L
legg
Guest
When you've got this thing plugged in and running, what is visible in
the display? Can you get a locator dot? Traces in free-run?
RL
the display? Can you get a locator dot? Traces in free-run?
RL
C
Cursitor Doom
Guest
On Sun, 06 Mar 2016 19:27:19 -0500, legg wrote:
[...]
I am happy to assure you that I have not touched a single trimmer so far
and neither will I be dismissing the heating of the power resistor, which
is clearly indicating that something is still amiss here.
[...]
I am happy to assure you that I have not touched a single trimmer so far
and neither will I be dismissing the heating of the power resistor, which
is clearly indicating that something is still amiss here.
D
Dimitrij Klingbeil
Guest
On 06.03.2016 14:35, Cursitor Doom wrote:
Okay, that makes the difference somewhat less. Still higher than 17.35
kHz obviously.
If I understood the service manual correctly, they seem to suggest to
start from the lowest frequency when performing an adjustment and going
up until output regulation is reached. (They write from "fully
counter-clockwise" actually, referring to the "FREQ" trimmer, and
looking at the schematic that would likely be from the "lowest" position
of the wiper, meaning starting at the highest resistance and going
towards lower resistance.)
It's only my guess, but I think that they intended this supply to run
rather somewhere below resonance than somewhere above. This would mean
that adjusting the pulse frequency down to 17.35 kHz should do no harm
as that value would be lower than the setting right now.
If there was any danger of something blowing up by setting the frequency
lower, they would not be recommending to set it to the absolute minimum
before slowly adjusting it back "up" again.
Can you adjust the pulse rate to 17.35 kHz and then test the supply with
a dummy load?
Can you test it with a variac and see if it still maintains output in
regulation down to 175 V "mains" (adjusted to 17.35 kHz, that is)?
Regards
Dimitrij
Okay, that makes the difference somewhat less. Still higher than 17.35
kHz obviously.
If I understood the service manual correctly, they seem to suggest to
start from the lowest frequency when performing an adjustment and going
up until output regulation is reached. (They write from "fully
counter-clockwise" actually, referring to the "FREQ" trimmer, and
looking at the schematic that would likely be from the "lowest" position
of the wiper, meaning starting at the highest resistance and going
towards lower resistance.)
It's only my guess, but I think that they intended this supply to run
rather somewhere below resonance than somewhere above. This would mean
that adjusting the pulse frequency down to 17.35 kHz should do no harm
as that value would be lower than the setting right now.
If there was any danger of something blowing up by setting the frequency
lower, they would not be recommending to set it to the absolute minimum
before slowly adjusting it back "up" again.
Can you adjust the pulse rate to 17.35 kHz and then test the supply with
a dummy load?
Can you test it with a variac and see if it still maintains output in
regulation down to 175 V "mains" (adjusted to 17.35 kHz, that is)?
Regards
Dimitrij
L
legg
Guest
On Sun, 6 Mar 2016 21:18:58 -0000 (UTC), Cursitor Doom
<curd@notformail.com> wrote:
As long as you haven't been fooling with psu trimpots, you can forget
about the resistor.
If you have been fooling with trim pots, then you'll have to follow
the manual adjustment procedure first...assuming similarity to PM3262.
(check pot rotation effects expected between models).
Forget about the resistor while you're doing this.
Continue to forget about this resistor until (and if ever) V1811 dies
again.
RL
<curd@notformail.com> wrote:
As long as you haven't been fooling with psu trimpots, you can forget
about the resistor.
If you have been fooling with trim pots, then you'll have to follow
the manual adjustment procedure first...assuming similarity to PM3262.
(check pot rotation effects expected between models).
Forget about the resistor while you're doing this.
Continue to forget about this resistor until (and if ever) V1811 dies
again.
RL
C
Cursitor Doom
Guest
On Sun, 06 Mar 2016 23:34:55 +0100, Dimitrij Klingbeil wrote:
I've just noticed that towards the bottom of (true) page 106, it states
the following:-
"The oscillator frequency is approximately 25kHz, determined by network
C1811, R1823 and is adjustable by means of R1824."
