AudioAvarice
Super Member
I'm sure you don't need to be told, but check for cracked solder joints, and pay close attention to resistors in the power supply, had one go bad in mine, resulting in it going into protection after it warmed up.
Let's See Your Great JVC Gear!
- Thread starter GD70
- Start date
Appreciate the heads up. I’ll have to see if these amps use fusible resistors. If so, all of them are being replaced. Standard practice for my restorations is a complete reflow and deflux of all circuit boards. This way I’ll have a clean slate to work off of with respect to the solder side. No need to spend an eternity troubleshooting a micro crack on a trace hidden deep in the belly of beast. It’ll be a while before I’m able to start working on gear again, but between these M-L10’s and my Sony TA-N900’s, plus a few other pieces from some friends of mine, I definitely have my work cut out for me
AudioAvarice
Super Member
Oh nice you got a pair of TA-N900's too? You have fine taste in Japanese amps, I've got a TA-N902 from the same line up, great era for Sony imo.
Yep! I actually have three of them. Two US spec units and one from the EU. The EU unit I bought for parts if needed. Lots of unobtainium under the hood, so I’d rather be safe than sorry. These things are gonna be interesting to dig into to say the least
The N902 is on my list!
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AudioAvarice
Super Member
Yeah the Sony '900' was pretty popular in Europe, particularly Germany, rare as hens teeth here in the UK though. Looks nicely laid out inside, is the PSU potted in them? I forget.
The Victor (Japan only) M-7070 monoblocs use a similar idea with a different implementation in regards to the power supply, but have a more 70's look, but with LED level meters.
The Victor (Japan only) M-7070 monoblocs use a similar idea with a different implementation in regards to the power supply, but have a more 70's look, but with LED level meters.
The PLPS (SMPS) power supply in the 900 is about as good as I’ve seen Sony implement them, especially when compared to units like the N86. The circuit board quality is much improved, too. It is not potted, but it’s still sealed. Luckily, Sony had the efficiency down to a science and they don’t appear to run terribly hot, judging by the condition of the boards and components in all three of my N900’s. I’ll attach a few photos here:
At the end of the day though they still crammed 10lbs of stuff in a 5lb bag if you know what I mean. It’s probably going to be a fair nightmare to service but I think I’m up for it.
I’ve seen the M-7070 before. Very cool amplifiers. I’ve heard those that have them like them quite a bit!
AudioAvarice
Super Member
It looks well laid out despite all the space being used, pretty amazing really, especially considering it's specs, I still prefer lots of smaller boards rather than one large one tbh, much less prone to cracked solder joints, and flex.
I still haven't listened to the M-7070's not sure I want to risk the unobtainable JVC made MOSFETs, still looking for a service manual, so I can do a proper recap/service.
I still haven't listened to the M-7070's not sure I want to risk the unobtainable JVC made MOSFETs, still looking for a service manual, so I can do a proper recap/service.
Snuck
Active Member
You are totally right about the VC-5022 chip I am affraid I spoke too fast.
Regarding the secrecy, all brands invested millions and millions into gear and researches, so they didn't really want to be copied. There was a spirit of both cooperation between them, and yet of secrecy as well. I readed some interviews from one of the former head of Mitsubishi speaker design and it was quite wild the techs they used right in the 50s for their speakers, and the investment they did later, as well as Hitachi and so on. Few brands started it, all others followed not to be left behind.
To post some Sony on a Victor post, is a bit trolling considering the big splat and war they had on going, yet, Victor recognized it was a Sony chip invention that allowed them to start the K2 inventions (while Sony never recognized all the help they forced Victor to do for Betamax for instance). x)
Regarding the secrecy, all brands invested millions and millions into gear and researches, so they didn't really want to be copied. There was a spirit of both cooperation between them, and yet of secrecy as well. I readed some interviews from one of the former head of Mitsubishi speaker design and it was quite wild the techs they used right in the 50s for their speakers, and the investment they did later, as well as Hitachi and so on. Few brands started it, all others followed not to be left behind.
To post some Sony on a Victor post, is a bit trolling considering the big splat and war they had on going, yet, Victor recognized it was a Sony chip invention that allowed them to start the K2 inventions (while Sony never recognized all the help they forced Victor to do for Betamax for instance). x)
stueym
Active Member
I've just scored a R-S77 on the auction site for the princely sum of £35 delivered - described as not working, no sound so I took a punt. Not much invested if it's shot to hell, and perhaps if it needs a little work it would be worth it.
