Why should someone replace ALL the capacitors on old Tube eq

[Jim Mueller]

On Sat, 04 Feb 2017 18:53:53 -0600, oldschool wrote:

snip
I wonder why they dont make them both radial and axial? I'd think that
it's just a matter of rerouting the wires from the same innards.

No market. Everything now is built on PC boards and axial lead parts
take up too much room. Some axial lead parts are getting hard to get.

--
Jim Mueller wrongname@nospam.com

To get my real email address, replace wrongname with dadoheadman.
Then replace nospam with fastmail. Lastly, replace com with us.

 

[Jeff Liebermann]

On Sun, 05 Feb 2017 16:47:14 -0600, oldschool@tubes.com wrote:

>I am a lot more limited than you could imagine.

Agreed. You've given up before you've even started looking for a
solution. We have about 5 small and one large wireless ISP's in my
area that provide reliable service for your situation.

>My nearest neighbor is over a mile away.

Duz this neighbor have high speed internet? If so, a point to point
wireless link will get you internet.

>The nearest small town is 5 miles,

Can you "see" this small town from your rooftop? From a nearby
hilltop on your property? From the top of a tree or tower? If it has
high speed internet, as seems to be the case since the local coffee
shop does have it, you can establish a similar point to point wireless
link, or find a WISP to do it for you.

>the nearest large city is 55 miles.

That's a bit too far.

>I can not get a reliable cell phone signal here.

I live in a hilly area with lots of tall trees. Cellular coverage is
spotty in many places. So, I arrange to have someone install either a
nanocellular base station from the cellular provider, or a yagi
antenna on the roof pointed at the nearest cell site. (I gave up
tower and rooftop climbing about 15 years ago).

>There is no cable.

I've been mildly involved in several neighborhood campaigns to
"convince" the incumbent service provider to provide internet. If
they want a franchise from the city or county, they'll have to provide
service extension for those that are willing to pay for it. For
example:
<http://sccounty01.co.santa-cruz.ca.us/BDS/Govstream2/Bdsvdata/non_legacy_2.0/agendas/2007/20070626-386/PDF/068.pdf>
Get your neighborhood organized and be prepared to make some noises
when your local cable franchise is scheduled for renewal.

>The only way might be a satellite dish.

Only way? You're ignoring almost everything I previously suggested. I
suggest you do some research into wireless internet before declaring
your situation as hopeless. If you're lost, the email address in the
signature works. If you're desperate, so does the phone number. I
just hate to see anyone suffer with only dialup.

>And that would cost me at least $100 per month.

<http://www.exede.com>
$70/month after the teaser rate expires. No TV required. You can
possibly dump your phone service and switch to VoIP or use their phone
offering. You can get a similar prices from:
<https://www.hughesnet.com>
You'll need to buy satellite equipment and have an authorized
installer do the dish installation. Not sure of the prices.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

On Sun, 05 Feb 2017 19:18:58 -0800, Jeff Liebermann <jeffl@cruzio.com>
wrote:

On Sun, 05 Feb 2017 16:47:14 -0600, oldschool@tubes.com wrote:

I am a lot more limited than you could imagine.

Agreed. You've given up before you've even started looking for a
solution. We have about 5 small and one large wireless ISP's in my
area that provide reliable service for your situation.

My nearest neighbor is over a mile away.

Duz this neighbor have high speed internet? If so, a point to point
wireless link will get you internet.

No, they are Amish. Almost all my neighbors are Amish, except for one
very old retired farmer who I doubt even knows what the internet is.

The nearest small town is 5 miles,

Can you "see" this small town from your rooftop? From a nearby
hilltop on your property? From the top of a tree or tower? If it has
high speed internet, as seems to be the case since the local coffee
shop does have it, you can establish a similar point to point wireless
link, or find a WISP to do it for you.

I can not see it from my rooftop. There is a woods between my house and
the road. But even without the trees, I could not see the town, unless I
drive to the top of the hill (I live in a valley). My land ends at
almost the top of the hill, and I can probably see the town if I was to
climb a tree, or even stand on top of a full hay wagon full of hay. But
if I go another 50 or 70 feet higher (up the private road), I can easily
see town. (If this is not making sense, my driveway is a shared private
road. Between the county road and my farm, there is cropland. The
driveway is shared by myself and the farmer who owns that land. (He does
not live there, it's just crops). This roadway (driveway) is 2/3 of a
mile from the county road to my house. [and, yea, I have to plow the
whole friggin thing when it snows].

