Reed relays for a sick AA501A


Eric
 

I have a sick AA501A that I am trying to bring back from the dead. I am wondering if anyone knows of any replacement reed relays. The existing part is Tek number 148-0134-00. The part number on the part is EAC 2A05X250biaa. If there is not a supply of these or if these are troublesome parts I am looking at a possible modern replacement. Coto 2332 Mouser part 816-2332-05-010 https://www.mouser.com/ProductDetail/816-2332-05-010. It will need some adaptation of course but it does look like it will fit physically.

Eric


 

Hi Eric,
Reed relays are conceptually simple devices in electrical and in mechanical terms. There are only two parts - the reed- and a coil wrapped around it. The reeds come in two types: the more common ones have normally open contacts. The less common ones have normally closed contacts. The coils are designed to operate on a specific voltage like +12VDC, +15VDC, or +28VDC. Coil resistance is dependent on the operating voltage.

I have a bunch of the glass reeds I picked up somewhere 50 years ago and every few years I find a use for one of them. The reeds themselves are cheap and probably available on eBay for a few dollars for a handful of them.
The only thing that matters is the diameter of the glass envelope surrounding the reed and the length from one end to the other of the contact pins. It is good to have an assortment of sizes to work with.
A bad reed can almost always be slid out of the coil and replaced with one that is approximately the same size. You can't bend the leads (even slightly) or that will break the glass. But you can cut them down to size.

You can hear the reed make and break contact (if you are in a quiet room) to determine the reed closes BEFORE the proper voltage is applied to the coil. For instance, a 12V reed relay should close when you apply about 8V to it.

Dennis Tillman W7pF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Eric
Sent: Saturday, April 03, 2021 8:25 PM
To: TekScopes@groups.io
Subject: [TekScopes] Reed relays for a sick AA501A

I have a sick AA501A that I am trying to bring back from the dead. I am wondering if anyone knows of any replacement reed relays. The existing part is Tek number 148-0134-00. The part number on the part is EAC 2A05X250biaa. If there is not a supply of these or if these are troublesome parts I am looking at a possible modern replacement. Coto 2332 Mouser part 816-2332-05-010 https://www.mouser.com/ProductDetail/816-2332-05-010. It will need some adaptation of course but it does look like it will fit physically.

Eric







--
Dennis Tillman W7pF
TekScopes Moderator


Eric
 

Dennis,
Thanks for the info I did not know whey were this easy to rebuild. Unfortunately these particular ones are sealed on the ends molded plastic caps for the lead wires. There are 5 relays in the 501A that handle the high voltage ranges. I am having issues with 60, 20 and 6. With them also causing some havoc on auto range as well. When I have a situation where they are working the unit locks in and works as expected. These are supposed to have a 5Vdc coil but when I was testing one with a square wave it would not trip till about 8Vdc. In the 501A all the relays are energized by the output of a hex inverter then they are allowed to fall low and open. These are energized = Closed I believe. The odd thing about these is they are DP ST relays as they cover + and - inputs with the same relay. These are silver packages with 4 legs on one side and 2 on the other. 2 outer legs are for the coil the 2 inner ones are for the reeds running straight through.

This 501A is worth saving especially this one as it has option one the intermodulation measurements. Of course it will need a full cal after words.

Being double pole has caused me a fair bit of grief in the replacement department.

Eric

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Dennis Tillman W7pF
Sent: Sunday, April 4, 2021 12:57 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Reed relays for a sick AA501A

Hi Eric,
Reed relays are conceptually simple devices in electrical and in mechanical terms. There are only two parts - the reed- and a coil wrapped around it. The reeds come in two types: the more common ones have normally open contacts. The less common ones have normally closed contacts. The coils are designed to operate on a specific voltage like +12VDC, +15VDC, or +28VDC. Coil resistance is dependent on the operating voltage.

I have a bunch of the glass reeds I picked up somewhere 50 years ago and every few years I find a use for one of them. The reeds themselves are cheap and probably available on eBay for a few dollars for a handful of them.
The only thing that matters is the diameter of the glass envelope surrounding the reed and the length from one end to the other of the contact pins. It is good to have an assortment of sizes to work with.
A bad reed can almost always be slid out of the coil and replaced with one that is approximately the same size. You can't bend the leads (even slightly) or that will break the glass. But you can cut them down to size.