It then goes on to specify the duty cycle. Two things stand out as
requiring further investigation here. Clearly, the 25kHz clock frequency
mentioned is *miles* away from what my clock is running at - and the
frequency adjustment is made with R1827, not R1824 (which is fixed
anyway). I'm guessing the reference to R1824 is just a typo, but can we
say the same for 25kHz??
Since this *completely* changes our former assumptions, I'm going to
confine myself to just replacing the flaky polyester caps for the time
being. Be interested to hear how you think I should proceed now in the
light of this...
I've just noticed that towards the bottom of (true) page 106, it states
the following:-
"The oscillator frequency is approximately 25kHz, determined by network
C1811, R1823 and is adjustable by means of R1824."
It then goes on to specify the duty cycle. Two things stand out as
requiring further investigation here. Clearly, the 25kHz clock frequency
mentioned is *miles* away from what my clock is running at - and the
frequency adjustment is made with R1827, not R1824 (which is fixed
anyway). I'm guessing the reference to R1824 is just a typo, but can we
say the same for 25kHz??
Since this *completely* changes our former assumptions, I'm going to
confine myself to just replacing the flaky polyester caps for the time
being. Be interested to hear how you think I should proceed now in the
light of this...
C
Cursitor Doom
Guest
And before anyone suggests it: I've frequency swept the primary circuit
just in case there's a second resonance peak at around 25kHz and there
isn't one.
just in case there's a second resonance peak at around 25kHz and there
isn't one.
C
Cursitor Doom
Guest
On Mon, 07 Mar 2016 14:23:22 -0500, legg wrote:
OMG you're right. I've had this issue before when looking at manuals
from .pdf files on a screen rather than hard-copy. Well that's just dandy
I must say. Now I'm *really* confused.
Once again I'm really tempted to just scrap this thing as it stands,
salvage the transformer and start afresh in a year's time with a
conventional non-resonant PWM design using a MOSFET instead of a BJT and
a more up-to-date controller.
OMG you're right. I've had this issue before when looking at manuals
from .pdf files on a screen rather than hard-copy. Well that's just dandy
I must say. Now I'm *really* confused.
Once again I'm really tempted to just scrap this thing as it stands,
salvage the transformer and start afresh in a year's time with a
conventional non-resonant PWM design using a MOSFET instead of a BJT and
a more up-to-date controller.
C
Cursitor Doom
Guest
On Mon, 07 Mar 2016 21:55:56 +0100, Dimitrij Klingbeil wrote:
Sorry, Dimitrij; as you were. Legg has spotted I was mistakenly referring
to the wrong diagram in fact. They look very similar and when you don't
have the physical hard copy manual in front of you then errors like this
are far more easily made, I regret to say.
Sigh. I've had enough for today, I'll take yet another look at it again
tomorrow.
Sorry, Dimitrij; as you were. Legg has spotted I was mistakenly referring
to the wrong diagram in fact. They look very similar and when you don't
have the physical hard copy manual in front of you then errors like this
are far more easily made, I regret to say.
Sigh. I've had enough for today, I'll take yet another look at it again
tomorrow.
D
Dimitrij Klingbeil
Guest
On 07.03.2016 19:08, Cursitor Doom wrote:
Hi
News indeed. Something must be amiss, and quite heavily amiss, that's
for sure.
It looks like the resonant circuit considerably out of tune.
Driving a 17 kHz LC with 25 kHz would not make sense to me, and it looks
like the circuit does not like it too much either, since it overheats.
If it was indeed tuned for 25 kHz, then the currently set 22 (or 20) kHz
pulse rate setting could at least make some sense. It would be slightly
below resonance, but probably not too far away.
I was assuming that the resonant circuit was ok-ish and the frequency
somewhat matched, but this turns out, now, not to be the case.
Now I've looked in the TDA1060 controller datasheet again, and checked
the adjustment range (with the trimpot set from 0 to 10 kOhm and the 11
kOhm fixed resistor and 3.3 nF timing capacitor) and the calculated
resulting range of frequencies happens to be from 17.3 kHz to 33 kHz.