Yes, that town has high speed internet, and has public WIFI at the
library and at a fast food restaurant. As well as a lot of secured WIFI
signals (at businesses) that I can see on my laptop, when I am in town.
I regularly sit in the parking lot at that restaurant and use the WIFI
from my car, even when they are closed.

You lost me, when you started talking about "point to point wireless
link, and WISP".

the nearest large city is 55 miles.

That's a bit too far.

I can not get a reliable cell phone signal here.

I live in a hilly area with lots of tall trees. Cellular coverage is
spotty in many places. So, I arrange to have someone install either a
nanocellular base station from the cellular provider, or a yagi
antenna on the roof pointed at the nearest cell site. (I gave up
tower and rooftop climbing about 15 years ago).

I was looking at those cellphone boosters on ebay. Since I can get a
semi-usable signal on the roof, I thought about putting a yagi antenna
on my tv antenna tower and running that into the house. Part of my
problem is having a house with metal siding and roof.

There is no cable.

I've been mildly involved in several neighborhood campaigns to
"convince" the incumbent service provider to provide internet. If
they want a franchise from the city or county, they'll have to provide
service extension for those that are willing to pay for it. For
example:
http://sccounty01.co.santa-cruz.ca.us/BDS/Govstream2/Bdsvdata/non_
egacy_2.0/agendas/2007/20070626-386/PDF/068.pdf
Get your neighborhood organized and be prepared to make some noises
when your local cable franchise is scheduled for renewal.

Getting my Amish neighbors involved is not gonna happen

But I did sign a petition to get better cell service, after I raised
hell with some of the law enforcement people in the area. This occurred
about 20 months ago, when I saw a building on fire in another small town
nearby. I had a vehicle breakdown, and I was unable to call anyone for
help, because there is no cell signal at all in that town. So, while I'm
trying to fix my truck in cold weather, I notice a building on fire a
block away, and I cant even call the fire dept. This was during the
night, that town consists of about 100 population and no one drives up
that town's roads during the night. I finally woke someone up by banging
on doors, but by the time they called the fire dept, that building was a
total loss.

After I bitched like hell to the fire dept and other law enforcement,
that petition was created. It was passed around that town and other
nearby small towns. It was at the bars and public buildings, and got
around 250 signatures. The cell company in the area said they were
planning to build a new tower. (But from what I have heard from the
locals, they said that same thing 10 years ago). Nothing has changed.

The only way might be a satellite dish.

Only way? You're ignoring almost everything I previously suggested. I
suggest you do some research into wireless internet before declaring
your situation as hopeless. If you're lost, the email address in the
signature works. If you're desperate, so does the phone number. I
just hate to see anyone suffer with only dialup.

I hate having to cope with dialup, and worse yet, I can not establish a
decent connection using my US RObotics modem on any computer with
Windows XP. I can only connect using Window 98. I dont mind Win98, in
fact I like it, but the newest browser I can use if Firefox 3.x. At
least half the websites no longer work for me. So I mostly just use
usenet and email most of the time now, but some websites still work. If
they dont load after 10 minutes, I know they will never load.

I may be emailing you soon....

And that would cost me at least $100 per month.

http://www.exede.com
$70/month after the teaser rate expires. No TV required. You can
possibly dump your phone service and switch to VoIP or use their phone
offering. You can get a similar prices from:
https://www.hughesnet.com
You'll need to buy satellite equipment and have an authorized
installer do the dish installation. Not sure of the prices.

 

[Jeff Liebermann]

On Mon, 06 Feb 2017 04:21:27 -0600, oldschool@tubes.com wrote:

On Sun, 05 Feb 2017 19:18:58 -0800, Jeff Liebermann <jeffl@cruzio.com
wrote:
Duz this neighbor have high speed internet? If so, a point to point
wireless link will get you internet.

No, they are Amish. Almost all my neighbors are Amish, except for one
very old retired farmer who I doubt even knows what the internet is.

