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Advice requested on repair Yamaha CA-1000

jansen2810 said:
I already replaced the BP caps with Nichicon ES, because I had them in stock.
Click to expand...

Understandable

The CA-1000 is a very good amp, if you get it working normal/refurbished you will be pleased.

The operations switch performs 2 actions, selects different voltage windings and shorts/joins a number of pins (A&C&S in
class A). Long shot that there is some damage to the operations board, eg solder bridge, the resistance measurements
are for test.

I don't have an issue with you unsoldering the +/-B and +/-50 supplies on one power amp side in an attempt to find
the faulty side. What was strange is that you needed to remove fuses from both sides (shutting down the outputs)
before the relay clicked.
 
mbz said:
Understandable

The CA-1000 is a very good amp, if you get it working normal/refurbished you will be pleased.

The operations switch performs 2 actions, selects different voltage windings and shorts/joins a number of pins (A&C&S in
class A). Long shot that there is some damage to the operations board, eg solder bridge, the resistance measurements
are for test.

I don't have an issue with you unsoldering the +/-B and +/-50 supplies on one power amp side in an attempt to find
the faulty side. What was strange is that you needed to remove fuses from both sides (shutting down the outputs)
before the relay clicked.
Click to expand...

It is strange. Removing fuses of one main amp causes the bulb limiter to shine just less bright, removing the fuses of the other one made the bulb shine less bright also but in an irregular way. (flickering). I will post my measurements. I am 67 but still working. :-)
 
mbz said:
The pic is not one of my amps. Generally I will replace TR705, TR707, TR709 being 2SC458's, I wouldn't use Nichicon ES
(bright green) with Nichicon EP being a better choice. I'd use Nichicom PW for the other caps,
View attachment 1669433

With amp powered off/unplugged, operations switch set to class A, black
meter probe inserted into any black speaker post, measure the resistance
at wire "B" on left power amp. Repeat for wires A, C, S, these 3 should
give the same result. Need to verify no near short, anything less than 500
ohms would be a concern. Repeat for right power amp.

Please try to get all requested measurements, without them we/I loose interest very fast.
Click to expand...

All 6 of them about 10kOhm B a bit higher about 15kOhm
 
mbz said:
Carefully measure dc voltage at one side of F704 (47ohm, as pix), black probe connected to chassis or any black
speaker post. Then measure the other side of F704 to GND. Expect about 65Vdc one side and 60Vdc the other
Click to expand...

Both amps out: 51 vdc 55 vdc
one amp out 38,8 vdc 41,1 vdc
both amps on 28,9 vdc 30,8 vdc
mbz said:
Carefully measure dc voltage at one side of F704 (47ohm, as pix), black probe connected to chassis or any black
speaker post. Then measure the other side of F704 to GND. Expect about 65Vdc one side and 60Vdc the other
Click to expand...
Left or right amp out makes no difference
In normal: 49,6 vdc and 53,3 vdc
 
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Please post a photo of the top edge of your amplifier assembly circuit boards. In particular the A,B,C & S connections.
 
While you have the amplifiers out test the final outputs and drivers. TR609,610,611 and 612. On both amplifiers. Out of circuit.
 
jansen2810 said:
Both amps out: 51 vdc 55 vdc
one amp out 38,8 vdc 41,1 vdc
both amps on 28,9 vdc 30,8 vdc
Click to expand...
Without load from power amp, regulated supply delivers 4/47 = 85mA
Drops to 49mA with one amp and 40mA with both amps connected, voltage progressively worse.
Was thinking about the rectifier but results in normal are ok., back to power amp and class A...

Amp is still on DBT which explains the lower than expected voltages 55 v 65Vdc.
 
Have you done any work on VR604, eg adjusted or replaced?
Suggest check resistance, in-circuit should be ok, amp powered
off/unplugged for all resistance measurements. Measure at wire "A"
and the top of R617 I (in front of bias transistor)
upload_2019-11-12_19-3-16.png


Again, not my work...

EDIT Resistance wire B to GND is about 15k could indicate VR is close to max 5k.
Vaguely recall VR604 being set to about 2.2k-2.4k on units I've worked on.
 
