Date   

Re: OT question about oil filled caps

stefan_trethan
 

I agree with Brian this makes no sense. Perhaps you are confusing oil
filled capacitors with electrolytic. The electrolyte can kinda look
like oil, and sometimes, in the eternal words of one customer "smells
like bacon".

Perhaps the "managing" you mentioned caused the misunderstanding, it
often does. ;-)

ST

On Fri, Dec 30, 2016 at 3:49 AM, swingdancer swingdancerman@...
[TekScopes] <TekScopes@...> wrote:
In my experience oil filled Caps fail either because they are wired backwards or are just poor quality, or not ov protected.I have seen it all managing a power supply manufacturing department. During power supply burn in, caps exploding, oil all over the place, burnt P/S.Some times a bad one gets out into the field.
Regards,Richard


Re: OT question about oil filled caps

Brian <brianclarke01@...>
 

Have you photographic evidence to back up your story?
Oil-filled capacitors wired up backwards? My oh my, what will chicken licken think of next?
Oil-filled capacitors catching fire? What oil was in them? Manufacturers chose oils like poly-chloral biphenols to avoid fire. Normally, oil does not burn; it is the vapor that might burn. But to reach vaporisation temperature in an oil-filled capacitor sounds like either poor quality components, or poor quality PSU design. When I tested oils for transformers – very similar oils – I needed to reach over 7k5 V before submerged electrodes would even discharge, and there was no flame.
The only way I can imagine oil-filled capacitors catching fire is if:
a.. the can is steel
b.. the steel rusts, usually from the outside in – if it rusts from the inside out, the bushes are pumping humid air past their seals (pumping = as the capacitor heats and cools)
c.. the oil leaks out and air enters the void left by the departing oil
d.. the oil vapour was flammable in the first place.
The first three are down to poor maintenance; the last is very poor design.

I suspect urban myths are being propagated.
73 de Brian, VK2GCE.

On Friday, December 30, 2016 1:49 PM, Richard said:

In my experience oil filled Caps fail either because they are wired backwards or are just poor quality, or not ov protected.I have seen it all managing a power supply manufacturing department. During power supply burn in, caps exploding, oil all over the place, burnt P/S.Some times a bad one gets out into the field.
Regards,Richard

And Dick said:


I would add that, in my experience, some oil filled caps are prone to take
overvoltages very personally - they sometimes explode. They don't just punch
through and catch fire.


Re: OT question about oil filled caps

Vince Vielhaber
 

As I posted earlier, Motorola knows how to pack 50 lbs of crap into a 5lb coffee can. After disassembling it to the point where I could actually see what was going on, I found these are large can electrolytics. The ones with the rubber plug in the bottom and the two screw terminals. What that liquid was, I have no idea but it was oily and didn't smell pleasantly and yes, they both leaked - or should I say they emptied themselves. Didn't stink, but wasn't something you'd want to smell all day (sure glad the new bench has a rubber top!)

These are 30,000uv 15v caps, 2" dia, 2" long. I was able to find a set of three 64,000 uf caps at 15v that are almost the same physical size. They're 1/8" too tall, so hopefully I don't have to machine 1/8" off the posts. Yes, they packed them in that tight. I almost bought 4 18,000uf caps and was going to parallel them and they almost would've fit but the speaker magnet actually sits between the two. Like I said, packed in!

So what was that junk that leaked out? They still tested ok with low ESR.

Vince.

On 12/29/2016 10:44 PM, `Richard Knoppow dickburk@... [TekScopes] wrote:
Where did you encounter oil filled electrolytic caps? All I have
ever seen were paper or plastic dielectric. Not polarized. If you had
caps explode due to reverse polarity they were electrolytics and the
gunk was probably the electrolyte in them. Usually smell like ammonia or
fish.
There were a couple of forms of oil filled paper caps, those made
for transmitting or long life in receivers were in metal cans. Some,
like the notorious Black Beauty, were in molded Bakelite cases with some
oil injected. I think the only BBs with oil were the 600V rating. They
had one lead which was also the filler tube. They often lost the seal
from excessive soldering heat so the oil leaked out.

