Pioneer A-60 Protection

Hello everyone, I just bought an A-60 at a local thrift store today. When I got home and plugged it in no sound out of it tried with different sources and speakers. Opened and looked for any damage, no burned parts or bulging caps found. Found that the protection relay wasn't clicking in. Went and found the service manual and started looking at the circuit for the protection. Then using a DMM with the amp on I checked the voltage at the relay coil and the voltage of the in coming signal to the relay. Also measured the resistance of the coil with the unit unplugged.

coil voltage = 41.1 V dc. The manual shows 40.5 to be the normal.
Voltage of the input sides of the relay = 63 and 64 V ac. Couldn't find the spec in the manual.
Coil resistance 1113 ohms this seems a little high but the sevice manual doesn't give a specification.

Any help would be appreciated.

coil voltage = 41.1 V dc. The manual shows 40.5 to be the normal..........a little high because its not drawing any current
Voltage of the input sides of the relay = 63 and 64 V ac. Couldn't find the spec in the manual.,,,,,,what are these in dc ?
Coil resistance 1113 ohms this seems a little high but the service manual doesn't give a specification. maybe ok ....

petehall347 said:

coil voltage = 41.1 V dc. The manual shows 40.5 to be the normal..........a little high because its not drawing any current
Voltage of the input sides of the relay = 63 and 64 V ac. Couldn't find the spec in the manual.,,,,,,what are these in dc ?
Coil resistance 1113 ohms this seems a little high but the service manual doesn't give a specification. maybe ok ....

Click to expand...

The 63 and 64 is Volts AC. Those are the signal coming in, going out they are 0 because the relay is not engaging.

White_wolf said:

The 63 and 64 is Volts AC.

Click to expand...

but what is it in dc ?
i take it you are referring to the audio out from the power amp section that goes into the relay .?
no input to the amp vol turned right down

petehall347 said:

but what is it in dc ?
i take it you are referring to the audio out from the power amp section that goes into the relay .?
no input to the amp vol turned right down

Click to expand...

Sorry didn't quite understand you, they are the same in DC volts. Yes no input volume at infinity.

ok this needs looking at the schematic first off .. may take a while as its midnight here ..

ok ...this looks like fun ... lets start with the power supply first ....
can you read schematics ? and what equipment do you have ?

petehall347 said:

ok ...this looks like fun ... lets start with the power supply first ....
can you read schematics ? and what equipment do you have ?

Click to expand...

I can partially read them, basic circuits and things (Auto Mechanic by trade), but I'm not that experienced in them past that point. I have a DMM and soldering iron. Nothing else.

if you can find your way to the power supply and start taking voltage readings . it would be a good start ..then move onto the amp section ..
am turning in now as its late here ...

Power Supply Circuit

Multi-voltage model

Transformer
Pin 8 = 52.6 V ac
Pin 9 = 31.4 V ac
Pin 10 = 0 V ac
Pin 11 = 31.3 V ac
Pin 12 = 52.6 V ac
No DC volts at any pin

Where the scematic show +- 69.0 volts I have +69.0 and -69.4
where the scematic show +- 40.5 volts I have +41.0 and -41.1
I believe, not quite sure, that where it show +-20.0 I have +21.4 and -21.0

The last 3 sets should be DC voltages, Correct??? Label all voltages either AC or DC.

Looks like the P.S. is working as advertised. As it's a dynamic switching amp, you need to find the Dynamic Switching power supplies and make sure those are working correctly too. Read the section(7) starting on page 12 to learn about this. Basically at a certain point on the volume it switches from low power to highpower and kicks up the audio output some more.


Then on to the amp. The NSA (NON SWITCHING A Class) is a FINICKY, NON-FORGIVING AMP if you do something wrong. So go slow and be VERY CAREFUL!

Good luck. Pete can get you at least started in the right direction. If Mark the FIXER shows up you've got it made if you do exactly what is instructed an no more. Don't try and get ahead of them. You may end up with a 40# doorstop.

Larry

I have checked the voltages at every spot I could discern from the schematic picture (very bad copy by the way hard to see where some arrows were pointing) and they were all within 1-2 volts of what was listed at that spot. Also after having been on for awhile the output voltages into the relay are now at 67.4 and 67.8 dc volts and 67.1 and 67.5 ac volts respectively. I'm still wondering if the relay itself could be bad, in my line of work (Automotive) relay pull in coils usually have about 75 ohms of resistance this one measures 1113 ohms.

