Restoration Help Yamaha CR-820

[sajjad amer]

Thank you , I finish my shift at 2330 GMT, will check and report back.

 

[sajjad amer]

I'm struggling to find the resistor. Looking at schematic it's next to TR 803
But those are not 47 K
I've measured across the ones near arrow and voltages are
23.4-42.3 --- one next to cap
23.4-16.3--- one next to relay

 

[sajjad amer]

2 out of the three resistors between the TR713 and TR 721 were open so please bear this in mind when interpreting the voltages.
Also which components would have blown with these resistors?

 

[avionic]

But those are not 47 K

Yes they are .. yellow / violet / orange / gold 47KΩ 5% carbon film.

 

[sajjad amer]

Have I measured across the correct resistors?
Please see my pictures
Thank you

 

[avionic]

23.4-42.3 --- one next to cap
23.4-16.3--- one next to relay

What ? How are you measuring this ? Black test lead clipped to chassis ground and probing with red test probe ?

 

[avionic]

Black test lead clipped to chassis ground and probing with red test probe

 

[sajjad amer]

Yes precisely, black lead pink chassis positive across the resistor ends one by one

 

[sajjad amer]

Pink is typo

 

[avionic]

I hear FM radio for a sec and then relay clicks and silence !!!

Should be the other way around for the correct operation of the relay..

 

[sajjad amer]

I agree with you, I will make a video and post it.

 

[avionic]

2 out of the three resistors between the TR713 and TR 721 were open

Identify resistors with Rxxx reference designator. Were these checked in circuit ?

 

[avionic]

23.4-42.3 --- one next to cap
23.4-16.3--- one next to relay

Well that explains why the relay "resets". You have pretty substantial voltage at the amplifiers output. On both amplifiers.

 

[avionic]

Is there a slight delay after you press the power button before the relay "sets". Or does the relay click the instance you press the power switch ? Then appear to "reset" or click again.?

 

[sajjad amer]

Identify resistors with Rxxx reference designator. Were these checked in circuit ?

these resistors were initially tested in circuit with power off then out of circuit, they are both 22k resistors (red-red-orange-gold)

 

[sajjad amer]

Is there a slight delay after you press the power button before the relay "sets". Or does the relay click the instance you press the power switch ? Then appear to "reset" or click again.?

9 out of ten times relay just wont click. when it does there is sound for less than a sec then it clicks again and no sound.

 

[sajjad amer]

Replacing those 22k resistors with new ones had done the trick. Thank you ever so much for beating with me and guiding me along.
Now the 4 lights do not work and when I check voltage at L1-L4 there is nothing. Visual inspection of bulbs shows they are also blown, but I was expecting some voltage at above points. I hope I'm on the right path to diagnose it?

 

[sajjad amer]

I spoke too soon, after playing faultlessly for 4 hours, its again back to square 1. Switches on, dials move but relay does not click.

TBH I think it worked by chance and my "diagnosis" of 22k resistors was incorrect.

I was trying to expose the conductors on 3rd light from left , red wire with hot soldering iron when the fuse next to power supply blew.There are 2 fuses next to TR803, fuse near to the 100uf 63v caps in power supply blew.

I have learnt my lesson, never again but now how should I go about repairing it?