23 Oct
2022
23 Oct
'22
6:27 p.m.
I'm working on cleaning up a bit of battery leakage in a MicroVAX 3100
Model 10 and while it's apart I decided to look inside the PSU (an
H7822-00).
It's nice and clean inside with no bulging caps. What it does have is an
X2 capacitor, as shown here: https://photos.app.goo.gl/dpdqJ3tuGfsRDR3Y6.
It doesn't appear to be damaged and I can't see the word "RIFA" on it
anywhere but I can't see two of the sides because of other components
that get in the way.
So does anyone know for sure whether it is a RIFA brand or not, or do I
have to desolder it to be sure?
Thanks
Antonio
--
Antonio Carlini
antonio(a)acarlini.com
23 Oct
23 Oct
7:19 p.m.
On 10/23/2022 1:27 PM, Antonio Carlini via cctalk wrote:
I'm working on cleaning up a bit of battery
leakage in a MicroVAX 3100 Model 10 and while it's apart I decided to look inside the
PSU (an H7822-00).
It's nice and clean inside with no bulging caps. What it does have is an X2
capacitor, as shown here: https://photos.app.goo.gl/dpdqJ3tuGfsRDR3Y6.
It doesn't appear to be damaged and I can't see the word "RIFA" on it
anywhere but I can't see two of the sides because of other components that get in the
way.
So does anyone know for sure whether it is a RIFA brand or not, or do I have to desolder
it to be sure?
Thanks
Antonio
It looks like the RIFA caps I've removed from my DEC H7864 P/S. Though mine were
colored more toward the amber you find dead flies fossilized in and had visible cracks in
the case. The RIFA logo/name was on one side with other markings on the other side, on
the top was only the X2 and the value.
You might have to remove it just to be certain that it is a RIFA, but the top lettering
and the overall look point in that direction.
--
John H. Reinhardt
24 Oct
24 Oct
8:07 p.m.
On 23/10/2022 20:19, John H. Reinhardt via cctalk wrote:
It looks like the RIFA caps I've removed from my DEC H7864 P/S. Though
mine were colored more toward the amber you find dead flies fossilized
in and had visible cracks in the case. The RIFA logo/name was on one
side with other markings on the other side, on the top was only the X2
and the value.
You might have to remove it just to be certain that it is a RIFA, but
the top lettering and the overall look point in that direction.
On 23/10/2022 22:18, Peter Coghlan via cctalk wrote:
It does look rather like the troublesome RIFA
capacitors that come in
transparent / slightly yellow cases. However, it seems to be lacking the
usual tell tale cracks.
You are both right: I desoldered it tonight and it is indeed a RIFA:
https://photos.app.goo.gl/smYWrNeuFeo6Ragw7.
I measured it as: 28mm W x 16mm D x 13mm H. There are a couple of
matches so I'll probably buy a few from each of these:
https://www.bitsboxuk.com/index.php?main_page=product_info&cPath=65_81&…
https://www.ebay.co.uk/itm/124149363651
the bitsbox one may be a teensy bit to large but the ebay one should fit
nicely. Neither is too expensive even with postage so I'll buy a few,
given that I do have a fair few PSUs knocking around.
This is not a big deal compared to the six/ten 1800uF 25V
electrolytics in H7821/H7822 power supplies. If these are not already
leaking (look for a ring of brown goo around the base, sometimes only
visible after unsoldering them), they are very likely to start leaking
soon, even more likely if the power supply has not been stored in it's
natural orientation. These can do a lot of damage to the power supply
and anything else the goo gets on.
I have four H7868-B modules (two per BA213) that don't work and two of
them have leaking caps, and I mean *seriously* leaking!. This PSU though
(the H7822-00) is currently OK: None of the caps show any sign of
leaking or bulging. Given how easily the RIFA popped out, I might
speculatively try removing one of the 1800uF ones just to see what it
looks like underneath, and maybe measure its value too. Mouser wants
£1.10 each (for 10+) and also charges £12 minimum shipping, digikey
seems similar; eBay does have a UK seller doing 10 for £6, which might
be a better option if I need to go that way.