The modern equivalent of the Amish are people who claim to be
"electro-sensitive". A former lady friend was like that. I didn't
recognize the similarity until now. Thanks for the hint.

I can not see it from my rooftop. There is a woods between my house and
the road. But even without the trees, I could not see the town, unless I
drive to the top of the hill (I live in a valley). My land ends at
almost the top of the hill, and I can probably see the town if I was to
climb a tree, or even stand on top of a full hay wagon full of hay. But
if I go another 50 or 70 feet higher (up the private road), I can easily
see town.

I suspect that the aesthetics of a 50ft radio tower would be a show
stopper with the local planning department. However, if you can get
past that, you would end up with a radio tower with one end of a 2.4
or 5GHz wireless bridge with the other end in town with someone who
has high speed internet. Ideally, the backhaul from the tower to your
house would be buried cable or fiber, but can also be wireless. More
commonly, there's a 2nd wireless radio on the tower to distribute
internet to the neighbors, but that doesn't seem to be a requirement
here.

You lost me, when you started talking about "point to point wireless
link, and WISP".

WISP is "Wireless Internet Service Provider". It's just like a
conventional cable or telco service providers, but without the wires.
Instead of you building the tower and negotiating for sharing
broadband, the WISP does this for you.

Point to point wireless is basically a wireless bridge. I'll spare
you the details, but here's an example:
<http://www.ebay.com/itm/122182834424>
Think of it as an ethernet network extension cord without wires.

I was looking at those cellphone boosters on ebay. Since I can get a
semi-usable signal on the roof, I thought about putting a yagi antenna
on my tv antenna tower and running that into the house. Part of my
problem is having a house with metal siding and roof.

The legality of some of those boosters are questionable. They're also
expensive. I have one made by zBoost. Of course, I couldn't resist
tearing it apart and looking inside:
<http://802.11junk.com/jeffl/zBoost/>

The cell company in the area said they were
planning to build a new tower. (But from what I have heard from the
locals, they said that same thing 10 years ago). Nothing has changed.

I had a talk last year with the local Verizon engineer about new site
construction. He casually mentioned that they typically have about
2,000 new sites in progress at any time in Northern California. That
doesn't mean they're building these sites, just at some step in the
process, such as getting approvals from the local councils, boards,
and agencies. If they meet any resistance from citizens groups, that
site goes to the bottom of the list, and they continue working on
those where the locals want a cell site installed. He mentioned that
there were several sites where the locals offered to subsidize the
construction in order to get cellular service. I suspect your
cellular company meet some resistance from the local Amish, and just
walked away.

I hate having to cope with dialup, and worse yet, I can not establish a
decent connection using my US RObotics modem on any computer with
Windows XP.

I used that combination for many years until I was able to get DSL. It
should work. I wrote this during that era to test phone lines using
USR modems:
<http://members.cruzio.com/~jeffl/aty11/aty11.htm>

>I may be emailing you soon....

I was afraid that might happen.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[Chuck]

On 05 Feb 2017 22:54:02 GMT, Jim Mueller <wrongname@nospam.com> wrote:

On Sat, 04 Feb 2017 19:25:31 -0600, oldschool wrote:

On 05 Feb 2017 00:21:42 GMT, Jim Mueller <wrongname@nospam.com> wrote:

I think that there is a misunderstanding here. The statement to replace
all the capacitors actually means all the electrolytic and paper
capacitors. Usually ceramic and mica capacitors are still good and
nobody replaces those unless they are proven to be bad.

The paper capacitors in the IF and RF stages need to be replaced even if
the radio "works". Leaky capacitors change the voltages on the tubes
causing them to work at less than their best performance. Also, these
capacitors are used as supply bypasses and AVC filter capacitors. They
do not affect the alignment of the set; the ceramic and mica capacitors
may. Their value is not particularly critical; pick the closest modern
value.

I hear you.....

Consider the value issue. If the radio has a .05 uF, 20% capacitor in
it, its actual value can be anywhere from 0.04 uF to 0.06 uF. A modern
0.047 uF 10% capacitor can be between .0423 uF and 0.0517 uF. So the
0.047 uF capacitor can be closer to 0.05 uF than the old one marked with
that value.

OK. That makes sense...

