Yamaha CX-830 help

[MWH901]

Hi, all... unit will not power up at all. IC1 (an NJM2041DD op amp for the CD input) was blown apart. I removed it from the board for starters, have not replaced it. Also R295 and R296 (per the schematic, 1-ohm flameproof resistors) looked a little crispy and measured ~5 ohms. I changed them for fresh 1-ohm resistors.

Checking voltages, starting with the transformer secondaries:
Orange 1: .153 V
Orange 2: .153 V
Red 1: 0V
Black: 0V
Red 2: 0V

Should I be getting something on these? In other words, is the transformer shot, or is this like one of those funky Yamaha 'X' power supplies where something upstream shuts down the transformer output if it's out of spec?

Thanks!!

 

[avionic]

Yamaha 'X' power supplies

No.. Not even close..!!!


These are the only Yamaha X-power supply models
Yamaha amplifiers which were manufactured 1980 - 1982.

Models A-760, A-760II, A-960, A-960II, A-1060, M-50, M-70 and B-6

 

[avionic]

Orange 1: .153 V
Orange 2: .153 V
Red 1: 0V
Black: 0V
Red 2: 0V

Measuring AC or DC ? Should be measuring AC !

 

[avionic]

Black will be zero volts. ( center tap )

 

[MWH901]

Measuring AC or DC ? Should be measuring AC !

Yes, these are AC.

The low voltages I stated before were orange-black.

If I measure orange-orange, it's 0V, red-red is also 0V.

 

[MWH901]

This was the op-amp carnage. I know it's not super common to fry a transformer, but I'm wondering if in this case, whatever happened was enough to take it out.

 

[avionic]

Are you getting AC to the transformers primary ? Does this piece have a voltage selector on the rear panel ?

 

[MWH901]

Are you getting AC to the transformers primary ?

Yes, 120 V at the gray/brown primary wires.

 

[avionic]

That opamp is pretty bizarre..

 

[avionic]

Yes, 120 V at the gray/brown primary wires.

Start shopping for a transformer...

 

[MWH901]

Start shopping for a transformer...

That's what I was afraid of.

I appreciate your help, as always!

 

[avionic]

Did you try to ohm out the primary ? Check the resistance across the power plug with the on/off switch in the on position.

 

[avionic]

This may have taken a lightning strike..

 

[MWH901]

Did you try to ohm out the primary ? Check the resistance across the power plug with the on/off switch in the on position.

It shows OL. This unit doesn't have a "traditional" power switch, since it has a standby mode.

I was thinking the same thing re: lightning strike / power surge.

 

[avionic]

It shows OL.

Yep transformer is toast. Do you have any idea what the secondary voltages are suppose to be . Schematic I have is no help.

 

[MWH901]

No idea... the schematic I'm looking at only shows post-rectification voltages.

 

[avionic]

No idea... the schematic I'm looking at only shows post-rectification voltages.

Same one I have. Actually post voltage regulation.

 

[MWH901]

Well... you win some, you lose some.

 

[avionic]

CX-800 transformer would probably work ..
red -- 23.5 vac
blk --- 0
red -- 23.5 vac
orange to orange 13.9 vac

 

[Nashou66]

search this on ebay "Yamaha Power Transformer 29WP300 28v+28v (R-Br-R),17v+17v (Or-Bl-Or),18v(Y) ,W28" would that fit the bill or close to it? 28 VAC might be a bit high but might work?

CX-800 transformer would probably work ..
red -- 23.5 vac
blk --- 0
red -- 23.5 vac
orange to orange 18vac