• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Pioneer SX-1080 - No Delay Before Speaker Relay Engages

Brett Becker

Brett Becker

New Member
First post ever on AudioKarma so be easy on me. :)

There is one issue I can't figure out on a beautiful SX-1080 I'm working on. There is no speaker muting delay when you first turn on the unit leading to a nice pop and some impressive speaker cone movement. You can hear the two relays clicking almost simultaneously right after you flip the power switch. One of them being the speaker output relay.

When flipping the power switch, Pin 3 of the PA3004 IC, which is the output of the base to the NPN speaker relay driver transistor, almost instantly goes go 0.8V and stay there which is enough to kick on the relay. I can watch the timing capacitor (Qt) hooked up to Pin 8 slowly charge up to 8V after about 3-4 seconds, which from my understanding is supposed to control when Pin 3 goes high to flip the relay. It's almost like the PA3004 is ignoring Pin 8 for and there is something wrong with the IC. Anyone have any thoughts or experience on this? Everything else looks good on the IC as far as the pin voltages.

Thanks,
Brett Becker
 
Register to hide this ad
Brett Becker said:
There is one issue I can't figure out on a beautiful SX-1080 I'm working on. There is no speaker muting delay when you first turn on the unit leading to a nice pop and some impressive speaker cone movement. You can hear the two relays clicking almost simultaneously right after you flip the power switch.
Click to expand...
The other relay "click" is the "softstart" relay and it should be almost instantly.You have a problem with the protect circuit. Possibly a E-C short on the relay driver transistor. Q2 on the AWM-120 board
 
Last edited:
Brett Becker said:
Pin 3 goes high to flip the relay.
Click to expand...
What voltage are you seeing on pin 3 at start up? If Q2 is shorted it will instantly "set" the relay.Reguardless what voltages are on the PA3004 . Will also render the protect circuit unserviceable... Like no protect circuit.
 
Last edited:
avionic said:
The other relay "click" is the "softstart" relay and it should be almost instantly.You have a problem with the protect circuit. Possibly a E-C short on the relay driver transistor. Q2 on the AWM-120 board
Click to expand...

Yeah, I have checked Q2 both in and out of the circuit with my meter and with a transistor tester. The base voltage is 0.8V right away also.
 
avionic said:
What voltage are you seeing on pin 3 at start up? If Q2 is shorted it will instantly "set" the relay.Reguardless what voltages are on the PA3004 . Will also render the protect circuit unserviceable... Like no protect circuit.
Click to expand...

Yeah, I am seeing 0.8V basically right away coming off Pin 3 which connects to the base of Q2. The schematic says 0.7V so I am assuming that is enough to saturate the transistor and get the juice flowing. Q2 is a 2SC1438-V BTW.
 
I have seen several people here on AK buy a PA3004 NOS from the 'bay, about $11-$13 shipped seem to be the going rate. Look for one with a picture of the sip in a plastic bag with the Pioneer logo on the bag/label. This seems to be one of those strange occasions where there are lots of NOS items available so making fakes is not worthwhile :dunno:. YMMV
 
merlynski said:
I have seen several people here on AK buy a PA3004 NOS from the 'bay, about $11-$13 shipped seem to be the going rate. Look for one with a picture of the sip in a plastic bag with the Pioneer logo on the bag/label. This seems to be one of those strange occasions where there are lots of NOS items available so making fakes is not worthwhile :dunno:. YMMV
Click to expand...
Yeah, they all have the same date code so I was thinking they are all fake or someone found a huge stockpile somewhere. I ordered one off Aliexpress for $10 and we will see if it works. Thanks for the info!
 
If the Q2 transistor is shorted/leaky B-C it might/would exhibit the same symptom, pull the transistor and test it, they are easy to find replacements for, and cheap. Use Mouser 512-KSC2690A. 42¢
 
Last edited:
I have been buying PA3004 from the ebay sources, I have had no issues. Polida is one of them.
Check all your voltages against the schematic.
PA3004-2F1 sounds familiar. if they come in a Pioneer marked plastic bag and it is wrapped in Al foil they are genuine based on my use of them.
There are numerous reports of them failing, not sure for the fault as you describe. Install in a SIP machine socket, I use 575-3104710841001000
 
Last edited:
You must log in or register to reply here.
Back
Top Bottom