Wow this is great information. Promising that the switch may do the trick. Great information on the schematics and the routing. Very cool even if mostly over my head. The fuses I did check while in there last time and they looked good. Might be worth replacing while I'm in there. The soft start relay. Not sure if that would be available.
Jean Paul. You lost me at "eh" I realize I am not at the level as probably most of you. The PCB that the switch is connected to is something I need to look at more closely as well. If the switch doesn't work. I am not sure how testing equip works. So that is when I may need to educate myself some more and either dyi or find a local tech.
You are dealing with mains voltages which can be deadly - it would be safer to hand it over to people who know their ways around 🙂
Yes thanks. I am aware of capicitors, transormers and high voltage. I usually know my limits. Emphasis on usually.
I still advocate rearranging the AC wiring. After further study, I would simply short switch terminals S1-S2, thus bypassing the suspect pole. With luck, that will fix the problem. The amp should behave normally without having to replace the switch.
Maybe OP can also use aluminum foil in place of the fuse?
How can one recommend one this to a layman?!
How can one recommend one this to a layman?!
Don't you need to short switch terminals S3-S4 as well?
If you short switch terminals S1-S2 but not short switch terminals S3-S4, every time you plug in the amplifier to the mains, the amplifier will start charging its filter capacitor through the soft-start circuit and after a few seconds the speaker relay will turn on even if the power switch is not pressed. And the amplifier will not turn off until it unplug from the mains.
The assumption (needs to be confirmed) is that the S1-S2 section of the switch has failed open, so I suggest shorting its contacts as a remedy. The other half of the power switch continues to work normally, as evidenced by Larry hearing relay click.
Operation is as follows:
Initially power switch is off, RY901 is open. There is mains voltage at TM1 because switch terminals S1-S2 have been shorted but no power flows to the large power transformers T001 and T002 because the relay is open.
When power switch is pressed, AC power is applied to the small transformer T101 and RY901 energizes about a second later and operating power is delivered to the PA.
When the power switch is toggled to the off state, RY901 drive is removed and the PA powers down. The RY901 contacts handle the large current at both turn-on and turn-off.
Operation is as follows:
Initially power switch is off, RY901 is open. There is mains voltage at TM1 because switch terminals S1-S2 have been shorted but no power flows to the large power transformers T001 and T002 because the relay is open.
When power switch is pressed, AC power is applied to the small transformer T101 and RY901 energizes about a second later and operating power is delivered to the PA.
When the power switch is toggled to the off state, RY901 drive is removed and the PA powers down. The RY901 contacts handle the large current at both turn-on and turn-off.
Best, I have no idea how I would "short switch" terminals s1 & s2. Nor how to confirm that it has failed open. This sounds great in theory.
Best, RY901 is listed as an automotive relay. Listed for over 100.00. This is a component in my unit? Any techs out there recommended in Mesa Arizona?
Please adapt to the tech world and use brand names and type numbers. Makes it way easier for all.
There are many "automotive relays". There are also normal relays available as "automotive relay". Automotive is a buzzword that means they'll cost more. "Medical" is even better. Your device needs "industry". If the wallet is fat you can use "For Audio" and pay the double for relabelled industry quality.
Here we deal with (for instance) Schrack RY531024 that is DPDT and has 8A contacts (example). Then nasty types like me will write that you can upgrade to 10A contacts, use an Omron FY67024 with bifurcated tungsten contacts for longer service life etc.
Larrymrn, I think your knowledge to repair this yourself is insufficient at this moment. Please have an experienced tech replace both relay and switch. You can use shared knowledge to find a more sturdy relay but diagnosing, soldering and testing is better done by someone more experienced. Forget any suggestion to accept an error or to short contacts (really?!) as the device will not be in nominal state. Insurance companies love that.
There are many "automotive relays". There are also normal relays available as "automotive relay". Automotive is a buzzword that means they'll cost more. "Medical" is even better. Your device needs "industry". If the wallet is fat you can use "For Audio" and pay the double for relabelled industry quality.
Here we deal with (for instance) Schrack RY531024 that is DPDT and has 8A contacts (example). Then nasty types like me will write that you can upgrade to 10A contacts, use an Omron FY67024 with bifurcated tungsten contacts for longer service life etc.
Larrymrn, I think your knowledge to repair this yourself is insufficient at this moment. Please have an experienced tech replace both relay and switch. You can use shared knowledge to find a more sturdy relay but diagnosing, soldering and testing is better done by someone more experienced. Forget any suggestion to accept an error or to short contacts (really?!) as the device will not be in nominal state. Insurance companies love that.
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I don’t want to encourage you to do anything you’re not comfortable with. You seem aware of your skill levels. Trust your instincts and be safe.
I assume you have a multimeter and are comfortable using it.
Before attempting any repair, the easiest way to troubleshoot is to catch the amp in its failed state—- that is, with power switch on indicated by the relay clicking on about a second after the power switch, but the amp remains without any other activity. Now if you probe with AC voltmeter with respect to AC neutral, you should find 120VAC on both terminals 1 and 2 of TM1, but if the switch is failed open, only terminal 1 show 120V and terminal 2 will be at 0V. If you find 120VAC present at both terminals 1 and 2, suspicion shifts to the relay contacts. More troubleshooting needed at that point.
If you’re not comfortable with measuring live voltages (stay safe!), with power off, add test wires so that you can bring points of interest out to your meter and arrange to measure handsfree. Then you can switch power on and get a reading well clear of hazards.
If you confirm that the S1-S2 section of the switch is failed, the easiest fix is to install a short wire between terminals 1 and 2 of TM1. This shorts across the failed switch contacts. With luck, the amp will operate as you hope.
Good luck!
I assume you have a multimeter and are comfortable using it.
Before attempting any repair, the easiest way to troubleshoot is to catch the amp in its failed state—- that is, with power switch on indicated by the relay clicking on about a second after the power switch, but the amp remains without any other activity. Now if you probe with AC voltmeter with respect to AC neutral, you should find 120VAC on both terminals 1 and 2 of TM1, but if the switch is failed open, only terminal 1 show 120V and terminal 2 will be at 0V. If you find 120VAC present at both terminals 1 and 2, suspicion shifts to the relay contacts. More troubleshooting needed at that point.
If you’re not comfortable with measuring live voltages (stay safe!), with power off, add test wires so that you can bring points of interest out to your meter and arrange to measure handsfree. Then you can switch power on and get a reading well clear of hazards.
If you confirm that the S1-S2 section of the switch is failed, the easiest fix is to install a short wire between terminals 1 and 2 of TM1. This shorts across the failed switch contacts. With luck, the amp will operate as you hope.
Good luck!
Even though it's obsolete, you still can find it at some online site.
OZ-SS-112LM1F 12VDC 16A Normally Open Power Relay
BTW, the purpose of RY901 is to bypass the soft start.
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Thank you chrisng! I‘m embarrassed that I completely missed that detail and must retract my entire pitch. There’s no easy way to avoid needing to replace the power switch. My apologies to all.
I ordered RY901. Thanks chrisng for the relay link. Thanks everyone else for the input. Can anyone point me to a link for the correct power switch? I am going to take it somewhere. This has been very helpful.