On 12/29/2016 6:49 PM, swingdancer swingdancerman@... [TekScopes]
wrote:

In my experience oil filled Caps fail either because they are wired
backwards or are just poor quality, or not ov protected.I have seen
it all managing a power supply manufacturing department. During power
supply burn in, caps exploding, oil all over the place, burnt
P/S.Some times a bad one gets out into the field.
Regards,Richard

From: "'R.L. Wurdack' dickw@... [TekScopes]"
<TekScopes@...>
To: TekScopes@...
Sent: Wednesday, December 28, 2016 11:00 PM
Subject: Re: [TekScopes] OT question about oil filled caps

I would add that, in my experience, some oil filled caps are prone to
take
overvoltages very personally - they sometimes explode. They don't just
punch
through and catch fire.

Dick

----- Original Message -----
From: "Vince Vielhaber vev@... [TekScopes]"
<TekScopes@...>
To: <TekScopes@...>
Sent: Tuesday, December 27, 2016 11:37 PM
Subject: Re: [TekScopes] OT question about oil filled caps

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Yahoo Groups Links



Re: OT question about oil filled caps

Richard Knoppow
 

An interesting article. There is actually a military handbook on
reforming capacitors. I will have to find the link.
For the most part I think reforming is wishful thinking.
Electrolytics are easily available and not too expensive. To me it makes
more sense to replace old ones with new caps.

On 12/29/2016 7:36 PM, AncelB mosaicmerc@... [TekScopes] wrote:

Regarding vintage caps replacement/repair: this was interesting:
https://www.nmr.mgh.harvard.edu/~reese/electrolytics/

--
Richard Knoppow
dickburk@...
WB6KBL


Re: OT question about oil filled caps

Richard Knoppow
 

Where did you encounter oil filled electrolytic caps? All I have
ever seen were paper or plastic dielectric. Not polarized. If you had
caps explode due to reverse polarity they were electrolytics and the
gunk was probably the electrolyte in them. Usually smell like ammonia or
fish.
There were a couple of forms of oil filled paper caps, those made
for transmitting or long life in receivers were in metal cans. Some,
like the notorious Black Beauty, were in molded Bakelite cases with some
oil injected. I think the only BBs with oil were the 600V rating. They
had one lead which was also the filler tube. They often lost the seal
from excessive soldering heat so the oil leaked out.

On 12/29/2016 6:49 PM, swingdancer swingdancerman@... [TekScopes]
wrote:

In my experience oil filled Caps fail either because they are wired
backwards or are just poor quality, or not ov protected.I have seen
it all managing a power supply manufacturing department. During power
supply burn in, caps exploding, oil all over the place, burnt
P/S.Some times a bad one gets out into the field.
Regards,Richard

From: "'R.L. Wurdack' dickw@... [TekScopes]"
<TekScopes@...>
To: TekScopes@...
Sent: Wednesday, December 28, 2016 11:00 PM
Subject: Re: [TekScopes] OT question about oil filled caps

I would add that, in my experience, some oil filled caps are prone to
take
overvoltages very personally - they sometimes explode. They don't just
punch
through and catch fire.

Dick

----- Original Message -----
From: "Vince Vielhaber vev@... [TekScopes]"
<TekScopes@...>
To: <TekScopes@...>
Sent: Tuesday, December 27, 2016 11:37 PM
Subject: Re: [TekScopes] OT question about oil filled caps

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Yahoo Groups Links



--
Richard Knoppow
dickburk@...
WB6KBL



[Non-text portions of this message have been removed]


Re: OT question about oil filled caps

mosaicmerc
 

Regarding vintage caps replacement/repair: this was interesting:
https://www.nmr.mgh.harvard.edu/~reese/electrolytics/


Re: New Member Dead 7704

volvoboy242@...
 

OK so that row of nine mystery traces are actually numbers. A row of ones in horizontal mode B and nine fours in all other modes.


Re: New Member Dead 7704

volvoboy242@...
 


Re: New Member Dead 7704

volvoboy242@...
 

