20 Apr
2020
20 Apr
'20
11:15 a.m.
Hi friends,
Now that I have enough hobby time having quit my job two weeks before the
apocalypse, I'm interested in poking at my Kennedy 9800 tape controller
project.
I bought the tape unit in Q3 2017 and the seller said they had powered it
up and nothing seemed awry. I have not powered it up and reading about old
electrolytic cap issues I'm curious if I should do anything beyond replace
any obviously leaking/ruptured capacitors.
IIRC people have used a variac to gradually bring the power supply up to
operating voltage and somewhat refresh the capacitors - is this a thing? Is
this advisable?
Any help is appreciated!
--
Anders Nelson
www.erogear.com
22 Apr
22 Apr
5:35 p.m.
At least in radio repair of old equipment,,,, old electrolytic caps
cause all sorts of issues. Most of the guys doing restoration do a total
remove/replace on them.? In my opinion,,, I think that's a little
extreme,,, but then having one fail after all the other work is done is
also a PITA.
On 4/20/20 11:15 AM, Anders Nelson via cctalk wrote:
Hi friends,
Now that I have enough hobby time having quit my job two weeks before the
apocalypse, I'm interested in poking at my Kennedy 9800 tape controller
project.
I bought the tape unit in Q3 2017 and the seller said they had powered it
up and nothing seemed awry. I have not powered it up and reading about old
electrolytic cap issues I'm curious if I should do anything beyond replace
any obviously leaking/ruptured capacitors.
IIRC people have used a variac to gradually bring the power supply up to
operating voltage and somewhat refresh the capacitors - is this a thing? Is
this advisable?
Any help is appreciated!
--
Anders Nelson
www.erogear.com
23 Apr
23 Apr
8:58 a.m.
Cool, thanks for your take. I found some articles:
-
http://www.angelfire.com/electronic/funwithtubes/steps_to_first_power_on.ht…
- http://www.angelfire.com/electronic/funwithtubes/Restore_cap.html
Given this unit doesn't have any tubes, I imagine the motor drivers/amps in
this thing would simply go to zero output with shorted caps. The PSU might
blow the fuse and/or rectifier with a shorted bulk output cap. This unit is
very difficult to remove from the rack it's in so I'm trying to avoid
preemptive repairs.
I'm going to pick up a variac on Amazon when I finish up some other things:
https://www.amazon.com/dp/B076Y2XHRS/ref=twister_B07G5BHXYV
Happy to hear any constructive criticism.
--
Anders Nelson
+1 (517) 775-6129
www.erogear.com
On Thu, Apr 23, 2020 at 12:37 AM "Grif" w. keith griffith via cctalk <
cctalk at classiccmp.org> wrote:
At least in radio repair of old equipment,,,, old electrolytic caps
cause all sorts of issues. Most of the guys doing restoration do a total
remove/replace on them. In my opinion,,, I think that's a little
extreme,,, but then having one fail after all the other work is done is
also a PITA.
On 4/20/20 11:15 AM, Anders Nelson via cctalk wrote:
Hi friends,
Now that I have enough hobby time having quit my job two weeks before the
apocalypse, I'm interested in poking at my Kennedy 9800 tape controller
project.
I bought the tape unit in Q3 2017 and the seller said they had powered it
up and nothing seemed awry. I have not powered it up and reading about
old
electrolytic cap issues I'm curious if I
should do anything beyond
replace
any obviously leaking/ruptured capacitors.
IIRC people have used a variac to gradually bring the power supply up to
operating voltage and somewhat refresh the capacitors - is this a thing?
Is
this advisable?
Any help is appreciated!
--
Anders Nelson
www.erogear.com
10:53 a.m.
I'm under caffeinated and not really with it yet, having recently gone semi
nocturnal, so you'll want to double check this with someone who's actually
awake.
That said, variacs aren't a universal panacea and can sometimes be harmful
rather than helpful. My disorganized memory is offering TVs as an example,
but take that with a pinch of salt. I've only ever used them with tube
radios and amps, so have nothing further to offer, save this caution.
--
Robert
On Thu, Apr 23, 2020, 10:59 AM Anders Nelson via cctalk <
cctalk at classiccmp.org> wrote:
Cool, thanks for your take. I found some articles:
-
http://www.angelfire.com/electronic/funwithtubes/steps_to_first_power_on.ht…
- http://www.angelfire.com/electronic/funwithtubes/Restore_cap.html
Given this unit doesn't have any tubes, I imagine the motor drivers/amps in
this thing would simply go to zero output with shorted caps. The PSU might
blow the fuse and/or rectifier with a shorted bulk output cap. This unit is
very difficult to remove from the rack it's in so I'm trying to avoid
preemptive repairs.
