Kenwood Basic c2 balance adjustment pot
- Thread starter purenrg
- Start date
thanks matteos for this post. I am about to pick up a C2 with a channel out problem so I am guessing I will be getting in to this and trying to fix or bypass this and get it working. This one will be coupled with a Kenwood KM-209 amp pushing some cerwin Vega VS-150 speakers.
This post really helped me out and gave me a way out if I cant fix that pot. This will be my first electronic project other then re doing my rca cable and ground on my TT. So let the headache begin!
This post really helped me out and gave me a way out if I cant fix that pot. This will be my first electronic project other then re doing my rca cable and ground on my TT. So let the headache begin!
janikphoto
Lunatic Member
It's not the worst piece to work on. I just took mine apart a couple hours ago to fix what I'm guessing was cold solder joints on the rca outputs. I'm testing it now and it seems better.
hey guys I just picked up a c2 wit this same issue well I had it working the resistor way then decided to remove the switch and just jump it. Well know its will not work and I am actually thinking I messed up the circuit board when I de sodered a piece of the green line came off and now no matter what I do the unit is dead. Mad at myself for tinkering with it after I acutally had it going right. So here comes the question to you guys.
1. how can i tell if i messed up the board and are those green lines the circuit?
2. If the answer is yes and I messed it up is there another place to by pass this?
I dont care about the balance I just want it to work.
Thanks for any help. I am going to take it to a shop next week if you guys are stumped I am hoping you experienced guys can help me out.
Thanks in advance for any help at all. I am really excited to have this C2 but now I need to fix it or I guess break down and get it to an electronics repair place which will not be nearly as cool as doing it myself. I am a total noob to electronics and all that so just a heads up on that!
Thanks guys
1. how can i tell if i messed up the board and are those green lines the circuit?
2. If the answer is yes and I messed it up is there another place to by pass this?
I dont care about the balance I just want it to work.
Thanks for any help. I am going to take it to a shop next week if you guys are stumped I am hoping you experienced guys can help me out.
Thanks in advance for any help at all. I am really excited to have this C2 but now I need to fix it or I guess break down and get it to an electronics repair place which will not be nearly as cool as doing it myself. I am a total noob to electronics and all that so just a heads up on that!
Thanks guys
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well just to keep you updated i got the c2 working. I did mess up the circuit board a bit and had to bypass the balancer pot farther up. Worked like a charm just using some solder. So even if you mess up the board a bit around where the pot was its salvageable. Going to let her play for a while and enjoy.
janikphoto
Lunatic Member
Be sure go resolder the joints at the RCA's, if you have sound cutting in and out issues, like mine did. After I did the balance mod, I started having issues, which I tracked to cold solder joints back there.
well its doing something odd it works fine and all of the sudden the right channel goes fuzzy and then its dead. Is that what you were experiencing or was your different. I tried switching in between sources and it stayed consistently down thru it all then it just came back miraculously. After a few hours it went down again now its back. Any ideas? I thought maybe id didn't solder that channel with enough solder maybe and when it heats up its not enough of a bridge?
Will definitely check the RCA solder joints thanks for the heads up on that. I think what I am describing is different from what you had going on correct? Mine isn't cutting in and out and its all isolated to the right channel?
Will definitely check the RCA solder joints thanks for the heads up on that. I think what I am describing is different from what you had going on correct? Mine isn't cutting in and out and its all isolated to the right channel?
I just did all this to my C2 and despite removing the pot and adding the resistors ( I used 220K; does it really matter here??), it still was erratic. Suspecting bad solder joints, I began to handle the small board loose on the ribbon cables, as it worked well yesterday just jumpered loose, but once I buttoned it up it was erratic again.
After getting erratic outputs moving the board, I began to suspect the 6 wire ribbon. Pegging it on the volume pot case, I got erratic sound moving the side on the Volume pot, but no effect on the balance pot side. I decided to reflow the Volume pot side connections so after some finagleing I was able to flip the PC board and reflow the 6 joints, all which looked fine. I partially reassembled it and now she works fine.
Hopefully, this is it. I will save the removed pot as now I'm uncertain if is bad, but I have no intention of disassembling it as the PC board connections we tiny enough to challenge my skills.
BTW, I am loving this preamp and all but certain it will displace the tube pre that replaced a previous C2 years ago....
After getting erratic outputs moving the board, I began to suspect the 6 wire ribbon. Pegging it on the volume pot case, I got erratic sound moving the side on the Volume pot, but no effect on the balance pot side. I decided to reflow the Volume pot side connections so after some finagleing I was able to flip the PC board and reflow the 6 joints, all which looked fine. I partially reassembled it and now she works fine.
