Yamaha CA-1000 repair. My first Yammy!

HELP MY SANITY

I've been chasing my tail on this since 6am (2:30pm now) so I decided to go do a post and get some perspective. The problem is my speaker relay is no longer energizing on this CA-1000. Basically I need to understand how TR709 is biased...read on. :)

The base of TR709 is 0V, and it should be about 0.6V to allow current to flow on TR708 which energizes the relay. (Voltage around TR708 are a bit high (18V), but I think the will pull down when this is fixed, and collector on TR709 is high (18V) but this is just because of TR709 not being switched on allowing current to flow and voltage to drop through the 10k resistor, if I'm not mistaken).

How does the 0.6V on TR709 get setup? Looking at the board I've circled where the AC is applied from a secondary on the transformer (one side is via pilot lamp and tied to ground). We see D707 and a fitler cap and I have 18Vdc at that point. Following through to top of D709 I have 15Vdc (0.7Vac). From their to the base (TR709) I can't follow how we get 0.6V. (The AC ripple in insufficiently small for rectification resulting in 0.6Vdc based via such large resistors (and the diode faces so as to entirely block the DC). I'm sure I'm looking at this the wrong way around... thoughts please... going for a jog now to clear my mind (I'm sure I'm just being silly and frustrated).

I've checked conditions on TR705 - 707 to make sure they aren't activating and pulling down the TR709 base to ground (which is their function if DC is on output, if I'm not mistaken). I've even removed them and I still have 0V present at the base of TR709.

RpG6OFh.jpg
 
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Check/replace C715, check the feed into R721 from D704 on the
relay board, is the zener ok? Probably replace the cap, it performs
the power ON muting, maybe not charging up.

upload_2018-9-9_8-0-53.png
 
I missed the obvious.
I assume you have measured the Vdc to GND at each OUT pin on the power amp boards.
Ideally less than 10mV. More than 600mV (or so) will trip protection.
 
MBZ, yes, first thing I did was check it isn't tripping due proper reasons. Also, I already checked the time delay cap and nearby diode already.

But mate, you've pointed me in the right direction. For some reason I had in my head that the R721 to the "*" symbol was to a ground and some type of bleed cap for power off.... now the circuit makes sense. thanks mate. How blind of me!

Now I see that someone has replaced the fuse resistor F704 (you know the style, two resistors twisted together and old resistors legs clipped above the board and new resistor just attached by touching legs side-by-side and a dab of solder). And, one leg is unstuck, probably when I lifted up the board for inspection this morning at 6am. And F701 is open too, I expect after F704 lifted.

I should have seen this, because it's kind of obvious now that "+50V" is 0V. Ok, I should have this sorted soon then. Will let you know.

Thanks, sometimes a different perspective really helps. And my sanity has now returned.

* is it standard practice to replace fuse resistors with same wattage metal film resistors in the Yamahas? (my experience is with Sansui, where fuse resistors were problematic and they are replaced as standard practice).
 
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Hi Smurfer,

at first impressions I would check C715 for being short too. Same as mbz. Where does the connection circled green go to? (No.3) Also check to see if R721 has gone High/Open.

GPS16
 
GPS16 said:
Hi Smurfer,

at first impressions I would check C715 for being short too. Same as mbz. Where does the connection circled green go to? (No.3) Also check to see if R721 has gone High/Open.

GPS16
Click to expand...

GPS, looks like our replies passed each other in the internet :). C715 is good. Green circle goes to pilot lamps and other end of transformer secondary (and referenced to ground on that end). Check out my reply above and see how silly I was with the R721 thing. Anyway looks like we have found some previous repairs that have fallen apart... will report back when i patch her up.
 
Apologies, a little off post.
Not sure if you've done a recap but... I'm tinkering with a CA-1000 that was refurb'd in Japan.
I've refurb'd 5 or 6 or ... CA-800/-1000's with Elna Silmic/Nichi KL,PW,ES,PA/UCC-SMH or KMH
being the caps used. The unit from Japan mainly used Nichi KZ, with MKP an Polyprop caps used
on the tone board, see pix, I've since replaced the 2 silver (Jorvial?) caps. The filter board was
untouched. Point is the Japan unit sounded significantly better. I'm currently dissecting the amp
to work out why. Also 2SC1345 were not replaced.
Function.JPG
 
mbz said:
Apologies, a little off post.
Not sure if you've done a recap but... I'm tinkering with a CA-1000 that was refurb'd in Japan.
I've refurb'd 5 or 6 or ... CA-800/-1000's with Elna Silmic/Nichi KL,PW,ES,PA/UCC-SMH or KMH
being the caps used. The unit from Japan mainly used Nichi KZ, with MKP an Polyprop caps used
on the tone board, see pix, I've since replaced the 2 silver (Jorvial?) caps. The filter board was
untouched. Point is the Japan unit sounded significantly better. I'm currently dissecting the amp
to work out why. Also 2SC1345 were not replaced.
View attachment 1276993
Click to expand...

Definitely of interest. I am just using it stock for a while, which is what I like to do with 'keepers', and then do the recap later.