The power supplies seem to be ok on first glance.

The relay is a 1/2 watt core, @ 24 volts. The 820 ohm resistor dropping 40v to 24v means 16 volts with 19 ma of current and thus that 1300 ohms of resistance on the relay coil - It's OK...

I believe the protection is being TOLD to keep the speakers disconnected.

Check Q706's base voltage, to work it should be at 0.6v or greater which means that q706 should be conducting the protect relay's current through itself, and the q706 collector should be less than 2 volts, not pulling in will be 24v.

Check for +36v on the plus side of C413 (47uf 50v) in the power supply, that's the "weak" supply that signals shut down of AC power quickly before the other supplies get drained. It comes into the protect on D705. And beats the power drop weirdness by disconnecting the speakers

Basically you need to look at the output voltage of the amplifier channels, they should be near 0.000v either find them on the "hot": side of the relay contacts or at r713 and r714, both 15000 ohms brown green orange gold

either way (overvoltage (r713, r714) or overcurrent (d706, d707 remove them to eliminate their input)) the protect q705 is turned on, preventing C709 from charging and turning on the Q706 relay coil driver.

Q706= -2.72V dc 43.2V dc 0.00V dc going from the nerest to the relay to the farthest (I believe that -2.72V is the base.)

Resistors r713 r714 = 70 volts dc on one side 0.764 on the other both the same.

c413 = +41.2 on the positive 0 on the other side. at d705 I have +41.2 on the cathode and 0 on the anode. With Diode Check my meter reads 0.619 one way and OL the other.

In case it helps.

Q702 b = +62.0 c = +61.5 e = +70.9
Q701 b = +62.3 c = +62.0 e = +71.0
Q703 and Q704 b = +0.762 c = 0 e = 0
Q705 b = +0.009 c = 0 e = +0.570
Q206 b = -2.72 c = +43.2 e = 0

Resistors r713 r714 = 70 volts dc on one side 0.764 on the other both the same

Click to expand...

The amps are railed, pushed in one direction to their maximum voltage, and it's stuck there.

Start checking EACH AND EVERY solder joint in the power amp section, there are some transistors (Q509, Q519, q510, q520 = 2sa1145, 2sc2705) that are probably running too hot in this design as well as the sx-3900, sx-d7000 and so forth. They tend to crack or crystallize their solder joints. It may not show physically until you push on the wire with a sharp point - like a dental pick.
Also sometimes they go light on the wave solder and that causes weak joints.

It IS suspicious that both amps are railed in the same direction.

Then again, it could have something to do with this "dynamic power supply"...

This might not be an easy one.

It does look like those transistors you listed are/were running hot, here are the voltages in case it helps.

Q510 b = +68.7 c = +69.3 e = +69.2
Q520 b = -69.9 c = +66.4 e = -69.9
Q519 b = -69.6 c = +66.9 e = -69.9
Q509 b = +68.8 c = +69.5 e = +69.6

Went ahead checked all the diodes in both the power amp and dynamic power section these are the only ones that didn't seem right. these are the numbers my DMM gave in diode check mode.

D515 and D516 no current in either direction. not familiar with that diode symbol.
D509 0.722 and 0.615 flows current both directions
D510 0.722 and 0.611 same could this be feedback elsewhere
D610 0.715 and 0.618
D612 0.705 and 0.619
D611 0.706 and 0.613
D609 0.714 and 0.613

The rest mostly read around 0.615 except D601-D604 which read around 0.444

White_wolf said:

Went ahead checked all the diodes in both the power amp and dynamic power section these are the only ones that didn't seem right. these are the numbers my DMM gave in diode check mode.

D515 and D516 no current in either direction. not familiar with that diode symbol.
D509 0.722 and 0.615 flows current both directions
D510 0.722 and 0.611 same could this be feedback elsewhere
D610 0.715 and 0.618
D612 0.705 and 0.619
D611 0.706 and 0.613
D609 0.714 and 0.613

The rest mostly read around 0.615 except D601-D604 which read around 0.444

Click to expand...

d515 and d516 are 4 diodes inside in series and very likely wont read on your meter ..they can be tested with a 9v battery and resistor ..dont worry about these for now ..

with the other diodes you are reading transistors that are connected to them ..you need to unsolder one leg to test .

I talked about solder joints, NOT TURNING IT ON!!!!!

Nor specific readings. You JUMPED AHEAD OF ME.

Strike one.

I will figure out the useful readings to make, and post instructions...