Hum noise from my Rock-Ola 459

[Paul]

Hi Folks.

I have continued to try sort the above hum problem, taking into consideration of the much appreciated feedback from previous threads.

The current situation/findings are:

I noticed a large old looking transformer located (very closely) between the two very large speakers.

I tweeted with the cables and moved them around a bit with the aim of reducing their cross-over and increasing their distance from the transformer. Hum was still present.

Cutting a long story short, I disconnected one of the large speakers, removed the other to outside the jukebox. Approximately 4ft from the transformer. I extended the speaker wires to the now, external speaker. 

Switched on the jukebox, no hum from the connected external speaker. Played a record and sound was great.

Fitted the speaker in situ and reconnected both speakers. The hum returned.

OK. I then took a totally different speaker, one that is much smaller, connected it up, placed it beside the transformer, switched on the jukebox (both large speakers were still in their positions in the jukebox but were disconnected) and no hum from the small speaker.

Removed the small speaker, re-connected the two large speakers, switched on the jukebox and hum returned.

My conclusion is that there must be some type of magnetic/electric interference between the large speakers and transformer in relation to their distance from each other. 

I've thought of trying to relocate the transformer, use of shielded cable to the speakers, or relocate the speakers externally away from the transformer.

Can anyone help me figure out what to do next! It is a Rockola 459 model.


Many thanks

Paul




 

[Ron Rich]

Hi Paul,
What is the "transformer" -- What does it do ? Is i a lamp ballast, by any chance ? Ron Rich

[Paul]

Sorry Ron.

I recently replied to your questions above.

However, I cant see it anywhere!

Did you receive it?

If not, I can resend.

Thanks

Paul

[Ron Rich]

Hi Paul,
I don't think so -- did you forget to hit "send" ? ( I have forgotten that a few times-kick myself every time I do !) Ron Rich

[Paul]

Thanks Ron.
Here goes.

The transformer is large, old looking, dark green in Colour.
It is mounted on a large alloy box, which in turn is mounted to the cabinet.
The lower part of the alloy box has a power lead entering it. The power cable has signs of a metal internal shield.
There are two green wires leaving the top part of the alloy box and enters into the top part of the transformer.
Also, at the top part of the alloy box, there is a fixed plug that connects to another free moving plug, with cables connecting to the lower fluorescent (not working).

I don't see any other cables/wires with reference to the transformer assembly

The spec of the transformer is as follows:
9-73
ROBERTSON TRANSFORMER CO
CAT. 1.2525
25W 50A 220V 50HZ
BLUE ISLAND, ILL.
MADE IN THE UK.

The only function of the transformer, that I can see, is for the fluorescent light.

What I have noticed is that there are four wires, enclosed in a cream-coloured plastic sleeve, very closely running parallel to the transformer assembly. These are the speaker cables. I did re-route the speaker cables, but had no effect to the hum.
I'm soooo baffled. The speakers are very large and the transformer assembly is positioned between them. I am now thinking that a kind of electromagnetic effect is taking place, giving rise to the hum.

Whats your thinking/suggestion Ron?

Much appreciated and thanks

Paul

[Ron Rich]

Hi Paul,
Yes--Robertson made (still may ?) fluorescent lamp "ballasts", aka "transformers". But "Blue Island Ill--made in the "UK"" ?? When did the state of Illinois, move to the UK ?? 1. Be sure that that ballast ( and whole phono ) is grounded well. If that does not stop the "hum", try re-routing the wires going to/from the ballast. 2. Try twisting the wires in pairs, going to /coming from, the ballast. 3. Should that not solve the problem, Replace the ballast. Ron Rich

[Paul]

Hi Ron.

Excellent suggestions. Will work through them.

Ron, I'm still learning jukebox terminology and if I could please ask you the following:

On your point 1: Can I ask your help on this one. I have heard of the term "Grounding". Am I right in saying that I would remove and clean the earthing terminals and their contact surfaces?

Yes. I can re-route the wiring.

On your point 2: Yes. I can twist the wires.

On your point 3: Again, can I ask for your help on this one. Do I only need to take the spec of the current ballast and use those details should I need to/decide to buy one? Or, would it be best for me to remove it completely and hopefully source a supplier here in the UK?

