Apologies, I take all input gratefully. I am currently researching the certified caps as you suggest. It just takes me time to find one that I am able to get hold of quickly.
As to your further suggestions that I replace power resistors and reflow soldering, I am in full agreement.
That said, I do not believe these resistors or any of the soldering to be root cuase of the issue I am currently debugging. I have already visually checked and measured all power connections on the PCB to check for dry joints etc. That said, if/when I actually get this thing up an running again, I will absolutely set about replacing all components that can be improved (tant caps, power resistors etc).
In the meantime, thank you again for your input so far. Rest assured, I am taking it very seriously.
First reflow all connections, replace suspected parts. Only then think of the original subject "tantalum caps".
There is a chance that it will work again with the new 1 kV cap. AFAIK it is a switcher (you know that wonderful invention we all benefit from in audio 🙂) and finding errors in these is both tedious and time intensive. Without schematics one needs experience and maybe just maybe in this case simple replacements if you are lucky. That is gambling but it sometimes works.
There is a chance that it will work again with the new 1 kV cap. AFAIK it is a switcher (you know that wonderful invention we all benefit from in audio 🙂) and finding errors in these is both tedious and time intensive. Without schematics one needs experience and maybe just maybe in this case simple replacements if you are lucky. That is gambling but it sometimes works.
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Indeed. I will make these measurments once I am able to get the amplifier to operate again. As mentioned, it is currently producing no output so I am not able to create an 'under load' test. My assertion is, so far, simply that the zener based supplies are behaving as expected and that the resistors are not damaged to the point where they represent too low a resistance and get hot at idle.
I will not be able to make any judgements beyond this until I am able to get the amplifier running again.
I'm afraid I don't follow your statement below. If you could elaborate, I'd be grateful.
BTW "The resistors do indeed form part of a +/-18V with a pair of zeners (supply directly dropped from +/-150V)." is just crazy. Dividing in 2 resistors will have thermal benefits.
If you have 1 resistor 20 kOhm 2W becoming hot you may use 2 resistors 10 kOhm 2W in series and divide heat over twice the surface. Example. No difference in total heat but divided. As the resistors look to have been quite hot their reliability becomes questionable. Also 150V or thereabouts over just 1 resistor maybe is not the best of ideas. With 2 x 10 kOhm so 75V over each resistor that is also improved.
True but only if you measured the resistors values and the +/- 18V. After the new 1 nF cap you should do a heat run just in case. It would not surprise me as bug hunter that it is thermally eh... "less optimal" designed.
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I'm having a difficult time finding an equivalent 1nF cap (X1/Y1) that I can actually buy.
Looking again at the cap I am replacing (attached) I have a few questions:
1. What does the 'K' in 102K refer to?
2. Does the B1KV marking refer to DC or AC voltage?
3. @jean-paul, what was it that led you to conclude that this is a safety X1/Y1 capacitor? It makes sense given the location of the cap (may be a feedback, input to output, cap). Not doubting your assesment, just trying to understand.
Cheers
Looking again at the cap I am replacing (attached) I have a few questions:
1. What does the 'K' in 102K refer to?
2. Does the B1KV marking refer to DC or AC voltage?
3. @jean-paul, what was it that led you to conclude that this is a safety X1/Y1 capacitor? It makes sense given the location of the cap (may be a feedback, input to output, cap). Not doubting your assesment, just trying to understand.
Cheers
In a hurry right now but experience and that it is used in a mains voltage connected SMPS. Often but not always these ceramic disc “safety caps” used directly on mains voltage or high DC situations are blue and quite high in voltage rating. Checking the service manual brings certainty. Please read up on X and Y capacitors as I too have a life 🙂
That it is cracked means a quality “safety” one seems mandatory. Yes 10% tolerance.
That it is cracked means a quality “safety” one seems mandatory. Yes 10% tolerance.
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Yes, checked it and monitored its behaviour in operation. It is doing what I expect.
I was able to find an appropriate voltage rated cap at work to effect a temporary repair (just to check whether it would make a difference).
Dissapointingly, it made no difference 🙁
I also checked the value of the damaged cap that I removed. Much to my surpise, despite the crack, it still measured close to spec at about 800pF.
I took the time to reflow pretty much every connection on the power board which has also made no difference.
I'll need to have another think about this......
