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Old 20th May 2004, 10:27 PM   #1
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Default My darling is giving me hell!

Enclosed is a picture of how I have wired up the Parefeed Darling.
But the weirdest thing is happening...If only feed it with one channel...sound emenates from BOTH speakers. From the one a little distorted though. If I feed the same signal into the other channel...there is no sound from EITHER speaker?

Baffled!?!?!?? Anyone have an idea what it can be? I was thinking it might have something to do with the CCS's and no decoupling from the PSU?

Regards,
Bas
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Old 21st May 2004, 03:02 AM   #2
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Nothing on the scope? Oscillating maybe?

Although there are numerous things that I would do differently, and some of which are bad design practice, I'd check the 6.8uF cap. Everything's fed with a CCS but I still don't like it so small.

Tim (who recently completed a preamp drawing maybe 20mA but using 220uF in the PSU anyways )
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Old 21st May 2004, 06:44 AM   #3
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Well just like I would do at work when a control valve isn't working you start troubleshooting at the PSU. You could also hook up a tone generator and test for a signal after each stage. The only thing the two channels have in common is the power source (generally speaking) and the heater supply. That is where I would start. Also a faulty tube could allow a signal to pass from the cathode to the heater( or vice versa ) if the 1626 is a indirectly heated tube. This is just a semi-educated guess. You should be able to find it with a scope fairly quickly.
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Old 21st May 2004, 08:15 AM   #4
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Thank for helping...Problem is I don't have a scope...I'll just recheck everything...

Cheers,
Bas
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Old 21st May 2004, 09:27 AM   #5
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If you have a analog multimeter you can check the output of each stage of the offending channel in AC mode and you will be able to narrow it down to which stage the problem is rudely lurking in. Double check every connection against the schematic and be on the lookout for cold solder joints. If you took your time and concentrated when building the circuit then the problem should be easy to identify if approached in a logical step by step fashion. Check the B+ at the plates of the tubes and check across the cathode resistors for the desired bias voltage. Are the tubes NOS? Have they been tested for shorts? Post back with any strange readings or if you let the smoke out of anything.
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Old 21st May 2004, 09:40 AM   #6
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Bas,

What is the difference in voltage between +B and +b ?

(Glad it's only this 'darling" you're having problems with... )
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Old 21st May 2004, 11:55 AM   #7
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Quote:
What is the difference in voltage between +B and +b ?
150volts dc...well dc...;-)

Quote:
Glad it's only this 'darling" you're having problems with
Well it's not actually..but that the other one I don't ask questions about on forums....there is no help possible there..!!!

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Are the tubes NOS? Have they been tested for shorts?
No they have not been teste for shorts...I might try some others...and will report later if I find some odd readings...

Cheers and thanks y'all..
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Old 23rd May 2004, 08:24 PM   #8
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Bas,

double check your wiring first, a mistake is easily made, hence no output from the other channel at all.

Second, replace all the CCS with 10k high power resistors for troubleshooting. See if you get sound out of both then.

Dick.
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Old 23rd May 2004, 08:55 PM   #9
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Hi Bas, Ik have some new 1626s in stock if that may help you. Also a scope can be arranged....
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Old 23rd May 2004, 09:00 PM   #10
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Quote:
Originally posted by Sch3mat1c

Tim (who recently completed a preamp drawing maybe 20mA but using 220uF in the PSU anyways )

hehe-20 mA........
just 20 mA.......
again.........
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