6 Jan
2022
6 Jan
'22
12:52 a.m.
I think I may need to replace the two output capacitors in some of my H744
regulators. These are screw terminal 6,000uF 10V parts. I have looked on
Mouser, Farnell and Digikey and there don't seem to be any available, and
any that are listed are really rather costly.
Does anyone know where I might find some, preferably from a reputable
supplier. Note that I am in the UK.
If I can't find 10V rated ones, then, generally up to what sort of voltage
rating can I go? Of course, physical size will be a factor, but electrically
can it affect operation of the regulator if the rated voltage is too high?
Thanks
Rob
6 Jan
6 Jan
1:59 a.m.
On 06/01/2022 08:52, Rob Jarratt via cctalk wrote:
I think I may need to replace the two output
capacitors in some of my H744
regulators. These are screw terminal 6,000uF 10V parts. I have looked on
Mouser, Farnell and Digikey and there don't seem to be any available, and
any that are listed are really rather costly.
I think I used Mouser part number80-PEH169HA460AQU2 to replace mine. I
was also considering RS part number 381-9093 as an alternative though
the voltage rating is quite a bit higher.
Regards,
Matt
2:02 a.m.
On Thu, 6 Jan 2022, rob at jarratt.me.uk wrote:
If I can't find 10V rated ones, then, generally up
to what sort of voltage
rating can I go? Of course, physical size will be a factor, but electrically
can it affect operation of the regulator if the rated voltage is too high?
If you need to ask this, are you sure you want to do electronics repair?
And what makes you think that you need to replace these caps at all?
Christian
3:40 a.m.
-----Original Message-----
From: cctalk <cctalk-bounces at classiccmp.org> On Behalf Of Christian Corti
via cctalk
Sent: 06 January 2022 10:02
To: General Discussion: On-Topic and Off-Topic Posts
<cctalk at classiccmp.org>
Subject: Re: Source for replacement caps in H744 regulators
On Thu, 6 Jan 2022, rob at jarratt.me.uk wrote:
> If I can't find 10V rated ones, then, generally up to what sort of
> voltage rating can I go? Of course, physical size will be a factor,
> but electrically can it affect operation of the regulator if the rated
voltage
is
too high?
If you need to ask this, are you sure you want to do electronics repair?
I am gradually learning.
And what makes you think that you need to replace
these caps at all?
One of the H744 regulators whines and I have been told it could be the ESR
on these caps. I have measured the ESR on these particular ones (out of
circuit) and it seems higher than the expected values printed on the meter
and also the ESR is not stable, it fluctuates randomly. This suggests the
cap is not in great condition.
Christian
4:15 a.m.
-----Original Message-----
From: cctalk <cctalk-bounces at classiccmp.org> On Behalf Of Christian Corti
via cctalk
Sent: 06 January 2022 10:02
To: General Discussion: On-Topic and Off-Topic Posts
<cctalk at classiccmp.org>
Subject: Re: Source for replacement caps in H744 regulators
On Thu, 6 Jan 2022, rob at jarratt.me.uk wrote:
> If I can't find 10V rated ones, then, generally up to what sort of
> voltage rating can I go? Of course, physical size will be a factor,
> but electrically can it affect operation of the regulator if the rated
voltage is
too high?
If you need to ask this, are you sure you want to do electronics repair?
I am gradually learning.
And what makes you think that you need to replace
these caps at all?
One of the H744 regulators whines and I have been told it could be the ESR
on these caps. I have measured the ESR on these particular ones (out of
circuit) and it seems higher than the expected values printed on the meter
and also the ESR is not stable, it fluctuates randomly. This suggests the
cap is not in great condition.
I guess from that the large capacitance of these units, they are probably
filtering 50Hz or 100Hz ripple and high ESR is probably going to lead to
higher than normal levels of ripple on the output which could possibly
cause some inductive component somewhere to buzz or whine.
I'm not sure if it is easy to measure the ripple on the output or if
it is specified anywhere how much ripple can be tolerated before logic
errors start to become a problem.