I'm going to pick up a variac on Amazon when I finish up some other things:
https://www.amazon.com/dp/B076Y2XHRS/ref=twister_B07G5BHXYV
Happy to hear any constructive criticism.
--
Anders Nelson
+1 (517) 775-6129
www.erogear.com
On Thu, Apr 23, 2020 at 12:37 AM "Grif" w. keith griffith via cctalk <
cctalk at classiccmp.org> wrote:
to
At least in radio repair of old equipment,,,, old electrolytic caps
cause all sorts of issues. Most of the guys doing restoration do a total
remove/replace on them. In my opinion,,, I think that's a little
extreme,,, but then having one fail after all the other work is done is
also a PITA.
On 4/20/20 11:15 AM, Anders Nelson via cctalk wrote:
> Hi friends,
>
> Now that I have enough hobby time having quit my job two weeks before
the
> apocalypse, I'm interested in poking at
my Kennedy 9800 tape controller
> project.
>
> I bought the tape unit in Q3 2017 and the seller said they had powered
it
up and
nothing seemed awry. I have not powered it up and reading about
old
electrolytic cap issues I'm curious if I
should do anything beyond
replace
> any obviously leaking/ruptured capacitors.
>
> IIRC people have used a variac to gradually bring the power supply up > operating voltage and somewhat refresh the
capacitors - is this a
thing?
Is
this advisable?
Any help is appreciated!
--
Anders Nelson
www.erogear.com
11:09 a.m.
On 04/23/2020 12:53 PM, Robert via cctalk wrote:
I'm under caffeinated and not really with it yet,
having recently gone semi
nocturnal, so you'll want to double check this with someone who's actually
awake.
That said, variacs aren't a universal panacea and can sometimes be harmful
rather than helpful. My disorganized memory is offering TVs as an example,
but take that with a pinch of salt. I've only ever used them with tube
radios and amps, so have nothing further to offer, save this caution.
Well, if the power supply is all linear, a Variac is
probably fine to slowly ramp up the capacitors and
let the dielectric reform.
If it has switching power supplies, this can cause the
supply to try to operate at severe undervoltage, and cause
damage. On the other hand, powering it up to 10 V or so on
the AC input for a few minutes
is unlikely to allow the switching stage to start up, but
will reform the main input storage caps.
It won't reform the low voltage caps in the rest of the
unit, though. You could apply low voltage
(1-2 V for a minute or two) to each low voltage rail before
fully powering on. Especially if it
has bunches of tantalum caps in the logic, that could
prevent disaster.
Jon
5:43 p.m.
Hey this is all super useful info, thanks!
Any idea how to visually identify a tantalum cap? I suppose I could Google
it but maybe standards have changed between 1984 and 2020?
On Thu, Apr 23, 2020, 8:06 PM Jon Elson via cctalk <cctalk at classiccmp.org>
wrote:
On 04/23/2020 12:53 PM, Robert via cctalk wrote:
I'm under caffeinated and not really with it
yet, having recently gone
semi
nocturnal, so you'll want to double check
this with someone who's
actually
awake.
That said, variacs aren't a universal panacea and can sometimes be
harmful
rather than helpful. My disorganized memory is
offering TVs as an
example,
but take that with a pinch of salt. I've only
ever used them with tube
radios and amps, so have nothing further to offer, save this caution.
Well, if the power supply is all linear, a Variac is
probably fine to slowly ramp up the capacitors and
let the dielectric reform.
If it has switching power supplies, this can cause the
supply to try to operate at severe undervoltage, and cause
damage. On the other hand, powering it up to 10 V or so on
the AC input for a few minutes
is unlikely to allow the switching stage to start up, but
will reform the main input storage caps.
It won't reform the low voltage caps in the rest of the
unit, though. You could apply low voltage
(1-2 V for a minute or two) to each low voltage rail before
fully powering on. Especially if it
has bunches of tantalum caps in the logic, that could
prevent disaster.
Jon
8:19 p.m.
On 04/23/2020 07:43 PM, Anders Nelson via cctalk wrote:
Hey this is all super useful info, thanks!
Any idea how to visually identify a tantalum cap? I suppose I could Google
it but maybe standards have changed between 1984 and 2020?
They would be small ones on the circuit boards, not likely
in the power supply, but possible.
Generally, the old ones from the '70s and 80's would have
what looks like an aluminum can
wrapped with clear plastic (probably shrink tubing) with the
label printed on the metal part.
There will be some kind of epoxy plug poured in one end.
Another type look kind of like teardrops, they are dipped in
epoxy and have two skinny leads
coming out of the narrow part of the teardrop.
Jon
11:20 a.m.
