Question Harman kardon citation 16 variable resistor

Badula

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Hi all. I need some help.
I have recapped art Citation 16 amp. Unfortunately it suffers a common problems on these amps it seems. The variable resistors are finished.
Is there someone who knows what kind I should replace them with? A link perhaps?
I know the 500ohm one. But what does (IM ohm) mean?
Thanks
 

Badula

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Are you sure that one isn't 500k ohms (500,000 ohms)?

Do you mean variable resistors on the PCB (known as presets) rather than rotary controls (like volume/ tone controls?
The variable resistors on the PCB board. One is for the idle current. And the other for Output “idle”
As I can se in the service manual the is no K in the 500. I will attach a file
 

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Gray

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Any kind? Or any brand?
Provided that they're physically the same (the 3 pin / leg spacing / horizontal or vertical type).
Whatever types you're replacing, go for the enclosed, rather than the open (skeletal) types.

Search 'preset resistor' and you'll see a few.

Use an accurate meter to set them 👍
 
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Badula

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Nov 11, 2023
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Provided that they're physically the same (the 3 pin / leg spacing / horizontal or vertical type).
Whatever types you're replacing, go for the enclosed, rather than the open (skeletal) types.

Search 'preset resistor' and you'll see a few.

Use an accurate meter to set them 👍
Thank you very much. As one replied and questioned 500ohms. Is this a correct value ? There is no K in the 500 ?
 

Badula

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Yes, assuming the manual is correct, then VR2 is 500 ohms.
Hi again!
Problems… got the new variable resistors…
There is 30 volt!!! On channel A (blown transistor?!) 🤬 and Channel B “kinda works” but as hotter it gets on channel B the idle current lowers!?! Bad emitter resistors ?? It goes even to Minus ➖ as hotter it gets ? Ahh son of a *****… 😤😭
 

Badula

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It seems also that the PA/UA739pc IC are spooky to… read on many threads that these Opamps are bad… any one out there who has knowledge about these ones?
 

Gray

Well-known member
Hi again!
Problems… got the new variable resistors…
There is 30 volt!!! On channel A (blown transistor?!) 🤬 and Channel B “kinda works” but as hotter it gets on channel B the idle current lowers!?! Bad emitter resistors ?? It goes even to Minus ➖ as hotter it gets ? Ahh son of a *****… 😤😭

It seems also that the PA/UA739pc IC are spooky to… read on many threads that these Opamps are bad… any one out there who has knowledge about these ones?
☹️
Time to decide if / how much you're prepared to pay for a professional repair.
Get reliable estimate(s) first 👍
 

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