“Manky thing” in HMV 2010 model

[Notarfff]

I’ve opened up my HMV 2010 with a view to follow dekatron dereks/Dave’s posts regarding basic checks, I was looking for anything that seemed weird, burnt, loose wiring etc.
All looks good, apart from this thing, which I think is part of the transformer element of the player (don’t laugh if I’m wrong) it looks , well, manky.
The player works pretty well, but the volume is pretty unimpressive but then again it’s only 5watts per channel ... I think
And there’s not stereo, which I think is down to the cartridge which I’m testing later.
And there’s a bit of hum, so I was looking for the section on smoothing capacitor tests and I can’t find it now.
Can anyone help with all of these questions, sorry , I am new to electrical stuff and I didn’t listen in physics, so I can only remember that it’s dangerous, and yes it is unplugged from the mains !! Thanks in advance

[Nuvistor]

A good starting point.
https://www.vintage-radio.net/forum/...ad.php?t=75401

5 watts can be loud.

[Notarfff]

Cheers frank, yeah, found it and I think I checked the smoothing capacitor ok and it seemed ok, I’ve just no idea what the other thing is and whether it’s meant to look like mine.

It’s seems quiet, too quiet, it’s a transistor not valve , but my knowledge is fairly close to nil right now

[Station X]

Service information can be downloaded here:-

https://www.service-data.com/section.php/3753/1/2010

The "manky " looking object is the mains transformer. All you need to do is check that you have 22 VAC across its secondary winding and 29 VDC across the smoothing capacitor.

[Notarfff]

That’s awesome, thanks so much, I really appreciate the link to the service manual.

[paulsherwin]

Your manky thing does look like the mains transformer, as Graham said. I can't see anything obviously wrong with it.

[crackle]

I can't see any manky looking items.
It all looks normal to me.

Mike

[Notarfff]

Many thanks fellas for the advice and pointers to other threads and resources, very much appreciated.

I’ll keep persevering and hope I don’t make it any worse than it is.

[ben]

Many transfomers of this era had waxy insulation, this in turn probably picked up a bit of dust plus the heat in operation would cause some discolouration. I agree it doesn't look as neat as those later manufactured. But it looks fine to me, as in no sign of burnups. Don't judge by appearances! ;-)

[Radio Wrangler]

The manky looking thing is the mains transformer and it's gone a bit manky on the wax it was impregnated with. Don't try to clean it. That can cause problems.

The silvery square thing to the right of it, held down with a nut and a large washer is the rectifier.

The transformer takes the mains voltage and turns it into an alternating magnetic field in its metal core (by means of a winding of thin, varnished wire. The transformer then has a second winding which 'catches' that magnetic field and turns it back into alternating electricity. By having different numbers of turns in the two windings, the transformer can change the voltage. In this case, 240v in and about 22v out.

Because there are two windings, insulated electrically from each other, the transformer not only changes the voltage for you, it also creates a safety barrier.... it's said to provide 'isolation'

The voltage out of the transformer is still alternating, just like the mains. It's a scaled-down version at a voltage more suited to transistor circuitry.

The silver square thing is a bridge rectifier and contains four diodes. Diodes are one-way valves and are used to re-route the connections from the output of your transformer, so that current of always the same direction can be created.

This rectified power is lumpy. It varies between a peak value and zero. It would be useless for powering an amplifier, there would be an awful buzzing.

The shiny silver canister thing below the transformer is a large reservoir capacitor. An electrical store. Think of it as acting like a battery powering your amplifier smoothly, while the transformer and rectifier act to recharge the capacitor in little bursts whenever the mains voltage is high enough (I.E. 100 times per second, on the mains peaks) The bridge rectifier is clever enough to use both the positive and negative peaks of the mains. The rectifier also prevents the capacitor discharging backwards into the transformer winding.

Anyway, so that's what the things in your picture do.

David

[Station X]

Very good! Almost worth a sticky, but no one reads them.

