Well, it could be a false alarm (pun intended) but lately I have been getting more and more rigs for repairs, and from diferent manufacturers, with bad Toko black ceramic filters (6 and 9 kHz by now)
I have fixed three rigs in the last few weeks with this problem, two Yaesu FT-897 and one Kenwood TS-2000. Symptoms could range from lower sensitivity, to cracking noises and, usually, you have both. There is also an interesting effect, at least on FT-897s, which is that they receive in DSB instead of SSB when filter fails.
I have opened one filter and it had some greenish looking residue on it, so I guess sealing had failed and moisture did the dirty job.
I would be interested in hearing other people experiences with those small "BLACK NOISIES" (*) (remember you saw it first here, (c) EB5AGV ;-) )
Best regards,
JOSE
(*) the equivalent to "BLACK BEAUTIES" caps in old boatanchors!
12 comments:
Thanks for the info, Jose. Recently acquired a Yaesu 7800, and a Kenwood TS-480 SAT. Will now be wary of that happening to my rigs.
73,
Larry, WA9GUU
This happened to my FT857D. In that rig, the schematic shows that the diode DC switching voltage is applied to the Toko AM ceramic filter, although the Toko data sheet says that a DC blocking capacitor should be used. The problem is not the filter, it's that the rig design overlooked the need to avoid applying DC voltage to the filter. I simply added 0.01 microF capacitors at the input and output, and that cured the problem without having to replace the filter. From what I've heard, if this is left unchecked then the filter deteriorates and has to be replaced too. The filter is cheap, but replacing it (as you know) may take a lot of labor.
I've posted a file describing that repair to the Yahoo FT857D group.
73
Darrel, aa7fv.
Hola José. Mi FT-857D sufre de el mismo defecto. Empezó con muchos estáticos en el receptor, y en el audio del transmisión, y ahora, recibe DSB con muy poca sensibilidad, y en TX parecen haber desapárecido los estáticos!. El CF 1005 parece haberse definitivamente estropeado, así que he encargado el repuesto, y lo cambiaré. Si os interesa posteré mis resultados. Saludos. Leandro.
LU8AOI
Finally, The replacement of CF1005 cure the problem in my FT-857D. I've to wait the filter one month to arrive to this latitudes, and change it took me like one our (between remove the board, and reasemble all together). I didn't make the modification that Darrel propose (wich is also recomended in the datasheets of the filter, but only in the output lead), so let's see how much takes to repeat the failure (hopefuly, a very long time).
73s, Leandro LU8AOI
Hello Leandro,
Thanks for letting us know about your experience. I have so far replaced three damaged filters in different rigs and I am afraid lots more are on its way.
73 JOSE EB5AGV
Hola José:
Encontré el mismo problema en un TS-2000, los filtros cerámicos CF1, CF2, CF3 y CF4 presentan una baja resistencia a tierra (aprox 90 ohms) Probé a sustituirlos con otros Murata y funciona bien, pero son de diferente tamaño. Pedí ya nuevos filtros a Kenwood y espero los nuevos no den problemas. (En mas de 20 años de reparar radios únicamente he cambiado un filtro cerámico) 73´s Guillermo XE1GFF
Good afternoon Jose.
Following your tips replaces all of my ceramic filters FT 857, including CFJ455K14, bought all direct yaesu USA. Solved the problem of USB and LSB reception they were receiving in both DSB. It remained a problem, the FM sensitivity is normal, when moving to any AM or SSB S9 +30 signal before passing the S8 or S9. I am suspicious of D1076, D1078, D1068.
I would love to get your opinion before I venture to replace these diodes SMD.
Thank you!
73 of PY5KC
Alessandro
acscwb@bol.com.br
Hi everbody . I would like to thank particularly EA5AGV Jose and AA7FV Darrel and general thank for others OM contibutions.
I've purchased a second hand FT 857D (2007 model), like new because never been powered before me !
Unfortunatly I notice immediatly the crackling noise on my 857D .
I've been convinced in adding the 10 nF smd capacitors , because beeing new this radio shouldn't be bad !
I operate myself my FT857D and with time and its now REPARED !!
It's unbelivable , why didn't Yaesu engeneers put these recommanded capacitor ???!!
At last i've also purchased a TS2000 whithout any problem !o)
73 and Thanks for reading .
F5RAG Iñaki.
Saludos , amitiés .
Hope to Ear you on this air .
good day my friend!
i would like to share this about ceramic filters which i found on the net:
http://sv8ym.blogspot.com/2010/07/mysterious-case-of-withering-filters.html
nice website, very informative, keep the good work! i learned a lot from this site! tnx
dw2nah/jonathan
ilocos sur, philippines
Greetings Jose,
Sad to say, the ceramic filter misuse problem appears in quite a lot of other receiving gear as well. I, too, stared with disbelief when I saw sizable DC voltages being applied to ceramic filters. The result is slow degradation over time, just as you've noted; either the receiver goes deaf, or it develops a case of the crackles. I just replaced three failed ceramic filters in a Realistic STA-90 (ca. 1976) that was deaf to the world -- all three of the filters see 5 vdc or more when the unit is operating.
Thanks for the informative site!
73,
Tom N0GSG
http://n0gsg.no-ip.org
These filters are also found in the Vertex Standard series of commercial radios. They are dropping like flies. Especially the VX2200 VHF and the VX354 VHF. The symptom shows up after reprogramming channels to narrow band 12.5 from customers using only wide band. And by then the radios are out of warranty. Talk about mad customers.... And worse, Im scared to put the TOKO filters back in. I'm having a time trying to find replacements by another brand.
A frustrated Vertex Standard dealer...
Hola/Hey Jose and folks! Que tal? Tnx for the info. Seems to be that Vertex Standard VX-351, 351PMR and VX-146 have the same problem. 73 de Jukka OH2JIN
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