Marantz 2252b Part 3 - Modifying and Adjusting the Bias Circuit

Рет қаралды 6,959

Күн бұрын

Пікірлер: 38

@ohmbug10 11 ай бұрын

Tony, I kind of like when KZbinrs go off on tangents. It separates real people from fake Hollywood crap. That was a great story about your IRL job and being able to fix what the OEM couldn't. It says much about you and your coworker's abilities. And of course, nice job explaining the circuitry on this receiver.

@robburbrink8277 Ай бұрын

Tony I beg to differ on the idea that you're not a 'proper' educator, on the contrary mon frare, you are the best type of educator because you keep it light. please don't second guess yourself in telling stories, its all appreciated. your approach and methods are perfect for how I learn. dude I'm clocking like 10 hours a week at least on your channel, taking loads of notes, learning so much. thank you sincerely for the effort, its the best I've found yet on KZbin that appeals to my interests. you're the man, much love from Cincinnati!!!

@jaybats7865 8 ай бұрын

Nice work Tony, I really enjoy your videos. Intelligence coupled with humility and consideration, in my view, are the finest qualities one can have and you have them all in spades. Thanks for the fun!

@eduardomenendez1706 19 күн бұрын

Thank you for sharing and showing how to work on this beatiful pieces. Tony btw your a great story teller , I just got myself into the journey of restoring my late dad s marantz 2220 so this series its a nice learning tool for people like me that do this as a hobby

@Amplified208 11 ай бұрын

Love the art of electronics. Great video as usual love the solder and chat videos and the stories. Thanks for sharing your years of experience with us on KZbin.

@mjg263 7 ай бұрын

Excellent video and very clear explanation of the bias spreader circuit. Thanks!

@isoguy. 11 ай бұрын

Really enjoy these chatty vids, especially when you admit to mistakes, as these serve as real learning points for me; check, check and check again, though I'm equally guilty of not reading instructions on non-safety critical items. Though of course I never make mistakes. (if only!) This series is great, it makes learning enjoyable and fun; though not in the, everything has to be fun modern way of thinking. Can't wait till the next episode and as always thank you for the time you put into making these vids.

@RPike-bq3xm 11 ай бұрын

Tony, I love your channel and have picked up many new processes and techniques. I would like to comment on the wire wrapped pins. Those wraps are tight when originally made. Gas-tight as its listed for the wire wrap specs. The sharp corners on the pins gouge the wire making the connection. If the wire is unwrapped the nicked wire is basically rendered unreliable if used again. I see you solder after you rewrap but without flux it could end up unreliable in the future. I desolder the pins and wraps as one, leaving the wrap alone. Those pins would be easy to reach with a iron and a slight pull with a pliers, or better, cutoff pliers and a pry? This is only if I can't loosen enough harness to access without removing the pins. I like making the restorations like factory. Again, I love the channel and only make the comment with respect. Keep the wonderful content coming.

@adalbertus777 11 ай бұрын

Tony was doing exactly how you described it on some of his other videos. If I'm correct on the part 1 of this series he mentioned he could take pins out with the wire wrapped around them but had decided to go down the other path here. That's what I really like in Tony's videos (besides other stuff, of course). He's showing various methods, technics, skills, approaches etc. when servicing gears. It's good for those who learn from him and it also makes each episode more entertaining.

@richardmarshall6751 10 ай бұрын

Isn't there flux in the solder? Why would that be unreliable, unless you are saying the pins are nickel coated and don't take the solder?

@eatshitgoogle 11 ай бұрын

Tony: Are you bored yet? Me: Tony, you coudn't make a 'solder and chat' boring if you tried. I love it! 🤣

@stephensams709 11 ай бұрын

I agree with you about wearing jewelry. When I was in the military working on avionics, it was constantly drilled in our heads about wearing jewelry and sometimes to the point of being ridiculous. Since then, over time, I pretty much do as you do : )

@SergZak2023 11 ай бұрын

Thanks Tony….enjoying your channel and your content greatly. Keep up the great work!

@craigm.9070 11 ай бұрын

Thank you for your time Tony! Very much appreciated information in this video.

@davidwolverton4858 11 ай бұрын

Great job Tony

@merrittderr9708 11 ай бұрын

I've thought about saying something about the ring, but some folks are pretty adamant about keeping it on as part of their vows. I haven't worn my ring for years because I used to do a lot of automotive repair work and the danger of the ring getting caught on something and stripping the skin off my finger was a concern. Not to mention getting harsh chemicals under the ring and hurting the finger. (I know, gloves). In any case be safe and stay healthy.