Let us know what you find out. Are power supply caps new on all? Once I get this sorted, and put the new speaker relay in, I will start planning on the recap. Will measure the two 18,000 uF caps at 120Hz tomorrow and see what shape they are in as a starter, but would love to know what you find out about the finer details. :thumbsup:
 
smurfer77 said:
Are power supply caps new on all?
Click to expand...
Yeah, happy to continue to use Nichi PW and EP on the relay board.
The Japan unit had Panasonic TUP 18000uf/63V, (tested ok at 17000uf), the bass was good but became "loose"
when pushed very low (Zoe Keating cello). I've only now just replaced them with UCC-SMH 22000uf/80V. Bass
not soo loose on the same passages, will give it some time to settle. Main focus will be on the tone board where
the guy used a 4.7uf/50V Jorvial (silver) at C317, 318. A 3.3uf/35V is normally used in this position, I used a
Silmic II, will probably source some KZ's and also try a 4.7uf. Maybe too early to say but might have lost a little
bit of "air"/separation by going to 3.3uf.

EDIT: Checked an untouced/original unit, it has a 4.7uf tant at C317,8. Maybe a late
production change. Will revert to 4.7uf and reassess.
 
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What I'm finding is that when I use a standard component tester I tend to get good C for reservoir caps, but standard component testers use fairly high frequency, usually 1kHz or 10Khz. But when I measure at 120Hz the story is often different (and worse); and this is the frequency those caps will see. So now I'm reevalutating all of my amps that have original PS caps (not many haven't been recapped truth be told, but still interesting...). So I wouldn't rule out PS caps being low capacitance, for the bass effect you mention, unless you are sure of testing frequency. And if ESR has drifted a bit high, there may be some bass 'oomph' lost in power supply voltage supply sag too. You know all this probably.... food for thought.

I haven't thought too hard about the recap, but aside from the usual electrolytic campaign I am thinking the best rewards will come from changing the following coupling caps to film caps (unless they are film already... just looking at schematic now which doesn't differentiate), and slightly larger value where they will fit:

TONE:
C301/302
C317-320

FILTER:
C540/541
C511/512
C531/532

MAIN:
C801/C801 (<-- not a typo, they used same numbers for both channels only on this board)

Not really fussy about brands (usually use WIMA, but open to suggestions); polypro where it will fit and polysester otherwise.
 
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C301,2 are polar tantalums, previously I would use Nichicon UKL, tempted to go MKS. "Hiroshi"(japanese unit) used Nichicon FW (wtf??? and this unit sounds so good...)
Likewise C317,,320, 540,541, 511,512, 531, 532 are polar tants. Symbol on the schematic is a circle with a cross inside as per below. Copy resolution converts it
to a solid dot.
upload_2018-9-9_19-42-39.png
 
mbz said:
C301,2 are polar tantalums, previously I would use Nichicon UKL, tempted to go MKS. "Hiroshi"(japanese unit) used Nichicon FW (wtf??? and this unit sounds so good...)
Likewise C317,,320, 540,541, 511,512, 531, 532 are polar tants. Symbol on the schematic is a circle with a cross inside as per below. Copy resolution converts it
to a solid dot.
View attachment 1277134
Click to expand...

Got ya on the tants. Well i think MKS would be an upgrade over UKL for sure, or FW (i do like FW and FG but i think MUSE would be more interesting to try if going electrolytic).
 
Well, sorted out the previous issues last night very quickly... a little too quickly.

Note to self... don't work on amps sleep deprived.

My solder wire was left on the bench and it shorted out the left main amp board.... magic smoke released. Hopefully the fuses blew quick enough to protect much of the board, but at this stage I think I'm going to just put this amp aside now for full rebuild. Will pull the main amp boards and go through the bad board in my spare time, while waiting for pulling together cap list and postage time.

I guess the upside is that this amp deserves a full rebuild and now it is going to get it.

I measured the main reservoir caps this morning. The 18,000uF caps measured ok for C and a little lossy at high frequency using a standard component tester. But at 120Hz they measured only 11,000uF with an impedance phase angle of -6.8 degress (should be more towards -90 (for new big caps I usually measure about -85 degrees or higher). I.e. they have bucket loads of resistance relative to capacitive reactance, will drop voltage and cause sag, and will warm up more and more accelerating lifetime reduction. IN THE BIN THEY GO. No wonder i couldn't make full rated output. Sorry to moan on about the 120Hz, but it's a game changer for me... it use to drive me crazy that caps measure ok with a component tester and still supply sags.
 
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No mean to hi jack this thread but I hope I will contribute in some ways. My CA-1000 is currently under full restoration and my tech is looking for a replacement for the two big 18000uf/63V filter caps. What is the general consensus for a replacement for these? Is there a drop it unit that could work? He says they are 51 mm in diameter.
 
avionic said:
Whats the maximum length that will still allow you to slide the wooden bonnet over the amplifier?
Click to expand...

I believe no more than a few mm from the original ones. I was there when he openned the wooden case and it was quite tight. I don't know the actual height of the originals.
 
Either way. They are both" 5-pin snap-in "and will require some minor PCB alterations.
 
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