Maybe it would be good to replace the capacitors in just the unit which
is whining to begin with and see if it makes a difference?
To address the original question, I think I read somewhere that electrolytic
capacitors that are used for voltages a lot lower than their rating may
fail to maintain their dielectric formation which may in turn result in
increased leakage.
Here's a thought. Could the whining be coming from an inductive filter
before the capactors because of excessive leakage through the capacitors
rather than because of high ESR? Would they benefit from re-forming?
Regards,
Peter Coghlan.
Christian
7:13 a.m.
-----Original Message-----
From: cctalk <cctalk-bounces at classiccmp.org> On Behalf Of Peter Coghlan
via cctalk
Sent: 06 January 2022 12:16
To: General Discussion: On-Topic and Off-Topic Posts
<cctalk at classiccmp.org>
Subject: RE: Source for replacement caps in H744 regulators
>
>> -----Original Message-----
>> From: cctalk <cctalk-bounces at classiccmp.org> On Behalf Of Christian
>> Corti via cctalk
>> Sent: 06 January 2022 10:02
>> To: General Discussion: On-Topic and Off-Topic Posts
>> <cctalk at classiccmp.org>
>> Subject: Re: Source for replacement caps in H744 regulators
>>
>> On Thu, 6 Jan 2022, rob at jarratt.me.uk wrote:
>> > If I can't find 10V rated ones, then, generally up to what sort of
>> > voltage rating can I go? Of course, physical size will be a factor,
>> > but electrically can it affect operation of the regulator if the
>> > rated
> voltage is
>> too high?
>>
>> If you need to ask this, are you sure you want to do electronics
repair?
I am gradually learning.
I'm slowly picking this sort of stuff up as I go along too.
I think that asking questions like this is the right thing to do when we sure about something and is not at all an indication
that someone is
somehow not suited to the task. Quite the reverse in fact.
If we don't do this sort of work ourselves, it's not going to be easy to
get
someone else to do it and make sure it is done well
for a
reasonable price. Any contemporary electronics repair outfit, assuming
one can be found, would probably recommend dumping the whole thing and
replacing it with a "modern" power supply.
I appreciate that there is lots of bogus advice out there which suggests
that
And what makes you think that you need to replace
these caps at all?
all capacitors need to be replaced before even
starting to investigate the
cause of problems but I think Rob has demonstrated that he is trying to
figure out what is going on rather than just blindly replacing stuff.
higher
One of the H744 regulators whines and I have been told it could be the
ESR on these caps. I have measured the ESR on these particular ones
(out of
circuit) and it seems higher than the expected values printed on the
meter and also the ESR is not stable, it fluctuates randomly. This
suggests the cap is not in great condition.
I guess from that the large capacitance of these units, they are probably
filtering 50Hz or 100Hz ripple and high ESR is probably going to lead to than normal levels of ripple on the output which could
possibly cause some
inductive component somewhere to buzz or whine.
I'm not sure if it is easy to measure the ripple on the output or if it is
specified
anywhere how much ripple can be tolerated before logic
errors start to
become a problem.
Maybe it would be good to replace the capacitors in just the unit which is
whining to begin with and see if it makes a difference?
I will try this by using the caps from other H744s that don't whine.
To address the original question, I think I read somewhere that
electrolytic
capacitors that are used for voltages a lot lower than
their rating may
fail to
maintain their dielectric formation which may in turn
result in increased
leakage.
Here's a thought. Could the whining be coming from an inductive filter
before the capactors because of excessive leakage through the capacitors
rather than because of high ESR? Would they benefit from re-forming?
I did re-form the capacitors first. They didn't seem to need much as I ran
them at 10V with zero leakage current (i.e. not measurable). Maybe I need to
run the reforming process a bit longer anyway?
Regards,
Peter Coghlan.
>
>>
>> Christian
>
4:59 a.m.
