Re: Info or schematics for BBC AM9, AM7, UN4/6, AM1/57 Modules anyone?

[MagnetoSound]

Hi Roddy,

I know this is a really ancient thread, but I also have some BBC AM9/6 mic amps and AM7/4 line receiving amps that I would like to find schemos for.

I'm (almost) a newbie here, and I wasn't sure whether to start a new topic on this, but having found this thread, I just wondered whether, if you ever got PDFs or photos together for the other guys that asked, could I possibly get copies?

I'd be pleased to discuss possible mods to these if anyone's interested, too - the AM9s are awfully sensitive at the front, I'm guessing it would be a simple matter to fix ...


Thanks,

Dan

 

[mrclunk]

i'm still looking for schems myself, so nice one for rejuvenating the thread.
I'd forgotten about it myself.
our modules are slowly composting along with the 2inch...

 

[MagnetoSound]

the AM9s are awfully sensitive at the front, I'm guessing it would be a simple matter to fix ...

In fact, I don't think they are. (I was using a pretty hot mic to test them, and up very close, so not exactly a fair test.)

mrclunk, can I take it you haven't managed to get yours going? I could give you the pinout if it would help.

 

[rodabod]

Guys, hold up. Let me get the sheets out.

 

[mrclunk]

magneto, no i havent powered them up. They're quite dirty, little corroded. i wouldn't dare plugging the psu's in with out cleaning/recapping first. THink they've been sat in a garden shed for a few years before we got them.
The pin outs would be very handy, thanks.

and roddy if you do have the sheets  ;D

 

[rodabod]

I know this is a really ancient thread, but I also have some BBC AM9/6 mic amps and AM7/4 line receiving amps that I would like to find schemos for.

Hi Dan,

I have data for the AM9/5 and AM9/8, but sadly not the AM9/6 specifically. What I have may be helpful though.

I do have the AM7/4 sheets.

Roddy

 

[clintrubber]

Hi Roddy,

If these are related & if already in electr. form, yes please, let's have them.

Thanks,

  Peter

 

[rodabod]

Ok, I need to get my camera back off of who I loaned it to. Keep bugging me until I get it done!

 

[rodabod]

Still waiting on my camera. I'd use my phone, but the pictures are crap.

Bump in a week or so. (Sorry!)

 

[MagnetoSound]

Bimp!

 

[rodabod]

Right, I'll borrow a camera off someone else. It's a bit ironic. Why do I always trust people who I lend stuff to?

 

[clintrubber]

bmp 

 

[rodabod]

Ok, I've borrowed a DSLR and taken the shots. Let me host them after I get back from the pub this evening and then that should help you.

The "Power Supplier" units you have must be very early revisions I guess as I don't have details for them.

Roddy

 

[MagnetoSound]

That's great news! :thumbs and guinness:

The "Power Supplier" units you have must be very early revisions I guess as I don't have details for them.

Not sure what you mean about this - I have the PS2/49, like mrclunk. You said you had the sheet for it, no?

 

[rodabod]

Not sure what you mean about this - I have the PS2/49, like mrclunk. You said you had the sheet for it, no?

Oh balls. Yeah, wait until I get that camera again - hopefully tomorrow.

I'll be PMing you by the way.

Roddy

 

[MagnetoSound]

Right. With big thanks to Roddy we can now see the circuits (here).

As it turns out the AM9/5 does not normally have gain controls on the front panel, as I thought - but as an external option. The AM9/5 modules in the picture I posted above are the narrow modules directly below the jackfield.

Perhaps surprisingly though, I can confirm that the AM9/5 circuit is identical in every way to the AM9/6, even down to the component designations - so it's good news for those that have the AM9/6 - the AM9/6 is simply two channels of AM9/5, but with front-panel mounted attenuators!


Of course the pinouts of the modules are different, and the 'PL A' pin numbers in the AM9/5 schematic do not apply to the AM9/6.


The AM9/6 pinout is as follows for each of the two connectors:

  1 -
  2 -
  3 -
  4 - I/P SIGNAL GND
  5 - I/P + @ 600 ohm
  6 - I/P -
  7 - I/P + @ 60 ohm
  8 - I/P -
  9 - 24v  -ve
10 - 24v +ve GND
11 -
12 -
13 - O/P (unbal, 600 ohm)
14 - O/P SIGNAL GND
15 - CHASSIS GND

(Pins 6 & 8 are linked at the connector.)


Note that on the right-hand connector (when looking at the back of the module) for AMP. A, pin 1 is at the bottom. On the left-hand connector, for AMP. B, pin 1 is at the top.

For those of us with PN3/23F sub-frames, with only one female connector in the frame per module, it is entirely possible to remove the second connector from the module and move the wires across to the empty pins on connector 1, thereby making life considerably easier as you can now use both channels via one connector. (I haven't checked this for crosstalk yet, but as the inputs are balanced and floating I would expect this to be acceptable ... )

The transistors (original) in the AM9/6's that I have are 2G308 Germanium types, rather than the 'R2039' in the schematic (which I can't find reference to anywhere!). If you look at the AM7/4 circuit you can see that these can also sometimes be BCY70/71, so it would be interesting to hear from anyone that has silicon in theirs ...


HTH,

Dan

 

[mrclunk]

;D Nice one Roddy, thanks so much for the scans.

was just about to scrutinize them but looks like Dans done all the hardwork, thanks mate.

thanks again guys.


I'll have a look at mine in the morning and see what type of transistors are in there.

 

[mrclunk]

btw we have the 2G308 Germanium type transistors in ours.

 

[MagnetoSound]

Oh, cool ...

Have you got them going yet?

 

[mrclunk]

Haven't tried yet, too busy and have a mountain of other magic beans to hook up first!