Wanted - audio board for AWA B92 radiogram
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Administrator
Location: Naremburn, NSW
Member since 15 November 2005
Member #: 1
Postcount: 7457
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Photo uploaded to Post 28.
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A valve a day keeps the transistor away...
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Location: Sydney, NSW
Member since 28 January 2011
Member #: 823
Postcount: 6812
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Nice job! Love the period resistors, too.
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Location: Daylesford, VIC
Member since 13 January 2011
Member #: 809
Postcount: 326
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The resistors are Soanar, and they're a bit bigger than they need to be, but I buy them because they're very easy to read and check. The modern blue bodied metal resistors are tiny and hard to decode; the blue base shifts the colours of the bands, making red, orange and brown look murkily similar.
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Location: Sydney, NSW
Member since 28 January 2011
Member #: 823
Postcount: 6812
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Location: Daylesford, VIC
Member since 13 January 2011
Member #: 809
Postcount: 326
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It seems that Soanar doesn't sell 0.5 W carbon film resistors, which is a pity because that size is ideal for restoring 70s transistor equipment.
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Location: Sydney, NSW
Member since 28 January 2011
Member #: 823
Postcount: 6812
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Yes, strange that they jump straight from 0.25 to 1 watt.
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Location: Belrose, NSW
Member since 31 December 2015
Member #: 1844
Postcount: 2528
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Those Soanar resistors are carbon film, like the Philips ones.
Carbon and metal film resistors do not drift. They go open circuit under stress and this is usually (but not always) obvious.
When I'm restoring a chassis I normally would not even bother to test a film resistor, that is how reliable they are.
Except where one has been used inappropriately in a circuit with high pulse or steady state voltages (i.e. 500v or more), such as off the anode of a vertical output stage or around the B+Boost or stabiliser circuits. They don't like that kind of service. If the original was a 68k 1w, say, and I needed to replace it with a film resistor, I would use two 33k 1w film resistors in series to spread the peak voltage.
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Location: Daylesford, VIC
Member since 13 January 2011
Member #: 809
Postcount: 326
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OK, I've got the whole chassis back together, but it's not quite right, so I'll start a thread in the Tech section.
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Location: Daylesford, VIC
Member since 13 January 2011
Member #: 809
Postcount: 326
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Everything is now working properly.
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Location: Toongabbie, NSW
Member since 19 November 2015
Member #: 1828
Postcount: 1336
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Hi Sue, how about in special projects and with lots of pix and text about how you did it?
We are a dying breed of people that actually do stuff instead of talking about it!
I don't care if its a small amplifier or a large radio, its how you solve problems that gets me in.
Cheers, Fred.
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Location: Daylesford, VIC
Member since 13 January 2011
Member #: 809
Postcount: 326
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A good idea, but it's a bit late for a detailed description of this job because it's gone back to its owner. The only photos I have are general shots of the chassis taken after the repair, taken because there's no pictures of the inside of this player online. The worst problem was determining what was missing without reference pictures, and tracing all the loose wires and matching them to the circuit diagram. Really tedious!
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