With a 17.3 to 33 kHz range, that would put 25 kHz quite well in the
middle. A 17 kHz resonance frequency does not fit anywhere though. It
can't even reliably be adjusted (even if it were correct, which it
surely isn't) because it's simply out of the trimpot's range.
But it would not make any sense to pulse a 17 kHz LC at 25 kHz either.
The LC will be heavily capacitive, the power factor will be down in the
ditch, and that will overload (-heat) the driver (just as it happens).
Therefore I can only think that 17 kHz is wrong. The LC is out of
resonance. If it were OK, it should never have a 17 kHz SRF.
That leaves either a measurement error (now rather less likely) or a
heavy stray capacitance somewhere, that brings the resonance down.
I can only think of C1806 and C1807. They are in series. If one of them
has an isolation problem, that would leave the other one alone in the
circuit - and therefore double the capacitance.
Also there are the resistors in parallel - R1817 and R1818. They should
be 10 Megaohm. But if one of them is either shorted or improperly
replaced (maybe it formed an isolation breakdown from over-voltage or
someone put in a wrong value like zero Ohm instead), then that would
also short out the corresponding capacitor, and have the same effect.
Usually resistors are reliable, but sometimes, some old ones of the
"carbon composition" variety, do form a "hot channel" and break down.
Doubling the capacitance would almost halve the resonance frequency.
Actually it won't *exactly* halve it, because there is still a third
capacitor in parallel, namely the stray winding capacitance.
This looks quite enough to be realistic. If one resonance cap is shot,
the LC frequency will go down by a great deal, and (assuming it was
initially slightly higher than the pulse frequency), a change from some
25 or 27 kHz to the 17 kHz that you are now seeing, could happen.
It could also explain the overload on the resistor - a heavily
capacitive out-of-resonance load would easily do that.
Can you get these two caps out altogether, connect a known good 15 nF
(or two of 30 nF in series) instead and sweep again?
Also, to avoid unforeseen measurement errors, can you do that out of
circuit? Just the transformer and the capacitor(s) on the primary. This
would also nicely avoid the resistors too, they too may be questionable.
You won't need a high voltage cap for sweeping - any good 15 nF one will
do. But don't power it up with "any 15 nF". To run at full power it
needs something like a FKP1 or MKP-4C with proper ratings (see my
earlier post, there are some suggested models that can work there).
Regards
Dimitrij
Hi
News indeed. Something must be amiss, and quite heavily amiss, that's
for sure.
It looks like the resonant circuit considerably out of tune.
Driving a 17 kHz LC with 25 kHz would not make sense to me, and it looks
like the circuit does not like it too much either, since it overheats.
If it was indeed tuned for 25 kHz, then the currently set 22 (or 20) kHz
pulse rate setting could at least make some sense. It would be slightly
below resonance, but probably not too far away.
I was assuming that the resonant circuit was ok-ish and the frequency
somewhat matched, but this turns out, now, not to be the case.
Now I've looked in the TDA1060 controller datasheet again, and checked
the adjustment range (with the trimpot set from 0 to 10 kOhm and the 11
kOhm fixed resistor and 3.3 nF timing capacitor) and the calculated
resulting range of frequencies happens to be from 17.3 kHz to 33 kHz.
With a 17.3 to 33 kHz range, that would put 25 kHz quite well in the
middle. A 17 kHz resonance frequency does not fit anywhere though. It
can't even reliably be adjusted (even if it were correct, which it
surely isn't) because it's simply out of the trimpot's range.
But it would not make any sense to pulse a 17 kHz LC at 25 kHz either.
The LC will be heavily capacitive, the power factor will be down in the
ditch, and that will overload (-heat) the driver (just as it happens).
Therefore I can only think that 17 kHz is wrong. The LC is out of
resonance. If it were OK, it should never have a 17 kHz SRF.
That leaves either a measurement error (now rather less likely) or a
heavy stray capacitance somewhere, that brings the resonance down.
I can only think of C1806 and C1807. They are in series. If one of them
has an isolation problem, that would leave the other one alone in the
circuit - and therefore double the capacitance.
