I have only just joined this group earlier today and am still trying
to work out how to navigate my way around

OK, thanks David

I assume I can email you back directly, is that correct ?

?

?

?

On Wed, Mar 1, 2023 at 04:42 PM, Craig Mayfield wrote:

?

I have only just joined this group earlier today and am still trying to work out how to navigate my way around

?

I have a HP 3457A and it keeps giving me an error 256. I have replaced the filter caps and followed the steps in as shown in a series of YouTube videos and I can get the diagnostic 8 to pass most of the time, however it then fails. On the YouTube series, the guy replaced 6 of the FETS as shown in the attached document. I am trying to find modern equivalents of these to order them. I have contacted Keysight and Element 14 to no avail. Can someone suggest a part number and or brand of FET I can use which should do the job as per the manufacturers original specs ?

----
Hi Craig,
Service manual says

"8-49. Front end zero measurement errors (error code 16) and AC flatness test errors (error code 256) can often be remedied by calibration. Refer to Section V for the appropriate procedures."

Did you try doing an AC calibration first?

Ozan

?

On Wed, Mar 1, 2023 at 06:06 PM, Craig Mayfield wrote:

Hi Ozan

?

Yes, I did. If I don’t, it comes up with an error 264. By doing the calibration, I am only left with an error 256. I then adjust the flatness pot and can get it to “0” PASS maybe 9 seconds out of 10 and then it fails once and then passes again and again and occasionally fails again. When I do the self test, it FAILS every time with 256

?

This guy has 3 videos in a series which were helpful. He replaced the FETS and the problem was eliminated. He seems to be having the same issue as me. I just don’t know which FETS he used and Keysight can’t tell me

?

?

?

---
Hi Craig,
Debugging the actual issue is more fun and I am sure Dave would agree but the transistor can be found by searching Keysight:



Database says it is a J304. Mouser in US has them, I don't know about the distributors in Australia.

Ozan

?

On Wed, Mar 1, 2023 at 06:57 PM, Craig Mayfield wrote:

Hi Ozan

?

That’s excellent news if that’s the one and its directly compatible. I will get some on order asap if you are sure ?

?

---
Hi Craig,
I don't have this equipment and I didn't do any repairs on it so can't give you 100% assurance. However, I gave you the link to Keysight?(I am sure you know HP->Agilent->Keysight connection) part finder for the cross reference. It is as good as it gets for free advice :)

I usually don't recommend replacing parts without checking if they are faulty. However, everyone has a different debug approach.
Ozan

Dave - terrible!!! How did you cope with that at the time?.... :)
On Wed, Mar 1, 2023 at 4:55?PM Dave McGuire <mcguire@... <mailto:mcguire@...>> wrote:
On 3/1/23 19:52, Craig Mayfield wrote:
> OK, thanks David
>
> I assume I can email you back directly, is that correct ?
? ?Sure.? But while I own a 3457A, I've never had to repair it, so I
can't help you with your FET issue.
? ?It was frustrating, actually.? I bought it on eBay as "broken",
wouldn't power on, and got it very cheap. (like $75) The power switch
was mechanically jammed.? I was looking forward to a fun
troubleshooting
session!
? ? ? ? ? ? -Dave
--
Dave McGuire, AK4HZ
New Kensington, PA

Dave - terrible!!! How did you cope with that at the time?.... :)

On Wed, Mar 1, 2023 at 4:55?PM Dave McGuire <mcguire@...
<mailto:mcguire@...>> wrote:

On 3/1/23 19:52, Craig Mayfield wrote:
> OK, thanks David
>
> I assume I can email you back directly, is that correct ?

Sure. But while I own a 3457A, I've never had to repair it, so I
can't help you with your FET issue.

It was frustrating, actually. I bought it on eBay as "broken",
wouldn't power on, and got it very cheap. (like $75) The power switch
was mechanically jammed. I was looking forward to a fun
troubleshooting
session!

-Dave

--
Dave McGuire, AK4HZ
New Kensington, PA

I know!? I thought about asking a neighbor to come over and break it, and not tell me how.

That was a good price
Best Regards
CRAIG MAYFIELD | Director - Particle & Environmental Technologies
Alpha Scientific Pty Ltd
Melbourne Office
Phone: (03) 9893 3972
Mobile: 0413 124 589
Email: craig@...
Website: www.alphascientific.com.au
This e-mail message and any attachments are subject to copyright and they are intended only for the addressee and may contain confidential or privileged information. Confidentiality and privilege are not waived if you are not the intended recipient of this e-mail, nor may you use or retain, or disclose, copy or forward to any third party this e-mail, or any information contained in or attached to it. If you received this e-mail in error please delete it (and any copy of it from your computer system) and kindly notify the sender by reply e-mail. Alpha Scientific Pty Ltd does not warrant that this e-mail and / or any attachments are error or virus free and recommends that all attachments be scanned / checked for computer viruses.
-----Original Message-----
From: [email protected] <[email protected]> On Behalf Of Dave McGuire
Sent: Thursday, 2 March 2023 3:17 PM
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] HP 3457A FET Transistors
I know! I thought about asking a neighbor to come over and break it, and not tell me how. But then I just decided to be happy about getting a 3457A for $75. B-)
-Dave
On 3/1/23 19:59, Radu Bogdan Dicher wrote:

Dave - terrible!!! How did you cope with that at the time?.... :)

On Wed, Mar 1, 2023 at 4:55?PM Dave McGuire <mcguire@...
<mailto:mcguire@...>> wrote:

On 3/1/23 19:52, Craig Mayfield wrote:
> OK, thanks David
>
> I assume I can email you back directly, is that correct ?

Sure. But while I own a 3457A, I've never had to repair it, so I
can't help you with your FET issue.

It was frustrating, actually. I bought it on eBay as "broken",
wouldn't power on, and got it very cheap. (like $75) The power switch
was mechanically jammed. I was looking forward to a fun
troubleshooting
session!

-Dave

--
Dave McGuire, AK4HZ
New Kensington, PA

--
Dave McGuire, AK4HZ
New Kensington, PA

Dear Sir / Madam

I have only just joined this group earlier today and am still trying to work
out how to navigate my way around

I have a HP 3457A and it keeps giving me an error 256. I have replaced the
filter caps and followed the steps in as shown in a series of YouTube videos
and I can get the diagnostic 8 to pass most of the time, however it then
fails. On the YouTube series, the guy replaced 6 of the FETS as shown in the
attached document. I am trying to find modern equivalents of these to order
them. I have contacted Keysight and Element 14 to no avail. Can someone
suggest a part number and or brand of FET I can use which should do the job as
per the manufacturers original specs ?