Yamaha CA-810 Relay Randomly Engages
- Thread starter AngelAT
- Start date
AngelAT
Well-Known Member
So today it took a few hours for the relay to start acting again...
What I did is I cleaned both boards.
Measured voltages again:
TR606
e-> 38.9 v
c-> 38.8 v
b-> 38.3 v
TR605
e-> 78 mV
c-> 0 v
b-> 0.8 v
TR604
e-> 0 v
c-> 78 mV
b-> 0.7 v
TR601
e-> 0 v
c-> 0.7 v
b-> 11 mV
Then I replaced both D602 and D603 with 1N4148
Now waiting...
What I did is I cleaned both boards.
Measured voltages again:
TR606
e-> 38.9 v
c-> 38.8 v
b-> 38.3 v
TR605
e-> 78 mV
c-> 0 v
b-> 0.8 v
TR604
e-> 0 v
c-> 78 mV
b-> 0.7 v
TR601
e-> 0 v
c-> 0.7 v
b-> 11 mV
Then I replaced both D602 and D603 with 1N4148
Now waiting...
Sparkplug
Super Member
LOL, don’t despair, it’s part of the journey....and it clicks again...
Is this still the original relay? Any chance it can be changed just to be sure?
AngelAT
Well-Known Member
AngelAT
Well-Known Member
When I turn the amp on and before the relay releases, the voltage at TR604 starts from 0.2 - 0.3v and goes up to 0.7v. During operation, when the relay cuts off the voltage drops down to ca. 180mV, then starts to build up until it gets to 0.7 and then the relay turns on again.
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AngelAT
Well-Known Member
Today again biased the 25V and the L and R channels.
I was thinking, could the problem come from the power supply? In this unit the PS is the 8xx board, right?
The other anomaly is that sometimes I turn it on and the relay starts to click on and off almost immediately after the initial check. And sometimes it takes a few hours. The amp stays on my bench, I am not moving it around.
I was thinking, could the problem come from the power supply? In this unit the PS is the 8xx board, right?
The other anomaly is that sometimes I turn it on and the relay starts to click on and off almost immediately after the initial check. And sometimes it takes a few hours. The amp stays on my bench, I am not moving it around.
Great, so the question becomes, what causes TR604b to drop to 180mV, effectively turning off TR604.
Time for another "brainstorm" so input from others very welcome.
Trying to understand the basic operation of the protection circuit and how it behaves when excessive Vdc is detected.
My take... a +ve offset at TR601b will cause TR601 to conduct.
A -ve offset at TR602b turns on TR602 and then TR603.
With TR601 or TR603 on means increase current through R604,5,,, (and associated volt drop) results in a drop in voltage at TR604b (eg, 180mV) effectively turning off TR604 and removing the current path from TR606e,b TR605,4. The reduced current flow should cause TR605c/TR606b voltage to raise possibly to the point where TR606 is reversed biased (some circumstantial eveidence this occurred)
Candidates are TR601,2,3, and breakdown of D602(replaced) so need to go over the trackwork in this area. Past measurement has TR601b being rock solid xxmV, so monitoring voltages at TR603b and TR601e (or TR602e) may help to further localize.
Trying to understand the basic operation of the protection circuit and how it behaves when excessive Vdc is detected.
My take... a +ve offset at TR601b will cause TR601 to conduct.
A -ve offset at TR602b turns on TR602 and then TR603.
With TR601 or TR603 on means increase current through R604,5,,, (and associated volt drop) results in a drop in voltage at TR604b (eg, 180mV) effectively turning off TR604 and removing the current path from TR606e,b TR605,4. The reduced current flow should cause TR605c/TR606b voltage to raise possibly to the point where TR606 is reversed biased (some circumstantial eveidence this occurred)
Candidates are TR601,2,3, and breakdown of D602(replaced) so need to go over the trackwork in this area. Past measurement has TR601b being rock solid xxmV, so monitoring voltages at TR603b and TR601e (or TR602e) may help to further localize.
Sparkplug
Super Member
@AngelAT ,
Thanks for posting the voltages. Is it at all possible to measure these voltages when the fault occurs, for comparison purposes? I understand it’s a difficult task but it would also shed light on what’s happening and possibly finding an explanation and a fix. It’d also go to verify what @mbz is suggesting.
Also, the schematic shows the relay open, is this the normal operation state of the relay (open)? Are the voltages shown on the schematic for when the relay is open?