As for life expectancy, there was a time in the late '50s and early '60s
when both paper and plastic film capacitors were used. The paper
capacitors I have from that period are universally bad while the plastic
film ones are almost always good. Plastic film has passed the test of
time.

As for what type of plastic film to use, polyester (AKA Mylar) is the
cheapest and has the poorest performance. But it is still better than
the paper capacitors of old so it is suitable for use just about
anywhere a paper capacitor was formerly used. Polycarbonate (no longer
made) and polypropylene are better but more expensive. Polystyrene
capacitors are also very good and inexpensive but are usually seen only
in small values

I see where this can get confusing. I'll consider the polyester (AKA
Mylar), but for the small cost difference, I'd probably prefer the best.
It looks like polypropylene would be that choice.

Do you have any brand names to recommend for these types?
(I will be buying online, there are no electronics stores around here).

and are frequently not seen at all. They also have the problem that
they melt at lower temperatures than other plastic capacitors and
solvents dissolve them. Still, within their limitations, they are
excellent.


Dont you mean they melt at a *HIGHER* temperature? I cant imagine how
something could melt at a low temp?

Upon reading a URL that somone posted on here, I see where the
audiophliles say that some caps have better sound quality, than others.
On a SW radio, I'm not really looking for "precision sound", but more so
for best performance from the signal coming from the antenna to the
speaker. And while some (or most) of these newer types of caps are made
to be used with modern gear, containing semiconductors, which are the
best choice for old tube stuff. I would think that the caps should mimic
the old paper caps, because that is what these circuits were designed to
use. I know the values of caps are the capcitance (in MF or MMF) and the
voltage. But I know there are other factors that I know nothing about.
Someone mentioned tempco (is that what I read?) in another message in
this thread. What the heck is that?

Either way, I do believe the caps should be similar to the original ones
to work properly. Just made from better materials.


--
Jim Mueller wrongname@nospam.com
No, polystyrene capacitors have LOWER maximum temperature capability than
most other capacitors; that is one of their limitations. But they have
very low leakage, last forever if not mistreated, and are cheap.

Tempco is shorthand for temperature coefficient. It describes how much
the capacitance changes as temperature changes. Some capacitors change
very little (for example C0G ceramics), others change a LOT (Z5U
ceramics).

The 470pf polystyrene capacitors used in the mpx circuits of many
receivers in the 1970s used to fail all the time.

---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus

 

[Benderthe.evilrobot]

<oldschool@tubes.com> wrote in message
news:957f9chh7874ipnges7e90a80v5idod4k5@4ax.com...

On Sun, 5 Feb 2017 19:14:06 -0000, "Benderthe.evilrobot"
Benderthe.evilrobot@virginmedia.com> wrote:


I know the dry 'lytics were better, I have to ask what came before these
wet ones with the vent hole? I really dont know...

When I was a kid, I liked taking old radios to bits. A mains reservoir
electrolytic I "autopsied" had a centre electrode that was sort of like a
curvy column (for maximum surface area) up the middle, the can was the
other
electrode, it was completely filled with electrolyte. Another old radio
had
a compartment under the one that housed the chassis, it contained a huge
slab flat wound paper capacitor - it must've weighed at least 7lb.

That sort of thing I never encountered. That must have been REALLY old!
Most of the stuff I worked on, was mid 40s thru 60s. I had a few of
those old wooden radios that stood about 40" tall and had a round top.
Those were some of the harder ones I tried to work on, and the tubes
were unusual. I know those were the ones that had those wet caps with
the top vent hole. I also recall that the speaker magnet was an
electro-magnet and was also used as a choke for the power supply. Those
were some of the oldest things I worked on.

AFAICR: the one with the paper reservoir cap was a regen.

 

[Benderthe.evilrobot]

"Jim Mueller" <wrongname@nospam.com> wrote in message
news:5897ad0a$0$59611$c3e8da3$460562f1@news.astraweb.com...

On Sat, 04 Feb 2017 19:25:31 -0600, oldschool wrote:

On 05 Feb 2017 00:21:42 GMT, Jim Mueller <wrongname@nospam.com> wrote:

I think that there is a misunderstanding here. The statement to replace
all the capacitors actually means all the electrolytic and paper
capacitors. Usually ceramic and mica capacitors are still good and
nobody replaces those unless they are proven to be bad.

