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Re: Oscillation Fixed

 

On 2025-05-01 13:50, K9HZ wrote:
“So the next time it pops, I should be able to replace it without
removing any relay”

Not sure what is going on… maybe a static issue? If you are not
using the HPF you can put some limiting circuitry there.
*** I am using the HPF. Way too much broadcast here to do without it.

How about a pair of Schottkys? One from the signal to ground - won't
let it go below -0.5V or so and another one from signal to +5.

- Jerry




The 0179
will take up to 33 db or 2W… and at 50 ohms (which is the design) is
about 10V. You will never have an RF signal even half that strong
come in the RX so even a string of a couple diodes back to back would
be more than sufficient.

DR. WILLIAM J. SCHMIDT - K9HZ J62K(J68HZ) 8P6HK ZF2HZ PJ4/K9HZ
VP5/K9HZ PJ2/K9HZ VP2EHZ

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com [1]

Moderator: North American QRO Group at Groups.IO.

Moderator: Amateur Radio Builders Group at Groups.IO.

email: bill@...

FROM: [email protected] <[email protected]>
ON BEHALF OF jerry-KF6VB
SENT: Thursday, May 1, 2025 3:09 PM
TO: [email protected]
SUBJECT: [AmateurRadioBuilders] Oscillation Fixed

All,

As you may remember, my T41 has been oscillating on all frequencies
above 20M. Today, I replaced
U8, the first analog switch in the receive path on the K9HZ LPF card.
Problem solved, no more oscillation.

To get access to U8, I removed all four antenna relays. When I put it
back together, I installed
only one of them - because I only use it with one antenna. Luckily,
the
needed antenna relay is
the farthest one from U8. So the next time it pops, I should be able
to
replace it without removing
any relay.

I'm not the only person who has fried U8. Why does it break? I can
only guess that somehow,
Big RF got into the receive input.

Sure would be nice if I could protect it somehow....

- Jerry, KF6VB



Links:
------
[1]
[2] /g/AmateurRadioBuilders/message/6484
[3] /mt/112568743/243852
[4] /g/AmateurRadioBuilders/post
[5] /g/AmateurRadioBuilders/editsub/243852
[6]
/g/AmateurRadioBuilders/leave/11522011/243852/920863695/xyzzy


Re: Oscillation Fixed

 

开云体育

“So the next time it pops, I should be able to replace it without removing any relay”

?

Not sure what is going on… maybe a static issue? If you are not using the HPF you can put some limiting circuitry there.? The 0179 will take up to 33 db or 2W… and at 50 ohms (which is the design) is about 10V.? You will never have an RF signal even half that strong come in the RX so even a string of a couple diodes back to back would be more than sufficient. ??

?

Dr. William J. Schmidt - K9HZ J62K(J68HZ) 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ

?

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

?

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it:

?

Moderator: North American QRO Group at Groups.IO.

Moderator: Amateur Radio Builders Group at Groups.IO.

?

email:? bill@...

?

?

From: [email protected] <[email protected]> On Behalf Of jerry-KF6VB
Sent: Thursday, May 1, 2025 3:09 PM
To: [email protected]
Subject: [AmateurRadioBuilders] Oscillation Fixed

?

All,

As you may remember, my T41 has been oscillating on all frequencies
above 20M. Today, I replaced
U8, the first analog switch in the receive path on the K9HZ LPF card.
Problem solved, no more oscillation.

To get access to U8, I removed all four antenna relays. When I put it
back together, I installed
only one of them - because I only use it with one antenna. Luckily, the
needed antenna relay is
the farthest one from U8. So the next time it pops, I should be able to
replace it without removing
any relay.

I'm not the only person who has fried U8. Why does it break? I can
only guess that somehow,
Big RF got into the receive input.

Sure would be nice if I could protect it somehow....

- Jerry, KF6VB


Oscillation Fixed

 

All,

As you may remember, my T41 has been oscillating on all frequencies
above 20M. Today, I replaced
U8, the first analog switch in the receive path on the K9HZ LPF card.
Problem solved, no more oscillation.

To get access to U8, I removed all four antenna relays. When I put it
back together, I installed
only one of them - because I only use it with one antenna. Luckily, the
needed antenna relay is
the farthest one from U8. So the next time it pops, I should be able to
replace it without removing
any relay.

I'm not the only person who has fried U8. Why does it break? I can
only guess that somehow,
Big RF got into the receive input.

Sure would be nice if I could protect it somehow....

