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
dying caps?
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
or
Nichicon VZ Series 4700 microF 50V, 20mmx40mm High temp 105C
(in the $3.00 to $4.00 range)
Others
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.
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
dying caps?
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
or
Nichicon VZ Series 4700 microF 50V, 20mmx40mm High temp 105C
(in the $3.00 to $4.00 range)
Others
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.
c-85
Hi gni,
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.
cheers,
Hi gni,
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.
cheers,
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.
Chris
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.
Chris
Yamaha C-85 Update
UPDATE[\B]
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.
Chris Browne
Northern California
P.S. This preamp is used in a multi-amp and electronic crossover
setup. . .will start thread soon on that topic.
UPDATE
UPDATE[\B]
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.
Chris Browne
Northern California
P.S. This preamp is used in a multi-amp and electronic crossover
setup. . .will start thread soon on that topic.
UPDATE
Yamaha Parts
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
since.
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 $$$s back to me!
Time to take some before pictures.
Chris Browne
I wish my boss cared as much about the
business as I care about my equipment!
Thank you for the continued support!
Thanks for the parts pointers. . .for me or janusz it is another
avenue of possibilities.
As much as I like my Yamaha Equipment, Yamaha parts is way
to expensive. There stuff is 3x to 4x open market price.
Case in point:
I had (note the had) a CDX-930U(or something like that) that had
a spindle motor crap out. They wanted something like $48.45 for
the motor and just over $50.00 labor. . .with shipping it was going
to be something like 120 big ones! Ouch! I snail mailed about
10 people in the company over 8 months and got them to only
charge for 1/2 the labor and the part was free. I think it ended
up costing me just under $50. I haven't called or written them
since.
And don't get me started about Sony. Which means "cow crap
that stupid Americans keep buying" in Japanese. They used to
be good until they got greedy. . . cheap microswitches made in
Malaysia and dip soldered.
Flog myself with a wet noodle 100 times for getting off topic.
Now I'm thinking of rewiring all the points that use the plastic
wire connectors (hardwire). With this little episode it looks
just like the time my Yamaha(yep, another piece of Yamaha
consumer electronics) cassette deck kept stopping in the middle
of play or record (about 35 minutes). Had it repaired before
I knew better (that was about $120 also, but in the late 80s).
After the repair. . .same darn thing happened again. Decided
to take fate into my own hands. Hours of poking later. . .crappy
plastic connector for connecting wires from the motor to the
PCB (sounds familar. . .I wonded if the same thing was happening
with the CD player). Rewired and it works to this day transfering
tapes to computer to CD to Customer then $$$s back to me!
Time to take some before pictures.
Chris Browne
I wish my boss cared as much about the
business as I care about my equipment!
Thank you for the continued support!
yamaha
Hi,
I have contacted Yamaha Australia and Japan. Yamaha Japan sent my enquiry back to Australia and I was told twice the same thing - the preamp is 20 years old and there are no parts. Maybe Yamaha USA is better.
I looked at PartsSource site but it looks like a medical equipment supplier and their enquiry form looks like they are dealing with businesses only. I may invent a company for myself but have no idea what model these pots are and what is their part number. Anyway I'll try. Thanks for s suggestion.
Preamps power supply runs hot and 4700uF caps are swallen from heat. Drilling the cover to vent the transformer is a good idea.
I have bought my preamp just recently on Ebay and had to dismantle it straight away as tone control pots were noisy and treble pot acted as a secondary volume. Never encountered a problem like that. With main volume set to whatever level turning the treble pot left would take sound level to almost zero, while turning it right would bring it to a level set by the volume pot. Would anyone know what is wrong?
Variable loudness does a similar thing. Instead taking centre frequencies down it brings everything down. Lodness and tone control circuits are somewhat connected so I suspect faulty caps but there might be other things. Any idea what else?
That 3.5kHz resonance must be generated somewhere. Capacitance and inductance must be involved. Check the diagram and try to locate its source. Try to measure AC from the output backward until you'll find it.
You may also resolder all pot and switch joints and whatever looks suspicious. Soldering on my c65 looks good to me. I had to desolder four tone control pots, balance pot and one switch and original soldering looked good to me.