Thanks Ron

Paul

[jukenorman]

Paul, there is something strange about the spec of the transformer that you have posted.
25W 50A 220V 50HZ

You said the transformer was large. If it was 25W, it would be small! If it was 50A, it would be enormous. Something is not right - can you post (or host somewhere) a picture of that data plate so that we can have a look at it?

Norman.

[Ron Rich]

Hi Paul,
Yes--"Grounding" in the USA is, "earthing" elsewhere !
Is that ballast connected to a 120, or 240 volt source ?
Like Norman wrote above-- re-check what it says on the ballast ?? ]
Ron Rich

[Paul]

Hi Folks.

Thank you for your feedback.

Voltage rating in the UK is 220-240V.

I have completely removed the front door of the jukebox, allowing me easier and, clearer access to its inner.

Overall dimensions(centimetres)

1. Transformer: L=16 W=6 H=4.5 cms

2. Alloy box (Transformer is mounted on this box): L=23 W=8 H=4 cms.

I have a much clearer view now of the transformers spec. All readings above, EXCEPT FOR THE AMP READING. There is a small point/dot in front of the 50. It shows .50A and can only assume this is a half amp reading.

I will try and load up and post a picture of the transformer assembly.

Many thanks and much appreciated

Paul

[Paul]

Hi Folks.

I have been reading the "Threads, Posts, Polls and attachments" section under the "Help" page.

I would like to attach a picture of the above transformer assembly.

However, I cant see the "Add attachment button" on the thread page.

This would be a very powerful and useful tool to use as it expresses a wordy script into a picture/diagram.

If you have the time, can I please ask if you could forward me a point procedure of how to use the add attachment.

Only thing I can think of is that I need approval from yourselves.

Many thanks

Paul

[jukenorman]

Hi Paul,
Yes 0.50A makes a world of difference! I had wondered whether you had an import model (US) and the transformer might have been a voltage step down but that is clearly not the case (it's not big enough). I would say that the metal box is an irrelevance. It could well be a fluorescent ballast. If my memory serves me (it doesn't always), there is a socket on the power supply assy that supplies the lighting. If you disconnect the lighting there and the hum vanishes, then you know it's interference from there.

I think I may have said it before but maintaining these older fluorescent circuits in Europe is becoming incresingly problematic because of environmental regulations covering fluorescent tube manufacture - meaning that the (newly purchased) tube won't strike. It's now either fluorescent tubes with electronic ballasts or LED lighting if you don't have NOS tubes.

Norman.

[Ron Rich]

Hi Paul,
Read our "FAQ's page-- Photo's are no longer allowed. Sorry, but you will need to post it elsewhere, and link to it. As far as I'm concerned, there is no need to do such for a lamp ballast-- either the tips above will work, or you will need to replace it. Ron Rich

[Paul]

Hi Norman.

I hope you are well.

I have worked through the suggestions put forward by Ron.

I have cleaned all the earth cable connections and did a continuity test for each of the earthing cables and all seems good.

I have re-routed cables going to and from the transformer.

I didn't twist the cables as they seem fine.

Still getting the hum.

I totally removed the front door of the jukebox and reconnected the cables. Hence, at this point, the door, speakers etc are approx 3 ft from the main workings of the jukebox. My thinking here was to totally isolate the transformer/speakers etc from the other bits and pieces of the jukebox.
Hum still present.

Regarding your point Norman, I disconnected the lead coming out of the transformer (located at the top end of the transformer) to the lower fluorescent tube a while back and has remained disconnected since.
Hum is still there.

Norman, from your suggestion above, the transformer, supplying the lower fluorescent tube, does indeed have a power plug supplying it. The power line entering the transformer is located at the lower end of the transformer. Do you mean to disconnect it, then switch the jukebox on and listen for the presence of the hum?

Also, I did, however, remove the transformer and noted some of the wires within, have been previously cut and reconnected again.

In addition, the jukebox is served with another ballast, situated at the top part of the jukebox. This serves a working, top fluorescent tube. I have not been able to get the lower fluorescent tube to work, which is interesting too. However, I've given up on that one, but just for the moment!

Many thanks

Paul

PS. I need to learn to upload photos as it will help clarify my points.

Thanks Norman

[Ron Rich]

Paul,
If the lamp won't light most likely that ballast is not the source of your hum ! Yes-- dis-connect the power plug to that ballast and see if the hum is still there-- then dis-connect,or just remove the other lamp-- hum gone ?? And you should have twisted the wires going to, and coming from that ballast, as much as possible ! Ron Rich