SONY FH-909 HiFi Stereo REPAIR Advice (repaired!) - Page 1
Forum section: electronics / repair

author: hgg
author_rank: Frequent Contributor
timestamp: October 18, 2013, 07:56:45 am
content: Hi,I have been using the SONY FH-909 hifi stereo for 30 years now with no problems.Excellent hifi. Lately though a problem appeared. Only at low volumes the soundis cutting out and coming back. Same sound as when you move a bad contact. Theproblem stops at higher volumes completely. If I increase the volume for some timeand then return to the same lower level it will play for a while normally but then itwill start to do the same on/off cutting again.I took apart the unit and to my surprise the amplifier board is quite small. From whatit seems all the work is done by a beefy integrated IC, STK4152II stero amplifier,made by ... SANYO.Anyway, two of the big capacitors are bulging. The ESR of all the big capacitors isborderline so I am guessing that they need replacement and most probably are thecause for the problem.My question is, apart from the capacitors, do you think that the problem might comefrom oxidised relay contacts? There is a replay on the board and from what I see itsconnected to the right and left of the signal. I am not sure why, but is there a possibilitythat the problem arises only at low volume due to contact oxidation ?Finally there are also 4 small transistors. Can they create a similar problem?Top ViewBottom ViewRelayThanks!George.

author: Stonent
author_rank: Super Contributor
timestamp: October 18, 2013, 08:12:45 am
content: Looks like a broken resistor over by R602.Can you get the part #s from the transistors? If they're common, and cheap, I'd say try swapping them out if the caps don't fix the problem.

author: hgg
author_rank: Frequent Contributor
timestamp: October 18, 2013, 08:35:35 am
content: That is actually the reflection of R602 on the red capacitor ...So, the little transistors can create the same problem?The transistors are C1841-EA83 and the small ones C2458-BL88

author: Stonent
author_rank: Super Contributor
timestamp: October 18, 2013, 08:52:17 am
content: Quote from: hgg on October 18, 2013, 08:35:35 amI suppose if somehow the bad caps were overloading them. Many computers with bad capacitors start to overheat.I'd just try the capacitors first.http://pdf1.alldatasheet.com/datasheet-pdf/view/108509/NEC/2SC1841.htmlhttp://pdf1.alldatasheet.com/datasheet-pdf/view/30102/TOSHIBA/2SC2458.html

author: hgg
author_rank: Frequent Contributor
timestamp: October 18, 2013, 08:56:12 am
content: Ok, I will start with the capacitors.Do we rule out the Relay?Thanks.

author: Stonent
author_rank: Super Contributor
timestamp: October 18, 2013, 09:02:00 am
content: Quote from: hgg on October 18, 2013, 08:56:12 amIt just doesn't seem like it would be that to me. On my stereo that I've had for about 20 years, I turn it on and there's about a 5 second delay and then the relay goes click and the sound starts.If you can easily get the cover off you can take some contact cleaner or sandpaper to the contacts if they look dirty.

author: hgg
author_rank: Frequent Contributor
timestamp: October 18, 2013, 09:21:14 am
content: I will try that as well. I am going to buy the capacitors right now!Thank you for your help!

author: David_AVD
author_rank: Super Contributor
timestamp: October 18, 2013, 09:37:07 am
content: Definitely change any bulging capacitors, even if they measure ok.Also check the smaller capacitors around the relay drive area. If they go low in value, the relay may not pull in reliably. It's a pretty common issue in older hi-fi amplifiers.You can also temporarily link out the relay contacts and see if the issue persists. I have seen relay contacts go bad, but it would be unusual for both to go intermittent together.Apart from all that, sometimes those STK series chips go bad. Surprisingly you can still buy many of them as a spare part.

author: amyk
author_rank: Super Contributor
timestamp: October 18, 2013, 11:53:34 am
content: Bulging Nichicons? That's unusual...