You can hear the reed make and break contact (if you are in a quiet room) to determine the reed closes BEFORE the proper voltage is applied to the coil. For instance, a 12V reed relay should close when you apply about 8V to it.

Dennis Tillman W7pF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Eric
Sent: Saturday, April 03, 2021 8:25 PM
To: TekScopes@groups.io
Subject: [TekScopes] Reed relays for a sick AA501A

I have a sick AA501A that I am trying to bring back from the dead. I am wondering if anyone knows of any replacement reed relays. The existing part is Tek number 148-0134-00. The part number on the part is EAC 2A05X250biaa. If there is not a supply of these or if these are troublesome parts I am looking at a possible modern replacement. Coto 2332 Mouser part 816-2332-05-010 https://www.mouser.com/ProductDetail/816-2332-05-010. It will need some adaptation of course but it does look like it will fit physically.

Eric







--
Dennis Tillman W7pF
TekScopes Moderator


 

Hi Eric,
I don't have an AA501A. I have an AA5001A which also uses the same relays. Unfortunately I can't get to the board they are on without disassembling the plugin.
I looked at the COTO relay and they look like a good choice electrically. Mechanical issues like location and spacing of the leads will probably be the main issue you have to deal with. The best approach might be to mount the Coto relays "dead-bug" style with their leads facing up and away from the PC Board. A small piece of double-back tape can be used to anchor the relay to the PCB. Then you can wire short jumpers to go from each Coto lead to the correct hole in the PCB.
Dennis Tillman W7pF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Eric
Sent: Sunday, April 04, 2021 12:28 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Reed relays for a sick AA501A

Dennis,
Thanks for the info I did not know whey were this easy to rebuild. Unfortunately these particular ones are sealed on the ends molded plastic caps for the lead wires. There are 5 relays in the 501A that handle the high voltage ranges. I am having issues with 60, 20 and 6. With them also causing some havoc on auto range as well. When I have a situation where they are working the unit locks in and works as expected. These are supposed to have a 5Vdc coil but when I was testing one with a square wave it would not trip till about 8Vdc. In the 501A all the relays are energized by the output of a hex inverter then they are allowed to fall low and open. These are energized = Closed I believe. The odd thing about these is they are DP ST relays as they cover + and - inputs with the same relay. These are silver packages with 4 legs on one side and 2 on the other. 2 outer legs are for the coil the 2 inner ones are for the reeds running straight through.

This 501A is worth saving especially this one as it has option one the intermodulation measurements. Of course it will need a full cal after words.

Being double pole has caused me a fair bit of grief in the replacement department.

Eric

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Dennis Tillman W7pF
Sent: Sunday, April 4, 2021 12:57 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Reed relays for a sick AA501A

Hi Eric,
Reed relays are conceptually simple devices in electrical and in mechanical terms. There are only two parts - the reed- and a coil wrapped around it. The reeds come in two types: the more common ones have normally open contacts. The less common ones have normally closed contacts. The coils are designed to operate on a specific voltage like +12VDC, +15VDC, or +28VDC. Coil resistance is dependent on the operating voltage.

I have a bunch of the glass reeds I picked up somewhere 50 years ago and every few years I find a use for one of them. The reeds themselves are cheap and probably available on eBay for a few dollars for a handful of them.
The only thing that matters is the diameter of the glass envelope surrounding the reed and the length from one end to the other of the contact pins. It is good to have an assortment of sizes to work with.
A bad reed can almost always be slid out of the coil and replaced with one that is approximately the same size. You can't bend the leads (even slightly) or that will break the glass. But you can cut them down to size.

You can hear the reed make and break contact (if you are in a quiet room) to determine the reed closes BEFORE the proper voltage is applied to the coil. For instance, a 12V reed relay should close when you apply about 8V to it.