On 4/23/20 10:53 AM, Robert via cctalk wrote:
I'm under caffeinated and not really with it yet,
having recently gone semi
nocturnal, so you'll want to double check this with someone who's actually
awake.
That said, variacs aren't a universal panacea and can sometimes be harmful
rather than helpful. My disorganized memory is offering TVs as an example,
but take that with a pinch of salt. I've only ever used them with tube
radios and amps, so have nothing further to offer, save this caution.
My own experience is that they're pretty much useless when a siwtch-mode
power supply is involved.
If you're dealing with a linear power supply, a good first move, in my
experience, is to hook a high-wattage (say, 100W) in series with the AC
line for first power-up.
--Chuck
11:21 a.m.
On Thu, Apr 23, 2020 at 11:59 AM Anders Nelson via cctalk <
cctalk at classiccmp.org> wrote:
Cool, thanks for your take. I found some articles:
-
http://www.angelfire.com/electronic/funwithtubes/steps_to_first_power_on.ht…
- http://www.angelfire.com/electronic/funwithtubes/Restore_cap.html
Given this unit doesn't have any tubes, I imagine the motor drivers/amps in
this thing would simply go to zero output with shorted caps. The PSU might
blow the fuse and/or rectifier with a shorted bulk output cap. This unit is
very difficult to remove from the rack it's in so I'm trying to avoid
preemptive repairs.
I'd personally say that since it hasn't been off for that long (less than 3
years) and since it sounds like you're not interested in taking it apart,
I'd just plug it back in, and see how that goes.
As a minimal step, I might disconnect the PSU from the rest of the drive,
and plug it in like that for a moment, but it's probably best to not run it
without a load for very long.
Pat
12:12 p.m.
On 4/23/20 11:21 AM, Patrick Finnegan via cctalk wrote:
As a minimal step, I might disconnect the PSU from the
rest of the drive,
and plug it in like that for a moment, but it's probably best to not run it
without a load for very long.
The 9800 is the 8" little brother to the 9000 tension arm drive. The service manual
is on bitsavers, it probably has a linear power supply. There is also an inverter
supply shown but that is probably for special applications.
2:11 p.m.
On 4/23/20 12:12 PM, Al Kossow via cctalk wrote:
The 9800 is the 8" little brother to the 9000
tension arm drive. The
service manual
is on bitsavers, it probably has a linear power supply. There is also an
inverter
supply shown but that is probably for special applications.
That's the one that Sellam was selling, IIRC. Incremental (i.e stepper)
drive. Great for key-to-tape application.
--Chuck
1:12 p.m.
Thanks for all the input!
@Chuck: I assume you are talking about a 100W incandescent light bulb, I
like that idea for current-limiting. And I agree a SMPS should cut off the
switch if it detects a short; not sure what kind of supply is in there but
I'll take a look.
@Patrick: There's a stamp on the unit that seems to indicate it was made in
1984 but yeah the eBayer applied power normally before I got it.
Thanks!
On Thu, Apr 23, 2020, 2:21 PM Patrick Finnegan <pat at vax11.net> wrote:
On Thu, Apr 23, 2020 at 11:59 AM Anders Nelson via
cctalk <
cctalk at classiccmp.org> wrote:
Cool, thanks for your take. I found some
articles:
-
http://www.angelfire.com/electronic/funwithtubes/steps_to_first_power_on.ht…
- http://www.angelfire.com/electronic/funwithtubes/Restore_cap.html
Given this unit doesn't have any tubes, I imagine the motor drivers/amps
in
this thing would simply go to zero output with shorted caps. The PSU might
blow the fuse and/or rectifier with a shorted bulk output cap. This unit
is
very difficult to remove from the rack it's in so I'm trying to avoid
preemptive repairs.
I'd personally say that since it hasn't been off for that long (less than
3 years) and since it sounds like you're not interested in taking it apart,
I'd just plug it back in, and see how that goes.
As a minimal step, I might disconnect the PSU from the rest of the drive,
and plug it in like that for a moment, but it's probably best to not run it
without a load for very long.
Pat
2:09 p.m.
On 4/23/20 1:12 PM, Anders Nelson via cctalk wrote:
Thanks for all the input!
@Chuck: I assume you are talking about a 100W incandescent light bulb, I
like that idea for current-limiting. And I agree a SMPS should cut off the
switch if it detects a short; not sure what kind of supply is in there but
I'll take a look.
Incandescent, yes, as a poor man's current limiter/fault indicator.
--Chuck
1473
days inactive
1477
days old
12 comments
7 participants
participants (7)
-
aek＠bitsavers.org -
anders.k.nelson＠gmail.com -
cclist＠sydex.com -
elson＠pico-systems.com -
kgriffit＠mindspring.com -
pat＠vax11.net -
robert626001＠gmail.com