The good thing about these c series preamps is that most things on boards (except for pots) are accessible without dismantling and tracks are as wide as possible. That makes repairs easier and tracks more secure to multiple soldering attempts.
cheers,
Hi,
I have contacted Yamaha Australia and Japan. Yamaha Japan sent my enquiry back to Australia and I was told twice the same thing - the preamp is 20 years old and there are no parts. Maybe Yamaha USA is better.
I looked at PartsSource site but it looks like a medical equipment supplier and their enquiry form looks like they are dealing with businesses only. I may invent a company for myself but have no idea what model these pots are and what is their part number. Anyway I'll try. Thanks for s suggestion.
Preamps power supply runs hot and 4700uF caps are swallen from heat. Drilling the cover to vent the transformer is a good idea.
I have bought my preamp just recently on Ebay and had to dismantle it straight away as tone control pots were noisy and treble pot acted as a secondary volume. Never encountered a problem like that. With main volume set to whatever level turning the treble pot left would take sound level to almost zero, while turning it right would bring it to a level set by the volume pot. Would anyone know what is wrong?
Variable loudness does a similar thing. Instead taking centre frequencies down it brings everything down. Lodness and tone control circuits are somewhat connected so I suspect faulty caps but there might be other things. Any idea what else?
That 3.5kHz resonance must be generated somewhere. Capacitance and inductance must be involved. Check the diagram and try to locate its source. Try to measure AC from the output backward until you'll find it.
You may also resolder all pot and switch joints and whatever looks suspicious. Soldering on my c65 looks good to me. I had to desolder four tone control pots, balance pot and one switch and original soldering looked good to me.
The good thing about these c series preamps is that most things on boards (except for pots) are accessible without dismantling and tracks are as wide as possible. That makes repairs easier and tracks more secure to multiple soldering attempts.
cheers,
Yamaha C Series Preamps
janusz,
I agree that the amps are built well in many aspects. . .accessibility
is quite wonderful. . .except behind the volume control. . .you need
to remove the front panel. . .then the side panel. . .or front then
both retaining screws for the balance and Volume. . .
Sorry about the funky problems with the pots. . . sound like a short
to me. . .but I should speak. . .I'm not sure of my problem. . .maybe
Prozac? ; - )
I'll snap some shots of the C-85 mods. . . parts are probably
going to be similar, but not actual parts. . .some are funky and
look custom! If you see my unit. . .maybe it (seeing that my
circuit is working -- the volume and tone control) will allow you
to see the problem with your circuit. . .you might need to pull
the pots and measure them. . .short it possible. I think they
say what value they are.
Mine are 90Kx4, 20Kx4 for the frequency set, and 70K+200K level
and bandwidth control.
Volume is an ALPS with 6 units. . . 53Kx2, 10Kx2, 50Kx2. . .
It seems like there should only be 4 units. . .2 for volume, 2 for loudness. . . it must create some hybrid so the volume is smooth
from low to high. . .or so the loudness works. . .
One way to test that I might do is:
Pull the pots and test them. . .put into (solder) a resistor of
a value that will make the tone flat, or volume is about 25%. . .
so you can monitor. It seems if the pots are bad. . .resistors
can substitue for a normal value. . .if problem persists. . .look
to the caps (I don't like them. . .dry out. . .explode, leak,
20% tolerance).
Some solder joints on mine had the component leads bent over
for soldering, but the lead was long enough to extend over the
PCB trace. . .I heated and bent up these. . .most were in the front
of the unit. . .near the tone controls in fact. Makes me think.
The transformer is just a transformer gunked into a metal case
that looks pretty. I pulled mine to move the wires and there is
hard brown resin and suspended in it is the transformer. . .that
looks like a cheap radio shack transformer.
The cover above the Class A section has a rubber like square
glued to it. . .heat dispertion?. . .I've always used the preamp
on top due to the heat it generated.
I was thinking of putting the small fan in the back panel where
the 220/110 voltage selector switch is located. Maybe a screened
vent in the bottom plate. . .suck air from the bottom of the unit
up around the PCB and out the back. . .
Let me know if this sounds good. I will continue to think about
the volume / tone control problem on your C-65.
Why the BYW100-200 to replace the rectifier diodes. . .mine are
clear glass with orange inside?
"The best source of capacitors are Handmade and
Michael Percy. The four 8200mF/50V KG Nichicons
from Michael. They are 35x45mm "
I just remeasured and the original Audio ELNAs are 40mm high
and them replaced ones are Audio nippon at 42mm The PCB to
Lid is 47mm with rubber stand-offs. Have you installed them yet.
