Yamaha C4 Preamplifier Repair Brief
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- čas přidán 3. 06. 2013
- Mostly raw footage cleaning controls, replacing lamps, and general maintenance. As you can see, sometimes it ain't easy! Feel free to skip around. Shot this a year or two back - editing didn't go well, so did not post at the time. Presented here by request.
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Love your CZcams channel Keep it up your helping us repair old units from thank you
dude your a true pro...not just a capacitor fixer upper...ty,ty for posting this..and i love it was an hour long.
Missed your video's ! Glad a new one came along!
Glad to see that you made a new video....
Love the vids, I would like to see more troubleshooting too. I'm a trained tech, just haven't worked on audio gear much. I would also love to see a video on internal connector types. One of things that trips me up disassembling are the different connectors for ribbon cable and such that are tough to figure out how to disconnect without breaking a brittle plug or connector..
Fingers crossed I'll be getting one of these which needs a little attention. Those push buttons look a lot like ALPS (forgot the part number) I replaced a load in a soundcraft desk ages ago. What is the best way to clean the pots? In the past I'd open the pot and clean it with Isopropyl alcohol, then I got lazy and just sprayed it in but this would usually dry the pot out as it doesn't grease it. I also some times use contact cleaner some times but that tends to leave a bit of residue. Also where can you get the bulbs for these amps?
Been pretty lazy lately, and my outdated video software doesn't like my 720p Flip videos, but I'll see what I can do... Thanks for watching!
Mark nice video, quick question..I have finally got both channels running after lots of colder solder connections and a recap..the phono seems to sound tinny and moving those cartridge input impedance and Pf load switches doesn't seem to do a whole lot. Looking at schematic I see all the different resistors and caps around the slide switches. I put an ohmeter on the phono input say Phono 1, and turned the load Resistance pot, when I put it to 100 it did read almost 100 on my meter, but the rest as I go up stayed at 53k. Am I troubleshooting this correctly? If I turn the unit on and then run these tests then I get different values. Have you run into this issue before?
like allways great job, hope you uploud more repair videos soon
hey mark i have pioneer dvl-909 dvd player did not read dvd discs but read on cd and no audio coming out
Do have any videos on an onkyo ht r520 receiver? Problem is that it shuts off shortly after being turned on. I think it has a short but not really sure. I would appreciate any info on this issue.
the front lamps of which volts are? 12V o 6v?
Most Yamaha lamps are 14 volts at 60 mA if I remember correctly.
Hello,
Could a "bumpy" ride during shipment cause a loud humming noise to a once perfect sounding C-4? If so what should I look for first?
Thanks
rat mann I'd look for bad / broken solder connections, especially at the rear jacks.
Which key did you use to open up the main front panel switches? I have tried so many keys but none of them worked at all.
Thank you very much indeed!
Do you mean the hex keys to loosen the control knob? Not sure except they were metric.
Hi Mark I have a Yamaha C-4 and the left channel is weak and distorted, while the right channel sound perfect, what should I be looking for to correct the left channel?
Generally speaking - these model have lots of issues with bad solder connections and dirty controls, so I would tend to that first. Otherwise takes real troubleshooting, a job for a technician.
Hi mark I have quite a few 70s pioneer stereos and a marantz 79 model sitting in my room all the pioneers have no audio even when I plug in headphones they fully power on and light up but no sound at all do you know if they are worth fixing?
Mark, I'm about to re-do the power supply on my C4. What do you think about Nichicon PW for the electrolytic caps? This video is going to help a lot.
+Audioquest56 I think any high quality caps would be fine. Low esr, caps suitable for switching power supplies would be my choice. Nichicon is fine.
Nice video, I skipped ahead to the part I needed to see right away, the 21:00-22:00ish area where you worked on those push buttons for mono/stereo/rev. I will watch in it's entirety soon, thanks for doing this. Anyway, how would you address the sticking of one of these switches? The mono one gets stuck when I press the other switches and needs to be "helped" out. I deoxited it, checked the spring, etc. Step it up to Fader lube maybe? I have not laid the unit vertically yet as I didn't want to rest it on the rear terminals. Maybe I'll put it on a pillow or something.
Silicone wd40 and compressed air always give me good results with switches and buttons
I was in the middle of installing some new lamps and all was well.
While trying to install the last lamp all the lamps went out. Can the "-" and "+" wires touch because I'm guessing they did.
I'm new to this and thanks
Hi mark
Just buy a Yamaha c 4 preamp'
3 knobs missing like the the input selector
Can I buy some somewhere ?
Thank you from Montreal !
Maybe a parts unit from eBay. Most Yamaha knobs like that are brushed aluminum, not painted black so those would be harder to find.
Nice video. Wish you would explain have why you re- soldered the points you did.
This model is prone to many bad solder connections due to heat generated by some of the components - transistors, mainly, and the resulting thermal expansion and contraction as the parts heat and cool.
Have you given up on any new videos? I have enjoyed all that you have done so far.
