Tek 465 Power Supply Rebuild

[nre_admin]

My 465 I've had since early 1980s gave up, the +5VDC regulated power supply rail gave up.  Pretty clear it was a shot filter capacitor, ripple voltage in excess on 600mV on the rail (should be <2mV).  Just putting a healthy 3000uF in parallel across the cap in question confirmed the diagnosis a broken to perfect trace immediately. 

These are an absolute bitch to remove without risking damaging the board traces.  Requires a desolder unit with vacuum activated trigger and a second iron in your hand to soften the other side of the joint.  You must use them both, simultaneously to remove the solder.  The good news is the caps had adequate clearance to get an iron at the top side of the joint.

Trigger board that must be removed.


Caps exposed with trigger board removed.


Caps removed, no trace damage.


Caps to be replaced.

[nre_admin]

This was the ripple voltage of the +5VDC rail.  Clearly the rail capacitor is toast.  Vertical scale is 1VDC/division.  Ripple should be <5mV.  DC coupling.

OUCH!!!

[nre_admin]

There are five Aluminum electrolytics in the 465 supply.  Three have their negative side to GND.
Theses are C1513, C1552 and C1542.  The original Mallory cans are the "-" side of the capacitor. Here, I'm using radial caps thus need to be creative.

C1512 and C1562 both have potential across the leads.  For C1512 about 65VDC and for C1562 it's about 13VDC.  Some thought is required to properly ground the entire supply. 

I've added jumpers to enable the proper grounding of circuit.  Rather than attempt to fill the large plated holes with solder I used terminal connections and screws. 

[nre_admin]

The location of each capacitor, from the bottom of the board.  Yellow are GND one end, pink are across potential.

[nre_admin]

Schematic

[nre_admin]

To remove these capacitors, I've had good results using both a temperature-controlled iron and a trigger actuated vacuum desoldering tool.  I heat the top side of the board with the iron and use the vacuum actuated desolder unit on the bottom side.  A clean-up with solder braid is all that's needed to loosen the cap and remove any residual solder from the joints.  The capacitor, if done properly, will release without any distress to the board traces.

[nre_admin]

Installation of new power supply filter capacitors.  All are PET dielectric, 105C, Nichicon and United Chemi-con.





   

[nre_admin]

55VDC supply and ripple voltage.



 
Back in business.

[nre_admin]

Here's my first stab at the 465 SN 250000-up electrolytic capacitor parts list.  The power supply caps are not listed here.  I'll add a separate list for those.

[HD1200xlh]

Well done. Congratulations, the end result is well worth the patience and time invested - that's a nice crisp display.

[nre_admin]

Well done. Congratulations, the end result is well worth the patience and time invested - that's a nice crisp display.

Thank you!  Having the right tools helps too.
jw