Welcome to Australia's only Vintage Radio and Television discussion forums. You are not logged in. Please log in below, apply for an account or retrieve your password.
Australian Vintage Radio Forums
  Home  ·  About Us  ·  Discussion Forums  ·  Glossary  ·  Outside Links  ·  Policies  ·  Services Directory  ·  Safety Warnings  ·  Tutorials

Tech Talk

Forum home - Go back to Tech talk

 Help with ASTOR radiogram
« Back · 1 · 2 · Next »
 Return to top of page · Post #: 1 · Written at 2:54:13 PM on 4 June 2016.
Scotty's Gravatar
 Location: Melbourne, VIC
 Member since 26 December 2010
 Member #: 794
 Postcount: 274

Hi Folks,

I have been repairing an Astor Radiogram - I cannot find a model number stamped anywhere on it and don't have a circuit diagram for it either.

The unit was working fine and as of today the AM radio no longer works, it picks up static but no stations. The static becomes louder as you progress down the dial.

I have no idea where to start looking to fix it and would appreciate any assistance and a digram if someone can assist.

Unit has dates of 1954 stamped on the chassis and 1955 on the cabinet. It has the power amplifier located at the bottom of the cabinet with valves 6V4 and 6AQ5 along with the audio output transformer.

The head unit (radio dial and controls etc) are at the top on the front of the player and is a pull open type.

Valves on the head unit are 6AV6, 6N8 and 6AN7.

Below is a URL with a pic of the same model that was advertised foe sale if that helps identify it.

http://www.gumtree.com.au/s-ad/ringwood-east/collectables/astor-radiogram-restored-working-includes-radio-record-player/1078516937

Hope to hear from someone.

Cheers
Scott


 
 Return to top of page · Post #: 2 · Written at 4:16:40 PM on 4 June 2016.
Kakadumh's Gravatar
 Location: Darlington, WA
 Member since 30 March 2016
 Member #: 1897
 Postcount: 130

That sort of behavior sounds much like the set I am dealing with right now when the oscillator simply stopped working. It all sounded very lively with plenty of static from when flouro lights start up & fridges etc cut out but no stations at all. In this instance it would work sometimes and then not at all.
Check the 6AN7 (mixer tube) by substituting a known good one & see how you go.

Lindsay


 
 Return to top of page · Post #: 3 · Written at 4:23:52 PM on 4 June 2016.
Scotty's Gravatar
 Location: Melbourne, VIC
 Member since 26 December 2010
 Member #: 794
 Postcount: 274

Thanks Lindsay, I tried that and it was pretty much the same. - Not sure where to go with it now.

Cheers
Scott


 
 Return to top of page · Post #: 4 · Written at 5:26:02 PM on 4 June 2016.
Robbbert's avatar
 Location: Sydney, NSW
 Member since 18 September 2015
 Member #: 1801
 Postcount: 1094

Check everything to do with the oscillator, especially old caps. Check the resistors there and the voltages on each pin of the 6AN7. Check that the tuning gang hasn't been shorted by some stray dust. There really isn't many parts, so it shouldn't take too long.


 
 Return to top of page · Post #: 5 · Written at 5:26:43 PM on 4 June 2016.
Kakadumh's Gravatar
 Location: Darlington, WA
 Member since 30 March 2016
 Member #: 1897
 Postcount: 130

Looks like you now really do need a circuit to check out the oscillator section around that mixer tube. Hopefully someone on the forum can dig one up for you to work from.

I have a photo of a similar type of circuit using the 6AN7 I will send it to Brad to upload to this page & also Email it to you...might be a start as the circuitry around the 6AN7 was very similar for most sets of that vintage. The unit looks very similar to one owned by one of my childhood friends bought around 1950-ish ... we used to drive them silly playing the Goon Show records over & over again.

Lindsay

Astor Radiogram Circuit Diagram


 
 Return to top of page · Post #: 6 · Written at 6:27:24 PM on 4 June 2016.
Scotty's Gravatar
 Location: Melbourne, VIC
 Member since 26 December 2010
 Member #: 794
 Postcount: 274

Thank Guys, there are a number of mica caps around the tuner itself but the values have rubbed off so having the circuit will help identify them so I can replace them.

Cheers
Scott


 
 Return to top of page · Post #: 7 · Written at 7:33:00 PM on 4 June 2016.
MonochromeTV's avatar
 Location: Melbourne, VIC
 Member since 20 September 2011
 Member #: 1009
 Postcount: 1051

 
 Return to top of page · Post #: 8 · Written at 8:24:31 PM on 4 June 2016.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 3791

One thing that has to be ascertained is if it is one band, or all. If it is one then its the circuitry around that coil set, if it is all, then it is the common to all components, and that will narrow it down.

