Turtlerock Forum

Ok,

So I thought that this would be the best place to talk about this thing and just generally see if anyone here has any more info regarding anything to do with this piece.

I found this in the shop display of a local tip shop last year, where they appeared to have a haul from the radio transmission department of a local University, they also had tons of valves and other junk but this appeared to be the stand out to me. So I got it for the grand sum of $30 and instantly knew that it was some kind of audio valve gear by the "DECIBELS" in the main meter. The plan is to eventually send it to a tech and have it up and running as a valve preamp to use in my humble home studio.

It's made by an old Australian company called "Sydney Transmission Products" and as you can see from the pics is called an "A.P.O. T.M.S. No2 MARK 2".

I have searched everywhere on the net for more info on this unit and even finding references to the company are few and far between. I hope that someone here may know something about it like, when it was made, what exactly it does?, how many were made?, for what industry purpose were they made, radio?, and is it possible to use in a modern studio environment realistically?


Also very interested if Rick and Rob might have any comments regarding the construction of the unit and if they've seen one before. I think I'll be sending it to Proharmonic sometime this year to get it going again as it obviously needs a lot of work, so if anyone has schematics, that would be really, really helpful. I can tell from the inside that this is a beautifully constructed piece from yesteryear, shame to let it turn to junk.

enjoy the pics :)

never seen one before

first up, it looks like it needs a power supply. A good suitable PSU will cost around $500

hard to know what it does, seems there is gain there but is there enough for a preamp?

the meter is funky

Cool, thanks Rob, yeah there is signs of where the mains cable was as it's been cut from the outside, the tip shop guys do this to avoid people getting fried from old electronics stuff. But you can see where it goes in and where it's connected to a tagstrip and then to the valves (second-last pic in the left corner between the valves).

It's got gain controls everywhere on the front panel, it's crazy.

Yeah, the meter's huge ;)


Cheers.

that cable probably isn't for the mains input. Most of these old units had external supplies that delivered 6.3Vac and 300V DC

if this is the situation with this unit, then it will need an external supply built to suit it

rob wrote:that cable probably isn't for the mains input. Most of these old units had external supplies that delivered 6.3Vac and 300V DC

if this is the situation with this unit, then it will need an external supply built to suit it

hmm, not sure but the cord is very similar to a modern mains cable.

It has three similarly colour coded wires inside an 8mm sleve, can't quite remember but something like brown, black and green.

Anyway, no chance I'd wire it up like this, so I thinks at some point it's going to need to see you Rob, just needs a re-paint on the outside first ;)

APO stands for Australian Post Office. In the dim distant past the P.O. and Telstra were linked. Regards Norm

Norm,

Do you have any documentation to verify APO?



Once upon a time our mail and telephonic services were under the auspices of the PMG (Post Master General) department which was ultimately divided into departments for electronic and physical communications...........now, my memory may be failing but I think they were then and still are, known as, initially Telecom (now Telstra), and Australia Post............I have no recollection of there being a transitional organisation officially known as the Australian Post Office.

Norm is right, the 'APO' does indeed refer to the Australian Post Office. I believe this organisation worked under the Post-Master Generals department in R&D for telecommunications networks in Australia

http://www.austehc.unimelb.edu.au/tia/contents.html

You need to dig a little deeper than wikipedia!

Chris

So the unit is used for something to do with telecommunications installs or maintenance.

Given the handle I think you could assume that the unit is designed to be portable – this limits the options a little.

There are a series of jacks on the front which look (for example) like they might be able to accept a line from a switchboard or perhaps an exchange.

Components look 'serious' and the build quality looks high but I'd suggest the unit is not designed for audio recording purposes.

Then there's the reference to N.C.R. 10 dB gain on the front - this might be a clue to what the unit was purposed for?

Interesting puzzle, Richard.

Can you write out for us all of the front panel control labels - I can male out CAL with is clearly the meter calibration adjustment, and DECIBELS on one of the switched pots which seems to be a gain control.

The "NCR Gain 10db" seems to be a tag applied later. I'm wondering is it refers to the input transformer gain given position compared to the bak of the panel.

Decibels switched pot appears to run from -20 to +10 but with a further two detents where the marking on the case could have been worn off (+20, +30?).

This could be a coarse amplifier gain control (in which case the unit is some sort of amplifier with around 50dB of gain?) or that this sets the range of the meter.

Maybe someone more knowledgeable and experienced can chime in to correct some of these deductions?

Text_Edifice wrote:Maybe someone more knowledgeable and experienced can chime in to correct some of these deductions?

