Planet Audio PA4004 protection problem

[dre0011]

My friend gave me a Planet Audio pa4004 amplifier the protection light cycles on and off, with and without speakers hooked up. Ive opened the amplifier to check for any visible damage such as blown components or burned traces but came up with nothing...now im in need of some expert direction as to where i go from here to get this thing working again... Any help would be greatly appreciated!! Thank you.

[1moreamp]

Originally posted by dre0011
My friend gave me a Planet Audio pa4004 amplifier the protection light cycles on and off, with and without speakers hooked up. Ive opened the amplifier to check for any visible damage such as blown components or burned traces but came up with nothing...now im in need of some expert direction as to where i go from here to get this thing working again... Any help would be greatly appreciated!! Thank you.

Start ohming out your output devices. Sounds like one or two might be shorted, and your protection is just recycling on and off because of possible bad outputs or more

[dre0011]

Don't wanna sound clueless but when you say the output devices are you refering to the RCA outputs or other components?? Thanks...

[1moreamp]

Originally posted by dre0011
Don't wanna sound clueless but when you say the output devices are you refering to the RCA outputs or other components?? Thanks...

Thats ok i was referring to the power devices in the audio section of the amp they are the ones clamped to the sink with bars and what not. they should be ohm'ed out with a volmeter with the amp NOT powered. they will read in the 10 ohms or less range typically when blown.
Let me know what you find. if possible post a pic or two and i or someone else will roadmap you thru the amp.

[dre0011]

pulled them out of circuit last night and tested each one...they all checked out...how does the thermal protection work? is there a way to bypass this to eliminated it from being a possible problem or is there somthing else i should look for next?

thanks

[1moreamp]

Originally posted by dre0011
pulled them out of circuit last night and tested each one...they all checked out...how does the thermal protection work? is there a way to bypass this to eliminated it from being a possible problem or is there somthing else i should look for next?

thanks

Is the thermal protection giving you issues? It was meant to protect the amp from thermal related failures like fire and heat related semi failures
Why do you want to render it useless. or ineffective at its job???
I have never seen them become a real trouble issue, and rarely are they the cause of amp failure on a permanent basis.

"Start ohming out your output devices. " removal should not have been needed unless they were found to be bad.

Start looking for shorted power supply diodes and lower supply failures on the + - 15 volt power supply.
Let me know what you find

[dre0011]

I did end up finding two transistors that were bad...The next question is where can I find them or somthing that will work? They are Sanken C4466 I could only find them in quantity of 50+...do you know any local places in the Northern California to locate them??

[1moreamp]

Balbani, and others will sell them to you in smaller numbers. Just goggle the net with the number.
Oh the number is 2SC4466, the C4466 is the last part of the entire part number, they leave off the the 2S indicators as most tech's would know that all Asian semi's use the 2S designator..
I'm sure I have them in stock, But i run a shop so I don't resell parts except in repairs.
Plus I get better prices for them installed if you know what I mean

But there available worldwide as SANKEN makes some of the best linear output transistors for audio, and are known worldwide for that one reason. as always I hope this is found helpful