One of the H744 regulators whines
FWIW, none of mine are silent under load. If they're not being loaded (e.g. on a test
bench, with no dummy load, or if you have all the boards out) they can whine excessively
due to no minimum load.
it seems higher than the expected values printed on
the meter
Beware cheap test equipment. $client has a few of these Chinese handheld LC/RLC meters,
they're wildly inaccurate on some parameters, including ESR on large electrolytics.
We've got a proper Gen-Rad RLC Digibridge in the shop to compare against. We
couldn't figure out why some of their tuned filter stages were failing QC at a much
higher rate than expected. They were off-frequency because the cheap meters were giving
consistently incorrect measurements when trying to match capacitors.
That said, it's not like replacing them with new will *hurt* -- it just might not fix
the whine.
Thanks,
Jonathan
7:11 a.m.
-----Original Message-----
From: Jonathan Chapman <lists at glitchwrks.com>
Sent: 06 January 2022 13:00
To: rob at jarratt.me.uk; Rob Jarratt <robert.jarratt at ntlworld.com>; General
Discussion: On-Topic and Off-Topic Posts <cctalk at classiccmp.org>
Subject: RE: Source for replacement caps in H744 regulators
I was testing with a 1R resistor, so drawing 5A of the rated 25A. The other two H744s did
not whine, but this one does. I can try a bigger load, I think the best I may be able to
do is 10A, possibly 20A.
One of the H744 regulators whines
FWIW, none of mine are silent under load. If they're not being loaded (e.g.
on a test bench, with no dummy load, or if you have all the boards out) they
can whine excessively due to no minimum load. it seems higher than the expected values printed
on the meter
Beware cheap test equipment. $client has a few of these Chinese handheld
LC/RLC meters, they're wildly inaccurate on some parameters, including ESR
on large electrolytics. We've got a proper Gen-Rad RLC Digibridge in the shop
to compare against. We couldn't figure out why some of their tuned filter
stages were failing QC at a much higher rate than expected. They were off-
frequency because the cheap meters were giving consistently incorrect
measurements when trying to match capacitors.
That said, it's not like replacing them with new
will *hurt* -- it just might not
fix the whine.
Thanks,
Jonathan
4:04 p.m.
On 06/01/2022 12:59, Jonathan Chapman via cctalk wrote:
That said, it's not like replacing them with new
will *hurt* -- it just might not fix the whine.
I suspect that it won't fix the problem. Slightly hijacking the thread
here but hopefully in a semi-helpful way.
I have two of these regulators, one from a BA11K and one from a TS11.
Under the same test conditions the one from the TS11 produces a
significantly louder whining noise than the one from the BA11K. Given
that they are largely the same circuit as the H745 regulators and all
the ones I have are silent in operation I find it hard to believe they
are supposed to be like this. I used to have two more TS11 drives and
they both exhibited the same behaviour. Seems to be a common problem.
Now, for the one from the BA11K (quiet one) the output capacitors were
completely open (0uF) so I had to replace them. Given that I had the new
capacitors I decided to try them in the TS11 regulator to see if it
would fix the whining noise. It made no difference.
After some probing with an oscilloscope I found that between the two
regulators there was a very different waveform on the emitter of Q2.
Quiet regulator: http://www.9track.net/posts/h744/h744_ba11_q2e.png
Noisy regulator: http://www.9track.net/posts/h744/h744_ts11_q2e.png
The yellow trace is the emitter of Q2 (input of L1) and the cyan trace
is the output of L1. Q2 seems to be switching partly on then fully on in
the noisy regulator. it should of course be fully on or fully off as
seen on the quiet regulator. Also the switching frequency seems to be lower.
I tried testing/swapping a few parts between the two regulators, L1, Q2,
Q3, E1. It started out reasonably logical and after several days
descended into a unscientific mess of swapping anything and everything
that could possibly be at fault. I got to the point where I had
eliminated just about every component so I must have overlooked
something. I was hoping to stumble upon the answer and then learn
something from it but so far no luck. This project has been shelved for
a while now.
