Tuesday, October 26, 2010

Kenwood filter fault fix

As the owner of a Kenwood TM-D710 I was interested to see that Anastasios, SV8YM, has developed a mod to fix the problem of the failing IF filters which causes these radios to go deaf after a couple of years. As explained in admirable detail in his original article describing the problem, it is caused by electromigration due to the fact that Kenwood omitted DC blocking capacitors on the input and output of the ceramic filters. This issue affects the TS2000 as well.

As you can see from Anastasios' excellent photographs, the mod involves cutting some tiny circuit board tracks, bridging between pairs of them with wire, then soldering 0.1uF SMD capacitors between the bridge and the filter input. The TM-D710 has two receivers, each with two filters (one for wide FM and one for narrow FM) each of which has both an input and an output that needs to be treated. So that is 16 tracks that need to be cut and 8 tiny capacitors inserted. I'm afraid working with these tiny components is beyond me, which is a shame as it is now, while my Kenwood is still only a few months old, that it needs to be treated.

Thanks to SV8YM for sharing the details of the modification.


Phil Terkoff said...

Another vital piece of news from you. I've suspected my 8-year-old TS2000 of being deaf for a few years now and now I know why! Thanks again and sorry for the stupid pseudonym. It was under that name that I blogged a while ago and I couldn't seem to change it last night.

GM4JPZ (in Abu Dhabi A6 right now)

Dave said...

Does anyone know if this fault also affects my Kenwood TS-480?

Unknown said...

I think the best way to find out would be to compare the schematic with that of the TS-2000 and see whether it has the same circuit around the IF filters.

IW1AYD said...

Hi all.

Older Kenwood doesn't have this problem. No notices of this fault for the TS-480, but a look on related Yahoo group may give further info abt.

The FT-857 and the FT-897 made by Yaesu have the same problem. But, more sporadicly, at least it seems. The same crackling noise is the symptom.

May be it was the same engineer that changed company or a common consultancy house.

What seems really strange is that those so called mistakes could be eliminated at the source simply by reading. Those filters have stated on theirs spec that DC biasing/coupling must be avoided. So those so called engineers doesn't read spec. Unbelievable.

The firmware blues of some radios could seems just a simple chain of news after reading about those cracked engineers and theirs dreams of MF filters coupling rules.

73 de iw1ayd Salvo

Fenris said...

I would expect that this sort of problem, caused by incorrect design, ought to be covered by Kenwood under warranty. Time for a call to the dealer that supplied it, or perhaps an email with a link to the details described in your posts.

Unknown said...

Unfortunately it seems that the problem only becomes apparent once the radio is out of warranty. There is a Yahoo group dedicated for these radios and I don't recall reading of anyone who managed to get this issue repaired under warranty. Someone in the group is compiling a database of issues to try to establish how prevalent the problem is. I would certainly advise anyone who owns one and isn't a member to join the group: http://groups.yahoo.com/group/TM-D710_TM-V71/

Fenris said...

Under the Sale and Supply of Goods Act, I think that if you can show that the product had a fault (even a potential one) in it at point of sale, then the retailer is responsible for dealing with it. The expected lifetime for electronics is a minimum of 6 years for the purposes of the act, so a 1 year warranty is irrelevant and doesn't affect your statutory rights.

Of course, showing this to the satisfaction of the dealer might not be too easy, but it's a sufficiently cut and dried case that Trading Standards (in the UK) ought to be prepared to help out.