Thanks for posting the voltages. Is it at all possible to measure these voltages when the fault occurs, for comparison purposes? I understand it’s a difficult task but it would also shed light on what’s happening and possibly finding an explanation and a fix. It’d also go to verify what @mbz is suggesting.
Not a bad theory, up to Tr604 affair I can see this happening, but after that it’s not clear for me, and not because of the theory itself, but because I’m not exactly sure what roles Tr604, 5 play and how. Maybe if @AngelAT could collect the same set of voltages for when the relay is at fault (open?), then the picture could become a bit clearer by comparison? Easier said than done given the short time the relay stays open.
Also, the schematic shows the relay open, is this the normal operation state of the relay (open)? Are the voltages shown on the schematic for when the relay is open?
I see TR605 as AC detection, more so at power off to quickly release the relay.
TR604 is just a switch(?) controlled by TR601 (+ve offset) and TR603(-ve offset)
Sparkplug
Super Member
Agree,
. Its base is even setup through the rectified but unfiltered voltage right out of the bridge, so upon switch off, stored charge in big filter caps won’t keep it going for extra seconds, milliseconds, or whatever, instantly cuts the relay through Tr605 (guessing 
)I realized this after my last post earlier but the mechanism isn’t crystal clear yet (to me).
Also, still don’t know what triggers all this. Maybe @AngelAT is right, maybe the supply itself is playing games due to whatever reason. Worth monitoring for sure, especially that AC line that could potentially open the relay if it in fact cuts in and out …
Edit: Forgot to upload this schematic populated with the data we have so far:
Green for relay engaged, Red for the opposite.
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AngelAT
Well-Known Member
It is taking some time to get the voltages when the relay is "acting"
So far what i have is (when relay cuts):
TR606
e->39.3V
c->6mV
b->39.2V
TR605
c->0V
b->3.51V
TR604
e->0V
c->3.7V (going down to 2.9V)
TR601
b->14mV (goes up to 20mV)
This is what I have so far
So far what i have is (when relay cuts):
TR606
e->39.3V
c->6mV
b->39.2V
TR605
c->0V
b->3.51V
TR604
e->0V
c->3.7V (going down to 2.9V)
TR601
b->14mV (goes up to 20mV)
This is what I have so far
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Sparkplug
Super Member
Thank you for new measurements, I know they take time and are cumbersome. Time permitting, could you measure the voltages marked in orange in the diagram below which is updated with the newly provided data? That’s is to check if there are any changes in the supply voltages.
Tr605b is going from 0.8V to 3.51V. It is fed through R613 directly from rectified but not yet smoothed output of the bridge rectifier. Is it detecting anomalies in the supply voltage (per post 70)? Is this what’s causing Tr606b go up by a volt and effectively shutting it off?
Edit: In post 67, it was described that, Tr604b builds up its voltage from 0.18V to 0.7V during the relay release/close cycles. This voltage is also Tr601c voltage, why would that have to build up? It’s fed directly from the 25V supply rail voltage through R604, 5. Tr601b is essentially not changing unless you consider 0.011V—>0.02V significant
Tr605b is going from 0.8V to 3.51V. It is fed through R613 directly from rectified but not yet smoothed output of the bridge rectifier. Is it detecting anomalies in the supply voltage (per post 70)? Is this what’s causing Tr606b go up by a volt and effectively shutting it off?
Edit: In post 67, it was described that, Tr604b builds up its voltage from 0.18V to 0.7V during the relay release/close cycles. This voltage is also Tr601c voltage, why would that have to build up? It’s fed directly from the 25V supply rail voltage through R604, 5. Tr601b is essentially not changing unless you consider 0.011V—>0.02V significant
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Yes, I have to agree, @AngelAT has done a fantastic job, most people would have given up, mind you, the CA-810 is worth saving.
Time for some more brainstorming,
TR605 Vb increases since TR604 has shut down so low TR605 Ib and volt drop at R613.
Same with TR606b, ie, TR604 shuts down so low current through TR605Ic, D603, R604.
TR605 and TR604 provide a current path to GND that needs to be open for TR606 to correctly bias.
When a real dc offset occurs additional Ic through TR601 or TR603 causes higher volt drop through R605
setting TR604b to 180mV?
Possible minor error in schematic, would expect TR601e and TR602e to be connected to GND, ie, missing "dot"
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