Yamaha CA-1010 - is big current draw OK even in AB mode?

[vibroverbus]

Just started to poke around on a busted CA-1010, in which relays don't seem to click on properly. Have read previous posts suggesting common failure modes for this one including:

• Relays
• Solder joints
• Dirty switches & pots in various places

Haven't attended to all of those yet... I certainly will, but there's another question bothering me - running it on the trusty variac (always on the bench if only for the ammeter to keep an eye on currrent draw for un-trusted pieces). It seems this unit draws a lot of current all the time, even if it's not in "Class A" mode (and yes I know what Class A is). Flipping the mode switch doesn't cause a noticable change in the current draw although seems like a slightly different sequence of clicking noises comes from the relays.

I would have expected the high draw in Class A but for it to drop considerably in AB mode. Specifically it is pulling something around 1.5-1.8amps with switch in either position (and no input signal applied). From a quick look, basic PS voltages seem essentially correct. Haven't dug much further yet.

Can anyone suggest what 'correct' current draw would be to expect on this unit? Is there a known failure for them getting stuck in Class A (aka switch or the related relay)? No DC on outputs by the way, that's always my first check before allowing anything to come near speakers...

 

[avionic]

Check your power supply voltages first. I would just about suspect you need to recap power supply/regulator board.Then check for any significant DC voltage on the amplifier output.This will need to be measured somewhere before the protect relay.

 

[brutal]

And those micro switches for Class A mode are probably fried/fused.

 

[vibroverbus]

Check your power supply voltages first. I would just about suspect you need to recap power supply/regulator board.Then check for any significant DC voltage on the amplifier output.This will need to be measured somewhere before the protect relay.

Avionic - appreciate the quick draw reply.... but maybe you scanned a bit too quick - you'll see in the OP I note that I checked the supply volts and DC right off the bat (I may be dumb but at least I get a few of the basics right after the first 20 or 30 times). Both seem OK. And yep I checked outputs at the power amp board before the relays. Also BTW I checked for DC on the inputs to the power amp just in case... but nothing.

I haven't delved into the deets of the Class A switching system but I'm guessing from this whole current draw thing that it's something related to that... was just wondering if there's a known failure mode around it.

 

[vibroverbus]

And those micro switches for Class A mode are probably fried/fused.

Just the kind of thing I was wondering about...

 

[avionic]

Excuse me!.BTW the CA-1010 doesn't use microswitches to switch the high current, it uses a relay. Is the protect relay clicking shortly after "power on"? If your power supply is OK and no DC on the output.The protect circuit has a problem if the relay isn't switching properly. ie. bad RC timing capacitor or bad relay driver transistor(s) or solder connection or relay coil is open(unlikely).

 

[avionic]

Specifically it is pulling something around 1.5-1.8amps

Mains fuse is a 5-7 amp@117vac..1.5A is idling current..Bet the regulators in the PS are a little warm if not hot.Theres the current draw!.which is typical for these yamaha's.

 

[pradigmshift]

I read somewere, it draws 55 watts when idle in class B and over 130 watts idle in class A.

 

[brutal]

Excuse me!.BTW the CA-1010 doesn't use microswitches to switch the high current, it uses a relay. Is the protect relay clicking shortly after "power on"? If your power supply is OK and no DC on the output.The protect circuit has a problem if the relay isn't switching properly. ie. bad RC timing capacitor or bad relay driver transistor(s) or solder connection or relay coil is open(unlikely).

My bad, assumption made on the CA-1000. Thanks for sorting it out.

 

[vibroverbus]

Excuse me!.BTW the CA-1010 doesn't use microswitches to switch the high current, it uses a relay. Is the protect relay clicking shortly after "power on"? If your power supply is OK and no DC on the output.The protect circuit has a problem if the relay isn't switching properly. ie. bad RC timing capacitor or bad relay driver transistor(s) or solder connection or relay coil is open(unlikely).

Thanks Av. The relay clicks but back and forth in usual "something has gone bad" way. So I won't worry about the idle current for the moment (although am still suspecting it's stuck in A mode).

Both relays appear to be replaced with new Omron's, I suspect that was a blind stab at fixing something else and original relays turned out not to be the core problem.

I'll dig in some more and report back - thanks for helpsing

 

[Raynald]

Don't you wish that all of your problems were just a loose ground wire!

 

[vibroverbus]

Don't you wish that all of your problems were just a loose ground wire!

Hey don't rule that out yet!

JC's Correlary to Murphy's Law states:
'Simple 5 second fixes only are discovered after several days of painstaking work on other areas'.