Pye black box no sound

[ms660]

If in doubt, pin 1 for the EL42 is the one that's connected to the chassis, pins 3 and 7 are the cathode.

Lawrence.

[Station X]

Originally Posted by Minster97

Readings for the two capacitors are 275V and 236V
Output transformer all three readings are 275V
I am fairly sure that the valve holder for ECC83 is ruined.
The readings for Ecc83 are pin 1 zero,pin 3 69V,pin 6 zero or very slightly minus,pin 8 zero
I could see the wider gap between the pins so think I got the numbering right.
Now the EL42’s,There was a wire going across the opening to a pin at about the four or five o’clock position,I have assumed this is pin 8
Readings for both valves are the same.pin 2 16V,pin 3 0.2 V , pin 5 zero pin 6 15.7V
I am very lost now.I suppose I have got to start by replacing the valve holder?? but not sure what is the correct one.Thank you

There's something very wrong there.

The outer tags of the output transformer's secondary winding are wired directly to pins 2 (anodes) and 5 (screen grids) of the EL42's. You should be measuring around 275VDC on these sockets of the EL42 valve holders even if the valve holders are dodgy.

You need to check your pin numbering and measurements. The "pip" on the EL42 valve and valve holder is between pins 1 and 8. Pins number clockwise when viewed from below the chassis.

[snowman_al]

A picture might help?
As stated count 'clockwise' from pin 1.
Alan

[Minster97]

It looks like what I thought was pin 8 is pin one.Thanks for the help.will check readings again

[Minster97]

Both EL42’s valves the same.
Pin 2. 277V. Anode
Pin 3 15V. Cathode
Pin 5. 278V. Screen Grid.
Pin 6 .01V Control Grid.

ECC83.
Pin 1. 196V. Anode (2)
Pin 2 Cathode (2)
Pin 3 zero V. Grid (2)
Pin 6. 67V. Anode (1)
Pin 7
Pin 8. zero V Cathode (1)

On ECC83 could only count 8 pins!

[Station X]

EL42's looking good.

ECC83 has 9 pins. Check again and redo your measurements on it after making sure it's lit up.

[snowman_al]

My error on the ECC83 pin 1. (The others are correct) It is actually pin 6. I was doing it from photos, I do not have one to look at...

You might only see 8 pins as 2 heater pins (pins 4 and 5) are soldered together.
Have a careful look again and see if you can find two pins soldered together.

Also make sure the cap lead, in the the centre of your picture, is not touching the nut and bolt.

Alan

Edit, Yes my error. Look someone (Half A Mullard) has been here before... https://www.vintage-radio.net/forum/...1&postcount=56

Apologies, Alan

[Minster97]

I will do ecc 83 again tomorrow. It is NOT lit up anymore now. When I looked at the pins from the top they were a bit mangled. After I tried to repair it’s worse. The light always went out and you had to waggle the valve around. There may be two pins soldered together. If I can’t get it to light up shall I just try and get a new holder from somewhere? I did try another valve and no joy so I assume it must be the contacts. I have cleaned very well.

[Station X]

Check valve holder sockets 4, 5 and 9 (which serve the heaters) carefully, preferably with a magnifier. If they're not damaged try nipping them up so they make better contact with the valve pins.

[barretter]

Originally Posted by Minster97

I will do ecc 83 again tomorrow. It is NOT lit up anymore now. When I looked at the pins from the top they were a bit mangled. After I tried to repair it’s worse. The light always went out and you had to waggle the valve around. There may be two pins soldered together. If I can’t get it to light up shall I just try and get a new holder from somewhere? I did try another valve and no joy so I assume it must be the contacts. I have cleaned very well.

Just to be absolutely clear about the pins of the ECC83 : looking from below and counting clockwise from the gap, pin 1 is anode, pin 2 is grid, pin 3 is cathode, pin 4 is heater, pin 5 is heater, pin 6 is anode, pin 7 is grid, pin 8 is cathode and pin 9 is heater centre-tap. Usually in power amplifiers the valves are all run from 6.3V and in the the ECC83 this means connecting pins 4 & 5 together and connecting the 6.3v between that junction and pin 9. According to the printed instructions for the ECC83, EL42 version of the Black Box one of the cathodes of the ECC83 should be at about 25V.
When you say the ECC83 is not lit what do you mean? Quite a lot of the small 9-pin valves flash when the power is first switched on because the cathode sleeve doesn't quite cover the heater wires and the sudden inrush of current makes the wires white hot for a moment but they soon settle down to a dull red.

[Minster97]

Thank you all.Ecc 83 remained cold and no sign of any glow.The valve seems loose in the socket and if you moved it you could get it to light with a lot of crackliing noises.One of the pins in one of the sockets was very loose possibly broken.
Before I tried to improve the pin contacts you could just about get the valve to stay on ie warm and a definite constant glow

[Edward Huggins]

This will just not do. It will never settle in a fractured state like this. Suggest you buy a B9A (ceramic) valveholder and carefully re-wire. This one valve provides 2 key functions as AF amplifier and Phase Splitter and you can't afford any kind of poor contacts in these stages. I would recommend a B9A ceramic valveholder with skirt and screening can for optimum performance.

[Minster97]

I certainly will try to salvage the holder and tryi nipping.I do have very fine instruments to try this.replacing the holder I dare say will be challenging for the likes of me!

[Sideband]

You will have to replace the valveholder. You can't repair the pins once they are broken. Don't leave the amp on whilst in this state. B9A valveholders are readily available from a number of sources. You need a good one, either nylon or ceramic type and as suggested with a skirt and screening can. I had to do this a few years ago (plus the B8A ones as well)! It's an hour or so work for one valveholder but well worth the effort. Plenty of good clear photos or a clear hand drawing of the connections and you'll find it's easier than it looks.

[Minster97]

Edward just seen your post and will buy one anyway

[Sideband]

The forks on the valveholder pins break. No amount of twisting, bending, nipping or any other 'wangle' will do and if by some remote chance you do have some success, it won't last and will just emphasise the need to replace the holder.

You'll probably need to drill the old holder out (if it's riveted). Just replace the new one with suitable sized nuts and bolts. I would suggest you unsolder all the connections first taking lots of photos beforehand so you can see where everything goes. It really isn't as bad as it seems but it can be fiddly at times. At least you don't have a customer breathing down your neck wondering when his amplifier is going to be fixed....! Take your time and make sure you get everything right referring to your photos.

[Minster97]

Ordered a good one from langrex.just taken out screws and nuts( not riveted��) and making detailed drawings of where everything goes.Thank you again

[Minster97]

Fittted the new holder,valve lights up and no crackling noises.problem is no sound other than hum from pick up or buzz testing anywhere.
ECC83 readings are:-

1) 135V Anode 2
2) 16V Grid 2
3) 63V Cathode 2

4 and 5 both zero

6) 52V Anode 1
7) 1V Grid 1
8) 1 or 2V Cathode 1

9) zero
I was very confused that there is pin 10 the tag of which is at right angles to the others.I have not connected this to anything.Could this be the cause? Thank you

[Minster97]

Should have said no sound other than hum.Nothing from pick up at all

[Station X]

Anode voltages are low. Check R5 and R9 the anode resistors along with R13.