Hi to all,
Picked up one of these 10MHz, single beam CROs from my local DSE store last Tuesday - there were none on display and the staff seemed unaware of its existence. The unit comes in a carry box, well packed with IEC mains lead,
10:1 probe and small handbook written by DSE staff.Using a bench sine/ square generator and frequency counter when back at home, I found my unit met published accuracy specs - time base speeds being particularly accurate.
The *green* trace on the 75m dia tube face is particularly sharp and geometry is very good all over the (external) graticule. The vertical and horizontal positioning pots allow the pattern to be moved right off the screen without visible limiting - so the deflection amplifiers have adequate headroom.
The internal (Y) synch appears to function well as does the external and LINE synch inputs. There is an X-Y mode that works fine too. There is no "trace rotate " control, but two screws on the rear can be loosened to allow the tube and hence trace to be lined up with the graticule OK.
Now for the insides:
-----------------------
With the vinyl coated steel sleeve slid off, there is a nice surprise. This little CRO is *very* well made - reminiscent of the way Aussie firm BWD built their famous CROs.
There are no SMD, all parts are "garden variety" - ie TO92 pack transistors, TO220 regulators, a couple of fets and 3 bog standard ICs. There is one large PCB for the PSU, deflection and synch circuits while a smaller one at the front covers the vertical attenuator, input pre-amp and time base circuitry.
Both sides of these (single sided, through hole) PCBs are fully accessible for servicing !
A very neat, 20 VA, R-core transformer powers the CRO with a ferrite HF inverter supplying 1200 volt DC to the tube. All internal voltages remain regulated down to 200 volts AC input.
The 75mm tube is covered in a black, very snug fitting, full length MAGNETIC SHIELD !! This is practically unheard of in a low cost CRO and means the unit can be used, without annoying trace jitter, quite close to AC power transformers used by other items on the bench or the equipment under test.
The AC current draw was only 84mA rms ( 20 VA ) - so operation from a small 12volt / 240 volt inverter supply is possible.
One anomaly I found - the CRO comes fitted with a 0.75 amp AC fuse. The DSE handbook and the back label on the CRO both say this is the intended value - which is nonsense since it offers no protection for the 20 VA transformer. Best replace it with a 160 mA, slo-blo type.
Although not indicated anywhere, I expect the CRO was manufactured in China or just possibly Korea. One would have to remove the CRO tube to see where that was made.
My conclusion:
At a mere $ 128 inc GST and probe, this has got to be the biggest bargain in
*new* test gear you can buy in Australia........ Phil