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Would it be worth fixing old Kenwood KA-7010?


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Hope get some information on if it would be worth getting old amp repaired or just get new one? We had old Kenwood KA-7010 amp, that dad purchased new but was in HiFi shelf not used for more than 20 years.  Now with the speaker purchase tried to use the amp but it doesn't seem to be in fully working order.

 

It can play both channel without issue when using "Source Direct" button is on, but when it is off, only right channel has normal level of audio.  Left channel has real faint sound even at full volume.  It sound still very good in "Source Direct" mode but just wanted to see if it would worth fixing it.

 

As this amp will not fetch too much even if it is fully working condition, wasn't sure how much would it cost to have it repaired.. may be cheaper to get new amp?

 

Attaching photo in case something someone can see something obvious... it look

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Edited by xtiva2000
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  • xtiva2000 changed the title to Would it be worth fixing old Kenwood KA-7010?

Worth fixing.

 

The issue with source direct disengaged is obviously on the tone controls circuitry, might even just be dirty pots.

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Get local quotes but repairs can often be around $150-250+ depending what’s wrong with it. They won’t know until seeing it but check any simple items like fuses, burn or smell marks around capacitors and replace like for like, as Muon says spray cleaner around control knobs and clean.

 

Its quite a solid built but not well reviewed old amp see here https://audio-heritage.jp/TRIO-KENWOOD/amp/ka-7010.html

 

 

Edited by Al.M
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Oh Thanks for the quick reply... will try to open the front and try Muon's suggestion first...

Wasn't able to find obvious marks or smell but will try to look again..

 

Thanks.

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When repairing your Kenwood a schematic diagram will show exactly how the parts are arranged. A schematic is available here:

https://www.hifiengine.com/manual_library/kenwood/ka-7010.shtml

 

You should find on page 9 how the source direct is wired and the principal cause of your difficulty is the balance control which is dual gang 200k potentiometer. 

 

A little history first  shows audio signals were never designed to be arranged to traverse through potentiometers,  Mary Hallock Greenewalt holds the patent for the rheostat and she was well aware of the potentiometer form in her 1919 patent. Mary designed the rheostat to be used for a visual music form she called Nourathar  and never was her invention intended for audio signals. 

https://www.diyaudio.com/forums/analog-line-level/359931-100-wrong-purpose.html

 

If you do not need the balance control which might be best  you could wire it out using resistors using 4x 100k 1/4 watt types - all of about 10 cents or less. You would copy the exact same schematic form instead making the take off wire for the wiper ( the middle wire ) the divider between the two 100k resistors for each channel. that you have you have substituted the balance control for.   

 

Hope that helps.

 

 

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10 hours ago, stereo coffee said:

When repairing your Kenwood a schematic diagram will show exactly how the parts are arranged. A schematic is available here:

https://www.hifiengine.com/manual_library/kenwood/ka-7010.shtml

 

You should find on page 9 how the source direct is wired and the principal cause of your difficulty is the balance control which is dual gang 200k potentiometer. 

 

A little history first  shows audio signals were never designed to be arranged to traverse through potentiometers,  Mary Hallock Greenewalt holds the patent for the rheostat and she was well aware of the potentiometer form in her 1919 patent. Mary designed the rheostat to be used for a visual music form she called Nourathar  and never was her invention intended for audio signals. 

https://www.diyaudio.com/forums/analog-line-level/359931-100-wrong-purpose.html

 

If you do not need the balance control which might be best  you could wire it out using resistors using 4x 100k 1/4 watt types - all of about 10 cents or less. You would copy the exact same schematic form instead making the take off wire for the wiper ( the middle wire ) the divider between the two 100k resistors for each channel. that you have you have substituted the balance control for.   

 

Hope that helps.

 

 

Wow thanks for detailed information... sounds like too much for non-techie person for me ... have opened and gave front panel a cleaning.. but still only one channel in non source direct mode... might take it to repair shop..

 

But would you know how much this amp is worth in fully working order?  I still have original manual and box...

