Scope repair

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Re: Scope repair

Postby Harry Dalek » Sat Feb 18, 2023 4:43 pm

I just ended up mounting the second transformer getting some thing to fit nice with close enough voltages worth giving it a go once Steve has a look .
I checked the voltages with another Multimeter today and the readings pretty much match .
The 2 AC voltages i am a bit iffy over more so the isolated 31v Blanking and high positive 141v Ac .
I am getting 135V 6v off does it matter that much ? i am sure if your looking Steve you would say well it depends on how it go's on the DC side with load of the circuits ,i just know this transformer is 3 times the size of the old one hardly do any worse .
Being a touch under the AC readings voltage i am happier than if it were over what i am thinking is its safer but i know it has to work as well .
Now where i see the last problem being is the isolated 6.3 and 31 volts sharing the middle winding i only have 20v here with is own isolated but i touch low .
i was thinking of using the 12v for the 11.9v components test circuit but if i use the 12v 0 12v together i get 24 or 25 volts for the blanking its 22 to 65 from memory in the CRT PDF i could drop the (20 volt for component for 11.9v Ac ) be much easier in dc but here i can't see where it go's in the schematic i would have to visually look on the board. ..
Image of the mounted Transformers and the scope AC multi wiring to plugs just sitting on top ,all that works with the scope so far is the on and off panel switch mains to the 2 new transformers ,i can connect now the transformers secondary if i wanted to and or test via the sockets on the mounted PCB ,be easy to wire the oscilloscope in but i will wait till sensei Steve has a look .
And the original transformer it was not big at all !
Attachments
DSCN6971.JPG
DSCN6963.JPG
original scope transformer
Last edited by Harry Dalek on Sun Feb 19, 2023 9:06 am, edited 3 times in total.
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Harry Dalek
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Re: Scope repair

Postby Harry Dalek » Sat Feb 18, 2023 11:11 pm

My Dick smith 20 Mhz scope manual
I am having another look for a schematic and it looks like its a copy rebranded Pintek Oscilloscope PS-200
UPDATE
i think the Heatkit SO-4552 scope is the same also ,i found another scrap of schematic below but i found that my scope and the heatkit are the same and it does have a schematic in the manual ! found it on https://mods.dk/manual.php?brand=heath via a lot of searching on other forums giving clues to where to look .
SO-4552 Oscilloscope.pdf
The full schematic
(2.93 MiB) Downloaded 117 times
Attachments
dick_smith_cro_ps-205 (1).pdf
(2.12 MiB) Downloaded 120 times
s-l640.jpg
s-l640.jpg (41.49 KiB) Viewed 3198 times
Capture.PNG
Last edited by Harry Dalek on Sun Feb 19, 2023 9:09 am, edited 1 time in total.
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Harry Dalek
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Re: Scope repair

Postby Harry Dalek » Sun Feb 19, 2023 9:02 am

Having a look at where the to comp test gos from the AC 11.9 secondary its not an easy schematic to follow with it split up over pages ,looks like its using the 12v AC as is .
looks to go to (Resistance Voltage Divider) feeding it or not at the moment looks to me like it would not stop the scope working if i just concentrated on powering the scopes other supplies ?
Attachments
Screen 00014.bmp
Screen 00015.bmp
Screen 00015.bmp (268.73 KiB) Viewed 3189 times
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
User avatar
Harry Dalek
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Re: Scope repair

Postby Harry Dalek » Tue Feb 21, 2023 5:39 pm

I was waiting for Steve before i worked any more on it this but it looks all good and Steve may be off on a work job ?.
Temptation to find out one way or another i hooked up the heater all good and hooked up the low power and 130v AC to the high positive supply the scope came to life again.

DSCN6990.JPG

I was at first using the 12v 0 12V ac supply and only getting 13v DC the trace was a bit of a saw tooth sinewave cross looking to it, i was at first thinking Oh no magnetic field problems but after checking the voltages i could see this AC supply was not good enough swapped to the 15v 0 15v and that worked gave the 18v as on the schematic and 145v DC 12v dc and 5 v dc .
I left the component test supply not connected yet .
Now for the Bad news i was thinking the scope was fine when the last transformer went but i seem to have a problem with both vertical position controls not working and signal display waveform in is distorted both channels so something happened .
DSCN6983.JPG

Today also looking at the Schematic and looking at the circuits i noticed changes that were made to my scope replacing the opamps with regulators 7812 7912 7805 but not an easy schematic to follow rest looks a copy but some updating happened in the Dick smith version .
I hope its just a IC thats gone most look pretty common 7474 4011's arrr more studying
Last edited by Harry Dalek on Fri Feb 24, 2023 5:24 pm, edited 1 time in total.
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Harry Dalek
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Posts: 5363
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Location: Australia

