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 Valve Radio Public Address Systems
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 Return to top of page · Post #: 1 · Written at 10:39:03 AM on 10 April 2015.
Pa Man's Gravatar
 Location: Golden Grove, SA
 Member since 10 April 2015
 Member #: 1726
 Postcount: 149

HI, I am new to this forum.
I have a small collection of radios radiograms and PA amplifiers and I was wondering,
if anyone out there has an old Valve system that would have come out of schools , hospitals etc
They usually have a turntable, Radio (for ABC schools programs) and of course an Amplifier.
Or in a Hospitals systems case several radios which were fed to patient panels.
I have been looking for one for a while but would love to see what some of the people on this
forum might have in there collections.
I have a Bland Radio system (dual 6CA7 with fixed Bias) I just got with a turntable which I think came
out of a community hall.

Josh


 
 Return to top of page · Post #: 2 · Written at 5:45:48 PM on 10 April 2015.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 6761

Welcome to the forum.

Or in a Hospitals systems case several radios which were fed to patient panels.

Brad has just the thing. See this thread:

https://vintage-radio.com.au/default.asp?f=1&th=578


 
 Return to top of page · Post #: 3 · Written at 6:16:22 PM on 10 April 2015.
Brad's avatar
 Administrator
 Location: Naremburn, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 7395

It is a rare find these days. I would imagine that most hospitals would have ditched their valve piped music systems by now. There may be one or two in the bush that have retained theirs but they certainly would not be in service now. Modern digital MATV systems that include FTA channels, some of the Pay channels and radio channels as well are usually distributed through the nurse-call system now so you get one handset that does everything.

I grabbed that STC unit as it was being gently filed in a skip bin. The hospital I worked at at the time, namely Royal Ryde Rehabilitation Hospital, was going through their accreditation process and this involves, amongst other things, maintaining a clean and safe workplace, so all the junk they had jammed in store rooms at the time went to the tip. I was just in the nick of time to save this system from a similar fate.

Down the track I ran this unit in my garage whilst I was working in there. It pretty much ran all day, every day on unit number two, the middle one. Even back then in the mid 1990s the top and bottom units required restoration and these days the whole unit requires it. One day I will strip it bare and repaint the rack and restore each chassis to as-new. A major project that is likely to take some weeks when the work finally starts.


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A valve a day keeps the transistor away...

 
 Return to top of page · Post #: 4 · Written at 6:38:30 PM on 10 April 2015.
Pa Man's Gravatar
 Location: Golden Grove, SA
 Member since 10 April 2015
 Member #: 1726
 Postcount: 149

Love it Brad,
Am thinking the same thing, country may be the only place left, that's where I found the Bland Radio unit
I did wind up with a couple of the wedge shape school speakers one of which is in the process of being restored the other a bit beyond it BUT they did have the original Operatic badges on them.
I did come across a Philips unit 25+ years ago but at that point if I had bought that home I probably
would ave been made to live in it!! ( thinking these days it may have been worth it)
Just love the old valve equipment.

Josh


 
 Return to top of page · Post #: 5 · Written at 7:08:48 PM on 10 April 2015.
Brad's avatar
 Administrator
 Location: Naremburn, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 7395

I remember those wedge speakers. One in every classroom at my school, St Pat's Strathfield. They are probably long gone by now though. Been many years since I was there.


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A valve a day keeps the transistor away...

 
 Return to top of page · Post #: 6 · Written at 7:23:54 PM on 10 April 2015.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 6761

I have a Bland Radio system

Please email some photos to Brad.


 
 Return to top of page · Post #: 7 · Written at 7:23:56 PM on 10 April 2015.
Samt's Gravatar
 Location: Hobart, TAS
 Member since 6 May 2013
 Member #: 1337
 Postcount: 73

The local drive in at Hobart used Westrex valve amplifiers to drive the 500 or so speakers up until closure. Strait after closure the equipment was scrapped by Village to avoid anyone reopening the drive in and running in competition with their multiplex. There may be older theatres and drive in in country areas that still have their valve audio equipment.


 
 Return to top of page · Post #: 8 · Written at 7:29:40 PM on 10 April 2015.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 6761

wedge speakers

Picked up a bakelite AWA wall type 8 inch extension speaker last weekend.

Has a transformer on it. Coil appears to be 2 ohms.