Antonio
--
Antonio Carlini
antonio(a)acarlini.com
1 Nov
1 Nov
8:57 p.m.
On 24/10/2022 21:07, Antonio Carlini via cctalk wrote:
the bitsbox one may be a teensy bit to large but the
ebay one should
fit nicely. Neither is too expensive even with postage so I'll buy a
few, given that I do have a fair few PSUs knocking around.
Turns out both sets of X2 caps I bought were identical and they fit
perfectly.
As I was putting the PSU back together I thought I could hear something
loose rattling inside. So I decided to dismantle it completely.
I managed to get the bottom board out, with some fiddling, but it would
be much easier if I could get the fans off. However, they seem to be
held on with some fasteners that I've not seen before. On the inside
they are some sort of trilobe fastener that seems to yield under any
sort of pressure (so I stopped) and on the outside they have a small
hole with three thin slots, but my tri-wing bits only seem to turn them
in the "tighten" direction, almost as though the whole thing is supposed
to be "fit and forget". I suppose if I had to get the fans out of the
way I could destroy those fittings and replace with some suitable M
bolts. I'm just wondering now whether I'm missing a trick for removing
the fans?
As I write this I realise that a photo or two wouldn't go amiss, so I'll
try to take a few close ups tomorrow in daylight.
Antonio
--
Antonio Carlini
antonio(a)acarlini.com
11:10 p.m.
On 24/10/2022 21:07, Antonio Carlini via cctalk wrote:
I thought those things that hold the fans on were a variation on pop rivets
but now that you mention it, I can see the "three sided slot" on the
outside. Perhaps there is something preventing them from unscrewing, so
that vibration from the fans will not end up loostening them or something
like that?
I've taken the boards out of a whole bunch of H7821 and H7822 PSUs to
replace the electrolytics without removing the fans. It was difficult at
first but the more I did, the easier it got. I did come across one seized
fan along the way but I haven't a replacement yet so I haven't got around
to removing the bad one. I should look into it.
Regards,
Peter Coghlan.
the bitsbox
one may be a teensy bit to large but the ebay one should
fit nicely. Neither is too expensive even with postage so I'll buy a
few, given that I do have a fair few PSUs knocking around.
Turns out both sets of X2 caps I bought were identical and they fit
perfectly.
As I was putting the PSU back together I thought I could hear something
loose rattling inside. So I decided to dismantle it completely.
I managed to get the bottom board out, with some fiddling, but it would
be much easier if I could get the fans off. However, they seem to be
held on with some fasteners that I've not seen before. On the inside
they are some sort of trilobe fastener that seems to yield under any
sort of pressure (so I stopped) and on the outside they have a small
hole with three thin slots, but my tri-wing bits only seem to turn them
in the "tighten" direction, almost as though the whole thing is supposed
to be "fit and forget". I suppose if I had to get the fans out of the
way I could destroy those fittings and replace with some suitable M
bolts. I'm just wondering now whether I'm missing a trick for removing
the fans?
As I write this I realise that a photo or two wouldn't go amiss, so I'll
try to take a few close ups tomorrow in daylight.
Antonio
--
Antonio Carlini
antonio(a)acarlini.com
2 Nov
2 Nov
4:26 p.m.
On 01/11/2022 23:10, Peter Coghlan via cctalk wrote:
I've taken the boards out of a whole bunch of
H7821 and H7822 PSUs to
replace the electrolytics without removing the fans. It was difficult at
first but the more I did, the easier it got. I did come across one
seized
fan along the way but I haven't a replacement yet so I haven't got around
to removing the bad one. I should look into it.
I think I have a second H7822 and a pair of H7821 supplies to look at,
so I may well end up getting some practice in!
Did you have to replace the power LED at all? I've just bench-tested the
PSU I've swapped the X2 cap in (luckily it powers up without a load, so
all I did was hook up a DVM and check out the voltages), and I noticed
that the LED didn't light. I'm pretty sure I connected it back (and it
is keyed!) so I think I may be looking for a replacement. Something in
the back of my mind says that there is something that makes the
replacement slightly non-trivial (funny LED, odd housing it fits in,
some trick to getting it out ... I can't remember unfortunately).
