HP 5005B Signature Multimeter cleanup

I have been look­ing for a Hewlett Packard sig­na­ture ana­lyz­er for many years, but until I found this one they have either been in good shape and real­ly expen­sive or in poor shape and real­ly expensive.

Part of what I believe has kept the price high for the ana­lyz­ers has been the pop­u­lar­i­ty of peo­ple inter­est­ed in arcade game repair and restora­tion, as many of the game man­u­fac­tures used Signature Analyzers (SA’s) for trou­bleshoot­ing their games.
I feel very lucky to have come across this unit at a rea­son­able price. It was a bit dusty and dirty, with a small amount of rust on the HPIB con­nec­tor. The probe case and the tip also had some minor damage.

The unit had a pic­ture of it pow­ered up when sold, so I was­n’t in a big hur­ry to ini­tial­ly pow­er it on. I did my usu­al checks such as check­ing the volt­age set­ting, fuse, fan not stuck, and visu­al check for dam­aged com­po­nents, etc.
The first prob­lem that I ran into was a pair of the noto­ri­ous RIFA capac­i­tors locat­ed on the back of the AC pow­er input module.

Both capac­i­tors showed a sig­nif­i­cant amount of craz­ing on the back sides of the com­po­nents, but showed no signs of bloat­ing yet.
They were replaced with a new­er style of RIFA capac­i­tors that are epoxy pot­ted in a plas­tic shell. Hopefully much bet­ter than the old amber col­ored units.

Before tack­ling the dam­aged probe, I decid­ed to go though all the inner boards and pow­er sup­ply. The 5005B SA uses a fan to keep the inter­nals at a rea­son­able tem­per­a­ture, but in doing so also brings in a lot of dust and oth­er con­t­a­m­i­nants. Some areas have high imped­ance cir­cuit­ry requir­ing extreme clean­li­ness, so a very good clean­ing was necessary.

I unscrewed or lift­ed one lead on all the elec­trolyt­ic capac­i­tors on the main board and pow­er sup­ply. All the capac­i­tors test­ed in very good con­di­tion, except the small unit near the 4 ver­ti­cal heat-sinks. My assump­tion is that this capac­i­tor was in a hot­ter area of the board which caused some degra­da­tion. It was around 20% out of tol­er­ance with a high­er than nor­mal ESR read­ing, so was replaced.
Getting to the back side of the main board is no easy feat, as it must be par­tial­ly removed due to the frame cov­er­ing areas where the capac­i­tors are sol­dered to it.

A note on the A2 DVM board states: “CAUTION Extreme Cleanliness Required Minimize Handling”. This is due to the high-imped­ance cir­cuit­ry locat­ed on this board. The board was cleaned and rinsed sev­er­al times with 99.9% Isopropyl alco­hol, before it was reinstalled.

Just above the A2 DVM board in the stack is the A3 micro­proces­sor log­ic board with the “Test Number” selec­tor rotary switch­es. When trou­bleshoot­ing the 5005B the test num­ber switch­es place the unit into spe­cif­ic modes and con­di­tions allow­ing for ease of trou­bleshoot­ing the unit.

The very top board of the stack is the A8 HP-IB and dis­play board. Someone had been into this unit before me and used a blue sharpie to mark the con­nec­tors for some unknown rea­son, as it is almost impos­si­ble to plug the con­nec­tors into the wrong place.

After clean­ing all the boards and reassem­bly, it was time to tack­le the dam­aged data probe. The data probe had sev­er­al issues: The main body of the probe was deformed from some heavy object sit­ting on it for some peri­od of time, and the tip was no longer con­nect­ed to the cir­cuit board inside the probe body. I end­ed up using my heat gun on low to reform the plas­tic case until the two sides lined up and it was round again.
The screw on tip attach­es to a thread­ed met­al assem­bly that at one time was sol­dered to the cir­cuit board. With a lit­tle bit of cleanup the assem­bly was re-sol­dered to the board. Screwing on the probe tip locks the probe body and tip assem­bly in place.
I fab­ri­cat­ed a data probe ground wire and added a mini-grab­ber to replace the miss­ing part. I also added some mini-grab­bers to the tim­ing pod wires.

Now that the cleanup of the HP 5005B Signature Multimeter is com­plete all I need is some more bro­ken test equip­ment to use it on.