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A quick partial fix that should work for a while  is to turn the unit off  by disconnecting the AC cord from the wall socket , obtain some contact cleaner from Jaycar  and nozzle spray the balance volume and every other potentiometer  gaining access to their internal parts from inside , each are attached to the front panel, so will be just a matter of lining each up leaning into the inside front panel, then cleaning the tracks of each - give it about 30 mins before turning on again. 

 

Shown here cleaning a guitar amp, the video provider manages to find spider nests and disassembles the complete circuit board, but the principle is exactly the same with your Kenwood, less removing the circuit board. 

 

 

 

As regards retail sale.  the buyer will greatly appreciate a nice working amplifier, the Kenwood has good specification its rated distortion

is low, so its beauty and performance, will or should reflect a reasonable return for you at that time. 

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39 minutes ago, stereo coffee said:

A quick partial fix that should work for a while  is to turn the unit off  by disconnecting the AC cord from the wall socket , obtain some contact cleaner from Jaycar  and nozzle spray the balance volume and every other potentiometer  gaining access to their internal parts from inside , each are attached to the front panel, so will be just a matter of lining each up leaning into the inside front panel, then cleaning the tracks of each - give it about 30 mins before turning on again. 

 

Shown here cleaning a guitar amp, the video provider manages to find spider nests and disassembles the complete circuit board, but the principle is exactly the same with your Kenwood, less removing the circuit board. 

 

 

 

As regards retail sale.  the buyer will greatly appreciate a nice working amplifier, the Kenwood has good specification its rated distortion

is low, so its beauty and performance, will or should reflect a reasonable return for you at that time. 

Thanks once again for your detailed information.  Will go get dexit today and try your suggestion.

 

Thanks

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15 hours ago, xtiva2000 said:

Hope get some information on if it would be worth getting old amp repaired or just get new one?

 

Beautiful, dual-mono, integrated amp from the late 80's. While these were well designed, there were issues with dust/rust due to the front panel knobs and buttons not being well sealed. From another forum, there was this:

There are a couple of trouble spots in this amplifier

1. the Speaker relay in the back of the amplifier (near the speaker outputs...go figure) can oxidize and cause intermittent operation
2. the front panel buttons and switches aren't sealed, and are a natural for oxidation

 

On the plus side, 100w/Ch of fairly clean power, reasonable quality Phono pre-amp (MM & MC) and a good subsonic filter (6dB/oct at 18Hz).

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Sorry guys but amp plays ok when source direct is on, this means everything
downstream of the source direct switch is ok, this includes speaker relay and balance pot. Problem is in the tone amp, bass, trebble switches...

 

With tone direct off, work through each of the tone switches and not any significant change in audio, either good or bad, that switch may need further cleaning. The tone amp is based around NJM4560.

 

It should be a simple task to diagnose the problem with an oscilloscope, maybe $75- if you took it to a tech.

 

image.png.c00c88263d357b9321657073d38583f9.png

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Yep, spoke too quickly. The block diagram has balance after the tone direct switch however the schematic show it before, so it is "in play". More interest to me is the subsonic switch, exercise it a few times and note any change.

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On 18/01/2021 at 12:33 PM, Cloth Ears said:

Beautiful, dual-mono, integrated amp from the late 80's. While these were well designed, there were issues with dust/rust due to the front panel knobs and buttons not being well sealed. From another forum, there was this:

There are a couple of trouble spots in this amplifier

1. the Speaker relay in the back of the amplifier (near the speaker outputs...go figure) can oxidize and cause intermittent operation
2. the front panel buttons and switches aren't sealed, and are a natural for oxidation

 

On the plus side, 100w/Ch of fairly clean power, reasonable quality Phono pre-amp (MM & MC) and a good subsonic filter (6dB/oct at 18Hz).

 

 

On 18/01/2021 at 3:14 PM, mbz said:

Yep, spoke too quickly. The block diagram has balance after the tone direct switch however the schematic show it before, so it is "in play". More interest to me is the subsonic switch, exercise it a few times and note any change.

 

Thanks so much for the information!!!

 

didn't have time until today to get the DeoxIT from Jaycar and to clean all of the knobs.

 

When opening the case and looking at the those pods, it looked clean to my eyes so was skeptical but DeoxIT seems to have done the trick.  

 

All is working great now no little static I was getting from volume pod is no longer there either.

 

Thanks guys 

 

 

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