diff -r 6faac5ee8017 -r 9e963e155d4c content/hp8662a.rst --- a/content/hp8662a.rst Thu Nov 10 16:46:54 2022 +0100 +++ b/content/hp8662a.rst Thu Nov 10 17:26:20 2022 +0100 @@ -44,6 +44,7 @@ .. image:: {static}/images/hp8662a/dirty_hp.jpg :class: image-process-large-photo + :alt: Very dirty inside view of the HP8662A And I must say that if most of the unit is very easy to service due to the @@ -54,17 +55,21 @@ .. image:: {static}/images/hp8662a/top_before_2.jpg :class: image-process-large-photo + :alt: Top view of the inside of the HP8662A .. image:: {static}/images/hp8662a/bottom_before.jpg :class: image-process-large-photo + :alt: Bottom view of the inside of the HP8662A .. image:: {static}/images/hp8662a/front_after.jpg :class: image-process-large-photo + :alt: Fromt view of the inside of the HP8662A Also, there are hundreds of screws in this unit! it's insane. .. image:: {static}/images/hp8662a/top_after.jpg :class: image-process-large-photo + :alt: Top view of the many shielded compartments of the HP8662A Whatever, I finally got to a point I could clean most of the parts of the unit, so I started to reassemble it. Unfortunately, I did not took enough pictures @@ -73,13 +78,15 @@ .. image:: {static}/images/hp8662a/reassembling_2.jpg :class: image-process-large-photo + :alt: General view of the HP8662A case -Once I had the structure of the generator back togother, with the back plane in +Once I had the structure of the generator back together, with the back plane in place but no other board nor module plugged in, I started to take care of the PSU. .. image:: {static}/images/hp8662a/reassembling_1.jpg :class: image-process-large-photo + :alt: General view of the bottom of the HP8662A case with the main mother board The PSU ======= @@ -96,6 +103,7 @@ .. image:: {static}/images/hp8662a/PSU_simplified_schematic.jpeg :class: image-process-large-photo + :alt: Simplified schematics of the HP8662A PSU The 4 boards the PSU is made of are: @@ -116,6 +124,7 @@ .. image:: {static}/images/hp8662a/PSU_block_diagram.jpeg :class: image-process-large-photo + :alt: Block diagram of the HP8662A PSU So I gave a close look at thes boards, beginning by the main board, the I found the culprit for the smoke: the input protection thermistor. Strangely, it still @@ -128,6 +137,7 @@ .. image:: {static}/images/hp8662a/smoking_thermistor.jpg :class: image-process-large-photo + :alt: Picture of the smoked thermistor After this first step forward, I was not confident enought to plug the boards back in place and try again (I am always worried when I repair switching @@ -149,6 +159,7 @@ .. image:: {static}/images/hp8662a/PSU_inverter_schematic.jpeg :class: image-process-large-photo + :alt: Full schematic of the PSU Looking at the schematics and the boards, I did find several failure points: @@ -163,9 +174,11 @@ .. image:: {static}/images/hp8662a/broken_choke.jpg :class: image-process-large-photo + :alt: Pictures of broken choke coils .. image:: {static}/images/hp8662a/replacement_choke.jpg :class: image-process-large-photo + :alt: Picture of the replacement choke coils - there are 2 small 400mA fuses on the inverter board to protect the base of the 2 switching (bipolar!) transistors (first time I see the base of an NPN @@ -178,6 +191,7 @@ .. image:: {static}/images/hp8662a/fuse_replacement.jpeg :class: image-process-large-photo + :alt: Picture of the hacked replacement fuse After these fixes, I reassembled the PSU and tried again: the result was quite