Also there are the resistors in parallel - R1817 and R1818. They should
be 10 Megaohm. But if one of them is either shorted or improperly
replaced (maybe it formed an isolation breakdown from over-voltage or
someone put in a wrong value like zero Ohm instead), then that would
also short out the corresponding capacitor, and have the same effect.
Usually resistors are reliable, but sometimes, some old ones of the
"carbon composition" variety, do form a "hot channel" and break down.
Doubling the capacitance would almost halve the resonance frequency.
Actually it won't *exactly* halve it, because there is still a third
capacitor in parallel, namely the stray winding capacitance.
This looks quite enough to be realistic. If one resonance cap is shot,
the LC frequency will go down by a great deal, and (assuming it was
initially slightly higher than the pulse frequency), a change from some
25 or 27 kHz to the 17 kHz that you are now seeing, could happen.
It could also explain the overload on the resistor - a heavily
capacitive out-of-resonance load would easily do that.
Can you get these two caps out altogether, connect a known good 15 nF
(or two of 30 nF in series) instead and sweep again?
Also, to avoid unforeseen measurement errors, can you do that out of
circuit? Just the transformer and the capacitor(s) on the primary. This
would also nicely avoid the resistors too, they too may be questionable.
You won't need a high voltage cap for sweeping - any good 15 nF one will
do. But don't power it up with "any 15 nF". To run at full power it
needs something like a FKP1 or MKP-4C with proper ratings (see my
earlier post, there are some suggested models that can work there).
Regards
Dimitrij
L
legg
Guest
On Mon, 7 Mar 2016 13:46:27 -0000 (UTC), Cursitor Doom
<curd@notformail.com> wrote:
You are refering to manual component numbers from the 3262 manual and
schematic. The 3264 does not have the same schematic or part numbers.
The schematic is functionally similar, but uses a different control IC
and different components are present/selected to set the IC's
function. Part type for the main transformer/size and pinout, the size
of resonant/snubbing components, along the actual supply power
ratings may vary with model number, as well. One example is the
different resonant cap size used.
3262 PSU adjustment begins with para 3.4.4 on 3262 manual page 115.
(do not ignore preceding setup instructions re scope settings)
You can assume the sequencing and intention of these instructions to
mirror those needed for 3264, however numbers and test conditions that
reflect operating power and typical frequency can be expected to vary.
This includes chip reference pin voltages - TDA1060 internal reference
is 3V62.
The converter runs at a fixed frequency, above resonance. The
frequency only needs adjustment if the output voltages lose full power
low-line voltage regulation. This is also the protective power limit.
The two model control circuits do not limit in a similar manner. The
3262 manual describes a latching power limit that occurs after
repeated continuous overload. This does not appear to be present in in
3264, as it is chip-based feature.
RL
<curd@notformail.com> wrote:
You are refering to manual component numbers from the 3262 manual and
schematic. The 3264 does not have the same schematic or part numbers.
The schematic is functionally similar, but uses a different control IC
and different components are present/selected to set the IC's
function. Part type for the main transformer/size and pinout, the size
of resonant/snubbing components, along the actual supply power
ratings may vary with model number, as well. One example is the
different resonant cap size used.
3262 PSU adjustment begins with para 3.4.4 on 3262 manual page 115.
(do not ignore preceding setup instructions re scope settings)
You can assume the sequencing and intention of these instructions to
mirror those needed for 3264, however numbers and test conditions that
reflect operating power and typical frequency can be expected to vary.
This includes chip reference pin voltages - TDA1060 internal reference
is 3V62.
The converter runs at a fixed frequency, above resonance. The
frequency only needs adjustment if the output voltages lose full power
low-line voltage regulation. This is also the protective power limit.
The two model control circuits do not limit in a similar manner. The
3262 manual describes a latching power limit that occurs after
repeated continuous overload. This does not appear to be present in in
3264, as it is chip-based feature.
