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

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Radio (domestic)

Notices

Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only.

Closed Thread
 
Thread Tools
Old 18th Jan 2022, 7:28 am   #1
Stelladragon
Diode
 
Stelladragon's Avatar
 
Join Date: Dec 2021
Location: Preston, Lancashire, UK.
Posts: 6
Default Hacker RP78 Working Current?

Hi folks, I managed to find a replacement BC465 for the RP78 as the original one was split. Fitted it, and checked the cap across the battery input. It works well enough on all bands, but is drawing around 80mA on FM at moderate volume. This seems high, any suggestions on anything else I can check etc? Thanks, Russ.
Stelladragon is offline  
Old 20th Jan 2022, 1:08 pm   #2
Vicboduk
Hexode
 
Join Date: Aug 2007
Location: S.W. London, UK.
Posts: 416
Default Re: Hacker RP78 Working Current?

Hi Russ, I have a RP78 and have taken some measurements for you. The figures are for total current from the battery terminals at 9 volts.

FM mode tuned to a station;

23mA, Volume at minimum
25mA, Volume at my normal listening level
40mA+, Volume at moderately loud

---------
AM mode tuned to a station;

19.5mA, Volume at minimum
21.5mA, Volume at my normal listening level
40mA+, Volume at moderately loud


Your value of 80mA does seem excessive. As you have been working in the output stage it would be wise to check the output stage quiescent current setting.

Vic
Vicboduk is offline  
Old 21st Jan 2022, 3:56 pm   #3
Graham G3ZVT
Dekatron
 
Graham G3ZVT's Avatar
 
Join Date: May 2010
Location: Greater Manchester, UK.
Posts: 18,668
Default Re: Hacker RP78 Working Current?

Hi Russ,

Have you performed this adjustment?

Click image for larger version

Name:	quiescent.jpg
Views:	57
Size:	24.3 KB
ID:	250111
__________________
--
Graham.
G3ZVT
Graham G3ZVT is online now  
Old 23rd Jan 2022, 4:39 pm   #4
Stelladragon
Diode
 
Stelladragon's Avatar
 
Join Date: Dec 2021
Location: Preston, Lancashire, UK.
Posts: 6
Default Re: Hacker RP78 Working Current?

Thanks Vic, much appreciated. I'll have a look at it tomorrow. Apologies for the ignorance, but that will the pot on the output stage board? Cheers, Russ.
Stelladragon is offline  
Old 23rd Jan 2022, 7:11 pm   #5
Stelladragon
Diode
 
Stelladragon's Avatar
 
Join Date: Dec 2021
Location: Preston, Lancashire, UK.
Posts: 6
Default Re: Hacker RP78 Working Current?

Tremendous progress! I tried adjusting the current with the pot, and it made no difference at all. So, I removed it from the board and checked the resistance, and it is fine. I took both electrolytics out of the board, tested them and the 1000uf was short circuit. Replaced with a decent used one (slightly smaller) and I've set the rest current to 23ma. It's singing away now! Happy days!
Stelladragon is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 5:38 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 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.