Regards,
Matt
5:03 p.m.
My 2c. I am not familiar with a "whine" but certainly a "hum."
Sometimes if a power supply has seen a lot of heavy load over its lifetime, the heat
generated can begin to do things to the transformer. And once that heat has done its
"thing" to the transformer, it stays that way. And no replacing external
components will change the hum. However, there are some transformers with bolts and nuts
that hold the laminations together. Sometimes they can be tightened to reduce the hum. I
don?t know this PS specifically and whether it falls into this category or not.
I don?t know if what you are hearing is transformer hum, but if it is, you may just have
to live with it.
73 Eugene W2HX
Subscribe to my Youtube Channel: https://www.youtube.com/c/w2hx-channel/videos
-----Original Message-----
From: cctalk <cctalk-bounces at classiccmp.org> On Behalf Of Matt Burke via cctalk
Sent: Thursday, January 6, 2022 7:05 PM
To: cctalk at classiccmp.org
Subject: Re: Source for replacement caps in H744 regulators
On 06/01/2022 12:59, Jonathan Chapman via cctalk wrote:
That said, it's not like replacing them with new
will *hurt* -- it just might not fix the whine.
I suspect that it won't fix the problem. Slightly hijacking the thread here but
hopefully in a semi-helpful way.
I have two of these regulators, one from a BA11K and one from a TS11.
Under the same test conditions the one from the TS11 produces a significantly louder
whining noise than the one from the BA11K. Given that they are largely the same circuit as
the H745 regulators and all the ones I have are silent in operation I find it hard to
believe they are supposed to be like this. I used to have two more TS11 drives and they
both exhibited the same behaviour. Seems to be a common problem.
Now, for the one from the BA11K (quiet one) the output capacitors were completely open
(0uF) so I had to replace them. Given that I had the new capacitors I decided to try them
in the TS11 regulator to see if it would fix the whining noise. It made no difference.
After some probing with an oscilloscope I found that between the two regulators there was
a very different waveform on the emitter of Q2.
Quiet regulator: http://www.9track.net/posts/h744/h744_ba11_q2e.png
Noisy regulator: http://www.9track.net/posts/h744/h744_ts11_q2e.png
The yellow trace is the emitter of Q2 (input of L1) and the cyan trace is the output of
L1. Q2 seems to be switching partly on then fully on in the noisy regulator. it should of
course be fully on or fully off as seen on the quiet regulator. Also the switching
frequency seems to be lower.
I tried testing/swapping a few parts between the two regulators, L1, Q2, Q3, E1. It
started out reasonably logical and after several days descended into a unscientific mess
of swapping anything and everything that could possibly be at fault. I got to the point
where I had eliminated just about every component so I must have overlooked something. I
was hoping to stumble upon the answer and then learn something from it but so far no luck.
This project has been shelved for a while now.
Regards,
Matt
7 Jan
7 Jan
8:02 a.m.
On 1/6/2022 7:03 PM, W2HX via cctalk wrote:
My 2c. I am not familiar with a "whine" but
certainly a "hum." Sometimes if a power supply has seen a lot of heavy load over
its lifetime, the heat generated can begin to do things to the transformer. And once that
heat has done its "thing" to the transformer, it stays that way. And no
replacing external components will change the hum. However, there are some transformers
with bolts and nuts that hold the laminations together. Sometimes they can be tightened to
reduce the hum. I don?t know this PS specifically and whether it falls into this category
or not.
I don?t know if what you are hearing is transformer hum, but if it is, you may just have
to live with it.
73 Eugene W2HX
Subscribe to my Youtube Channel: https://www.youtube.com/c/w2hx-channel/videos
This does not fall "into this category". This is typically high
frequency (in excess of 10KHz) whine, not 60 cycle, 120 cycle or even
400 cycle "hum".