Dissapointingly, it made no difference 🙁
I also checked the value of the damaged cap that I removed. Much to my surpise, despite the crack, it still measured close to spec at about 800pF.
I took the time to reflow pretty much every connection on the power board which has also made no difference.
I'll need to have another think about this......
Not really, maybe explain 106K, is it 1 uF or 10 uF and 101 is it 10 pF or 100pF
For interest sake, three orders of magnitude is 30 dB not 6 dB, if you meant three times it is 9.5 dB maybe it is just different schools we came from other than that the numbers are actually identical an only used for interpretation, like it is a lot more or a lot less. 6dB is not so much more, that simplifies everything
For interest sake, three orders of magnitude is 30 dB not 6 dB, if you meant three times it is 9.5 dB maybe it is just different schools we came from other than that the numbers are actually identical an only used for interpretation, like it is a lot more or a lot less. 6dB is not so much more, that simplifies everything
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Is it test day in DIYAudio world 🙂
106K, is it 1 uF or 10 uF/10%
101 is it 10 pF or 100pF
Once upon a time, I worked at HP designing pcbs and have some test old gear too. So far so good on the Kemet tants they used alot of.
My Amber 3500 has those blue ITT tants that have failed a few times. One was in the PS, buried in the PS shielded can = PITA
Bigger problem is fixing a amp that's complicated and no schematics or understanding of how the technology works.
I tell you its a challege, maybe you will get lucky. of the SMPS that I have fixed its usually the ecap in the AC input rectifier or switching MOSFETs in the converter but it can be anything in this case because you do not know if its PS related or not. But with anything, check out the PS for DC and AC noise as a start and then go from there.
This is an AC cap that I have used
72-VY2472M49Y5US6TV0
4700 pF 20 %
Voltage Rating AC: 440 VAC, 300 VAC
Voltage Rating DC: 1 kVDC
Safety Rating: X1, Y2
EIA Temp Co: Y5U
Good Luck
106K, is it 1 uF or 10 uF/10%
101 is it 10 pF or 100pF
Once upon a time, I worked at HP designing pcbs and have some test old gear too. So far so good on the Kemet tants they used alot of.
My Amber 3500 has those blue ITT tants that have failed a few times. One was in the PS, buried in the PS shielded can = PITA
Bigger problem is fixing a amp that's complicated and no schematics or understanding of how the technology works.
I tell you its a challege, maybe you will get lucky. of the SMPS that I have fixed its usually the ecap in the AC input rectifier or switching MOSFETs in the converter but it can be anything in this case because you do not know if its PS related or not. But with anything, check out the PS for DC and AC noise as a start and then go from there.
This is an AC cap that I have used
72-VY2472M49Y5US6TV0
4700 pF 20 %
Voltage Rating AC: 440 VAC, 300 VAC
Voltage Rating DC: 1 kVDC
Safety Rating: X1, Y2
EIA Temp Co: Y5U
Good Luck
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In a bit of luck(?), I finally tracked down some more info on the amp. Schematics(!) and a quite a useful discussion here:
https://www.eevblog.com/forum/repai...dio-amplifier-(velodyne-active-subwoofer)/25/
Looks like Velodyne just kept reusing this amp design across all their subs. So, the schematics will be representative as will the many identified issues with the design 🙂
It's interesting to note that they have re-released this sub with a simpler class AB amp.
I'm starting to think I just blank the rear amp panel on the sub and drive it with a Fosi M03 external amp instead ~£50 for the Fosi amp. My time has to be worth more than that....
https://www.eevblog.com/forum/repai...dio-amplifier-(velodyne-active-subwoofer)/25/
Looks like Velodyne just kept reusing this amp design across all their subs. So, the schematics will be representative as will the many identified issues with the design 🙂
It's interesting to note that they have re-released this sub with a simpler class AB amp.
I'm starting to think I just blank the rear amp panel on the sub and drive it with a Fosi M03 external amp instead ~£50 for the Fosi amp. My time has to be worth more than that....
rcavas,
When were you at HP. I was at Signal Analysis Division at SANTA ROSA between 1975- 79.
Ever saw this amp by Barnie.
When were you at HP. I was at Signal Analysis Division at SANTA ROSA between 1975- 79.
Ever saw this amp by Barnie.
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