- Jerry, KF6VB


Re: Display Advice

 

Thanks Phil,
I do have the proper 5" display, so after building the main board and testing it with the 5" display, then I'll try it with the 7"
Thanks for your detailed advice.
Best regards,
John K1JO


Re: Display Advice

 

John
?
First point - The display Normally used for T41 have the RA8875 controller, not RA8876.
?
Second point - As mentioned by Terrance the post on PJRC forum speculates RA8876 and LT7683 controllers are compatible. (This point is probably superfluous)?
?
Third Point - Larry says the LT7683 type displays work with the T41.
?
Fourth Point - The display you have, (type 7, i.e. ER-TFTM070-7), the wiring on Pins 1 to 8 of the 40 pin IDC (including power and SPI) is identical to the RA8875 type displays like ER-TFTM070-5V4 7" display.
?
I would give your LT7683 display a try, wire it the same as the Schematics say and see what happens. Remember, you can test the display with just the main board working.
?
Keep in mind two things:
1.? Your display is 5 V, remember to configure your main board J8 for 5V display.
2. Use a very short ribbon cable (>3" long) if you omit using DR. Bills display driver board at first.
?
This is what the first test cable I used to test the display looks like.
?
?
Regards?
Phil
VK2KKZ
?
On Tue, Apr 29, 2025 at 11:48 AM, John Owens K1JO wrote:

My fat fingers...I missed the last "6". When I said RA887 I meant RA8876.
According to the website, it said the ones I ordered today are the RA8876. Well see, however, I am interested to see if we can get the Lt7683 displays to work.
Best regards,
John K1JO


Re: Display Advice

 

My fat fingers...I missed the last "6". When I said RA887 I meant RA8876.
According to the website, it said the ones I ordered today are the RA8876. Well see, however, I am interested to see if we can get the Lt7683 displays to work.
Best regards,
John K1JO


Re: Display Advice

 

That post is actually referring to the RA8876 *not* the RA8875.
?
From on the BuyDisplay? website they say:
?
Controller IC Replacement Notice
Due to the global shortage of IC, the controller RA8876 used in this module has been difficult to purchase. In order not to affect the delivery, we will use the controller LT7683 as replacement which is fully compatible with the same stable performance when the RA8876 is out of stock. (Oct-28-2021)
?
The LT768x datasheet is found on the BuyDisplay site here
?
BuyDisplay are very good at making the datasheets for all their displays as well as the LCD and touch controllers they use in them available on their website. Just scroll down on the page where you can buy the display in question. They also provide sample code and sometimes libraries/drivers. Would that all vendors did the same.
?
On Mon, Apr 28, 2025 at 10:31 AM, Terrance Robertson, KN6ZDE wrote:

This over on the PJRC forum speculates the two controllers are compatible.


Re: Display Advice

 

I went ahead today and ordered two 7" RA887, 4-wire SPI, with Capacitive touch. Hopefully, the tariff won't kill me.
Larry, you said that you use the LS7683 controller display on your T-41 radio. How did you connect the SPI? My connectors are shown on the ER-TFTM070-7_Datasheet.pdf page 11-2, that I uploaded here at Files > BuyDisplays DataSheets. Are yours the same?
Best regards,
John K1JO


Re: Display Advice

 

Jack-
?
No, because Buy Display said it was compatible with the RA8875 and I didn't want to deviate from the T41 software.? I also have had it running the K7MDL software which is also written for the RA8875.?? If it is compatible, it is compatible.?? I think those that have been buying the Buy Display product for the last year or two have been getting the LT7683 without realizing it.?? It works!
?
-Larry
W1SIM
?


Re: Display Advice

 

Did you check for an LT7683 library?

Jack, W8TEE

On Monday, April 28, 2025 at 12:17:57 PM EDT, W1SIM via groups.io <w1sim@...> wrote:


I have an LT7683 chip on the Buy Display board that I bought 1 or 2 years ago.?? If I recall correctly, Buy Display said it was compatible with the RA8875.? The board does run the T41 software and other software that uses the RA8875 driver.
?
-Larry
W1SIM

--
Jack, W8TEE


Re: Display Advice

 

开云体育

Ok… I just don’t have any experience with the LT part.? It may, in fact, work…

?

Has anyone tried it that can report?

?

?

Dr. William J. Schmidt - K9HZ J62K(J68HZ) 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ

?

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

?

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it:

?

Moderator: North American QRO Group at Groups.IO.

Moderator: Amateur Radio Builders Group at Groups.IO.

?

email:? bill@...

?

?

From: [email protected] <[email protected]> On Behalf Of W1SIM via groups.io
Sent: Monday, April 28, 2025 11:18 AM
To: [email protected]
Subject: Re: [AmateurRadioBuilders] Display Advice

?