@alexw890 11 ай бұрын

Another great one Tony! Thanks!

@Jim14872 11 ай бұрын

I like to set the bias on the cold side with the dim bulb off and set my variac to 120vac so I take the wall outlet voltage out of the equation. Then I vary the AC voltage to about 110-130 vac which is the most I have seen at the wall. And confirm it doesn't go over the spec or cause crossover distortion. I have tested the crossover distortion on most amps they need very little bias. 10-15 mv across the 2 emitter resistors is usually plenty. Then I like to add a little heat from the heatgun on the heatsink near the temp sensors to see that they are lowering the bias when heated up so it reduces chance of themal runaway. Then as it cools it should rise back up to what I set earlier. Thanks, Jim

@apollorobb 11 ай бұрын

I agree with you about the Bias . I run all mine on the cold side. I generally adjust mine with the Scope . I dont read much into what the service manual says . I cant stand an Amplifier that runs so Hot you think its class A . I really dislike working on the 2238 and the 2252 id much rather work on the 65,75,85 . Nice job on the re-Bias sir

@troy6882 11 ай бұрын

😃😄😁😆😅 5 Smile's there still a fantastic unit even today especially with the hole kit.

@somebodyx 11 ай бұрын

To find an optimum bias point it really takes FFT analysis for best harmonics profile. Another thing is if somebody wants to increase the Class A portion of Class AB up to what given sinks can tolerate. For more linearity in quiet program parts or for better low level detail with sensitive speakers. In a push pull amp you get ((Iq*2)*0.71)^2*Rload Class A power RMS. Then it slides to Class AB.

@mohimadvani6425 11 ай бұрын

super awesome and informative video ❤

@g.fortin3228 11 ай бұрын

Great to know those tips, especially about the bias not having to be spot on and can be set slightly lower.. may as well have it idle a tad cooler. that board was a pain tho''

@erikdenhouter 11 ай бұрын

Unlike this amp, many amps get their bias from the unregulated power supply. Better check the mains before setting, one of the reasons why the range is broad. It is not difficult to check how much the bias changes per mains Volt, and adjust accordingly.

@wizzkidelectronics 11 ай бұрын

great video i would have done the same . yeah they were biased on but i wouldnt have been happy i would have wanted to see at least 15 mv and i would have been second guessing the drivers gain . making it much harder on myself

@mackfisher4487 11 ай бұрын

Thank You

@williammiller950 11 ай бұрын

i like you ,good story

@anandadesilva6558 11 ай бұрын

Hi Tony, That was a great clip. the explanation with the various values of resistors for the bias adjustment was really nice. Since the voltage was creeping ever so slightly, I wonder if it will do the same while the amp is producing a signal. I mean, will you have to re-adjust with a signal fed in... even after the warming up period?

@andydelle4509 11 ай бұрын

Jewelry? I worked on some broadcast digital image effects processing equipment in the mid 1980s where they specifically warned you about rings and other jewelry. The upper and lower rack bays were both fed with 300amp 5volt power supplies in parallel. Hey, it's only 5 volts. But of you bumped that rail on the backplane, any ring would turn to liquid metal in microseconds. Damage from that means ultimate amputation! Short circuit protection? Sure, but your wedding ring just looks like a normal few hundred TTL gates pulling low.

@NiHaoMike64 11 ай бұрын

I remember at an Intel lab, one time someone blew up a prototype board by shorting it out with a ring. (Fancy 100A ATX PSUs were the preferred ones for powering up the boards, I guess luckily the board happened to be the weak link that time!) Not too long afterwards, there were reminders by the lab doors to remove conductive jewelry before entering.

@christophergetchell6490 11 ай бұрын

If you think that's hard to work on, imagine having to disassemble an entire AVR just to fix a couple of cracked solder joints. I miss the days of bottom access. That being said, there is some ease in removing boards with connectors rather than wire wraps!

@andymouse 11 ай бұрын

Great fix and setup. A decade box to hand perhaps to more easily set bias...cheers!!...Edit:- regarding the 'look' I personally don't like it because they have used 4 different fonts and it looks like a hobby kit ! again personally don't like the blue but that's how it was, I like the old 'grain of wheat' bulbs behind VU's that incandescent glow for me all day ! so I would have probably made it non standard if I was going to use it (philistine !)