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Cleaning volume and balance pots


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I have an HK 630 (old Dual Power supply unit) that is occasionally malking noise. Fiddling with the bass or volume control seems to make the noise go away.

I would like to clean the inside of the unit, and clean and lubricate the switches. I have never done this before. What products do I use, where do I get them and how do I do it?

Thanks,

Chris

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OK. I'm sure that you will get some advice involving expensive products and exotic proceedures. There is a lot of voodoo out there which prompted PWK to issue the famous yellow BS badges. In the age, shortly after the earth cooled, when I was a HS kid working a bench in a radio/(soon to be) TV shop, we had syringes and a pot of carbon tetrachloride that we spewed into noisy controls. It worked well until California determined that the practice would send us into a frenzy of self abuse or something.

Now, I use a product from Radio Store. "Contact/Control Cleaner & Lubricant" 64-4315. It is excellent. WARNING, do not spray this product into a paper bag and put it over your head.

DR BILL9.gif

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My previous reply was based on repairing industrial equipment with zillions of pots which if they went bad would drive you absolutely nuts if you squirted the tri-clo in them. Yes they would work for a while, but only for a while. We would substitute wire wound pots if possible and maybe 5 turn and 10 turn pots which would expand the "sweet area" where it would constantly end up position wise depending on the circuit. Then instead of setting the level to -10db it would be -10.0 db. You gain a ton of calibration adjustment at that specific point---it doesn't make the circuit more accurate but the result seems like it is---. Wheras before the -10db would fluctuate from -10.7 to -9.8 because of bad carbon surface with the 5 or 10 turn pot you could nail it at 10.0 with great ease and peace of mind.

JJK

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On 3/2/2005 2:49:22 PM JJKIZAK wrote:

My previous reply was based on repairing industrial equipment with zillions of pots which if they went bad would drive you absolutely nuts if you squirted the tri-clo in them. Yes they would work for a while, but only for a while. We would substitute wire wound pots if possible and maybe 5 turn and 10 turn pots which would expand the "sweet area" where it would constantly end up position wise depending on the circuit. Then instead of setting the level to -10db it would be -10.0 db. You gain a ton of calibration adjustment at that specific point---it doesn't make the circuit more accurate but the result seems like it is---. Wheras before the -10db would fluctuate from -10.7 to -9.8 because of bad carbon surface with the 5 or 10 turn pot you could nail it at 10.0 with great ease and peace of mind.

JJK

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I didn't doubt you, just a tough solution with vintage equipment.

Can you reccomend any "sleeper" pots that are relatively inexpensive and good grade for audio equipment?

thanks,

Chris

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That's a tough one. If I used a carbon pot I would put a multimeter on it and slowly move it through from one end to the other noting if there were any jerks or jumps. The Allen-Bradley carbon pots seemed to be consistantly good but that was back in the old days. I haven't a clue today. Wirewound pots (if the circuit is not designed for carbon pots) really worked well for us in a variety of equipments, and they are expensive. For the life of me I cannot remember any circuits where they did not work. We used them in Parametric amp monitoring circuits and baseband oscillator output circuits to set very precise levels for testing. Our Western Electric VTVM measured from 12khz to 4 meghz +-0.2db from +10 to -110db and this was tubes. The 60khz phase lock frequency generated in New York measured 60,000.000hz with the HP solid state freq meter which was a calibration standard. The VTVM was calibrated with a special floor mounted oscillator using a 75 ohm thermocouple set which was accurate to the same frequency spec as the VTVM except the db spec was .o1db instead of .1 db. (37B VTVM and 53A oscillator)Just to give youo an idea of what was in the field in those old days the 53A oscillator had a custom made 35mm filmstrip with the exact frequency settings of the oscillator itself and you could not change those strips as they would not match another oscillator unit. Thats where all your phone bill money went, to create masterpieces of test equipment that people today cannot even concieve of. All of the special mux filters they used would have a -70 db down spec at the 3 db points. I could go on and on but somehow got off subject.

JJK

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I have an HK 630 (old Dual Power supply unit) that is occasionally malking noise. Fiddling with the bass or volume control seems to make the noise go away.

I would like to clean the inside of the unit, and clean and lubricate the switches. I have never done this before. What products do I use, where do I get them and how do I do it?

I use Caig deoxit on the pots and switches of all my vintage stereo equipment works great.You can get it at parts express.

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On 3/1/2005 3:12:50 PM RichardP wrote:

Yes, I would like to know also, for both paddle-type switches as well as rotary knobs, like the volume control.

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I remember being a young-un, and my Pa used to paddle my knobs with switches before his Rotary meetings. Even so, he could not control my volume.

Thanks, I had almost forgotten this.

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On 3/3/2005 11:48:04 PM 3dzapper wrote:

It didn't help a bit.

I second Dr Bill's motion, Rat Shack Contact Cleaner, not the paper bag though I hadn't thought of that before.
5.gif14.gif

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What didn't help a bit?

Also, does anyone know how many watts the 630 is rated at?

Chris

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