Chris
janusz,
I agree that the amps are built well in many aspects. . .accessibility
is quite wonderful. . .except behind the volume control. . .you need
to remove the front panel. . .then the side panel. . .or front then
both retaining screws for the balance and Volume. . .
Sorry about the funky problems with the pots. . . sound like a short
to me. . .but I should speak. . .I'm not sure of my problem. . .maybe
Prozac? ; - )
I'll snap some shots of the C-85 mods. . . parts are probably
going to be similar, but not actual parts. . .some are funky and
look custom! If you see my unit. . .maybe it (seeing that my
circuit is working -- the volume and tone control) will allow you
to see the problem with your circuit. . .you might need to pull
the pots and measure them. . .short it possible. I think they
say what value they are.
Mine are 90Kx4, 20Kx4 for the frequency set, and 70K+200K level
and bandwidth control.
Volume is an ALPS with 6 units. . . 53Kx2, 10Kx2, 50Kx2. . .
It seems like there should only be 4 units. . .2 for volume, 2 for loudness. . . it must create some hybrid so the volume is smooth
from low to high. . .or so the loudness works. . .
One way to test that I might do is:
Pull the pots and test them. . .put into (solder) a resistor of
a value that will make the tone flat, or volume is about 25%. . .
so you can monitor. It seems if the pots are bad. . .resistors
can substitue for a normal value. . .if problem persists. . .look
to the caps (I don't like them. . .dry out. . .explode, leak,
20% tolerance).
Some solder joints on mine had the component leads bent over
for soldering, but the lead was long enough to extend over the
PCB trace. . .I heated and bent up these. . .most were in the front
of the unit. . .near the tone controls in fact. Makes me think.
The transformer is just a transformer gunked into a metal case
that looks pretty. I pulled mine to move the wires and there is
hard brown resin and suspended in it is the transformer. . .that
looks like a cheap radio shack transformer.
The cover above the Class A section has a rubber like square
glued to it. . .heat dispertion?. . .I've always used the preamp
on top due to the heat it generated.
I was thinking of putting the small fan in the back panel where
the 220/110 voltage selector switch is located. Maybe a screened
vent in the bottom plate. . .suck air from the bottom of the unit
up around the PCB and out the back. . .
Let me know if this sounds good. I will continue to think about
the volume / tone control problem on your C-65.
Why the BYW100-200 to replace the rectifier diodes. . .mine are
clear glass with orange inside?
"The best source of capacitors are Handmade and
Michael Percy. The four 8200mF/50V KG Nichicons
from Michael. They are 35x45mm "
I just remeasured and the original Audio ELNAs are 40mm high
and them replaced ones are Audio nippon at 42mm The PCB to
Lid is 47mm with rubber stand-offs. Have you installed them yet.
Chris
Yamaha C-85 Mod pictures
Here is the link again. . .with new C-85 closeups. . .I'm really
thinking a fan in the voltage selector slot is a good idea. . And
a Processor fan and heatsink on the transformer! Just the right
size. . .That would require a hold in the top cover. . .things sticking
out. . .but tube people have the same problem.
Take a look. . .I think looking at a similar unit might help. . .
Chris
http://arts2001photo.lifepics.com/a/v.cfm?h=CB59E3A7
PS. . .I work at Arts 2001 Photo. . .
Here is the link again. . .with new C-85 closeups. . .I'm really
thinking a fan in the voltage selector slot is a good idea. . And
a Processor fan and heatsink on the transformer! Just the right
size. . .That would require a hold in the top cover. . .things sticking
out. . .but tube people have the same problem.
Take a look. . .I think looking at a similar unit might help. . .
Chris
http://arts2001photo.lifepics.com/a/v.cfm?h=CB59E3A7
PS. . .I work at Arts 2001 Photo. . .
yamaha
Hi Chris,
I have dismantled the whole preamp and removed all pots except for tone-loudness control as these are quiet in my c65. I must say that dismantling was rather easy.
The unit was serviced just before I bought it. The guy who sold it to me paid $130 to a technician who only sprayed four tone control pots and that was it!!! $130 for five minute work. I talked to him over the phone and he agreed to find replacement pots so I sent hem to the previous owner. I got them back recently because the technicia did not find any replacements. The previous owner agreed to refund me half of the price I paid for the unit plus the service manual, which is fair.