RL
D
Dimitrij Klingbeil
Guest
On 07.03.2016 20:21, Dimitrij Klingbeil wrote:
P.S. There may be another failure mode that I did not consider right
away, that can make it a little harder for you to test the caps.
These high voltage impulse-rated capacitors are usually made with three
metal layers and two layers of isolation internally. Mains "X1" and "X2"
rated capacitors are also made in this way. They are like two capacitors
that are connected in series inside. When one isolator breaks down,
the whole capacitor won't be destroyed catastrophically because there's
still the other internal half in series.
But it can happen (depending on the construction of the capacitor, if it
has a continuous metal layer between the isolators) that the capacitance
will "double itself" instead.
If one of your 30 nF caps has failed in this way, it will "become 60 nF"
instead of becoming short-circuit. So you won't see it on an Ohmmeter.
But that would also be reason enough to detune the resonance a lot.
So, my advice would be, do not trust them, and do not trust their
parallel resistors too much either. Take a known working 15 nF cap and
sweep the transformer with it. If you get anything significantly above
17 kHz with a new cap, look for the main problem in this direction.
Dimitrij
P.S. There may be another failure mode that I did not consider right
away, that can make it a little harder for you to test the caps.
These high voltage impulse-rated capacitors are usually made with three
metal layers and two layers of isolation internally. Mains "X1" and "X2"
rated capacitors are also made in this way. They are like two capacitors
that are connected in series inside. When one isolator breaks down,
the whole capacitor won't be destroyed catastrophically because there's
still the other internal half in series.
But it can happen (depending on the construction of the capacitor, if it
has a continuous metal layer between the isolators) that the capacitance
will "double itself" instead.
If one of your 30 nF caps has failed in this way, it will "become 60 nF"
instead of becoming short-circuit. So you won't see it on an Ohmmeter.
But that would also be reason enough to detune the resonance a lot.
So, my advice would be, do not trust them, and do not trust their
parallel resistors too much either. Take a known working 15 nF cap and
sweep the transformer with it. If you get anything significantly above
17 kHz with a new cap, look for the main problem in this direction.
Dimitrij
D
Dimitrij Klingbeil
Guest
On 07.03.2016 20:21, Dimitrij Klingbeil wrote:
P.P.S. If you decide to sweep the LC part in circuit instead of out of
circuit (because the transformer is difficult to solder out etc...), you
can use a small voltage source (a 9 V block battery) connected to the
power supply's "AC" input. This will precharge the circuit enough to get
the parasitics down. It won't start the power supply controller, but it
will reverse-bias various diodes and also the base-collector junction of
the main switching transistor. That will make these semiconductor parts
non-conducting (at small signal levels) and prevent them from rectifying
the test signal from your sweep generator, and messing it up in various
ways through leakage paths. It's an easier alternative to removing the
switching transistor from the circuit.
Dimitrij
P.P.S. If you decide to sweep the LC part in circuit instead of out of
circuit (because the transformer is difficult to solder out etc...), you
can use a small voltage source (a 9 V block battery) connected to the
power supply's "AC" input. This will precharge the circuit enough to get
the parasitics down. It won't start the power supply controller, but it
will reverse-bias various diodes and also the base-collector junction of
the main switching transistor. That will make these semiconductor parts
non-conducting (at small signal levels) and prevent them from rectifying
the test signal from your sweep generator, and messing it up in various
ways through leakage paths. It's an easier alternative to removing the
switching transistor from the circuit.
Dimitrij
C
Cursitor Doom
Guest
Well, I've replaced all the flaking capacitors and still no improvement.
A number of people have been suggesting I remove the two resonant caps
(the 30n ones) from the primary circuit and test them. I didn't have any
expectation that this would achieve anything since they tested good in-
circuit, but as we're running out of ideas now I did remove them this
afternoon and they both tested at 31nF a piece and no signs of any
physical damage. I then subbed a couple of common-or-garden mylars of the
same value in their places and re-swept for changes in resonance. Result
was no change in resonance - but a slightly better Q(!!) Also checked the
two 10Meg resistors whilst I was at it and they were fine, too. So I can
only think of making up Dimitrij's winding tester and looking for signs
of any turns shorting in the main transformer.
