'Identical' CA-1010's, both recapped, but possible different output levels?

nate86

Well-Known Member
I just finished re-capping two CA-1010's, except for about maybe 4 caps which look like you have to take the face of the unit off to reach. Set bias as best I could, and measured DC offset.

offset for 'quieter' amp: R channel: 18mv, L channel -2.2mv

Is it okay for this particular amp to have a neg. offset value? The other amp doesn't have negative values in either channel.

As a side note, even before recapping, I noticed that one amp was louder than the other, and that the meters on the front would show less power was being used when compared to the other CA-1010. Does this explanation make sense? Basically I have to crank the knob quite a bit more on one amp to get to the other one's output level...anyone have ideas as to where to start troubleshooting?
 
I just finished re-capping two CA-1010's, except for about maybe 4 caps which look like you have to take the face of the unit off to reach. Set bias as best I could, and measured DC offset.

offset for 'quieter' amp: R channel: 18mv, L channel -2.2mv

Is it okay for this particular amp to have a neg. offset value? The other amp doesn't have negative values in either channel.

As a side note, even before recapping, I noticed that one amp was louder than the other, and that the meters on the front would show less power was being used when compared to the other CA-1010. Does this explanation make sense? Basically I have to crank the knob quite a bit more on one amp to get to the other one's output level...anyone have ideas as to where to start troubleshooting?

- or + offset is insignificant.What counts is as close to zero as possible.
 
Good to know- I read this in the sticky thread, but wasn't sure if that applied to all amplifiers or just certain ones. Thanks for clearing that up!

I'm confused now about what to do, if anything :)
 
I just finished re-capping two CA-1010's, except for about maybe 4 caps which look like you have to take the face of the unit off to reach. Set bias as best I could, and measured DC offset.

offset for 'quieter' amp: R channel: 18mv, L channel -2.2mv

Is it okay for this particular amp to have a neg. offset value? The other amp doesn't have negative values in either channel.

As a side note, even before recapping, I noticed that one amp was louder than the other, and that the meters on the front would show less power was being used when compared to the other CA-1010. Does this explanation make sense? Basically I have to crank the knob quite a bit more on one amp to get to the other one's output level...anyone have ideas as to where to start troubleshooting?

Check "mute switch". Compare rail voltages on both .Are both in the normal mode or class A mode.Dirty switches , relay contacts and controls can impede the sound /volume output.Is there a universal voltage selector on these examples? If so , are they both selecting the same input voltage.
Just a few things to look at..
 
Ok so:
-Mute switches definitely aren't on, but I'll hit them with more deoxit

-Rail voltages (both are in class AB right now) are 24.7mv for quieter one and 25mv for other one. (It's REALLY hard on these to fine tune them once you get close to the voltage you want...I'm talking about minuscule, tiny nudges with a tiny screwdriver in a given direction...anyways)

-Could be dirty switches still; have blasted both with deoxit already but will do so again and make sure! (One thing I have noticed; quieter amp has slight balance knob issue where if you turn it, sometimes this will also drag the volume knob along with it a little bit, in the same direction. But when comparing output obv the balance is centered etc.)

-Universal voltage selector- neat idea to check; forgot that these could possibly come with them. Unfortunately neither of mine have this though.


If it is of any help or interest, the serial numbers are 07542 on the quieter one and 12046 on louder one. They have slightly different parts inside (I just noticed the basics- adjustment resistors for rail voltage have slightly different styles, different bulb styles, power filter caps slightly diff lettering, etc.). Probably doesn't mean anything though, I'm assuming.

The louder one had a bit of a heat stroke before I recapped it; caps on the power supply board were melty, etc., whereas the quieter one had very very few signs of high heat over the years. Not sure if that helps or is relevant...time to buy another can of deoxit though!
 
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D'oh! No wonder why one is so quiet...

just kidding. I'm new to this, can you tell? :) Okay, so hopefully I didn't kill the power supply. I have sound. It sounds nice, I think.

I think what I meant was idling current was 25mv?

I've got the service manual as a PDF open here and I can't see any mention of rail voltage, but then again I'm sure there's another word for it or something...
 