Dennis Tillman W7pF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Eric
Sent: Saturday, April 03, 2021 8:25 PM
To: TekScopes@groups.io
Subject: [TekScopes] Reed relays for a sick AA501A

I have a sick AA501A that I am trying to bring back from the dead. I am wondering if anyone knows of any replacement reed relays. The existing part is Tek number 148-0134-00. The part number on the part is EAC 2A05X250biaa. If there is not a supply of these or if these are troublesome parts I am looking at a possible modern replacement. Coto 2332 Mouser part 816-2332-05-010 https://www.mouser.com/ProductDetail/816-2332-05-010. It will need some adaptation of course but it does look like it will fit physically.

Eric







--
Dennis Tillman W7pF
TekScopes Moderator













--
Dennis Tillman W7pF
TekScopes Moderator


Eric
 

Dennis,
I have something coming for the mechanical and pin out issues. I will let everyone know how it goes well. I should know more by the end of the week.

Eric

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Dennis Tillman W7pF
Sent: Sunday, April 4, 2021 4:23 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Reed relays for a sick AA501A

Hi Eric,
I don't have an AA501A. I have an AA5001A which also uses the same relays. Unfortunately I can't get to the board they are on without disassembling the plugin.
I looked at the COTO relay and they look like a good choice electrically. Mechanical issues like location and spacing of the leads will probably be the main issue you have to deal with. The best approach might be to mount the Coto relays "dead-bug" style with their leads facing up and away from the PC Board. A small piece of double-back tape can be used to anchor the relay to the PCB. Then you can wire short jumpers to go from each Coto lead to the correct hole in the PCB.
Dennis Tillman W7pF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Eric
Sent: Sunday, April 04, 2021 12:28 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Reed relays for a sick AA501A

Dennis,
Thanks for the info I did not know whey were this easy to rebuild. Unfortunately these particular ones are sealed on the ends molded plastic caps for the lead wires. There are 5 relays in the 501A that handle the high voltage ranges. I am having issues with 60, 20 and 6. With them also causing some havoc on auto range as well. When I have a situation where they are working the unit locks in and works as expected. These are supposed to have a 5Vdc coil but when I was testing one with a square wave it would not trip till about 8Vdc. In the 501A all the relays are energized by the output of a hex inverter then they are allowed to fall low and open. These are energized = Closed I believe. The odd thing about these is they are DP ST relays as they cover + and - inputs with the same relay. These are silver packages with 4 legs on one side and 2 on the other. 2 outer legs are for the coil the 2 inner ones are for the reeds running straight through.

This 501A is worth saving especially this one as it has option one the intermodulation measurements. Of course it will need a full cal after words.

Being double pole has caused me a fair bit of grief in the replacement department.

Eric

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Dennis Tillman W7pF
Sent: Sunday, April 4, 2021 12:57 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Reed relays for a sick AA501A

Hi Eric,
Reed relays are conceptually simple devices in electrical and in mechanical terms. There are only two parts - the reed- and a coil wrapped around it. The reeds come in two types: the more common ones have normally open contacts. The less common ones have normally closed contacts. The coils are designed to operate on a specific voltage like +12VDC, +15VDC, or +28VDC. Coil resistance is dependent on the operating voltage.

I have a bunch of the glass reeds I picked up somewhere 50 years ago and every few years I find a use for one of them. The reeds themselves are cheap and probably available on eBay for a few dollars for a handful of them.
The only thing that matters is the diameter of the glass envelope surrounding the reed and the length from one end to the other of the contact pins. It is good to have an assortment of sizes to work with.
A bad reed can almost always be slid out of the coil and replaced with one that is approximately the same size. You can't bend the leads (even slightly) or that will break the glass. But you can cut them down to size.

You can hear the reed make and break contact (if you are in a quiet room) to determine the reed closes BEFORE the proper voltage is applied to the coil. For instance, a 12V reed relay should close when you apply about 8V to it.

Dennis Tillman W7pF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Eric
Sent: Saturday, April 03, 2021 8:25 PM
To: TekScopes@groups.io
Subject: [TekScopes] Reed relays for a sick AA501A

I have a sick AA501A that I am trying to bring back from the dead. I am wondering if anyone knows of any replacement reed relays. The existing part is Tek number 148-0134-00. The part number on the part is EAC 2A05X250biaa. If there is not a supply of these or if these are troublesome parts I am looking at a possible modern replacement. Coto 2332 Mouser part 816-2332-05-010 https://www.mouser.com/ProductDetail/816-2332-05-010. It will need some adaptation of course but it does look like it will fit physically.

