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WAD Problems For questions and answers re older World Audio Design Projects

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  #11  
Old 5th February 2006, 09:28 PM
John Caswell John Caswell is offline
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Default Re: I've had a bad day!!!...please help!

Hi Gerry,
This thread got a little highjacked and confused so will try to make some sense of it.
If you have 0V dc or ac across the heater pins 3&4 of the 6AU6 I guess the wires to the heater pins may be broken somewhere or there is a fault in the bridge rectifier circuit that feeds the 6AU6. Can you see the heater glowing on the "faulty" amp if not then you need to investigate the wiring/bridge rectifier especially if the 5687 heaters are glowing.

Regards

John aka Dr John
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  #12  
Old 6th February 2006, 11:37 AM
Gerry Gerry is offline
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Default Re: I've had a bad day!!!...please help!

John

Thanks. I will have a look this evening and maybe give you a call if I get stuck? The 5667 is fine.

Regards
Gerry
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  #13  
Old 6th February 2006, 04:09 PM
Richard Richard is offline
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Default Re: I've had a bad day!!!...please help!

Quote:
Originally Posted by Gerry
Richard

I've tested both amps and get 326R (on both) measuring chassis to pin 7!

I rechecked the voltages on both amps and swaped valves also to check..

amp1 amp2 WAD fig

Pin 7 1.578dc 0dc 1.5dc

Pin5 103.7dc 171.7dc 115dc

h to h 6.44dc 0dc 6.3dc

Same when valves swaped over.
Any ideas?

Thanks
Gerry
Hi Gerry, Cathode resistance is correct so, as John says, heater looks the culprit. Is it glowing? If not or only a little check the wiring then change the bridge rect and cap if no fault found.

Rich
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  #14  
Old 6th February 2006, 07:24 PM
Gerry Gerry is offline
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Default Re: I've had a bad day!!!...please help!

Richard/John
Wiring looksok, but I will re-solder the joints in case. Anyway to test (meter) the Bridge rectifier?
thanks for the help.
Gerry
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  #15  
Old 7th February 2006, 02:51 PM
Richard Richard is offline
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Default Re: I've had a bad day!!!...please help!

Gerry,
You might be able to test it if you took it off but it could also be the cap. Only pennies, I'd just change them both from Maplins. If you've a local store you can check availability on the website,
Bridge rect WO2 AQ96E
http://www.maplin.co.uk/module.aspx?...=19088&doy=7m2
Cap 4700uF 16v VH57M
http://www.maplin.co.uk/module.aspx?...=13472&doy=7m2
Rich
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