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 AWA Radiola 586-MA astounds me
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 Return to top of page · Post #: 1 · Written at 12:39:26 PM on 9 March 2019.
Stdavies's Gravatar
 Location: Metford, NSW
 Member since 23 December 2018
 Member #: 2313
 Postcount: 12

Hi All,

I picked up 3 radios this week. I have already posted about the mystery 1930s console AC/DC portable, but here is the story of the third radio to be looked at - the Radiola.

I began by checking the power cord and testing the mains transformer - both are ok.

Next came the main filter capacitors - I checked them both for shorts - once again all ok.

The output transformer was tested next, and it was fine.

With a hand on the power plug (the mains switch had broken some time in the past and it had been bypassed) and my multimeter on the B+ test point I gingerly pushed the plug into a 240v outlet. The HT was slow to come up - very slow. it rose to 50v in about 2 min. I checked the current from the rectifier to see if it was overloaded, but it was less than a milliamp.

"Bugger", I thought, "I don't have a spare 6X4 to try."

I thought it was best to keep checking voltages on the other valves while I could, just to make sure none were gassy or internally shorted.

Lo and behold, after about 5 min of this I heard a crackle from the loudspeaker! We were experiencing a thunderstorm at the time.

Unable to believe my ears, I tuned our local ABC and sure enough, up comes the Saturday Grandstand show! I quickly plugged the meter into the test plug again and could not believe my eyes - the whole radio was working from just 61v at the output valve (65v at the main HT cap).

These old things never cease to amaze me...............

Now I just need to wait for my 6X4 to arrive so I can turn it up a bit to suit my old ears..........


 
 Return to top of page · Post #: 2 · Written at 12:40:17 PM on 9 March 2019.
Stdavies's Gravatar
 Location: Metford, NSW
 Member since 23 December 2018
 Member #: 2313
 Postcount: 12

 
 Return to top of page · Post #: 3 · Written at 1:25:57 PM on 9 March 2019.
Tallar Carl's avatar
 Location: Latham, ACT
 Member since 21 February 2015
 Member #: 1705
 Postcount: 1275

Your 6x4 may just have dirty sockets and pins. I use brasso with a pipe cleaner or in your case a bit of string pulled back and forth through the sockets. And a bit of sandpaper on the sockets. Then flush it with good contact cleaner.
Your electrolytics are not ok! When you replace them and all the paper caps you my find you don't need a new 6x4.


 
 Return to top of page · Post #: 4 · Written at 1:57:21 PM on 9 March 2019.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 5061

The B+ from the 6X4 should be 250 volts and the 6AQ5 should have 240V on the plate, so yes, it is amazing that the set actually works but ABC transmits at very high power so, if any station had a chance of getting through, ABC would be it.

It seems the low B+ has slowly re-formed the electros to some extent. As you may be aware, the full B+ voltage may well have tuned them into Roman Candles.


 
 Return to top of page · Post #: 5 · Written at 2:53:44 PM on 9 March 2019.
Stdavies's Gravatar
 Location: Metford, NSW
 Member since 23 December 2018
 Member #: 2313
 Postcount: 12

I'm aware the electros will need to be changed.

I spent 15 years in TV repair before the bottom dropped out. I've been covered in brown and silver confetti from exploding electros more than once LOL.

My normal practice with silicon power supplies is to replace caps before turning on, but with valves I always measure first and monitor during warm-up to try to get an idea of what's wrong before heading off to Jaycar.

Regarding the cleaning of the pins and socket, yes I will try that. I had another where I thought I may need a new valve only to find that half a sleeve had broken inside a socket and was causing intermittent contact. Hopefully I won't get tricked by that one again.


 
 Return to top of page · Post #: 6 · Written at 4:15:38 PM on 9 March 2019.
Robbbert's avatar
 Location: Sydney, NSW
 Member since 18 September 2015
 Member #: 1801
 Postcount: 989

I'd still be looking at replacing all the paper / wax capacitors, especially the one that feeds audio into the output valve.


 
 Return to top of page · Post #: 7 · Written at 5:03:36 PM on 9 March 2019.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 3433

The NP cap with the highest probability of a fail is the plate bypass on the OP tube. In cases where the Electrolytics are a bit more modern & there are no wax paper caps, in the valve set; I will resort to powering the "B" from the reformer & stepping the voltage up gradually.

This applied to a Thorn Radiogram (no circuit yet) where the power transformer secondary staged a melt down. This had to be a short. As it has a metal rectifier, which have an extremely poor reputation for reliability, it was disconnected & the "B" powered (no heater power) everything seemed happy & it was subsequently confirmed that the rectifier was the culprit: Another test method. The chip in the reformer will "lock up" if there is a overload.

Whilst I have seen some in magazines who I consider need re-educating, for leaving wax paper caps in sets. Fifty+ years of fixing says that's not best practice. I really don't care by how much a wax paper cap leaks. A capacitor should not pass DC, if it does its a dud.


