Yamaha A-1 Repair and restore: beyond Deoxit

mouser does not have anything called mylar cap. do you guys know what is the alternative?
 
across the postiove and negative legs of the cap? should it be 51? shouldnt it be 63 volts?
it says 63 volts on the cap
 
No, no , 63V is the maximum voltage this capacitor can hold . Over this value it will explode .
51DCV is value that you schould find across the both pins of each capacitor . One is +51V the other one should be -51VDC (values given between ground and + of capacitor working on positive rail and between ground and - for the negative side)
That's what Avionic recommended you to find
 
No, no , 63V is the maximum voltage this capacitor can hold . Over this value it will explode .
51DCV is value that you schould find across the both pins of each capacitor . One is +51V the other one should be -51VDC (values given between ground and + of capacitor working on positive rail and between ground and - for the negative side)
That's what Avionic recommended you to find
got it. thanks.
 
I measured the rail voltage which is 52.7V across each cap. ill replace the fried resistors R119,120,121, 122 and the emitter resistors and the fusible resistors and then take it from there i guess.
 
You should build a DBT before plowing ahead or this is going to end in blown outputs (if it hasn't already).
Just slow down a bit. Resistors don't usually fry without something else being wrong.
Does the relay still click on a few seconds after power-on?
Are you testing with a load (resistor) attached to the speaker terminals? I would have no load connected, at this stage.
one for left channel measures 6.6 ohm and the one for right measures 1.63 MEGA OHMS
High resistance usually means resistor blown (open circuit). You need to remove from circuit or at least desolder one leg to measure correctly. For transistors at least two legs.

Like clinic said, changing the volume should not affect bias. If you see a problem you definitely shouldn't keep running the amp because you'll likely blow up more things than you can visually see failing, especially while on full mains power.
 
You should build a DBT before plowing ahead or this is going to end in blown outputs (if it hasn't already).
Just slow down a bit. Resistors don't usually fry without something else being wrong.
Does the relay still click on a few seconds after power-on?
Are you testing with a load (resistor) attached to the speaker terminals? I would have no load connected, at this stage.

High resistance usually means resistor blown (open circuit). You need to remove from circuit or at least desolder one leg to measure correctly. For transistors at least two legs.

Like clinic said, changing the volume should not affect bias. If you see a problem you definitely shouldn't keep running the amp because you'll likely blow up more things than you can visually see failing, especially while on full mains power.

I had to find out which element is smoking because i was not getting anywhere and everyone else also ran out of ideas. I was hoping someone here knew why when i touch the volume pot, it changes/shoots up the bias voltages and everything goes haywire. just like ya'll mentioned does not make any sense, so at this point i'm either gonna just order every component on that board (as many as i can find on mouser), replace everything and then try again and if that doesnt work then trash can it is.
 
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yes the relay clicks, the power amp board bias point is correct and stable at 35V.
I was testing with a load when i found the smoking resistor.
 
I had to find out which element is smoking because i was not getting anywhere and everyone else also ran out of ideas. I was hoping someone here knew why when i touch the volume pot, it changes shoots up the bias voltages and everything goes haywire. just like ya'll mentioned does not make any sense, so at this point i'm either gonna just order every component on that board (as many as i can find on mouser), replace everything and then try again and if that doesnt work then trash can it is.
i do understand that those resistors are blown, i have ordered them already. i dont know why they would fry like that and just like you said, the reason they fry is probably = the root of the problem.

my point was that resistors can be bad but still measure some value so i cant trust that there are not more bad resistors that i just havent found because they dont test OL.
so basically measuring a component in circuit is useless? then why do it at all?
 
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so the rail voltage is not exactly 51. it is probably because of those blown resistors and possibly caps around it, right?
 
You can buy 2 thousand electronics components and you will burn them all if you don't work logically . Changing components will not help you to understand what is wrong
you don't follow advice that everybody take time to give you
very strange way to act
 
You can buy 2 thousand electronics components and you will burn them all if you don't work logically . Changing components will not help you to understand what is wrong
you don't follow advice that everybody take time to give you
very strange way to act
im not sure what you mean. other than your advice to take that board out and ship it to repair, i am asking for advice and i am following them. the reason i dont want to take the board out is that it is impossible to take out. it has wires on all 4 sides that go both over and under it so i will either have to remove every wire from the connection or just cut the wires in the middle. other than that the whole point of these 10 pages is to askj advice and then act on it, if there is any advice that i missed is because i didnt understand it not that i asked for it and then didnt do it just for kicks.
 
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im gonna go over the previous pages and find the advice or tips that i missed or questions that i forgot ti answer. sorry that i have obviously frustrated you and probably avionic.
 
You can buy 2 thousand electronics components and you will burn them all if you don't work logically . Changing components will not help you to understand what is wrong
you don't follow advice that everybody take time to give you
very strange way to act
You should build a DBT before plowing ahead or this is going to end in blown outputs (if it hasn't already).
Just slow down a bit. Resistors don't usually fry without something else being wrong.
Does the relay still click on a few seconds after power-on?
Are you testing with a load (resistor) attached to the speaker terminals? I would have no load connected, at this stage.

High resistance usually means resistor blown (open circuit). You need to remove from circuit or at least desolder one leg to measure correctly. For transistors at least two legs.

Like clinic said, changing the volume should not affect bias. If you see a problem you definitely shouldn't keep running the amp because you'll likely blow up more things than you can visually see failing, especially while on full mains power.

putting these two together, i guess i should remove all the components in question from the board and measure them separate before ordering anything. i will either put the original back or the new one, huh?
 
emitter resistors removed. all 4 of them measure .6 ohm

off topic:
one good thing about this project, is that before this i was pretty mediocore ot soldering and just horrendous at desoldering, now im pretty good at both which help me with my project of building a the Soekris R2R dac.
 
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