开云体育

U8 test

jerry-KF6VB All Messages By This Member #6387 Hello all, My T41 has been oscillating on bands higher than 20M. I think others have traced a similar problem to U8, the first analog switch in the receive path on the K9HZ LPF control card. I just looked at the card - U8 is going to be a challenging chip to replace, and it would be nice to test things first, and not replace it if it doesn't need it. Can anybody supply details of such a test? I have a decent SA with tracking generator. - Jerry, KF6VB
Rick Price All Messages By This Member #6391 开云体育 Hi Jerry, I was also having oscillations on high bands, traced mine back to the T/R switch plug in.? 20 pins in total but only one of them was a ground, pin 2 of the TR CTL. ?I had a loose fitting ground pin.? Replaced the socket, actually replaced two sockets after checking the tightness of a single pin in each hole.? I also added a ground wire from the top of the T/R board, scrapped away a little solder resist and soldered directly to the top of the board, to one of the ground holes above it on an unused INVTR jumper jack ground.? That alone solved my oscillation issue. Later found U6, inverter, was not changing state from R to T which could have added to the problem.? Even though I used Kapton tape for temp isolation, hot air still melted, distorted, the case end on two antenna relays, very small area to work in with hot air. ?Ended up removing all ANT relays and when I was finished only put one back for the time being. Rick, kN4AIE ? toggle quoted message Show quoted text From: [email protected] <[email protected]> On Behalf Of jerry-KF6VB via groups.io Sent: Sunday, April 13, 2025 2:29 PM To: [email protected] Subject: [AmateurRadioBuilders] U8 test ? Hello all, My T41 has been oscillating on bands higher than 20M. I think others have traced a similar problem to U8, the first analog switch in the receive path on the K9HZ LPF control card. I just looked at the card - U8 is going to be a challenging chip to replace, and it would be nice to test things first, and not replace it if it doesn't need it. Can anybody supply details of such a test? I have a decent SA with tracking generator. - Jerry, KF6VB
K9HZ All Messages By This Member #6392 开云体育 Jerry… on the 1.8 MHZ filter… did you build it on the LPF or did you just short across it? ? ? Dr. William J. Schmidt - K9HZ 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@... ? ? toggle quoted message Show quoted text From: [email protected] <[email protected]> On Behalf Of jerry-KF6VB Sent: Sunday, April 13, 2025 1:29 PM To: [email protected] Subject: [AmateurRadioBuilders] U8 test ? Hello all, My T41 has been oscillating on bands higher than 20M. I think others have traced a similar problem to U8, the first analog switch in the receive path on the K9HZ LPF control card. I just looked at the card - U8 is going to be a challenging chip to replace, and it would be nice to test things first, and not replace it if it doesn't need it. Can anybody supply details of such a test? I have a decent SA with tracking generator. - Jerry, KF6VB
jerry-KF6VB All Messages By This Member #6393 On 2025-04-13 13:00, K9HZ wrote: Jerry… on the 1.8 MHZ filter… did you build it on the LPF or did you just short across it? *** I built it. - Jerry, KF6VB DR. WILLIAM J. SCHMIDT - K9HZ 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: Sunday, April 13, 2025 1:29 PM TO: [email protected] SUBJECT: [AmateurRadioBuilders] U8 test Hello all, My T41 has been oscillating on bands higher than 20M. I think others have traced a similar problem to U8, the first analog switch in the receive path on the K9HZ LPF control card. I just looked at the card - U8 is going to be a challenging chip to replace, and it would be nice to test things first, and not replace it if it doesn't need it. Can anybody supply details of such a test? I have a decent SA with tracking generator. - Jerry, KF6VB Links: ------ [1] [2] /g/AmateurRadioBuilders/message/6392 [3] /mt/112245177/243852 [4] /g/AmateurRadioBuilders/post [5] /g/AmateurRadioBuilders/editsub/243852 [6] /g/AmateurRadioBuilders/leave/11522011/243852/920863695/xyzzy
D Solt All Messages By This Member #6394 开云体育 Jerry,? Version 66.4 had a bug that caused my T41 to oscillate above 20m. 66.9 solved that. If you take out the MW high pass you need to make sure you have a dc blocking cap in its place. Oliver posted a lot on checking feedback from PA out to input.? dave, n3ds toggle quoted message Show quoted text On Apr 13, 2025, at 3:47?PM, Rick Price via groups.io <rickprice48@...> wrote: ? Hi Jerry, I was also having oscillations on high bands, traced mine back to the T/R switch plug in.? 20 pins in total but only one of them was a ground, pin 2 of the TR CTL. ?I had a loose fitting ground pin.? Replaced the socket, actually replaced two sockets after checking the tightness of a single pin in each hole.? I also added a ground wire from the top of the T/R board, scrapped away a little solder resist and soldered directly to the top of the board, to one of the ground holes above it on an unused INVTR jumper jack ground.? That alone solved my oscillation issue. Later found U6, inverter, was not changing state from R to T which could have added to the problem.? Even though I used Kapton tape for temp isolation, hot air still melted, distorted, the case end on two antenna relays, very small area to work in with hot air. ?Ended up removing all ANT relays and when I was finished only put one back for the time being. Rick, kN4AIE ? From: [email protected] <[email protected]> On Behalf Of jerry-KF6VB via groups.io Sent: Sunday, April 13, 2025 2:29 PM To: [email protected] Subject: [AmateurRadioBuilders] U8 test ? Hello all, My T41 has been oscillating on bands higher than 20M. I think others have traced a similar problem to U8, the first analog switch in the receive path on the K9HZ LPF control card. I just looked at the card - U8 is going to be a challenging chip to replace, and it would be nice to test things first, and not replace it if it doesn't need it. Can anybody supply details of such a test? I have a decent SA with tracking generator. - Jerry, KF6VB
Oliver KI3P All Messages By This Member #6397 Hi Jerry, ? I posted the measurement I used to prove that U8 was bad here: /g/SoftwareControlledHamRadio/message/33289 ? Cheers, Oliver KI3P
jerry-KF6VB All Messages By This Member #6408 On 2025-04-13 14:45, Oliver KI3P via groups.io wrote: Hi Jerry, I posted the measurement I used to prove that U8 was bad here: /g/SoftwareControlledHamRadio/message/33289 *** So - you did this measurement with RX_BPF_SEL = False, right? -Jerry, KF6VB
Oliver KI3P All Messages By This Member #6410 When RX_BPF is LOW/FALSE/0, S21 between J23 and J18 (assuming receive is bridged to transmit in the TR switch) should be low, meaning less than -45 dB. That's what is shown in the plot on the right. When U8 was blown S21 was actually between -3 and -8 dB. On Monday, April 14th, 2025 at 3:28 PM, jerry-KF6VB <jerry@...> wrote: toggle quoted message Show quoted text On 2025-04-13 14:45, Oliver KI3P via groups.io wrote: Hi Jerry, I posted the measurement I used to prove that U8 was bad here: /g/SoftwareControlledHamRadio/message/33289 *** So - you did this measurement with RX_BPF_SEL = False, right? -Jerry, KF6VB

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