BA-F1 restore

[Hyperion]

I have been entrusted with a really nice BA-F1 to restore for an AK member, I collected it last night. It is in at least a 9/10 condition overall, and appears un-molested inside apart from a replacement set of OnSemi output transistors for one channel. He is not expecting it to be finished until early next year - so I have plenty of time to make a really good job of the restore.

The restore
I'll probably post some before and after PCB pictures if there is interest, as this model doesn't seem that well documented / illustrated here on AK.

Any tips?
For those of you that have already tackled one of these I would be very interested in any tips you may have picked up regarding this model. I am also interested to know if anyone knows the whereabouts of a guaranteed one channel set of OP transistors going spare anywhere, the originals in the other channel are NMC1012 // NMA1012. (The OnSemi replacements used are MJ15024 // MJ15025 which are fine really - but maybe originals are better).

Pre-amp?
The owner really wants to get a pre-amp for it, I have suggested he does everything he can to get the CA-F1 - the perfect pairing.

 

[Kale]

The most important upgrade is to change the way how bias transistor is mounted to the heat sink, in original way, the bias transistor is fixed over metal holder to the aluminum het sink, that way is not good because heat is traveling from aluminum heat sink over metal holder to bias transistor, so you should adopt that metal holder to fix bias transistor directly to aluminum heat sink, something like that


But careful, metal holder could be broken during adopting it on that way, so you should be very precise to do that at first time…

I have some better picture, but it is on my second computer, so I will show you later....

And not so important, but good to do... new ground connection of main capacitors like I did here

http://audiokarma.org/forums/index.php?threads/connection-of-the-main-capacitors-in-ba-f1.779894/

 

[Hyperion]

Thank you Kale, - I just (independently) found the thread you linked to above and have bookmarked it

Thanks for the tip about the bias transistor mounting.

I've just worked out what you did with the bias transistor - you turned it round the other way! - clever.

 

[ghamilton]

 

[cnyel1967]

 

[Hyperion]

Isn't anyone going to bring something to drink.

 

[leesonic]

I wish I had one of these to work on, even better if I could own one...

Lee.

 

[smurfer77]

John. I will follow with interest, although I have never had a BA-F1. I hope to get one to match my CA-F1 which I recently acquired.

Regarding the preamp, I can speak highly of the CA-F1 already. I sounds great with anything I pair it with... slightly mellow and bassy though even with tone defeat engage (but hey, my CA-F1 is stock so who knows...). I don't think a CA-2000/3000 would be bad either. Oh, I really like my Marantz Esotech SC-6... in fact I have two of them! Runs a bit warm and has some reliability issues but sounds great.

 

[Hyperion]

John. I will follow with interest, although I have never had a BA-F1. I hope to get one to match my CA-F1 which I recently acquired.

Regarding the preamp, I can speak highly of the CA-F1 already. I sounds great with anything I pair it with... slightly mellow and bassy though even with tone defeat engage (but hey, my CA-F1 is stock so who knows...). I don't think a CA-2000/3000 would be bad either. Oh, I really like my Marantz Esotech SC-6... in fact I have two of them! Runs a bit warm and has some reliability issues but sounds great.

Thank you - the owner is following this thread so that information will be music to his ears.

 

[skippy124]

Hi John,

Watching with interest. I could link my 2012 BA-F1 restore thread but Photobucket has all but made the thread useless.....

Some info from that thread -

- I used 2SA1116/2SC2607 pairs to replace the outputs one channel that had failed (these are the recommended sub for the NMA/NMC - hard to get but they do pop up now and then

- 4 fuse resistors on the power supply board

- the foam seals around the meter needed replacing

I am intending to look at the bias transistor mounting, and that grounding mod is a piece of art!!

They do sound pretty damn good once up and running, and the CA-F1 pairs up very nicely.

Cheers

John

 

[ManyMoonsAudio]

Bring a drink? Wanna make it cool? Just hope it is all original and not blown up. Then all you really need to do is recap it, and take care of the black caps of death.

