Hello all,
We either had two bad preamps to begin with, or they became casualties during transport to K4T, but regardless--the Icom preamps we took appear to have bad GAsFET devices in them.
Can anybody tell me what is the device in each unit (AG-25 and AG-35)? And are they something a skilled ham can reasonably replace?
Specific suggestions for a parts source will be appreciated, too.
73,
Mark L. Hammond [N8MH]
For the AG-35, it's a 2SK121Y. Not sure about the AG-25.
As others have mentioned, because of the proximity of the relay, one of the easiest ways to replace it is to cut the leads on the old device, then bend & trim the leads on the new device to "straddle" the old leads & solder away. Way easier than removing the relay...
George, KA3HSW
----- Original Message ----- From: "Mark L. Hammond" marklhammond@gmail.com To: amsat-bb@amsat.org Sent: Wednesday, March 17, 2010 5:29 PM Subject: [amsat-bb] Devices in Icom preamps AG-25 AG-35
Hello all,
We either had two bad preamps to begin with, or they became casualties during transport to K4T, but regardless--the Icom preamps we took appear to have bad GAsFET devices in them.
Can anybody tell me what is the device in each unit (AG-25 and AG-35)? And are they something a skilled ham can reasonably replace?
Specific suggestions for a parts source will be appreciated, too.
73,
Mark L. Hammond [N8MH]
Hi George, KA3HSW
The 3SK121Y is a Dual Gate MOS-FET in package SOT 143R and it can be directly replaced by the very inexpencive BF998R with same package
See the cross reference here:
http://www.go-ic.cn/admin/newspic/20061127185602infineon.pdf
The Noise Figure of the BF998R is 1 dB at 800 MHz
See the data sheet here:
http://www.nxp.com/documents/data_sheet/BF998.pdf
I hope this helps.
73" de
i8CVS Domenico
----- Original Message ----- From: "George Henry" ka3hsw@att.net To: amsat-bb@amsat.org; "Mark L. Hammond" marklhammond@gmail.com Sent: Thursday, March 18, 2010 4:54 AM Subject: [amsat-bb] Re: Devices in Icom preamps AG-25 AG-35
For the AG-35, it's a 2SK121Y. Not sure about the AG-25.
As others have mentioned, because of the proximity of the relay, one of
the
easiest ways to replace it is to cut the leads on the old device, then
bend
& trim the leads on the new device to "straddle" the old leads & solder away. Way easier than removing the relay...
George, KA3HSW
----- Original Message ----- From: "Mark L. Hammond" marklhammond@gmail.com To: amsat-bb@amsat.org Sent: Wednesday, March 17, 2010 5:29 PM Subject: [amsat-bb] Devices in Icom preamps AG-25 AG-35
Hello all,
We either had two bad preamps to begin with, or they became casualties during transport to K4T, but regardless--the Icom preamps we took appear to have bad GAsFET devices in them.
Can anybody tell me what is the device in each unit (AG-25 and AG-35)? And are they something a skilled ham can reasonably replace?
Specific suggestions for a parts source will be appreciated, too.
73,
Mark L. Hammond [N8MH]
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Correction: 3SK121Y, not 2SK...
Sorry....
George,KA3HSW
----- Original Message ----- From: "Mark L. Hammond" marklhammond@gmail.com To: amsat-bb@amsat.org Sent: Wednesday, March 17, 2010 5:29 PM Subject: [amsat-bb] Devices in Icom preamps AG-25 AG-35
Hello all,
We either had two bad preamps to begin with, or they became casualties during transport to K4T, but regardless--the Icom preamps we took appear to have bad GAsFET devices in them.
Can anybody tell me what is the device in each unit (AG-25 and AG-35)? And are they something a skilled ham can reasonably replace?
Specific suggestions for a parts source will be appreciated, too.
73,
Mark L. Hammond [N8MH]
I should have offered this first: before suspecting the preamps, did you enable preamp control for each band in the 910's "SET" menu? Preamp control must be enabled before the front panel P.AMP button will switch power to the preamp. Also, there must not be anything inline such as an SWR meter, filter, or anything else that might block DC on the coax.
If you hook the preamp up to the rig with a short jumper cable, you should head a noticeable relay click from the preamp when you press & hold the P.AMP button.
