Mine seems to be leveling off at around the 18mv mark. It will go a bit lower if I left it.
These are nearly 35 years old though.
It does. Leakage is higher at higher voltages for electroylitics.
I put a 2.2uF film cap on test and the voltage soon dropped right down within minutes ending up at 0.00 (no measurable leakage with this test set up).
Volume control was scratchy while turning it without the knob, directly touching its brass shaft , especially so in the right channel. C505 and C506 are ELNA RLB 1uF 50V which we just measured on battery for leaking. After 20 hours it settled on 3.6mV and wouldn't go lower, I would say that is LN result. Would you agree?
I checked popping in amplifier once more, left channel is still silent and I noticed no further improvement in the right channel so I turned it off.
If touching the chassis causes changes, then you have a power supply problem. Something's not ground properly maybe.
The volume control is something to look at later 🙂
That leakage seems a good result. I think though that it's important that it can achieve that fairly quickly as you can't be leaving the amp on 24/7
So where are we up to now ? Are we waiting for these new caps ?
I would wait for the new caps if you agree.
I ordered some WIMA MKS2 4,7uF, 50V from one source and some ERO VISHAY MKT1826 4.7UF 40V Vishay - Vishay's New Metallized Polyester Film Capacitor Provides High Reliability, Versatile Performance from another, it was my plan to install whatever reaches shores of Croatia first, but I am open for suggestions🙂
In the meantime I will receive Panasonic's Polyester caps ECQV1 in 1uF/63V value so we can exchange C505/C506 and C527/C528, although considering ELNAs good performance that is probably unnecessary, but to be absolutely sure there is no leakage I would rather do so.
That sounds like a plan 🙂
The WIMA and Vishay will both have virtually zero leakage and so too the Panasonics.
If any of the caps have the wrong lead spacing then it's worth redriiing the PCB (either 0.8 or 1mm) along the track somewhere so that they are a perfect fit. Much better than bending leads or soldering extension wires on them.
The WIMA and Vishay will both have virtually zero leakage and so too the Panasonics.
If any of the caps have the wrong lead spacing then it's worth redriiing the PCB (either 0.8 or 1mm) along the track somewhere so that they are a perfect fit. Much better than bending leads or soldering extension wires on them.
I am glad you approve of it.
So WIMA or Vishay are equally good solution, FCFS (first-come, first-soldered) it is then, as soon as the first batch of caps arrives I will report here.
In the meantime, if I may ask, can you think from time to time about possible alternate causes of this symptoms, just for backup🙂
Sometimes the problem is best analyzed when certain distance is made from it.
Thank You
Marko
Plan B you mean 😉
There isn't one ! The switch will be silent 🙂 How dare it not be after all this !
There isn't one ! The switch will be silent 🙂 How dare it not be after all this !
No need for plan B indeed🙂. ERO VISHAY MKT1826 4.7uF (well 4.4uF according to my DVM) arrived first and settled in Rotel. I am absolutely sure that the switch is now silent in operation from BOTH channels on speakers and on headphones and I can see no speaker cone movement while pressing it😀.
Unfortunately, those Panasonic caps 1uF for C505/C506 and C527/C528 I expected to arrive first are not here yet.
I am cautiously happy about this positive result, and very much curious about volume pot problem, no chance of this cap change solving both problems?
Excellent 🙂
The pot, well we will have to see. That's another different issue. We take it one step at a time wiring it carefully and checking as we go along. It may well be OK when it is all connected up though.
At least the amp circuit itself seems OK now.
The pot, well we will have to see. That's another different issue. We take it one step at a time wiring it carefully and checking as we go along. It may well be OK when it is all connected up though.
At least the amp circuit itself seems OK now.
Hi Mooly,
so the plan is to wait for 1uF caps and then troubleshoot potentiometer?
Thanks
Marko
I guess so, although you could fit these new 4.7 uf caps if you have any spare for C505/6 and then rewire the volume control one step at a time checking along the way.
We know those type of caps to be good with the amp itself now silent.
It's worth looking over all the work that has been done and making sure nothing has been left disconnected or not soldered properly.
We know those type of caps to be good with the amp itself now silent.
It's worth looking over all the work that has been done and making sure nothing has been left disconnected or not soldered properly.
We will wait for the new caps then, I left amp in post #217 state (Q504,Q502,C516,C510 removed), can I in the meantime revert those changes?
Yes you can build it all back up again.
And then with either the new 1uf (or if you want the 4.7 uf's) fitted for C505/6 we again connect the negative side of those to ground just like before to make sure it is silent.
As in post #66
And then with either the new 1uf (or if you want the 4.7 uf's) fitted for C505/6 we again connect the negative side of those to ground just like before to make sure it is silent.
As in post #66
I will solder those back then.
Although I have spare 4.7uFs, I would rather wait for the real substitutes to arrive, that should be real soon I guess, just to spare the board of unnecessary soldering.
Is that alright with you?
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