UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > General Vintage Technology > Success Stories

Notices

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!

Reply
 
Thread Tools
Old 26th May 2019, 12:56 am   #1
martin.m
Pentode
 
martin.m's Avatar
 
Join Date: Mar 2018
Location: Bishop Auckland, County Durham, UK.
Posts: 212
Default 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.
Attached Thumbnails
Click image for larger version

Name:	Hacker Autocrat.jpg
Views:	113
Size:	102.2 KB
ID:	183854   Click image for larger version

Name:	Hacker Autocrat 2.jpg
Views:	105
Size:	100.6 KB
ID:	183855   Click image for larger version

Name:	20190525.jpg
Views:	93
Size:	83.6 KB
ID:	183856  
__________________
Regards
Martin
martin.m is offline   Reply With Quote
Old 27th May 2019, 10:49 am   #2
Kentode
Hexode
 
Kentode's Avatar
 
Join Date: Mar 2015
Location: Todmorden, West Yorkshire, UK.
Posts: 334
Default 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.
__________________
Regards, Ken.

BVWS member
Kentode is offline   Reply With Quote
Old 27th May 2019, 11:14 am   #3
Andrewausfa
Heptode
 
Andrewausfa's Avatar
 
Join Date: Dec 2010
Location: St Ives, Cambridgeshire, UK.
Posts: 963
Default 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
__________________
Invisible airwaves crackle with life. Or they should do.
BVWS Member
Andrewausfa is offline   Reply With Quote
Old 27th May 2019, 10:36 pm   #4
martin.m
Pentode
 
martin.m's Avatar
 
Join Date: Mar 2018
Location: Bishop Auckland, County Durham, UK.
Posts: 212
Default 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)
__________________
Regards
Martin
martin.m is offline   Reply With Quote
Old 28th May 2019, 10:17 am   #5
Hybrid tellies
Nonode
 
Hybrid tellies's Avatar
 
Join Date: Jan 2004
Location: Bristol, UK
Posts: 2,345
Default 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.
__________________
Simon
BVWS member
Hybrid tellies is offline   Reply With Quote
Old 1st Jun 2019, 4:19 pm   #6
Phil G4SPZ
Dekatron
 
Phil G4SPZ's Avatar
 
Join Date: Apr 2005
Location: Bewdley, Worcestershire, UK.
Posts: 4,187
Default Re: Hacker Autocrat RP33

Yes, well done indeed!

Quote:
Originally Posted by Hybrid tellies View Post
This same cap can cause all sorts of strange problems on other Hacker radios.
And not just on Hacker radios. I’ve encountered exactly the same fault on Philips, Grundig, Yaesu, Aiwa, Sanyo and many other makes of equipment where an electrolytic capacitor is used to decouple a resistively dropped supply rail. Electrolytic caps of this vintage are presumably coming to the end of their working life, albeit after several decades. They can of course fail open-circuit as well, and I’ve come across several of those, but going short-circuit is the most common failure mode in my experience.

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.
__________________
Phil

“The place where optimism most flourishes is the lunatic asylum” - Havelock Ellis

Last edited by Phil G4SPZ; 1st Jun 2019 at 4:20 pm. Reason: Layout
Phil G4SPZ is offline   Reply With Quote
Reply

Thread Tools



All times are GMT +1. The time now is 9:01 am.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Copyright ©2002 - 2019, Paul Stenning.