That's definately not me BTW.



However, I thought it was a transmission limiter seeing there is a "cal" for the meter to calibrate back to 0db. For gain reduction?

I'm probably very wrong.


Nice little find Richard. I feel like I'm on "Collectors" audio episode. :)

Wow, thanks for all the replies guys! So APO really does stand for Australian Post Office, ha cool.

Just away on holidays at the moment, so will get more info on thurs when I get back ;)

Ben Moore wrote:...Nice little find Richard. I feel like I'm on "Collectors" audio episode. :)

Yeah, when are they going to do an audio episode, about time they did I reckon.

Text_Edifice wrote:...Given the handle I think you could assume that the unit is designed to be portable – this limits the options a little...

Actually, this is the interesting bit, while it does have a leather handle on the top, the width of the front is actually 19 inches, just like a rack unit. However, there are no rack holes on the front but there are the normal 4 oval rack holes, but on the rear?!

chris p wrote:Interesting puzzle, Richard.
Can you write out for us all of the front panel control labels...

Will do, as soon as i get back home :)

ok i am back from holidays - and look what happens

it looks like the make up amp for the transmission phone line passive equaliser they made
i will try and remember where the equaliser is and post up a photo .

i have a fair idea what good looking useless junk is
this is good looking useless junk :)

i always assumed it was a post office thing

rick wrote:ok i am back from holidays - and look what happens

it looks like the make up amp for the transmission phone line passive equaliser they made
i will try and remember where the equaliser is and post up a photo .

i have a fair idea what good looking useless junk is
this is good looking useless junk :)

i always assumed it was a post office thing

Rick, I love how you've got to try and remember where all these things are. Damn your endless closet of fun toys! :)

pic's please.

Like I said in the other thread,

It is an Australian Post Office (A.P.O.)
Transmission Measurement Set (T.M.S.)

I don't own the passive eq but one of my collecter friends does I just need to remember which one!
There is a lot of stc stuff around of the same vintage ( early 50s ) which looks the same but better ( cause it's black)
My advice is polish it up a bit put it in your loungeroom and admire the effort people went to in days gone by for 10 db of makeup gain better still take a snazzy photo of it on your iPhone and post it up on the web
and post it up on the web and ask yourself the question about how far communications have come since that was built

never walked past a bakalite knob without given it a second look myself

Rick wrote:Better still take a snazzy photo of it on your iPhone and post it up on the web

And then see how many times it gets copied and appears elsewhere on the web!

rick wrote:i have a fair idea what good looking useless junk is

So you have met my ex girlfriend then....!

I think that this is a vu meter unit. It allows you to measyre the voltage unit on a given cable with a calibrated meter. Not sure what the usefulness of this is but I have one made by trimax and you can see similar ones on the old aussie gear website listed in the other posting.

I'm with rick good looking but useless in current situation. Build a LA2a clone or similar into the chassis and use the vu.

cheers
M

Well, thanks to everone who responded, looks like we've collectively found out what it is √√

otto ruiter wrote:Like I said in the other thread,

It is an Australian Post Office (A.P.O.)
Transmission Measurement Set (T.M.S.)

Oh sorry, thought you were joking, never seen anything look less likely than this to come from what is now Aus Post.

rick wrote:I don't own the passive eq but one of my collecter friends does I just need to remember which one!
There is a lot of stc stuff around of the same vintage ( early 50s ) which looks the same but better ( cause it's black)
My advice is polish it up a bit put it in your loungeroom and admire the effort people went to in days gone by for 10 db of makeup gain better still take a snazzy photo of it on your iPhone and post it up on the web
and post it up on the web and ask yourself the question about how far communications have come since that was built

never walked past a bakalite knob without given it a second look myself

Cheers Rick, damn so it basically is a piece of junk, I had ideas of being able to process my synths through this and get some sort of tubey tone with it, but I guess 10db just aint going to cut it.

Anyway, I would've thought it to be quite rare, the only other Sydney Transmission stuff I've seen is valve testers and the like, nothing audio.

mylesgm wrote:I think that this is a vu meter unit. It allows you to measyre the voltage unit on a given cable with a calibrated meter. Not sure what the usefulness of this is but I have one made by trimax and you can see similar ones on the old aussie gear website listed in the other posting.

I'm with rick good looking but useless in current situation. Build a LA2a clone or similar into the chassis and use the vu.

cheers
M

Thanks Myles, yeah well I was going to fix it up and see if it was useable but seems it's not worth it - another interesting but ultimately useless thing to sit around my place, oh well :)