Eric







--
Dennis Tillman W7pF
TekScopes Moderator













--
Dennis Tillman W7pF
TekScopes Moderator


Jan Weber
 

White browsing some paper catalogues I found a "microscopic" reed relay
measuring 8.6 x 4.4 x 3.6 mm , which might be useful as a replacement for
these failure-prone Tektronix subminiature devices.

The part number is CRR-05 , made by Standex/Meder.

This is a link to the datasheet:
https://standexelectronics.com/viewer/pdfjs/web/viewer.php?file=https%3A%2F%2Fstandexelectronics.com%2Fwp-content%2Fuploads%2F2015%2F03%2FCRR_V02.pdf

I've only found a SPST variant.

Regards,

Jan

Eric <ericsp@gmail.com> schrieb am Mo., 5. Apr. 2021, 15:52:

Dennis,
I have something coming for the mechanical and pin out issues. I
will let everyone know how it goes well. I should know more by the end of
the week.

Eric

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Dennis
Tillman W7pF
Sent: Sunday, April 4, 2021 4:23 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Reed relays for a sick AA501A

Hi Eric,
I don't have an AA501A. I have an AA5001A which also uses the same relays.
Unfortunately I can't get to the board they are on without disassembling
the plugin.
I looked at the COTO relay and they look like a good choice electrically.
Mechanical issues like location and spacing of the leads will probably be
the main issue you have to deal with. The best approach might be to mount
the Coto relays "dead-bug" style with their leads facing up and away from
the PC Board. A small piece of double-back tape can be used to anchor the
relay to the PCB. Then you can wire short jumpers to go from each Coto lead
to the correct hole in the PCB.
Dennis Tillman W7pF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Eric
Sent: Sunday, April 04, 2021 12:28 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Reed relays for a sick AA501A

Dennis,
Thanks for the info I did not know whey were this easy to rebuild.
Unfortunately these particular ones are sealed on the ends molded plastic
caps for the lead wires. There are 5 relays in the 501A that handle the
high voltage ranges. I am having issues with 60, 20 and 6. With them also
causing some havoc on auto range as well. When I have a situation where
they are working the unit locks in and works as expected. These are
supposed to have a 5Vdc coil but when I was testing one with a square wave
it would not trip till about 8Vdc. In the 501A all the relays are energized
by the output of a hex inverter then they are allowed to fall low and open.
These are energized = Closed I believe. The odd thing about these is they
are DP ST relays as they cover + and - inputs with the same relay. These
are silver packages with 4 legs on one side and 2 on the other. 2 outer
legs are for the coil the 2 inner ones are for the reeds running straight
through.

This 501A is worth saving especially this one as it has option one the
intermodulation measurements. Of course it will need a full cal after
words.

Being double pole has caused me a fair bit of grief in the replacement
department.

Eric

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Dennis
Tillman W7pF
Sent: Sunday, April 4, 2021 12:57 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Reed relays for a sick AA501A

Hi Eric,
Reed relays are conceptually simple devices in electrical and in
mechanical terms. There are only two parts - the reed- and a coil wrapped
around it. The reeds come in two types: the more common ones have normally
open contacts. The less common ones have normally closed contacts. The
coils are designed to operate on a specific voltage like +12VDC, +15VDC, or
+28VDC. Coil resistance is dependent on the operating voltage.

I have a bunch of the glass reeds I picked up somewhere 50 years ago and
every few years I find a use for one of them. The reeds themselves are
cheap and probably available on eBay for a few dollars for a handful of
them.
The only thing that matters is the diameter of the glass envelope
surrounding the reed and the length from one end to the other of the
contact pins. It is good to have an assortment of sizes to work with.
A bad reed can almost always be slid out of the coil and replaced with one
that is approximately the same size. You can't bend the leads (even
slightly) or that will break the glass. But you can cut them down to size.

You can hear the reed make and break contact (if you are in a quiet room)
to determine the reed closes BEFORE the proper voltage is applied to the
coil. For instance, a 12V reed relay should close when you apply about 8V
to it.

