UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post

MickMcmichael · 15th Nov 2019, 12:22 pm

A few days have passed so I thought it about time I check out the 625 operation. I knew that the 625 tuner was very stiff to turn and would need a little fettling

Out came the tuner (easy) and strip and lubricate the cog etc and free off all the old grease. Quick and easy. Set system switch to 625, 405 to U and switch on.

Smoke and big sparks from under the IF board in the top right hand corner immediately as I switch on. Ooerr...

Remove system linkage from IF board (easy) and swing the board towards me. There was a little carbonisation between two pieces of parallel running print along the right hand edge of the board. These were shorting to the metal chassis due to the thin rubber insulation strip having deteriorated badly.

Cleaned print with fibre pen and dug out the carbonised bit until it was clean. I then grabbed a capstan belt out of a video recorder belt kit and used this as a replacement for the insulation on the chassis once cut to length. A little glue helped to keep it in position as I re-fitted the IF board into the chassis slots.

Switch on again and we have good but not perfect 625 operation.

The frame stage is still playing up a bit but I've still got a couple of old Dubiliers in there to sort out next time.

More soon.

15th Nov 2019, 12:22 pm	#9
MickMcmichael Pentode Join Date: Mar 2009 Location: Peterborough, Cambridgeshire, UK. Posts: 196	Re: Marconi 4610. Thorn 850. A few days have passed so I thought it about time I check out the 625 operation. I knew that the 625 tuner was very stiff to turn and would need a little fettling Out came the tuner (easy) and strip and lubricate the cog etc and free off all the old grease. Quick and easy. Set system switch to 625, 405 to U and switch on. Smoke and big sparks from under the IF board in the top right hand corner immediately as I switch on. Ooerr... Remove system linkage from IF board (easy) and swing the board towards me. There was a little carbonisation between two pieces of parallel running print along the right hand edge of the board. These were shorting to the metal chassis due to the thin rubber insulation strip having deteriorated badly. Cleaned print with fibre pen and dug out the carbonised bit until it was clean. I then grabbed a capstan belt out of a video recorder belt kit and used this as a replacement for the insulation on the chassis once cut to length. A little glue helped to keep it in position as I re-fitted the IF board into the chassis slots. Switch on again and we have good but not perfect 625 operation. The frame stage is still playing up a bit but I've still got a couple of old Dubiliers in there to sort out next time. More soon. Attached Thumbnails Last edited by MickMcmichael; 15th Nov 2019 at 12:29 pm.