C-2X stays warm after shut off. Repair or OK or return?

samosui

samosui

Well-Known Member
I was happy with my recent purchase of a C-2X until I noticed that the unit stays warm even after turning off the unit. I have a Yamaha HT receiver that stays warm (RX-Z7) but I think that this is the case only when the "network standby" mode is enabled. Will check.

But I didn't think that a preamp from the 80's would stay in a standby mode. The unit turns on and works (with pilot light lit) and also turns off (no sound and pilot light out). I unplugged the unit overnight and it was cold in the morning (would have been an interesting situation if it stayed warm ;). Plugged it in in the morning without turning it "on" and it checked it in the afternoon. Yup, it's warm. What gives?

In the attached schematic, the "regular" model is the one that applies.

Edit: so does the US (or Japan) model have to be on for the phono preamp to be powered? But with the "regular" model the phono preamp is always powered (per the schematic)? If the latter is true that could explain the heat being generated by the preamp when the unit is off. But why would one want the phono preamp operational while the preamp itself is "off"? To route it to an external amp via the tape record "outs"? Why?

Cheers,
John
 

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samosui said:
I was happy with my recent purchase of a C-2X until I noticed that the unit stays warm even after turning off the unit. I have a Yamaha HT receiver that stays warm (RX-Z7) but I think that this is the case only when the "network standby" mode is enabled. Will check.

But I didn't think that a preamp from the 80's would stay in a standby mode. The unit turns on and works (with pilot light lit) and also turns off (no sound and pilot light out). I unplugged the unit overnight and it was cold in the morning (would have been an interesting situation if it stayed warm ;). Plugged it in in the morning without turning it "on" and it checked it in the afternoon. Yup, it's warm. What gives?

In the attached schematic, the "regular" model is the one that applies.

Edit: so does the US (or Japan) model have to be on for the phono preamp to be powered? But with the "regular" model the phono preamp is always powered (per the schematic)? If the latter is true that could explain the heat being generated by the preamp when the unit is off. But why would one want the phono preamp operational while the preamp itself is "off"? To route it to an external amp via the tape record "outs"? Why?

Cheers,
John
Click to expand...

Check and see if your switched and unswitched covenience plugs are tied together for some reason or another. Pop the cover and see if someone has been in there and gotten something miswired.
 
stoutblock said:
My c-2x is cool when off....
Click to expand...

Yes, my "other" US version C-2X is cool when off too. This one seems to be wired differently based on the schematic in my first post. Must admit I'm not that familiar with the switch notation (see my next post).
 
Avionic, this model only has two unswitched plugs on the rear. I should probably open her up but noticed that according to the schematic, if I understand the notation for the Japan and USA model versus the Regular model, it looks like with the former, the switch needs to be in the "on" position for current to go to the primaries for the Line and to the primaries for the Phono transformers.

But for the Regular model, it appears as if the one position leaves power on to the Phono section and the other gives power to both the Phono and Line circuits.
If somebody could validate my understanding of the above that would be much appreciated.

In the meantime, I ran an experiment. With this new, used C-2X unit power switch in the "off" position, I hooked up the output from a turntable to the "phono in" inputs in the rear of the unit and set the "record out" selector to phono. And I hooked up the record out plugs in the rear to the inputs of a power amp.

With Déjà Vu by CSNY spinning, and the power amp turned on, music played! This is with the C2X off.

So one may ask why I even submitted my original post to begin with. Well, at first I didn't know what was going on. Then I looked at the schematic (I'm a newbie when it comes to tracing the signal path or even power) and guessed that this unit is wired for the phone preamp to be on all the time. Why? Who knows?

Am I reading the schematic correctly? My experiment seems to validate the fact that the phono preamp must be working.

Cheers,
John
 
samosui said:
Avionic, this model only has two unswitched plugs on the rear. I should probably open her up but noticed that according to the schematic, if I understand the notation for the Japan and USA model versus the Regular model, it looks like with the former, the switch needs to be in the "on" position for current to go to the primaries for the Line and to the primaries for the Phono transformers.

