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Old 16th Nov 2018, 8:56 pm   #1
TrevorG3VLF
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Default Heathkit OS1 scope voltages

I have a Heathkit OS1 scope with a sick mains transformer. I have the construction manual and circuit.
Does anyone have the HT and EHT voltages to aid in rewinding the transformer?
This is a future project, with luck it will eventually get to the top of the pile.
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Old 16th Nov 2018, 9:56 pm   #2
Bazz4CQJ
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Default Re: Heathkit OS1 scope voltages

Trevor, long ago (~1980) I had two of these (?) scopes taken from a skip.
Attached is a circuit diagram; I have a better copy, but it exceeds the file size limit. Do these look right? Somewhere, I may have a transformer.

B
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File Type: pdf Heathkitscope.pdf (98.2 KB, 29 views)
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Old 16th Nov 2018, 10:13 pm   #3
Ed_Dinning
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Default Re: Heathkit OS1 scope voltages

Hi Trevor, mail me when you get round to doing this and I'll see if I have a used /tested transformer that will do in my collection. Is there much space in the chassis for a larger transformer?


Ed
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Old 16th Nov 2018, 10:16 pm   #4
ronbryan
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Default Re: Heathkit OS1 scope voltages

That circuit is for a more sophisticated Heathkit scope. It's from an O-12, which was sold as a 'lab' scope as far as I remember.

Ron
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Old 17th Nov 2018, 5:28 pm   #5
ColinTheAmpMan1
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Default Re: Heathkit OS1 scope voltages

I have these two, which I think are the right scope. I'm afraid there are still no voltages shown.

Colin.
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Old 17th Nov 2018, 6:57 pm   #6
wd40addict
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Default Re: Heathkit OS1 scope voltages

Page 27 of the manual gives 235Vac on the rectifier anodes and -700Vdc on CRT pin 8 (depending on brightness). No Vac into the stick, but Ed may be able to estimate this!
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Old 17th Nov 2018, 8:07 pm   #7
Ed_Dinning
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Default Re: Heathkit OS1 scope voltages

Hi Gents, it is possibly a 250-0-250 for main Ht then a 350v overwind on one of the rect anode windings as the loading will only be low.

It would be possible to configure a voltage multiplier (tripler?) from one of the rect anodes.

Ed
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Old 17th Nov 2018, 9:04 pm   #8
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Default Re: Heathkit OS1 scope voltages

I once had a TQ D43 with the highest voltage winding of the transformer open circuit.I did exactly what Ed suggests and made up a multiplier (quintupler?) which worked perfectly. I had a willing customer who knew the score, and got a good working calibrated scope at a price he could afford. 35 years ago, I wonder if he still has it?
Les.
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Old 17th Nov 2018, 9:13 pm   #9
ColinTheAmpMan1
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Default Re: Heathkit OS1 scope voltages

Quote:
Originally Posted by wd40addict View Post
Page 27 of the manual gives 235Vac on the rectifier anodes and -700Vdc on CRT pin 8 (depending on brightness). No Vac into the stick, but Ed may be able to estimate this!
If you look at this page:
https://frank.pocnet.net/sheets/198/3/3AFP1.pdf
you will see that the maximum final anode voltage for the 3AFP1 crt is 1.0 kV. There is some more data on the crt, too. I hope it helps.
Colin.
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Old 18th Nov 2018, 1:07 am   #10
TrevorG3VLF
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Default Re: Heathkit OS1 scope voltages

Thanks for the information. I will put it to one side for a time and will rewind a simple battery charger as my first mains transformer I have wound coils for geetah pick ups, 30000 turns for a slave clock solenoid and a few hundred turns for a low tension ignition coil (1900 Mercedes engine).
The transformer has the flu as it is sweating so will not give correct voltages. I do not think that a couple of paracetamol will help. More investigation needed.
It is just an idea at the moment, I thought I might get rid of the primary taps, use a single 250V winding with a coule of diodes to make a bridge and use a separate winding doubled for the EHT, thus balancing the series capacitors. No taps should be easier to make.
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