UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Roband Varex 60-5 power supply

Techman · 19th May 2016, 1:28 am

Another of the £1 'bargains' from the recent 'silent key' sale here in the wilds of rural Lincolnshire. This is a real 'boat anchor' of a power pack and it does work but has one fault. I've read a couple of previous threads on this power supply and downloaded the service information from the link in one of these threads that covers the 'twin' version, but should be near enough the same, and I've read about the problem with the current limit control in one of these threads.

The current limit controls and circuitry seem to work perfectly on this unit, but the problem is with the voltage control. As long as the voltage control RV101B 'fine' outer ring is set fully anti-clockwise, the inner control RV101A can be used to set the voltage without problems. However, if the 'fine' control is moved more than three divisions from its end stop, the voltage will go straight up to 105 volts! This is a bit of a worry should I happen to forget NOT to touch the 'fine' adjustment, that this voltage increase can suddenly happen like this. I've not opened the power unit yet, but on listening to the control as it's rotated I can hear it making that familiar sound of a wire wound pot with a damaged section of track just in one place - probably caused by battery charging with the settings too low as warned about in the manual. I'm thinking that the best way forward would be to hard wire this 'pot' out of circuit so that it no longer 'adjusts' anything as there's little chance of replacing it or easily repairing it - any thoughts?

19th May 2016, 1:28 am	#1
Techman Dekatron Join Date: Nov 2009 Location: Lincolnshire, UK. Posts: 5,000	Roband Varex 60-5 power supply Another of the £1 'bargains' from the recent 'silent key' sale here in the wilds of rural Lincolnshire. This is a real 'boat anchor' of a power pack and it does work but has one fault. I've read a couple of previous threads on this power supply and downloaded the service information from the link in one of these threads that covers the 'twin' version, but should be near enough the same, and I've read about the problem with the current limit control in one of these threads. The current limit controls and circuitry seem to work perfectly on this unit, but the problem is with the voltage control. As long as the voltage control RV101B 'fine' outer ring is set fully anti-clockwise, the inner control RV101A can be used to set the voltage without problems. However, if the 'fine' control is moved more than three divisions from its end stop, the voltage will go straight up to 105 volts! This is a bit of a worry should I happen to forget NOT to touch the 'fine' adjustment, that this voltage increase can suddenly happen like this. I've not opened the power unit yet, but on listening to the control as it's rotated I can hear it making that familiar sound of a wire wound pot with a damaged section of track just in one place - probably caused by battery charging with the settings too low as warned about in the manual. I'm thinking that the best way forward would be to hard wire this 'pot' out of circuit so that it no longer 'adjusts' anything as there's little chance of replacing it or easily repairing it - any thoughts? Attached Thumbnails