 
 Return to top of page · Post #: 8 · Written at 8:49:39 AM on 10 March 2019.
Irext's avatar
 Location: Werribee South, VIC
 Member since 30 September 2016
 Member #: 1981
 Postcount: 141

I've found when reforming old electrolytics that they behave a bit like zener diodes until they are fully reformed.
I have a small low current variable 300v supply which I use for this purpose.
I put a 1k resistor in series and a meter across the cap.
I see the voltage steadily rise over an hour or so but what is very interesting is if you disconnect the supply before the cap is fully restored then discharge the cap.
When it's reconnected to the supply it very quickly comes up to the voltage it was just before being disconnected then continues to slowly rise from there.
Once fully reformed it comes up quickly to it's rated voltage.
The 300V supply was bought on Ebay and only cost a few dollars. It's 12V in and variable up to 300V out. Very handy.


 
 Return to top of page · Post #: 9 · Written at 10:23:57 AM on 10 March 2019.
Jimb's Gravatar
 Location: Kanahooka, NSW
 Member since 18 November 2016
 Member #: 2012
 Postcount: 242

I was somewhat amused by Stdavies comment about heading off to Jaycar. Your Jaycar must be heaps better the two near me.It is getting harder and harder to buy anything useful from these stores they are becoming another retail store catering for techno yuppies who want to buy the latest gizmoletry .
Regards Jimb


 
 Return to top of page · Post #: 10 · Written at 3:48:48 PM on 10 March 2019.
Brad's avatar
 Administrator
 Location: Greenwich, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 5203

My prediction is to expect that to continue, regarding Jaycar. At the moment, it is still possible to get rare components from them but the owner of the business is exploring an exit strategy, which includes a float of the business. The logo has changed for the first time since the merger of John Carr Electronics and Bill Edge Electronics and I am guessing the exit of the sponsorship of the Canterbury-Bankstown Bulldogs due to the Mad Monday saga was just a timely excuse, as companies looking at a change of ownership don't want big financial commitments hanging over them and sponsoring a Rugby League club isn't a cheap exercise.

Jaycar, as this stage, is also still selling kits, test equipment and tools as well as components and I hope this continues. Their only real competition is Altronics and they don't have as many stores.


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A valve a day keeps the transistor away...

 
 Return to top of page · Post #: 11 · Written at 4:50:31 PM on 10 March 2019.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 5061

the owner of the [Jaycar] business is exploring an exit strategy, which includes a float of the business

Where did you hear that?


 
 Return to top of page · Post #: 12 · Written at 5:21:09 PM on 10 March 2019.
Brad's avatar
 Administrator
 Location: Greenwich, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 5203

To be honest I don't remember but when the Mad Monday issue came up last year, a few were saying to me that this is the perfect 'out' for Jaycar as a sponsor.

Of course, this is all hearsay. None of it may be true - it just makes sense if it is.


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A valve a day keeps the transistor away...

 
 Return to top of page · Post #: 13 · Written at 6:10:17 PM on 10 March 2019.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 5061

Jaycar's printed catalogue gets bigger every year. While it's handy to have on the sales counter, I really don't know why they still bother to publish it given the humongous manual effort required to lay it out and proof read it. Frankly, I'd prefer that they put the money and effort into building a better website. Altronics' website is heaps better.


 
 Return to top of page · Post #: 14 · Written at 6:38:38 PM on 10 March 2019.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 3433

There are two principal reformers in use here for Electrolytic caps. One is the Circa 1938 VCT "Valve & Circuit Tester" which uses a meter. It is principally for those of its era. So we have 25V and 225V. So even back then, when Electrolytic caps were in their infancy, they were well aware of their failings.

The more sophisticated, is much as described. It is the one from SC that was described by Rodney Champness. Mine is built onto the bench PSU which can get to 400V. It has stepped voltages controlled by a very handy LR8 (which I have used for PSU "B" for valves like UX-201-A.

The reformer & like yours uses the drop across a 1K resistor, for current and discharges by switching in 10K. It is extremely useful for the new dud cap that gets to a specific voltage below its rating & then starts drawing current at a hyperbolic rate.

If you want caps for valve radio's which for NP types, which are going to be 630V Jaycar is not the place. Beware with resistors under 1W they may not have the voltage rating needed; That also applies to test equipment.


 
 Return to top of page · Post #: 15 · Written at 6:42:52 AM on 11 March 2019.
Jimb's Gravatar
 Location: Kanahooka, NSW
 Member since 18 November 2016
 Member #: 2012
 Postcount: 242

When I returned to the workforce at age 57 after going broke running my own business the company I was working for had an account with Electus it basically was the supply chain for Jaycar, much bigger and better range at greatly reduced prices. Unfortunately they do not sell to the public. I sorely miss not having it at my disposal.
Regards Jimb.


 
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