Pioneer A757 repair, break & repair again

[@mdzacharias]

Dirty controls and especially tarnished relay contacts can easily account for the variations of level and distortion you were seeing here, and they can be quite intermittent and capricious in nature.

[@lornespry]

Thanks very much for the comprehensive presentation. I own the domestic Japanese A-717 version. For years I used it as the AV amp on the family rig. And before that, I used it in my pet audio system until the PHONO section quit. I have been planning to replace all the capacitors and generally clean it up ... perhaps just to use the preamp section. If you do any further work on it, I'd be interested in any updates in regards to your opinion of the sound. From what you say here, the huge amount of work to refurbish the amp may not give me anything more than what I have already in my system - which quite frankly is very good. (Thanks again - I've subscribed to keep up-to-date.) (BTW: quiescent current/ DC-offset cannot be adjusted. I guess it's controlled by a chip??)

[@lucacavallini561]

hi, i have this amp, i have cd-direct switch that if you touch lost a channel righ or left, depending how i touch this, you think that i can resolve with spay cleaner? or i must open the switch to check inside?

[@WackyRacesable]

Hi Simon, I've got an issue with my loudness switch.. Any ideas where i can get a new switch from.........? I have the same 757 amp

[@RUfromthe40s]

i bought in 91 a A-717mkII and it sounds very good if using the tone controls ,but recentelly i was moving my system and one night i think i let hot milk fell into the volume system ,now just a part of the volume works and i use the monitor of a cassette deck to reduce the volume, but this volume system is diferent from the others i was used to ,is it an easy fix?in your opinion

[@SacreDro]

Any idea what the differences between this and the A-777 are?

[@friedyyy]

Hey, if got the a-656 mark II (same series little brother) and also got the problem of the dropping channel the previous owner of yours had. Can you maybe tell me how you fixed it?

[@abuhamidan3488]

Hi i have the same siries of this amp., but no sound, ialso the are are not the click sound ffrom the speaker selector relay and I found that the final transistkr output are -12 vdc and -18vdx... is it normal or any problem eith mine..... tbank u.

[@MichaelBeeny]

After watching this video, it's been on my mind for a while. Mostly concerning the odd frequency response. You would expect there to be a slightly bumpy response if measurements were via the pre amp due to tolerances within the tone control pots, which normally are only balanced within 2 dB. As you were in tone defeat I don't know!! An amplifier like that you would expect ruler flat may be 0.5dB down at 20hz and 20khz, but only down! I have never seen any quality amplifier with plus dB bumps in it. The only exceptions would be some class D stuff or amplifiers without feedback, even then they never go up and down and tend to be smooth variations. Could be a preamp fault! be interesting to do a power amp only test, even dare I suggest a test gear check? I am amazed you find the amplifier thin on the bass. It has such amazing low end power and current reserve. I think you will find it will deliver a solid 100+ watts at 10hz if my memory holds out. Was a long time ago!! I hope a follow up video solves the issue. Mike

[@RUfromthe40s]

the A-90D was the urushi version of this with already in/out digital signal and a bit more improved in look, also better selectors that they all become bad after some 15 years of use but i have a pioneer since 1974 and the selector is still working without any noise since day 1

[@redrobbosworkshop]

I have the ancestor to this, the 1979 SA9800. A beast of an amplifier with twin power supplies. It too was prone to dry joints and for much the same reason, Pioneer placing hot running regulated supply boards upside down beneath the main chassis. Not good engineering and a shame because it spoils otherwise fine units. They did the same in their larger receivers.

[@RUfromthe40s]

not even close ,worlds appart , the SA-9800 is far better and no matter what watts per channel they have it can cope with most of the speakers you throw at it .the A-757 ,this is for the year a good amplifier but never compare them ,also own a A-717MKII and it ´s good but not alf the dynamics and not more powerfull and i use tone controls and loudness in this type of integrated amplifiers, depending on the quality one uses or not tone controls

[@paulmontgomery2935]

