Well, Flukers (is that too crude? ) it looks like I have an 8800A/AF on the way. Guaranteed working, pictures supplied of the unit allegedly powered up and working in multiple modes. Fingers crossed, it's supposed to arrive tomorrow.
Now, business: this, and my 8600A, are likely in ticking time bomb mode as far as electrolytic caps are concerned. I've read almost all of this thread, and it seems maybe the aluminum poly caps are the best replacements? How about for replacing the tantalums? I'm putting together a BOM to get my meters updated so (without starting any arguments) what's the consensus?
My 8600A just had a major crap out due to tantalums. See here...
https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/msg1839170/#msg1839170
Revisiting this issue with the 8600A. It appeared at first that the drifting problem on the 20VDC range had been fixed. It wasn't. After the DMM was shut off for several hours on initial power up it was grossly inaccurate. For example: against a 9.99691V reference it would sometimes read as low 9.945V. Over the course of a half hour or so the voltage measurement would slowly increase to 9.997V and then remain stable. I finally traced this back to the DC input divider board and believe it or not it was one of the reed relays. When the relay was “cold” it had high contact resistance and as it warmed up the contact resistance decreased. And I proved it with freeze spray and a heat gun. Freeze spray would lower the measured voltage to as low as 9.7V and then apply heat and right back up to normal.
The 8600A has a total of 7 of these reed relays. 3 on the DC divider board, 1 on the Ohms board, and 3 on the AC board. I decided to change the reed relays on the DC divider and Ohms boards but for now leave the AC board alone since I don't have appropriate standards to perform a calibration. All of the reed relays are 5 volt coil and SPST NO type and they have a finite life span which after 40-45 years has been greatly exceeded. Obviously getting exact replacements is near impossible so I had to find acceptable substitutes. One of the items that needed to be checked was coil resistance. Turns out 1 relay had a coil resistance of 125 ohms and the other 3 had a coil resistance of 600 ohms (Didn't check the relays on the AC board).
Here's the DC Divider board. The reed relay on the left is 125 ohm coil, the 2 on the right are 600 ohm coil. The defective relay (K2) is in the lower right.
The Ohm's board. The single reed relay is 600 ohms coil.
Here's what I found for substitutes from Mouser. The bag on the left is a 125 ohm relay. Mouser P/N 934-HE3351A0500. The bag on the right are 500 ohm relays. Mouser P/N 934-HE3321A0400. I could not find 600 ohm relays that were reasonably priced so I decided to go with 500 ohm. The difference in drive current is about 2ma greater and I figured it would not be an issue (Proven to be true).
Here is the DC Divider board with the new relays installed. They are a smaller form factor so they are mounted sideways against the board and held in place with 3M automotive grade emblem tape. Then leads soldered to the pins.
The Ohms board. The relay mounted the same as the DC Divider board.
The results. No more drift. Accurate results right at power up. I also did a complete recalibration of the DC volts and Ohms. If you have a vintage Fluke with these reed relays I recommend changing them out before they cause problems. My 8800A has at least 4 of these reed relays and it's on my project list to replace them.