Dennis Tillman W7pF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Eric
Sent: Saturday, April 03, 2021 8:25 PM
To: TekScopes@groups.io
Subject: [TekScopes] Reed relays for a sick AA501A

I have a sick AA501A that I am trying to bring back from the dead. I am
wondering if anyone knows of any replacement reed relays. The existing part
is Tek number 148-0134-00. The part number on the part is EAC 2A05X250biaa.
If there is not a supply of these or if these are troublesome parts I am
looking at a possible modern replacement. Coto 2332 Mouser part
816-2332-05-010 https://www.mouser.com/ProductDetail/816-2332-05-010. It
will need some adaptation of course but it does look like it will fit
physically.

Eric







--
Dennis Tillman W7pF
TekScopes Moderator













--
Dennis Tillman W7pF
TekScopes Moderator












Keith
 

Hi Eric,

Just a thought here - you said:

“I am having issues with 60, 20 and 6. With them also causing some havoc on auto range as well. When I have a situation where they are working the unit locks in and works as expected. These are supposed to have a 5Vdc coil but when I was testing one with a square wave it would not trip till about 8Vdc.”

So from your description, it sounds from this like they are working but perhaps mysteriously intermittent?

If so, one thing I’ve seen on DC powered reed switches that are “vintage” (i.e. old far beyond their rated service life) is that sometimes the application of a DC voltage to a coil over a very long period of time (i.e. years) can induce residual magnetism somewhere in the switch assembly. This residual magnetism can make them act “sticky”. They stay on when they are off, or they are hard to energize at the rated voltage.

I admit I have not seen this on Tek scopes - no experience there - but I’ve definitely seen this on vintage analog recording consoles and vintage analog tape machines, which use a lot of Reed relays. My solution was to use a spot tape demagnetizer tool to demagnetize the switch assembly. It seemed to work for me, assuming the relay wasn’t actually bad.

Maybe not useful info in your case, but I thought I would throw it in.


Jean-Paul
 

Bonjour, sealed reed relays are VERY reliable and the telephone system had lifetimes for 40 years in constant use on 24.48V.

But reeds can develop film on the contact surfaces, especially if unused for a long time.

We have sometimes rejuvenated a reed relay wiht this procedure:

1/ Check coil V and I
2/ Apply a line freq low voltage with a variac and transformer (or curve tracer!) that is about that voltage. (have used diode for 1/2 wave rectified)
3/ Allow the relay to buzz for a few minutes.
4/ Test relay and repeat or perhaps raise the applied V if needed.

NOTE: Polar relays with magnets or latching relays should NOT be treated this way!

Be fine if this can succeed!

Kind Regards,

Jon


Eric
 

I can now confirm that my solution with the coto 2332 relays worked and brought the unit back to life. I was waiting on and interface board that I doodled up to arrive for testing. Everything worked perfectly except some silk screen was missing but that is due to me using the nightly builds of kicad and nothing the board house did. I have uploaded photos in to the photo section if anyone is curious. For those that make their own boards I would strongly recommend getting these boards made as the plated through hole is a nice to have and there are some very small features. I have 2 more sets of boards if any one else would like a set. And needs some options for a similar unit. The 501A is back up and running now all it needs is a CAL.

The main symptom you need this fix is a galloping auto range that wont settle. In my unit this was caused by multiple dead relays and a bad IC that was sending out funny (incorrect) data.

Thanks for the help on this one.

Eric

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Jean-Paul
Sent: Saturday, April 10, 2021 12:23 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Reed relays for a sick AA501A

Bonjour, sealed reed relays are VERY reliable and the telephone system had lifetimes for 40 years in constant use on 24.48V.

But reeds can develop film on the contact surfaces, especially if unused for a long time.

We have sometimes rejuvenated a reed relay wiht this procedure:

1/ Check coil V and I
2/ Apply a line freq low voltage with a variac and transformer (or curve tracer!) that is about that voltage. (have used diode for 1/2 wave rectified) 3/ Allow the relay to buzz for a few minutes.
4/ Test relay and repeat or perhaps raise the applied V if needed.

NOTE: Polar relays with magnets or latching relays should NOT be treated this way!

Be fine if this can succeed!

Kind Regards,

Jon


Stephen
 

Congratulations!!