My experience with many PDP-11 machines going back to the mid 1970s, and
those in my collection, is that this whine from the *switching* power
supplies is very common. For some people, it may be above the frequency
that they can hear. For me it is not (I could also hear burglar alarms
in excess of 20KHz back in the day, though I doubt I could now, at age 70.)
My *guess* is that it comes from the inductors in the switching circuit,
and is *mechanical*, induced by the switching waveform, which in turn is
dependent upon load. If I had one that was really bad, I'd be tempted
to put on a glove for insulation and hold those to see if the mechanical
pressure made any difference.
JRJ
12:21 p.m.
Weirdly, the whine has disappeared. This is after I put the suspect capacitors back in.
Because I had previously removed them for reforming, I wonder if one of them was not
properly screwed in?
Regards
Rob
-----Original Message-----
From: cctalk <cctalk-bounces at classiccmp.org> On Behalf Of Jay Jaeger via
cctalk
Sent: 07 January 2022 16:02
To: cctalk at classiccmp.org
Subject: Re: Source for replacement caps in H744 regulators
On 1/6/2022 7:03 PM, W2HX via cctalk wrote:
My 2c. I am not familiar with a "whine"
but certainly a "hum." Sometimes if
a power supply has seen a lot of
heavy load over its lifetime, the heat
generated can begin to do things to the transformer. And once that heat has
done its "thing" to the transformer, it stays that way. And no replacing
external components will change the hum. However, there are some
transformers with bolts and nuts that hold the laminations together.
Sometimes they can be tightened to reduce the hum. I don?t know this PS
specifically and whether it falls into this category or not.
I don?t know if what you are hearing is transformer hum, but if it is, you
may
just have to live with it.
73 Eugene W2HX
Subscribe to my Youtube Channel:
https://www.youtube.com/c/w2hx-channel/videos
This does not fall "into this category". This is typically high frequency (in
excess of 10KHz) whine, not 60 cycle, 120 cycle or even
400 cycle "hum".
My experience with many PDP-11 machines going back to the mid 1970s, and
those in my collection, is that this whine from the *switching* power
supplies is very common. For some people, it may be above the frequency
that they can hear. For me it is not (I could also hear burglar alarms in excess
of 20KHz back in the day, though I doubt I could now, at age 70.)
My *guess* is that it comes from the inductors in the switching circuit, and is
*mechanical*, induced by the switching waveform, which in turn is
dependent upon load. If I had one that was really bad, I'd be tempted to put
on a glove for insulation and hold those to see if the mechanical pressure
made any difference.
JRJ 
12:35 p.m.
I never had this problem with an H744 power regulator, but once I had a
horrible intermittent problem in the RK05 power supply where the caps
were 'wafting in the breeze' of the fan.
Metal fatigue had created almost microscopic cracks around the part of
the land where the screws attached, causing a disk fault every week or
so.? It was in? one of four drives and the only way I found it was to
swap the drives one by one and wait, since the emerg signal was paralleled!
I told the chief engineer that the problem was the same thing that
caused planes to crash, and he suggested maybe the cargo door had fallen
off!? (that puts it in 1972 since it was AA Flight 96 that had just
happened!)
Try reheating around the screws.
cheers,
Nigel
Nigel Johnson, MSc., MIEEE, MCSE VE3ID/G4AJQ/VA3MCU
Amateur Radio, the origin of the open-source concept!
Skype: TILBURY2591nw.johnson at ieee.org
On 2022-01-07 15:21, Rob Jarratt via cctalk wrote:
Weirdly, the whine has disappeared. This is after I
put the suspect capacitors back in. Because I had previously removed them for reforming, I
wonder if one of them was not properly screwed in?
