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 Airvoyce=Mystery Valve
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 Return to top of page · Post #: 1 · Written at 8:30:39 PM on 4 July 2016.
JamieLee's Gravatar
 Location: Clare, SA
 Member since 27 March 2016
 Member #: 1894
 Postcount: 508

Hello!
I have finally pulled the chassis out of my Airvoyce radiogram pictured in my "General discussion post "Airvoyce" several weeks ago, in order to re-cap and clean it up;
Airvoyce were sold by Charles Birks department store in Adelaide and due to the Garrard 78rpm only turntable, I estimate it to be made sometime between 1947 and 1953, only guessing though... The chassis apparently would have been made by a larger manufacturer for this brand and If anybody has any clues as to whom that manufacturer might be I would be grateful, especially as one particular valve, which I believe to be the rectifier (the pins mostly connected to the power transformer), has the valve type number rubbed off, therefore I am at a loss to identify it.
The other valves in the lineup are as follows: 6BE6, 6BH5, 6BD7, 6M5, and ???
I have emailed photos, when they are uploaded, from left to right along the chassis, they are in the above order.
Can anybody help me Identify the mystery valve?
Cheers Smile

Airvoyce Radio
Airvoyce Radio


 
 Return to top of page · Post #: 2 · Written at 10:36:54 PM on 4 July 2016.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 5830

That line-up needs a rectifier. Guessing 6V4, which as 9 pins, or 6X4 with 7 pins.


 
 Return to top of page · Post #: 3 · Written at 5:30:24 AM on 5 July 2016.
MonochromeTV's avatar
 Location: Melbourne, VIC
 Member since 20 September 2011
 Member #: 1009
 Postcount: 1098

The chassis looks like it could be made by Precedent. (A.W. Jackson)

The unknown valve will be a 6V4. I have on numerous occasions mentioned here how to identify unknown valves by the factory codes.

Is the small transformer under the chassis a choke or a speaker transformer? If it is a speaker transformer then I'd look at Precedent model/models 534A or 515 in AORSM Vol. 14 or JR Publications Radio Service Handbook.


 
 Return to top of page · Post #: 4 · Written at 2:31:42 PM on 5 July 2016.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 5830

Looks to be a choke.


 
 Return to top of page · Post #: 5 · Written at 8:38:40 PM on 5 July 2016.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 4178

Choke will have two wires, speaker transformer four and as that audio plug has four terminals wired, its a fair bet that the at the soon to be replaced cap on it is the 6M5 plate bypass (6M5 pin 7) and another goes to B+ (pin1, 6M5 screen) Valve socket Pin 6 is a dead pin & could have nothing or anything on the socket pin 6.

So the OP transformer is / was on the speaker.

The only 7pin socket to me is the Pentagrid so the rectifier is more likely 6V4 pins 1&7 are the diode plates (to transformer); Cathode (B+ out) pin 3. Heaters 4&5.

Marc


 
 Return to top of page · Post #: 6 · Written at 10:17:14 PM on 5 July 2016.
JamieLee's Gravatar
 Location: Clare, SA
 Member since 27 March 2016
 Member #: 1894
 Postcount: 508

Yes only two wires, it's a choke on the heater circuit, It looks like it's going on the back burner for a bit as although I have bags of capacitors, the values all seem to be wrong, I need .02μF but only seem to have .o22... I need a .05, yet none of those, 22μF electro, when I need 24μF, I need an 8μF but only have 10uf... etc. So the jobs turned a bit howdy doody. So I'm going to need to source the specific ones. and just wait until I get them. I find the codes really confusing although I have a code sheet showing what is what, some of the smaller cas, the labels have peeled off.
Is there any way of ascertaining their value with a multi meter?
Not many cas in this one, just different values to the ones I have?


 
 Return to top of page · Post #: 7 · Written at 11:05:17 PM on 5 July 2016.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 4178

Decades ago the "preferred" range of capacitors & resistor values came about: Changed from the old RMA & rafferty's rules of the past.

Also the voltage steps changed & 200V & 400V virtually disappeared with the introduction of polymer dielectrics. All of the NP caps in the valve radio will be 500V for Mica & Ceramic and 630VDC for the others.

If you buy a capacitor bulk bag of caps, these will be of a size that you do not need & that's how they got rid of them.

Some do stock electrolytics in the old values. You will probably find 450V common & most suited to that in electrolytics.

0.022 mfd (223) replaces 0.02 mfd
0.047 mfd (473) replaces 0.05 mfd

The electrolytic tolerances were fairly wide (& wild) replace 8μF with 10μF and 24μF with 22μF. and make sure you check the resistors, as you go. Some look odd & the one with a green body and yellow band belongs to a group type that fail regularly. In commercial fixing 10% is my red line.

The squarish, Brown Bakelite caps do not have labels it is painted on there body and are of type (Mica) one leaves alone, due to their rare fail rate. If one is out of circuit to replace something, I High voltage leakage test it (minimum) anyway.

