Spec 2 in Protection Mode

bikerdon

Active Member
I recently picked up a Spec 2 off CL that is not functioning. The protection light was on when I bought it, so I knew it had some kind of issue.

The first time I powered it up, the relay clicked a couple of times, but the protection light never went off.

The next time I powered it up, the Relay clicked after a few seconds, the light went out, then about 5 seconds later it clicked again and the light came back on.

I powered it up again and the relay never clicked.

I am thinking that perhaps the caps that power that circuit my be bad because the unit is pretty old. I haven't pulled the cover off yet, but I was contemplating doing a full recap.

I am not super experienced, but I have done a recap on a few other receivers....

Any suggestions would be helpful, I do have the original schematic as well.

Don
 
Don,
Don't jump to conclusions that a bad cap(s) is/are the issue. The Protection Circuit most likely is doing it's job.
If you're handy with a DMM, you cam measure the DCV at the common terminals of the relay, Both channels are connected there. This will give you positive proof of what's going on.
Hope this helps.
 
Spec 2's usually need a full rebuild, with a few new reed type relays tossed in.

Intermittents turn out to be bad bias circuit relay or overworked driver transistors.
 
I see the relay on the meter board has pins 29-35 that look like the supply power to the entire unit.
What kind of current should I be looking for?
Do I measure pins 29 & 30 and also 32 & 33?
 
Those relays I spoke of, are NOT the plastic cube ones, although the plastic cube ones can also cause problems.

These are the itty bitty RL1 , asr-017 single pole (single switched circuit) normally open (means power through the coil makes the reed operate and close, completing the circuit) reed type relay - one of two on the corner of each amplifier card. They switch on the bias circuitry which use the STV-3h thermal bias diode. When they go bad, nasty things happen.

The second one, next to it on the board closer to the edge is called RL2 asr-005, but that one is a double pole (2 switched circuits) normally open and only affects the power limiter circuit.

Look at the pins 19,20 voltage to ground on EACH amplifier card - this is the audio output and this will tell us if a channel is railed and putting it into protect, it IS literally the DC offset voltage.
pins 29, 30, 31, 32 feed the primary side of the power transformer and are connected to the power line!!! they are the inrush control relay!! if it didn't operate, the unit would be strangled continuously, b ut it wouldn't put it into protect. The R67 4.7 ohm 5 watt inrush resistor would stay in circuit, heating up and eventually popping itself. No thermal fuse shows up in THIS circuit.
 
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I measured pins 19,20 on both boards, I also inspected the STV-3H and the STV-4 diodes and they "appear" to be good with the wires connected, however one of the STV=3H (this is the board that has no measurable current)has the connecter turned a bit sideways so it is hard to tell if the wires are ok. I know these things are very brittle so I don't want to touch them to be honest.

L19 -165 mv
L20 +165 mv

R19 and R20 virtually no measurable voltage
 
I followed this advice from Echowars>>>>FYI, usually the current mirror transistors are the cause of major issues. Q4, Q5, Q6, Q7. I replace these with On-Semi MJE15032 and MJE15033. I also replace the bias interrupt relay: http://www.audiokarma.org/forums/sho...d.php?t=113229

>>>>>>

Now when I power the unit on, the relay clicks right away, the protection light goes off, but after about a minute or so it goes back on. I let it set for a while and powered it on again and tested the idle current. If is suppose to read 30mV, but I am only reading 16mV on each board.... then it goes into protection mode again....

Anyone have any suggestions?
TIA
Don
 
There is a vital difference, on the awm-081 meter board, pins 15 and 16 (some schematic listings of 5 & 6 are WRONG!!) are monitoring the amplifier L & R outputs, and are non adjustable, but ideally should be 0.000v dc to ground. This is "offset".

Have you read Amplifier Distortion, DC-Offset, and You! this thread?

Then there is the idle current adjust.

Did you set the idle current after changing the transistors? to what value? Was that the 16mv that's supposed to be 30 you were speaking of?
That is a 0.030v dc target.

Are the heat sinks hot when it clicks out, one channel's could be if the idle current is too high..