But for the Regular model, it appears as if the one position leaves power on to the Phono section and the other gives power to both the Phono and Line circuits.
If somebody could validate my understanding of the above that would be much appreciated.

In the meantime, I ran an experiment. With this new, used C-2X unit power switch in the "off" position, I hooked up the output from a turntable to the "phono in" inputs in the rear of the unit and set the "record out" selector to phono. And I hooked up the record out plugs in the rear to the inputs of a power amp.

With Déjà Vu by CSNY spinning, and the power amp turned on, music played! This is with the C2X off.

So one may ask why I even submitted my original post to begin with. Well, at first I didn't know what was going on. Then I looked at the schematic (I'm a newbie when it comes to tracing the signal path or even power) and guessed that this unit is wired for the phone preamp to be on all the time. Why? Who knows?

Am I reading the schematic correctly? My experiment seems to validate the fact that the phono preamp must be working.

Cheers,
John
Click to expand...

If I were you John. I'd box that thing up and send it to me..:D I'd even pay shipping.:thmbsp:
 
avionic said:
If I were you John. I'd box that thing up and send it to me..:D I'd even pay shipping.:thmbsp:
Click to expand...

Uh, I think I threw the box away already ;)

Thanks though. If this or one of my other units needs repair I'll be sure to see if you have much of a backlog. You do great work.

Cheers,
John
 
Time to put my C-2x back into rotation. Great preamplifier and phono stage! :yes:
 
Thanks everyone for your replies and links and thoughts.

Based on some posts from years ago, my experimenting, and most of all, the schematic that nobody seems to want to acknowledge ;) , there are some models where there is a relay and indeed these do go stone cold when the power switch is in the off position. These are called the Japan and USA model in the schematic.

Then there are the "Regular" models as shown in the schematic, where there is no relay and there is indeed power going to the phono preamp circuit, even when the power switch is in the off position. Hence there have been "reports" of units staying warm, mine being one of them.

I guess if I really wanted to I could just plug the pre into a power strip and turn off all of the power that way. Will decide later :).

Happy listening to all :music:
John
 
samosui said:
Then there are the "Regular" models as shown in the schematic, where there is no relay and there is indeed power going to the phono preamp circuit, even when the power switch is in the off position. Hence there have been "reports" of units staying warm, mine being one of them.
Click to expand...

My old one(timofred's one now) being another one. Thank you for clearing that up. I always wondered why I could use the phono stage, via the tape-outs, when it was turned off. :thmbsp:
 
When I was repairing C-2x, which I bought broken, I noticed that it was wired to always be ON. Looking at schematic, it does not seem to be correct. So In rewired it according to schematic in service manual. My unit was universal with 120/240V switch.
 
for_p1 said:
When I was repairing C-2x, which I bought broken, I noticed that it was wired to always be ON. Looking at schematic, it does not seem to be correct. So In rewired it according to schematic in service manual. My unit was universal with 120/240V switch.
Click to expand...

Your answer would appear to be in the post below in bold.


samosui said:
Thanks everyone for your replies and links and thoughts.

Based on some posts from years ago, my experimenting, and most of all, the schematic that nobody seems to want to acknowledge
attachment.php
;) , there are some models where there is a relay and indeed these do go stone cold when the power switch is in the off position. These are called the Japan and USA model in the schematic.

Then there are the "Regular" models as shown in the schematic, where there is no relay and there is indeed power going to the phono preamp circuit, even when the power switch is in the off position. Hence there have been "reports" of units staying warm, mine being one of them.

I guess if I really wanted to I could just plug the pre into a power strip and turn off all of the power that way. Will decide later :).

Happy listening to all :music:
John
Click to expand...
 
I'd feel better if someone familiar with schematics (and the notation used) would chime in and say that my interpretation is correct (or not). Fact is, here have been at least a couple of C-2X owners (with the switchable power) that have noticed our units staying warm and with the phono preamp working, all with the front panel switch in the off position. Simple "work around" is using a power strip if that bothers anyone.

There was a C-2X with switchable power on eBay recently. Let's see if the new owner notices anything and if so, it they know about AK and if they post a question here ;)

Cheers,
John
 
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