Benjamin Lanza Thanks. My original intention was only to do a few. Might do another sometime - I'd like to show some troubleshooting. I've become more concerned that unqualified people are attempting things they shouldn't. Besides - everyone's such a CHEAPSKATE these days. It's a pet peeve and I'm less and less willing to help them
Hey Mark
I got my C-4 M-4 Set a year ago and i noticed some small issues.
the first one is not so terrible: when automuting is on, there is a little background noise. If the automuting is off there is no background noise at all-perfect sound.
Now the bigger problem:
Sometimes, the left channel stops working, it only plays at really low volume and with crackling. The right channel works fine. If i raise the volume and play something with a punchy base the left speaker starts working normaly again. This only happens in stereo mode (and reverse). Mono is fine. The thing is, i happens randomly. Sometimes it works for days and then it stops working for 30 minutes. It happens sometimes while already on for hours and sometimes just when powering it on. I dont understand what is broken, I hope I explained enough.
Greetings from Germany
oh, and theres a brumming sound on the headphone jack
I would start with cleaning the various controls and re-soldering any suspicious connections on that top circuit board(s) as shown in the video. Fixes most such problems with these.
+Mark Zacharias That was a quick answer! Thank you for that, i'll keep you running. If you have any other idea keep me up.
Hey Mark, I have a c4 Yamaha just like you were working on, I can hear out of headphones but not from speakers, any help would be great.. Thanks
The C-4 is a very complex unit as pre-amps go. I would simply have to try to trace the problem on the bench. I would say, most problems of this sort on a C-4 would come down to bad solder connections, which they were very prone to, or issues involving the power supply, muting circuit and capacitors.
Mark Zacharias
Thanks Mark, I did find 2 solder connections but that did not fix problem. I had this unit repaired 2 years ago for the same problem. Guess I'll take it back again. Thanks again.
Love the Kinks. Do you do repairs? I also have a C4.
Hi - I'm not able to take in repairs at this time; sorry.
hmm, I picked up a c4 yesterday, seems to be working well but i am considering keeping it forever, would you be interested and how much would it cost me to have you do a full service to it ?
+60ndown Probably a couple hundred plus return freight anyhow... we're in Wichita KS. 67208 zip code.
+Mark Zacharias thank you sounds good, I've been using it for a few days now, seems to be working fine.just 1 bulb out, does get warm, ill contact you for a service if and when it misbehaves :)
+60ndown Do contact first. We're probably closing the shop before the end of the year.
Hey - Thanks for watching. Hope to post something new soon.
Hi, i hv a pioneer vsx919ah. Today i switch on it, i notice the middle blue light dosent turn on anymore..... everything works normally but the light went out..... is it a sign of a problem with the receiver or is it jus the light went out? if it is the light went out, do u recommend repairing it? If it is a problem wh the receiver, what problem will it be? Thanks
nicholastmhsw What does the light normally signify?
Mark Zacharias not sure..... is the blue light in the middle of the receiver face which light up when the receiver was on.....
Mark Zacharias Hi, i read the manual book and it says if the blue light blinks means there is a problem in the power section..... wat could it be? mine didnt blinks but jus not light up..... the receiver works as usual, no problem..... after i shut it down for a few minutes, the light came bck on n off again after 30 minutes..... nw it is normal again for a few days already..... wat could b the problem? thanks.....
nicholastmhsw If the receiver functions normally otherwise I simply would not worry about it until I need to. This model is UNECONOMICAL to repair for a power amp problem. The power pack IC's are simply too expensive.
Dear sir
I have purchased yamaha c4 pre amp but it lights are very dim as power switch light is blown can please let me know its voltage so I can buy new
Thanks
Guru
Most Yamaha lamps of this sort are 14 volts.
Hi Mark,
this video is amazing thank you for posting.
I own a C4 with a small problem. When i turn it on it takes 40 minutes before i can hear something. All potis and buttons work fine, i cleaned everything. If you answer please use simple words because my english is not so good.
All the best wishes from Germany
There is a muting circuit involving TR621, 622, 623, and TR624 which may be malfunctioning.The relay is RY301 (probably a reed-relay).
Thank you very much for a ultra fast answer. Must i look for a bad soldered point or clean the button?
The best approach is to actually troubleshoot with digital multi-meter, oscilloscope, and so forth. This is a model C-4, yes? If so, then yes, they are prone to many bad solder connections. Always worth a try.
Hi Mark. Thanks for the video! My pre-amp keeps shorting out every time I turn it on. would that likely mean a blown fuse? Thanks again.
I need more information. What model is yours? What do you mean by "shorting out" ? Are channels dropping out? If so - one channel or both at the same time? That for example would not be a fuse.
Hi Mark just doing this amp C4 can you pls give me some info on this micron resistirs 37ma-180k there are 2 and no continuity are they fuse resistors
Sounds like you are trying to measure them in-circuit with a digital multimeter. This will often lead to erroneous results. Measure out of circuit or rely on voltage readings instead. I'm pretty sure the resistors are fine.
The fusing resistors are white. There is 4 85mA-330k showing continuity all 4 are good. The other 2 37mA-180k showing no continuity I have taken them out from board still no continuity. The board is where the head phoneplug is.
