Re: So Why Do Those TR-4C Can Caps Fail?
Electrolytics have a small amount of leakage. They generate internal heat. The harder they work, the more heat. Over time this will degrade the cap. Hence the move to 105C and higher rated capacitors in recent years. Look at the design of the PS7. What components are closest to the fan? That is not just a coincidence. 73 -Jim NU0C On Sat, 13 Apr 2024 06:42:54 -0700 "Jerry NY2KW" <josternmd@...> wrote: I am very new to Drake just got my 1st TR4C but I've been working on Collins radios for many years.? It's a chicken or egg question.? If the can is not near any significant heat source, the only reason it can get hotter than surroundings is because its leaking current and acting like a DC resistor.
73 Jerry NY2KW
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Re: So Why Do Those TR-4C Can Caps Fail?
I am very new to Drake just got my 1st TR4C but I've been working on Collins radios for many years.? It's a chicken or egg question.? If the can is not near any significant heat source, the only reason it can get hotter than surroundings is because its leaking current and acting like a DC resistor.
73 Jerry NY2KW
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Re: So Why Do Those TR-4C Can Caps Fail?
I suspect that heat is the real enemy here. You mentioned that the can was hot. That's the end stage of a progressive process. 260v isn't a huge overvoltage but there is a lot going on inside those cans. Once the thermal degradation starts it only accelerates. 73 -Jim NU0C On Fri, 12 Apr 2024 23:23:26 +0000 "Steve Wedge, W1ES/4 via groups.io" <w1es@...> wrote: TNX for the info.
Steve Wedge, W1ES/4
-- 73 -Jim NU0C
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Re: So Why Do Those TR-4C Can Caps Fail?
My SN 27844 has a 250VDC can cap, too. Guess that was OEM off the assembly line for TR-4¡¯s.
Never noticed the modest 250 VDC rating on the cap nor pondered its significance. My purchased new in mid-1968 TR-4 has been carefully stored for years as I¡¯ve played with C-Lines and many other BA¡¯s.?
I¡¯ll sure replace the original cap before I fire it up again.
Dan WB4GRA
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Show quoted text
On Apr 12, 2024, at 7:23?PM, Steve Wedge, W1ES/4 via groups.io <w1es@...> wrote:
? TNX for the info.
Steve Wedge, W1ES/4
Time flies like an arrow.? Fruit flies like a banana.
Sent with secure email.
On Friday, April 12th, 2024 at 7:02 PM, n7qmm25 <n7qmm25@...> wrote:
The TR4 in my possession, sn 27xxx, has a Mallory can and it says
250 volts.
On 4/12/2024 1:57 PM, Steve Wedge,
W1ES/4 via groups.io wrote:
For
some reason, I was noticing that I have either replaced bad can
caps in all versions of the TR-4C (including Cw, with and
without RIT). I have a pretty good idea now why this has been
happening but I need for those of you who have older TR-3's and
TR-4's to take a quick look at your can cap.
I
can confirm that the can cap in the C version is somewhat
shorter than the cap used on the earlier sets, so it's
definitely a different part.
My
line voltage at my shack, and at my AC-4 that feeds my test
bench, is typically always over 120VAC, sometimes as high as
126VAC. This is still within the 10% margin for supplying all 4
Line gear and later. The USA has been on the 120V standard
since the early 60's,
The
AC4 - has a nominal +250V DC output, as well as the +650V and
-50 to -100 bias supply. On my bench, I can have voltages in
the TR-4 (any) that are as high as +260V. In fact, if you look
at the voltage chart for the TR-4Cm you can see that values of
up to 260V are expected.
THE
PROBLEM IS THAT THE CAN CAP (Twist-Lock) IS ONLY RATED FOR 250v!
This
is a bit of an unfortunate example of not allowing enough
headroom for the capacitors. It is my opinion that these
capacitors have been running at least at their maximum rating
with respect to C145A and C145D. The voltage chart expects
values over the rating of these two capacitor sections.
I
suspect that the older sets may have been rated at 300V or
more. I don't have a TR-4 that I can check.
There
aren't really many parts that I'd recommend that you change,
regardless of the set's condition but I will recommend this as
preventive maintenance for all TR-4C versions. The fact that
these capacitors have lasted 50+ years at overvoltage attests to
their initial quality but they're now at the point in time where
they've been beat up long enough.
