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Ceramic filter failures in multimode rigs.
- Ceramic filter failures in multimode rigs.
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Ceramic filter failures in multimode rigs.
ZL3OZ > 30-09-2016, 03:16 PM
Had a Yaesu FT857 come in for repair with very sick receive sensitivity on FM mode mainly VHF was reported.
I found it actually still worked but RX sens was about -62dBm and the squelch could not be opened from the squelch control.
Also on SSB HF seemed at a first listen to be still ok but both sidebands hearable at the same tune by. i.e. like a double sideband receiver. (Never checked TX)
Did a search on Google and found many hits. It seems this is caused by breakdown of one or more of the ceramic 455 filters.
Usual configuration is an AM, a wideband FM and a narrow FM. (i.e three filters)(main SSB filters and CW filters not affected) and the FM one is the most likely culprit because it is most often selected (i.e. for the longest periods) and the manufacturers did not isolate the filter with caps so that the diode switching selection voltage is applied to the filter input and output as a byproduct after passing through the switching diode. This causes electron migration and a crystal buildup occurs across the tiny ceramic slices inside, shorting them out. Theres a heap on Google about dismantling and cleaning then out. I tried it and it was about 90% successful but very fiddly and still lost about 3dB more than it should.
Do a google search on ft857 filter problem or ft897 filter problems, and the iceberg starts to take shape, and this only the tip.
Also affected that I know about is the FT897, Ft817, Kenwood TS2000 and there will be others, not sure about Icom but someone said one of their marine radios is affected.
The radios all built between late 90s and 2009. Now reaching the crucial age.
I contacted Coms Centre in ZL and requested replacements. Well that was a waste of time and an argument into the bargain, seems they may not have them, might not want to supply them to anyone anyway because they are so hard to get.
I saw on line someone had found them available on ebay so thought "wonder what Aliexpress has to offer". There they were at very reasonable prices.
So if you have that trouble either go to Ali or contact me as I bought lots of 20 of all three types. So far two types have arrived and running the sig gen over them they are indeed filters and not what i feared, tiny bits of cleverly painted
wood.
Thought I would post it here as there will be quite a few of these rigs among us.
Ken
ZL3OZ -
Re: Ceramic filter failures in multimode rigs.
VK4ADC > 30-09-2016, 04:33 PM
Ken
I have a Yaesu VX7R handheld with the same issue although the ceramic filters in it are 450KHz rather than 455KHz and, yes, DC on the filter itself appears the cause of the issue. 2M FM sensitivity was around -50dBm with the faulty filter in circuit.
A Yaesu repairer in NSW supposedly had them in stock last year and I ordered them but they never did arrive. The VX7R remains faulty even now.
From my original enquiry email:
"Price and availability of TWO replacements for CF2002 and CF2003 in a VX7R handheld.
Original part was a Toyo ALFYM450F, original part number H3900531."
Maybe I should see if they area still available.
PS: This part has been replaced by Yaesu PN H3900572A or Yaesu TOKO A50FQ filter.
PPS: Just tried phoning them (RF Repairs at Wyong) and phone service has been disconnected so I guess that isn't a good sign.
PPPS: Just ordered some from radioshackus on eBay under listing
Replacement for YAESU VX-6R VX-7R Signal Crash 450F Filter 3 PCS Bundle
also available...
Replacement for YAESU FT-857/897 Signal Crash 455E/455G/455H Filter 3 PCS Bundle
Replacement for Kenwood TM-D710 Signal-Crash Filters 450E/450G Design issue
Kenwood TS-2000 Signal-Crash Filters 455E/455G Replacement Kits
YAESU FT-1802M Signal-Crash Filters 450F/450G Replacement Kits
Copy and paste the appropriate description into the eBay search box...
73 Doug VK4ADC -
Re: Ceramic filter failures in multimode rigs.
admin > 01-10-2016, 07:20 AM
Topic moved from General Discussion
Admin -
Re: Ceramic filter failures in multimode rigs.
ZL3OZ > 05-10-2016, 08:06 AM
Hi Doug
Hope it all works out and thanks for the added info. So someone has it sorted in available bundles.
Mine are all in now from AliExpress and it cost me about US$18 for enough to do about twenty ft857 rigs. i.e they were in bundles of 20 each for the H G and E type 455 filters. I had to buy them from three different sellers via AliExpress on free shipping china post.