BTW was it just the 1800uF 25V 105degC caps (mine are brown) that you
had to replace? Mine look fine but there are some other large
electrolytics in there (two large brown 470uF voltage unclear, and one
large black cap by the mains input on which I cannot see any of the
markings).
Thanks
Antonio
--
Antonio Carlini
antonio(a)acarlini.com
5:15 p.m.
Antonio Carlini via cctalk wrote:
On 01/11/2022 23:10, Peter Coghlan via cctalk wrote:
The LED is more than just a power on indicator. When it fails to light,
it can indicate that something is not right in the PSU. It may tie in
with the "power good" output from the PSU.
It could be that it is failing to light because the regulation is not
working properly because there is no load. I'd try it with a load
before anything else. The H7822 may need a load on both boards.
To eliminate the LED from enquiries, you could try powering it from a 5V
supply via a 1KOhm resistor or something like that to see if it lights.
If it does, then further investigation in the PSU may be required.
If the LED does turn out to be bad, I forget whether it comes out by
pulling the LED out of the bezel first or taking the ring off the
rear of the bezel first, whichever works.
I've taken the boards out of a whole bunch of
H7821 and H7822 PSUs to
replace the electrolytics without removing the fans. It was difficult at
first but the more I did, the easier it got. I did come across one
seized
fan along the way but I haven't a replacement yet so I haven't got around
to removing the bad one. I should look into it.
I think I have a second H7822 and a pair of H7821 supplies to look at,
so I may well end up getting some practice in!
Did you have to replace the power LED at all? I've just bench-tested the
PSU I've swapped the X2 cap in (luckily it powers up without a load, so
all I did was hook up a DVM and check out the voltages), and I noticed
that the LED didn't light. I'm pretty sure I connected it back (and it
is keyed!) so I think I may be looking for a replacement. Something in
the back of my mind says that there is something that makes the
replacement slightly non-trivial (funny LED, odd housing it fits in,
some trick to getting it out ... I can't remember unfortunately).
BTW was it just the 1800uF 25V 105degC caps (mine are brown) that you
had to replace? Mine look fine but there are some other large
electrolytics in there (two large brown 470uF voltage unclear, and one
large black cap by the mains input on which I cannot see any of the
markings).
It was only the 1800uF 25V capacitors were bad (mine are all brown too).
In an earlier posting I said there were six of them in a H7821 and ten of
them in a H7822. I should have said five in a H7821 and nine in a H7822.
The 470uF 400V capacitors in my units were all fine.
The leaking electrolyte had damaged some other components in some cases,
especially an odd value resistor which seems to have different values in
different units, something around 464 Ohms. It is in series with an
thermistor which seems to control the speed of the fans. I've also had
a zener diode fail which caused problems with the fans. (If the fans
aren't operating properly, the LED might not light!)
Regards,
Peter Coghlan.
Thanks
Antonio
--
Antonio Carlini
antonio(a)acarlini.com
17 Nov
17 Nov
12:56 p.m.
On Wed, 2 Nov 2022, Peter Coghlan via cctalk wrote:
It does. I have an H7821 PSU where the LED lights briefly upon power-on
and then goes dark. The PSU cannot be used to power a mainboard as it
does not come up, however it works just fine with storage in an expansion
box. It is one of those that I recapped after leaks have appeared; in
fact it is the one that made me aware of the problem in the first place.
I'll have to get back to it sometime to get this sorted.
Same here, five 1800uF 25V caps to replace in the H7821 according to my
notes. Overall if you spot a cap that says SXF on it, then replace it
right away whether already leaking or not. These were made by Chemi-con.
Other Chemi-con lines reported problematic are SXE and LXF, though from
own experience they seem less prone.
Also Nichicon PL and PF parts may have to be replaced, I have seen the
former ones actually leaking in other DEC PSUs, such as the H7826, which
is also infested by SXF parts in various capacitances. Both kinds leaked
in a generic industrial Bel Power PSU used with a Cisco device.
Sadly the problem with component shortage has hit capacitors as well and
some that used to be readily available are not anymore and prices have
risen too.