Regards
Rob
> -----Original Message-----
> From: cctalk<cctalk-bounces at classiccmp.org> On Behalf Of Jay Jaeger via
> cctalk
> Sent: 07 January 2022 16:02
> To:cctalk at classiccmp.org
> Subject: Re: Source for replacement caps in H744 regulators
>
> On 1/6/2022 7:03 PM, W2HX via cctalk wrote:
>> My 2c. I am not familiar with a "whine" but certainly a
"hum." Sometimes if
> a power supply has seen a lot of heavy load over its lifetime, the heat
> generated can begin to do things to the transformer. And once that heat has
> done its "thing" to the transformer, it stays that way. And no replacing
> external components will change the hum. However, there are some
> transformers with bolts and nuts that hold the laminations together.
> Sometimes they can be tightened to reduce the hum. I don?t know this PS
> specifically and whether it falls into this category or not.
>> I don?t know if what you are hearing is transformer hum, but if it is, you
> may just have to live with it.
>> 73 Eugene W2HX
>> Subscribe to my Youtube Channel:
>> https://www.youtube.com/c/w2hx-channel/videos
> This does not fall "into this category". This is typically high frequency
(in
> excess of 10KHz) whine, not 60 cycle, 120 cycle or even
> 400 cycle "hum".
>
> My experience with many PDP-11 machines going back to the mid 1970s, and
> those in my collection, is that this whine from the *switching* power
> supplies is very common. For some people, it may be above the frequency
> that they can hear. For me it is not (I could also hear burglar alarms in excess
> of 20KHz back in the day, though I doubt I could now, at age 70.)
>
> My *guess* is that it comes from the inductors in the switching circuit, and is
> *mechanical*, induced by the switching waveform, which in turn is
> dependent upon load. If I had one that was really bad, I'd be tempted to put
> on a glove for insulation and hold those to see if the mechanical pressure
> made any difference.
>
> JRJ
8 Jan
8 Jan
8:36 a.m.
On 1/7/2022 2:35 PM, Nigel Johnson Ham via cctalk wrote:
I told the chief engineer that the problem was the
same thing that
caused planes to crash, and he suggested maybe the cargo door had fallen
off!? (that puts it in 1972 since it was AA Flight 96 that had just
happened!)
My uncle worked for McDonnell Douglass as an engineer and my dad told me
that he got called back to work on that DC 10 door issue.
JRJ
7 Jan
7 Jan
2:33 p.m.
On 1/7/22 2:21 PM, Rob Jarratt via cctalk wrote:
Weirdly, the whine has disappeared. This is after I
put the suspect capacitors back in. Because I had previously removed them for reforming, I
wonder if one of them was not properly screwed in?
The terminal posts are aluminum, and can develop an oxide
layer that prevents good contact.
Removing and replacing them might improve the contact.
Jon
3:37 p.m.
The terminal posts are aluminum, and can develop an
oxide
layer that prevents good contact.
Removing and replacing them might improve the contact.
I have experienced this personally with TO-3 regulators, too. I had a bunch of triple
voltage Power One linear supplies that would intermittently brownout, had to chase the
threads in the TO-3 sockets (which served as a case terminal connection) and put toothed
washers under the screws to bond the TO-3 aluminum case.
Thanks,
Jonathan
4:41 p.m.
New subject: DEC RX01 Parts
I have acquired an RX01 dual drive set from a VAX780 (RX01W-VA). I am
converting it to fit in my PDP-8 rack.
I removed the VAX cabinet frame.
I have the front panel but I need the following parts:
IMC PEWEE BOXER 80mm fan PWS2107FL-1000 cooling fan (this unit has an
individual fan for each drive and one is bad.).
Dual Drive Front Plate (#74-12853-00). This is the black metal plate
with the ridges in it that the front panel mounts to.
RX8E Controller
The drives came with a single diskette so I need some formatted
diskettes also.
I don't know if the circuit boards are compatible with the RX8E
Controller. The Read/Write Control Board is labeled 243A and the Floppy
Disk Control Board is labeled 245A.
I don't have any other 8" floppy systems to format the disks in.
Thanks,
Mike
21 Jan
21 Jan
4:26 p.m.
New subject: DEC RX01 Parts
On Fri, Jan 7, 2022 at 7:41 PM Mike Katz via cctalk <cctalk at classiccmp.org wrote:
The format is IBM 3740. So quite common in the way that 8 inch floppies are
common.