The
Hayseed capacitor has ratings of 350V for 3 of the 4 sections
and 50V for the section that's used on the cathode of the VOX
amp. These ratings are what should have been designed in the
first place but that's all water under the bridge, obviously.
If you're still using the original can with your TR-4C, replace
it.
73,
Steve Wedge, W1ES/4
Time flies like an arrow. Fruit flies like a banana.
Sent with
secure email.
|
Re: So Why Do Those TR-4C Can Caps Fail?
TNX for the info.
Steve Wedge, W1ES/4
Time flies like an arrow.? Fruit flies like a banana.
Sent with secure email.
On Friday, April 12th, 2024 at 7:02 PM, n7qmm25 <n7qmm25@...> wrote:
The TR4 in my possession, sn 27xxx, has a Mallory can and it says
250 volts.
On 4/12/2024 1:57 PM, Steve Wedge,
W1ES/4 via groups.io wrote:
For
some reason, I was noticing that I have either replaced bad can
caps in all versions of the TR-4C (including Cw, with and
without RIT). I have a pretty good idea now why this has been
happening but I need for those of you who have older TR-3's and
TR-4's to take a quick look at your can cap.
I
can confirm that the can cap in the C version is somewhat
shorter than the cap used on the earlier sets, so it's
definitely a different part.
My
line voltage at my shack, and at my AC-4 that feeds my test
bench, is typically always over 120VAC, sometimes as high as
126VAC. This is still within the 10% margin for supplying all 4
Line gear and later. The USA has been on the 120V standard
since the early 60's,
The
AC4 - has a nominal +250V DC output, as well as the +650V and
-50 to -100 bias supply. On my bench, I can have voltages in
the TR-4 (any) that are as high as +260V. In fact, if you look
at the voltage chart for the TR-4Cm you can see that values of
up to 260V are expected.
THE
PROBLEM IS THAT THE CAN CAP (Twist-Lock) IS ONLY RATED FOR 250v!
This
is a bit of an unfortunate example of not allowing enough
headroom for the capacitors. It is my opinion that these
capacitors have been running at least at their maximum rating
with respect to C145A and C145D. The voltage chart expects
values over the rating of these two capacitor sections.
I
suspect that the older sets may have been rated at 300V or
more. I don't have a TR-4 that I can check.
There
aren't really many parts that I'd recommend that you change,
regardless of the set's condition but I will recommend this as
preventive maintenance for all TR-4C versions. The fact that
these capacitors have lasted 50+ years at overvoltage attests to
their initial quality but they're now at the point in time where
they've been beat up long enough.
The
Hayseed capacitor has ratings of 350V for 3 of the 4 sections
and 50V for the section that's used on the cathode of the VOX
amp. These ratings are what should have been designed in the
first place but that's all water under the bridge, obviously.
If you're still using the original can with your TR-4C, replace
it.
73,
Steve Wedge, W1ES/4
Time flies like an arrow. Fruit flies like a banana.
Sent with
secure email.
|
Re: 4 line filter impedance
Thanks Rob!
73
Stan
KM4HQE
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Show quoted text
On 4/11/24 21:17, Rob Sherwood wrote: I don¡¯t know about the balanced TR-3 filters, but the unbalanced TR-4 filters are 120 ohms.
R-4C plug-in filters are 50 ohms.
I believe T-4XC filters are 500 ohms.
Rob, NC0B
On Apr 11, 2024, at 7:51?PM, Stan Gammons via groups.io <buttercup11421@...> wrote:
?Hi All,
I was wondering if anyone knows the impedance of the IF filters used in
the 4 line transmitters and receivers? A search of this group seems to
indicate the TR-4 has 2,000 ohm impedance filters, TR-3 has 500 ohm
impedance filters. What about the receivers?
I emailed John Kriner to see if he knows, but he wasn't able to help.
John said he was sure he had a list of the impedances but he couldn't
find it. I asked Noble Radio to see if he knows, but haven't heard back
yet.
73
Stan
KM4HQE
|
Re: So Why Do Those TR-4C Can Caps Fail?