I have an LT7683 chip on the Buy Display board that I bought 1 or 2 years ago.?? If I recall correctly, Buy Display said it was compatible with the RA8875.? The board does run the T41 software and other software that uses the RA8875 driver.

?

-Larry

W1SIM


Re: Display Advice

 

I have an LT7683 chip on the Buy Display board that I bought 1 or 2 years ago.?? If I recall correctly, Buy Display said it was compatible with the RA8875.? The board does run the T41 software and other software that uses the RA8875 driver.
?
-Larry
W1SIM


Re: Display Advice

 

开云体育

I doubt it… no telling how different the RA8875 and LT7683 chips/ libraries are.? You should use a display that has an RA8875 controller chip and SPI connections.

?

?

Dr. William J. Schmidt - K9HZ J62K(J68HZ) 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ

?

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

?

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it:

?

Moderator: North American QRO Group at Groups.IO.

Moderator: Amateur Radio Builders Group at Groups.IO.

?

email:? bill@...

?

?

From: [email protected] <[email protected]> On Behalf Of John Owens K1JO via groups.io
Sent: Monday, April 28, 2025 7:45 AM
To: [email protected]
Subject: Re: [AmateurRadioBuilders] Display Advice

?

Looks like it will be a lot of work, even if I can find a LT7683 library for the Teensy4.1???


Re: Display Advice

 

开云体育

As long as the board uses a RA8875 controller chip… it will work no matter what it is..

?

?

Dr. William J. Schmidt - K9HZ J62K(J68HZ) 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ

?

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

?

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it:

?

Moderator: North American QRO Group at Groups.IO.

Moderator: Amateur Radio Builders Group at Groups.IO.

?

email:? bill@...

?

?

From: [email protected] <[email protected]> On Behalf Of John Owens K1JO via groups.io
Sent: Monday, April 28, 2025 6:04 AM
To: [email protected]
Subject: Re: [AmateurRadioBuilders] Display Advice

?

Thanks Bill and Phil,

The BuyDisplay China office was quick to send me the datasheet for the three displays that I purchased. I have uploaded them here at Files>BuyDisplays DataSheets. I am trying to use the 7" version which is ER-TFTM070-7. The board is not like the one you attached above. Here is the one I have:

It says the controller is the LT7683, see below. Hopefully, I can connect it up, as the site is reporting that the new tariff are in our court :(


Re: Display Advice

 

Has anyone bought one and tried it?

Jack, W8TEE

On Monday, April 28, 2025 at 10:31:37 AM EDT, Terrance Robertson, KN6ZDE via groups.io <tmrob4@...> wrote:


This over on the PJRC forum speculates the two controllers are compatible.

--
Jack, W8TEE


Re: Display Advice

 

This over on the PJRC forum speculates the two controllers are compatible.


Re: Display Advice

 

Looks like it will be a lot of work, even if I can find a LT7683 library for the Teensy4.1???


Re: Display Advice

 

Thanks Bill and Phil,
The BuyDisplay China office was quick to send me the datasheet for the three displays that I purchased. I have uploaded them here at Files>BuyDisplays DataSheets. I am trying to use the 7" version which is ER-TFTM070-7. The board is not like the one you attached above. Here is the one I have:
It says the controller is the LT7683, see below. Hopefully, I can connect it up, as the site is reporting that the new tariff are in our court :(


Added Folder /BuyDisplays DataSheets #file-notice

Group Notification
 

John Owens K1JO <johnowenschina@...> added folder /BuyDisplays DataSheets


Re: Display Advice

 

开云体育

“but it the layout of the board is different than the one they sent me” ???

?

Then its probably a different REV than whats on the sheet.? I’m not sure that matters.? I have multiple 5” and 7” displays from BuyDisplay that are different REVs.? Some look different and have different connection arrangements, BUT… they all work the same way.

?

?

Dr. William J. Schmidt - K9HZ J62K(J68HZ) 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ

?

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

?

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it:

?

Moderator: North American QRO Group at Groups.IO.

Moderator: Amateur Radio Builders Group at Groups.IO.

?

email:? bill@...

?

?

From: [email protected] <[email protected]> On Behalf Of John Owens K1JO via groups.io
Sent: Sunday, April 27, 2025 2:52 PM
To: [email protected]
Subject: Re: [AmateurRadioBuilders] Display Advice

?

Hi Bill,

Hope you have a nice trip.
Yeah, one of those PDFs is the one I downloaded from the BuyDisplays site but it the layout of the board is different than the one they sent me.
Best regards,

John K1JO