I'm coming to the end of the amount of time I'm prepared to spend on this
psu as it stands. I'm more and more tempted to mothball the key parts of
it til next year then rebuild it as a conventional non-res converter to a
fresh design. TBH, I'm not prepared to still be testing this thing after
the end of this week, so if anyone has any last-ditch ideas, now's the
time to toss 'em into the mix. Speak now or forever hold your peace.
Thanks, all.
A number of people have been suggesting I remove the two resonant caps
(the 30n ones) from the primary circuit and test them. I didn't have any
expectation that this would achieve anything since they tested good in-
circuit, but as we're running out of ideas now I did remove them this
afternoon and they both tested at 31nF a piece and no signs of any
physical damage. I then subbed a couple of common-or-garden mylars of the
same value in their places and re-swept for changes in resonance. Result
was no change in resonance - but a slightly better Q(!!) Also checked the
two 10Meg resistors whilst I was at it and they were fine, too. So I can
only think of making up Dimitrij's winding tester and looking for signs
of any turns shorting in the main transformer.
I'm coming to the end of the amount of time I'm prepared to spend on this
psu as it stands. I'm more and more tempted to mothball the key parts of
it til next year then rebuild it as a conventional non-res converter to a
fresh design. TBH, I'm not prepared to still be testing this thing after
the end of this week, so if anyone has any last-ditch ideas, now's the
time to toss 'em into the mix. Speak now or forever hold your peace.
Thanks, all.
C
Cursitor Doom
Guest
On Tue, 08 Mar 2016 12:35:07 -0500, JC wrote:
Yes, they're fine. It's not *my* opinion that this is a poor design! I
posted the schematic to s.e.d and the designers there told me that. I've
said all along I know nothing about this type of PSU so I defer to those
better qualified. Having said that, the widespread evidence of charring
and soot residue that appear even worse in real life than in the photos
would seem to indicated that that is not a happy board. The rest of the
scope's boards are still pristine showing no sign of repairs at all.
Nothing obvious about it! - apart from the rather poor replacement
technique. The problem with that replacement was very subtle inasmuch as
it wasn't recovering quickly enough at 20kHz. Nevertheless it was still
capable of functioning as a viable rectifier right up to 500kHz.
All the recent tests have been carried out using the actual scope itself
as a load - can't get any better than that. I won't put it in the scope
until that resistor is running cool. It's proximity to other temperature
sensitive components like diodes and its siting deep within the scope
uncooled lead me to believe that it is running far hotter than it should
be - and will be even worse in situ. That *might* just be a design flaw,
but I doubt it.
Yes, they're fine. It's not *my* opinion that this is a poor design! I
posted the schematic to s.e.d and the designers there told me that. I've
said all along I know nothing about this type of PSU so I defer to those
better qualified. Having said that, the widespread evidence of charring
and soot residue that appear even worse in real life than in the photos
would seem to indicated that that is not a happy board. The rest of the
scope's boards are still pristine showing no sign of repairs at all.
Nothing obvious about it! - apart from the rather poor replacement
technique. The problem with that replacement was very subtle inasmuch as
it wasn't recovering quickly enough at 20kHz. Nevertheless it was still
capable of functioning as a viable rectifier right up to 500kHz.
All the recent tests have been carried out using the actual scope itself
as a load - can't get any better than that. I won't put it in the scope
until that resistor is running cool. It's proximity to other temperature
sensitive components like diodes and its siting deep within the scope
uncooled lead me to believe that it is running far hotter than it should
be - and will be even worse in situ. That *might* just be a design flaw,
but I doubt it.
C
Cursitor Doom
Guest
On Tue, 08 Mar 2016 12:33:50 -0500, legg wrote:
Yeah, I know what you're thinking - your suggestion still hasn't been
adopted. I've been giving it more thought and I've come up with a
brainwave.
This is a 2W resistor. If it's trying to dissipate more than 2W as I
strongly believe, something's definitely wrong. The problem up until now
has been measuring the dissipation, because we can't use I^2*R or
variations thereof because of the highly noisy/irregular waveform. So...