The TR4 in my possession, sn 27xxx, has a Mallory can and it says
250 volts.
On 4/12/2024 1:57 PM, Steve Wedge,
W1ES/4 via groups.io wrote:
toggle quoted message
Show quoted text
For
some reason, I was noticing that I have either replaced bad can
caps in all versions of the TR-4C (including Cw, with and
without RIT).? I have a pretty good idea now why this has been
happening but I need for those of you who have older TR-3's and
TR-4's to take a quick look at your can cap.
I
can confirm that the can cap in the C version is somewhat
shorter than the cap used on the earlier sets, so it's
definitely a different part.
My
line voltage at my shack, and at my AC-4 that feeds my test
bench, is typically always over 120VAC, sometimes as high as
126VAC.? This is still within the 10% margin for supplying all 4
Line gear and later.? The USA has been on the 120V standard
since the early 60's,
The
AC4 - has a nominal +250V DC output, as well as the +650V and
-50 to -100 bias supply.? On my bench, I can have voltages in
the TR-4 (any) that are as high as +260V.? In fact, if you look
at the voltage chart for the TR-4Cm you can see that values of
up to 260V are expected.
THE
PROBLEM IS THAT THE CAN CAP (Twist-Lock) IS ONLY RATED FOR 250v!
This
is a bit of an unfortunate example of not allowing enough
headroom for the capacitors.? It is my opinion that these
capacitors have been running at least at their maximum rating
with respect to C145A and C145D.? The voltage chart expects
values over the rating of these two capacitor sections.
I
suspect that the older sets may have been rated at 300V or
more.? I don't have a TR-4 that I can check.
There
aren't really many parts that I'd recommend that you change,
regardless of the set's condition but I will recommend this as
preventive maintenance for all TR-4C versions.? The fact that
these capacitors have lasted 50+ years at overvoltage attests to
their initial quality but they're now at the point in time where
they've been beat up long enough.
The
Hayseed capacitor has ratings of 350V for 3 of the 4 sections
and 50V for the section that's used on the cathode of the VOX
amp.? These ratings are what should have been designed in the
first place but that's all water under the bridge, obviously.?
If you're still using the original can with your TR-4C, replace
it.
73,
Steve Wedge, W1ES/4
Time flies like an arrow.? Fruit flies like a banana.
Sent with
secure email.
|
Re: So Why Do Those TR-4C Can Caps Fail?
Finding authoritative information on electrolytic caps is difficult. At least one respected handbook I have says that because the dielectric is formed by the voltage across the cap that electrolytics should be run at near their rated voltage or else the dielectric will not be formed correctly. Is this true? I have also seen discussion questioning this. If so how is the dielectric of a bi-polar electrolytic maintained? These are essentially back to back polarized caps. Essentially no DC passes through them. So, is the dielectric formed partly by AC?
The main reason for electrolytic caps is size. Because of the nature of the dielectric the effective dielectric constant is very high so a relatively small cap can have high capacitance value. In the past they were used mainly for power supply filtering where a fairly large amount of leakage, i.e. relatively small parallel resistance, was allowable but not for other purposes, such as audio coupling capacitors, where passage of DC is not desirable. However, other kinds of essentially electrolytic caps like tantalum caps, can be used in these applications.
I am far from an expert. I read what I can find and its left me puzzled.
BTW, I am another satisfied Hayseed Hamfest customer. Been doing business with Tom since he started.
toggle quoted message
Show quoted text
On 4/12/2024 2:20 PM, Steve Wedge, W1ES/4 via groups.io wrote: The first paragraph, I left off that the other sets I have purchased already had had their can caps replaced with Hayseed parts.
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
Re: So Why Do Those TR-4C Can Caps Fail?
The first paragraph, I left off that the other sets I have purchased already had had their can caps replaced with Hayseed parts.
This latest TR-4C didn't get to catastrophic failure but it was about a minute away from it.? I could not touch the cap with my finger.
Again, please, if you have an older TR-3/4, please reply to this email with the values of your capacitors -- even if you bypassed them with discrete parts underneath.
73,
Steve Wedge, W1ES/4
Time flies like an arrow.? Fruit flies like a banana.
Sent with secure email.