The directions are crap for setting the idle current, pins 24 or 25 or 26 are the red dmm lead, pins 11 or 12 or 13 is the black dmm lead.
The pin numbers should be ON the board.

read and post the awm-081 meter board pins 15, 16 and 21 voltages to ground before and after it goes into protect.
 
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If it's kicking into protection that quick, there's no time for it to heat up, and no time to adjust the bias. But with power off, the bias adjust pot should be set to minimum resistance to make sure that the current flow through the outputs are not part of the equation as you try to determine WTF is going on.

The Spec 2 is a maze of relays, but the speaker relay sounds different than the rest (although it's hard to see). The Spec 2 has overtemp monitoring, offset monitoring, muting for impedance switching, and turn-on/turn-off muting. Any issues with this rather complicated circuitry controlling these functions may keep the unit in protect mode.

Might mention that the meter board is wired with lots of solid-core wire that's easy to break. Look over the connections carefully. Also, measure the voltages as Pins 15, 16, and 21 on this board.
 
I measured Pins 15, 16 and 21 before going into protection and after:

15 / 16 / 21
Before
1.4mV / 7.2 mV / 15.8 mV
After
1.4 mV / .9 mV / 15.9 mV

I monitored pin 15, and it climbed from 1.4 to over 4mV before the protection circuit clicked on... Then I could hear some relays clicking on and off (every 15 seconds or so)for about a minute before they stopped.

Also, after it has been on and gone into protection mode, it needs to set for several hours before it will power up and have the protection lamp go off.
 
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Pin 21 and 22 should be at around 15V when things are normal. This is set up by 90-something volts coming in on Pin 23, and knocked down to 15V with the 15K 1/2W resistor and a 15V zener diode.

Check the voltage again on Pins 21, 22, and 23. And make sure that the rear panel "4 ohm/8 ohm" switch has been shot with DeOxit and is in the 8 ohm position. And make sure that your negative meter lead is on a reliable ground (there's a good one on the main chassis next to the far left power supply cap on the underneath).

If you have 90-something volts at Pin 23, but nothing at Pin 22, then the 15K resistor is likely open. If you have 15V at Pin 22, but zilch at Pin 21, then one of your PTC thermistors is disconnected or is open. Or there's a busted wire somewhere that you have missed.
 
I did what you described and measurements are as follows on the meter board

Pin 23 88 mV Pin 22 16.2mV Pin 21 15.8mV

The only thing that changed on these measurements after it went in to protection mode, was Pin 23 dropped to 84 mV
 
Check your fuses. Five of them on the vertically mounted middle board. We need volts on Pin 23 before it's gonna come out of protection.
 
checked all five fuses, all looked good and tested good...

After retesting pin 23, I notices that the "m" went away on my DMM and it was measuring Volts not mV all the numbers previously measured were in volts not mV... sorry for the rookie mistake..
 
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Read the SM...pages 8, 9, and 10. Does a lovely job of explaining the function of the protection circuit (except I wish they had stayed with the same component designations as on the full schematic).

First stop: read the voltage at the base of Q11 on the meter/protect board. The transistor should be off, so the voltage on the base should be some positive value (15V, I believe).

If this were on my bench, I'd be tempted to swap out Q11, Q12, Q13, and Q14 just to be done with it (though Q9 and Q10 could still be an issue). Probably toss in new diodes at D29, 30, 31, and 32 while I was there.
 
I tested Q11 and was getting 6V at the base.
If this were on your bench I would be a lot happier too!!!

Anyway, I will take your suggestion and replace all those parts, I got the part numbers but none of them come up from mouser.
Is there someplace you go to to find new replacements for old part numbers?
 
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These transistors are used as switches, so anything with decent gain and can handle the current and voltage is fair game. Also, since Pioneer uses a circular (or some call it triangular) PC board layout for the device holes, you can use either a ECB or a CBE pinout to the transistors.

Forgot to ask...you got 15V on the emitter of Q16? Should also have the same voltage on the emitter of Q11.
 
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