Tektronix TDS attenuator relays replacement

[eKretz]

After having multiple SPC failures on my Tek TDS754D I've taken it apart to replace the attenuator relays. It was also sickeningly filthy so I went ahead and washed all the boards then baked them dry. I've put everything back together now besides the acquisition board and am ready to work on the relays. I've disassembled the front end except for the ceramic boards - to get these out do I need to desolder the the connection to the BNC deep down in the housing? I don't want to mess these up so I thought it best to hopefully get the question answered by someone who has already done it. Anybody got a good source for the relays? Anybody have any success refreshing the old ones?

[eKretz]

Okeydoke, figured out how to get the boards out, on to replacing the relays.

[capt bullshot]

I once had just a bad solder joint on one of these relays. Re-soldering fixed this particular problem, no need to change the relay. I discovered the fault by testing the relays with a function gen set to 10Hz, and feeding this signal into the coil to recover worn out contacts. If you exercise the relay by rapidly switching on and off, the contacts get better (not always, and the effect doesn't last forever).
So just check the solder joints before removing the relays, it might be unnecessary.

[snoopy]

Okeydoke, figured out how to get the boards out, on to replacing the relays.

I just cut the relay pins and unsoldered the remaining stubs and replaced the lot of them. Some had even gone open circuit !! Don't muck around. Just order 16 of them and replace them all

cheers

[eKretz]

I think I'll just replace them also. I got a very attractive price on this scope so it won't really hurt the bottom line. It was less than a Rigol 1054 by a fair bit.

[eKretz]

I've done a 4-wire resistance check on the NC relay contacts I could reach, and some are within the 0.01 ohm to 0.02 ohm range but others are way high. I decided to swap in my attenuator assembly from my 754A which always passes SPC and it definitely cured the problem. I may just grab enough spare to do that board as well.