George, KA3HSW
----- Original Message ----- From: "Mark L. Hammond" marklhammond@gmail.com To: amsat-bb@amsat.org Sent: Wednesday, March 17, 2010 5:29 PM Subject: [amsat-bb] Devices in Icom preamps AG-25 AG-35
Hello all,
We either had two bad preamps to begin with, or they became casualties during transport to K4T, but regardless--the Icom preamps we took appear to have bad GAsFET devices in them.
[snip]
Hi George,
Thanks for the tips. We had a measured 12V at the connector attaching to the preamps and the menus were correct, so every thing indicates something was amiss on the preamp-hardware side.
I hope my colleague can get his preamps in working order.
Does anybody have the device information for the AG-25 units?
Thanks!
Mark N8MH
On Thu, Mar 18, 2010 at 12:20 AM, George Henry ka3hsw@att.net wrote:
I should have offered this first: before suspecting the preamps, did you enable preamp control for each band in the 910's "SET" menu? Preamp control must be enabled before the front panel P.AMP button will switch power to the preamp. Also, there must not be anything inline such as an SWR meter, filter, or anything else that might block DC on the coax.
If you hook the preamp up to the rig with a short jumper cable, you should head a noticeable relay click from the preamp when you press & hold the P.AMP button.
George, KA3HSW
----- Original Message ----- From: "Mark L. Hammond" marklhammond@gmail.com To: amsat-bb@amsat.org Sent: Wednesday, March 17, 2010 5:29 PM Subject: [amsat-bb] Devices in Icom preamps AG-25 AG-35
Hello all,
We either had two bad preamps to begin with, or they became casualties during transport to K4T, but regardless--the Icom preamps we took appear to have bad GAsFET devices in them.
[snip]
Going back in the archives, I found a message that said the AG-25 also uses the 3SK121Y. Thru Google, I also found a site which talked about replacing the device with a 3SK183 https://www.stu2.net/wiki/index.php?title=Satellites&printable=yes.
George, KA3HSW
----- Original Message ----
From: Mark L. Hammond marklhammond@gmail.com To: George Henry ka3hsw@att.net Cc: amsat-bb@amsat.org Sent: Thu, March 18, 2010 5:44:13 AM Subject: Re: [amsat-bb] Devices in Icom preamps AG-25 AG-35
Hi George,
Thanks for the tips. We had a measured 12V at the connector
attaching
to the preamps and the menus were correct, so every thing
indicates
something was amiss on the preamp-hardware side.
I hope my
colleague can get his preamps in working order.
Does anybody have the
device information for the AG-25 units?
Thanks!
Mark
N8MH
FYI my browser (Firefox) warned me that link was 'untrusted'. Simply by removing the 's' in https, fixed that issue.
I'm expecting an AG-25 tomorrow, so if anyone has a need, I'll open it up and take some hi-resolution pictures of it.
I'm still also looking for similar information for a Mirage KP-2 440 preamp.
73 de W4AS
On Mar 18, 2010, at 1:38 PM, George Henry wrote:
Going back in the archives, I found a message that said the AG-25 also uses the 3SK121Y. Thru Google, I also found a site which talked about replacing the device with a 3SK183 https://www.stu2.net/wiki/index.php?title=Satellites&printable=yes.
George, KA3HSW
----- Original Message ----
From: Mark L. Hammond marklhammond@gmail.com To: George Henry ka3hsw@att.net Cc: amsat-bb@amsat.org Sent: Thu, March 18, 2010 5:44:13 AM Subject: Re: [amsat-bb] Devices in Icom preamps AG-25 AG-35
Hi George,
Thanks for the tips. We had a measured 12V at the connector
attaching
to the preamps and the menus were correct, so every thing
indicates
something was amiss on the preamp-hardware side.
I hope my
colleague can get his preamps in working order.
Does anybody have the
device information for the AG-25 units?
Thanks!
Mark
N8MH
Sebastian wrote:
FYI my browser (Firefox) warned me that link was 'untrusted'. Simply by removing the 's' in https, fixed that issue.
Yes - the SSL cert is self-signed so the browsers throw an exception. ;) http works, now.
I found the replacement part number somewhere in the AMSAT archives after I blew up my preamp. ;) I bought the 3SK183 from http://www.xs4all.nl/~barendh/Indexeng.htm. (Look under FETs on the right hand frame of his web site. You have to scroll down.)
Stu2 W7IY
participants (5)
-
George Henry -
i8cvs -
Mark L. Hammond -
Sebastian -
Stu2