ADA B200s: Channel A issues

[Iperfungus]

And another thing I'm thinking is that, aside different values, pots could be one LOG (A) and one LINEAR (B)...depending from production's country...I will verify that with a tester.
This could also explain the slight differences among Channel A and B...

I've found that for European production A = linear and B = log, while for USA and Japan (or other eastern countries) A = log and B = linear...

This makes me laugh... 

[MarshallJMP]

No the standard is A=log and B=lin, this is always been like this both in EU and US

[Iperfungus]

Ok, here we go with some updated and pictures.

I opened it again and I found that:

1) channel A and B pots are both log pots but they have different values (also after cleaning and drying): A measures now 9.97K and B measures 8.7K...yes, they ARE different...  This "issue" has an easy workaround: set channel A level a little higher...in this way channels sounds very close and past halfway the slight difference tends to zero as soon as max level is reached.
I will change both pots with 10K log new ones (identical).

2) on/off switch has been replaced and it works...but look at its picture how they fixed from the inside... 
I will replace it...

3) IN and OUT jack connectors will be replaced as well (INs have broken plastic threads)

4) the tranny seems original and that low "hum" is just normal transformer "noise". If I remove bottom cover, this "hum" is very, very low...and it gest "a little worse" when I put the cover in place and screw it to the chassis...it just transmits tranny vibrations to the chassis...  I fixed this with some strips of adhesive paper tape between bottom cover and chassis edges and this made the trick: now I just can hear the normal tranny "hum" without any additional vibration! 
By the way, it looks the correct one:

http://adadepot.com/mods/ADA-B200S-schematics/ADA-B200S-transformer-220V-50hz.pdf

I post some pictures just to see if someone (MJMP???  ) can identify this unit and see if it's a kind of export item...
It looks like having the chassis of a US unit where they put a 220VAC transformer and a different fuse, removing the white socket (for what was it used on US models???) and replacing it with a black rubber stopper.

@MJMP: can you date this unit from its serial number? Are jack connectors pictures OK? Can you see them right?

By the way, aside from a couple of minor issues that are normal with such used items, this is a great SS power amp.
A very good companion for and a perfect match with the MP-1.
Dead silent even at max levels, reliable, punchy, warm, transparent, thick as a brick and powerful.
I like it with my 2x12 Blackstar cab and I love how it sounds even at very low volume in night time.

Thanks to rnolan and Dante for pushing me down the hill!!!  :banana-rock: :banana-rock: :banana-rock:
 

[Iperfungus]

Other pics...

[Iperfungus]

More pics...

[Iperfungus]

........last pics!!! 

[Iperfungus]

Take a pic of the tranny as well.

I will attempt to record the buzz/hum too...  :banana-jazz-smiley-emoticon:

Needed no more! 

[MarshallJMP]

looks all stock to me, and from what I can see on the tranny the date code seems to be 05/90, so it's a late 90's model.

Should you need those jacks I have them lying around.

[Iperfungus]

looks all stock to me, and from what I can see on the tranny the date code seems to be 05/90, so it's a late 90's model.

Should you need those jacks I have them lying around.

Thanks a lot MJMP!
Very good news then!

About those jacks...yes, I need 4 of them!
They are all the same, INs and OUTs...isn't it?
We can talk about this by email!
Thanks a lot again!

[rnolan]

It's good its a later model, ADA changed (improved) the B200s a little bit from the first model that I had. With new jacks and pots (and I'd also highly recommend a full re-flow), it will do you well for years to come  .

[Iperfungus]

It's good its a later model, ADA changed (improved) the B200s a little bit from the first model that I had. With new jacks and pots (and I'd also highly recommend a full re-flow), it will do you well for years to come  .

I had some fun with it until 10 minutes ago...