On Friday, April 12th, 2024 at 4:57 PM, Steve Wedge, W1ES/4 via groups.io <w1es@...> wrote:
For some reason, I was noticing that I have either replaced bad can caps in all versions of the TR-4C (including Cw, with and without RIT).? I have a pretty good idea now why this has been happening but I need for those of you who have older TR-3's and TR-4's to take a quick look at your can cap.
I can confirm that the can cap in the C version is somewhat shorter than the cap used on the earlier sets, so it's definitely a different part.
My line voltage at my shack, and at my AC-4 that feeds my test bench, is typically always over 120VAC, sometimes as high as 126VAC.? This is still within the 10% margin for supplying all 4 Line gear and later.? The USA has been on the 120V standard since the early 60's,
The AC4 - has a nominal +250V DC output, as well as the +650V and -50 to -100 bias supply.? On my bench, I can have voltages in the TR-4 (any) that are as high as +260V.? In fact, if you look at the voltage chart for the TR-4Cm you can see that values of up to 260V are expected.
THE PROBLEM IS THAT THE CAN CAP (Twist-Lock) IS ONLY RATED FOR 250v!
This is a bit of an unfortunate example of not allowing enough headroom for the capacitors.? It is my opinion that these capacitors have been running at least at their maximum rating with respect to C145A and C145D.? The voltage chart expects values over the rating of these two capacitor sections. I suspect that the older sets may have been rated at 300V or more.? I don't have a TR-4 that I can check.
There aren't really many parts that I'd recommend that you change, regardless of the set's condition but I will recommend this as preventive maintenance for all TR-4C versions.? The fact that these capacitors have lasted 50+ years at overvoltage attests to their initial quality but they're now at the point in time where they've been beat up long enough.
The Hayseed capacitor has ratings of 350V for 3 of the 4 sections and 50V for the section that's used on the cathode of the VOX amp.? These ratings are what should have been designed in the first place but that's all water under the bridge, obviously.? If you're still using the original can with your TR-4C, replace it.
73,
Steve Wedge, W1ES/4
Time flies like an arrow.? Fruit flies like a banana.
Sent with secure email.
|
So Why Do Those TR-4C Can Caps Fail?
For some reason, I was noticing that I have either replaced bad can caps in all versions of the TR-4C (including Cw, with and without RIT).? I have a pretty good idea now why this has been happening but I need for those of you who have older TR-3's and TR-4's to take a quick look at your can cap.
I can confirm that the can cap in the C version is somewhat shorter than the cap used on the earlier sets, so it's definitely a different part.
My line voltage at my shack, and at my AC-4 that feeds my test bench, is typically always over 120VAC, sometimes as high as 126VAC.? This is still within the 10% margin for supplying all 4 Line gear and later.? The USA has been on the 120V standard since the early 60's,
The AC4 - has a nominal +250V DC output, as well as the +650V and -50 to -100 bias supply.? On my bench, I can have voltages in the TR-4 (any) that are as high as +260V.? In fact, if you look at the voltage chart for the TR-4Cm you can see that values of up to 260V are expected.
THE PROBLEM IS THAT THE CAN CAP (Twist-Lock) IS ONLY RATED FOR 250v!
This is a bit of an unfortunate example of not allowing enough headroom for the capacitors.? It is my opinion that these capacitors have been running at least at their maximum rating with respect to C145A and C145D.? The voltage chart expects values over the rating of these two capacitor sections. I suspect that the older sets may have been rated at 300V or more.? I don't have a TR-4 that I can check.
There aren't really many parts that I'd recommend that you change, regardless of the set's condition but I will recommend this as preventive maintenance for all TR-4C versions.? The fact that these capacitors have lasted 50+ years at overvoltage attests to their initial quality but they're now at the point in time where they've been beat up long enough.
The Hayseed capacitor has ratings of 350V for 3 of the 4 sections and 50V for the section that's used on the cathode of the VOX amp.? These ratings are what should have been designed in the first place but that's all water under the bridge, obviously.? If you're still using the original can with your TR-4C, replace it.
73,
Steve Wedge, W1ES/4
Time flies like an arrow.? Fruit flies like a banana.
Sent with secure email.
|
Re: 4 line filter impedance
I don¡¯t know about the balanced TR-3 filters, but the unbalanced TR-4 filters are 120 ohms.
