Meter Balancing == Kenny KA-5700

Spenser

AK Subscriber
Subscriber
Meters on Kenwood KA-5700 seem out of balance. That is to say. One seems to read consistently higher than the other.

Sevice manual procedure to balance meters had no effect. (Edit: upon reflection I think this sentence was incorrect. I don't think I actually performed the procedure before. Sorry.)

What do you think may be the problem here?

Thanks.
 
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Try a tuner with muting off, and in Mono, in between stations ( white noise), and see if the meters are still out of ballance.
 
Hey turboyam! Thanks for the reply. Good idea. Yes. The issue persists. Right meter is a hair higher than the left meter. You know like an eighth inch. I know. I'm out of my mind. How common is this type of disparity? If I were to put this amplifier up for sale would a buyer be put off?

So the dope that I am, I think several weeks ago before I buttoned her up I couldn't help myself and tried cranking one or the other or both of the meter VRs to see if I could get the two meters to match. Seemed to have no effect, as I recall.

I have no experience with power meters. I think my NAD 3080 might be off like this, too. I'll have to check.

Judging by the schematic there is a fair number of things in-play in these meter circuits.

Should I hook up a wave generator at 1kHz; turn up the volume some; and turn the left VR to see if it will match up with the right?

Should I deoxit and lube the VRs?

Replace the VRs?

What is a SSVM? Does that stand for Sinusoidal Volt Meter?

Were I to want to calibrate the meters to proper settings I'm not sure how to "use AG and volume control to obtain a setting of 40W (17.88V/8Ohm)."

Sorry for the 20 questions here.

Thanks again for the reply!
 
SSVM - probably solid state volt meter. DMM today

Never done it - but connect an 8ohm dummy load and your DMM to the speaker terminal. Feed the 1khz tone and turn up the volume until the meter reads 17.88V AC . If you were to do the math that equals 40W. http://www.bowdenshobbycircuits.info/ohmslaw.htm

Turn the trimmer so the meter reads 40W

If you don't have proper dummy loads you can't do it.

I just like watching the needles bounce.
 
Hey Al, Aha! SS=solid state (SSVM=solid state volt meter). Sounds right on. Thanks!

That's a nice calculator, for which you provided the link. Worth saving. Thank you.

So here's my report:

I put an Instek function generator into the auxiliarly input set to 1kHz sine wave; and an 8-Ohm dummy load on the A speaker outputs. Powered the amplifier up and established roughly 0.3W output (judging solely by the reading on right channel meter). Used a plastic tuning tool to turn the trimmer and bring the left channel meter needle up to match the right channel needle. Done. (Note: my objective in this power meter, tune-up was limted to getting the meters to read reasonably accurately, relative only to each other.) Thanks to all!





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@Spenser

If you have all the stuff and were inside anyway, why did you not calibrate the meters per the SM procedure?

Point being, if all you wanted was relative equal indication then neither the function generator not dummy loads were necessary to achieve that.
 
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Hey whoaru99. Thanks for asking. I was reluctant to take it further due to my inexperience; fear I might damage something; and suspicion that accuracy of the meters -- taken together with everything else -- was questionable and therefore unjustified / moot to take it beyond minimal risk getting the two meters to look like they were operating properly.

Do you think I should go back and calibrate the meters per the service manual?

Would installing Bourns replacement variable resistors (trimmers), be a responsible thing to do? I did not think about the meters when I did the overhaul.

Tagging on to matters here, looking at my file, I did not take good notes (feel shame), and cannot remember whether I checked bias and made a judgement on the optional variable resistor installment there.

Thanks again.
 
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No, not necessarily that you need to; it was just an observation.

About the other trimmers, I don't think I would for the meters as long as they worked well enough to make the adjustment.
 
Thank you. Could you advise me how I might have gone about getting the meters to align with each other without using the function generator and dummy load? Thanks
 
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