Seeking advice on potential concerns with recently purchased (eBay), partially recapped Kenwood KA-8150 integrated amplifier

[Sila881]

Hello, I would sincerely appreciate some feedback from experienced technicians/hobbyists. I’m pretty new to servicing and recapping vintage equipment that I own. I recently purchased a Kenwood KA-8150 integrated amp from eBay (first time buying electronics through eBay)- fully recapped with the exception of the main power supply capacitors (tested and still hold rated capacity per eBay seller/tech hobbyist).

I have some potential concern after opening the metal cabinet up for a visual inspection. I am seeing some apparent poor solder work, with some areas of missing solder (@ C-17 capacitor) on the front panel- including old flux/possible corrosion at the Tape/Gain functions (seller indicates this area is solder flux residue from the factory). Please see attached photos. After sharing photos with the seller, he said there should be no problems/issues, and admits sometimes things are missed. Comparing my recently fully recapped amp and receiver, however, the solder work in both units was very thorough and interiors free of any such residue.

As for sound, with initial testing, the Bass knob was very scratchy- but only on the right speaker- and the Gain switch was very scratchy. Both have improved with use (seller indicates all switches and pots were cleaned with DeOxit). Any idea what could cause just the right speaker to be scratchy when turning the Bass knob (tested with volume balance knob)?

I was offered a $75 refund towards the issues I shared, for any servicing on my end by the seller. I realize this will only cover some servicing work.

The Kenwood tested well with other functions and is in excellent cosmetic condition otherwise- the overall cost was reasonable- would the above issues (particularly the soldering concerns and flux debris) be concerning enough to bring in for further testing/servicing? I lack the knowledge and looking for second opinion from the seller. I can open it back up and try to access the interior of the front panel to hit the bass knob and gain switch with De-Oxit myself.

I value the work that all you technicians/hobbyist techs do for us to continue to enjoy these lovely vintage units. I am willing to work with the seller, as he seems sincere and more of a hobbyist. He also received flawless reviews from all previous sales. Ultimately, seeking input on whether this Kenwood amp should be serviced soon. Thank you very much for your time and having a look at my post.

 

[rickl]

I'd try to clean the pots again. And then use some f5 like lubricant.

You can heat up a nozzle with a heat gun or similar to bend it to fit the pot opening.

 

[Sila881]

I'd try to clean the pots again. And then use some f5 like lubricant.

You can heat up a nozzle with a heat gun or similar to bend it to fit the pot opening.

Thank you very much- I'll give that a try.

 

[painttoad]

Any idea what could cause just the right speaker to be scratchy when turning the Bass knob

yes. most likely a spray and pray was performed.

my guess is that the potentiometers were not removed for cleaning.

many vintage tone pots are dual gang and the rear gang has a notch (red) that prevents the knob from turning continuously. flippers see that hole and spray cleaner in it but that only gets cleaner on the rear gang and that leaves the front gang dry and scratchy.

if you are lucky to have a pot like pictured that has a hole on the front section(blue) then you can spray your cleaner in that hole also.

imo, at the very least, cleaner needs sprayed in bottom(green) and that generally means much more disassembly to get access and usually involves removing the pots which is a LOT more work than flippers will do.

 

[curtisw99]

Hello, I would sincerely appreciate some feedback from experienced technicians/hobbyists. I’m pretty new to servicing and recapping vintage equipment that I own. I recently purchased a Kenwood KA-8150 integrated amp from eBay (first time buying electronics through eBay)- fully recapped with the exception of the main power supply capacitors (tested and still hold rated capacity per eBay seller/tech hobbyist).

I have some potential concern after opening the metal cabinet up for a visual inspection. I am seeing some apparent poor solder work, with some areas of missing solder (@ C-17 capacitor) on the front panel- including old flux/possible corrosion at the Tape/Gain functions (seller indicates this area is solder flux residue from the factory). Please see attached photos. After sharing photos with the seller, he said there should be no problems/issues, and admits sometimes things are missed. Comparing my recently fully recapped amp and receiver, however, the solder work in both units was very thorough and interiors free of any such residue.

