Hi all,

any exBBC engineers floating around?

I am trying to get some information about a BBC PPM drive card. It is the
one used to drive the Sifam dual needle unit (red and green needles AB/MS
etc.) It appears to use digital-based sampling to perform the
characteristics. It also has 4 small pots along the top and an 8 way DIP
switch bank. All the inputs are all on a 25 way D type connector , it runs
of 24 volts and it also has a small daughter board with a couple of bridging
transformers that has the BBC logo on it. It doesn't appears to be the
Canford one.

Anyone have a clue - it works fine, but I want to find out more about the
other functions that it has.

Thanks and regards, Mike

In article ,
fredbloggstwo wrote:
any exBBC engineers floating around?

I am trying to get some information about a BBC PPM drive card. It is
the one used to drive the Sifam dual needle unit (red and green needles
AB/MS etc.)

Only left/right if red/green. M/S meters use white for the M and usually
yellow for the S.

It appears to use digital-based sampling to perform the
characteristics. It also has 4 small pots along the top and an 8 way
DIP switch bank. All the inputs are all on a 25 way D type connector ,
it runs of 24 volts and it also has a small daughter board with a couple
of bridging transformers that has the BBC logo on it. It doesn't
appears to be the Canford one.

Anyone have a clue - it works fine, but I want to find out more about
the other functions that it has.

There are no other functions of a PPM than to read levels and peaks to the
BBC spec.

And there are so many different drive boards which do this as to be very
difficult to give guidance.

But most decent ones will allow setting of zero, 2, 4, 6, 7, and full
scale.

--
*If you can read this, thank a teecher

Dave Plowman London SW
To e-mail, change noise into sound.

"Dave Plowman (News)" wrote in message
...
In article ,
fredbloggstwo wrote:
any exBBC engineers floating around?

I am trying to get some information about a BBC PPM drive card. It is
the one used to drive the Sifam dual needle unit (red and green needles
AB/MS etc.)

Only left/right if red/green. M/S meters use white for the M and usually
yellow for the S.

It appears to use digital-based sampling to perform the
characteristics. It also has 4 small pots along the top and an 8 way
DIP switch bank. All the inputs are all on a 25 way D type connector ,
it runs of 24 volts and it also has a small daughter board with a couple
of bridging transformers that has the BBC logo on it. It doesn't
appears to be the Canford one.

Anyone have a clue - it works fine, but I want to find out more about
the other functions that it has.

There are no other functions of a PPM than to read levels and peaks to the
BBC spec.

And there are so many different drive boards which do this as to be very
difficult to give guidance.

But most decent ones will allow setting of zero, 2, 4, 6, 7, and full
scale.


Dave,
That is why I asked if there were any ex BBC guys hanging in there. The
drive card is a BBC unit, not a Canford or other make.

Yes I know if reads levels and programme peaks that is why it is called a
Programme Peak Meter. The needles are Red and Green and the unit is ex BBC.
Are you reading this now. It also has a switch for reading AB or MS which
work - it may be able to do other things such as MS +20 - that is why I
asked the question.

Have a nice day

In article ,
fredbloggstwo wrote:
That is why I asked if there were any ex BBC guys hanging in there. The
drive card is a BBC unit, not a Canford or other make.

It should then have a marking on it something like ME12/10A or perhaps
AM20/3 on the PCB? All the BBC ones I've seen use Earnest Turner
movements, although I'm aware Sifam make a similar one. But there are
dozens of different types of drivers for different needs, and I've not got
any circuits for recent ones.

Yes I know if reads levels and programme peaks that is why it is called
a Programme Peak Meter. The needles are Red and Green and the unit is
ex BBC. Are you reading this now. It also has a switch for reading AB
or MS which work - it may be able to do other things such as MS +20 -
that is why I asked the question.

The +20 switch adds 20 dB of gain to the 'S' signal input, as this is
often too low to read accurately without.

Have a nice day

I am, thank you. Hope you are too.

--
*Geeks shall inherit the earth *

Dave Plowman London SW
To e-mail, change noise into sound.

wrote in message
...
On Fri, 13 May 2005 23:09:56 +0100, "fredbloggstwo"
wrote:

I am trying to get some information about a BBC PPM drive card. It is
the
one used to drive the Sifam dual needle unit (red and green needles AB/MS
etc.) It appears to use digital-based sampling to perform the
characteristics. It also has 4 small pots along the top and an 8 way DIP
switch bank. All the inputs are all on a 25 way D type connector , it
runs
of 24 volts and it also has a small daughter board with a couple of
bridging
transformers that has the BBC logo on it. It doesn't appears to be the
Canford one.



What you have there is an AM20/5 driver, made by Surrey electronics
inder the name PPM9. The front end is conventional but the input is
digitised in an A to D converter. The log law is controlled by a
microprocessor, using a look-up table.

Some relevant info:-

Power 24v DC @150mA max.

25 way D pinouts:-
1 A input +ve
2 A input -ve
3 A input screen
4 B input screen
5 B input +ve
6 B input -ve
7 B meter output -ve (link to pin 8)
8 B meter input
9 A meter output -ve (link to pin 10)
10 A meter input
11 n/c
12 n/c
13 24 volts +ve
14 Internal 0 volts
15 Separate unbalanced "M" input
16 Internal 0 volts
17 M/S switch (short to pin 16 for M/S operation)
18 Internal 0 volts
19 "S" sensitivity (short to pin 20 for normal, open for S+20dB)
20 "S" sensitivity
21 B remote meter output
22 A remote meter output
23 n/c
24 24 volts -ve
25 n/c

IMPORTANT - Do not connectthe internal 0 volts line to an external
ground as the power is floating. the input screen connections should
be used for the audio grounds.

Calibration adjustments:-

Viewed on rear, reading left to right.

DIP switches 8 to 1 are the set 6 level adjusts. The 4 trimmers along
the top are for Gain B, Zero B, Zero A and Gain A.

With no input signal, adjust the meter zeros. Apply 0dBu input and
adjust gain controls for PPM 4. Check law at all points. If there is a
small error above PPM 5 then adjust PPM 6 using the DIP switches.

Switch
number
6 5 4 A channel, left (Red, White)
3 2 1 B channel, right (Green, Yellow)

0 0 0 No correction
0 0 1 Increase deflection 1
0 1 0 Increase deflection 2
0 1 1 Increase deflection 3
1 1 1 No correction
1 0 1 Decrease deflection 1
1 1 0 Decrease deflection 2
1 1 1 Decrease deflection 3

The degree of adjustment is deliberately small

I think this covers all the basics and hope it has been of assistance.


Hi there,

Thanks for the thorough description and information - it is exactly what I
needed - Many thanks.

Kind regards, Mike

In article ,
fredbloggstwo wrote:
Thanks for the thorough description and information - it is exactly what
I needed - Many thanks.

So you knew it was an AM20/5 ?

WTF didn't you say so?

--
*Of course I'm against sin; I'm against anything that I'm too old to enjoy.

Dave Plowman London SW
To e-mail, change noise into sound.

"Dave Plowman (News)" wrote in message
...
In article ,
fredbloggstwo wrote:
Thanks for the thorough description and information - it is exactly what
I needed - Many thanks.

So you knew it was an AM20/5 ?

WTF didn't you say so?

--

Hi Dave,

No I didn't know if was an AM20/5 until it was pointed out to me - it was
not obvious and I am not used to the BBC markings on PCBs.

It was good and very helpful of the reply posting to let me know from the
description I gave and I now have the information I need.

No need to go into expletives.

Regards, Mike