Re: Scope repair

Postby Harry Dalek » Fri Feb 24, 2023 8:53 am

I found that this scope Dse Q-1802 oscilloscope has also been rebranded to a Toptronic T200 and digitor Q-1802 .
Looking at the circuit boards i also found changes to the old heathkit version in the timing circuits for the horizontal trace .
So looking for a more updated pintek PS-200 oscilloscope schematic ,some one on another forum managed to get one from Pintek a few years ago and was offering a copy to any one but my luck has not been on that forum since
Update found the pinteck schematic
PS 20-60mhz (1).pdf
(1.18 MiB) Downloaded 115 times

I will have a look how close it is to mine
Attachments
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa.jpg
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Harry Dalek
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Re: Scope repair

Postby Steve Anderson » Sat Feb 25, 2023 3:43 pm

Harry, can't really help at the moment, I'm away from home in Vientienne, Laos, I'm gonna be here for a few more days. Been able (just about) to get this internet connection which isn't easy here. But only while I'm in the capital, once rural, (the site), forget it.

Steve A.
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Steve Anderson
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Re: Scope repair

Postby Harry Dalek » Sat Feb 25, 2023 9:16 pm

Steve Anderson wrote:Harry, can't really help at the moment, I'm away from home in Vientienne, Laos, I'm gonna be here for a few more days. Been able (just about) to get this internet connection which isn't easy here. But only while I'm in the capital, once rural, (the site), forget it.

Steve A.


I was thinking you were working no problems ,this one is a hard one for me the vertical position circuit in the schematic is confusing to me could be so many things around the controls or after ,problems seem to be just in the vertical side both channels .
I saw some one had a problem with the pintek 200 but gives away the blanking voltage shown below .

I recently measure the power transformer output of the pintek im servicing. (mine only displays a dot, im not able to mess around with controls because something is making a high POP sound after 5 seconds i turn the unit on, sounds like something is arcing inside, no smell of any burned component and no visible burned one)

the voltages are:
primary on 220v
secondaries:
12v
15.5 - 0 - 15.5
147.5
30.8 - 0 - 6.2.

note: my unit uses another type of voltage regulation(transistors, not LM78XX) and the pcb is coded: PWB 064V.


I am starting to suspect the HV negative might of been the cause of the vertical failure its not some thing i have heard but noticed the wire was very close to the other wiring and is very under pretected for something carrying around 2kv i think i will put another plastic jacket around it and keep other wiring away .
MY high positive seems fine working on 130v ac .
After doing some research on this scopes circuits it's been used in so many rebranded scopes.
have some other bits
This fellow below similar vertical problems but he's is a 60mhz scope

youtu.be/E281JIRxb_w

youtu.be/J47J3YgVMHo
Attachments
PWB-044V-E-1.pdf
(1.84 MiB) Downloaded 104 times
PWB-044V-E-2.pdf
(1.84 MiB) Downloaded 107 times
PWB-045H-F.pdf
(1.55 MiB) Downloaded 109 times
schematicsreduced.pdf
(4.1 MiB) Downloaded 131 times
PS-605 Power Supply-1.pdf
(1.26 MiB) Downloaded 110 times
PS-605 vertical-1.pdf
(1.23 MiB) Downloaded 114 times
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
User avatar
Harry Dalek
"Fester! Don't do that to 'Thing'"
 
Posts: 5363
Joined: Fri Sep 26, 2008 4:58 pm
Location: Australia

Re: Scope repair

Postby Harry Dalek » Thu Mar 16, 2023 5:14 pm

This is still on going when i have time this is going to take a while to track down the problem in the vertical section as it could be any where along the chain from input middle to output or more than one problem .
I have to really pull the board out or take the top board PWB-045 H-F out to view the the middle board schematic below ,since i have a problem in the signal going in i suspect The ic's 3F 351N opamps are bad or in the chain perhaps The transistor array CA 3086 ,i don't have spares to check
lf351-955012.pdf
(603.62 KiB) Downloaded 108 times

schematicsreduced (1)-01.png


Next problem is the the position controls as i recall these are plugged into the bottom board PWB-044v-D
schematicsreduced (1)-02.png

PWB-044V-E-2 (1).pdf
(1.84 MiB) Downloaded 102 times


The scope does not have to many IC's that are hard to get but i would have to order the 351N's or the transistor array if its either of them any case still need to check voltages on the board when i can get to it ...
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
User avatar
Harry Dalek
"Fester! Don't do that to 'Thing'"
 
Posts: 5363
Joined: Fri Sep 26, 2008 4:58 pm
Location: Australia

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