Well the youtube vid fixed it. Good suggestion!
As soon as I started recording on my phone, the screen lit up.
I was able to get focus and I could read my volts/div.
I tried to get a trace but the screen faded very slowly and went out.
Much button pushing and knob wiggling later (plus pulling the beam finder) and I got this:
2016-12-29_22-02-45_281.jpg https://drive.google.com/open?id=0BydAjXF94zykWGR1ellCMi1SbFE

https://drive.google.com/open?id=0BydAjXF94zykWGR1ellCMi1SbFE

2016-12-29_22-02-45_281.jpg https://drive.google.com/open?id=0BydAjXF94zykWGR1ellCMi1SbFE Sign in Main menu



View on drive.google.com https://drive.google.com/open?id=0BydAjXF94zykWGR1ellCMi1SbFE
Preview by Yahoo







Seems like a good cleaning, re seating some chips and maybe a couple caps and I'll be able to calibrate and use it.
Will share videos shortly.


Re: OT question about oil filled caps

swingdancer <swingdancerman@...>
 

In my experience oil filled Caps fail either because they are wired backwards or are just poor quality, or not ov protected.I  have seen it all managing a power supply manufacturing department. During power supply burn in, caps exploding, oil all  over the place, burnt P/S.Some times a bad one gets out into the field. 
Regards,Richard


From: "'R.L. Wurdack' dickw@... [TekScopes]" <TekScopes@...>
To: TekScopes@...
Sent: Wednesday, December 28, 2016 11:00 PM
Subject: Re: [TekScopes] OT question about oil filled caps

I would add that, in my experience, some oil filled caps are prone to take
overvoltages very personally - they sometimes explode. They don't just punch
through and catch fire.

Dick

----- Original Message -----
From: "Vince Vielhaber vev@... [TekScopes]"
<TekScopes@...>
To: <TekScopes@...>
Sent: Tuesday, December 27, 2016 11:37 PM
Subject: Re: [TekScopes] OT question about oil filled caps





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Re: New Member Dead 7704

Joseph Tatum
 

Rght now I have the control board out of it so cannot turn it back on until I get it re-assembled. I do not have a YouTube account right now.


Re: New Member Dead 7704

 

How about a short video to Youtube?

----- Original Message -----
From: tatumj1@... [TekScopes]
To: TekScopes@...
Sent: Thursday, December 29, 2016 7:16 PM
Subject: [TekScopes] Re: New Member Dead 7704



The only glow I expected would be the scale illumination. But this is like a trace that fills almost the whole screen.


Re: Thank for add to group.

Joseph Tatum
 

I will keep that in mind. Right now I am working with a pretty good PDF copy I downloaded. Everything is pretty clear except the photos.


Re: Thank for add to group.

Joseph Tatum
 

Thanks, I will check it out. Looks like huge resource.


Re: New Member Dead 7704

Joseph Tatum
 

The only glow I expected would be the scale illumination. But this is like a trace that fills almost the whole screen.


Re: Thank for add to group.

Joseph Tatum
 

What happens is that almost the whole screen glows and the band fills the screen top to bottom. When horiz rate is changed you can see a that is is sweeping horizontally.


Re: Good Tm503 w plugins deal

 

I'm not so sure. Something is wrong with the way the DC504 counter's front panel at the top looks "Catty-Wompus" either that or the frame of the TM503 is bent. I notice the seller doesn't mention the condition of the DC 504. The rest is a good deal.

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@... [mailto:TekScopes@...]
Sent: Thursday, December 29, 2016 8:12 AM
To: TekScopes@...
Subject: Re: [TekScopes] Good Tm503 w plugins deal

Somebody got a steal! Wow.