The paper capacitors in the IF and RF stages need to be replaced even if
the radio "works". Leaky capacitors change the voltages on the tubes
causing them to work at less than their best performance. Also, these
capacitors are used as supply bypasses and AVC filter capacitors. They
do not affect the alignment of the set; the ceramic and mica capacitors
may. Their value is not particularly critical; pick the closest modern
value.

I hear you.....

Consider the value issue. If the radio has a .05 uF, 20% capacitor in
it, its actual value can be anywhere from 0.04 uF to 0.06 uF. A modern
0.047 uF 10% capacitor can be between .0423 uF and 0.0517 uF. So the
0.047 uF capacitor can be closer to 0.05 uF than the old one marked with
that value.

OK. That makes sense...

As for life expectancy, there was a time in the late '50s and early '60s
when both paper and plastic film capacitors were used. The paper
capacitors I have from that period are universally bad while the plastic
film ones are almost always good. Plastic film has passed the test of
time.

As for what type of plastic film to use, polyester (AKA Mylar) is the
cheapest and has the poorest performance. But it is still better than
the paper capacitors of old so it is suitable for use just about
anywhere a paper capacitor was formerly used. Polycarbonate (no longer
made) and polypropylene are better but more expensive. Polystyrene
capacitors are also very good and inexpensive but are usually seen only
in small values

I see where this can get confusing. I'll consider the polyester (AKA
Mylar), but for the small cost difference, I'd probably prefer the best.
It looks like polypropylene would be that choice.

Do you have any brand names to recommend for these types?
(I will be buying online, there are no electronics stores around here).

and are frequently not seen at all. They also have the problem that
they melt at lower temperatures than other plastic capacitors and
solvents dissolve them. Still, within their limitations, they are
excellent.


Dont you mean they melt at a *HIGHER* temperature? I cant imagine how
something could melt at a low temp?

Upon reading a URL that somone posted on here, I see where the
audiophliles say that some caps have better sound quality, than others.
On a SW radio, I'm not really looking for "precision sound", but more so
for best performance from the signal coming from the antenna to the
speaker. And while some (or most) of these newer types of caps are made
to be used with modern gear, containing semiconductors, which are the
best choice for old tube stuff. I would think that the caps should mimic
the old paper caps, because that is what these circuits were designed to
use. I know the values of caps are the capcitance (in MF or MMF) and the
voltage. But I know there are other factors that I know nothing about.
Someone mentioned tempco (is that what I read?) in another message in
this thread. What the heck is that?

Either way, I do believe the caps should be similar to the original ones
to work properly. Just made from better materials.


--
Jim Mueller wrongname@nospam.com
No, polystyrene capacitors have LOWER maximum temperature capability than
most other capacitors; that is one of their limitations. But they have
very low leakage, last forever if not mistreated, and are cheap.

Apparently the tempco of polystyrene is a good match for pot cores.

I've seen polystyrene crack/craze with age - I didn't investigate whether
performance was impaired.

Polystyrene is pretty much the most vulnerable to solvents there is -
fortunately, most de fluxing solvents were banned to protect the ozone
layer.

 

[Spare Change]

On Feb 2, 2017, oldschool@tubes.com wrote
(in article<32779ctsu0qa604ak706qamu4fft571fj8@4ax.com&gt:

> Why should someone replace ALL the capacitors on old Tube equipment?

<https://en.wikipedia.org/wiki/Glowing_plate#Common_Occurrences>

Several causes listed are caused by shorted or leaking capacitors. It’s a
tube killer.

 

On Mon, 06 Feb 2017 21:54:54 -0800, Spare Change
<noncompliant@notcompliant.zgq> wrote:

On Feb 2, 2017, oldschool@tubes.com wrote
(in article<32779ctsu0qa604ak706qamu4fft571fj8@4ax.com&gt:

Why should someone replace ALL the capacitors on old Tube equipment?

https://en.wikipedia.org/wiki/Glowing_plate#Common_Occurrences

Several causes listed are caused by shorted or leaking capacitors. It’s a
tube killer.
A;so the sinle largest killer of hard to replace power transformers.

 

[Benderthe.evilrobot]

<clare@snyder.on.ca> wrote in message
news:th7k9cl63nqp5gaql8pfsfp6nu7dpvuoss@4ax.com...

