@BakedAlaska,
When having difficulties in dismantling the upper board, you could connect a Cap from outside to R201 and R219 / R202 and R220 at exactly the points where you measured with the shortest possible leads.
Not as elegant, but probably just as effective in solving the problem without having to dismantle.
Hans
When having difficulties in dismantling the upper board, you could connect a Cap from outside to R201 and R219 / R202 and R220 at exactly the points where you measured with the shortest possible leads.
Not as elegant, but probably just as effective in solving the problem without having to dismantle.
Hans
Hans, this is what I will try.
But now I get it: the pin's solder holes are contacted-through, so I would need to solder only one side of the board, yes?
Sorry, I was thinking about how I would get it back together after dismantling.
But now I get it: the pin's solder holes are contacted-through, so I would need to solder only one side of the board, yes?
Sorry, I was thinking about how I would get it back together after dismantling.
Those contacted through holes are called “vias”.
And yes you can solder on either side of the PCB.
Hans
And yes you can solder on either side of the PCB.
Hans
Good, these are vias. Got confused why ML seemed to have soldered it neatly both sides.
Did you mean V_Prereg?
VUnreg (big blue caps 47mF) is 65V (65V noisy ML, 59V silent ML).
V_Prereg, P17 and P19, (smaller blue caps 1900uF) is 90V (93,5V noisy ML, silent ML 85,5V).
Why the difference? Noisy ML has tranformer jumper set to A-E G-H (=220-230V AC mains), silent ML has jumper set to A-F G-H (=230-240V AC mains).
I tried to set jumper to 230-240V for noisy ML, too, but than the relais doesn't click. I suspect they saved on the extra winding. Still weird. The marking (red dot) on the backplate is identical to both MLs.
BR
Did you mean V_Prereg?
VUnreg (big blue caps 47mF) is 65V (65V noisy ML, 59V silent ML).
V_Prereg, P17 and P19, (smaller blue caps 1900uF) is 90V (93,5V noisy ML, silent ML 85,5V).
Why the difference? Noisy ML has tranformer jumper set to A-E G-H (=220-230V AC mains), silent ML has jumper set to A-F G-H (=230-240V AC mains).
I tried to set jumper to 230-240V for noisy ML, too, but than the relais doesn't click. I suspect they saved on the extra winding. Still weird. The marking (red dot) on the backplate is identical to both MLs.
BR
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That is indeed weird.
It is almost as if this additional winding between E F was destroyed by some short circuit.
And if this would be the case, it could be that more components on the primary side are damaged such as the DC blocking circuitry.
ML specifies +/- 94V on Vprereg and +/- 64V on Vunreg, so your noisy amp is quite close and the silent amp is a bit low, probably because your mains is not 240V.
Hans
It is almost as if this additional winding between E F was destroyed by some short circuit.
And if this would be the case, it could be that more components on the primary side are damaged such as the DC blocking circuitry.
ML specifies +/- 94V on Vprereg and +/- 64V on Vunreg, so your noisy amp is quite close and the silent amp is a bit low, probably because your mains is not 240V.
Hans
They both have different transformer covers, but that seems normal, as there are also 2 different types of 27.5 transformer covers on the internet (there seems a 3rd version with greyish covers).
Btw mains is 230V, as should be.
BR
Btw mains is 230V, as should be.
BR
I have gray lids. What color do you have? Which covers are better? I was told that with gray covers were issued at the very end of the circulation of 27.5
One has the ones that the 27 had (without a screw hole) and one has black ones, looks like the grey otherwise. No idea what is better.
Ahh, the Bourns are the 4 trim pots, now I get it.
Your amp is now operational, I take it?
BR
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Sorry to keep you waiting, was blocked from working on the amp.
Hans, you are a genius. C201 C202 are the problem. I bypassed them with caps from outside, and the noise is gone.
Thank you very very much for your help!
I made a new measurement for P1 P4 for the right channel, and VReg +- looks so much better now.
BR
Hans, you are a genius. C201 C202 are the problem. I bypassed them with caps from outside, and the noise is gone.
Thank you very very much for your help!
I made a new measurement for P1 P4 for the right channel, and VReg +- looks so much better now.
BR
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Hey, thanks. Where did you get this? From Harman?
Well, I' contemplating should I a) take blue pill, slab on the caps and enjoy the music or b) take the red pill, dismantle the boards, replace caps & all the other stuff properly 😉
BR
Well, I' contemplating should I a) take blue pill, slab on the caps and enjoy the music or b) take the red pill, dismantle the boards, replace caps & all the other stuff properly 😉
BR
Apparently the used different 0.22uF - in one amp this are "EKM..", in the noisy these are Roedersteins.
BR
BR
Yes, this selection is from Harman.
Yes, these roe disgusting capacitors! I set myself a nichicon muse kz 22uf 100v. Harman recommends another nippon kmg 22uf 100v.
Don't be lazy and restore it completely! He deserves whatever you give him attention 🙂
@M.L.
My Russian is a bit rusty, but I'll figure it out, thanks 😉
(off-topic)
I'm so happy that my problem was fixed, here's a little anecdote: I had some bad experiences with Roe caps before. They are used in the power supplies of east german computers from the 80s (people collect these). They often leak and explode, and we call them 'fish cans', because when you put them in a box, it smells of fish for leaking electrolyte. The assumption is that these bad caps had been supplied to east germany, but apparently the problem is not limited to socialism. US (Madrigal) got framed with this stuff as well ;-)
BR
My Russian is a bit rusty, but I'll figure it out, thanks 😉
(off-topic)
I'm so happy that my problem was fixed, here's a little anecdote: I had some bad experiences with Roe caps before. They are used in the power supplies of east german computers from the 80s (people collect these). They often leak and explode, and we call them 'fish cans', because when you put them in a box, it smells of fish for leaking electrolyte. The assumption is that these bad caps had been supplied to east germany, but apparently the problem is not limited to socialism. US (Madrigal) got framed with this stuff as well ;-)
BR