So I just took delivery and plugged in some speakers and my MiniDisc recorder into the AUX and.... playing through the right channel! Well. This is better than the description! I wiggled the volume slider a bit and the left channel comes in too! She lives! Haven't done any cleaning or maintenance yet. The SEA works and so far no noise either. I am chuffed! This is my first top of the line item I've owned 
So I just took delivery and plugged in some speakers and my MiniDisc recorder into the AUX and.... playing through the right channel! Well. This is better than the description! I wiggled the volume slider a bit and the left channel comes in too! She lives! Haven't done any cleaning or maintenance yet. The SEA works and so far no noise either. I am chuffed! This is my first top of the line item I've owned
Okke 70s
Super Member
That is a darn pretty machine, isn't it? And those Super-A's always sound great. There is (or was) one exactly like it for sale near me. I shall resist the temptation!
It was mentioned somewhere that they are not easy to work on. Probability the same construction as with the integrated's where you have to take the amp out, heatsink and all, just to get to the bottom.
I have seen some seriously bad main caps on these series, you might want to check that out. But darn does it look appealing..
It was mentioned somewhere that they are not easy to work on. Probability the same construction as with the integrated's where you have to take the amp out, heatsink and all, just to get to the bottom.
I have seen some seriously bad main caps on these series, you might want to check that out. But darn does it look appealing..
stueym
Active Member
Thanks! I love the look. It sounds so wonderfully clean now I've gone through the front panel switches and controls with servisol. No static and the volume, balance and SEA controls are all smooth and quiet now. I can't believe I got it for such a good price. Looks a little nicer now it's cleaned up:
GD70
Lunatic Member
The R-S77 is a great receiver, and under the radar. I’ve owned mine since new, 1980. Extremely well built. Sounds incredible. U.S. version has the wood faux wood cheeks. They run hot. Mine has since new.
Glad you have yours working properly!
Cheers, Glenn
stueym
Active Member
Hey Glen. Glad yours is still going strong! Mine has two issues that I've found since I got it. First is the 5th radio preset button doesn't work - it can live with that, but may get it sorted out as I think a service is required due to the 2nd issue:
After the unit has been on for a period of around 5-15 minutes, there's a static crack from the speakers and the sound cuts out for about 2 seconds, then returns. This only happens once, but has happened pretty much each time I turn the unit on to play something. Happens on any input as far as I can tell. The unit will then play perfectly for hours at a time. Anyone have an idea what this might be? Perhaps a bad capacitor, or the speaker relay? I'd like to pinpoint this issue if anyone has experience of this kind of issue before I take it to someone to service it.
Snuck
Active Member
A full service shouldn't be too complicated nor expensive on this model, it deserves it. Those apparels starts to be half a century now. When they were 20-30 years old, they still had years to go but now, they start to need total care. Still impressive regarding the build quality.
stueym
Active Member
This weekend I finally acquired a working KD-D4 cassette deck. I've been listing after this for a couple of years, had a couple of supposedly working ones which turn out to need more work than I can achieve, but this one came alongside a L-A31 turntable which I like better than my QL-FX5, and a fully working R-S33L receiver, all for £50. Here's the deck in my system:
Wally1955
Well-Known Member
Aloha
Longtime not visit the Victor/JVC AK Forum
luckily find one of this super rare VIctor MST-1000 fully functional and yes it's a gorgeous
Vintage Amp in exceptional good condition
for few Euros the ugly part of the deal the high shipping costs to Germany
Well the Amp is worth keep in my home and after first testing all I can say it's getting better after warm up
Cheers happy listening
massive build quality
all untouched and multi voltage
100/110-220/240V that's big advantage
Longtime not visit the Victor/JVC AK Forum
luckily find one of this super rare VIctor MST-1000 fully functional and yes it's a gorgeous
Vintage Amp in exceptional good condition
for few Euros the ugly part of the deal the high shipping costs to Germany
Well the Amp is worth keep in my home and after first testing all I can say it's getting better after warm up
Cheers happy listening
massive build quality
all untouched and multi voltage
100/110-220/240V that's big advantage