[Notarfff]

Originally Posted by Radio Wrangler

The manky looking thing is the mains transformer and it's gone a bit manky on the wax it was impregnated with. Don't try to clean it. That can cause problems.

****** BRILLIANT !! Thanks so much for taking the time to write that, I understand it, I did wonder about the square thing. And I kinda guessed about the smoothing capacitor, I must have listened during the capacitor lesson in physics.

You should be a school teacher !!

[Notarfff]

Originally Posted by ben

Many transfomers of this era had waxy insulation, this in turn probably picked up a bit of dust plus the heat in operation would cause some discolouration. I agree it doesn't look as neat as those later manufactured. But it looks fine to me, as in no sign of burnups. Don't judge by appearances! ;-)

Thanks Ben it was the waxy paper that worried me, I wondered if something had melted.

It works fine though, so I guess not, and nothing else looks “burnt” so maybe it’s holding up , not bad for 55 years ...

[Station X]

Originally Posted by Notarfff

It works fine though, so I guess not, and nothing else looks “burnt” so maybe it’s holding up , not bad for 55 years ...

Why not do some tests? The circuit diagram shows what voltages to expect where. You can't generally tell whether a component is faulty just by looking at it.

[Notarfff]

Now I have the circuit diagram, thanks to you providing the link, I’m seriously considering just that.

I’m going to ask my stepdad to guide me as he is a retired electronics maintenance engineer, I have a multi meter but don’t really “understand” what I’m doing, I’m doing things by rote rather than understanding.

The whole thing has really piqued my interest in electronics a subject I’ve never understood and I’m sick to death of software as I’ve done that for a living for thirty years...

[Radio Wrangler]

Originally Posted by Notarfff

You should be a school teacher !!

Best not. I'd scare the living daylights out of headmasters

David

[Edward Huggins]

Originally Posted by Notarfff

The player works pretty well, but the volume is pretty unimpressive but then again it’s only 5watts per channel ... I think
And there’s not stereo, which I think is down to the cartridge which I’m testing later.

Well surely 5 watts per channel is pretty loud if it's working as it should!
When you say "there's not stereo", what does that mean i.e. can you only hear one channel properly?
To test this, switch your Stereo-Mono selector to Mono, put on a Stereo record and you should hear an equal volume level from both sets of loudspeakers.
Then switch to Stereo and the volume levels should be similar, but of course with different content on each channel.

[PaulR]

The parents of friend had one of these. It would rattle the tiles on the roof if turned up high playing Status Quo so something is amiss if it sounds quiet.

If the tests suggested by Edward are inconclusive could you take the leads off the back of the cartridge? If so try touching the terminals on the ends of the leads. You may need a small screwdriver or something else pointed to get inside the insulation. Two of them should produce a loud hum. One should be in one speaker and the other in the other. If you turn up the volume the hum should get quite loud. Don't forget to photograph or make a note of where the leads went before you take them off.

The Isle of Man is a favourite place of my wife and me. Hopefully we will be holidaying there next summer.

[Notarfff]

It certainly is very quiet, something is wrong for sure. Glad you like the IoM, it's not for everyone, but I like that, keeps it quiet for the rest of us.
Drop by when you come over ....and bring your multi meter

[Notarfff]

Originally Posted by Edward Huggins

Well surely 5 watts per channel is pretty loud if it's working as it should!
When you say "there's not stereo", what does that mean i.e. can you only hear one channel properly?
To test this, switch your Stereo-Mono selector to Mono, put on a Stereo record and you should hear an equal volume level from both sets of loudspeakers.
Then switch to Stereo and the volume levels should be similar, but of course with different content on each channel.

Thanks Edward, yes, on mono I get sound through each channel, but on stereo only on one. so the cartridge has been pointed out as a likely problem, I am going to thoroughly check this w/e, didn't want to rush as the wires leading from it are hair-like and I don't want to break anything.
I suspect this is all going to lead to a new cartridge and the ronettes are not cheap?
What else could it be? if it were something else I'd notice it in MONO yeah?