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 Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players

Notices

Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players Open-reel tape recorders, cassette recorders, 8-track players etc.

Closed Thread
 
Thread Tools
Old 22nd Jan 2019, 1:58 pm   #1
A1RXADC
Retired Dormant Member
 
Join Date: Jun 2018
Location: Durham, County Durham, UK.
Posts: 2
Default Grundig CR 485 Transformer Replacement

Hi,
My portable stereo cassette player will not now function on mains.
I have tested on battery without problem(6x 1.5v C cell ).
I have tested and replaced the T630ma fuse without success.
I do not own a multi meter as yet.
Concluding the transformer not working.
Can't see any markings on the transformer but concluding
output is 9v AC.

Can somebody advise what amp. rating I should use for either
replacing the transformer or using a DC power brick connected
to the battery terminals.
A1RXADC is offline  
Old 22nd Jan 2019, 2:57 pm   #2
paulsherwin
Moderator
 
paulsherwin's Avatar
 
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,788
Default Re: Grundig CR 485 Transformer Replacement

9V stabilised at 500mA should be fine. In fact 250mA should be OK if there isn't a CD player built in. Just make sure you connect the supply the right way round.

Replacing the transformer won't be trivially easy if you don't have the right skills and equipment, so a wall wart is the best solution.
paulsherwin is online now  
Old 22nd Jan 2019, 4:12 pm   #3
Studio263
Octode
 
Studio263's Avatar
 
Join Date: Apr 2007
Location: Hampshire, UK.
Posts: 1,574
Default Re: Grundig CR 485 Transformer Replacement

Quote:
Originally Posted by A1RXADC View Post
Can't see any markings on the transformer but concluding output is 9v AC.
That's far too much. If you want a 9V DC supply (= 6 x 1.5V batteries) you divide this by 1.4 (roughly) to get the AC voltage you need to get it. Assuming full wave rectification and ignoring diode drops in the rectifier itself, this works out to about 6.4V. A 6V transformer is therefore the one you need.

To save of space and weight, transformers are usually made to give an excess of voltage output 'off load', this drops down through resistive losses in the windings when you begin to draw current. Therefore, avoid using a transformer which is too big or again you will end up with a surplus of voltage.

What is wrong with the original one? Is there a thermal fuse in the primary winding? You need a meter to check this out, do that first.
Studio263 is offline  
Old 22nd Jan 2019, 4:42 pm   #4
paulsherwin
Moderator
 
paulsherwin's Avatar
 
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,788
Default Re: Grundig CR 485 Transformer Replacement

I agree that it's unlikely the transformer itself has failed, but the OP doesn't appear to have the skills or facilities to do any fault finding, so an external power supply is the simplest solution in the circumstances.
paulsherwin is online now  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 3:10 pm.


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.