Hartung amplifier project

[Ian Mason]

Dear all, I wonder if anyone could help me please as I am somewhat of a novice when it comes to electronics but I am also a very keen and quick learner, I am just starting to build a Hartung headphone amp which came in kit form, this is p2p with no step by step guide and I am having to construct it from the schematic and my question is that there are two things on the schematic(picture provided) that I don't understand, number 1 is to the very left which has a black dot with a 47 Kohm resistor, I can see that one side is ground but what does the back dot indicate ie what is the resistor attached to (incidentally the resistor was not in the kit) and the 2nd problem is at the very bottom right, the 6.3v cables have no indication of where they are supposed to go, I would so grateful to anyone that could help me please and I would like to say a massive thank you in advance and merry Christmas and happy new year to everyone.

Thanks and best wishes Ian​

 

[BobK]

The black dot is the input. The unconnected wires from the transformer are The filament winding, and, presumably connects to the filament of the tube, which is not shown.

Bob

 

[Audioguru]

The circuit is probably 100years old. Why make it today?

 

[kellys_eye]

Not quite 100 years but I get your drift!

There is still a very active 'tube' amplifier community - those that like the 'warm' sound that tubes (valves) are purported to deliver...

 

[Audioguru]

Toob amplifiers muffle the highs a little (but this headphones amp does not have an output transformer that cuts the highs) and makes very low frequencies "loose" instead of tight because they produce poor damping. The "warm" sound is the added even harmonics distortion.

 

[Ian Mason]

Thanks to everyone for their input, I have a few more questions regarding the same amp build, would anyone be able to help or do I need to start a new thread.

 

[Audioguru]

This is your thread about the headphones amplifier so put your questions here and they might be answered.

 

[Ian Mason]

Thanks, could anyway please tell me if the wiring for the power is correct for the UK in these photo's, it seems that the red wire is coming from the neutral pin of the plug and going to the fuse and a separate wire from the switch to the fuse, where as the blue wire is being grounded at the rca input and also going to the negative side of the capacitor which means that the live pin on the plug is not being used. Also what happens with the white cables from the transformer as it appears that they are unused in this build.

 

[duke37]

As I read it, the mains input wires are white. No other wires should be connected to the mains plug other than a yellow/green earth wire to chassis.
The pair of red wires should go to a bridge rectifier and nowhere else. (110V)
The pair of blue wires should go to a bridge rectifier and nowhere else.(250V)

 

[Ian Mason]

As I read it, the mains input wires are white. No other wires should be connected to the mains plug other than a yellow/green earth wire to chassis.
The pair of red wires should go to a bridge rectifier and nowhere else. (110V)
The pair of blue wires should go to a bridge rectifier and nowhere else.(250V)

Thank you very much for answering, could you please tell me exactly where the four white wires would go is it live and neutral from the 3 pin plug and live and neutral to the switch and one last thing how is the fuse then wired up, sorry to be complete novice but I really appreciate you help. Thanks Ian

 

[duke37]

You are in the UK so there will be a fuse in the mains plug. Chose a 1A fuse, this may be difficult to find, 3A and 13A are much more common.

The four white wires go to two windings. These must be connected in series with the correct phase. If you are not familiar with what this means, get someone who does. This is critical. The two spare white wires will then go to line and neutral. If you want a mains switch in the amplifier, then it should be in the line connection as should a fuse if you fit one.

I am worried that you are involved with high voltages that you do not understand. Why not start with a low voltage transistor amplifier which is unlikely to kill you.

 

[Ian Mason]

You are in the UK so there will be a fuse in the mains plug. Chose a 1A fuse, this may be difficult to find, 3A and 13A are much more common.

The four white wires go to two windings. These must be connected in series with the correct phase. If you are not familiar with what this means, get someone who does. This is critical. The two spare white wires will then go to line and neutral. If you want a mains switch in the amplifier, then it should be in the line connection as should a fuse if you fit one.

I am worried that you are involved with high voltages that you do not understand. Why not start with a low voltage transistor amplifier which is unlikely to kill you.

Thanks for your concern, it is true to say that I am out of my depth, I understand what in series means but I am unsure of the correct phase, the amp has an off switch and fuse as standard (built in) and I am pretty much aware of where everything else goes except for the primary (white wires) from the transformer, I think you dead right though I do need help, thanks for helping.

 

[duke37]

It is not easy to get the phase of the input windings correct, they may be labelled start and finish and one start should be connected to a end leaving two wires for input. See the circuit diagram.

the best way would be to use a measure of the inductance with no secondary connected. With the phase connected the right way round, the inductance will be much more than the wrong way round.

A bulb could be placed in series, known as a lamp limiter. The lamp will only just light if the phase is correct but if the phase is wrong, the transformer will be close to a short circuit and the light will be at full brilliance. A lamp limiter is of value when diagnosing faults in equipment, particularly if using valves. It enables voltage to be applied with little risk of damage.

 

[Ian Mason]

It is not easy to get the phase of the input windings correct, they may be labelled start and finish and one start should be connected to a end leaving two wires for input. See the circuit diagram.

the best way would be to use a measure of the inductance with no secondary connected. With the phase connected the right way round, the inductance will be much more than the wrong way round.