R-4C plug-in filters are 50 ohms.
I believe T-4XC filters are 500 ohms.
Rob, NC0B
toggle quoted message
Show quoted text
On Apr 11, 2024, at 7:51?PM, Stan Gammons via groups.io <buttercup11421@...> wrote:
?Hi All,
I was wondering if anyone knows the impedance of the IF filters used in
the 4 line transmitters and receivers? A search of this group seems to
indicate the TR-4 has 2,000 ohm impedance filters, TR-3 has 500 ohm
impedance filters. What about the receivers?
I emailed John Kriner to see if he knows, but he wasn't able to help.
John said he was sure he had a list of the impedances but he couldn't
find it. I asked Noble Radio to see if he knows, but haven't heard back
yet.
73
Stan
KM4HQE
|
Hi All,
I was wondering if anyone knows the impedance of the IF filters used in
the 4 line transmitters and receivers??? A search of this group seems to
indicate the TR-4 has 2,000 ohm impedance filters, TR-3 has 500 ohm
impedance filters. What about the receivers?
I emailed John Kriner to see if he knows, but he wasn't able to help.?
John said he was sure he had a list of the impedances but he couldn't
find it.? I asked Noble Radio to see if he knows, but haven't heard back
yet.
73
Stan
KM4HQE
|
On 2024-04-11 10:36, Don Humphrey wrote: OK Gang,
I think I got it I think it's the PBT switch. *** Spray it - sparingly - with DeOxit and exercise it. - Jerry, KF6VB when I operate the switch sometimes the controls will
start acting normal.
|
Re: Very Nice anp on QTH.com
A pair of 8122 should be easily capable of a kilowatt+ on VHF. Probably grid-driven which means low drive. 8122s are not hard to find. With careful shopping you can pick up good used tubes or NOS on eBay for one. I wold be seriously tempted if 73 -Jim NU0C On Thu, 11 Apr 2024 14:01:50 -0400 (EDT) "KL7AM" <w7apm@...> wrote: Beautiful looking homebrew amp on qth and made to match the 4-line.
ad# 1682503
He is changing the ad to show correct tube numbers to 8122's
KL7AM
|
Beautiful looking homebrew amp on qth and made to match the 4-line.
ad# 1682503
He is changing the ad to show correct tube numbers to 8122's
KL7AM
|
OK Gang,
I think I got it I think it's the PBT switch.
when I operate the switch sometimes the controls will
start acting normal.
I am going to work on the controls some more.
This TR-7 was a flea market find and I don't think
I have all the BUGS out.
Thanks to Gary and all for your help.
|
Gary, I think you have hit on it.?
Steve Wedge, W1ES/4
Time flies like an arrow. Fruit flies like a banana.
On Thu, Apr 11, 2024 at 11:34, Gary Follett < xntrick1948@...> wrote: OR try turning OFF PBT. If the radio PBT is on, the mode selector switch will have no impact on received signal.
Gary
W0DVN On Apr 11, 2024, at 10:31?AM, Tom Evans <Tom.AG9X@...> wrote:
Don,
On receive, turn on PBT and verify that the front panel PBT control is working.
Tom, AG9X
On Thu, Apr 11, 2024 at 10:01?AM Don Humphrey < dscc1947@...> wrote: I think so nobody has told me i am transmitting DSB
|
OR try turning OFF PBT. If the radio PBT is on, the mode selector switch will have no impact on received signal.
Gary
toggle quoted message
Show quoted text
On Apr 11, 2024, at 10:31?AM, Tom Evans <Tom.AG9X@...> wrote:
Don,
On receive, turn on PBT and verify that the front panel PBT control is working.
Tom, AG9X
On Thu, Apr 11, 2024 at 10:01?AM Don Humphrey < dscc1947@...> wrote: I think so nobody has told me i am transmitting DSB
|
Don,
On receive, turn on PBT and verify that the front panel PBT control is working.
Tom, AG9X
On Thu, Apr 11, 2024 at 10:01?AM Don Humphrey < dscc1947@...> wrote: I think so nobody has told me i am transmitting DSB
|
I think so nobody has told me i am transmitting DSB
|
Jim Shorney
Rob Sherwood