On Mon, 06 Feb 2017 21:54:54 -0800, Spare Change
noncompliant@notcompliant.zgq> wrote:

On Feb 2, 2017, oldschool@tubes.com wrote
(in article<32779ctsu0qa604ak706qamu4fft571fj8@4ax.com&gt:

Why should someone replace ALL the capacitors on old Tube equipment?

https://en.wikipedia.org/wiki/Glowing_plate#Common_Occurrences

Several causes listed are caused by shorted or leaking capacitors. It's a
tube killer.
A;so the sinle largest killer of hard to replace power transformers.

Not to mention a leaky grid coupling cap can pass a large DC voltage from
the plate of the previous stage. I've seen tubes that got so hot the glass
melted and the vacuum wrapped it round the internal structure like cling
film.

If it happens in Ham gear - the PA tubes are seriously expensive.

 

On Tue, 07 Feb 2017 14:22:09 -0500, clare@snyder.on.ca wrote:

On Mon, 06 Feb 2017 21:54:54 -0800, Spare Change
noncompliant@notcompliant.zgq> wrote:

https://en.wikipedia.org/wiki/Glowing_plate#Common_Occurrences

Several causes listed are caused by shorted or leaking capacitors. It’s a
tube killer.
A;so the sinle largest killer of hard to replace power transformers.

I have put fuses on the secondaries of the power transformer on some
high powered amplifiers. (On the high voltage leads). That protects the
xformer as well as other parts. Line fuses on the primary are not enough
in my opinion.

 

[Michael Black]

On Tue, 7 Feb 2017, Benderthe.evilrobot wrote:

clare@snyder.on.ca> wrote in message
news:th7k9cl63nqp5gaql8pfsfp6nu7dpvuoss@4ax.com...
On Mon, 06 Feb 2017 21:54:54 -0800, Spare Change
noncompliant@notcompliant.zgq> wrote:

On Feb 2, 2017, oldschool@tubes.com wrote
(in article<32779ctsu0qa604ak706qamu4fft571fj8@4ax.com&gt:

Why should someone replace ALL the capacitors on old Tube equipment?

https://en.wikipedia.org/wiki/Glowing_plate#Common_Occurrences

Several causes listed are caused by shorted or leaking capacitors. It's a
tube killer.
A;so the sinle largest killer of hard to replace power transformers.


Not to mention a leaky grid coupling cap can pass a large DC voltage from the
plate of the previous stage. I've seen tubes that got so hot the glass melted
and the vacuum wrapped it round the internal structure like cling film.

If it happens in Ham gear - the PA tubes are seriously expensive.

There are stories of Collins receivers, I forget which model, where the
capacitor feeding the mechanical filter can go bad, and the result is
a ruined mechanical filter, it can't handle the DC going through it.

SO that's the sort of thing knowledge that is out there for people coming
to an old receiver for the first time.

Michael

 

On Tue, 7 Feb 2017 16:11:28 -0500, Michael Black <et472@ncf.ca> wrote:

There are stories of Collins receivers, I forget which model, where the
capacitor feeding the mechanical filter can go bad, and the result is
a ruined mechanical filter, it can't handle the DC going through it.

SO that's the sort of thing knowledge that is out there for people coming
to an old receiver for the first time.

Michael

What is a " mechanical filter"?

 

[Benderthe.evilrobot]

<oldschool@tubes.com> wrote in message
news:im3n9c5c1ogspq5fk6nb93htrel23fhn4u@4ax.com...

On Tue, 7 Feb 2017 16:11:28 -0500, Michael Black <et472@ncf.ca> wrote:

There are stories of Collins receivers, I forget which model, where the
capacitor feeding the mechanical filter can go bad, and the result is
a ruined mechanical filter, it can't handle the DC going through it.

SO that's the sort of thing knowledge that is out there for people coming
to an old receiver for the first time.

Michael


What is a " mechanical filter"?

Pretty much what the name says it is.

Usually a row of disks with a mechanical resonant frequency, AFAIK: the
transducers at each end were usually inductive, but I believe there were
piezo types.

At one time they were the most common type of IF selectivity in Ham radio
and other communications gear.

