This poor thing was going to be thrown in the bin (some will say they would have i know 😉 )-but i saw this as a real challenge as its realy in a bad way.
so here we go this is it, and there is lots to do.
The cover will need to be stripped, repaired and recovered.
The amp, completly stripped down, a realy good clean,get rid of all the rust, reacap
Im going to have to strip this right back to bare bones.
Looking at the set up it might even lend itself to a simpler circuit and laterals??
so here we go this is it, and there is lots to do.
The cover will need to be stripped, repaired and recovered.
The amp, completly stripped down, a realy good clean,get rid of all the rust, reacap
Im going to have to strip this right back to bare bones.
Looking at the set up it might even lend itself to a simpler circuit and laterals??
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That is kind of grim looking and it is a shame about the rust. You have your work cut out with that one 😱
Unless you already started dismantling it, someone's been there before... and 'borrowed' both of the phono input pcbs
@Goldie99 ,you are right,I didn't notice,didn't get that far.oh well I'll just have to make up or adapt
Nah , keep that classic amp. One of the first P/N true complimentary output EF2's !
C611 - bootstrap and C605 DC , get some nice "muse" or panasonic NP @35V.
Main miller compensation (c609) = 47pF silver mica 300v.
Should have a real classic sound , like DIY "badger" , has a real 2 diode CCS , unlike some
other cheapo 70's OEM.
You could geek out on it.... R605-560R + D605/7 replaced with a standard 1.9Vf red led.
Of course , the 2 main PS caps = 8200u @ 50-63V would fit. And all the caps for the +/- 23V aux supplies.
Board most likely looks slightly burnt near those. Ahhh , they actually use EF pass semi's for the aux.
End up with a cool party amp that will belt out 50W for 20 more years. COOL METERS !!! (blue led's)...
I've seen eBay restored units like this (with blue meters) "Vintage" auction for 250-300$ !
OS
C611 - bootstrap and C605 DC , get some nice "muse" or panasonic NP @35V.
Main miller compensation (c609) = 47pF silver mica 300v.
Should have a real classic sound , like DIY "badger" , has a real 2 diode CCS , unlike some
other cheapo 70's OEM.
You could geek out on it.... R605-560R + D605/7 replaced with a standard 1.9Vf red led.
Of course , the 2 main PS caps = 8200u @ 50-63V would fit. And all the caps for the +/- 23V aux supplies.
Board most likely looks slightly burnt near those. Ahhh , they actually use EF pass semi's for the aux.
End up with a cool party amp that will belt out 50W for 20 more years. COOL METERS !!! (blue led's)...
I've seen eBay restored units like this (with blue meters) "Vintage" auction for 250-300$ !
OS
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Phono stages aren't really my thing but it should be do-able to add a simple opamp based one from eBay or another amp. Essentially you have only supplies, in, outs and grounds to deal with. Providing it physically fits it should be possible to hook it up.
Or, if you're looking to keep originality, you could always try to find a 'volunteer' to put the small phono pcb into Kicad, and get a few made (typically ca. £5-6 for 5X pcb that size at JLCPCB, including P&P). There's nothing special on that pcb, and all the info needed is in the manual & amp.
any idea who i could ask? im affraid i dont realy know people in the industry on here
If you don't have any application for phono, then omit it. Try to make the amp working first
I am not familiar with led implementations - what benefit would that change bring along?
Kicad is a fairly straightforward pcb design package, used by a lot of people not just professionals, I've used it myself but I'm certainly no expert.
I'm loathe to 'volunteer' anyone else, but maybe someone will step up and help you out. I'll pm you some more info anyway.
LED CCS (3) would cancel tempco better than double diode CCS #2. The best CCS is transistor - transistor CCS #4 (tempco and regulation).
OS
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How much effort do you plan to put into the wood part of this unit? It is more than tempting just to start over.
A NAD 3030 does not produce a single watt, not a single tone cleanly. What do you want to do with 10 or more dirty and distorted sounding "watts"? This is not an audio circuit: a complementary transistors half wave non symmetric push pull. No audio circuit!
You can't save some:
The BD139, BD140 are all audio unsuitable (except for a few lucky batches that are suitable for a special SE due to their unique sound). I recommend the BD441, BD442 basically because they are very charge stable and sound very clean and genuine. You can also use them as power transistors, they are very tough and distort very late.
Of course you have to think about your loudspeakers and sources and room and set-up: just improve and then it will be fine, it's not.
When building an active CS, the sound of the transistor (and diode) is essential. The vast majority are unsuitable for audio. It is an artificial, technical sound, often cloudy, curtained, that is often introduced.
Your ear will tell you what is suitable for audio and what is not: diy audio;-)
You can't save some:
- remove the bootstrap cap,
- C615 as cap > 100uF, > 30 VAC,
- no power transistors in TO-3: use TO-220 (sufficient here), the most sound much better than the most big ones (unless you have some rumbling, booming, multi-way wooden boxes to drive;-),
- R609, D601, C625 gone,
- R629 gone,
- R547, C531, C533, R549 gone.
- the wire-sand-ceramic emitter power resistors replace by any film resistors (TO-220 or TO126)
The BD139, BD140 are all audio unsuitable (except for a few lucky batches that are suitable for a special SE due to their unique sound). I recommend the BD441, BD442 basically because they are very charge stable and sound very clean and genuine. You can also use them as power transistors, they are very tough and distort very late.
Of course you have to think about your loudspeakers and sources and room and set-up: just improve and then it will be fine, it's not.
When building an active CS, the sound of the transistor (and diode) is essential. The vast majority are unsuitable for audio. It is an artificial, technical sound, often cloudy, curtained, that is often introduced.
Your ear will tell you what is suitable for audio and what is not: diy audio;-)
And so the work beguins, starting with the external wooden cover, which is in a very poor state of repair.
It has been stripped of all the old vaneer, cleaned up,put back together, sanded and filled so there are no high points when i re-cover it.
The base plate had lost all of its sheradised finish, and it would cost quite a bit to get this redone.
I have to consider what the cost of refurbishment would be against what i would get back on the unit, as i wont be keeping it(i cant keep them all), so it has to be a bit of a compromise in places, but not all.
So the base plate was cleaned up and given a realy nice coat of a fine hammer finish in a greyish black.
The center ventilation grill was all bent up, so this has been straightened, cleaned up and resprayed-this now looks good.
The next step will be the amp itself,a complete strip down to chassis.
It has been stripped of all the old vaneer, cleaned up,put back together, sanded and filled so there are no high points when i re-cover it.
The base plate had lost all of its sheradised finish, and it would cost quite a bit to get this redone.
I have to consider what the cost of refurbishment would be against what i would get back on the unit, as i wont be keeping it(i cant keep them all), so it has to be a bit of a compromise in places, but not all.
So the base plate was cleaned up and given a realy nice coat of a fine hammer finish in a greyish black.
The center ventilation grill was all bent up, so this has been straightened, cleaned up and resprayed-this now looks good.
The next step will be the amp itself,a complete strip down to chassis.
