Kenwood TS-850SAT Modifications

Replacing the capacitors on the carrier board

In March 2006, several hams on the Yahoo TS-850 group began discussing a problem with intermittent output. It came out that some of the capacitors on the carrier board could fail, leaking caustic chemicals onto the board. The concensus is to replace these caps as soon as possible, to prevent problems that are likely to show up at some point in the future.

These apparently aren't rated for great long life in rough conditions, so being baked over the years inside the compartment can lead to failure. Replacing them with better capacitors can help keep your radio alive longer. If you want to get worried about it, read the Capacitor Plague article on compoent failures.

Take a look at the pictures taken by John (GM1BSG) to see what failures look like:


I haven't replaced mine yet, but opened it up today to see how many I had to order. It turns out there are:

Value Voltage Count

The carrier board is located under the shield below the accessories. Remove whatever cables you need, and remove the 6 screws holding down the shield.

The caps I found are marked with arrows:

Here's a close up:

I ended up replacing my caps with some from Mouser. The part numbers used were:

647-UUD1E470MCL - 47uf, 25v
647-UUD1E220MCL - 22uf, 25v (Mouser didn't have 10uf in stock)

You can get a look at the data sheet on the Mouser web site. I picked these because they seemed to have higher temp range and are SMD to match the ones it replaced. These are 25v which hopefully will give them a bit more headroom. The 22uf caps were slightly larger than the 10uf they replaced, but it wasn't a problem to get the pads and leads to match up. These caps are all on the V+ supply line to the digital chips, used to smooth out transients and noise that can get injected with digital switching. Going to the higher capacitor values isn't a problem in this case.

Clif, of Avvid Kenwood repair fame, made a comment on the Yahoo group that replacing all the caps probably isn't necessary. That may be true - apparently the 47uf is most likely to fail, occasionally the 10ufs. I'm probably being paranoid and replacing all of them is over-kill. In any case, I got some practice with SMD components and have a nicely working rig.

I hope this helps. If you have questions, you can contact me via email to my callsign at

- Dave

Fine Print Disclaimer - this worked well for me, but may not for your particular radio. If you wire things wrong, you may damage your radio and/or yourself. The author makes no guarantees about anything.

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