NB I wasn't aware about the problem with RIFA capacitors, it seems like I
might have to replace them in several PSUs I have already recapped, sigh.
I haven't seen any of them fail though, not at least in an obvious way.
HTH,
Maciej
Did you have
to replace the power LED at all? I've just bench-tested the PSU
I've swapped the X2 cap in (luckily it powers up without a load, so all I
did was hook up a DVM and check out the voltages), and I noticed that the
LED didn't light. I'm pretty sure I connected it back (and it is keyed!) so
I think I may be looking for a replacement. Something in the back of my mind
says that there is something that makes the replacement slightly non-trivial
(funny LED, odd housing it fits in, some trick to getting it out ... I can't
remember unfortunately).
The LED is more than just a power on indicator. When it fails to light,
it can indicate that something is not right in the PSU. It may tie in
with the "power good" output from the PSU. It could be that it is failing to light because the
regulation is not
working properly because there is no load. I'd try it with a load
before anything else. The H7822 may need a load on both boards.
There's a 2Ω dummy load on the 5V line in storage expansion boxes powered
by the H7821, so these do require minimum current to work correctly.
BTW was it
just the 1800uF 25V 105degC caps (mine are brown) that you had to
replace? Mine look fine but there are some other large electrolytics in
there (two large brown 470uF voltage unclear, and one large black cap by the
mains input on which I cannot see any of the markings).
It was only the 1800uF 25V capacitors were bad (mine are all brown too).
In an earlier posting I said there were six of them in a H7821 and ten of
them in a H7822. I should have said five in a H7821 and nine in a H7822.
The 470uF 400V capacitors in my units were all fine.
18 Nov
18 Nov
10:51 a.m.
Maciej W. Rozycki via cctalk wrote:
Same here, five 1800uF 25V caps to replace in the H7821 according to my
notes. Overall if you spot a cap that says SXF on it, then replace it
right away whether already leaking or not. These were made by Chemi-con.
Other Chemi-con lines reported problematic are SXE and LXF, though from
own experience they seem less prone.
Also Nichicon PL and PF parts may have to be replaced, I have seen the
former ones actually leaking in other DEC PSUs, such as the H7826, which
is also infested by SXF parts in various capacitances. Both kinds leaked
in a generic industrial Bel Power PSU used with a Cisco device.
I agree that all the 1800uF capacitors should be replaced whether leaking
or not. When I first checked all my H7821 power supplies, I found some
that looked absolutely fine. However, after I started using them for a
while, problems began to show up and when I checked them again, they were
leaking badly.
Sadly the problem with component shortage has hit capacitors as well and
some that used to be readily available are not anymore and prices have
risen too.
Even if replacements are not available, I would suggest immediately removing
any capacitors that are showing any signs of leakage and cleaning the affected
area in order to limit damage from the leakage.
NB I wasn't aware about the problem with RIFA capacitors, it seems like I
might have to replace them in several PSUs I have already recapped, sigh.
I haven't seen any of them fail though, not at least in an obvious way.
I wouldn't worry too much about the RIFAs. Their failure mode is to produce
lots of smoke a short while after switch on. Apart from a bit of soot, they
don't do any damage to anything else while the faulty electrolytics can do a
considerable amount of damage without any visible external sign that anything
is wrong. I haven't seen any failures of any of the RIFAs in my H7821 or
H7822 power supplies and even if they are going to fail eventually, I am
happy enough to wait for this to happen before doing anything about it because
it will be obvious to me when they do fail and the consequences of their
failure are not severe anyway.
Regards,
Peter Coghlan
HTH,
Maciej
15 Nov
15 Nov
10:06 a.m.
On 24/10/2022 21:07, Antonio Carlini via cctalk wrote:
the bitsbox one may be a teensy bit to large but the
ebay one should
fit nicely. Neither is too expensive even with postage so I'll buy a
few, given that I do have a fair few PSUs knocking around.
Just a quick follow-up in case it helps someone else down the line. I've
put the system back together and the H7822 PSU seems to work: with the
mainboard connected the green LED lights (and the fans spin). So that's
good.
The mainboard stays in the reset state (all diagnostic LEDs lit) so that
might still be an issue with the PSU DC OK signal or the mainboard
itself. However, at this stage the PSU is behaving as expected.