Hi Simon, I hope you are well. I could use a bit of help. I have exactly the same amp with the voltage selector on the back. Unfortunately the bit that you would turn to select the voltage is missing. I would like to short the wires on the back of the switch to use it on 240v. I have downloaded the manual for the A757 but it doesn't say anything about the voltage selector. So basically I don't know which wires to short to mimic the switch being selected to 240v. can you help? kind regards Paul

[@RUfromthe40s]

never saw one with voltage switch

[@paulmontgomery2935]

@@RUfromthe40s I managed to sort it now. Just had to short out the correct terminals on the switch selector. I think this is the military version so the manual states. Best regards

[@rsa2hi]

Quick question sir, my amplifier started since some months to take longer to switch on, now takes more than half an hour to be ready to play. I think it can be the caps in the power supply module for ripple correction that are nok. Any idea? Are they available in the Markt?

[@SoddingaboutSi]

Leaky coupling caps in the power amp probably.

[@rsa2hi]

@@SoddingaboutSi after researching a bit more I'm strongly tending to the caps for the delay to the relais! Thank you!

[@moseskh8477]

What is the difference between Pioneer A757 & Pioneer A757 MK-II

[@Si1983h]

What ever happened to the Roksan Caspian amp you were looking at? I’ve owned a bit of Roksan kit in the past and was looking forward to the repair video on it.

[@SoddingaboutSi]

Its still in bits. No service data unfortunately. Did spend a day last year trying to fix it. But so far no luck,

[@Si1983h]

Simon Spiers that's a shame, they're nice sounding bits of kit when they're working. I take it Roksan aren't forthcoming with schematics and service manuals then? That can be a problem with British kit.

[@TSilva01]

That's a non-switch amp, one off the lasts... I think the non-switching feature and the idle current is controlled by this chip PA0016.

[@Simon_B]

What type of speaker connector fits inside the centre of speaker connection posts?

[@landskronatompa]

I have a A-777 that wont click when I turn it on. Just replaced the two speaker relays but no difference. Any advice?

[@SoddingaboutSi]

Output is in protection. Blown output transistor or driver most likely.

[@landskronatompa]

@@SoddingaboutSi it starts again now after cleaning everything and replacing the speaker relays, but it take an hour or so to get warm and startup. What parts other then relays does that?

[@RTI_MD]

Hi, I've recently gotten an A-717 (which is basically the same amp), on higher volumes (where I wouldn't usually ever go that high) I hear a hissing noise if I put my ear close to the twitter, and much more when I use the headphones connected to the amp. Should this be a concern?

[@SoddingaboutSi]

No not at all. Particularly on phono stage.

[@RTI_MD]

Thank you. Btw I have to agree regarding the bass, it's a bit lacking in this area. But it's a very "transparent" amp, well at least the A-717.

[@johnsweda2999]

Isn't it to prevent the phono stage turned off to prevent noise in the preamp? What about changing the op-amps and upgrading them what would be a excellence substitute? maybe changing some of the transistors for better quality less noise a good amplifier for an upgrade I would say.

[@SoddingaboutSi]

The op amps are proprietary Pioneer units. There are no cross references. What would be a better transistor? The sound quality is more likely to be the design. Transistors won't change the sound unless they are noisy.

[@johnsweda2999]

Simon Spiers so what do you suggest to make it sound better bring in better bass and say sweeter top end? can you do a spectrum analyser sweep to find out where it's lacking in its frequencies? What is the amperage consumption if you can up the amperage output word help. Does it have a snubber capacitor on the bridge rectifier????

[@luispereira344]

Hi sir, is normal high temperature without signal audio ou speakears off?

[@SoddingaboutSi]

Sorry for delay. Yes amp will run quite warm with no sound. That's normal.

[@ВладимирГерасимук-к7ц]

How does this amplifier sound in your sound .. and what is the difference between 717 777 and this? what do you say about yamaha ax 900 ??????

[@SoddingaboutSi]

I haven't heard those other amps. But this sounds harsh.

[@ВладимирГерасимук-к7ц]

What would you advise from the Japanese ????? what sounds good ??? can Yamaha a 2000a ???

[@SoddingaboutSi]

@@ВладимирГерасимук-к7цPioneer A400, Some of the Marantz amps.