 
 Return to top of page · Post #: 9 · Written at 6:16:57 PM on 11 April 2015.
Pa Man's Gravatar
 Location: Golden Grove, SA
 Member since 10 April 2015
 Member #: 1726
 Postcount: 149

Unfortunately there weren't a lot of regional drive ins in Adelaide and most folded a long time ago
even in Adelaide itself we have had only the one drive in for the last 20+ years.
Have seen a few of the AWA bakelite extension speakers, have got a couple of the Philips Metal versions, all the public schools here had the timber wedge shaped ones as I reckon they were pretty cheap to manufacture and pretty hardy being mostly ply.
Driving around quite a few schools still have the old horn speaker that had an 8" speaker inside still hanging on their buildings
I think a lot of different impedance wound up in extension speaker have seen everything fom 2 to 32 ohms , I reckon it was what ever they had on hand sometimes as with a 100v transformer they could match anything.

I will send some photos tomorrow afternoon.

Josh


 
 Return to top of page · Post #: 10 · Written at 7:12:27 PM on 11 April 2015.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 6761

with a 100v transformer they could match anything.

Yes, I'm familiar with 100 volt and 70 volt systems. My jukebox supports a 70 volt speaker system.

The transformer on the AWA speaker isn't tapped -- looks like a normal output transformer. Not sure how it was used. Will need to work out the transformer's winding ratio.

Driving around quite a few schools still have the old horn speaker that had an 8" speaker inside still hanging on their buildings

Haven't see many of those anymore here in Sydney.


 
 Return to top of page · Post #: 11 · Written at 7:34:03 PM on 11 April 2015.
Brad's avatar
 Administrator
 Location: Naremburn, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 7395

Driving around quite a few schools still have the old horn speaker that had an 8" speaker inside still hanging on their buildings

Do you mean the super large horns that look like those on a tuba?

We had two or three of those around the school I went to and the electronic class bell was played over those plus the wedge speakers in the corner of each classroom above the teacher's desks. These were in addition to the more traditional fire bells that were located in the play areas.

These speakers also broadcast announcements from the 2nd Assistant to the Headmaster after first period, the prayers at midday and fire drill three times per year (once a term back in the three term days).

I can't find a photo but here's a video of someone testing one in their bedroom.

https://www.youtube.com/watch?v=x_RkR0CQ5ec


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A valve a day keeps the transistor away...

 
 Return to top of page · Post #: 12 · Written at 7:39:41 PM on 11 April 2015.
Pa Man's Gravatar
 Location: Golden Grove, SA
 Member since 10 April 2015
 Member #: 1726
 Postcount: 149

Quite a few weren't tapped they were fixed and had a pot to alter the level. I have quite a few of them with wide variety of in and out impedances like 3.5/600 ohms 15/2500 ohms.
Had some old Philips column speakers the transformer just matched the speakers power of 20 watts so were just 500ohm
An impedance meter is an invaluable tool to have if the markings have come off the transformer and speaker

Brad, Those exactly, although they didnt pipe the bell, and I cant remember to many announcements just the weekly ones for the whole school in the quadrangle.And the "Lets Have Music" program from ABC radio

Josh


 
 Return to top of page · Post #: 13 · Written at 7:53:30 PM on 11 April 2015.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 5389

There were a lot of "Australia Sound" one's in schools many were based on the switching valve 6CM5 in push pull & Philips was about the only one that listed the valve data for push pull.

I have a Philips one and a nasty piece of work that is for the uneducated. push pull bias (40v) and bias for the add on tuner are provided by a separate winding. There is around 315V on the PP plates.

I would suggest that the transformer is good for 400V . 500mA. DC which is something the newbie should steer well clear of: That can kill.

Marc


 
 Return to top of page · Post #: 14 · Written at 8:35:56 PM on 11 April 2015.
Pa Man's Gravatar
 Location: Golden Grove, SA
 Member since 10 April 2015
 Member #: 1726
 Postcount: 149

The 6CA7s in the Bland have an 80v fixed bias and 450v on the pp plates.
I had a few of the Philips 6CM5 amps, a 30w with an add on preamp, a 60w which I actually used on a couple of PA jobs and a 100w.
Would love to get hold of one with the tuner! Missed out on one a little while back. still got brand new 6CM5s and quite a few spares including correct period input balancing transformers
My father actually installed a few when they where new and knows them backwards

Josh


 
 Return to top of page · Post #: 15 · Written at 9:17:19 PM on 11 April 2015.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 6761

An impedance meter is an invaluable tool to have if the markings have come off the transformer and speaker

I have such a meter, but it's not in my workshop yet -- must remember to put it in the car.

No pot in mine, but there's a position in the moulding to mount one.

That horn in the video sounds remarkably good.

Back in Grade 3 or so, at 9am after any announcements, we had to march into class to this:

https://www.youtube.com/watch?v=QuVYS4uw0as

... via one of those speakers.



 
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