Help restoring a Yamaha CA-600

[bzb882]

Great thread, I plan on recapping mine shortly. Looks like there's a typo with respect to C601. Mouser part # is for a 1 uF 50V cap (looks like that's correct), not 220 uF as noted.

 

[EmuMannen]

Great thread, I plan on recapping mine shortly. Looks like there's a typo with respect to C601. Mouser part # is for a 1 uF 50V cap (looks like that's correct), not 220 uF as noted.

You are right, it must be a cut-and-paste typo. I ended up buying everything from Digi-Key, here is the updated BOM (without Mouser No.):

Filter Board
============
C505 & C506 (1µF, 35V, P3, tant); UFG1H010MDM (1µF, 50V, D5, L11, P2)
C509 & C510 (100µF, 6.3V, D8, P4); UFG1E101MPM (100µF, 25V, D8, L11.5, P3.5)
C511 & C512 (1µF, 35V, P3, tant); UFG1H010MDM (1µF, 50V, D5, L11, P2)

Tone Control Board
==================
C302 & C305 (1µF, 35V, P3, tant); UFG1H010MDM (1µF, 50V, D5, L11, P2)
C305 & C306 (100µF, 10V, D8, P4); UFG1E101MPM (100µF, 25V, D8, L11.5, P3.5)
C307 & C308 (10µF, 35V, D6, P4); UFG1H100MDM (10µF, 50V, D5, L11, P2)
C309 & C310 (3.3µF, 35V, P3, tant); UFG1H3R3MDM (3.3µF, 50V, D5, L11, P2)
C311 & C312 (33µF, 10V, P4, tant); UFG1E330MEM (33µF, 25V, D6.3, L11, P2.5)

Function Board
==============
C401 & C402 (10µF, 10V, P3.5, tant); UFG1H100MDM (10µF, 50V, D5, L11, P2)
C411 & C412 (47µF, 35V, D10, P6); UFG1H470MPM (47µF, 50V, D12.5, L11.5, P3.5)
C416 & C417 (4.7µF, 50V, P3, tant); UFG1H4R7MDM (4.7µF, 50V, D5, L11, P2)
C421 & C422 (1µF, 35V, P3, tant); UFG1H010MDM (1µF, 50V, D5, L11, P2)
C425 & C426 (10µF, 10V, P3.5, tant); UFG1H100MDM (10µF, 50V, D5, L11, P2)

Power Board (NA06399)
=====================
C701 (220µF, 25V, D13, P5); UFG1V221MPM (220µF, 35V, D10, L20, P5)
C704 & C705 (100µF, 80V, D16, P7.5); UFG2A101MHM (100µF, 100V, D12.5, L20, P5)
C706 (47µF, 16V, D10, P4); UFG1V470MPM (47µF, 35V, D8, L11.5, P3.5)
C707 (100µF, 50V, D13, P5); UFG1J101MPM (100µF, 63V, D10, L20, P5)
C709 (1µF, 50V, D5, P3.5); UFG1H010MDM (1µF, 50V, D5, L11, P2)
C710 (1µF, 50V, D5, P3.5); UES1H010MDM (1µF, 50V, D5, L11, P2)
C711 (100µF, 6.3V, D10, P4); UES1E101MPM (100µF, 25V, D10, L16, P5)

Electrolytic Capacitor Board
============================
C802 & C803 (4700µF, 50V, D35, L62, P20); MAL205158472E3 (4700µF, 63V, D30, L40, P17.5)

Main Amp Board x 2
==================
Tr607 (C458); KSC1815YTA (50V, 80MHz, 400mW, 150mA, 120hFE)
C601 (1µF, 50V, D5, P4); UFG1H010MDM (1µF, 50V, D5, L11, P2)
C609 (47µF, 50V, D13, P6); UES1H470MPM (47µF, 50V, D10, L20, P5)
C611 (100µF, 50V, D13, P6); UFG1H101MPM (100µF, 50V, D10, L16, P5)
C615 (220µF, 35V, D13, P6); UFG1H221MHM (220µF, 50V, D12.5, L20, P5)

 

[EmuMannen]

Ps. I was initially planning to use a pair of UKW1J472MRD (4700µF, 63V, D22, L50, P10) instead of the two MAL205158472E3 (4700µF, 63V, D30, L40, P17.5) I had to make adapters for. UKW1J472MRD would also need some type of support I guess...

 

[avionic]

So did you get your midpoint squared away ?

 

[EmuMannen]

So did you get your midpoint squared away ?

No still the same problem with the midpoint, will work on it this weekend...

