Diagnosing and servicing a crusty Denon PMA-770 integrated amplifier

[@billmcdonald2436]

Definitely one of the best explanations I’ve seen on to-3 transistor testing that I’ve seen . Thank you

[@steveneal5267]

Great troubleshooting on what appeared to be a hopeless case. Always enjoy your old amplifier 'surgery' classes, with plenty of helpful tips. Keep up the good work.

[@justincowen7657]

I just got the same amp, but much much worse condition. Looks like it was under a pile of garbage for 20 years. Vacuumed it out, deoxed everything, twice. And it is fully functional (while not pretty) and sounds great. Minus the lcd screen, which I'm gonna try and repair. Good video!

[@theoryismypraxis3538]

these are actually worth 300-350 usd. and it's one of the top of the line pieces. i have a fully working version coming over to me in mail tomorrow. My friend has a unit, hes said that it sounds absolutely brilliant. its also incredibly reliable

[@lurkersmith810]

Wow, if I had one of those, I'd NEVER get rid of it! (Actually I did have one of those, and still have it, in storage and in much better shape than that one.) It was part of the best audio system I ever had. The input display is, if I recall an LCD that is back lit by a bulb somewhere inside. (I never got around to fixing mine either.) It's sad for me to see such vintage high end audio equipment poorly neglected. Not enough respect for the higher end stuff from the 1980s. I once saw a Nakamichi Dragon cassette deck (arguably the best, most expensive cassette deck you could buy), rusted and beat to crap, having been shown the disrespect I wouldn't even show a no-name kid's deck. Glad to see a vintage Denon (Nippon Columbia era) component saved!

[@jameslucas6589]

Your question of the tech that worked on this board prior is not unusual today. Everything is plug in boards on modern equipment as you know. Techs not familiar with old school knowledge are not able to service a dead battery in a key fob. I took my Marantz 4400 quad into be serviced and it was returned unserviceable.i.e. I'm not smart enough. Shame. All the repair shops have closed because it's a throw away society. $25-100 amplifiers. Garbage. But that's what fast food Americans want. Hell, any group of people that would elect a moron would have no interest in a quality product. Great video. Yes it was a big help to me as all your videos. Shango066 mentioned you knew your shit when it comes to audio. Yep, he was right. Thank you

[@waltschannel7465]

Right you are, and then add the whole Raspberry Pi dimension. The student thinks they know electronics because they're staring at a bare board full of components, and sorta making it work, but at best they are learning how to program in Python. Great skill but it's not actual electronics.

[@pvb9964]

The moron was turfed in 2016, and replaced with a real businessman

[@nerdywolfi]

That cleaned up very nice. Good job and thanks for the video

[@justsumguy2u]

Love the troubleshooting, very interesting. I wouldn't have minded hearing a demo with speakers, though

[@dewdude]

I have one of these. They're from around 1981; I think by 85 they'd "replaced" it in the model line. It's a extremely fantastic amp. My input switches are gone, no amount of Deoxit helped. It currently lives with a pair of RCA jack pigtails soldered directly to the input on the main board. I'm planning on replacing it with a much simpler input relay board controlled by an Arduino using a small OLED to replace the input display LCD...gets rid of all those unnecessary series connections. Mine's a tank..it's been abused and looks a lot worse than what yours started with...but other than the input switches, an output relay that needed cleaning, and a phono stage I never use that doesn't work...I'm honestly quite surprised mine is still on all original caps.

[@mikemorgan5015]

It seems like an infrared camera would help isolate hot spots quick, fast, and in a hurry compared to reliance on the olfactory senses. Might be worth the investment. Very interesting to see a true professional at work here.

[@charlesbickenheuser8281]

Your Videos are always very interesting. Thanks for sharing

[@saarike]

Great repair and troubleshooting!

[@JustinAzeiMusic]

I have this amp for 14 years. What new amp should i buy to get better everything? And is it worth it to do that? Im happy with quality but almost 50 years passed. Maybe its worth to buy a new amp for example 500eur?

[@billwilliams6338]

JORDAN PIER< you disconnected the "Speaker resistor loads" on the left and right channel to measure if the pre-driver transistors are good or bad? I didn't know you can disconnect the speaker resistor loads on the speaker output jacks to measure each receivers channels output

[@mspysu79]

What a rust bucket, but nothing like the ones that Shango066 finds! It cleaned up nicely though.

[@mikemurphy5336]

thanks for a great vid again !! also you might want to re edit the this video you mistakenly added the 2 or 3 take twice, or the second to last take is a duplicate added error, which threw me off at first, okay keep up the good work......... mike !!

[@pvb9964]

Stylish, much classier the black PPJ today

[@tigerelectronics5966]

Heh, when amps get this crusty I fix the essentials to make at least one input work, and use them for my outdoor sound systems until they blow up. X3 some of these older hifi amps push quite hard actually, and can be cheaply obtained!

[@mrbreeze732]

Great fix...You are the man.... I want to get a generator like yours could you recommend one? I have a HP 8656 R/F generator but I don't think it will do it.

[@JordanPier]

I use an old leader LAG-120a. Works great after replacing a few caps and cleaning the switches

[@brianfletcher9774]

Jordan, I was beginning to think I was loosing my mind...but you did cut in the phono section of the amp twice in this video. Did you do that on purpose ? Lol

[@XtremeKremaTor]

Well done again. Did you manage to fix the front input indicator? Was it lcd not working?

[@JordanPier]

I never got to figuring out why the display was not lit. Think it was an lcd

[@lurkersmith810]

@@JordanPier I believe there is a small incandescent lamp back light soldered in there, behind the LCD. Mine went out in the 80s after only a few years, and I never bothered replacing it because if I recall, it only told you what the selector knobs told you anyway. Now mine is buried away because I got spoiled by remote controls. Back then, it was cool having the LCD readout!

[@fredfabris7187]

At 13:40 there was a comment that if the load is removed and the distortion stays the same the issue is pre-driver..... if the distortion goes away it is a problem with the drivers or output devices right? Thanks! Helpful stuff!!

[@JordanPier]

Not true of all designs but true of this Denon and some others. It's a good troubleshooting technique to remember

[@fredfabris7187]

Jordan Pier thanks for the reply..... I will definitely add that to my bag of tricks.😎

[@moodyga40]

great video this is what i do for a job

[@ztechrepairs]

Subscribed. Great info. Keep up the great videos

[@waltschannel7465]

Good teaching on how to properly evaluate a solid state thingamabob. Maybe that thing survived Katrina? Barn find cars are one thing, but a barn find amp? 😂

[@daleburrell6273]

10:35...well, if ya don't LIKE it- ya don't have to EAT it!!

[@darikdatta]

Two phono inputs. Two tape inputs. One lonely aux input.

[@redstrat1234]

That was great

[@neverknowit11]

Gee what happened to this Amplifier?

[@MrRadioGypsy]

Hey; my work bench is covered with a bunch of crap - too . . .

[@brianfoley4519]

looks like the cat drained a kidney...

[@scottjohnson921]

from 34 minute to 36.5 minutes your video repeats you working on the phono section.

[@JordanPier]

Doesn't surprise me. This was just before my channel got booted for no reason. After it was restored there were many videos that were glitched. Some even got copyright violations where none had occurred before.