Going back to my third post of this thread, which states:FACT #1, when the protect circuit is reacting on and off FASTER than the timing interval, it's the relay DRIVE part of the circuit.
Which is WHY I asked about watching PIN 3 of the PA3004 protect IC.
Disconnecting AWM-124's pin 4 connection is NOT the SAME as pulling Q1.
1 to 2 seconds delay with a NEW CAP??
Per a previous post, I already replaced FU6, but I'll try temporarily shorting it to see if I get any different readings. However, all my voltage readings at the board have always looked good, with exception of some ripple in the 65v supply, which appears to probably be normal, since I measured that same ripple on either side of the supply. Caps have been replaced for both the +65v and the -65v supplies.Check FU6, or test short it or just replace it for now.
If it is old age failing, fu5 could carry the 13v dc load alone or smooth over the intermittent, showing up ONLY at the AC 20v output of the power supply.
Hi, Rick. Thanks for your reply. I will need to verify these things when I get back to the shop but, according to previous testing:PA3004 is a failure prone device, based on a lot of threads with this issue.
You have to verify if it is the PA3004 or an actual fault that is causing it to to drive the relay driver bjt.
Tests to be preformed
Do you have DC offset at a power amp channel?
Do you have the over current trigger activated, you can remove the bjt that drives this summing node at pin 4?
Grounding pin 4 will determine if there is a problem with PA3004
Does the relay operate correctly with the drive bjt operating properly?
Do you have a clean supply at pin 1, ~13VDC
Do you have -7.6VDC at pin 6?
Pin 7 is the ac presence detector, it should have a low voltage AC from the transformer secondary winding.
Good Luck
Rick
It keeps the relay off as it should, since it turns Q1 on to drive the summing node.Grounding pin 4 of the protection board does stop the relay cycling.
I already have a spare PA3004 on order. Hoping to receive it later this week. I'm hoping you're right about the faulty IC - it'll make my life easier if I can replace it and have my relay cycling problem go away!It keeps the relay off as it should, since it turns Q1 on to drive the summing node.
pin 3 should not be cycling.
PA3004 is faulty, get a spare, put in a SIP IC socket so it easy to change out if fails again.
I have -13.28vdc at the anode of D1 on the protection board. O-scope shows me a nice, flat line @ 5v/division.What is the dc voltage at the anode of D1 on the Protection board? Is it clean DC looking at it with the scope?
Really, they weren't too bad. Most can be had for under $20, including shipping. I just have to wait for the slow boat from China. Either way this works out, I'm learning something.I know they are expensive, too bad, Pioneers failure imo was to get into custom ics, I wish they just kept with the original discrete design that they used for years or used a standard ic mfg, even a later SX-D7000 uses a discrete protection ckt, go figure.
something to make/design one day is a small pcb that will replace it.
here's hoping the new parts work out for you.
Really, they weren't too bad. Most can be had for under $20, including shipping. I just have to wait for the slow boat from China. Either way this works our, I'm learning something.
It would be nice to have a write-up on the procedure for checking protection board issues. Basically, check for proper, stable voltages (and ground) to the PA3004. Leave the preamp/power amp out/in jumpers disconnected. Disconnect speakers. Then it's down to pin 4 of the board and pin 4 of the IC. Not sure if the wire to pin 4 of the board should be disconnected or not (my guess is disconnect it). If the relay operates normally at this point, there's a problem with one or both of the amp boards. Continuing on, ground pin 4 of the protection board, then pin 4 of the IC - the results of the relay action during the grounding of these two pins should narrow down the problem to either the IC or the protection board.
Does that sound sort of correct?
I'm going on the assumption the spare protection board I purchased has a faulty PA3004, as well. I'd like to connect and test that other board the same way I tested my original and get both boards so they can be connected up and function normally.Yes, I believe so. Grounding Protection Board pin 4 should cause the relay to turn off, as this is the overload fault input. Grounding the PA3004 pin 4 should not affect the relay UNLESS there is an overload or dc offset fault signal coming in causing the relay to be off. If so the the relay should pull in, as grounding PA3004 pin 4 swamps the incoming 'fault' indication.
It appears we have exhausted the tests and have nothing left to look at until one of your new PA3004s arrive. The real conundrum for me is that the second board behaves the same as the original. Perhaps that is why it was for sale.
The least expensive (individually) I have found is to buy 10 PA3004s at one time, with free shipping, for $110. On our favorite auction site of course. Every other listing I have found is slightly to greatly more expensive.
I am hoping to acquire a protection board and set up a test bed to determine directly the limits and operational parameters of the PA3004.
I had a look at the protection circuit for an SX-950 this morning, thinking it might be similar-enough to adapt to an SX-980. Not so much - not without a lot of adaptation, anyway. I finally received a shipping confirmation for my first PA3004 - I should be able to install it by the end of the week. Hoping that closes this chapter of issues.Yes, that seems elusive. The block diagram seems to be the only readily available info:
The slow boat from China must have had a tail wind - my new PA3004 arrived yesterday. I installed it first thing this this morning, double-checked my solder connections and my jumper wires to the protection board, turned on the power and.......the relay continues to cycle! OMG. I disconnected wires from pins 4,5,6,7 & 8 of the protection board. I rechecked voltages on the PA3004 - all the same as my last check - everything checks normal. Grounding pin 4 of the protection board prevents the relay from engaging. Grounding pin 4 of the PA3004 does nothing - relay still cycles. Everything tests and behaves exactly the same as before. It appears it's time to go back to square 1 and start over. I'll read over some of the old posts and start there. I might pull Q1 as Mark advised and see what result I get.Yes, I believe so. Grounding Protection Board pin 4 should cause the relay to turn off, as this is the overload fault input. Grounding the PA3004 pin 4 should not affect the relay UNLESS there is an overload or dc offset fault signal coming in causing the relay to be off. If so then the relay should pull in, as grounding PA3004 pin 4 swamps the incoming 'fault' indication.
It appears we have exhausted the tests and have nothing left to look at until one of your new PA3004s arrive. The real conundrum for me is that the second board behaves the same as the original. Perhaps that is why it was for sale.
The least expensive (individually) I have found is to buy 10 PA3004s at one time, with free shipping, for $110. On our favorite auction site of course. Every other listing I have found is slightly to greatly more expensive.
I am hoping to acquire a protection board and set up a test bed to determine directly the limits and operational parameters of the PA3004.
That is interesting. Look at the ground potential difference between the ACTUAL metal of the PA3004's pin 5 and the actual metal of the chassis. Watch it through a couple of "cycles" first.Grounding pin 4 of the protection board prevents the relay from engaging. Grounding pin 4 of the PA3004 does nothing - relay still cycles.
I know there is a hankering to rush and "git er dunn", but PLEASE do this in a methodical order, you would be setting up a double double blind,Hmmm, that stinks, but it points back to power supply, as nothing else is connected. Do you still have that noise on the peaks of the +65v ripple? When you pull Q1, pull Q2 as well, then check PA3004 pin 3 to see if it is still cycling.
That is interesting. Look at the ground potential difference between the ACTUAL metal of the PA3004's pin 5 and the actual metal of the chassis. Watch it through a couple of "cycles" first.
Quite frankly, grounding the AWM-124 protection board's pin 4 is just signalling a protect condition, as pulling it LOW is the function of both AWH-073 power amp channel's Q8s.
I know there is a hankering to rush and "git er dunn", but PLEASE do this in a methodical order, you would be setting up a double double blind,
so please do q1 first, then see if pin 3 and q2 are behaving.