 

[EmuMannen]

Your just spinning your wheels. Until you swap out the two long tailed pair (differential pair) transistors.(TR601/603 and TR602/604)

I have now swapped TR601/603 and TR602/604, the problem did not follow, it persisted on the left side (same midpoint voltage as before on both sides, about 0.5V on left side, 4mV on right side). Any other ideas?

 

[avionic]

Left
D601 13.15 v --- just a wee bit out of tolerance
D603 12.15v --- OK

You can replace it . But I don't think you will gain anything from it.

Re-thinking this.could be and issue. D601..
Check resistance of R607 -- 390 Ω *
Check resistance of R605 -- 150Ω *

* these two are in a series parallel with the adjustment trimmer so to accurately measure there resistance you will need to lift one lead.

 

[EmuMannen]

I got some new measurements. Initially measuring the zener-diodes I measured between E (OUT), when measuring between E (IN) I get 12V and 0V on D601 and D603. Some further measurements against E (IN):

Left side Tr601 base = 0.631V and right side Tr602 base = 0.163V

Left side R611 towards VR601 wiper = 0.41V and right side R611 towards VR601 wiper = -0.055V (that was with left side VR601 in end state, right side VR601 adjusted for midpoint 0V)
Left side R611 towards VR601 wiper = -0.121V and right side R611 towards VR601 wiper = 0.059 (VR601 on both side in approximately same position)

Measuring voltage between E (IN) and E (OUT) on left side ~ 1V
Measuring voltage between E (IN) and E (OUT) on right side = 0V

 

[avionic]

Check resistance of R607 -- 390 Ω *
Check resistance of R605 -- 150Ω *

 

[EmuMannen]

R607 = 389Ω
R605 = 149.9Ω

 

[zaibatsu]

Hmm, could it be possible that the offset is coming from somewhere further upstream?

Could you turn the coupler switch to "off" and re-check? If you haven't already.

 

[EmuMannen]

Hmm, could it be possible that the offset is coming from somewhere further upstream?

Could you turn the coupler switch to "off" and re-check? If you haven't already.

It has been in the "off" position all the time. Could it be further downstream? I will swap position with the main amp boards just to see if the problem follows the whole boards or not...

 

[avionic]

. Could it be further downstream?

If your DC rails are not equal in +/- voltage . It will throw off the offset. But that would do it to both channels.

 

[avionic]

Excessive leakage in the outputs or drivers could skew your offset.

 

[EmuMannen]

I swapped sides of main amp board and the problem did not follow. So I guess the root cause is not on the amp board but somewhere downstream. DC rails seems OK (equal in voltage). Next stop Power Circuit Board I guess...

 

[avionic]

Next stop Power Circuit Board I guess...

If it was the power supply then both channels would be effected.

 

[EmuMannen]

If it was the power supply then both channels would be effected.

Power Circuit Board seems to contain more than power though, phone jack, speaker selector, speaker protection (is that what relay MX2PO does?) etc.

Not the exact same problem but Power Circuit Board apparently could affect one of the main amp boards as in this post: http://audiokarma.org/forums/index....0-hot-amp-board-problem.749335/#post-10276208

 

[avionic]

It will be hard to fit film caps instead of the tantalums. Is it really OK to replace them with electrolytics?

Look at this finding on the Tone Control Board, doesn't look too good:
View attachment 1075680

I assume these ones on the Function Board are 4.7uF but what about the (M) marking? It is also two 50V on that board where the service manual state one 16V and another 35V...
View attachment 1075682

Is it really OK to replace them with electrolytics?

Yes...Definitely.. I do it all the time..

 

[zaibatsu]

Not the exact same problem but Power Circuit Board apparently could affect one of the main amp boards as in this post: http://audiokarma.org/forums/index....0-hot-amp-board-problem.749335/#post-10276208

I feel the same as avionic, however if you want to try changing the equivalent part anyway, TR701 on your amp:
2SC1213 --> KSC2383

 

[EmuMannen]

OK, found the "error"... Feels almost ashamed to tell you... I traced E IN to the back plane thanks to friendly forum users on the Swedish www.faktiskt.io board. This is where it got really weird, my board seemed to have the 9P CIS connector at the wrong place, in the middle instead of to the upper left. And whats even weirder, that connector seemed to go to the TAPE sockets... Wait, two 9P CIS sockets on the same board and one seems to be in the wrong place?!? Or maybe I put the cable to the wrong connector! Swapped connector and now everything worked and I had no problems setting midpoint voltage or bias on both MAIN AMP cards. Thanks everyone who's been chasing ghosts with me, I'm sorry for taking your time...