Antonio
--
Antonio Carlini
antonio(a)acarlini.com
11:22 p.m.
On 15/11/2022 10:06, Antonio Carlini via cctalk wrote:
On 24/10/2022 21:07, Antonio Carlini via cctalk
wrote:
My experience with a H7822 is that when all the diagnostic LEDs stay lit,
DC OK is probably not getting asserted so the power supply might still
not be working 100% correctly. In the H7822, DC OK seems to be the
purple lead and high (something around 4V-5V) means asserted.
Regards,
Peter Coghlan.
the bitsbox one may be a teensy bit to large but
the ebay one should
fit nicely. Neither is too expensive even with postage so I'll buy a
few, given that I do have a fair few PSUs knocking around.
Just a quick follow-up in case it helps someone else down the line. I've
put the system back together and the H7822 PSU seems to work: with the
mainboard connected the green LED lights (and the fans spin). So that's
good.
The mainboard stays in the reset state (all diagnostic LEDs lit) so that
might still be an issue with the PSU DC OK signal or the mainboard
itself. However, at this stage the PSU is behaving as expected.
Antonio
--
Antonio Carlini
antonio(a)acarlini.com
17 Nov
17 Nov
12:33 a.m.
On 15/11/2022 23:22, Peter Coghlan via cctalk wrote:
My experience with a H7822 is that when all the
diagnostic LEDs stay lit,
DC OK is probably not getting asserted so the power supply might still
not be working 100% correctly. In the H7822, DC OK seems to be the
purple lead and high (something around 4V-5V) means asserted.
Thanks, but sadly in this case it's not such a simple diagnosis. I had a
spare 15 mins tonight so I powered it up and checked (DC OK is indeed
the purple lead). DC OK is sitting at 5.13V so the problem lies elsewhere.
I do have another H7822 in a MicroVAX 3100-80 (iirc, could be -40) and
that one doesn't start either. I've done nothing with that one at all
since it has a Dallas chip and so didn't need any remedial work. At some
point I'll get back to these and spend some time trying to get them
going. But I need to do some work on a Rainbow and some uV3600 PSUs
first before I get back to working through uVAX/VS 3100 PSUs (I also
have 5 H7821 PSUs there, so I expect that I'll be back ...).
Antonio
--
Antonio Carlini
antonio(a)acarlini.com
23 Oct
23 Oct
9:18 p.m.
I'm working on cleaning up a bit of battery leakage in a MicroVAX 3100
Model 10 and while it's apart I decided to look inside the PSU (an
H7822-00).
It's nice and clean inside with no bulging caps. What it does have is an
X2 capacitor, as shown here: https://photos.app.goo.gl/dpdqJ3tuGfsRDR3Y6.
It doesn't appear to be damaged and I can't see the word "RIFA" on it
anywhere but I can't see two of the sides because of other components
that get in the way.
So does anyone know for sure whether it is a RIFA brand or not, or do I
have to desolder it to be sure?
Antonio,
It does look rather like the troublesome RIFA capacitors that come in
transparent / slightly yellow cases. However, it seems to be lacking the
usual tell tale cracks.
If it is a RIFA, the worst it will do is create lots of smoke and stink
the place out. This is not a big deal compared to the six/ten 1800uF 25V
electrolytics in H7821/H7822 power supplies. If these are not already
leaking (look for a ring of brown goo around the base, sometimes only
visible after unsoldering them), they are very likely to start leaking
soon, even more likely if the power supply has not been stored in it's
natural orientation. These can do a lot of damage to the power supply
and anything else the goo gets on.
I would prioritise sorting out the ten dodgy electrolytics and deal with
the suspected RIFA afterwards.
(I found that the top board in a H7822 is identical or nearly identical
to the single board in a H7821)
Regards,
Peter Coghlan.
Thanks
Antonio
--
Antonio Carlini
antonio(a)acarlini.com
734
days inactive
760
days old
12 comments
4 participants
participants (4)
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Antonio Carlini -
John H. Reinhardt -
Maciej W. Rozycki -
Peter Coghlan