[@ВладимирГерасимук-к7ц]

Pioneer A400 so this is a cheap amplifier .... is it really better to be 757 pioneers .... and what of the Marantse would you advise?

[@SoddingaboutSi]

@@ВладимирГерасимук-к7ц Pioneer A400.

[@gamerpaddy]

i hunted down a problem that didnt exist, i when i had "direct" turned off, no sound came out at all. after checking voltages, transistors, diodes and breaking my back several times i figured, there must be a jumper bridge between ADP2 In and Out L/R.... even tho its using alps potentiometers and switches, all of them scratch horribly on mine, i tought alps is proper stuff that lasts. all of them are hard to get and even harder to get to internally

[@SoddingaboutSi]

Welcome to the nightmare of dirty switches. I uploaded a similar video of a technics amp only working on one channel. I was sure it was a fractured track ir open resistor. Turned out to be a really gummed up switch.

[@twister1264]

Fantastic video

[@SoddingaboutSi]

Thanks. It's an impressive amp.

[@Duijnkiller]

What you think of opening a pioneer m90a ?

[@SoddingaboutSi]

If you confident, go for it.

[@craigdavidson2278]

Eye spy, with my little eye....a Roberts R707!

[@spencebarton2947]

Simon take a look at your oscilloscope at 18:26 through 18:32. I saw it on the earlier sweep as well. It could just be interaction between your camera and the oscilloscope display, but if I saw that 'scope display in my lab I'd be doing some more investigating. I use my phone as a scope camera all the time and haven't experienced that.

[@SoddingaboutSi]

ralph cramden This scope does that a lot. It's aliasing and can be quite confusing. The HP scope doesn't do that.

[@RUfromthe40s]

all reference series are in the internet as the MKII was released in the same year of the MKI but ,ot doesn´t make no sense and some people believe that ,i talked to a old pioneer oficial technician and he told kme to look on the first two numbers on the serial number which comes in the back ,this fo0r the ones who are interested to know a friend of mine was a pioneer dealer and i remenber when their componemnts came out but diferent years in diferent countries, in late 93 there were not those decks with the casing for the cassette in the midle, and in all european countries they came out in 91 ,here in 95

[@SastusBulbas1]

I foolishly took one of these apart to do a DIY power amp, mint, fully working, but never used it as it was so dull and bland sounding, I regret taking it apart, one of my more childish moments as a teenager. The later A-400 integrated was a far better sounding amplifier.

[@SoddingaboutSi]

Yep. Nasty sounding thing.

[@RUfromthe40s]

in 93 i bought a ES sony amplifier that had better spec.´s than this or the others 717, 767 & MKII and the not so loved 777 it had better measures and more power and bigger transformers also bigger capaciteurs but when looking to Ebay recentelly and in all Europe this sony es amplifiers were very weak only in Portugal and U.K. they had this configuration ,the others are like one small transformer and two capaciteurs, sony is not my go to nbrand due to it´s all components failures but the amplifiers from esprit series are really good, some say elevated standart but that only comes on a catalog cover and written on a av receiver not that good, but SONY always call it ESPRIT series

[@banksbrothersfishing3126]

Make a replace volume Button my son turned mine the wrong way and IT snapped 🤧 maybe u could help med fix IT👍😉

[@RUfromthe40s]

the 400 and the 300 apeared after the reference series

[@ksztyrix]

Which model was better/highier in line up - A-757 or A717?

[@spiritfreemike]

A757 of course ...

[@spiritfreemike]

@Gerrit nonetheless the A757 (theoretically) is higher in the line up.

[@Flymochairman1]

'Bi-monoral', two mono amps in one box, as opposed to 'stereo-integrated' amplifier in one box. Looking at the dates, you'll know that now.

[@ulisesmoran5551]

Hola amigo me podrías facilitar el diagrama para poder arreglar el mio

[@marinkusev7537]

Thank you

[@RUfromthe40s]

100 watts at 8 ohms r.m.s. not nominal power

[@pawe-xm3kh]

👍

[@georgegraham7365]

please l will like to bring my pioneer A717 AMP to you for service. let me know your contact . thanks

[@waltervalenzuela4472]

Eselente lástima que no explica en español

[@RUfromthe40s]

not a dual mono