Can anyone shed some light please? - diyAudio
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Old 13th August 2011, 11:06 PM   #1
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Default Can anyone shed some light please?

My amp , wharfedale 2050A was working ok last night , tonight nothing , the light comes on when I press the power switch on but usually I hear a click and the music comes on.
Tonight no click , no music.

The worrieng bit is when I switch the amp off the light gets to about half brightness even though the power switch is off and stays like this for 20 or so seconds before fading out. It has never done this before.

Any suggestions or ideas?

Also , when the amp is switched on I can hear a humming coming from it.
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Old 14th August 2011, 12:01 AM   #2
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ok this isnt right is it , I decided to check the fuses and pulled them out with some pliers, good job I did because as they came out they arced against the fuse holder, this was with the power lead unplugged.
What are your thoughts guys?
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Old 14th August 2011, 03:06 AM   #3
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My guess is that you aren't getting power supply to your output. The residual lights and spark on fuse removal means your power supply is likely working. Slowly diminishing charge on rectifier caps. The familiar click sound is likely a delay relay that is set not to switch in untill supplies are up to speed. Some amps won't permit such delay relays to engage unless supplies reach a certain level or all are present. Check what supplies you are able as a start. Look for relays and check voltages waiting on input side.
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Old 14th August 2011, 09:33 AM   #4
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Isnt the relay part of the speaker protection circuit?
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Old 14th August 2011, 09:47 AM   #5
AndrewT is offline AndrewT  Scotland
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Probably, but it can double as a mute during start up and a mute during shutdown.

The mute during start up appears not to be working. There could be a DC detect circuit on the amp and this is sending a "fault signal" to the muting relay telling it to not unmute.

You need to post pics and schematic and test measurements.

In the meantime build a bulb tester and only power up the faulty amplifier through it.
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Old 14th August 2011, 09:54 AM   #6
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I'm afraid I dont have any test equipment, nor a schematic and I have no idea how to build a bulb tester.
It's not looking good is it?
I could take some photos but doubt anybody could diagnose the problem through them alone, unless there was something obviously wrong with it.
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Old 14th August 2011, 12:04 PM   #7
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OK guys , I think I might know what has happened. My 1 year old daughter may have pulled the wires out of the back of the speaker and put the volume on full.
My partner said she tried to put a record on and when she switched the amp on a massively loud noise came from the speakers (so loud she couldn't even tell if it was music or not), she turned the volume down straight away and after that there was nothing more from the amp.

Does this make any sense?
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Old 14th August 2011, 12:55 PM   #8
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Some photos of the inside of the amp here.

Wharfedale 2050A, A rarity+ TEN Audio upgrade, Warranty | eBay

Ive just had another word with the missus and she said the amp was on CD, she switched it to phono (a record was already playing) and it made a huge noise so she switched it straight back to CD, turned the volume down then switched back to phono , at this point the amp was dead.

Might she have blown the fuses? One has blown but I though it blew when I tried to remove it and it arced against the fuse holder, also , if only one blew would both channels be quiet? Perhaps I need to replace both to be on the safe side?
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Old 14th August 2011, 01:19 PM   #9
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Who makes maintenance and repair of this model and from where I can order a service manual of this model?
here an additional link to this amp model:
dual concentric volume pot needed?
I have save some pics from ebay, because there this pics will be deleted after short time.

BTW - this model looks similar to Linn's vintage amp "INTEK" - perhaps both models comes from the same factory.

Quote:
Originally Posted by robgilmo View Post
Ive just had another word with the missus and she said the amp was on CD, she switched it to phono (a record was already playing) and it made a huge noise so she switched it straight back to CD, turned the volume down then switched back to phono , at this point the amp was dead.

Might she have blown the fuses? One has blown but I though it blew when I tried to remove it and it arced against the fuse holder, also , if only one blew would both channels be quiet? Perhaps I need to replace both to be on the safe side?
Huge noise (perhaps shot noise) by the switch position "Phono" means, that in this aera must be unwanted effects through corrosion/oxidation (mostly the MM/MC switch). If I am right, remove this swich and solder wires at this place according the cartridge, what you have in use.
Where exactly are the fuses located in the circuit? In serial to the loudspeaker output or in the DC voltage rails (supply-power buffer)?

It is best to check before replacing the fuses the output transistors - mounted on the big heatsink - with an ohmmeter to internal short-circuit between B-E, C-B and C-E.
Attached Images
File Type: jpg LINN INTEK front.JPG (73.1 KB, 58 views)
File Type: jpg LINN INTEK inside BUFFER.JPG (109.2 KB, 57 views)
File Type: jpg LINN INTEK inside RIAA.JPG (140.0 KB, 54 views)
File Type: jpg LINN INTEK inside top.JPG (75.9 KB, 54 views)
File Type: jpg LINN INTEK inside top-II.JPG (180.9 KB, 53 views)
Attached Files
File Type: pdf Wharfedale 2050A.pdf (104.3 KB, 18 views)

Last edited by tiefbassuebertr; 14th August 2011 at 01:37 PM.
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Old 14th August 2011, 02:28 PM   #10
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Hi, they do look quite similar. I am afraid I haver no idea as to what part of the circuit the fuses are in. I think my best bet would be to let someone who knows what they are doing have a look at it.
Do you guys think this would be an expensive fix? Its not a very valuable amp however to find its equivalent in a new amp today could prove costly.
I t5hink it was the sudden pulse of current when switched from CD to Phono that blew something, output transistors perhaps?
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