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 > General Vintage Technology > Success Stories


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!

Closed Thread
Thread Tools
Old 8th Sep 2018, 8:56 pm   #1
Mikey66's Avatar
Join Date: Dec 2008
Location: Swinton, Manchester, UK.
Posts: 264
Default B&O 3163 mx3500

I've always wanted one of the smaller B&O MX series tellies, when I won this set at an auction for a small sum I was over the Pennines in a flash to collect it.

The chap who sold it to me said it might be the fuse inside, I've heard that one before. Once I managed to get it up on the bench, the first thing I noticed was one of the screws securing the back was missing... oh dear.

Upon removing the remaining screws the set looked quite tidy and untouched.

Nothing looked untoward so I fitted a plug and switched on, there was a slight "humph" and nothing else. When I removed the power there the sound of a fading whistle.

Oh well, at least it didn't blow up! Eventually I managed to find the correct manual (I incorrectly downloaded the MX4000 one first) and decided to do some cold checks.

As the power supply is easily accessible I quickly checked the reservoir caps on the secondary side of the chopper transformer, C13, the 148V reservoir cap measured short circuit. I removed the power board from the set and the short across C13 disappeared. Tracing the 148V to the lower line output panel I clocked TR8 (BU508A) looking all innocent.

Once I had disconnected various plugs I was able to slide the chassis out completely and look at the underside of the board. The BU508A was easily isolated from the PCB thanks to the B&O method of soldering it onto the board (The legs pass through the PCB and bend over towards the solder pads - never seen this before).
TR8 was dead short between all 3 pins, but did it die or was it killed?

A new BU508A was fitted, removed and refitted again with the ferite bead on the base this time and I checked around the PCB for any bad joints, a couple of legs looked rough on a cap (C12 between T3 and TR8) so I decided to re-solder them, upon applying heat from my iron, a right pong ensued. C12 was not well. So it looked as though TR8 had been killed.

So with a new TR8 and C12 I powered on. This time I got a standby light, pressing the "P" button beneath the CRT and up came a snowy raster.

In the absence of the correct Beolink remote control I had to tune a test card in by altering the RF channel output on my PM5515 pattern generator and the CRT looks like a good one.
Attached Thumbnails
Click image for larger version

Name:	B&O_1.jpg
Views:	127
Size:	71.2 KB
ID:	168982   Click image for larger version

Name:	B&O_2.jpg
Views:	122
Size:	122.8 KB
ID:	168983   Click image for larger version

Name:	B&O_3.jpg
Views:	117
Size:	52.0 KB
ID:	168984   Click image for larger version

Name:	B&O_4.jpg
Views:	136
Size:	97.5 KB
ID:	168985   Click image for larger version

Name:	B&O_5.jpg
Views:	126
Size:	43.1 KB
ID:	168986  


Mike C
Mikey66 is offline  
Old 11th Sep 2018, 10:09 pm   #2
Join Date: Dec 2007
Location: Haarlem, Netherlands
Posts: 3,189
Default Re: B&O 3163 mx3500

Time may tell whether some more electrolytics need replacing. Nice set and good job! Geometry and convergence still look spot on (B&O had their tubes selected from the production line).
Maarten is offline  
Closed Thread

Thread Tools

All times are GMT. The time now is 10:51 am.

All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at
Failure to heed this warning may result in death or serious injury to yourself and/or others.

Powered by vBulletin®
Copyright ©2000 - 2021, vBulletin Solutions, Inc.
Copyright ©2002 - 2021, Paul Stenning.