My Yamaha CA-1000 Restoration / Modifications Thread

[mbz]

measure voltage between TP3 and TP4, max 47mV.

 

[T3SAM]

Thank you All for your input. I was able to adjust the TP3-4 for Normal Class AB 47mV and Class A 94mV for both ch. Tested the amp works fine BUT still one problem is the L ch (which was R ch before amp board swapping) gets hot even in Class AB whereas the other Ch (currently R) not hot just tiny warm.
In the currently L ch the Tr 609 (2SC680) gets very hot.

 

[mbz]

Set operations to Normal. Measure voltage at left power amp wires A,B,C,S +/-50, +/-B, D607 anode

 

[T3SAM]

	L Ch	R Ch
A	-0.65	-0.36
B	2.17	1.86
C	2.17	1.86
S	4.44	4.43
-50	-50.50	-50.56
50	50.23	50.46
-B	-49.01	-49.26
+B	48.99	49.21
D607 anode	1.50	1.18
D607 cathode	0.83	0.52
D605 anode	0.192	0.000
D605 cathode	-0.013	-0.013

 

[T3SAM]

	L Ch	R Ch
A	-0.65	-0.36
B	2.17	1.86
C	2.17	1.86
S	4.44	4.43
-50	-50.50	-50.56
50	50.23	50.46
-B	-49.01	-49.26
+B	48.99	49.21
D607 anode	0.192	0.000
D607 cathode	-0.013	-0.013

 

[mbz]

Voltages don't look too bad, certainly wire C is a little high.
Did you change TR606(2SC458LG) mounted on the heatsink. Most use KSC1815 as a replacement, round face to heatsink, will study voltages.

edit odd that the S point voltages are the same, but then B,C are significantly different.
Inspect R615(470) try measuring in circuit.
With the amp powered off/unplugged measure the resistance between the C & S wires on the faulty left channel, operations switch set to normal, expect open/OL

 

[T3SAM]

Thanks lot mbz.
R613/614/615/616 are the very much same for both ch. in circuit R615 467 for L and 478 for R
resistance between the C & S wires 467 for L and 469 for R ch
thanks

 

[mbz]

measure the resistance between the C & S wires on the faulty left channel, operations switch set to normal, expect open/OL

resistance between the C & S wires 467 for L and 469 for R ch

Apologies, I had a "blonde moment"
Can't see the forest for the trees...

Did you change TR606(2SC458LG) mounted on the heatsink. Most use KSC1815 as a replacement, round face to heatsink,

Was it replaced? Need round face to heat sink

 

[T3SAM]

Tr 606: No it’s still original, not changed yet. O

 

[mbz]

Can you post a hi-res pix of faulty left channel board both component side and solder side

D605 cathode should be connected to GND, looks like you have a minor GND problem, not the cause of this problem. With amp powered off connect black MM probe to black/GND wires/pins on the electrolytic board then with red probe measure the resistance at,
- any black speaker post
- phono chassis GND lug
- at each black GND wire ("e" and "E") on the power amp board
- AUX RCA outer/GND
- black GND wire in yellow wrap on volume board
All should be less than 1ohm (abouts)

Back to the problem...
TR606 Vce is about 2.17(C wire) - -0.65(A-wire) + (0.65) TR606Vbe = 3.47V

for the working side
TR606 Vce is about 1.86(C wire) - -0.36(A-wire) + (0.65) TR606Vbe = 2.87V
TR606 is working a little harder but significant???

Still puzzled by Same wire S voltages but difference at wire C

Anyone with ideas???

 

[T3SAM]

Thanks mbz again. Really appreciate.
I have measured all the res between all these you mentioned above. I put MM black in a black wire pin on the elec cap board then measured all the res. They are all pretty much 1.2-1.6 ohm. Aux1/2 is 1.6 ohm all other about 1.2 ohm.

 

[mbz]

OK, the GND issue is a minor distraction.

Need to refocus on why TR609 is overly warm

 

[mbz]

Can you post a hi-res pix of faulty left channel board both component side and solder side