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 What's this Radio?
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 Return to top of page · Post #: 1 · Written at 7:55:20 PM on 23 April 2017.
JamieLee's Gravatar
 Location: Clare, SA
 Member since 27 March 2016
 Member #: 1894
 Postcount: 508

I have just bought and finished re-capping this lovely old Console. Steve Savell has narrowed it down to Adelaide made and 1935 as the year, but as to who actually manufactured it is yet a mystery?

The valve lineup id 80, 42, 75, 6D6 and 6D6.

It has "Goat shields" on three valves and a friction drive tuner.

Unknown Radio
Unknown Radio
Unknown Radio


 
 Return to top of page · Post #: 2 · Written at 8:13:11 PM on 23 April 2017.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 6012

Is there a 6A7 also in that line-up?


 
 Return to top of page · Post #: 3 · Written at 8:52:07 PM on 23 April 2017.
JamieLee's Gravatar
 Location: Clare, SA
 Member since 27 March 2016
 Member #: 1894
 Postcount: 508

It is possible I may have misread one of the 6D6's as one definitely is, the other was a lot more faded and hard to decipher?


 
 Return to top of page · Post #: 4 · Written at 9:05:48 PM on 23 April 2017.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 6012

So, only 5 valves in total?


 
 Return to top of page · Post #: 5 · Written at 12:13:05 AM on 24 April 2017.
JamieLee's Gravatar
 Location: Clare, SA
 Member since 27 March 2016
 Member #: 1894
 Postcount: 508

Yes 5 in total, I'm fairly sure they are both 6D6's s I usually have a pretty good gander, so if you know of a contender with 2 of these, 75, 42 and 80, it might be apparent to be a certain make?

[Photos pending]

It has high voltages, without the 80, there's 425 volts on the rectifier pins! 575volts DC with the 80 (only) in, I suspect it will lose 100 volts or so with the valves all in and speaker plugged in, but it's pretty hot, quiet a loud hollering radio, louder than the others!

It had couple of 25μF 25V electro's with piggybacked wire wound resistors! Ever seen that? I made up 2 x 25uf's using one 16 and 1 8μF electro (500V) with another 1μF poly (600V) all in parallel of course adding the resistor which was originally there, so 500-600V caps replacing 25V ones, but they re working well, this radio is a real belter!


 
 Return to top of page · Post #: 6 · Written at 2:43:54 AM on 24 April 2017.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 6012

Maybe one of those valves is a 6C6?

Be very careful measuring voltages above 500V as that will push the safe limit of many probes.

Sounds like RC filters.


 
 Return to top of page · Post #: 7 · Written at 10:25:10 AM on 24 April 2017.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 4342

6C6 was commonly used as a separate exciter, but more commonly as an an RF / IF amp but the second tube when used as an Autodyne converter.


More likely a 6A7 its top cap would go to the tuning gang. Reverse engineering would identify. A common thing with 6A7, 6A8, 6J8 Pentagrid is that Grid #1 is often has 50K to its Cathode. 6A7 was used in hundreds of sets with that pin out and line up.

If that has a field coil that will eliminate several sets by its resistance value.

25V caps were probably cathode caps and rarely were they over 25V.

I have serious concerns as to how you have measured the voltages etc and how this is all going. I will not use less than 600V filters on #80. The first filter cap has a significant effect on the DC voltage developed. The only tube I would expect 400 or so volts on would be one like a a #50.

I would expect twice EMF with the "B" voltage unloaded.

With the #80 removed, small pins are measured from them,to ground (chassis).

I would agree with the meter comment: Modern meters are not designed for valve radio. Some will not handle the voltages, or RF. Measuring plate to plate on a rectifier needs a meter that will withstand 1kV or often more. That goes into the realm of industrial types.
Digital meters are often hopeless with dirty & fluctuating voltages.


 
 Return to top of page · Post #: 8 · Written at 4:10:33 PM on 24 April 2017.
Brad's avatar
 Administrator
 Location: Greenwich, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 6349

Some will not handle the voltages, or RF.

I'd go as far to say most won't. Most digital meters are rated at 600VAC or 1000VDC and some are not even that generous. A Fluke true RMS meter, rated at 1000VAC/DC is probably the best meter for this job, though in any application where the measured potential difference is fluctuating then only an analogue meter with a suitable visual resolution will give the user an idea of what the median voltage may be.