Hopefully, this is it. I will save the removed pot as now I'm uncertain if is bad, but I have no intention of disassembling it as the PC board connections we tiny enough to challenge my skills.
BTW, I am loving this preamp and all but certain it will displace the tube pre that replaced a previous C2 years ago....
BTSs
Active Member
My thanks to all for this thread.
I picked up a C2 pre last week with some other Kenwood bits.
5 minutes into testing the C2 things were going well then the balance pot give up completely on the right channel. With the knowledge gained here I had ago at repairing it.
As you can see some bush mechanics was required to keep it together. Only one rivet was re-usable and I only had a paper clip handy to tie the other side together.
Five days latter its still going strong.
Thanks all.
Tony
I picked up a C2 pre last week with some other Kenwood bits.
5 minutes into testing the C2 things were going well then the balance pot give up completely on the right channel. With the knowledge gained here I had ago at repairing it.
As you can see some bush mechanics was required to keep it together. Only one rivet was re-usable and I only had a paper clip handy to tie the other side together.
Five days latter its still going strong.
Thanks all.
Tony
Just to keep this thread "alive". As far as C1 and C2 I think them great little Pre amps. Both have good quality's. I have two C1s and one C2. Once a lightng storm came and blew a lot of equipment in the shop I was using to listen in. The Basic M2 did not make it (The Kenwood amp connected to one of the C1s) The C1 did ! Pretty strong ! I did have a problem once with that same C1. After I moved it it started having some weird problem. I really can not recall what it was of the top of my head..seems like it was humming or weak output, just can not recall. I went to checking it out..Cover off meter in hand..Finally after a while I realized that the 120VAC/220VAC switch had inadvertently been switched to 220VDC when I moved it. I live on 120VDC hence problem solved. Now on to the C2. I have found that if the Source OR the Input selector have dust, trash whatever in them (and most would after 25 years give or take) then a channel will give trouble. This is a link where you will find an excellent tutorial..Oh and BTW, This is the right way to go no matter how it may seem. Worked at a company years ago that sold/repaired very expensive electronics and this was standard procedure for every rebuild..
http://www.audiokarma.org/forums/showthread.php?t=258899
http://www.audiokarma.org/forums/showthread.php?t=258899
janikphoto
Lunatic Member
I'm pretty sure you mean 120vac, and not DC. You'll be hard pressed to plug in a piece of stereo equipment and expect it to work with the wrong current!
Thanks a bunch for this thread. I was thinking of purchasing one of these as I had heard many good things about the sound. However due to the price that is being asked and the large number of people with problem units I think I will keep my cash in my pocket. Now if they were asking 50.00 I might have to think about that.
Cheers! and good work with all of your fixes.
Cheers! and good work with all of your fixes.
ponitora
New Member
Back to the C2 balance pot problem, I replaced the original pot with an Alps LPS 704F 250K dual balance pot which is slightly larger than the original. But with a bit of jiggery pokery that pot can be made to fit in the location and imo is far better quality than the original. Not really a job for the novice repairer but if anyone cares to know the details just post a follow up here. The Alps LPS 704F 250K dual balance pot is available online and the closest quality replacement I could find after much study.
Most people just bypass that balance pot. I have a recapped C2 where the tech did just that. I have no problem with it because my power amp has separate gain pots for each channel.
ponitora
New Member
Sure the thread shows how to bypass the pot but not everyone wants to do that, and not everyone has a power amp that can be balanced. The original topic was about replacing the balance pot, with some concern that a suitable replacement pot cannot be found. The point of my post is that an Alps LPS 704F 250K dual balance pot can be made to work and is better quality than the original, for those with a modicum of skill who care to try it. For my part I like to keep my gear as original as possible, and do appreciate having a balance control. So, once again, if anyone is interested in the details of using an Alps LPS 704F 250K dual balance pot (easily available) please post a follow up, thank you.
If having to do modifications to use the new pot, it may be just as easy to rebuild the original. Here's my rebuild starting at post #14
http://audiokarma.org/forums/index.php?threads/basic-c2-restoration.730787/
http://audiokarma.org/forums/index.php?threads/basic-c2-restoration.730787/
ponitora
New Member
My balance potentiometer was physically damaged so could not be rebuilt. The Alps LPS 704F 250K dual balance pot is functionally identical to the original, but 6mm larger in diameter. It can still fit in the space of the original, and is by the way a better quality component. The LPS 704F solder tabs are larger and spaced wider apart, so the pot body must be rotated away from the board, then wires soldered to the board as shown in the photo. Since the replacement is functionally identical to the original the only difficulty is finding a neat wiring solution, I used the two ribbons shown in the photo. That's it pretty easy no secret about it.
