mbz

hifiengine has the HTR-6030 as 2007. Yamaha generally used good components, caps should be good for 30+ years. I've recapped plenty of 1970's gear, some needed it, some didn't judging by the sound quality. Plenty of good amps in vintage if you can invest the time to learn.

Possibly the only thing I'd look at are the caps on the regulated power supply board, normally top board with heat sink mounted voltage regulators. These caps have a low but noticeable failure rate triggering protection in the HTR's and RX-V's. Replace with Nichicon UPW from a reliable source. The amp will have a fair swag of SMT and the boards difficult to rework due to lead free solder. I would suggest leaving the amp alone. If you want to tinker then suggest you pickup a vintage piece and refurb that. An amp/receiver from Kenwood, marantz, pioneer, yamaha, sansui, luxman,,,wou

Certainly only connect low level inputs to the power amp. If the AVR has PRE-OUT RCA's then yes that would be the next step, connect from AVR PRE-OUTs to power amp input, hopefully this will help isolate problem. Have you tried a different source like ipod, iphone,,, (at minimum volume) connected directly to the power amp. Check through headphones on the AVR, expect same behaviour. Maybe intermittent connection on power amp speaker posts. Also swap RCA cables into power amp, maybe intermittent cable?

Where abouts in melb are you

Correct, the stepdown specs will show rated voltage is produced at rated VA. So if you get a 2kVA step down and run an amp which consumes 100-150W during quiet passages then the supply voltage will be 4-6% higher than rated voltage. These are generalizations, need to check transformer spec, eg, no load voltage. Need to decide on whether you go for the cheaper auto transformer or the isolated variant. A winding fault on an auto transformer may result in mains 240Vac being presented to your 110Vac amp.

Bias adj shown as RN51 in the ma-24 schematic, J705 contains test points for bias voltage measurements, need to locate service manual for voltage spec

Possibly the amp is in protect mode. The amp shuts down either 1 or 3 seconds after power on or does not respond to power on. You can read the protection history by the following key sequence, Note the text on disply, eg, DC PRT:015 Failed power supplies are common and a reasonably easy repair. Other faults can be very difficult.

What model number (MA-5?) need to track down the service manual. Did you measure the bias? Not real happy that tinkering with dc offset trimmer brought the amp back to life, maybe the trimmer is intermittent, generally marantz use good trimmers unlike vintage NAD (garbage...). If the amp is unstable (seen by power consumption) then I'd refrain from using it until you can check the bias. Maybe post a few pix of the boards/components of the problematic unit.

Nice pix Agree, everything looks in order. I wouldn't replace that transistor with heat sink, it would be a punt only. You are better off with an oscilloscope and a signal generator for sine and square wave test. A distortion analyzer would be even better so a trip to a tech is probably on the cards. If you want to take a punt, note the numbers on each transistor, ie, Cxxxx, Axxx ("2S" omitted) and compare against known vintage problematic transistors (from audiokarma). Consider replacing any "bad actors" you have.

Looks like pooly applied thermal heat sink compound on transistor/heat sink. Electrolytic caps show no signs of stress. Polar tantalums used (pic 2) these have a history of going (windy) noisy. Maybe post a pic of the audio stage/preamp. Loosing "some clarity" could be anything, both channels affected? Do you have a schematic?

Depends if you are confortable taking voltage measurements on a live unit (warning, lethal voltages inside). First step would be a basic health check of the power supply. Put the schematic on a (google?) shared drive, I'm looking at the TA-V715T, it shows the power amp with STK modules and uPC1237HA based protection circuit. I assume there is no faint click 4-8seconds after hitting the p-on button. Possibly the front panel lights are out. Looks like a 1.25AT fuse and a thermal fuse in transformer primary.

I've got an AU-505, refurb'd and 555 upgrades. Pair them with Altec 420A's(104-5)dB and Visaton TL-16H(106dB) tweeter, ok, it's not high end but can be had for under $1000 with crossover caps. Nice open sound, I don't mind turning off the consonance/osborn epitome gear.

Buy from a reliable source though I understand shipping to NZ is an issue. Preferred sources are mouser and digikey in the US, typically free shipping to AU on orders over $60-. RS stocks the LM4562 but they want you to buy a minimum of 5, https://au.rs-online.com/web/p/op-amps/1977299 I wouldn't buy semi's from jcay, certainly not off the bay.

NJM2043D for phone stage. LM4562 if you are wanting accuracy, nice tones OPA2134 if you want more body/timbre, nice tones. Choice depends on the equipment (signature) of the gear you are connecting to. Not a huge fan of jcay but then again it's about learning and having some fun. 2c...

Possibly a slightly dirty switch. Work through each/all switches in turn, ie, operate back and forth a few times and note any effect on balance.