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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
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24th Feb 2021, 2:05 pm | #21 |
Heptode
Join Date: Nov 2008
Location: Stockport, Cheshire, UK.
Posts: 710
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Re: Pocket radio repairs
Classic Gold AM is quite good round here, their website says 1458 AM
The station is loud enough, distortion is not like a faulty speaker, it's more like a faulty amplifier would sound. But on R5 it plays fine at low volume. Shame l can't post an audio clip of it. The trimmer on the tuner will peak the signal at 1458, it comes in louder but with the same distortion. Maybe l should try the detector diode as suggested. Will one out of another similar set do? Last edited by lightning; 24th Feb 2021 at 2:12 pm. |
24th Feb 2021, 3:34 pm | #22 |
Dekatron
Join Date: Aug 2013
Location: Wigan, Greater Manchester, UK.
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Re: Pocket radio repairs
Have you a way to inject an audio signal into the volume control? That way you could rule out RF/IF stages or Audio stages that is causing the fault.
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Frank |
24th Feb 2021, 7:04 pm | #23 |
Dekatron
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Location: Chesterfield, Derbyshire, UK.
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Re: Pocket radio repairs
can you check the voltages on the transformer nearest the output transistors, note! voltages measured from the poss side of the battery, Do you have a circuit. Mick.
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24th Feb 2021, 7:27 pm | #24 |
Dekatron
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Location: Wigan, Greater Manchester, UK.
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Re: Pocket radio repairs
Not going to be exactly the same but probably similar if no circuit available.
http://fourier.eng.hmc.edu/e84/labs/radio.gif
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Frank |
24th Feb 2021, 8:55 pm | #25 |
Heptode
Join Date: Nov 2008
Location: Stockport, Cheshire, UK.
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Re: Pocket radio repairs
Thank you l will get on to this and report back.
Also l think it's time to buy a signal injector! |
25th Feb 2021, 10:13 am | #26 |
Heptode
Join Date: Nov 2008
Location: Stockport, Cheshire, UK.
Posts: 710
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Re: Pocket radio repairs
ls the detector diode anything special or will any small diode do the job?
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25th Feb 2021, 10:25 am | #27 |
Dekatron
Join Date: Feb 2009
Location: Chesterfield, Derbyshire, UK.
Posts: 3,737
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Re: Pocket radio repairs
Hi have you checked the diode , it should be a Germanium type, Mick.
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25th Feb 2021, 3:18 pm | #28 |
Dekatron
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Location: Croydon, Surrey, UK.
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Re: Pocket radio repairs
Any small germanium should do the job. Nothing special at all.
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25th Feb 2021, 10:59 pm | #29 |
Heptode
Join Date: Nov 2008
Location: Stockport, Cheshire, UK.
Posts: 710
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Re: Pocket radio repairs
Thank you for the information, l will let you know how l get on with it.
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26th Feb 2021, 12:03 am | #30 |
Dekatron
Join Date: Feb 2009
Location: Chesterfield, Derbyshire, UK.
Posts: 3,737
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Re: Pocket radio repairs
Hi what makes you think the diode is at fault? Mick.
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26th Feb 2021, 12:39 pm | #31 |
Heptode
Join Date: Nov 2008
Location: Stockport, Cheshire, UK.
Posts: 710
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Re: Pocket radio repairs
On a previous post someone said the detector diode could be faulty and it receives strong stations but not weaker ones, it's something l could try in the absence of any test equipment to diagnose the fault.
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26th Feb 2021, 1:18 pm | #32 |
Dekatron
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Re: Pocket radio repairs
Mick suggested some voltage readings be taken, I would do those first.
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Frank |
26th Feb 2021, 8:12 pm | #33 |
Heptode
Join Date: Nov 2008
Location: Stockport, Cheshire, UK.
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Re: Pocket radio repairs
Yes will do, will get on to it this weekend
lt's a steep learning curve. |
27th Feb 2021, 8:27 am | #34 |
Dekatron
Join Date: Sep 2011
Location: Rugeley, Staffordshire, UK.
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Re: Pocket radio repairs
Does the detector diode on a set like this have to be germanium? What happens if a silicon one is used?
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28th Feb 2021, 7:58 am | #35 |
Dekatron
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Re: Pocket radio repairs
Not thought about it but it would depend on the silicon diode. A 1N4001 will be different than say a fast acting diode, the conduction voltage is different with silicon being around 0.6v and germanium 0.2v so the germanium will be more sensitive. The junction capacitance will have some effect, presume a germanium will be less but I have not checked.
I am not a designer so I tended to replace like with like unless it was obvious a more suitable part was available.
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Frank |
28th Feb 2021, 8:30 am | #36 | |
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Re: Pocket radio repairs
Quote:
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28th Feb 2021, 8:51 am | #37 |
Dekatron
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Re: Pocket radio repairs
I have probably got the wrong data sheet but the 10D4 appears to be a rectifier for 50/60 Hz. It’s needs someone better than me to give a conclusive answer but for me junction capacitance and forward turn on voltage are the important specification. Small signal diodes such as 0A91 are germanium (0.2v) point contact ( low capacitance).
https://www.digchip.com/datasheets/p...2/10D4-pdf.php
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Frank |
28th Feb 2021, 9:35 am | #38 | |
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Re: Pocket radio repairs
Quote:
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A digital radio is the latest thing, but a vintage wireless is forever.. |
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28th Feb 2021, 9:37 am | #39 |
Dekatron
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Re: Pocket radio repairs
See what others members can explain.
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Frank |
28th Feb 2021, 10:44 am | #40 |
Heptode
Join Date: Nov 2008
Location: Stockport, Cheshire, UK.
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Re: Pocket radio repairs
Can someone recommend a suitable germanium diode that l can buy online, that will do the job on this radio?
Or sell me a couple? l've got plenty of random diodes on circuit boards and in boxes of components but no idea which are germanium. |