On 17 Sep 2022, at 15:21, Radu Bogdan Dicher <vondicher@...> wrote:

?

To prevent any confusion, when I said I am reading 40V instead of 55V, this is between the negative legs of C2 and C4. Not at either one's legs vs ground, or over either one.?

This replicates step 2 from Service Group 8 (p.8-F-1). There was no way to connect to what they're calling for ("the junction of R1 and CR2 and R2 and CR4").?

Hopefully this helps with the clarity of my empirical data.?

Radu.??

On Sat, Sep 17, 2022 at 11:13 AM Radu Bogdan Dicher via <vondicher=[email protected]> wrote:

Hi Patricio,

One overall conclusion is that all rails are down by about 30% (mind you, the same rate). Given they're all referenced to the +15V rail, the running assumption is that something's wrong with the?+15V regulator.

I see less than 1.8V over C2.

Radu.??

On Sat, Sep 17, 2022 at 10:15 AM Patricio A. Greco via <patricio_greco=[email protected]> wrote:

Please note that the voltage outputs are : + - 15 vdc , 5 vdc and -5.2 Vdc … If C2 has > 40 Vdc is ok. Please take a look to power supply schematic …

Ing. Patricio A. Greco
Taller Aeronáutico de Reparación 1B-349
Organización de Mantenimiento Aeronáutico de la Defensa OMAD-001
Gral. Martín Rodríguez 2159
San Miguel (1663)
Buenos Aires
T:?+5411-4455-2557
F:?+5411-4032-0072

On 17 Sep 2022, at 12:39, Radu Bogdan Dicher <vondicher@...> wrote:

?

I whipped out my longest probes - an inspired overstock purchase from maybe Anchor near SF?... - (pictures added to album, hoping they give some ideas to others get that deep inside the belly of this unit) - and I am getting 40V at the minus leg of C2 and C4 (my probing points), vs. an expected 55V. Interestingly, as soon as I power off the unit, the voltage there jumps up to about 45V, and even raises a bit more as the unit is standing powered off (5 minutes later I measure about 47V...).

Continuing my investigation.?

Radu.?

On Sat, Sep 17, 2022 at 6:01 AM Radu Bogdan Dicher via <vondicher=[email protected]> wrote:

Thank you all for sharing your thoughts.?

I tried sending some pictures yesterday by replying to the email chain with attachments, but in doing so I exceeded the max size. I created a photo album?instead:?/g/HP-Agilent-Keysight-equipment/album?id=278590.?

Will keep investigating this morning. I'm surprised?to not find some paragraphs on removing (each) modules in their troubleshooting sections (typically with images), which I expect from an HP manual (particularly component-level). Anyway, that concludes my whining and will go ahead and dig in there more vigorously.?

Radu.?

On Sat, Sep 17, 2022 at 5:25 AM Patricio A. Greco via <patricio_greco=[email protected]> wrote:

I have a HP3335A. I started to experiment problems as cpu freeze and leveling errors and I found microscopic cracks on power supply board also I removed the transistors and found an anormal slope on characteristic curves (this is thermal deterioration). Replaced the transistors and re-soldered the complete board, Also I removed the capacitors for test , these was ok . Cleaned the contacts and mounted again. After that work, instrument started to work like never. It??s very very flat, let me show you the results. I attached the response curves I measured. X Avis is logarithmic starting @1 MHz , and Y Axis is in dB relative to 1 MHz. I used 3 different methods to measure.?

Regards,?

Ing. Patricio A. Greco
Taller Aeronáutico de Reparación 1B-349
Organización de Mantenimiento?Aeronáutico de la Defensa OMAD-001
Laboratorio de Calibración ISO 17025?AREA: RF/MW?
Gral. Martín Rodríguez 2159
San Miguel (1663)
Buenos Aires
T: +5411-4455-2557
F: +5411-4032-0072

On 17 Sep 2022, at 08:01, Harold Foster <halfoster@...> wrote:

Taking the assemblies loose is almost essential to troubleshooting the supply boards, but very important: You have to install a jumper to reconnect the ground - the boards are grounded through one of the brackets (the one to the bottom of the chassis if I remember correctly) and will be disconnected when it it taken loose.

Hal