HP34401A

[lucian]

Ive noticed that these ic and the MCU are sitting around the mid 40's is this to be expected?

[Paceguy]

Open power supply filter caps can cause regulators to run very hot. Did you check the ESR of all the power supply caps ?

[lucian]

I sadly don't have a esr meter but I have checked the resistance using a multimeter and they are all very high so I don't think thats the issue

[Kleinstein]

DC resistance is very different from ESR.  High ESR would cause increasing power supply ripple. Instead of looking at the ESR one could also check the supply ripple with a scope and as a last resort a DMM (in AC mode).

The CPU can get a little warm, as it is a relatively old type and still running on 5 V. So it will use some power. It would be a bad sign if it is not getting warm.

[coromonadalix]

i would say,  yep  could be a case of bad capacitors ...  and while they are removed,  you could replace the small tantalums near them too   

with hot air   not an iron ..

[J-R]

https://xdevs.com/fix/hp34401a/

[lucian]

Does anyone have a list of the sizes of the different tantulum caps

[J-R]

Does anyone have a list of the sizes of the different tantulum caps

The link I posted has the service manual which has all that info.

[lucian]

It doesn't have the specific sizings

[JohanH]

It doesn't have the specific sizings

Here's the list of tantalums that I wrote down once, from the manual, but please double check:

C552, C554, C753 (main PCB)       1 uF ±20% 35 V tant (+18V rail) B-case (3.5 x 2.8mm)       
C616, C617, C602, C603, C604 (display)      1 uF ±20% 35 V tant (+18V rail) B-case (3.5 x 2.8mm) 
C411   4.7 uF ±20% 10 V B-case (3.5 x 2.8mm)   (C411 wrongly marked as L411 on component placement diagram)   
C311, C312, C322, C323, C557, C559     22 uF ±20% 20 V D-case (7.3 x 4.3mm)
C706, C512    47 uF ±20% 10 V D-case (7.3 x 4.3mm)

[J-R]

It doesn't have the specific sizings

OK, I thought you meant values not dimensions.  The service manual does have part numbers listed which can direct you to that info and an appropriate replacement.

If you don't have an LCR or ESR meter you could test the capacitors using a function gen and scope (out of circuit).