Oh my wordee! A blast from the past ....
I am "working through" a mountain of equipment (test/professional audio & domestic) which was in our "hmmm, something's not right here" storeroom and today I pulled out this scope from "Tricky Dicky"
Make no mistake this is a general purpose analog oscilloscope for the "budget conscious" user and NOT in the same class as our HP, Tektronix equipment but even these days the old CRT based analog scopes are nice to have around and use for audio work in particular.
HISTORY:
Marketed in Australia through Dick Smith Electronics, they badged the oscilloscope as a Q1802. Original manufacturer was PINTEK of Taiwan and it is their model PS-200. Some say (not confirmed though) that this is actually a "cut down" a.k.a cheaper version of the HEATHKIT SO-4552 Oscilloscope.
Originally marketed as a "general purpose" scope and sold for around A$500 at the time, early 1990's
DICK SMITH ELECTRONICS - Oscilloscope
Model: Q1802
Original manufacturer: PINTEK
Country of origin: Taiwan
Technology: Semiconductor based analog
Display type: CRT Monochrome screen
Dual channel
Bandwidth: 20Mhz
AC input: 220V ~ 240V 50Hz or 110V ~ 115V (User selectable at the rear)
More complete technical information is available in one of the photographs
DIMENSIONS:
320mm wide x 130mm height x 400mm deep
WEIGHT:
7Kg (unpacked)
Quite a comfortable carrying weight although a bit cumbersome!
WHAT IS INCLUDED IN THIS ADVERTISEMENT?
DICK SMITH Q1802/PINTEK PS-200 Oscilloscope
IEC power lead to suit Australian standards
WHAT IS NOT INCLUDED?
NO test leads or probes of any kind
NO User or Service manual
If you cannot see what you are looking for in the equipment photograph, that means it is NOT included
COSMETIC CONDITION:
USED
Clean
Actually showing very little signs of use, with no significant scratching to the casing and absolutely NO DENTS!
Front CRT graticuled window is unmarked
ALL knobs and switch tops are present
NO damage to any of the front panel controls
BNC channel input sockets clean and undamaged
ALL labelling is unworn and easy to read
Rear panel is clean and very sparse, actually it only has the IEC input socket, into which is incorporated the 110/220V AC input selector plug
Rear feet are in very good condition and all are present!
Base feet are also in very good condition and all are present!
There is NO tilt arm underneath, I am not sure it even had one originally.
Carry handle (ALL plastic!) is undamaged, no cracks at all. Shows very little sign of being used. Side adjustment/locks for the carry handle are working fine.
Overall a very nice unit in great COSMETIC condition, now let's take a look inside ...
TESTING:
First thing BEFORE power ON is to observe, take a look around and see if anything is obvious. Once, long ago, I opened up some ancient equipment and found a well petrified mouse hanging from the HT rail! It always pays to check before powering up.
Easy to access the unit for servicing with 4x standard Philips head screws on each side and one on the top for the top cover and just two of the same screws to remove the bottom plate.
WOW! This looks like new inside, not even a cobweb!
Hmmmm, many of the chips are in IC sockets. That could be a source of issues or helpful to someone undertaking service.
Three separate PCB's, top side I see no obvious stress issues or damage of any kind. Underneath, again it LOOKED at first glance to be absolutely untouched and then I noticed that one of the transistors in the HV section has been "pulled" nada zero, 3 holes but no transistor (and it isn't lying around inside either!) The transistor has been professionally removed (nice and clean desoldering) and NO other tracks or components have been touched.
Please take a look at the photograph showing this missing transistor location (right inside the HV enclosure and next to the HV transformer)
So with this observation I am 100% sure that not all is going to be well with the scope...let's press on!
Removed the metal top cover of the HV section (2x screws - easy removal) revealing the missing transistor and surrounding components. Oh dear it is the dreaded Q950 (2SD880), this seems to be a fairly common issue with these scopes because I looked around online to see if others had experienced trouble around this area of the design and yes siree! quite a bit of discussion online about this transistor and possible failure causes.
Here are some links to those relevant discussion forums:
MOST of the surrounding components are not special but that transformer could create a headache, if in fact it turns out to have shorted turns.
None of the other components are showing any signs of stress at all, which I guess is a good thing. Perhaps the transistor "popped" its brains out, who knows? but hopefully it is not due to the transformer being at fault. NO efforts have been made by the previous person who looked at this (one of our techies probably) to remove that transformer, all soldering etc is untouched.
The HV transformer is marked as:
CVT023
YN05258
0608
At this point, here are some of the other components which could be of interest if using the scope as an "organ donor"
CRT: MEDIATECH Type 150BTB31F
FAIRCHILD 74ALS00 IC
FAIRCHILD 74ALS74 IC
HITACHI HA17741 Op Amp
MITSUBISHI 104011BP IC (I think this is just a 4011 CMOS gate chip)
4N35 Optocoupler
and a few others buried on the lower PCB which I cannot access without dismantling the whole unit!
The above are all in sockets, easy removal, but quite "ordinary" chips which is a good thing, nothing worse than trying to decode the markings on HP gear to figure out what the device replacement should be.
The CRT could be useful in other equipment though.
Although this will be a pretty fruitless endeavour, time to turn it ON! ....
NO Bangs!, NO Smoke!, NO Smells! NO Display (as expected)
All that happens when powered on is the Red LED turns ON and nothing more. I guess you can be sure at least the power switch and at least some parts of the power supply are running fine but I am not about to "dig deeper" so I have made no further tests, no voltage checks etc
I have a LOT of gear to work through and only a very limited time to spend on each so this is where my description will end ...
SUMMARY:
Obviously not working (no display) and there are strong indications of the reason (no transistor in the HV section is a pretty good reason!)
Either diagnose and service this scope to get it running again OR turn it into a "component farm" or "organ donor" to bring other similar model scopes back from the dead!
