Hacker Cavalier Loud Noise

[martinpinner]

I have redone the cartridge lead and I still have the problem. I disconnected the turntable and only turned the switch enough to power it on.Within 30 seconds it gets a little crackly and starts to get worse and within a minute it goes into a continuous loud noise. I have not looked at the amplifier as Maurice has suggested as I cannot identify it (excuse my ignorance) but only the mains/output transformers .What is frustrating is I was making adjustments to the pick up yesterday with the player switched on/off for over an hour and it did not happen. Any assistance would be appreciated. Thanks Martin

[martinpinner]

With the capacitors/resistors replaced should any of them be fitted as positive/negative connections. I have replaced without regard to them being + or -.

[Station X]

Only electrolytic capacitors will be marked + and/or - and they must be connected the right way round. Generally -ve to chassis in valve equipment.

[peter_sol]

The noise problem may be caused by one or both of the ECL86 valves

[martinpinner]

Thanks for the response. I have fitted some electrolytic caps to replace but these were not marked + or - and not sure how I determine. As they are replacing the 50uF caps I am not sure what is meant by negative to chassis.

With regards to the Valves can these be tested or will I have to look for replacements. Thanks Martin

[ms660]

Photo's?

Lawrence.

[TonyDuell]

'Negative to chassis' means essentially what it says. The negative terminal of the capacitor is connected to the metal chassis of the amplifier.

I assume the original capacitor was a metal can mounted on the chasss with several solder tags on the bottom end. Those tags are the positive connections for the capacitors in the can. The negative connections all go to the metal can, and therefore to the chassis when it is mounted.

(As an aside, if you have one of these cans with 2 tags on the bottom, then 99% of the time it is not a single capacitor connected between those 2 tags, it is 2 capacitors with the +ve terminals going to the tags and the -ve to the can.)

So if you replace this capacitor with several modern ones, which have positive and negative wires, you have to connect the positive wire to whatever was connected to the tag and the negative wire to the metal chassis.

[Station X]

I've never come across an electrolytic capacitor which wasn't marked with its polarity. Modern types tend to have a string of arrows on the side which point to the negative terminal.

[Nickthedentist]

Yes. So as Lawrence suggested, a photo or two would be great, please.

[martinpinner]

I am attaching photo's of the electrolytic capacitors I have used in replacement. The red 50uf replaced with the blue and the blue 8uf with the black. On neither the old or new capacitors is the polarity marked!

[martinpinner]

I have just read Nick's comment and can now see the markings on the blue capacitor. I was just looking for a + and - at each end of the cap. Unfortunately I still do not see how to fit them with the correct polarity!I presume incorrect fitting could be causing the problem.

['LIVEWIRE?']

Do you have the service sheet for the GP42. It should be available for £1.99 from the VRSD link 'up top'. This will show the correct polarity of the electrolytic capacitors - in most, if not all cases, the Negative terminal connects to chassis via the common negative wiring. (The golden rule, as always, is to take note of where the connections are before removing the old component!) Some of the capacitors in youtr pictures have one end plain metal - this is the Negative, and the other has a plastic or rubber insulated 'cap' - this is Positive. As to wiring electrolytic capacitors (and some other components) with incorrect polarity - in the words of Corporal Jones (Dad's Army) 'They don't like it up 'em!'

[julie_m]

On older electrolytic capacitors with one lead coming out of each end, usually one end will be bare metal and the other end will be plastic or some other insulating material. The metal end is the negative end.

By the way: If you were to take a brand new electrolytic capacitor that had never been charged, and connect it into circuit the wrong way round, it would actually work fine! The polarity of an electrolytic capacitor is fixed for life, the first time it is charged.

[Herald1360]

Shouldn't that be "never been formed"? But that's part of the manufacturing process, before they even get as far as brand new.

[peter_sol]

With regards to the valves and testing, no you can't test them for noises.

[martinpinner]

Thanks for all the responses but just to be clear am I safe leaving the capacitors fitted with the wrong polarity and not be giving me the loudness problem.Also, if I need to look at replacing valves can anyone recommend where to purchase or should I just go to Ebay.

[Edward Huggins]

Don't still quite understand why you are still confused about the capacitors. Can you re-word your query pease? As regards buying new valves, why do you think you need them - they are most unlikely to create the kind of noise you describe. I just don't think you need them! So first swap them over and check the pins for oxidisation. See how it sounds then. If you tap them when the amplifier is on, is there a "ringing" sound in the speaker? If you are determined to buy 2 new valves.......well, that's your choice. Ideally you should get what are desribed as a "matched pair" as you have a push-pull amplifier. These can be bought from Chelmer or Kenzen or Billington - all these are easily searched out on the Web. Edward

[julie_m]

If you had fitted an electrolytic capacitor with the wrong polarity, it most probably would have exploded when you first applied power! Any chance of some pictures?

The symptoms you describe sound like a bad connection somewhere upstream of the preamplifier stage. Try cleaning the valve pins with wire wool and a drop of Servisol or similar, and look for dry joints on the control potentiometers and associated components.

[martinpinner]

The photo's already posted show the capacitors I have replaced - some are fitted correctly. None have exploded and therefore assume they are OK to leave. I was just questioning if by them being fitted incorrectly whether it may be contributing to the loudness issue I have. I am not keen to replace the valves but as it was suggested that they may be the cause I thought they may need replacing. Apologies for my ignorance but I am learning and keen to get it operating.Thanks.

[Station X]

Circuit courtesy of NTD.