Repairs" this Thread includes ...
Are all these radios part of your Collection??
What are you going to do when you get to the end??

Are all these radios part of your Collection??

Yes. There's many more radios which are working and didn't need a repair.
Unfortunately, valve radios which sit unused on a shelf tend to break down spontaneously. They need to be tested every few years.


What are you going to do when you get to the end??

I'll cross that bridge when I get to it.