Dynatron Henley RG33W radiogram

[julie_m]

Picture 5 is the power transformer; the two smaller ones are for matching the speakers (which need a high current at a low voltage) to the output valves (which are supplying a low current at a high voltage). We don't need to worry about these for now.

It looks as though the thin red, orange and yellow wires disappear right into the innards of the transformer. They probably are the primary connections; I can see what might be a voltage selector panel. Any chance of some more angles?

If we number the tags 1---2---3 from left to right across the top row and 4-5-6-7-8 from left to right across the bottom row, then to me, it looks as if the thin red wires on 6 and 8 are the two ends of the HT winding, with 7 (which is joined to 1 and 4) being the centre tap; and the thick black and brown wires on 1 and 5 are the heater winding. That being so, I would expect 6 and 8 to go to the EZ81 valve (if the print has worn off, you can identify it by its distinctive internal structure -- see here for pictures); and 1 and 5 to go to pins 4 and 5 of all the valves.

If there was a short-circuit in the heater wiring, I would expect the transformer to buzz angrily and get very hot when power was applied. I'm more inclined to suspect something amiss with the primary side of things.

Anyway. For now, check my educated guesswork above against how the set is really wired (set unpowered) and if I was right about the heater wiring, try the following test:

1. Remove all the valves, labelling them so you will know later which one came from where, and any indicator or scale lamps that may be connected to the same wires.
2. Meter on ohms, to pins 4 and 5 of any valveholder. Note reading.
3. Disconnect one probe of meter, change to AC volts, reconnect probe to same place. Note whether meter reading is a steady zero, or randomly-changing small values.
4. Apply power and note meter reading.

If I was wrong about the wiring, please put me straight and I will revise my instructions accordingly.

You can leave the valves out for the next round of tests.

[Michael Maurice]

What seems odd to me is that the O/P stated he sprayed switch cleaner on the switches after which the set did not work.

So to go from that to a faulty transformer seems to me to be unlikely.

If the transformer has failed, I would expect it to have smoke and give off a burning smell before its demise but according to the O/P that didn't happen.

Please also note that if indeed the set is fitted with an EZ81, then the circuit published in post #50 is incorrect.

I dont know which part of London you are in but if you need help then please contact me.

[peter_sol]

I don't think we can source the correct circuit so that one is the nearest we have.

[Station X]

Originally Posted by julie_m

If we number the tags 1---2---3 from left to right across the top row and 4-5-6-7-8 from left to right across the bottom row...

Is it my imagination, or is there a spurious piece of wire between tags 7 and 8 in the fifth picture in post #53?

[julie_m]

If you look at the third photo in post 23, there is an EZ81 standing to the right of what looks like the smoothing can.

I'm still inclined to suspect something amiss on the primary side of the transformer, but we'll need some more photos of the wiring around it to be certain. It does look as though it's been hot sometime in the past, but the OP never mentioned any rattling or smells like you would expect from a transformer running into a short-circuit. There seems to be a voltage selector and a fuse; so it ought to be possible to isolate the primary winding and meter it directly, without the reading being spoiled by anything else in parallel with it.

EDIT: I noticed that too, but I don't think it reaches all the way to tag 7. Something else for the OP to check, though .....

[Station X]

Originally Posted by julie_m

If you look at the third photo in post 23, there is an EZ81 standing to the right of what looks like the smoothing can.

That would fit in with tags 1 and 2 feeding the EZ81's heater winding and tags 4 and 5 feeding the heaters of the other valves.

[Station X]

The internal fuse would appear to be in the primary circuit.

Removing it, along with the lamp and turntable plug should result in an open circuit between the L and N pins of the mains plug. On replacing the fuse the resistance of the primary winding should be measured across the mains plug pins. Should it still measure open circuit, then try the mains voltage selector in a different position. Under no circumstances plug in the player with the voltage slector set incorrectly though.

[Vintage84]

Good morning all.
Julie's post seems to have the wiring spot on. There is an EZ81 valve, which is connected to tags 6 and 8.
There is only one valve where the label has rubbed off (photo attached). I believe its an EC something and is the same size as the EBF89.
Do I need to remove the EM84 magic eye valve for the tests?
That spurious piece of wire doesn't quite connect tags 7 and 8.
Thanks again for all your help and suggestions!