Wire breaks are common when servicing & do not overlook switches. I have had one in the last week where the detent balls were missing and that will cause the switch to not lock in position. Also check the coupling plugs

Often you can pick up the oscillator with a transistor radio, at radio station frequency added to IF frequency (455KHz). Do not assume that it is the converter, if all bands are dead. I normally feed in IF frequency as per alignment to ensure that none of the other stages after the converter have failed: You will not fix the front end if they are not working.

Marc


 
 Return to top of page · Post #: 9 · Written at 9:52:23 PM on 4 June 2016.
Scotty's Gravatar
 Location: Melbourne, VIC
 Member since 26 December 2010
 Member #: 794
 Postcount: 274

Thanks for the links to the circuit Monochrome and the advice Marc, I'm feeling out of my depth on this one as I don't have (I think) equipment to re align a receiver. Is there a way to test if the Short Wave bands are working - it may be the whole tuner is not working.

a detent ball was missing from the selector, I found it and put it back, it appears the switch is locking properly. As I said it was working fine, and then when I went to check it today, it wasn't. All I got was a lot of noise - almost like you were out of range to pick up anything. Adding the arial only made the noise louder.

Cheers
Scott


 
 Return to top of page · Post #: 10 · Written at 12:19:04 AM on 5 June 2016.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 3791

If the noise is louder with an aerial, that is odd, unless the oscillator is dead an that sometimes gives one station. Do you have NBN via a tower?

The NBN box used with a tower, will wipe out a transistor radio at 15 feet, so if you moved the radio close to one it would kill it and an aerial would only make things worse.

The only way to test SW is to try & find a station if there is no equipment like a signal Generator available. I have been fixing for a long time & would reach for an Oscilloscope to see what the oscillator was up to.

I do have a couple of surplus Signal generators. The better and already serviced of the two is a Leader LSG-11. It has provision for a crystal to help calibrate it. I ignore the dial on mine & use a frequency counter to set it.

Marc


 
 Return to top of page · Post #: 11 · Written at 7:08:37 PM on 5 June 2016.
Brad's avatar
 Administrator
 Location: Greenwich, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 5568

Circuit diagram uploaded to Post #5.


‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾
A valve a day keeps the transistor away...

 
 Return to top of page · Post #: 12 · Written at 7:34:50 PM on 5 June 2016.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 5302

we used to drive them silly playing the Goon Show records over & over again

I don't wish to know that. Smile


 
 Return to top of page · Post #: 13 · Written at 10:32:04 PM on 5 June 2016.
Scotty's Gravatar
 Location: Melbourne, VIC
 Member since 26 December 2010
 Member #: 794
 Postcount: 274

Thats Gents, I'm really at a loss as to what to do with this thing.


 
 Return to top of page · Post #: 14 · Written at 11:19:34 PM on 5 June 2016.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 3791

Perhaps walking away & rethinking the methodology: That often helps in spotting the obvious as the brain can get in a rut & miss mistakes that you may have made. You need to start at the power supply, then the Audio then the RF, after you have visibly checked it for the obvious.

Basically: You work backwards, to make sure that the signal path works all the way to the front: If the signal cannot get from the converter / mixer, to the speaker, you are never going to fix a front end signal fault

E.g. I am getting very adept at fixing a HMV R53B as every time it gets transported (which it is not meant to be: Frequently) it seems to get broken.

Much like yours the last complaint was that the audio was dead? Radio SW & Record Changer.... Yeh! Not long since I refitted it (no believe).

Proper investigation revealed a problem with wave change SW, it also switches the changer audio: The second switch that they have managed to break by loosing the detent balls. OK fixed that. powered it amp was working (not surprised, never believed it wasn't); No radio, but dial needle binding; hum when the PU was touched? They broke the wires off at the head (crazy deign). Oscilloscope showed I was right the oscillator was dead. Broken resistor & wire on the switch, but I did change a couple off other resistors as well & the feedback cap.

That sorted that but there is still an intermittent mechanical issue with the plug in Volume pot's socket. Possibly also from vibration? That of course can kill all of the signal.

This is why you assume nothing & having "equipment" and methodology, is handy for getting to the bottom of things swiftly.

As I have been fixing these things for a long while and commercially at times, I can justify the seven, or so, instrument types I have in common use, but I have collected the odd surplus one, rather than see it scrapped.

Marc


 
 Return to top of page · Post #: 15 · Written at 11:58:02 PM on 5 June 2016.
Robbbert's avatar
 Location: Sydney, NSW
 Member since 18 September 2015
 Member #: 1801
 Postcount: 1094

The band switch on Aussie radios has got to be one of the most unreliable things in them. Radio cutting out for no reason can often be fixed by jiggling the switch. My first radio that I got as a teenager had the same problem. Noticed the contacts were partially black. Scraping the contacts inside and out with a screwdriver blade fixed it. But almost all radios will get the problem sooner or later.

If Scotty lived close by I'd offer to take a look... but he doesn't.


 
« Back · 1 · 2 · Next »
 You need to be a member to post comments on this forum.

Sign In

Username:
Password:
 Keep me logged in.
Do not tick box on a computer with public access.