With regard to probes, the good ones are rated at 1,000 volts and I wouldn't use anything with a lesser rating. I always buy Fluke moulded ones instead of the ones where the coloured plastic insulation is screwed to the tips. I even use the same probes on my electrical test lamps.

Buying test equipment is like anything else I reckon. A good meter with a high voltage rating and good quality probes will cost a lot of money. But you'll get something that lasts a long time, doesn't need calibrating very often and can be trusted. If you pay $40 for a meter then you'll get $40-worth of meter. It won't be backlit, its readings won't always be accurate and the probes will be rubbish.


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

 
 Return to top of page · Post #: 9 · Written at 4:37:53 PM on 24 April 2017.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 4342

The be all & end all is that it is the end use that governs what instrument you buy. Often price will not get you what you actually need. Some of the big purveyors of tube radio parts will not stock unsuitable instruments & that's why you pay.

It always pays, if there is RF, to absolutely insure that it will not cause an internal flashover. So you need to ask and look at the manual: No say no buy.

I have two vehicles with DC generators. I use an AVO 7X on them (500 opv) it should not flashover below 3KV & wont see RF on a DC range. Some digitals will detect RF & use the resultant voltage, for its own confusion.


 
 Return to top of page · Post #: 10 · Written at 5:23:40 PM on 24 April 2017.
Johnny's avatar
 Location: Hobart, TAS
 Member since 31 July 2016
 Member #: 1959
 Postcount: 410

Keep in mind we are servicing mainly domestic vintage valve radio here.
Not a 100 Kilowatt Transmitter.
Having said that, most professionals including the last respondents would have suitable test equipment.
For those new to the hobby, then I suggest the specifications of a Fluke 73 or 75, be minimum.
With their test leads of course.
Unfortunately there are far too many $20 digital meters around and owners that swear that's all that's required.
JJ


 
 Return to top of page · Post #: 11 · Written at 9:17:40 PM on 24 April 2017.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 4342

The AVO may be considered an over kill: But! This is ex military and was acquired many years ago at a good price.

It is absolutely not suited to 99% of transistor IC circuits due to the low impedance, but that does not render it useless.

It is an Industrial grade machine: Therefore it was built to a (British) standard; That ensures a level of quality.

But it has a niche that the digital cannot fill and the digital a niche that the AVO cannot fill.

In order to get accurate results you must understand the instrument and what it is telling you.

A classic on an RCA schematic (R2 I think) points out that the voltage you measure at a specific point, is not (due to loading) the voltage that the Radiotron element is running on: This is why you need understanding.

Do note AVO 7X has paper caps in it and these should be replaced. One is common to the DC 400V range, it was the one that failed in mine. The other one was not given the opportunity.

Marc


 
 Return to top of page · Post #: 12 · Written at 10:31:47 PM on 26 April 2017.
JamieLee's Gravatar
 Location: Clare, SA
 Member since 27 March 2016
 Member #: 1894
 Postcount: 508

Yes Pin to Chassis, and my Multimeter is a digital one, although I am planning on upgrading, mine cost me about $70 Trade, It's basically an Automotive unit and has been fairly rugged and reliable. I was entertaining the possibility that I had found myself in one of those Wiley Coyote type moments with 575Volts, when my new Filter Caps were only 500Volt Evatco ones! However without any load on the circuit, I don't think this would be normal, anyhow I know where I can get 600volt ones now, so will change them.


 
 Return to top of page · Post #: 13 · Written at 10:34:13 PM on 26 April 2017.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 6012

Any photos of the radio?


 
 Return to top of page · Post #: 14 · Written at 10:37:59 PM on 26 April 2017.
Brad's avatar
 Administrator
 Location: Greenwich, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 6349

Awaiting clearer photos of the front of the set.


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

 
 Return to top of page · Post #: 15 · Written at 1:06:38 AM on 27 April 2017.
Tallar Carl's avatar
 Location: Latham, ACT
 Member since 21 February 2015
 Member #: 1705
 Postcount: 1574

Steven Savell has the 600 volt caps. If not I will see what I have.


 
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