author: hgg
author_rank: Frequent Contributor
timestamp: October 18, 2013, 03:09:26 pm
content: I have just returned home with the new capacitors. Some cheap Chinese ones to see if I findthe fault. I will order some good ones later."David_AVD" hi, All the capacitors are measuring ok, apart from their ESR values which are borderline.I've also measured the resistors and they have very precise values! All of them are spot on!"Amyk", that's what I thought as well... The fact is though that was using the stereo for 30 years!Don't these capacitors have a lifetime hours limit?

author: hgg
author_rank: Frequent Contributor
timestamp: October 18, 2013, 05:45:38 pm
content: Epic FAILURE...I replaced all the capacitors except the smaller 1uF ones and while I saw a small difference,the problem was still there!I then turned on the stereo with a low volume level and tapped the relay with a small screwdriver.The sound stopped. I tapped it again and the sound returned. It looks like that the relay mightbe the real cause after all. I removed it from the board (and I stripped a contact as well..), I openedit and tried to clean its contacts. It fell to the ground and when I put it back, it stopped working...Now I need a new relay anyway!Do you know where I can find a compatible one?It has the following info:MATSUSHITAHB2a-YD-DC24-S05AV20HP125AC2A30V DCThanks.

author: SeanB
author_rank: Super Contributor
timestamp: October 18, 2013, 06:36:31 pm
content: It is a regular high sensitivity relay. Any one with the same pinout and with a 24V coil will fit, or you can just use a few short wires to connect the 6 pins you need and stick the relay where it will not be a problem, or use 6 short thick wires to hold it in the air above the board. Just measure the coil resistance and get the replacement with the same or within 5% of the value.

author: hgg
author_rank: Frequent Contributor
timestamp: October 18, 2013, 07:18:49 pm
content: Hi SeanB,The coil resistance is 770 Ohms.The hit to the floor killed it. It moves, but not enough to close the contacts, that's why I need anew one. The relay has 8 pins, but only 6 are connected on the board.1 2 3 4* * * ** * * *Column 1 is not connected. Column 3 is the coil.Its difficult to find a similar one and of good quality!Any ideas where to look?Will this do the job?:http://www.ebay.com/itm/10-x-F1CA024V-DC24V-8-Pins-Power-Relay-5A-AC250V-DC24V-1127R-FUJITSU-/350889682476?pt=LH_DefaultDomain_0&hash=item51b2a7a62c

author: hgg
author_rank: Frequent Contributor
timestamp: October 18, 2013, 08:17:01 pm
content: Repaired !!!It was the relay! The fall to the ground bent the spring that returns the armature to its originalposition. I managed to restore the spring tension and although it does not return all the way,when you apply voltage, it makes perfect contact.The volume works perfectly again!It looks like that when the volume (voltage) was low, the signal could not pass through the oxidizedrelay contacts creating the problem. Higher voltages though, could pass more easily.Anyway, thank you very much for your help.Although I cleaned the relay contacts, I think that I need to replace it with a new one,so if you can help me find a compatible one I would appreciated it.Thanks again.George.p.s. I replaced some high quality Nichicon capacitors with some cheap Chinese ones.Do you thing that they might affect the hifi sound quality?I didn't notice any difference yet.

author: fluxcapacitor
author_rank: Frequent Contributor
timestamp: October 18, 2013, 08:38:19 pm
content: If you need one in future :(Edited - Cheaper) :http://www.ebay.com/itm/370902829376?ru=http%3A%2F%2Fwww.ebay.com%2Fsch%2Fi.html%3F_sacat%3D0%26_from%3DR40%26_nkw%3D370902829376%26_rdc%3D1Only difference afaik is the Sealed amber case .

author: hgg
author_rank: Frequent Contributor
timestamp: October 18, 2013, 08:44:04 pm
content: Come on! How did you find it?! I could not find anything.Thank you very much indeed!

author: nithish
author_rank: Newbie
timestamp: March 28, 2018, 09:16:14 am
content: Hi dudeBro i have sony FH909R AMPLIFIER ITS ON BUT SOUND WHAT CAN I DO

author: David_AVD
author_rank: Super Contributor
timestamp: April 06, 2018, 10:06:48 pm
content: Quote from: nithish on March 28, 2018, 09:16:14 amYou can form a proper question and include some actual details.