A bulb could be placed in series, known as a lamp limiter. The lamp will only just light if the phase is correct but if the phase is wrong, the transformer will be close to a short circuit and the light will be at full brilliance. A lamp limiter is of value when diagnosing faults in equipment, particularly if using valves. It enables voltage to be applied with little risk of damage.

Thanks, I will set up a lamp limiter but from the drawing I think it will be negative 1 to off switch and live one to live on the 3 pin plug and negative 2 to n on the 3 pin socket and live 2 to the on of the switch, thanks again

 

[73's de Edd]

Sir Ian Mason . . . . .

I had to go get an extra photo of your "Chicken Kit " so that I could then fully see ALL of its feathers . . . . .a la . . . .

https://i.ebayimg.com/images/g/LdwAAOSwCJxaEyJX/s-l1600.jpg

O.K. initially . . . . you have 4 white wires as the primary of that units power transformer and
AM I RIGHT that they had two wires taped together with a bit if black tape, maybe even had them
twisted at their wire ends ?

I am seeing them as being the two SPECIFIC central wires that are needing to be joined, in order to get the two sets of 120vac windings being in series in order to be acepting a FULL 240VAC across the then series aiding windings.

Connecting them that way, and then using the very lowest scale of an ohmmmeter across each of
the assumed 120 VAC windings and then comparing the resistance across the extremes should read twice one windings resistance.

To not take any chances, you can carefully wire up a 60W incandescant lamp in series to make a safe testing of a power up and THEN see if the 110 and 250 VAC windings voltages are THERE after being powered up.

If finding very-very low voltage at the 250 and 120 OR 6.3 VAC windings ONLY one set of 120 V
winding leads need to be reversed. Because the phase reationship is backwards .

I BELIEVE that it will work as first tested, confirming that was the reason for the black tape referencing on the pairing of 2 specific wires.

NOW . . what you have there is a a C13 type of AC connector and the loose power cord, uses its C14 type companion female connector .

On that AC socket unit, that is already mounted on the chassis. Look at it FROM ITS REAR VIEW, with the single BLADE at very top for comparative referencing.
Then that top soldering terminal would be receiving a GREEN wire going to a metal chassis connection for equipment ground.

The bottom left BLADES wire terminal would be the incoming HOT 240VAC that would go to a BROWN wire going to the very tip connection of the fuse holder.

The other side connection of the fuse holder gets another BROWN wire that connects to the CENTER terminal of your mini BLUE cased switch.
EITHER the top or bottom terminal of the switch gets connected to one of the outer WHITE 240 VAC wires.

If you have the ohmmeter handy , flip the AC power switch to where you want its ON position to be, and then check between center switch terminal and the top or bottom switch terminal that shows a short, that will then be the connector of the two that the switch wire to the transformer goes to.

The remaining loose WHITE Wire from the power transformer connnects to the far bottom right BLADE of the AC power socket as the NEUTRAL connection, . . . pray tell . . . where ELSE, could they go . . . its in the book !

The paired white wires get twisted and soldered and taped into a coil, if 120V usage / conversion is
ever needed.

Thassssssit . . . . . now did you real l l l l l l y pay $120 for your Chicken Kit . . . . or $495 for an assembled kit . . . such as some AUDIO-FOOL ! ! ! is asking for one.

73's de Edd

.

 

[Ian Mason]

Sir Ian Mason . . . . .

I had to go get an extra photo of your "Chicken Kit " so that I could then fully see ALL of its feathers . . . . .a la . . . .

https://i.ebayimg.com/images/g/LdwAAOSwCJxaEyJX/s-l1600.jpg

O.K. initially . . . . you have 4 white wires as the primary of that units power transformer and
AM I RIGHT that they had two wires taped together with a bit if black tape, maybe even had them
twisted at their wire ends ?

I am seeing them as being the two SPECIFIC central wires that are needing to be joined, in order to get the two sets of 120vac windings being in series in order to be acepting a FULL 240VAC across the then series aiding windings.

Connecting them that way, and then using the very lowest scale of an ohmmmeter across each of
the assumed 120 VAC windings and then comparing the resistance across the extremes should read twice one windings resistance.

To not take any chances, you can carefully wire up a 60W incandescant lamp in series to make a safe testing of a power up and THEN see if the 110 and 250 VAC windings voltages are THERE after being powered up.

If finding very-very low voltage at the 250 and 120 OR 6.3 VAC windings ONLY one set of 120 V
winding leads need to be reversed. Because the phase reationship is backwards .

I BELIEVE that it will work as first tested, confirming that was the reason for the black tape referencing on the pairing of 2 specific wires.

NOW . . what you have there is a a C13 type of AC connector and the loose power cord, uses its C14 type companion female connector .

On that AC socket unit, that is already mounted on the chassis. Look at it FROM ITS REAR VIEW, with the single BLADE at very top for comparative referencing.
Then that top soldering terminal would be receiving a GREEN wire going to a metal chassis connection for equipment ground.