I put all the pots into kerosine first for a couple of days then into alcohol. Three of these are still soaking up. I hope most pots can be rejuvenated for some time. One is not smooth when turned and I'm afraid it will stay noisy. Once pots are out of alcohol and dry I use deoxidant and afterwards cleaner-lubricant. But these are not long life pots and after 20 years they are approaching their retirement in some junk yard I'm afraid.
The volume-loudness must be a six unit pot with this circuit because loudness is sort of active. My main tone pots are 200k centre detent S curve with a centre tap (fourth track/pin) taken to the ground. Turnover frequency pots are ordinary 30k log or anti-log pots.
I did not take the transformer out as it works fine. But I suspected that it is a dual ordinary unit judging by the shape of its screen and you just confirmed that. The screen looks solid and there is almost no hum when phono is on so I do not bother.
I got the preamp as a temporary solution. I needed one with tone controls and that variavble loudness tempted me. I have a line preamp I built 20 years ago and another one built a few years ago from a kit with dying pots. I plan to build a new preamp later next year to fit in a case I got a few years ago. The only limitation is that it has to fit the design of switches and pot spaces on the face plate and height of the case which is about 42mm inside. Very thin. Yamahas are monsters in comparison.
I'll test all the pots for noise without soldering them back. I simply use them as volume between my tuner and a power amp. Bass control worked fine although noisily. It was only treble pot and loudness.
I suspect caps as they may be shortnning paths. Board defects are difficult to spot but boards look fine to me and soldering as well. I may resolder a number of crucial joints.
Anyway, I decided to replace all caps in tone, loudness, gain, headphone and MM preamp circuits. I also intend to replace most original op-amps with op275, opa2134 and opa2132 mounted on brown dog adaptors. The originals are very slow obsolete beasts. I have more than a dozen of the above op-amps so I'll use them and see what happens.
I have decided to replace rectifying diodes with byw100-200 as these are fast soft recovery ones and I am almost doubling filtering capacitance value. BYWs are cheap and good. Should do the job better.
I must say I do not know why Yamaha called the series natural sound as design and choice of parts are compromised everywhere. The design is riddled with components including heaps of electros and op-amps and transistors and other rather cheap parts, while I think a better job could be done with half of the componets but top ones with very few electros and a simpler design. It could sound more natural then.
I haven't bought any new parts yet. The height of these KG-8200uF/50V Nichicons worries me a little. But they are quite fast.
Where did you get your Audio nippons? I'd like to have smaller than 45mm caps but of higher velue and not less than 50 volts. I looked at mouser for suitable caps but it's difficult to find one good enough fitting dimensions.
If you dismantled the transformer it might be better to fit two 30VA toroids (or even 50VA if they would fit) into the case. They will be quiet and will run cooler and they are cheap.
Alternatively, put transformers into a separate case. That is what I am doing in most of my designs. The phono amps will be quieter and no problem with heating. You might use well oversized transformers say 80VA ones.
cheers,
Hi Chris,
I have dismantled the whole preamp and removed all pots except for tone-loudness control as these are quiet in my c65. I must say that dismantling was rather easy.
The unit was serviced just before I bought it. The guy who sold it to me paid $130 to a technician who only sprayed four tone control pots and that was it!!! $130 for five minute work. I talked to him over the phone and he agreed to find replacement pots so I sent hem to the previous owner. I got them back recently because the technicia did not find any replacements. The previous owner agreed to refund me half of the price I paid for the unit plus the service manual, which is fair.
I put all the pots into kerosine first for a couple of days then into alcohol. Three of these are still soaking up. I hope most pots can be rejuvenated for some time. One is not smooth when turned and I'm afraid it will stay noisy. Once pots are out of alcohol and dry I use deoxidant and afterwards cleaner-lubricant. But these are not long life pots and after 20 years they are approaching their retirement in some junk yard I'm afraid.
The volume-loudness must be a six unit pot with this circuit because loudness is sort of active. My main tone pots are 200k centre detent S curve with a centre tap (fourth track/pin) taken to the ground. Turnover frequency pots are ordinary 30k log or anti-log pots.