 

[Michael Black]

On Wed, 8 Feb 2017, oldschool@tubes.com wrote:

On Tue, 7 Feb 2017 16:11:28 -0500, Michael Black <et472@ncf.ca> wrote:

There are stories of Collins receivers, I forget which model, where the
capacitor feeding the mechanical filter can go bad, and the result is
a ruined mechanical filter, it can't handle the DC going through it.

SO that's the sort of thing knowledge that is out there for people coming
to an old receiver for the first time.

Michael


What is a " mechanical filter"?

It provide selectivity in the receiver. It goes in the IF, at 455KHz or
sometimes 500KHz or even I have one at 250KHz. Generally for narrow
selctivity, like for SSB or CW. Kind of expensive, but even more so
decades later when they are no longer being made, and finding a specific
model may not be so easy. So if the capacitor goes, it can be expensive
to remedy.

Michael

 

[Foxs Mercantile]

On 2/8/2017 3:34 PM, oldschool@tubes.com wrote:

What is a " mechanical filter"?

<http://www.wa3key.com/filters.html>



--
Jeff-1.0
wa6fwi
http://www.foxsmercantile.com

 

[Michael Black]

On Wed, 8 Feb 2017, Benderthe.evilrobot wrote:

oldschool@tubes.com> wrote in message
news:im3n9c5c1ogspq5fk6nb93htrel23fhn4u@4ax.com...
On Tue, 7 Feb 2017 16:11:28 -0500, Michael Black <et472@ncf.ca> wrote:

There are stories of Collins receivers, I forget which model, where the
capacitor feeding the mechanical filter can go bad, and the result is
a ruined mechanical filter, it can't handle the DC going through it.

SO that's the sort of thing knowledge that is out there for people coming
to an old receiver for the first time.

Michael


What is a " mechanical filter"?

Pretty much what the name says it is.

Usually a row of disks with a mechanical resonant frequency, AFAIK: the
transducers at each end were usually inductive, but I believe there were
piezo types.

At one time they were the most common type of IF selectivity in Ham radio and
other communications gear.

I think that's debateable.

For a long time IF transformers were "good enough" and a single crystal
filter was the step up. Those were common until the SSB age in the
mid-fifties, when mechanical filters became somewhat common, but
multi-crystal filters also came along at that point, and within a few
years the shift was to a crystal filter in the HF range.

Collins used mechanical filters in their receivers, but not all of them.
Some CB sets used them, helped in part because some company in Japan made
a cheaper mechanical filter, but that wsa sort of a blip, ceramic filters
ame along soon after and they were cheaper. Upper end equipment tended to
use mechanical filters right to the end, when Collins stopped making them
a few years ago, the implied move to software radios taking over.

Some ham SSB sets used them, and I had an RCA SSB Carphone that had a
250KHz mechanical filter.

But lots of other equipment used other things rather than mechanical
filters.

Michael

 

[Foxs Mercantile]

On 2/9/2017 2:08 PM, Michael Black wrote:

Collins used mechanical filters in their receivers, but not all
of them.

Collins introduced them in the 75A-4 and 51J-4 receivers back in
the early '50s.

Drake used a 50 KHz IF and tuned LC filters in their receivers up
until the mid '60s.

The alternative to Collins mechanical filters were multi-pole crystal
filters. Which was what everyone else was using.

One of the stranger things to come across was Henry Radio offered a
kit to install a Collins mechanical filter in the Drake 2B receiver.

Absolutely pointless, but it allowed you to win "dick waving" contests.




--
Jeff-1.0
wa6fwi
http://www.foxsmercantile.com

 

"I would like to find out what problems are specific to the Hallicrafters
SX-99. Where is a good place to look? "

Inside the Hallicrafters SX-99 would be my first guess.

>"
I'd be interested in which of the old caps were known to have "issues".
or to fail. Sure, they are all old (in any tube equipmnent), and they
are paper caps, which are no longer made, but I'm sure some brands were
better or worse than others. "

The bad caps in old tube radios have already lasted longer than any normal engineer would plan for. The people who made those caps, by default, made them to last forever. so much for that. Of course as you know some of them can be reformed. Not that I would trust that in a heart/lung machine, but maybe for a table radio.

