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Kenwood Basic C1 Preamplifier Restoration/Upgrade

I have taken transformers apart to expose the winding and repaired them before using care and a soldering iron. If it really is bad why not try ?
 
i'd just throw in a transformer that fits with a couple of secondaries that are close to a C1 secondary voltages. I think the issue might be the C1 height. My C2 is not very high and (i think) a C1 is similar.

I like vstat88's suggestion to pull the bells off and see if you can find the problem.
 
Thanks! I luckily found someone to make me a new transformer out of two secondaries for a fair price like you said, so waiting on that.

Just curious- Is it possible to solder the copper wire back together in a transformer in place if easily visible on the outside? Or does it require unwinding it to that point.

When the copper is wound that tight does it make electronic connection to itself? Or is there a coating on the copper that prevents that. Meaning does electricity flow only through the small strand of copper wire or is the whole winding making a connection with itself?
 
i'm not a transformer guy but a transformer will have magnet (mag) wire wrapped around a iron core. this wire will have clear insulation. if you can find the broken wire, you can just resolder it back together (i'd probably cover with heatshrink). however it can be difficult to wind tight enough as the original. I haven't done this so this maybe wrong.

I'm glad to hear you can get a new transformer made. Once you get it working in your pre, you might want to post your supplier for others.
 
simpsonsons said:
Thanks! I luckily found someone to make me a new transformer out of two secondaries for a fair price like you said, so waiting on that.

Just curious- Is it possible to solder the copper wire back together in a transformer in place if easily visible on the outside? Or does it require unwinding it to that point.

When the copper is wound that tight does it make electronic connection to itself? Or is there a coating on the copper that prevents that. Meaning does electricity flow only through the small strand of copper wire or is the whole winding making a connection with itself?
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Go with the one that you are having made. No disrespect intended but if you are asking the ^ then it may be difficult for you to accomplish. Remember, NO disrespect intended. Let us know how it turns out and if you want me to look at fixing your stock one (no charge) then PM me. The only way I would attempt a repair is if the wire is broken somewhere and I did NOT have to try and unwind the whole thing.....
 
Hello mbz,

Before changing from LM4562 to OPA2134 in the tone circuit did you try the NJM2068DD opamp as recommended by Leestereo?

I'd be open to trying OPA2134, but would like to know what your thoughts were about the opamp I'm currently using NJM2068DD?

Thanks
 
I am using the NJM2068** in my C2 and it is just fine. I tried a few different ones but to me the stock one sounds good.
 
C1bob said:
Hello mbz,

Before changing from LM4562 to OPA2134 in the tone circuit did you try the NJM2068DD
Click to expand...
I only tried what I had at hand/in stock. If you have a socket in place and some spare time then certainly try a few.
On paper, the NJM2068 looks like a good sub for NJM2043, very low noise being the key attribute. Supply current
is about the same but voltage is back from 22V to 18V so you would need to updates to the psu (=16V? zeners)
 
If the C1 has black foam blocks for supporting wires on the board, I'd suggest replacing it with some new foam. My C2 has a foam block and it is crumbling. I really don't want any of the foam bits to get in the controls.

I'm using NJM2068DD with 16v zeners in my C2.
 
I agree about the op amp standoffs. That was one of the coolest things about restore to me. Now I can try different ones. As far as those little foam blocks I have never had one crumble but that is an excellent idea. I will be doing that on mine as well. Only makes sense to do so now. Thank you.
 
Hello mbz, vsat88 & rickl,

Thanks for your replies.

I'm basically happy with the NJM2068DD opamp and will stick with it, but had mbz actually of compared it to OPA2134 I might have been tempted to try.
 
C1bob said:
I'm basically happy with the NJM2068DD opamp and will stick with it, but had mbz actually of compared it to OPA2134 I might have been tempted to try.
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I will include 5xNJM2068DD on my next mouser order, at $1- each... The advantage with the NJM...DD is the lower noise.
Would also expect better "compatability" since originals were NJM... Probably provide an update in 3 months...
 
mbz said:
I will include 5xNJM2068DD on my next mouser order, at $1- each... The advantage with the NJM...DD is the lower noise.
Would also expect better "compatability" since originals were NJM... Probably provide an update in 3 months...
Click to expand...
Parts from mouser arrived including NJM2068DD. I like what the 2068DD's brings to the amp, it's a slightly different
sound compared to the OPA2134 which I also like. I don't see this as one opamp being "better" than the other more so
what sound you are after and how well it intergrates into the rest of your system. I found the 2068DD more "neutral"
something you would expect in higher priced items, now I need to decide what sound I want, both are good results.
 
Hi guys just completed the restore of my C2. I purchased a C1 should be here in a few days then I will restore it following instructions in this thread ( I can't wait) so anyways the difference in the C2 before and after I noticed the bass response tightened up real nice I'm not the only one who noticed this after reading quite a few threads here that seems to be what people notice right off I could not have done this without the help of AK so Thank You all of you
 
David, I looked it over and I think you have made an exceptional list here. I do not see anything by a quick scan that should be changed. Pretty awesome the way it is linked back to Mouser when the part number is clicked on. Great work ! Now a list for the C2 ?
 
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