I did not take the transformer out as it works fine. But I suspected that it is a dual ordinary unit judging by the shape of its screen and you just confirmed that. The screen looks solid and there is almost no hum when phono is on so I do not bother.
I got the preamp as a temporary solution. I needed one with tone controls and that variavble loudness tempted me. I have a line preamp I built 20 years ago and another one built a few years ago from a kit with dying pots. I plan to build a new preamp later next year to fit in a case I got a few years ago. The only limitation is that it has to fit the design of switches and pot spaces on the face plate and height of the case which is about 42mm inside. Very thin. Yamahas are monsters in comparison.
I'll test all the pots for noise without soldering them back. I simply use them as volume between my tuner and a power amp. Bass control worked fine although noisily. It was only treble pot and loudness.
I suspect caps as they may be shortnning paths. Board defects are difficult to spot but boards look fine to me and soldering as well. I may resolder a number of crucial joints.
Anyway, I decided to replace all caps in tone, loudness, gain, headphone and MM preamp circuits. I also intend to replace most original op-amps with op275, opa2134 and opa2132 mounted on brown dog adaptors. The originals are very slow obsolete beasts. I have more than a dozen of the above op-amps so I'll use them and see what happens.
I have decided to replace rectifying diodes with byw100-200 as these are fast soft recovery ones and I am almost doubling filtering capacitance value. BYWs are cheap and good. Should do the job better.
I must say I do not know why Yamaha called the series natural sound as design and choice of parts are compromised everywhere. The design is riddled with components including heaps of electros and op-amps and transistors and other rather cheap parts, while I think a better job could be done with half of the componets but top ones with very few electros and a simpler design. It could sound more natural then.
I haven't bought any new parts yet. The height of these KG-8200uF/50V Nichicons worries me a little. But they are quite fast.
Where did you get your Audio nippons? I'd like to have smaller than 45mm caps but of higher velue and not less than 50 volts. I looked at mouser for suitable caps but it's difficult to find one good enough fitting dimensions.
If you dismantled the transformer it might be better to fit two 30VA toroids (or even 50VA if they would fit) into the case. They will be quiet and will run cooler and they are cheap.
Alternatively, put transformers into a separate case. That is what I am doing in most of my designs. The phono amps will be quieter and no problem with heating. You might use well oversized transformers say 80VA ones.
cheers,
WOW Yamaha C-65
janusz,
That is the reply of the century.
Soaking the pots in kerosene is new to me. . .how did you
come to the conclusion to use that first, then alcohol, then
deoxidant, then cleaner-lubricant?
As far as a deoxidant goes. . .what do you use? (Noise in the
main volume at 1 o'clock will need work some day).
Yet another horror story with "Technicians!" Sorry about it,
but raise your voice and you pocketed 50% of the purchase
price -- and the service manual to boot. . .$25 at Yamaha parts!
My tone controls have the second part for bandwidth (70K ohm).
Then the 200K ohm is the level control. Thanks for making that
clear.
I think you are right about taking the transformer out of the box
and replacing it with a toroidal transformer. That would remove
half of the heat source in the box. . .the toroidal transformer
would run cooler too. Another good one.
The Audio nippons were put in by the tech that repaired it the first
time. He is long gone. . .but he was good. He must have had a
good supplier (probably Yamaha Parts replacement). They look
almost the same. . .it would be nice to get a hold of a 50V version.
I measured 47mm from PCB to the Top Plate. . .Worst case. . .you
have a metal shop cut four perfect holes where the tops of the
caps stick out. . .might look like a tube preamp. . .conversation
starter! This is a mod after all. . .like I said. . .it runs too hot to
put any components on top. . .a pain for placement of my
electronic crossover. . .but life is a compromise.
Just re-read the Percy site. . .not many choices in +50V. . .most are
50mm high. . .max that will fit is 35mm diameter. Not too many
choices. . . but size is a factor when dealing with the extra voltage.
Yamaha built it so tightly when considering the second of the two
power supplies. The first one is just under 40VAC CT. . . finally
rectified and filtered to +/- 15.5VDC on the secondary 1000 µF
25V caps. the 4700 µF 35V sees close to 30V.
BUT
The second supply gets 51.3VAC CT before the rectifiers. . .
Then with losses each 4700 µF cap will see about 34VDC. . . .very
close to max rated voltage. . . once regulated, the 1000 µF 25V
see close to 19 VDC. . .So, one set of caps it close to max!