Will get them fitted later in the week and see how it all goes. Theres a few spares here, tempted to send some to Yaesu agent for nix just to rub it in a bit. Why couldnt they have been a bit more proactive, I might have bought a new Yaesu instead of an Icom 7300 !
Admin, sorry didnt see the repair section the other day.
Ken
ZL3OZ -
Re: Ceramic filter failures in multimode rigs.
VK4ADC > 05-10-2016, 08:04 PM
The article at http://pages.cs.wisc.edu/~timc/e/vx7r/VX...er_fix.pdf is a must read as, while it deals with the VX-7R, it really applies to all of the Yaesu rigs that have DC voltage applied to the ceramic filters - and probably some other makes where they tried to save fitting two DC blocking caps on their PCB layout. This suggests how you can save yourself from the problem in the future ... when suitable replacement filters may not be available.
Modifying a currently good rig of these types as a precaution should also be considered.
The page at http://pages.cs.wisc.edu/~timc/e/vx7r.html provides more background too.
73 Doug VK4ADC -
Re: Ceramic filter failures in multimode rigs.
VK2AOH > 07-10-2016, 06:47 AM
Older GME UHF CB's such as TX3200/3400/4400 and some others suffer from the same condition. Poor sensitivity or "busy" indicator always locked on.
Some of the filters I replaced had a green tinge on the PCB which was a sure giveaway of a crook filter.
Uniden CB's which use the same filter suffer the same fate. -
Re: Ceramic filter failures in multimode rigs.
VK4ADC > 07-10-2016, 01:31 PM
VK2AOH Wrote:Some of the filters I replaced had a green tinge on the PCB which was a sure giveaway of a crook filter.
I have usually found that the green tinge effect on a PCB is actually corrosion induced from the device 'leaking' - which may be induced by the application of DC when there really should be DC blocking capacitors in circuit (eg ceramic filters). Those leaky devices are usually electrolytic capacitors (of one form or another) but could be almost anything similar depending on their construction.
The typical red/black wires from an external/connected battery make excellent conductive tubes to place their internal leakage chemicals to PCBs and make with the green effect too - with corrosion evident on both ends of the wire/s - and is usually open circuit because the internal wire has been eaten away.
73 Doug VK4ADC -
Re: Ceramic filter failures in multimode rigs.
ZL3OZ > 10-10-2016, 08:29 AM
Job all done. all three filters replaced and I cut tracks and fitted 0603 size 100nF caps where they always should have been (extremely fiddly job on tiny tracks with 0402or smaller resistors)and the Yaesu857 is good as gold again.
So I have 19 of each of the three filters in stock left over as I had bought lots of twenty each.
LTM455EW
LTM455GW
LTM455HW
Anyone want some my contact details can be found on VKLogger or QRZ.COM
Ken
ZL3OZ -
Re: Ceramic filter failures in multimode rigs.
VK4ADC > 01-11-2016, 09:05 AM
vk4adc Wrote:Replacement for YAESU VX-6R VX-7R Signal Crash 450F Filter 3 PCS Bundle
My ceramic filter problems in the VX-7R are now gone. The two new filters were fitted with small 100nF 0805 SMD-style DC blocking capacitors in series to each active signal point so now there is no DC on any of the filter pins. The PCB traces were not cut and I used mylar tape to provide insulation underneath so the filter pin leads could not contact the PCB holes directly. The sensitivity on 70cm seems normal although it has not been directly measured. The frequency display on 2m is flashing which (I think) means a PLL unlock state, but is normal on all other bands in the coverage. Maybe I disturbed something on the VHF section of the VCO submodule when I was working inside but I haven't yet pulled it apart again to check.
The three replacement filters were marked LTM 450FW on the case and since I only used two, that leaves me one spare.
Characteristics at http://pdf.eepw.com.cn/l20090915/7fd9c85...189c9c.pdf -
Re: Ceramic filter failures in multimode rigs.
ZR1WT > 21-03-2017, 08:37 PM
Hi Guys .. first post however only for the reason of trying to get hold of Ken ZL3OZ since I need a set of the filters for my 897. Ken if you do get this message please respond. if anybody has Ken's contact details or is in contact with him please convey my message to him.
I sent him a PM as well a few days ago to no avail ( so far ).
thanx so much.
rgs.