pioneer sx-727 no relay click

scotha

Active Member
Looking for advice, my 727 powers on but the amp will not turn on. All fuses are good I have 36v at pins 19,20 23,24 15,21,22 on the power amp (AWH-011). I have 35v on pin 14 on the protector board (AWM-011) should be 8v. On the power supply (AWR-011) I have pins 7,14,15 at 36v pins 5,6 at 28.8v pin 8 at 48V pins 9,10 at 36.7 Vac and pins 12,13 26.5 Vac. Using DBT nothing appears to be shorted. Everything looks clean no burns or bulges. Should the ac voltages on pins 9-13 be higher? Thanks for any help.
 
I have 36v at pins 19,20 23,24 15,21,22 on the power amp (AWH-011).

Those are all correct (DC voltages) provided the polarity is correct. Chances are that it is.


I have 35v on pin 14 on the protector board (AWM-011) should be 8v.

That voltage would drop to about 8-10 VDC once the protection circuit is satisfied and the transistor Q7 conducts, causing the relay to operate.


On the power supply (AWR-011) I have pins 7, 14, 15 at 36v

Those are correct, according to the diagram markups.


pins 5, 6 at 28.8v

Those seem appropriate.


pin 8 at 48V

That seems reasonable given the AC input on Pins 9 & 10.


pins 9,10 at 36.7 VAC

Probably O.K. since the DC output voltages at Pins 5, 6, & 7 are within the proper range.


pins 12,13 26.5 VAC.

That seems correct given that the DC output voltages at Pins 14 & 15 are correct.


Should the ac voltages on pins 9-13 be higher?

Since the DC voltages of the rectifier sections are within range, the AC voltage seems adequate. Look at the formula for filtered half- and full-wave bridge rectifiers to predict DC output from AC input, and they seem O.K.

It would seem that the reason for the protection circuit to prevent the relay from operating is not in the power supplies.

Verify that there is at least 6 VAC on pin 17 of the protection board (AWM-011).

Check the DC voltages on the power amp board (AWH-011) Pins 5, 6, 11, 12, 13, & 14.
 
One note: the voltage measurements of 5,6,11,12,13,14 are near zero normally, and 0.010 would be significant and tell us things about the health of the unit...

Don't want to step on Watthours toes here... :D (Thank You )

For your peace of mind, the amplifiers do not seem to be misbehaving either. Thus it may be a good idea to rebuild the protection unit - it's not hard, 4 capacitors and several transistors.

Look around inside the 727, look for any small Sanyo Capacitors that are sky blue in color - it's probably NOT them in the protect circuit problem, but they cause mischief elsewhere AS they (all eventually) fail. Best pro-active thing you can do for your 727 is to replace them.
You can find them in the manual's parts list because they are called electrolytic and also CSSA.

for example in the AF unit
C27 ELECTROLYTIC 2.2 25V CSSA 2R2X 25

The rest of the electrolytic caps will eventually need replacing ("re-cap") but these CSSA caps are particularly troublesome.
 
...Don't want to step on Watthours toes here... :D (Thank You )

Not a concern at all - My toes are quite forgiving. We're all here to learn and share, and I'm a firm believer that more information is almost always a good thing.

Besides, it's already been established that experience and cunning will trump youth and beauty almost every day. ;)
 
Thanks for the input, It has been a garage unit for several years it has cut out a couple of times but always restarted until now. I will rebuild the protection board and see what happens. Thanks.
 
Rebuilding the protection board may or may not help. Those circuit voltages, in millivolts, can be critical. They represent current values in the output amplifiers which can be harmful, and are generated across the low resistance emitter resistors, thus the very low signal levels.

These are also the voltages which WOULD appear at the speaker terminals IF the protection relay were closed, and thus are the same as the DC offset, in essence. These are always adjusted to the very low millivolt ranges if possible and the protection board really has no bearing upon that.

Just trying to spare you from any unnecessary work.
 
Hello, so i replaced all electrolytics and transistors on the amplifier and protection board excluding D8, D9 on the protection board, and all electrolytics on the power supply and the blue sanyo caps on the tuner board. No change amp is still in protect mode. Ran the pre outs to another amp and the tuner works fine. Any other ideas?
 
Pins 5,6 are at 0 also.

I think we got mixed up on the Amp and Protection readings.

Pin 16 on the Amp board supplies the -13v for the protection board pin 6.

Never mind if I am missing something.
 
If you want to replace the relay.:D

You may be able to re-use the original cover due to the way it mounts.


DigiKey: Z191-ND
Mouser: 653-LY2F-DC24
 
Jumped the relay and the receiver is working. So either a bad relay or no signal to switch the relay? What do you guys think?
 
I had the same problem with my 727. A drop of DeoxIT D5 on each relay contact point resolved the problem.
 
.007 and .006 at speaker terminals without speakers connected volume turned down and receiver on aux with no source connected. It has been running for hours problem free. Still need to clean the relay.
 
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