OK, we need to get on track here. First of all, I don't know for sure what resistors you are talking about. There are some 180 ohm (NOT Kohm) resistors in there. That changes everything. Please email me at mark_zacharias@labolgcbs.net and reverse labolgcbs to read sbcglobal. I'm going to want the resistor identifier numbers (locator numbers), like FR605 for example.
Hi Mark trying to send you email good due to your email can you send me an email i will reply audioclassic@ymail.com Thanks
I need to know the model numbers but this was a good time for Pioneer and Marantz. Maybe just some preamp - main amp jumpers missing at the rear panel, eh? Someone could have removed them to insert an equalizer in the signal path. If they are really broken, that's another matter.
Dont know if anybody has asked before, why dont you use a desodering gun? Looks like you desoder a lot. Im currently dissasambeling/recapping 2 Luxman M05 power amplifiers, and the task done with desoldering wig would be a bit up the hill. Btw always interresting to watch yours videos!
Been a while since you posted Mark can we have a fiew more please.
I've watched all 68 minutes of this 3 times now, made me buy a C4 for my collection, this is without doubt a really nice vintage pre-amp, now I need some other Yam equipment to match it, I like your videos, you certainly know your stuff and I would be fairly happy to pay you to service my gear instead of having to do it myself all of the time, ( If I lived in Murica, which unfortunately I do not ) , I do love my vintage HiFi, so my only criticism would be, I think your are a little bit rough with the gear, every screw head or hex nut is precious, as is every pot and switch, and a tiny scratch on the fascia is sacrilege, when it comes to classic HiFi, but still if I could post items to you economically for servicing, I would, you do a great job and probably quite cheaply too. i can do exactly the same , but this 68 minute job would take me 10 hours over a period of a week, I would be tempted to change caps. at the same time as they are cheap so the gear doesn't need servicing again in my lifetime.
Looks to me like the most likely thing is a blown fuse. There's a couple 1 amp fuses in there. One is probably bad.
Hello MZ , liked the Brief repair on the C4 pre amp. Need HELP,seriously....I use a C4 here in INDIA and the 'auto mut' on Start ON has gone rogue ...sometimes both channels play or PHONO/TAPE,,,,and sometimes only one channel plays right.
And sometimes while playing this particular channel goes bad again.
Seems like a switching transistor problem??
Similar problem on the M-35 Power Amplifier fro YAMAHA. The lights work, but the AUTO UTE circuit does not KICK-IN. No click noise before full power to the speakers.
I have access to trained people who work with SMD and discrete components.
BUT can you advise on the problem concerned??
Many Thanks. Manga.INDIA.
+Sunil Manga The C4 is prone to many potential bad solder connections on the main board. Often at the pre-out jacks but also at various transistors etc all over the board. A magnifying glass helps to find them. There is also a muting relay which could be flaky, (or a bad solder connection at the relay...) and there are switches on the front panel (I guess) to enable pre-out 1 or 2. One of these switches could be flaky. I'd be interested to know if the symptom also occurs when using headphones. Might help narrow it down a bit.
+Sunil Manga On the M-35: Do you mean the volume from the amp is there with no delay after power-up? Not a normal turn-on delay time?
+Mark Zacharias Thanks MZ
Yes the problem is still there even with headphones
Its taken me time to figure this auto mute problem
Definitely either a transistor or a dry solder
Can you suggest ,some simple checks?
+Mark Zacharias Hello MZ
In M35 the light comes On
But without the sound
The auto mute is stuck
Seems a regular problem with all the 1970's yamaha hifi
Any suggestions?
+Sunil Manga Sometimes just tapping on the board with a non-conductive item like a BIC pen or a chopstick will induce or affect the problem. Modifying the pressure or intensity of your tapping can help narrow down the search area for a bad connection. Might require actual troubleshooting with a 'scope and multimeter though.
This one was a couple hundred dollars. Might have been a little more but the fellow had an amp in at the same time.
Shows how much work can go into a simple control cleaning job. Devil is always in the details... Was an audio bench tech at a couple jobs three decades ago, then did a bit on the side from home. Then got into working on the 8 bit Atari stuff and later modulators and other CATV gear. Then drifted away from doing much bench work, but recently getting back into it a bit as I have quite a backup of audio projects and also learning about Arduino for some other projects.
The most likely thing on your Onkyo is a blown amp channel. I haven't a video on this, but another guy has a repair video on an Onk, maybe not the same model, but would be nearly the same parts, etc. Not for a newbie though - and the parts can be kinda special.
I know what you mean about people not appreciating the "simple repair" often said by non repair people, i have repaired equipment as well.
Stripping down multiswitches with lots of tiny sliders is fun not!! ha ha :-))
Your sound and video were out of synchronization.
Dont know if anybody has asked before, why dont you use a desodering gun? Looks like you desoder a lot. Im currently dissasambeling/recapping 2 Luxman M05 power amplifiers, and the task done with desoldering wig would be a bit up the hill. Btw always interresting to watch yours videos!
+John Michael Bech Yeah - I have one but it's old and cranky, like me! There's definitely times when it would work faster, but by the time I think of it, the job is done.