-chuck
I don't know if the circuit boards are compatible with the RX8E
Controller. The Read/Write Control Board is labeled 243A and the Floppy
Disk Control Board is labeled 245A.
What I know about the RX01/RX02 is only from poring over the manuals and
schematics.
There is only one RX01 system. It is compatible with all the controllers.
There may be a jumper.
I don't have any other 8" floppy systems to format the disks in.
4:42 p.m.
New subject: DEC RX01 Parts
Thank you.? That is what I figured.? Now all I need is a RK8E or RX28
controller and I'm all set.
I'm becoming more and more tempted to have some of Roland's TTL version
boards made and build one up myself.
I am trying to get an 8" shugart type drive and using the GreaseWeazel I
will be able to format disks for RX01.
The author of the original firmware is working with me to modify the
firmware for the screwy RX02 format.
The nice thing about the RX01 drive set that I have is that I can just
flip a dip switch and have an RX02 instead (as long as I install the
appropriate RX02 OS/8 driver and have the RX28 controller card).
Thanks again,
??????????? Mike
On 1/21/2022 6:26 PM, Charles Dickman wrote:
On Fri, Jan 7, 2022 at 7:41 PM Mike Katz via cctalk
<cctalk at classiccmp.org> wrote:
I don't know if the circuit boards are compatible with the RX8E
Controller. The Read/Write Control Board is labeled 243A and the
Floppy
Disk Control Board is labeled 245A.
What I know about the RX01/RX02 is only from poring over the manuals
and schematics.
There is only one RX01 system. It is compatible with all the
controllers. There may be a jumper.
I don't have any other 8" floppy systems to format the disks in.
The format is IBM 3740. So quite common in the way that?8 inch
floppies are common.
-chuck
6 Jan
6 Jan
5:28 p.m.
On 2022-Jan-06, at 4:04 PM, Matt Burke via cctalk wrote:
On 06/01/2022 12:59, Jonathan Chapman via cctalk
wrote:
The intermediate step voltage at Q2.E-L1.input is not Q2 partially on. It's D5
shutting off, as it would do when L1 has discharged and current is no longer flowing in
it, and follows from the basic principles of a buck converter. Notice that the step is 5V,
i.e. the output voltage.
That said, it's not like replacing them with
new will *hurt* -- it just might not fix the whine.
I suspect that it won't fix the problem. Slightly hijacking the thread
here but hopefully in a semi-helpful way.
I have two of these regulators, one from a BA11K and one from a TS11.
Under the same test conditions the one from the TS11 produces a
significantly louder whining noise than the one from the BA11K. Given
that they are largely the same circuit as the H745 regulators and all
the ones I have are silent in operation I find it hard to believe they
are supposed to be like this. I used to have two more TS11 drives and
they both exhibited the same behaviour. Seems to be a common problem.
Now, for the one from the BA11K (quiet one) the output capacitors were
completely open (0uF) so I had to replace them. Given that I had the new
capacitors I decided to try them in the TS11 regulator to see if it
would fix the whining noise. It made no difference.
After some probing with an oscilloscope I found that between the two
regulators there was a very different waveform on the emitter of Q2.
Quiet regulator: http://www.9track.net/posts/h744/h744_ba11_q2e.png
Noisy regulator: http://www.9track.net/posts/h744/h744_ts11_q2e.png
The yellow trace is the emitter of Q2 (input of L1) and the cyan trace
is the output of L1. Q2 seems to be switching partly on then fully on in
the noisy regulator. it should of course be fully on or fully off as
seen on the quiet regulator. Also the switching frequency seems to be lower. I tried testing/swapping a few parts between the two
regulators, L1, Q2,
Q3, E1. It started out reasonably logical and after several days
descended into a unscientific mess of swapping anything and everything
that could possibly be at fault. I got to the point where I had
eliminated just about every component so I must have overlooked
something. I was hoping to stumble upon the answer and then learn
something from it but so far no luck. This project has been shelved for
a while now.
