|4th October 2006, 01:39 PM|
Join Date: Sep 2006
Yamaha C-85 Replacement Capacitors
I need to replace the electrolytic caps in my Yamaha C-85.
The volume control is making noise when I touch it(again);
the last time this happened, the repair shop replaced two of
the 4700 microF caps and it fixed the problem($80). This
time I want to increase the voltage rating on all the caps to at
least 50V. One of the power rails is 38VAC CT and the other
one is 50VAC CT. Taking the second one at
25VAC x 1.414 = 35VDC
But the second rail rectifies out at +/- 37VDC!
That is above the 35V for the filter caps. . .possible cause of
The preamp also runs HOT! (caps and transformer)
I've created vent holes to keep the temp down.
(I think that is the other factor killing the caps).
As always, size does matter! I can't go over 40mm high on any
cap. 35mm, 18mm, 15mm are max diameter sizes. There are
four each of the big caps and eight total small caps.
4,700 microF 35V ELNA Audio (new ones replaced where Nichicon)
1,000 microF 25V Nichicon
22 microF 25V Nichicon
Keeping with the same brand. I've found the following replacements:
Main Filter Caps
Nichicon FW Series 4700 microF 50V, 20mmx40mm 85C
Nichicon VZ Series 4700 microF 50V, 20mmx40mm High temp 105C
(in the $3.00 to $4.00 range)
Nichicon Audio KZ MUSE Series 1000 microF 50V, 18mmx40mm
(just over $2.00 each)
Nichicon Audio KZ MUSE Series 22 microF 50V, 8mmx11.5mm
(Less than $1.00 each)
Therefore, I put the following to all the DIYers:
**Best place to purchase caps.
**Better caps available. (Why!)
I would like to complete this project under $50 US.
|5th October 2006, 09:14 AM|
Join Date: Oct 2004
I have c-65 and have a problem with finding two new tone control pots. All preamps from c45 to c85 I think use the same pots. These are Alps dual centre detent 200k S curve four pin perch channel. Would you (or anybody else) know by any chance a source of such pots?
When it comes to caps the supply electros should replaced. They swell under heat. Apart from pots I have decided to change all electros in it and rectifying diodes to BYW100-200. The best source of capacitors are Handmade and Michael Percy. I decided to get four 8200mF/50V KG Nichicons from Michael. They are 35x45mm and should just fit in. Everywhere else Nichicon KG and FG 35V or 50V can be used where polarization is necessary, while bipolars can be replaced with Nichicon ES 50V caps.
Noisy volume control may result from too much DC geting there or from getting worn off. Yamaha used best Alps audio pots for volume and variable loudness so I think these should last longer than 20 years. replacing all electros in the circuit might help.
I also intend to replace all op-amps in tone, gain, loudness and headphone circuits with op-275 and opa2134 or opa2132 using brown dog adaptors.
|5th October 2006, 04:37 PM|
Join Date: Sep 2006
C-85 Decoupling Caps
I would search the internet for the ALPS pots. Other than that, I don;t
know where to find them.
I am quite sure it is the caps again since it is acting just like the last
time this happened. Like janusz stated, there is too much DC getting
into the signal. Causes buzzing and a distinctive "Tap" sound when touching it. . . less so with inputs shorted, but still there.
Thank you for the great advice on cap replacement. Since it worked
once(via repair man), I hope it will work again. I visited Michael
Percy web site. . .some expensive stuff. . .
Test your AC then DC. . .mine is very close to the 35V for the cap.
Good idea to up to 50 V caps on the supply.
Does your unit run HOT. . .transformer and class A amp section
get too hot to touch.
|5th October 2006, 11:20 PM|
Join Date: Sep 2006
Yamaha C-85 Update
After a long night and late morning start. .
Everything seems to be fine!
"Twigs don't snap themselves, Man!" The Blair Thumb
I pulled every connector off and reset them. I pulled the face-plate
off and re-tightened the volume control(wow, what a monster).
Reassembled. . . no snap, crackle, or pop. Something I touched
removed the grounding issue when touching the volume control.
Pushed down and tapped each solder connection to the main
caps(looking for bad connections). Makes me wonder about those crappy plastic connectors running signals here and there!
With the input shorted. . .dead silent except for some scratch at the
1 o'clock position.
With nothing connected, at 9.5 volume there is the introduction of
a noise at 3.5kHz. . .I figured the frequency by using the parametric
EQ at narrow and 100% cut, then sweeped the frequency band until
the noise dissappeared! It is very slight and only in the left channel.
After several hours of "ON" time, the buzz can't be heard -- or my
hearing is going.
Either a connector is bad/loose/crappy or I moved something that
was shorting(partial shorting) to ground. I think it might be wise
to clean the whole board.
I guess I will contiunue with the modifications that I originally
wanted to do. Previously (8 years ago) I drilled about 120 1/4"
holes in the area over the transformer (to vent heat).
(A) Open hole above transformer and install heatsink.
(B) Open hole above the Class A section and install a tiny
fan to vent the heat from that section. I don't want to drop
the heat too much since I want the section to keep warm and
stable. They are B949 and D1275 on two different heak sinks.
(C) Clamp or screw on to the existing heatsinks a auxillary heat
sink. . .it gets toasty in there. Give it a little more surface area.
Let me know what you think.
P.S. This preamp is used in a multi-amp and electronic crossover
setup. . .will start thread soon on that topic.
|6th October 2006, 02:34 AM|
Join Date: Sep 2006
Thanks for the parts pointers. . .for me or janusz it is another
avenue of possibilities.
As much as I like my Yamaha Equipment, Yamaha parts is way
to expensive. There stuff is 3x to 4x open market price.
Case in point:
I had (note the had) a CDX-930U(or something like that) that had
a spindle motor crap out. They wanted something like $48.45 for
the motor and just over $50.00 labor. . .with shipping it was going
to be something like 120 big ones! Ouch! I snail mailed about
10 people in the company over 8 months and got them to only
charge for 1/2 the labor and the part was free. I think it ended
up costing me just under $50. I haven't called or written them
And don't get me started about Sony. Which means "cow crap
that stupid Americans keep buying" in Japanese. They used to
be good until they got greedy. . . cheap microswitches made in
Malaysia and dip soldered.
Flog myself with a wet noodle 100 times for getting off topic.
Now I'm thinking of rewiring all the points that use the plastic
wire connectors (hardwire). With this little episode it looks
just like the time my Yamaha(yep, another piece of Yamaha
consumer electronics) cassette deck kept stopping in the middle
of play or record (about 35 minutes). Had it repaired before
I knew better (that was about $120 also, but in the late 80s).
After the repair. . .same darn thing happened again. Decided
to take fate into my own hands. Hours of poking later. . .crappy
plastic connector for connecting wires from the motor to the
PCB (sounds familar. . .I wonded if the same thing was happening
with the CD player). Rewired and it works to this day transfering
tapes to computer to CD to Customer then $$$s back to me!
Time to take some before pictures.
I wish my boss cared as much about the
business as I care about my equipment!
Thank you for the continued support!
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