You cannot tie a knot in the mains cable, like that has, in this day & age.


 
 Return to top of page · Post #: 8 · Written at 11:54:25 PM on 5 July 2016.
JamieLee's Gravatar
 Location: Clare, SA
 Member since 27 March 2016
 Member #: 1894
 Postcount: 508

I need a -005uf...
Can capacitors be used in series, like 2x .022μF to get .05 thereabouts?


 
 Return to top of page · Post #: 9 · Written at 10:24:30 AM on 6 July 2016.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 4178

No! Capacity decreases in series: Increases in parallel. Modern 0.005mfd is 0.0047mfd (472) 2 x 0.0022mfd in parallel is 0.0044mfd, that looks like a plate bypass on 6M5; Use 630V or greater. The greatest risk on that cap, when plate to ground, is the audio transients not the DC.

Five 0.001mfd (102) is just plan messy & something I would not do. Even that I have stocks and I fix them.


 
 Return to top of page · Post #: 10 · Written at 12:11:28 AM on 7 July 2016.
JamieLee's Gravatar
 Location: Clare, SA
 Member since 27 March 2016
 Member #: 1894
 Postcount: 508

Whew, finished re-capping, I did have the ones I needed, just was confused about the codes and wasn't reading them properly.
Thank you very much Marcc, for your help, your information got me sorted!
It all works fine, the short wave which just made awful crackling noise now excels, I've just been listening to radio Thailand!!!
Unfortunately I didn't get to the resistors as I need to re-lern the colour codes and get my hands on a good chart, then buy a supply of them so I can just dive into it and start replacing them, another job for another day at this point, but it'll give me something meaningful to do on a rainy day in the future! I'll get to it. Good to hear it sounding so good, knowing it won't self destruct.
The volume is still quite audible at zero, soft enough to sleep with, I wonder if that may be possible evidence of a resistor out of spec, or whether it's just normal for that particular radio?
Shortwave needs much more volume, to find stations but hey come through loud and clear, hundreds of them! Well scores at any rate lol.
Might need to start collecting spare valves, hopefully find some brand new old stock.
Thank you again for your invaluable help!!!
Cheers.


 
 Return to top of page · Post #: 11 · Written at 1:17:06 AM on 7 July 2016.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 5830

The volume is still quite audible at zero, soft enough to sleep with

There's no way on earth I would leave an old set powered on while I slept, nor when I'm out of the house.

I'm sure that Brad will chime in with a related story.


 
 Return to top of page · Post #: 12 · Written at 9:18:40 AM on 7 July 2016.
Brad's avatar
 Administrator
 Location: Greenwich, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 6174

The infamous story about a Kriesler 11-20 'plum pudding' I listened to back around 1991.

I'll type up something tonight but yes - never go to sleep with an old radio or even leave one unattended. They can catch fire without warning, even after servicing.


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

 
 Return to top of page · Post #: 13 · Written at 9:48:29 AM on 7 July 2016.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 4178

It is likely that few resistors will have wandered off, that is why I check them as I refit the set. It saves time & rework can result in damage and there is also less risk of frustration, when a dud causes it not to work.

Once the front end has been tampered with and parts changed, it has to be re-aligned: Alignment and an inadequate antenna's are major causes of "deaf" sets. That needs to be done.

The other cause of deafness on SW is loss of modulation: It occurs as the frequency increases anyway. This loss can be exacerbated by a weak valve, but more commonly, the valve running out of volts, due to "high" out of tolerance resistors and leaking caps impinging on the bias.


 
 Return to top of page · Post #: 14 · Written at 4:07:55 PM on 7 July 2016.
JamieLee's Gravatar
 Location: Clare, SA
 Member since 27 March 2016
 Member #: 1894
 Postcount: 508

OMG really? I've always slept with the radio on very softly! In fact I can't easily get to sleep without it! Ok I'll get a battery smoke alarm and fire extinguisher and put it next to my bed...
Is re-aligning a difficult task? My radio is working ok, loud and clear, the shortwave on this never worked but it's great now...
One question. Do old resistors use the same colour codes as new ones?


 
 Return to top of page · Post #: 15 · Written at 4:15:53 PM on 7 July 2016.
JamieLee's Gravatar
 Location: Clare, SA
 Member since 27 March 2016
 Member #: 1894
 Postcount: 508

I have a 1958 Blaupunkt New York at my cottage in Sedan which I left on for over 12 months when I was living there, I'd simply turn down the volume if not listening to it, but it gave my dogs company whilst I was at work. (This was before I knew about restoring and re-capping) Sadly it doesn't work any more due to mice getting into it, I think FM still faintly worked last time about 9 months ago when I tried it, but the antenna was live with around 100 volts so its in storage. I'll have a go at fixing it eventually. once I've gained more experience on simpler sets!


 
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