This was given to me with the comment "It doesn't work; I think it's been dropped. Is it any good to you?" Not being able to resist a challenge, I said "Thank you very much!" - and the work began.
First inspection indicated that, yes, it had been dropped and since it is rather heavy, any such accident would - and indeed did have - consequences.
Apart from a distorted top lid (easily bent back into shape) and broken output terminals, the voltmeter and ammeter didn't work - but the unit did produce volts and amps. This is a rather old item from Zetagi and attempts to obtain the correct replacement meters were not successful. Hence, a replacement D-I-Y approach was required. The meter replacement results are not of the best quality I could have obtained, but are adequate for the job and, moreover, are in keeping with the grade of 'quality' of this item. 
To do this meter replacement, it was necessary to relocate the mains transformer further back in the case so that the meters would fit the front panel. Subsequent 'on-load' tests indicated that the main rectifier reservoir capacitors were past their best - so they were replaced: all eight of them, each 2200 uF @ 35-v. Finally, a general tidy-up of the wiring was done and a final 'soak test' was run.
Now this unit states "25 amp". Well, maybe: I found that the maximum current draw was about 20-amp. before the regulator gave up. And at that current, the heat-sinks on which series pass transistors are mounted got far too hot - seriously so. The output voltage was adjustable from 3 to 17-v.: this unit is clearly aimed to meet the needs of high-current 12-v. applications.
Piece-and-part of the repair was the need to produce a cct. diagram of the unit. This was traced out by eye-and-hand and is attached accordingly.
In conclusion, a useful item of test kit to meet those occasional requirements for a nominal, regulated 12-v. d.c. at seriously high currents; none of my existing PSUs meet that need.
[attachment=6222] [attachment=6223] [attachment=6224] [attachment=6225]
The white box (with the square meters) beneath the PSU is an adjustable dummy load.
This PSU now features in the Gallery.
Al. / Nov. 16, 2012 //
First inspection indicated that, yes, it had been dropped and since it is rather heavy, any such accident would - and indeed did have - consequences.
Apart from a distorted top lid (easily bent back into shape) and broken output terminals, the voltmeter and ammeter didn't work - but the unit did produce volts and amps. This is a rather old item from Zetagi and attempts to obtain the correct replacement meters were not successful. Hence, a replacement D-I-Y approach was required. The meter replacement results are not of the best quality I could have obtained, but are adequate for the job and, moreover, are in keeping with the grade of 'quality' of this item. To do this meter replacement, it was necessary to relocate the mains transformer further back in the case so that the meters would fit the front panel. Subsequent 'on-load' tests indicated that the main rectifier reservoir capacitors were past their best - so they were replaced: all eight of them, each 2200 uF @ 35-v. Finally, a general tidy-up of the wiring was done and a final 'soak test' was run.Now this unit states "25 amp". Well, maybe: I found that the maximum current draw was about 20-amp. before the regulator gave up. And at that current, the heat-sinks on which series pass transistors are mounted got far too hot - seriously so.
The output voltage was adjustable from 3 to 17-v.: this unit is clearly aimed to meet the needs of high-current 12-v. applications.Piece-and-part of the repair was the need to produce a cct. diagram of the unit. This was traced out by eye-and-hand and is attached accordingly.
In conclusion, a useful item of test kit to meet those occasional requirements for a nominal, regulated 12-v. d.c. at seriously high currents; none of my existing PSUs meet that need.
[attachment=6222] [attachment=6223] [attachment=6224] [attachment=6225]
The white box (with the square meters) beneath the PSU is an adjustable dummy load.
This PSU now features in the Gallery.
Al. / Nov. 16, 2012 //