6:39 p.m.
On 1/6/22 6:04 PM, Matt Burke via cctalk wrote:
Quiet regulator: http://www.9track.net/posts/h744/h744_ba11_q2e.png
Noisy regulator: http://www.9track.net/posts/h744/h744_ts11_q2e.png
The yellow trace is the emitter of Q2 (input of L1) and the cyan trace
is the output of L1. Q2 seems to be switching partly on then fully on in
the noisy regulator. it should of course be fully on or fully off as
seen on the quiet regulator. Also the switching frequency seems to be lower.
Yes, the 2nd unit is running at 5 KHz, clearly explaining
the noise.? Possibly there is a bad flyback diode, or
something causing the different waveform.
Jon
7 Jan
7 Jan
1:22 a.m.
On 07/01/2022 02:39, Jon Elson via cctalk wrote:
Yes, the 2nd unit is running at 5 KHz, clearly
explaining the noise.?
Possibly there is a bad flyback diode, or something causing the
different waveform.
That would be D5 I guess? I did do some checks in this area but I can't
remember if I swapped that particular part with the other unit. I did a
DC test out of circuit using the bench supply and it seemed to work with
no leakage in the reverse direction. Perhaps it only fails when running
at full speed?
Regards,
Matt
6 Jan
6 Jan
2:22 a.m.
Rob,
The voltage rating is just an absolute maximum. For PSU capacitors the other
critical rating is ripple current. Lower voltages are
The capacitance value won't be too critical either. At the time that was
made typical electrolytic tolerances were -50/+100%
So your 6,000uf could be anywhere between 3,000uf and 12,000uf when new, so
I suspect these
https://uk.rs-online.com/web/p/aluminium-capacitors/8556059
Sprague, 5,800uf 50v would be ok provided they physically fit... although RS
has only one in stock...
Dave
-----Original Message-----
From: cctalk <cctalk-bounces at classiccmp.org> On Behalf Of Rob Jarratt via
cctalk
Sent: 06 January 2022 08:53
To: General Discussion: On-Topic and Off-Topic Posts
<cctalk at classiccmp.org>
Subject: Source for replacement caps in H744 regulators
I think I may need to replace the two output capacitors in some of my H744
regulators. These are screw terminal 6,000uF 10V parts. I have looked on
Mouser, Farnell and Digikey and there don't seem to be any available, and
any that are listed are really rather costly.
Does anyone know where I might find some, preferably from a reputable
supplier. Note that I am in the UK.
If I can't find 10V rated ones, then, generally up to what sort of voltage
rating
can I go? Of course, physical size will be a factor,
but electrically can
it affect
operation of the regulator if the rated voltage is too
high?
Thanks
Rob
7:50 a.m.
On 1/6/22 2:52 AM, Rob Jarratt via cctalk wrote:
I think I may need to replace the two output
capacitors in some of my H744
regulators. These are screw terminal 6,000uF 10V parts. I have looked on
Mouser, Farnell and Digikey and there don't seem to be any available, and
any that are listed are really rather costly.
Does anyone know where I might find some, preferably from a reputable
supplier. Note that I am in the UK.
Mouser is a good place to find big caps (or at least used to
be).? You might have to get "snap in" caps and solder wires
to them, that style seems to be more available.
Jon
832
days inactive
848
days old
23 comments
13 participants
participants (13)
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bhilpert＠shaw.ca -
bitwiz＠12bitsbest.com -
cc＠informatik.uni-stuttgart.de -
cctalk＠beyondthepale.ie -
chd＠chdickman.com -
cube1＠charter.net -
dave.g4ugm＠gmail.com -
elson＠pico-systems.com -
g4ajq1＠gmail.com -
lists＠glitchwrks.com -
matt＠9track.net -
robert.jarratt＠ntlworld.com -
w2hx＠w2hx.com