Last edited:
mbz said:
Without load from power amp, regulated supply delivers 4/47 = 85mA
Drops to 49mA with one amp and 40mA with both amps connected, voltage progressively worse.
Was thinking about the rectifier but results in normal are ok., back to power amp and class A...

Amp is still on DBT which explains the lower than expected voltages 55 v 65Vdc.
Click to expand...

What's DBT?
 
mbz said:
Have you done any work on VR604, eg adjusted or replaced?
Suggest check resistance, in-circuit should be ok, amp powered
off/unplugged for all resistance measurements. Measure at wire "A"
and the top of R617 I (in front of bias transistor)
View attachment 1670542


Again, not my work...

EDIT Resistance wire B to GND is about 15k could indicate VR is close to max 5k.
Vaguely recall VR604 being set to about 2.2k-2.4k on units I've worked on.
Click to expand...


Yes I did on one channel, cannot remember which channel, I wanted to meet the requirements in the manual. They were not far off at the time. Cannot remember A or normal. I will post the values as is now in class A. BTW I bought new VR's as in the picture, not replace them yet. Multi-turn ones or how you call them in English.
 
mbz said:
Have you done any work on VR604, eg adjusted or replaced?
Suggest check resistance, in-circuit should be ok, amp powered
off/unplugged for all resistance measurements. Measure at wire "A"
and the top of R617 I (in front of bias transistor)
View attachment 1670542


Again, not my work...

EDIT Resistance wire B to GND is about 15k could indicate VR is close to max 5k.
Vaguely recall VR604 being set to about 2.2k-2.4k on units I've worked on.
Click to expand...

Before adjusting
mbz said:
Have you done any work on VR604, eg adjusted or replaced?
Suggest check resistance, in-circuit should be ok, amp powered
off/unplugged for all resistance measurements. Measure at wire "A"
and the top of R617 I (in front of bias transistor)
View attachment 1670542


Again, not my work...

EDIT Resistance wire B to GND is about 15k could indicate VR is close to max 5k.
Vaguely recall VR604 being set to about 2.2k-2.4k on units I've worked on.
Click to expand...

R = 3,6 kOhm
L= 3,0 kOhm

Before adjustment : R= TP 1/2 15,8 vdc after 14,88 end of VR
L= TP 1/2 16,2 vdc after 15,00 so on the dot.

overview ca1000.png DBT at 75W class A.png Before : TP 3/4 R = 0,67vdc after on the dot, so 0,94vdc L= 0,46 after on the dot. Left is jumping around a bit. Noticeable by flickering of the DTB.

Pictures a bit large, sorry.
 
jansen2810 said:
R = 3,6 kOhm
L= 3,0 kOhm
Click to expand...
VR settings are much higher than I recall, probably because bias is set
on DBT. Suggest set VR604 to zero (avionic post #39) on both channels then
power up and check for relay click etc... Then slowly increase VR604 to
about 600mV again both channels. Do not set to 940mV on DBT.
 
mbz said:
VR settings are much higher than I recall, probably because bias is set
on DBT. Suggest set VR604 to zero (avionic post #39) on both channels then
power up and check for relay click etc... Then slowly increase VR604 to
about 600mV again both channels. Do not set to 940mV on DBT.
Click to expand...

Problem is getting worse, I disconnected the +50/-50 from amps, relay clicks and there are the 50 volts (with and without fuses), with one amp connected it drops to +/-27vdc, with both connected only +/-15vdc. DBT burning like on Christmas. Wait.. it could be because I tuned bias etc.. on specs now. So counterclockwise? It's making me nervous... fiddling with those VR's. But will do as suggested.
 
jansen2810 said:
So counterclockwise?
Click to expand...

Yes.... Just verified on a CA-800/1000 here.
For trouble shooting adjust the bias (idle current) for both Normal and Class A to zero volts. 0.0000001 vdc or as close to zero as possible for both amplifiers. Leave them at zero until you get (normal) mode working. I'm not even interested in class A right now.



sneak preview.......
CA-800 that I just finished up. Pretty much the same as the CA-1000.In fact the amplifier assemblies are from a CA-1000.upload_2019-11-12_16-25-14.png
 
Last edited:
The amplifiers have to properly work in class AB(normal) for Class A to even think about working. This flipping from normal to class A and back.Is getting us nowhere.;)
 
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