(Vintage) Receiver imbalance issues driving me insane!

So I've been using a 70s Kenwood KR-3600 for about a year now, and for the most part it's served me well while I live in small college apartments with its 22wpc. About a month ago, I thought it sounded like the right channel was quieter than the left, sometimes it sounded like there was barely any audio coming from it, so I decided to take it out from the shelf and clean it, deoxit the pots and get all the dust out of it. I didn't notice any improvement after cleaning both the balance and volume pots for a few minutes each. I then used a pair of speaker cables to 3.5 audio connector to connect it to the line in on my iMac. I switched the receiver to mono mode and recorded a short bit of FM audio, and a bit of music from the aux input off my iPhone. My suspicions seemed to be true. In Audacity, the VU meter was showing the right channel to be maybe 15% lower than the left. While I was still recording, I turned the balance knob on the receiver to the right, and was able to get the levels virtually the same, albeit with the knob turned almost half way to the right! Thinking it would be less money in the long run to just get another receiver instead of repairing this low end one, I started looking for something else. I've gotten some really great offers from some fellow members and a couple good deals have popped up locally. However, before spending a few hundred dollars on something else (not exactly in the budget for a college student) I want to make sure I'm not going crazy here. Yesterday, I decided to try the receiver again after it sat unused for a few weeks. Low and behold, it sounded to my ears to be balanced. Unfortunately due to some hardware problems my mac is not currently usable to use the same method as before to test the channel balance. Instead, this time I used a decibel measurement app on my iPhone. I held the phone microphone to the exact spot on both speakers, playing a 440hz test tone from my laptop intot he aux input on the receiver. It measured the same decibel level on both speakers at multiple volumes, with the balance pot turned just a few degrees off center. Now, I'm not any kind of expert on these kinds of things, but could it be that there's some kind of imbalance in my speaker wires, enough that I'd notice it? In other words, how can I be sure it's the receiver and not something else? Like I said I'm no expert on the hardware side of things, but I do have a multimeter, not sure if I could get an accurate test of the outputs from the receiver from that? If so, how would I go about it?

Sorry for the longwinded post, just don't want to spend the money on something I don't in fact need.

 

I'd clean all other switches and pots as well if I were you. Input selector could easily be the culprit, and it will change it's performance everytime you move it. More cleaning, and sometimes you have to do them multiple times to get them clean and functioning properly.

 

Hadn’t even touched the input selector, I’ll see if that helps, thank you.

 

Loudness, etc too. It's all in the circuit one way or another!

 

Also, Kenwood balance pots are not well sealed. They tend to need cleaning a bit more often, and when really dirty, may need to be cleaned another time, also exercise them often, and after cleaning rotate them 20 times.

 

I'll try another cleaning, thanks for the suggestions. After that, is there any way to test balance past my ears? It's not that I care if I tinker with the eq for it to sound better, its that I want to be sure if it's out of wack or not.

 

So true; if it has knob or a switch on the frontal panel, it's in the signal path. My tone defeat switch is always on and the other day I had to spray it with Contact Cleaner because I kept loosing the right channel !

 

Not to get off topic from what I originally asked about, but how common is it to have vintage gear like this fail as far as caps/transistors? Is it pretty common, or more likely to just be dirty/finicky controls? I've had a few pieces of vintage gear and all have had problems at some point, but I've always had lower end stuff, nothing too fancy so I'm assuming lower end components as well which would be more failure prone. Perhaps I've just been unlucky

 

My opinion? Take it into a professional technician to have it serviced.

I’ve been through the same exact struggle with vintage gear finding it to be somewhat usable in current state, until problems start arising. The primary problems are in a vintage piece like this ate radical tonal shifts and channeling imbalance as well as extreme issues like crackling and popping etc.

You ask how common this issue is and I would say it’s extremely common. IMO, anyone that denies how common it is is just unaware of how far their vintage gear has drifted out of spec.

While vintage gear may sound “good” in a subjective sense without any restoration, the reality is you have to get these things repaired / recapped every ~30 years, so yours is certainly due. While you can treat some issues by deoxidizing and cleaning it yourself, that’s like taking a cough drop instead of antibiotics when you have strep throat.

I resisted this logic forever myself and figured that spending amy money on restoration of a vintage piece would defeat the inherent value proposition of buying used. I really wish I had woken up to this sooner, as I’m much happier now going through a tech for all vintage gear.

 

Sounds like my gut was right then. Deal with the issues in the meantime but since I'm dead set on using vintage gear, find something that I really like and have it serviced once and just take the financial bite.

 

Well yes; pretty common for caps having to be replaced. However, I own 2 vintage amps (see profile) and save for bias adjustment on one of them ONCE, nothing ever drifted from spec (and yes, they've been checked by techs on occasion of minor issues that needed repair, and despite my asking whether they needed to be recapped or not, they told me no need for it)) Luck has played a a part, but it's the stuff that has been stored for long periods of time that usually has the more issues, as opposed to stuff that's been in constant use.

 

So wait. You hooked speaker level amplifier output to the line input on your computer? No one else finds this troublesome? Also need to be careful with the pot cleaner. Some pots need the lube that gets washed out.

 

I did just that, this is how I've ripped vinyl to this computer several times before with no issue.

 

Anything can fail in a 45 year old piece of gear. Or it might keep working. But in truth, every electrolytic cap in a piece like that is probably beyond its reasonable-to-expect life. It wouldn't be surprising if other caps and resistors are out of spec. Depending on how the piece was used and how the piece was maintained and the conditions it has lived its life in, all the pots and contacts and switches are could range from marginally dirty to so dirty they cause signal to be intermittent. And any 45 year old active device like a tube or a transistor might die (tubes, like light bulbs, certainly will die with normal use, eventually). A 45 year old receiver that hasn't been tested and restored and maintained is probably operating out of spec. It's like a 50 year old car or something. If it's operating with all original parts, well, any number of those could go.

 

Yes, and the cost will be less than you think, a few hundred for a piece like that that’s easy to repair. Probably as much as it would cost to find a clean OG pressing off that record in your avatar! If I were you, I’d look into reputable repair shops in your area. You may even find one that’s willing to take the Kenwood and spot towards something else restored and ready to go that would have a better sound and more power if desired.

@chervokas is spot on with the car analogy, but I would add that you might be able to imagine the car had never had an oil change in all those years as well.

I was in college just a few years ago so I get that cash is tight, but as soon as I got a restored receiver after I graduated I wished I had just spent some of the money I put towards records on it years before. Especially since we have many years ahead of us in audio no use wasting time with a faulty piece.

 

Sure if you have a piece of vintage gear you plan to keep I'd sure as heck do a complete refurb with a qualified technician. Good luck finding one who will do exactly what you want!

Cleaning the pots is exactly what they will do as part of this, and the most likely cause of your imbalance issue.

I always use cleaner with lube in it on the last spray when I clean pots.

 

Could just be matching error of the volume pot. I recently replaced the conductive plastic pot in my pre with a true stepped pot with much higher accuracy for channel matching. Weaker left channel problem solved. Stepped pots are a massive upgrade it sound anyway..... totally worth the $$$.