>"(snipped the BS about older caps) Paper caps
seem to have passed the test of time. We wont know if these newer
materials pass the test of time or not, until we get there. "

We do know, and they don't. Newer capacitors have failure modes that'll put hair on your chest, curl it and take it off in one fell swoop.

I worked on bigscreen TVs, which were a fad here in the US and I made alot of money off of it because nobody else could understand it.

Well there were YEARS of Mitsubishi product out there with defective caps. someone (Rubycon ?) stole a formula for the electrolyte which was not yet perfected. but they made the caps and they had higher density, which means capacitance and voltage ratings in a smaller size. Thatis what determines the value of an electrolytic capacitor on the market. You got ESR, ESL, intolerance to heat as minus, microfarads and voltage are the plus. And the smaller the better.

You have to think outside the box to really understand this, electrolytes are not necessarily insulators. In fact when they leaked out on the board of $3,500 Mitsubishi TVs they caused leakage paths on the PC board.

Forget air and vacuum as an electrolyte, they are actually not. The electrolyte is more like the acid in your car battery.

Anyway, I have done alot of service and streamlined many the process. If you look at the damn schematic you can tell which caps are stressed worse and you know to replace them. New caps have hours before MTF based on ripple current. Well some do. Elcheapo ones do not give specs because they are so dismal, like the THD rating of a loudspeaker, they could never sell amps with 0.03 % distortion if people knew that actually good speakers usually have 5 % or more at normal listening levels. Of course some are lower, go have a look at the Martin Logan website for that, and if that doesn't make your wallet hurt go find some Quad ESL-63s.

In other words some things matter, others do not. Like I am about to work on a Pioneer SX-737. I am NOT replacing all the caps, and BTW, those big ones in the power supply, when they are bulging they are not necessarily bad. I am replacoing a bunch of PNP transistors because they were prone to failure ad could damage other components. there are a few caps I am going to change and I will (upon request) supply the schematic and my professional judgement as to why these caps get changed and why the others do not. If you understand the circuit you realize that some of these caps are nowhere near the audio path and do not affect the sound. If they pose a reliability problem that is different.

Now, you brought up old caps, and upon that I would like to expound a bit. A couple few years ago my sister's PC monitor crapped out. I had already been working on flatscrteen TVs so I knew the deal. I found a bank of caps, which is usually what they are, all bad. See, in business toward the end I did not replace all kinds of caps, I just bridged one in and when it worked I knew the caps would fix it. this was my job.

But this was far from professional. Her power supply of course worked up in the hundreds of KHz. I had no caps at the house but a thirty years old one.. Originally in the circuit there was a bank of 1,000 uF @ I think 35 volts, I only had 25s.

I took and old 100 uF @ 160 volts and stuck it in there and it worked. Think about it, a good cap, 100 KHz ? /Of course it worked.

I told her I really did not have the right part right now so be ready for it to fail, and I will order the right part.

It has been running for over three years now.

These engineers are idiots, they use banks of caps of poor quality instead of just a few good ones. But then they need to design next year's product you are forced to buy because this one failed. Like the government, is it complicity or incompetence ? To me it does not matter, they need for some heads to roll. They are wrecking the fucking planet.

Guy on here talking about Taiwan or whatever dog country saying it is a dumping ground for our junk electronics. GOOD ! That is where the garbage came from in the first place ! Take it back. In fact take it all back. I want to go back to where I have only six channels on the TV. I shit you not.

And I want a table radio in the kitchen.

Know what ? Off to eBay, or better yet Craigslist.

 

[Benderthe.evilrobot]

<jurb6006@gmail.com> wrote in message
news:44a416e8-4d8f-442b-8f9d-10c7dbc7c679@googlegroups.com...

"I would like to find out what problems are specific to the Hallicrafters
SX-99. Where is a good place to look? "

Inside the Hallicrafters SX-99 would be my first guess.

"
I'd be interested in which of the old caps were known to have "issues".
or to fail. Sure, they are all old (in any tube equipmnent), and they
are paper caps, which are no longer made, but I'm sure some brands were
better or worse than others. "

Some brands gained notoriety simply because there were a lot more of their
parts out there in the field.

Its probably more productive to identify suspect dielectric types than
brands.

Those were the materials they had back then, and some of them don't last
forever in the heat around tubes.