As for sound, with initial testing, the Bass knob was very scratchy- but only on the right speaker- and the Gain switch was very scratchy. Both have improved with use (seller indicates all switches and pots were cleaned with DeOxit). Any idea what could cause just the right speaker to be scratchy when turning the Bass knob (tested with volume balance knob)?

I was offered a $75 refund towards the issues I shared, for any servicing on my end by the seller. I realize this will only cover some servicing work.

The Kenwood tested well with other functions and is in excellent cosmetic condition otherwise- the overall cost was reasonable- would the above issues (particularly the soldering concerns and flux debris) be concerning enough to bring in for further testing/servicing? I lack the knowledge and looking for second opinion from the seller. I can open it back up and try to access the interior of the front panel to hit the bass knob and gain switch with De-Oxit myself.

I value the work that all you technicians/hobbyist techs do for us to continue to enjoy these lovely vintage units. I am willing to work with the seller, as he seems sincere and more of a hobbyist. He also received flawless reviews from all previous sales. Ultimately, seeking input on whether this Kenwood amp should be serviced soon. Thank you very much for your time and having a look at my post.

The stuff on the solder joints looks like old flux.
If it bugs you, a qtip with alcohol will clean it off

 

[painttoad]

i took a better look today and the pot is different on that unit than what i posted.

i think it is this style



but same theory as before. note the right side, it only has an opening to spray into half the unit. if your typical very light spray of deoxit was sprayed into that opening, it would not reach the rear wafer. if it was lightly sprayed into one of the 2 openings one the left side, it would not reach the other wafer.

not your most accessible pots out there. this will give you an idea of what's involved. $75 might only be enuff to inspect the unit. a brick & mortar shop may want double or triple that to dig into that unit enough to properly clean those pots.

 

[WSideWitness]

The pics you posted don't look terrible on quick inspection. The residue in the last 2 pics look to be from original soldering work. A thorough restoration involves reflowing all these points, but I wouldn't expect many ebay flippers to do that.

 

[Sila881]

i took a better look today and the pot is different on that unit than what i posted.

i think it is this style

View attachment 3842266

but same theory as before. note the right side, it only has an opening to spray into half the unit. if your typical very light spray of deoxit was sprayed into that opening, it would not reach the rear wafer. if it was lightly sprayed into one of the 2 openings one the left side, it would not reach the other wafer.

not your most accessible pots out there. this will give you an idea of what's involved. $75 might only be enuff to inspect the unit. a brick & mortar shop may want double or triple that to dig into that unit enough to properly clean those pots.

Thank you so very much for the education, your time, the photos and the video attachment- you have been very helpful!! I read your first comment as well. I found that 3 part Kenwood restoration on youtube and saved all three to view and study. I'll open it back up- but being that inaccessible and my lack of experience, I'm sure I'll be maing some calls for servicing.

 

[Sila881]

yes. most likely a spray and pray was performed.

my guess is that the potentiometers were not removed for cleaning.

many vintage tone pots are dual gang and the rear gang has a notch (red) that prevents the knob from turning continuously. flippers see that hole and spray cleaner in it but that only gets cleaner on the rear gang and that leaves the front gang dry and scratchy.

if you are lucky to have a pot like pictured that has a hole on the front section(blue) then you can spray your cleaner in that hole also.

imo, at the very least, cleaner needs sprayed in bottom(green) and that generally means much more disassembly to get access and usually involves removing the pots which is a LOT more work than flippers will do.

View attachment 3841963

Thank you so much for your detailed response!!

 

[Sila881]

The stuff on the solder joints looks like old flux.
If it bugs you, a qtip with alcohol will clean it off

Gotcha- thank you very much- I'll take care of that.

 

[Sila881]

The pics you posted don't look terrible on quick inspection. The residue in the last 2 pics look to be from original soldering work. A thorough restoration involves reflowing all these points, but I wouldn't expect many ebay flippers to do that.

I really appreciate your response- thank you so much!