Turtlerock Forum

Is anyone using the Transmission Products (Pty Ltd, Syndey) limiting amplifiers?

Any info appreciated. Can't find much info on 'em.

Cheers. Ev.

EvLoutonian wrote:Is anyone using the Transmission Products (Pty Ltd, Syndey) limiting amplifiers?

Any info appreciated. Can't find much info on 'em.

Is this a type 216 amplifier? If so there is some info here: http://www.retrovox.com.au/ABCsse.pdf

Uses radio circuitry to modulate the signal to 455 KHz (IF), does the limiting at this frequency, then demodulates to extract the audio.

David Crittle

Just picked up a 216 myself, but no documentation (yet) apart from David's retrovox source, though I'm hoping to find more as I trawl the old transmitter sites.
It's certainly an interesting device. Hopefully have it going soon

Found some info in a PMG Engineering Training Publication from 1970 entitled 'Audio and Video Equipment'. Nine types of equipment in use at sound and TV broadcasting stations at the time are covered.This was part of my apprentice technician curriculum.

It has the circuit for the limiter amplifier with voltages and waveforms, plus four pages of specs and circuit description. A radio engineer certainly designed this device! The audio input signal modulates a 455 kHz carrier (standard Intermediate Frequency used in radio), then the actual gain control/limiting uses a 6BA6 variable-mu pentode. Then it is demodulated, filtered and amplified.

My scanner is out of action at the moment, but I can make a photocopy of the relevant section for you.

With Many thanks to Rob Squire, I now have a full manual and schematics for the 216 Limiter that I have scanned and have in PDF format. If anyone wants a copy please PM me and send me your email to send PDFs to.

I'd like a copy .... seriously.
Nothing like trying to move some of my mountains of paperwork into the hard drive

Shall do Rob, but will have to wait 'til next week. Currently in Berri SA cutting over 5RM to a new building and have a very slow connection. scans are High Res and would take ages to post on email from here.It's good to have a few copies scattered around (For when I lose mine ) now back to the heat gun and Krone frame......

Hi,
I recently found two Transmission Products devices in my stepdads shed. One is older than the other and they both look round the 1950's mark. The later one is a 'A.P.O T.M.S No.2 Mark 2' and the older is a 'Meas Set A.P.O No.2'. I'm guessing these may have been used for testing phone lines in the field or testing radio equipment. There's no power transformer in either so I'm not sure of the voltages I'd need to fire them up. Most probably 6v or so for the heaters and 200-300v for the rest.

What I'm wondering is if any of you guys have come across these and if so do you have any schematics for these or similar models. I've tried trawling through pages on the net to find any info but there doesn't seem to be any.

I've attached some photos.

I have it in my head that these may be of some use in my studio. What, I don't know. Keen to get them running to find out!

Cheers,

Simon Russell

Maybe they'd be good talking points and/or door stops as is

Kurt wrote:Maybe they'd be good talking points and/or door stops as is

Or a cheap fireworks display... Who knows eh. They may be of use..

well all i have to say about them is take a good hard look at the turtlerock logo sometime
then look at these things
you will see where the vu meter came from

haha! Classic!
I knew that thing looked familiar, but hadn't put 2 and 2 together...

I think these are 'vu measuring sets' I've one or two of these and as they are the parts are useful the circuit not so. I think you'll find that you also need a powersupply to run these that is not in the case and therefore maybe you dont have it at all. I am some day going to build a valve comp inside the chassis with a few parts from the original circuit and the vu meter of course. I think I have a circuit diagram somewhere too.

Ha, cool I also have one of the TMS No2 MkII's aswell, thought I was the only one

Only difference is mine has a rotary switch in the top left, where yours seems to have a toggle switch, though there's evidence to suggest mine was modified with that. I actually had the exact same idea as you to somehow make it useable in the studio but with not much of an idea how. I posted here and we basically came to the conclusion that while they do look funky as hell, they are of little to no practical use in a studio application.

It looks like the TMS was a line gain amplifier, but without a schematic the power supply is the real sticking point, I just wouldn't want to go putting any random voltage through it - could be a nasty experience.

They're also slightly too wide to fit in a 19" rack, so all in all would need extensive mod's to the circuitry and case, to the point where it's be better to use it as parts than anything. But I cant bring myself to do it with mine.

I wonder if they have any value to radio/telecommunications museums of some kind as an example of what was used in the PMG dept. back in the day. In any case it's an interesting piece. Anyone know how rare they are?, I guess every City would've had a few at one stage, perhaps more? I suppose also a lot have been scrapped, it would be a shame to lose a piece of Australia's communications history in these units.

Here's my old thread;

http://www.turtlerockmastering.com/forums/viewtopic.php?f=1&t=3371

Thanks for the input guys,

I kinda knew these devices wouldn't really be of much use, but I guess you never know until you try. They certainly have an appealing look. Realistically, they have no power supply and the old caps would probably pop if the correct voltages were applied anyway so getting them properly running would be time consuming and expensive. I'm leaning towards using one of them as a case for an 1176 clone. I've made a few of them before and these cases are pretty much begging to be used in some way! Also some of the components (mainly the 600:600 audio transformers) may be useful.

I'd still be keen to check out any schematics anyone has..

Richard, I see you're from Launnie.. Interesting, my step dad's units came from Hobart.

Cheers.

Simon Russell

That's interesting, mine came from Hobart too. For sale along with a whole lot of old gear from the Radio Transmission dept. of the Uni I think, snagged a few cool looking tubes I have no use for too. They had a couple of wooden crates full of them, even NOS ones from the US military marked 1947, still in original cardboard box's with wood shavings in them.

rick wrote:well all i have to say about them is take a good hard look at the turtlerock logo sometime
then look at these things
you will see where the vu meter came from

Yeah i remember asking about your logo! I asked whether you did it in photoshop because it was flawless. You said you actually physically made it and then photographed it! Thats one way to do it! Actually that's the best way! A Quality Photograph to start with. (I think I laughed out loud on tne phone about how briiliant the idea was to simply make it physically)

I see a lot of customer designed logo's which are either:

Terrible
Woeful
Stuck in the 70's
Stuck in the 80's
Done by the daughter
Done using word
Done using publisher
Tacky
Did i say terrible?

I have to say the Turtlerock logo is elegantly simple, totally relevant and beautifully executed. The best customer designed logo ive seen.

I have seen a lot...

i just stuck i a big version up in my new entrance at the studio
i still find it hard to believe its all me

rick wrote:i just stuck i a big version up in my new entrance at the studio
i still find it hard to believe its all me

Sounds good. Be great to see when the studios all finished!

i am not sure they will ever be all finished
the space is too big and my wallet is too little
if i remember tonight or tommorrow night i will iphone a snapshot and let you see

see i really am building a studio late at night even the iphone was tired

I see old heavy stuff

yup

Going mono! ............great idea having the big VU meter up on the wall so you don't have to leave the desk to check levels to tape.

actually thats view from the kitchen and entranceway so i dont even have to bother going into the studios to see whats going on !

the machine is festival records ampex 351 - very historic machine it was in the powerhouse museuam for a time
- i bought it and restored it to do the johnny okeefe collection a while back ,I dont think i will ever use it again
even though its like new now - but what the hell you cannot chuck it out can you .?

my new corridors are full of those kinds of things in custom made alcoves lit up like they are actually worth something to somebody
-a mate said tonight the studios are not finished yet because the place is more like my huge woodworking project then a studio
arhh the truth .. its hard to hear sometimes