I'm a moron...(correct me if I use the wrong wording here or am just flat out wrong)-I think I only adjusted one of the idling current channels. Now I see that there are two places to adjust so that you get 25mv (I'm assuming one for R and one for L). Looking at the 'quiet' amp again- one side reads ~20mv and the other reads .1mv
 
D'oh! No wonder why one is so quiet...

just kidding. I'm new to this, can you tell? :) Okay, so hopefully I didn't kill the power supply. I have sound. It sounds nice, I think.

I think what I meant was idling current was 25mv?

I've got the service manual as a PDF open here and I can't see any mention of rail voltage, but then again I'm sure there's another word for it or something...

I kinda figured you were measuring The bias (idle current). The "rail" voltage is easiest measured at the big filter caps or on the output transistor collectors(metal case) "Rail" is just a sort of jargon for the output transistors collector voltage.
 
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I'm a moron...(correct me if I use the wrong wording here or am just flat out wrong)-I think I only adjusted one of the idling current channels. Now I see that there are two places to adjust so that you get 25mv (I'm assuming one for R and one for L)

Adjust by the manuals adjustment procedure. Each amplifier module has 2 idle current(bias) adjustments, one for class AB and one for class A VR301 and 302.. Check the service manual!!
 
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Thanks - thanks, thanks thanks!

For some newbie reason, I didn't know you were supposed to adjust the knobs on both the L and R circuit boards, so one was terribly low. Adjusted both sides, and for both AB and B, respectively. I think that might have been the problem :). Sounding much better too. I'll have to double check the other one tomorrow, but this seems promising. Maybe it's just in my head, but it sounds better as well. DC offset didn't really improve though, bummer.


It's just hard for someone who is new to this stuff- while I may have the service manual open, it doesn't explicitly say, hey dude, adjust BOTH little knobby things on the R AND the L side of the circuit board. Maybe that's supposed to be common sense though. :D. Live and learn...
 
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Did you set the voltages to the SM specs?


AB = 25mV VR301
A = 280mV VR302

You can't just set AB, then set A, then done. Have to go back and forth until they're both dialed in. Give each enough time to settle, esp A/B, before readjusting.
 
Thanks for the tip- I was checking them again today out of boredom and noticed they had to be readjusted again. So, good to know that some readjustment is needed for both AB and A and is normal. I turned them on and waited for about 20 mins before checking and adjusting- good amount of time?
 
Plenty of time for warmup. When switching from A to AB, wait about 30 seconds or more for the idel current to stabilize. About 10-15 seconds going AB to A.
 
I just finished re-capping two CA-1010's, except for about maybe 4 caps which look like you have to take the face of the unit off to reach.
I reckon the 8 caps of the meter board or the 4 caps on the tone control board? The latter can be soldered by removing both top and bottom cover.

One thing I have noticed; quieter amp has slight balance knob issue where if you turn it, sometimes this will also drag the volume knob along with it a little bit, in the same direction.
This can be fixed by repositioning the volume and balance knob. One is fixed with one hex screw and the other by two hex screws. These can be accesed on the right side on the unit with an Allen key when the top cover is off.
 
This can be fixed by repositioning the volume and balance knob. One is fixed with one hex screw and the other by two hex screws. These can be accesed on the right side on the unit with an Allen key when the top cover is off.

Only the balance knob is secured by set screws. The volume knob just presses onto a split-splined shaft. It could need a little adjustment, but I suspect the issue is internal where the two shafts meet, not the knobs.

Pull the volume knob off and spray a little faderlube between the silver splined shaft (volume) and brass outer shaft (balance)

My CA-1000 that has the opposite issue. The tone controls L/R are supposed to lock together via drag on the inside of the shafts and the treble one is too slippy and doesn't.
 
In an attempt to replace those caps I managed to give the meter button a little 'love tap' with my soldering iron and this was the result:

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Ouch. :tears:

This was a pretty pristine amp...I'd hate to leave it like this. Anyone know where I could get another one of those buttons or have any suggestions about what to do?
 

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A short sleeve of heat shrink tubing, in the colour of your choice…

Either that or bondo, sanding & painting.
 
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Usually hard to come by, particularly when people glue on the button. Soooo.... that means you might need to find a whole switch, button intact, unless you cover it or repair it.
 
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