--
Joe Laffey

On Dec 29, 2016, at 7:47 AM, mosaicmerc@... [TekScopes] <TekScopes@...> wrote:

TEKTRONIX DM501A DIGITAL MULTIMETER PLUG IN TM504 TM506 TM5006 BENCH TOP TESTING | eBay http://www.ebay.com/itm/142221367884?ul_noapp=true

http://www.ebay.com/itm/142221367884?ul_noapp=true

TEKTRONIX DM501A DIGITAL MULTIMETER PL... http://www.ebay.com/itm/142221367884?ul_noapp=true TEKTRONIX DM501A DIGITAL MULTIMETER PLUG IN TM504 TM506 TM5006 BENCH TOP TESTING | Business & Industrial, Electrical & Tes...
View on www.ebay.com http://www.ebay.com/itm/142221367884?ul_noapp=true
Preview by Yahoo
no affiliation.
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Posted by: Joe Laffey <joe@...>
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Re: Tek 464 - Correct transistor for Sync Generator Matched FETs 151-1042-00

 

On Thu, 29 Dec 2016 18:29:19 -0200, you wrote:

...

To what extent would
the performance of the buffer >circuit change if the resistor >values were
reduced to 0 ohm?
Strictly answering to your question, this circuit won't work as intended if
source resistors are 0 ohm.
In this circuit's design, the voltage drop at the source resistors is
required because a change in the
Drain-to-Source current translates into a change in the voltage drop that
is fed back into the transistor's gate,
which ultimately is what locks the transistor into the intended bias point.
We can, however, talk about making this value lower and lower if there's a
need for that (e.g. to lower the output
impedance of the buffer) but:
1. It can't EVER be 0 (well, there's no 0 Ohm resistance anyway) and...
2. Its value is not guesswork...It`s calculated in order to have the right
voltage drop at a desired current,
Both voltage drop and current are dependent on the particular
transistor that was chosen for the task.
In this particular Tek 464's circuit, 15 Ohm is probably the best value
that was possible, considering all
the design constraints (the transistor, the operating voltage, the
desired frequency response, etc, etc...)
There are a couple of other things the source resistors affect:

1. Transconductance of a JFET is proportional to the square root
of the drain current and the bandwidth is proportional to the
transconductance so lowering the drain current with the resistors
lowers the transconductance and bandwidth which might be necessary for
stability.

2. Lowering the drain current lowers the power dissipation. Some
JFETs have a high enough Idss that their power dissipation would be
exceeded if Vgs was held at zero volts.

3. The source resistance in the top JFET changes the load impedance
seen at the source which may be necessary for stability. You can find
low value resistors sprinkled here and there for this reason. For
instance the low value gate resistor cancels the negative resistance
at the gate.

I suspect the most important criteria is stability insofar as it
affects transient response.


Re: New Member Dead 7704

volvoboy242@...
 

The numbers are gone too. Doesn't the screen glow normally? I have a vague recollection of how it used to work.
I thought it had a glow visible with the grid ilum dimmed all the way.


Are there diagnostic pins or connectors to test? Something to probe without damaging anything?


Re: New Member Dead 7704

Jerry Massengale <jmassen418@...>
 

Mike,

Where do you see a quick flash? Is it green on the crt? You can at least
check for the -3Kv HV primary. Your unit may have something as simple as a
deflection plate connection loose. What plugins are you using?

jerry

On Thu, Dec 29, 2016 at 3:42 PM, volvoboy242@... [TekScopes] <
TekScopes@...> wrote:



I brought my old 7704 (non A) down from the attic the other day to find
that the CRT is dead.
I see a quick flash upon power down but, other then that, there is no
display.
I am guessing that the HV power supply has kicked the bucket.
I've done no diag since I know the voltage is high and my knowledge
doesn't extend to testing deadly secondary potential.
I've never had the covers off or had any work done (in 20 years).
Is this a serviceable part or do I need to source a known good power
supply?
I'm hoping it's something as simple as a re cap but this might be a bit
beyond me.


If any of you guys would Elmer me through this resto project, I'd be much
obliged!
No rush.


The only other scope I have is an old Velleman hand held that works
occasionally. I have some basic Ham survival tools.
I planned to gear up around this old main frame for radio alignments and
things of that nature.
Overkill I know.


Off topic; Also in my attic, there is an old pre war Allen B Dumont
"oscillograph" I played with when I was a kid.
I'd like to get that one working again some day. Just for fun.


Thanks
Mike
KD2MBG





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