It seems that this one should be 50V at least. The second power
supply uses a 2.2 ohm drop resistor to the B949/D1275 transistors.
The first preamp has a seconded set of rectifiers that seems to
go to the volume control/headphone area and is lacking any
significant caps. . . need to measure this. . .seems like it would
have a bunch of ripple. Both supplies have about 0.003VAC
or 0.0085 Vpeak-to-peak. That seems to be done right.
I might use the voltage selector switch to turn on/off the fan
instead. Or use it to select high/low fan speed. Mount the fan
it the top in front of the Class A B949/D1275. I thought these
were part of the amp stage, but maybe they are just regulating.
I guess I leave that question to you tonight. . .9:54 PM Thursday.
Good Night.
Chris Browne
Northern California
janusz,
That is the reply of the century.
Soaking the pots in kerosene is new to me. . .how did you
come to the conclusion to use that first, then alcohol, then
deoxidant, then cleaner-lubricant?
As far as a deoxidant goes. . .what do you use? (Noise in the
main volume at 1 o'clock will need work some day).
Yet another horror story with "Technicians!" Sorry about it,
but raise your voice and you pocketed 50% of the purchase
price -- and the service manual to boot. . .$25 at Yamaha parts!
My tone controls have the second part for bandwidth (70K ohm).
Then the 200K ohm is the level control. Thanks for making that
clear.
I think you are right about taking the transformer out of the box
and replacing it with a toroidal transformer. That would remove
half of the heat source in the box. . .the toroidal transformer
would run cooler too. Another good one.
The Audio nippons were put in by the tech that repaired it the first
time. He is long gone. . .but he was good. He must have had a
good supplier (probably Yamaha Parts replacement). They look
almost the same. . .it would be nice to get a hold of a 50V version.
I measured 47mm from PCB to the Top Plate. . .Worst case. . .you
have a metal shop cut four perfect holes where the tops of the
caps stick out. . .might look like a tube preamp. . .conversation
starter! This is a mod after all. . .like I said. . .it runs too hot to
put any components on top. . .a pain for placement of my
electronic crossover. . .but life is a compromise.
Just re-read the Percy site. . .not many choices in +50V. . .most are
50mm high. . .max that will fit is 35mm diameter. Not too many
choices. . . but size is a factor when dealing with the extra voltage.
Yamaha built it so tightly when considering the second of the two
power supplies. The first one is just under 40VAC CT. . . finally
rectified and filtered to +/- 15.5VDC on the secondary 1000 µF
25V caps. the 4700 µF 35V sees close to 30V.
BUT
The second supply gets 51.3VAC CT before the rectifiers. . .
Then with losses each 4700 µF cap will see about 34VDC. . . .very
close to max rated voltage. . . once regulated, the 1000 µF 25V
see close to 19 VDC. . .So, one set of caps it close to max!
It seems that this one should be 50V at least. The second power
supply uses a 2.2 ohm drop resistor to the B949/D1275 transistors.
The first preamp has a seconded set of rectifiers that seems to
go to the volume control/headphone area and is lacking any
significant caps. . . need to measure this. . .seems like it would
have a bunch of ripple. Both supplies have about 0.003VAC
or 0.0085 Vpeak-to-peak. That seems to be done right.
I might use the voltage selector switch to turn on/off the fan
instead. Or use it to select high/low fan speed. Mount the fan
it the top in front of the Class A B949/D1275. I thought these
were part of the amp stage, but maybe they are just regulating.
I guess I leave that question to you tonight. . .9:54 PM Thursday.
Good Night.
Chris Browne
Northern California
Yamaha C-85 Fan and Power Supply
After a night of thinking and letting the amp sit while ON. . .
I will move the transformer out of the main box. The space
left will have the fan (and use the existing holes for the vent.
The transformer heats up the supply caps closest to the transformer.
The supply caps on the other side heat up since they are near
voltage capacity. . . they will get changed to +50V versions,
while the pair near the transformer can stay 35V.
Another hot spot in the preamp is the volume control board. . .
it throws a fair amout of heat! Maybe an easy fix of replacemet
caps there. . .heat kills caps (electrolytic).
I figure I'll need a molex connector with 10 connections (at least).
Maybe a twelve and double up on the 120VAC connections.