The bottom left BLADES wire terminal would be the incoming HOT 240VAC that would go to a BROWN wire going to the very tip connection of the fuse holder.

The other side connection of the fuse holder gets another BROWN wire that connects to the CENTER terminal of your mini BLUE cased switch.
EITHER the top or bottom terminal of the switch gets connected to one of the outer WHITE 240 VAC wires.

If you have the ohmmeter handy , flip the AC power switch to where you want its ON position to be, and then check between center switch terminal and the top or bottom switch terminal that shows a short, that will then be the connector of the two that the switch wire to the transformer goes to.

The remaining loose WHITE Wire from the power transformer connnects to the far bottom right BLADE of the AC power socket as the NEUTRAL connection, . . . pray tell . . . where ELSE, could they go . . . its in the book !

The paired white wires get twisted and soldered and taped into a coil, if 120V usage / conversion is
ever needed.

Thassssssit . . . . . now did you real l l l l l l y pay $120 for your Chicken Kit . . . . or $495 for an assembled kit . . . such as some AUDIO-FOOL ! ! ! is asking for one.

73's de Edd

.

Ha ha, no I paid £140.00 about $180 for it but that was with the chassis, you have to remember this once great empire has now sunken in to a pile of manure and nothing is available like it is in the States, it seems that very few British companies/ people actually make their amps available in kit form and I wouldn't know where to begin
if I wanted to make my own from scratch, I don't even know which cable I should be using to run from the RCA inputs to the potentiometer.
Anyway thank you so much for your incredibly detailed answer, I really appreciate your time however if I may can I ask you just a couple of things, you will notice from the pictures attached that the schematic states that the primary must be in series from beginning to end, the transformer has 4 wires, 2 of which have the black tape as you said but if I then connected these 2 together would it not make it parallel rather than series, thanks in advance.

Sir Ian Mason

 

[duke37]

Well spotted Edd.
I would suggest that a resistance check will confirm if the windings are in series bur will NOT check the phase.

If you look at the diagram you will see that the primary current has to go through one winding and then the other. This is series and uses 240V.
Parallel connection would be when the primary current has two ways to get to the other side. This would be used for 120V.
The voltage on each input winding is the same but if you put 240V on a 120V winding, you can say goodby to most of your £140. Make sure a fuse is in the circuit.

 

[Ian Mason]

Thanks duke, so would you be able to explain what would be the correct phase please ie the two wires with the black tape on and the two wires without the black tape, the drawing states that these should be in series from beginning to end, beginning to end, I suppose what I'm asking is how would you do it, which wires would go to the
3 pin plug socket and which ones to the switch, I know the drawing is not very good but I would like to have as many
opinions as possible as I will not do this until I am 100% certain. Once again, I really appreciate your help.
I'm sure you have seen them but the photos of the drawing and the 3 pin plug are in the previous posts.

 

[duke37]

You can have as many opinions as you like but these will not help. You need to know whether the black labelled wires are intended to be connected together or they are start (or end). I would guess they are the start.

One way to find out would be to put the mains into the 250V output winding and measure the voltage on the series connected primary. If you get over 200V you have the two right connections. The primary should then be connected to the mains plug with the fuse and switch in series. There are are arguments as to whether they should be in the line or neutral, I would put both in the line (brown wire).

If you are not too far away from Whatstandwell, I could soon sort it for you.

 

[73's de Edd]

Sir Ian Mason . . . . .

Looking at the NEW photo #2, where the terminals can now be seen . It looks like the BLACK taped connections would be like . . .either start or finish sets of the two windings.
That would mean that you need to take out the twists and end up with straight wires again.
Then consider that:
The bottom wire position, on the entry to the transformer is being a start of one primary winding
and that
The second wire position up, on the entry to the transformer, is being the end of that winding.
Then the third wire position up, on the entry to the transformer , is being a start of the second primary winding.
The fourth wire position up, on the entry to the transformer , is being the end of the second primary winding.
With 4 loose white wires.Take ohmmeter and confirm continuity being between 1st and 2nd up wires and then 3rd and 4th up wires. That confirms them as being being the two 120 VAC primary's.

That then would have you using the VERY bottom white wire as one 220 VAC input wire, the second and third wires up, get connected together and coiled up and taped.
That then leaves the very top wire as being your other 220 VAC wire connection.

To confirm their then having the proper winding phasing, do as Sir Duke sez and pull one BLUE wire completely free from its already connected circuitry, leave the other BLUE lead as it was. Only one needs to be totally lifted.

Take your meter and set functions and range to where you can read 220 VAC and test at a wall power connection and leave metering setting exactly as it was, and move the probes to the agreed upon two white wire extremes.
Get 220 from a plug and some interconnecting wiring to go to the two BLUE winding wires , of which one is being a sole wire connection .

Then you only need to plug into ---and out of an AC outlet for that second or so that your meter needs to display a reading.
If that reading is 200 volt- ish or so you have proper phasing connection of all of the WHITE wires.
If the phasing is incorrect, the two windings magnetic fields cancel out, and there is close to zero voltage out from the two WHITE wires.
Come back for further instructions just in case that happens

73's de Edd