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YAMAHA CR-620 Protection Relay Fun

Would need to know the measured DC voltages around TR808 and TR809.
Emitter?
Collector?
Base?
 
nodols said:
Tested all voltages in the protect circuit, everything seems to be very close to what the schematic is showing.
Click to expand...
The schematic is showing the circuit " in protection" mode voltages. Look at the relay contacts positioning in the schematic.
 
@avionic

Here is a snapshot of my notes.
Note sure if it's clear.


TR808

B - 0.012v
C - 20.6v
E - 0v

TR809

B - 20.9v
C - -0.02v
E - 20.3v

1738454628877.png

Only taken voltages from the protect circuit, will check the amps, but then again, as protect is engaged. Main amp may have different voltages, maybe?
 
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Check/reflow solder connections on TR808 & TR809. Ideally you need around 12v on the collector of TR809 to energize the relay.
 
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avionic said:
Check/reflow solder connections on TR809. Ideally you need around 24v on the collector of TR809 to energize the relay. But in this case, it will be closer to 20v.
Click to expand...
Reflowed both transistors and the relay, issue is still there.
 
avionic said:
Very carefully measure the DC voltage on the 4 relay contacts. Should be close to zero volts or a few millivolts.
Click to expand...

There are 8 connections as shown.
The first two on the top are -24mv, the 2 below it are 0s the 3rd from below are around 26volts as shown and the two at the bottom are 0volts.
 

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petehall347 said:
has the flyback diode been checked yet ?
Click to expand...
Not really sure if this is the diode. It’s just beside the relay. In circuit, forward and reverse diode test 0.279volts. Out of circuit as I desolder this this morning to test it checks out. Forward bias around 0.5v, reverse is high resistance.
 

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nodols said:
Not really sure if this is the diode. It’s just beside the relay. In circuit, forward and reverse diode test 0.279volts. Out of circuit as I desolder this this morning to test it checks out. Forward bias around 0.5v, reverse is high resistance.
Click to expand...
yes that's it .it appears fine
 
There is something weird about the output transistors. The collector voltages are as per schematic at around 39V and -39volts.
The emitters and bases however are a different story, at startup it starts at around 29v and gradually and steadily drops, tapped both for around a minute or so, voltage gradually drops for both emitter and base, by .5mv per second, after a few minutes the voltage is down to 20ish volts. I haven't waited until where it stops, I'll try again in a bit.
For sure it's not the right voltages as per schematic. Base voltage should be around 0.58v and emitter at 0. Maybe B and E, something is open along the circuit preventing it from draining or reaching fast enough per schematic voltages?
 
petehall347 said:
looking like a power supply issue then
Click to expand...
I’m out for now for visit. Will check the power supply section when I get back.

Pretty sure the two main caps gives the right voltages 39v and -39v. Those were the voltages I checked first and double check again.
 
petehall347 said:
check tr802 voltages first
Click to expand...
Per the attached schematic on my response to avionic up top. Red caption are my actual readings.
B,C and E voltages are well within schematic voltages. Please see attached snapshot.
B = 28.75v
C = 44.2v
E = 28.75v
 

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