Three connections for the +/-50 CT (two hot, one neutral CT)
Three connections for the +/-40 CT (two hot, one neutral CT)
One connection 120VAC mains neutral
Two connections 120VAC mains hot.
The H1 needs to deliver voltage to the unswitched outlet
and power switch. The H2 delivers voltage to the switched
outlets and back to the transformer.
I really only need a 9 Molex, but 12 again will allow me to double
up the 120VAC mains!
I need to find a 12 conductor cable with the voltage and current
capacity.
I noticed that most of the green caps have the word MUSE on them.
These seem to be the audio grade caps. . .would you really notice
a difference with something off the shelf. . .I might try it.
Also. . .is there a way to test whether a cap is good or bad. . .
in the circuit or do you need to take it out. . .if it were out. . .you
could charge it up to some value below full voltage and then
let it sit for a few days to see if it discharges. Not sure if that is a
good test. . .maybe a resistor and plot the discharge. . .should be
a nice curve!
Have a great day.
Chris Browne
After a night of thinking and letting the amp sit while ON. . .
I will move the transformer out of the main box. The space
left will have the fan (and use the existing holes for the vent.
The transformer heats up the supply caps closest to the transformer.
The supply caps on the other side heat up since they are near
voltage capacity. . . they will get changed to +50V versions,
while the pair near the transformer can stay 35V.
Another hot spot in the preamp is the volume control board. . .
it throws a fair amout of heat! Maybe an easy fix of replacemet
caps there. . .heat kills caps (electrolytic).
I figure I'll need a molex connector with 10 connections (at least).
Maybe a twelve and double up on the 120VAC connections.
Three connections for the +/-50 CT (two hot, one neutral CT)
Three connections for the +/-40 CT (two hot, one neutral CT)
One connection 120VAC mains neutral
Two connections 120VAC mains hot.
The H1 needs to deliver voltage to the unswitched outlet
and power switch. The H2 delivers voltage to the switched
outlets and back to the transformer.
I really only need a 9 Molex, but 12 again will allow me to double
up the 120VAC mains!
I need to find a 12 conductor cable with the voltage and current
capacity.
I noticed that most of the green caps have the word MUSE on them.
These seem to be the audio grade caps. . .would you really notice
a difference with something off the shelf. . .I might try it.
Also. . .is there a way to test whether a cap is good or bad. . .
in the circuit or do you need to take it out. . .if it were out. . .you
could charge it up to some value below full voltage and then
let it sit for a few days to see if it discharges. Not sure if that is a
good test. . .maybe a resistor and plot the discharge. . .should be
a nice curve!
Have a great day.
Chris Browne
Transformer Heat sink on Yamaha C-85
I would like to heatsink the transformer. . . maybe even with a
CPU fan and heatsink. Maybe a heatsink on five of the sides. . . might
look funky. . .but extend the life of it.
Looked into toloroid xformers. . $$$. . .not sure of the advantage!
Chris Browne
I would like to heatsink the transformer. . . maybe even with a
CPU fan and heatsink. Maybe a heatsink on five of the sides. . . might
look funky. . .but extend the life of it.
Looked into toloroid xformers. . $$$. . .not sure of the advantage!
Chris Browne
I bought a Yamaha CDX-930 off of ebay for around 35-40 USD shipping included . It had a burnt-up power transformer- I buy broken stuff and repair/refurbish so I knew it was bad! I got a brand new genuine Yamaha oem replacement transformer from partsource for 35USD. CD player plays like brand new. Yes parts from Yamaha direct are pricey last purchase was 3 each NS-1000 beryllium tweeters I was quoted over yhe phone at 148 USD each. But when it came time to give them my creditcard # I ONLY paid 110 USD each but these were brand new. I am not to crazy about forking over big dollars for Used/abused/stressed or fatigued highend tweeters such as these.Anyway sometimes its your only option. I'm a Yamaha buff I have in my collection/system a C-2,C-4,C-6,M-4,two M-45's,T-1, CDX-500u,CDX-930u,Nakamichi 480,CR-2a,OMS-4,OMS-7,A pair of NS-1000's,A pair of NS-1000M's And a pair of NS 690's, P750 and a YP-701 TT(yeah I still listen to vinyl) Presently I have two DIY ESP P101 2-channel power amps hooked-up to the 2 sets of NS-1000's they sound fantastic.
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