The Kale bias upgrade is a good idea. Not something I have done personally, but do see the merits of "quicker" recovery here.

This amp is a technical marvel to experience on test equipment. One of the most perfect "mirror's" of a square wave I have ever seen from any amp, ever.

Talk to Kale and get those 2608/1117 outputs to replace whatever is blown up, then holler at me for the best replacement driver transistors if you need them.

 

[ManyMoonsAudio]

John. I will follow with interest, although I have never had a BA-F1. I hope to get one to match my CA-F1 which I recently acquired.

Regarding the preamp, I can speak highly of the CA-F1 already. I sounds great with anything I pair it with... slightly mellow and bassy though even with tone defeat engage (but hey, my CA-F1 is stock so who knows...). I don't think a CA-2000/3000 would be bad either. Oh, I really like my Marantz Esotech SC-6... in fact I have two of them! Runs a bit warm and has some reliability issues but sounds great.

You right smurf. They run parts of this preamp pretty hot, but boy does it sound fantastic when up to snuff. I have never been able to beat it in the preamp category. LOVE mine. The difference between one used up and one restored properly is a very drastic difference.

 

[Kale]

As I said, now I will show you what metal holder you should adopt to make a good mechanical contact BIAS transistor to aluminum heat-sink…


That grey glue is some liquid metal glue, just to make a good pressure body of BIAS transistor to heatsink…
And the result is

 

[Kale]

CA-F1 is specific preamp unit, as you already seen it does not have ventilation holes, so that should be because of proper functioning of preamp section (it is not design mistake of Sansui engineers!) Only upgrade what I did on that nice preamp unit is to change four TO92L transistors with very high heat dissipation (really I dont remember right now which they are) with very good Toshiba TO91L 2sc2655Y/2sa1020Y

 

[Hyperion]

Some Pictures

View of chassis underside.


Driver board - Left


Driver Board - Right


PSU Board.


Chassis Top Side (including speaker relays, protection circuit and meter drive board)


More to come when I start work on this beauty.

 

[Karl vd Berg]

@skippy124 , there's a link where someone shows how to recover dead Photobucket pics in the thread... can't remember which thread now. I hope I find that thread info...

 

[Overundr1]

Looks like those driver boards get toasty toasty (or had a not so nice over current episode in the past)

 

[Hyperion]

Yes, the right channel driver board has had several components changed, reasonable to suppose this happened when that channel's OP transistors were damaged.

The L&R driver boards and the PSU board all look like they have been pretty hot in the past, having darker areas on the PCB's where they have been discoloured by heat.

After some checks I'll probably power it on today (via a DBT of course), and see what we've got.

 

[Hyperion]

I powered it on for the first time today, via a DBT - and it was a good job I did, because I got a dim bulb but brightening rapidly in jerky stages - causing me to power off very quickly.

I traced it to the left channel, and quite quickly found a fairly steady ~10Ω showing from the positive main rail supply to ground, a few connectors pulled off, and one cut wire later (- for fault finding purposes), I find it! The collector of one of the original OP transistors was showing that 10Ω to ground reading. So I remove it and test it, expecting the worst - but no - it's fine, then I am wondering about this black gunk around one of the transistor mounting screw holes? I found the transistor case must have been shorted to the heatsink at the screw hole! I can see a burr on the heasink (lost anodising) and this black gunk in the hole, on the screw, insulator, and on the transistor case where I find signs of arcing and the bare copper of the transistor case showing.

So it looks like the OP transistors may be OK - I'll remove them and test, then remount them after some careful dressing of the transistor case with a fine rat-tail file, and a close inspection of the rest of that assembly.

In my travels finding this fault I found evidence of ad-hoc component additions under the left driver board, and some bad soldering, I am now on the alert for any more tomfoolery.

The good news is that the amplifier as a whole (now minus the short) powers up ok, with a satisfying 'ping' from the speaker relay.

 

[Robisme]

Nice find.

Sometime working on gear after others makes the job twice as difficult.

Looks like a lot of heat discoloring in there.

Rob