HP 5890 IIA GC- oven and fan not turning on

[Vivagen]

I'm attempting to repair an HP 5890 IIA GC coupled with an HP 5970 MSD and am having quite the major issue with the 5890. The oven and fan do not turn on! A few symptoms:

-the "oven temp" button on the front of the instrument is completely non-responsive.
-timed events run fine, programmed heating sequences progress correctly, no problem with internal clock.
-does not pass the self-check due to me not having installed the detector yet. (WARN: DETECTOR NOT INSTALLED) there is nothing about the oven in these initial error messages.
-the "not ready" light stays on solid because the oven temperature is not ready.
-the fan blades are not frozen; when prodded they freely rotate
-there is no evidence of scorching or heat damage (though i have not taken out the fan to look at the heating element)
-We tested the fuses on the AC power board and they are all fine.

At the moment we suspect that K1 on our AC power board (PCB 05890-60050) may not be working and i would greatly appreciate if anyone had schematics showing electricity flows for this board they'd like to share. And any ideas or comments would be greatly appreciated!

[rb6banjo]

Try this:

http://www.chem.agilent.com/Library/Sup ... a15307.pdf

Maybe that document will help you.

[cleh]

The self test is normal because, as you said, you don't have detectors installed. Is this an instrument that has been operating and this just started happening? Are you pressing oven temp and then on and the fan isn't operating? It could be a bad keyboard if you can't get the oven temp button to work but you can get the injector and detector temp to respond and turn on and off. Please let us know what you find.

[uzman]

Disassemble the keyboard carefully , and you will find a flexible resistor pack between two electronic boards.

Clean the sides of this resistor pack with a lint free tissue , moistened with methanol.

Assemble the keyboard , and push '' oven '' , then ''on'' buttons to check if it is successfull.

[freddiespedalo]

Before I worried about the boards I would confirm that the heating element is not broken/fused.

[uzman]

Dear Freddiespedalo ,

It is stated that '' fan is not turning ''
If it was a heater problem , fan will turn but the oven will not heat .

I insist on a keyboard problem.

[cleh]

Agree with uzman. You should be able to press the oven temp button and then press on or off to turn the fan and heater on or off. You said the oven temp button is not responding so it sounds like it's a keyboard problem.

[Vivagen]

Hello! Here to post an update, thank you for all the wonderful suggestions! It was indeed as simple as fixing the button. Because the button was nonfunctional, it was not possible to access the "oven temp" subroutine which is, apparently, the only way to turn the oven/fan "on." Once the button was bypassed the system operated normally.