Here's the clever bit:
Measure exactly how long it takes at present for the resistor to reach
say 50'C. I believe it's around 1 minute, but get the exact time. Then
let it cool completely back to the room ambient temperature. Remove from
circuit. Attach to bench power supply and by means of trial and error,
set the voltage across the resistor to raise it's temperature to 50'C in
1 minute (will obviously require several attempts, but no matter). Read
off the voltage level which produces this outcome, then just do V^2/R to
find W and see if it exceeds 2W.
I'll do it first thing tomorrow!
Yeah, I know what you're thinking - your suggestion still hasn't been
adopted. I've been giving it more thought and I've come up with a
brainwave.
This is a 2W resistor. If it's trying to dissipate more than 2W as I
strongly believe, something's definitely wrong. The problem up until now
has been measuring the dissipation, because we can't use I^2*R or
variations thereof because of the highly noisy/irregular waveform. So...
Here's the clever bit:
Measure exactly how long it takes at present for the resistor to reach
say 50'C. I believe it's around 1 minute, but get the exact time. Then
let it cool completely back to the room ambient temperature. Remove from
circuit. Attach to bench power supply and by means of trial and error,
set the voltage across the resistor to raise it's temperature to 50'C in
1 minute (will obviously require several attempts, but no matter). Read
off the voltage level which produces this outcome, then just do V^2/R to
find W and see if it exceeds 2W.
I'll do it first thing tomorrow!
J
Julian Barnes
Guest
On Tue, 08 Mar 2016 21:31:25 +0000, Cursitor Doom wrote:
[snip]
> I'll do it first thing tomorrow!
Finally it gets *really* interesting. >:-}
[snip]
> I'll do it first thing tomorrow!
Finally it gets *really* interesting. >:-}
L
legg
Guest
On Tue, 8 Mar 2016 16:48:05 -0000 (UTC), Cursitor Doom
<curd@notformail.com> wrote:
Waste of breath.
RL
<curd@notformail.com> wrote:
Waste of breath.
RL
J
JC
Guest
On 3/8/2016 11:48 AM, Cursitor Doom wrote:
I have no idea what you now consider to be wrong with the PSU. Apart
from a resistor that in your opinion runs too hot even though its well
within its rating I seem to recall amidst your ramblings that the
voltage rails are correct?
It seems to me that the only fault was the diode which was pretty
obvious from the beginning. (Always check for previous repairs).
You persist in not using the correct manual, refuse to test it with an
appropriate load and won't put it in the scope to see if the scope
actually functions.
If you just want to discuss switching supply design go buy some control
chips or an evaluation kit and build some.
I have no idea what you now consider to be wrong with the PSU. Apart
from a resistor that in your opinion runs too hot even though its well
within its rating I seem to recall amidst your ramblings that the
voltage rails are correct?
It seems to me that the only fault was the diode which was pretty
obvious from the beginning. (Always check for previous repairs).
You persist in not using the correct manual, refuse to test it with an
appropriate load and won't put it in the scope to see if the scope
actually functions.
If you just want to discuss switching supply design go buy some control
chips or an evaluation kit and build some.
J
Jeroni Paul
Guest
Cursitor Doom wrote:
Good test. It would be more straight to plug the right voltage to make it dissipate 2W, for 20 ohm that would be 6,3V and check what temp results in 1 minute. You could use another identical resistor for the test if you have one lying around to avoid unsoldering.
Good test. It would be more straight to plug the right voltage to make it dissipate 2W, for 20 ohm that would be 6,3V and check what temp results in 1 minute. You could use another identical resistor for the test if you have one lying around to avoid unsoldering.
C
Cursitor Doom
Guest
On Wed, 09 Mar 2016 00:20:35 +0100, Dimitrij Klingbeil wrote:
Thanks for the tips, guys, they will both save me time. I'll work out the
appropriate voltages for 3, 4 & 5W too and that'll save even more time.
Thanks for the tips, guys, they will both save me time. I'll work out the
appropriate voltages for 3, 4 & 5W too and that'll save even more time.