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Success Stories If you have successfully repaired or restored a piece of equipment, why not write up what you did and post details here. Particularly if it was interesting, unusual or challenging. PLEASE DO NOT POST REQUESTS FOR HELP HERE! |
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26th May 2019, 12:56 am | #1 |
Hexode
Join Date: Mar 2018
Location: Bishop Auckland, County Durham, UK.
Posts: 373
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Hacker Autocrat RP33
This AM only radio dates from the late 1960s and uses AF117s in the RF and IF stages. I bought it as non working and was surprised to find that these transistors had been replaced with shiny new-looking AF124s. There was no sound but the audio amp was working as there was a faint hiss when the volume was turned up. The Autocrat runs from an 18 volt supply provided by a pair of PP9 batteries. However the supply for the RF/IF circuits is dropped down to around 9 volts by a 1.5k resistor and decoupled with a 350uF electrolytic capacitor. Measuring this supply rail produced a reading of only 4 volts. I changed the capacitor, which is next to the volume control, for a new 470uF 25v. This restored the 9 volt supply and the radio burst into life. The Hacker Democrat uses a very similar IF panel and the usual cause of low supply voltage is inter electrode shorts in the AF117 transistors.
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Regards Martin |
27th May 2019, 10:49 am | #2 |
Octode
Join Date: Mar 2015
Location: Yorkshire, England.
Posts: 1,303
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Re: Hacker Autocrat RP33
Crikey Martin, 90 views and not one comment!
Well done, it looks really nice with the wood cheeks and must have gathered many envious looks when it was first purchased.
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Regards, Ken. BVWS member |
27th May 2019, 11:14 am | #3 |
Octode
Join Date: Dec 2010
Location: St Ives, Cambridgeshire, UK.
Posts: 1,180
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Re: Hacker Autocrat RP33
Nice sets these, that capacitor causes issues in quite a number of Hacker sets, particularly of that manufacture. You can use a permanent marker pen and fill those missing paint flecks on the grill.
Andrew
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Invisible airwaves crackle with life. Or they should do. BVWS Member |
27th May 2019, 10:36 pm | #4 |
Hexode
Join Date: Mar 2018
Location: Bishop Auckland, County Durham, UK.
Posts: 373
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Re: Hacker Autocrat RP33
Ken and Andrew, thank you for your comments. I had never heard of Hacker radios before joining this forum. They must have been expensive when new. The big speakers and 18 volt supply rail certainly make a difference to the sound. Thanks for the tip about touching up the speaker grille with a black marker pen. I tried this with one of my Democrats and it has worked well. I've noticed that with these radios the volume control only need to be turned about 20 degrees for the sound to be really loud. I was thinking of adding a resistor in the top end of the control to make setting the volume level easier. (This would not have bothered me when I was a teenager)
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Regards Martin |
28th May 2019, 10:17 am | #5 |
Nonode
Join Date: Jan 2004
Location: 1966-1976 Coverack in Cornwall and Helston Cornwall. 1976-present Bristol/Bath area.
Posts: 2,967
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Re: Hacker Autocrat RP33
A nice tidy radio. Well done on finding that fault. This same cap can cause all sorts of strange problems on other Hacker radios.
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Simon BVWS member |
1st Jun 2019, 4:19 pm | #6 | |
Dekatron
Join Date: Apr 2005
Location: Bewdley, Worcestershire, UK.
Posts: 4,748
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Re: Hacker Autocrat RP33
Yes, well done indeed!
Quote:
Such a failure will put stress on the dropper resistor, which is often a low-wattage component, so it’s worth checking that as well before you box it up.
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Phil Optimist [n]: One who is not in possession of the full facts Last edited by Phil G4SPZ; 1st Jun 2019 at 4:20 pm. Reason: Layout |
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