These should have been + 59 vdc
Yamaha M-65 protection mode - seeking help
- Thread starter tocomplero
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- m-65 protection circuit yamaha
These should have been + 59 vdc
It is much easier to access the test points from the solder side of the board.
tocomplero
New Member
Thanks for the input Asmodeus!
The resistor you pointed out seems to only be sold only in the US and the shipping to Germany is high... I'm looking at these other ones by Royal Ohm, that seem to have the same the features as the Stackpole ones, with the difference that Royal Ohm have a maximum overload voltage of 500v instead of 600v.
all info is here:
https://www.tme.eu/de/details/1_4w22r/tht-resistors/royal-ohm/cfr0w4j0220a50/
https://www.tme.eu/Document/fee7eb1775f93f5b65ea77d5d9cb8c5c/cfr.pdf
The resistor you pointed out seems to only be sold only in the US and the shipping to Germany is high... I'm looking at these other ones by Royal Ohm, that seem to have the same the features as the Stackpole ones, with the difference that Royal Ohm have a maximum overload voltage of 500v instead of 600v.
all info is here:
https://www.tme.eu/de/details/1_4w22r/tht-resistors/royal-ohm/cfr0w4j0220a50/
https://www.tme.eu/Document/fee7eb1775f93f5b65ea77d5d9cb8c5c/cfr.pdf
tocomplero
New Member
hello! update:
I removed the R141 and R142 resistors, along with C157 and C158.
Cleaned all the glue residue, and luckily it had not touched anything else, so I think it's safe now.
Soldered C157 and C158 back in place, as well as the new resistors that just arrived yesterday.
Everything is reading in order: the coils from the amplifier outputs read close to 0v, and the 8 output transistors read about 11v (and -11v on the other side).
Now, the light of the bulb tester is shining very bright, and after some measurements, I realised that I didn't order 22ohm resistors, but rather 0,22ohm......so I took them out and now I wait for the new parts to arrive.
I suspect this might be the only faulty part in the circuit. Is there anything else I should be testing for?
I removed the R141 and R142 resistors, along with C157 and C158.
Cleaned all the glue residue, and luckily it had not touched anything else, so I think it's safe now.
Soldered C157 and C158 back in place, as well as the new resistors that just arrived yesterday.
Everything is reading in order: the coils from the amplifier outputs read close to 0v, and the 8 output transistors read about 11v (and -11v on the other side).
Now, the light of the bulb tester is shining very bright, and after some measurements, I realised that I didn't order 22ohm resistors, but rather 0,22ohm......so I took them out and now I wait for the new parts to arrive.
I suspect this might be the only faulty part in the circuit. Is there anything else I should be testing for?
Asmodeus2112
Super Member
DBT is an invaluable tool! IMO, nothing until you get the 22Ohm resistors in. I wouldn't run it for long if the bulb stays bright.
What pins are you seeing 11 vdc on ?
tocomplero
New Member
hello!
I'm sorry it took so long to reply. I left home for a couple of months and only returned last week. I resumed the job as soon as the correct resistors arrived, quickly exchanged them, did some measurements and voila!! it works now!!
it sounds beautiful! such a fat and well rounded tone.
one thing I didn't get is why my DBT still lights up though? I thought it was meant to stay off if the circuit works correctly. is it actually still not fixed entirely? I also can't get any readings from the "idle current" test points. always 0v on both sides, even if I turn the bias adjustment part...surely something is not right, but I'm not sure..I don't event know what this is for. at least the unit turns on past the protection mode and plays music.
here's all the readings I did:
TR131 4.7
TR132 4.2
TR133 4.7
TR134 4.2
TR135 -4.4
TR136 -4.5
TR137 -4.4
TR138 -4.5
L101 0.4
L102 0.4
R142 6.9 both ends
R141 -6.9 both ends
thanks SO MUCH to both of you for the attention and help, specially avionic, you da real MVP!!
I'm sorry it took so long to reply. I left home for a couple of months and only returned last week. I resumed the job as soon as the correct resistors arrived, quickly exchanged them, did some measurements and voila!! it works now!!
it sounds beautiful! such a fat and well rounded tone.
one thing I didn't get is why my DBT still lights up though? I thought it was meant to stay off if the circuit works correctly. is it actually still not fixed entirely? I also can't get any readings from the "idle current" test points. always 0v on both sides, even if I turn the bias adjustment part...surely something is not right, but I'm not sure..I don't event know what this is for. at least the unit turns on past the protection mode and plays music.
here's all the readings I did:
TR131 4.7
TR132 4.2
TR133 4.7
TR134 4.2
TR135 -4.4
TR136 -4.5
TR137 -4.4
TR138 -4.5
L101 0.4
L102 0.4
R142 6.9 both ends
R141 -6.9 both ends
thanks SO MUCH to both of you for the attention and help, specially avionic, you da real MVP!!
Hello sir. Though you're getting the best help already, I gotta chime in a little so I feel relevant or something. The 40 watt bulb on your DBT is too small. Recommend 100 watt minimum, old school incandescent bulb.
Do not set the DC bias idle current while it's plugged into the DBT when you're near completion. Otherwise the bias will shoot up to 17-20 mV in a regular power outlet afterward, and possibly trip the protection light from over-bias.
Soldering: heat the component, not the board, 2 seconds.
Those are great amps. Good choice. Pounded out 3 of them in recent years. 2 of them shat the entire bed.
Do not set the DC bias idle current while it's plugged into the DBT when you're near completion. Otherwise the bias will shoot up to 17-20 mV in a regular power outlet afterward, and possibly trip the protection light from over-bias.
Soldering: heat the component, not the board, 2 seconds.
Those are great amps. Good choice. Pounded out 3 of them in recent years. 2 of them shat the entire bed.
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Me too! Getting harder & harder to find incandescents. ACE hardware seems my only option left.
So with a 150 watt bulb in the DBT, it should get bright for 2-3 seconds upon power up, then dim way down to little more than an orange filament glow. That means no short circuits. You could still have opens though, disclaimer.
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