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Another 465B Back In Service

Don N3DEB
 

Had a backup 465B taken out of service sitting on my hobbyist repair bench for about a year - long journey (hopefully) ended.

Symptom was losing trace after warm up, power supply folded over. The folder over at first was after a few minutes, gradually occurring almost immediately. While that seems like an easy fix based on all the group discussion, it was not because of some cascading failures. I replaced the power supply caps while I was at it.

All told I replaced quite an assortment of failed parts to get the trace back that included voltage regulation components. I lost my patience searching for the intermittent tantalum and injected DC slowly until I got the expected but unnerving "Pop" and column of smoke. Replaced the roasted peanut and got my trace back.

Next replaced the rest of the tantalums and the trace sharpened and other performance issues corrected.

I often use the somewhat controversial "IBM service practice" of just clipping out the component and soldering the replacement to the remaining leads. I did not want to remove any boards, nor cause any new faults by introducing a bad solder joint that could not be located by flipping the board over. I don't have the confidence nor inclination to install and potentially diagnose a bag of tantalums soldered in that were viewed from only one side of the boards. A newbie can mange this type of repair.

I would like to thank the group, as I would never have attempted scope repairs without the information here.

I would also encourage anyone new to this to jump in, read the service manual (did I say yet "read the service manual"), patiently follow service steps, then ask for help.

Abc Xyz
 

Terrific! Now you can Fix mine! lol

On Sat, Mar 14, 2020, 11:29 PM Don N3DEB via Groups.Io <dbawatsonville=
yahoo.com@groups.io> wrote:

Had a backup 465B taken out of service sitting on my hobbyist repair bench
for about a year - long journey (hopefully) ended.

Symptom was losing trace after warm up, power supply folded over. The
folder over at first was after a few minutes, gradually occurring almost
immediately. While that seems like an easy fix based on all the group
discussion, it was not because of some cascading failures. I replaced the
power supply caps while I was at it.

All told I replaced quite an assortment of failed parts to get the trace
back that included voltage regulation components. I lost my patience
searching for the intermittent tantalum and injected DC slowly until I got
the expected but unnerving "Pop" and column of smoke. Replaced the roasted
peanut and got my trace back.

Next replaced the rest of the tantalums and the trace sharpened and other
performance issues corrected.

I often use the somewhat controversial "IBM service practice" of just
clipping out the component and soldering the replacement to the remaining
leads. I did not want to remove any boards, nor cause any new faults by
introducing a bad solder joint that could not be located by flipping the
board over. I don't have the confidence nor inclination to install and
potentially diagnose a bag of tantalums soldered in that were viewed from
only one side of the boards. A newbie can mange this type of repair.

I would like to thank the group, as I would never have attempted scope
repairs without the information here.

I would also encourage anyone new to this to jump in, read the service
manual (did I say yet "read the service manual"), patiently follow service
steps, then ask for help.