[Vintage84]

Originally Posted by julie_m

[*]Meter on ohms, to pins 4 and 5 of any valveholder. Note reading.[*]Disconnect one probe of meter, change to AC volts, reconnect probe to same place. Note whether meter reading is a steady zero, or randomly-changing small values.[*]Apply power and note meter reading.[/list]If I was wrong about the wiring, please put me straight and I will revise my instructions accordingly.

You can leave the valves out for the next round of tests.

Results with 9 valves out (but magic eye still in)
1) 5.3ohms
2) .001V
3) .001V

[Station X]

You will need to repeat the tests with the magic eye removed, as its heater will be connected across the heater secondary winding of the mains transformer.

[julie_m]

O.K. The unidentified valve could be an ECH81. That would be connected to the tuning capacitor, the wavechange switch and the coils. If it's faulty, the record player will work but you will not be able to receive any radio stations. Those valves are usually fairly reliable, though, so don't worry about it for now; just remember where it came from.

Yes, the magic eye will need to be removed for the transformer test as described in post 61.

The errant piece of wire on tag 8 should be either cut off short, or bent away from pin 7.

As a next test, you could try:

1. Disconnect power
2. Meter on AC volts range to tags 6 and 7, preferrably using crocodile clip adaptors
3. Make sure your fingers are well clear of the transformer and apply power
4. Take voltage reading
5. Power off and move probe from tag 6 to tag 8
6. Fingers clear and power on
7. Take voltage reading
8. Power off.

[Vintage84]

Originally Posted by Station X

You will need to repeat the tests with the magic eye removed, as its heater will be connected across the heater secondary winding of the mains transformer.

The magic eye was easier to remove than expected!

Results with 9 valves and magic eye removed:
1) 1400 k ohms
2) .001V
3) .54V

[Vintage84]

Originally Posted by julie_m

As a next test, you could try:

1. Disconnect power
2. Meter on AC volts range to tags 6 and 7, preferrably using crocodile clip adaptors
3. Make sure your fingers are well clear of the transformer and apply power
4. Take voltage reading
5. Power off and move probe from tag 6 to tag 8
6. Fingers clear and power on
7. Take voltage reading
8. Power off.

Tags 6 & 7 and 7 & 8 both give readings of 280v

[Station X]

The mains transformer primary is OK then as are the HT (High Tension) secondary windings. Possible fault with heater winding.

With power applied check the AC Voltage from tag 7 to tag 2 and tag 7 to tag 5.

[Vintage84]

7 to 2 = 240v
7 to 5 = 0.56v

[Station X]

Tag 5 is obviously one end of the heater winding then, as the reading on it ie approx 0.54V is the same as that on pins 4 and 5 of the valveholders.

I'm not so sure about the 240V on tag 2. Where does the wire on it go to?

[Vintage84]

Tag 2 is the mains power N. It comes into the chassis up to the piano keys and then down to Tag 2 in the transformer. The brown cable then disappears into the transformer.
The mains power L goes from the piano keys through the fuse and voltage selector and then onto Tag 1.

[Station X]

I'm comfortable with tag 2 going to mains neutral.

However it looks like tag 1 is wired to tags 4 and 7. Tag 7 should connect to chassis at some point, so with mains on tag 1 there'll be a big bang when power is applied.

[Vintage84]

Sorry - I think I made a mistake there... The mains L goes through the fuse/voltage selector and then down inside the transformer just behind tag 1. Tag 1 is connected to a different cable coming out of the transformer.

Tag 7 is connected to tag 1 and a cable from inside the transformer.

The wire between tag 4 and 1 might be broken.

[ms660]

In one of the pictures it could be interpreted that the voltage selector wires go to tag 1, the plan view of the transformer shows that they don't, maybe that's caused confusion with the OP.

That 240 volt reading might be a ghost reading if using a high impedance meter?

If the above is nowt to worry about I would disconnect the brown wire from tag 5 and measure the AC voltage between tags 4 & 5.

EDIT: Whoops...my post crossed with the OP's.

Lawrence.