So a co-worker blew this AV Receiver and wanted me to take a look, found the SBL final stage Transistors shorted, I cut them out of circuit to see if the receiver would stay on and not go into shutdown.

It stayed on, now I'm looking at the pre-amp for issues, found a bad diode, resistor, and small transistor so far. But using my MM only which is working but, I purchased a Frequency Geni 15MHz with several functions itching to try and learn to use it. @JoeJester has been kind to help me and mentioned he may be of assistance.

Service Manual is online and has a Magna fine glass to enlarge the circuit, page 12 - 13 has the amp circuit.

https://www.manualslib.com/manual/1055398/Onkyo-Ht-R570.html?page=13#manual

I have to put down some cement tomorrow and Friday before old man winter marches in, we're expecting snow Monday. So, I'm not going to work on it till next week.

kv

Edit: Oh, ya I also have a scope Analog and Digital. Still trying to learn to use it as well.

Model of the Geni HP 15MHz Function / Arbitrary Waveform Generator Model 33120A

Oscope is Agilent S4622D Mixed Signal

 

I grabbed the manual, and put the two amp pages to one schematic. I have a program that converted the manual to jpg. I did one at 2400 dpi .... Damn big file. Settled on 300 dpi, an E size drawing.

I also noticed all the block diagram, a rarity these days.

So what was the initial fault indication?

That has more functional tests then I've seen in a while.

When you remove power to the power amp board can you test the other circuits up to the power amp input?

An ESR tester would be handy. You can build one...there are plans on the net for them.

 

My co-worker said he was hooking a speaker up with the Receiver turned on. He said it went pop and when he tried to turn it back on it went into shutdown.

Yes, I like on page 12 in the above notes: they tell you how to set up the test point with the 2-100 ohm resistors in series and a female connector to go to a MM.

I'll have to take another look on how the Audio Processor is connected next week when I can tear into it. I've just done some random tests to parts I can get to.

Yes, I have an ESR Meter.

First thing I thought of was check the final stage and sure enough they were shorted, cut them out of SBL circuit, the unit powered up so then I decided to check the pre-amp. I'm working tonight and I'll find the part numbers to what I've found so far and post them when I get off work. I'm glad they listed part numbers in the back too!

kv

 

I have a master key to my co-workers office and drove across campus, the class ended early and obtained the correct circuit SBL.
Finals Q6065, Q6055. Pre-amp Q6015, D6005, R6105. I need to check the 47k ohm resistor connected in series with D6005.

I can't separate the inputs from the Amp board.

kv

Edit: I didn't add Q6035 and Q6045.

 

So I had a chance to tear it down Q6035 and Q6045 and D6005 are ok. I was getting some strange readings until I pulled Q6105 and it's leaky.

I have already ordered Q6065, Q6055 only (one side) of the double resistor package .22k R6105 is open so, I'm just going to drop a (.22k - 2 watt) ceramic metal resistor to replace the open side of the resistor. The reason I'm not replacing it with original part is because I can't find one since I'm good on one side of the double resistor why not just replace the blown side with a single Metal Ceramic Resistor.

But, I have a question? when testing those Metal Ceramic Resistors doesn't make any sense, When I measure the Metal Ceramic resistors in the receiver instead of a normal 220 ohms or .22k which is marked on the resistor and schematic I measure .5 ohms not k-ohms but .5 ohms? Even if I remove them from the circuit in or out of circuit I still get just .5 ohms. Do they need to heat up or something to get to .22k? Can anyone explain this to me?

kv

Edit: While I'm waiting for parts, I'll build the Test Jig so I can measure the pre-amp voltages I need biased.